September 9, 2019
Volume 2019, Dated: 9 September 2019
[Initiated by Prof. Dr. K. Lakshmi Narayana]
In Memory of
Late Professor Kotcherlakota Rangadhama Rao
D.Sc. (Madras).a D.Sc. (London).
(Birth on 9 September 1899 Early Morning, Berhampur
Demise on 20 June 1972 at 9h09m at Visakhapatnam),
at his residence, Narasimha Ashram, Official Colony,
Maharanipeta. P. O., Visakhapatnam 530002.
[Mrs. Peramma Rangadhama Rao demise on 31 Dec 1971 around 10 AM.]
TRUWIZ-120a
Q1.MNRAS000,1–15:2017: A numerical twist on the observational spin parameter, λR: K.E. Harborne, C. Power, A.S.G. Robotham, L. Cortese, and D.S. Taranu: (Posted on 15 Nov 2018): ABSTRACT: A primary goal of integral field spectroscopic (IFS) surveys is to provide a statistical census of galaxies classified by their internal kinematics. As a result, the observational spin parameter, λR, has become one of the most popular methods of quantifying the relative importance of velocity dispersion and rotation in supporting a galaxy's inner structure. The goal of this paper is to examine the relationship between the observationally deduced λR and one of the most commonly used theoretical spin parameters in the literature, the Bullock et al. (2001) λ′. Using a set of N-body realizations of galaxies from which we construct mock IFS observations, we measure λR as an observer would, incorporate the effects of beam smearing and seeing conditions. Assuming parameters typical of current IFS surveys, we confirm that there are strong positive correlations between λR and measurement radius, and strong negative correlations between λR and size of the PSF, for late-type galaxies; these biases can be reduced using a recently proposed empirical correction. Once observational biases are corrected for, we find that λR provides a good approximation to ∼√3/2 λ′ (Reff), where λ′ is evaluated for the galactic stellar component within 1 Reff. DETAILS: Our aim, as extra-galactic astronomers, is to understand the formation and evolutionary mechanisms that lead to the variety of galaxies that we observe across the Universe. An observational spin parameter, λR, and ellipticity, ε. λR utilises the radial distribution of kinematics provided by integral field spectroscopy (IFS), defined by, λR ≡ <R|V|>/ <R√(V2 + σ2 ), where R is the circularised radial position, V is the LOS velocity, and σ is the LOS velocity dispersion taken as luminosity-weighted averages denoted by the angular brackets. λ′, given by, λ′ = J /√2 M Vc R, where J, M, and Vc are the angular momentum, mass, and circular velocity all measured within radius R. This form is particularly attractive because it depends only on material within R and can be calculated for an individual component, k, λ′ k = jk / √2 Vc R, where the angular momentum is replaced with the specific angular momentum, jk = Jk/Mk. CONCLUSION: We conclude that this correction should be applied to observational data prior to further comparisons in order to significantly reduce the observational limitations. We have also discussed that, following this correction, the observed λR may be compared to the theoretical definition of the Bullock spin parameter, λ′. While often it is assumed that the “true” spin parameter is the one measured in perfect seeing conditions, and this empirical correction has been designed to assume as much, we show that λR is offset from the commonly used theoretical -----------------------parameter,,
a. Bullock. b. Circular. c. Relative. d. Extra-galactic.
Q2. arXiv:1812.02754[astro-ph.EP]6Dec.2018: Dynamical origin of S-type planets in close binary stars: Giacomo Fragione: (Submitted on 6 Dec 2018) ABSTRACT: Understanding the origin of planets that have formed in binary stars is fundamental to constrain theories of binary and planet formation. The planet occurrence rate in binaries with a separation ≲50 AU is only ∼ one third that of wider binaries or single stars. This may indicate that a close companion has a ruinous influence on planet formation because it can truncate the protoplanetary disc and pump up planetesimals eccentricity and collision probability. Nevertheless, observations have revealed a few of these systems, which challenge current planet formation theories. Dynamical interactions can deliver planets into S-type orbits. In this paper, we consider as a possible scenario for forming S-type planets in close binaries the single star-binary star interactions that commonly take place in star clusters. We find that the final fraction and orbital properties of S-type planets in close binaries are mainly determined by the mass ratio of the stars involved in the close encounter, and the initial binary and planet semi-major axes. Present and upcoming missions, as TESS, PLATO and CHEOPS may shed new light on the origin of S-type planets in close binaries. DETAILS: one of the most generic environments to investigate planet formation and dynamics is that of binary and multiple systems. However, out of ∼ 3700 confirmed planets only about hundred exoplanets have been found in multiple stellar systems. CONCLUSIONS: Understanding the origin of planets that have formed in binary stars is fundamental to constrain theories of binary and planet formation. If S-type systems in close binaries cannot be formed in-situ, they should be mainly the result of planet trapping either as a consequence of the evolution of the stars of a binary or as a consequence of encounters, both of which ought to be rare. Both the rarity of these events and the difficulty in forming these planets in-situ seem to agree with the fact that most of the campaigns for detecting these planets have either produced no results or the number of their discovered planets did not exceed one or two. The recently launched TESS, along with future data by the James Webb Telescope and upcoming exoplanets missions like PLATO and CHEOPS, may shed new light on the origin of S-type planets in------- binaries.
a. Distant b. Averaged c. Conjoined d. Close
Q3. arXiv:1812.03177 [cond-mat.mes-hall]: 7 Dec. 2018: Adiabatic two-qubit gates in capacitively coupled quantum dot hybrid qubits: Adam Frees, Sebastian Mehl, John King Gamble, Mark Friesen, S. N. Coppersmith: (Submitted on 7 Dec 2018): ABSTRACT: The ability to tune qubits to flat points in their energy dispersions ("sweet spots") is an important tool for mitigating the effects of charge noise and dephasing in solid-state devices. However, the number of derivatives that must be simultaneously set to zero grows exponentially with the number of coupled qubits, making the task untenable for as few as two qubits. This is a particular problem for adiabatic gates, due to their slower speeds. Here, we propose an adiabatic two-qubit gate for quantum dot hybrid qubits, based on the tunable, electrostatic coupling between distinct charge configurations. We confirm the absence of a conventional sweet spot, but show that controlled-Z (CZ) gates can nonetheless be optimized to have fidelities of ∼99% for a typical level of quasistatic charge noise (σε≃1 μeV). We then develop the concept of a dynamical sweet spot (DSS), for which the time-averaged energy derivatives are set to zero, and identify a simple pulse sequence that achieves an approximate DSS for a CZ gate, with a 5× improvement in the fidelity. We observe that the results depend on the number of tunable parameters in the pulse sequence, and speculate that a more elaborate sequence could potentially attain a true DSS. CONCLUSIONS: Discussion — We have proposed a scheme for entangling capacitively coupled quantum-dot hybrid qubits by applying adiabatic pulse sequences to detuning parameters. We have optimized the sequences in the presence of quasistatic charge noise and computed the resulting process fidelities for a controlled-Z gate, obtaining fidelities approaching 99% for typical noise levels. Further improvements are obtained by simultaneously applying pulse sequences to the tunnel couplings. These results are explained by invoking the concept of a dynamical sweet spot (DSS), for which the splittings between the two-qubit energy levels are insensitive to fluctuations of the detuning parameters when averaged over the whole pulse sequence. Our analysis shows that a true DSS cannot be achieved using a simple pulse,
a. Excitations b. algorithms c. Sequences. d. Repetitions
Q4.arXiv:1812.03269: [gr-qc]: Curved Space, curved Time, and curved Space-Time in Schwarzschild geodetic geometry. Rafael T. Eufrasio, Nicholas A. Mecholsky, Lorenzo Resca: (Submitted on 8 Dec 2018): ABSTRACT: We investigate geodesic orbits and manifolds for metrics associated with Schwarzschild geometry, considering space and time curvatures separately. For `a-temporal' space, we solve a central geodesic orbit equation in terms of elliptic integrals. The intrinsic geometry of a two-sided equatorial plane corresponds to that of a full Flamm's paraboloid. Two kinds of geodesics emerge. Both kinds may or may not encircle the hole region any number of times, crossing themselves correspondingly. Regular geodesics reach a periastron greater than the rS Schwarzschild radius, thus remaining confined to a half of Flamm's paraboloid. Singular or s-geodesics tangentially reach the rS circle. These s-geodesics must then be regarded as funneling through the `belt' of the full Flamm's paraboloid. Infinitely many geodesics can possibly be drawn between any two points, but they must be of specific regular or singular types. A precise classification can be made in terms of impact parameters. Geodesic structure and completeness is conveyed by computer-generated figures depicting either Schwarzschild equatorial plane or Flamm's paraboloid. For the `curved-time' metric, devoid of any spatial curvature, geodesic orbits have the same apsides as in Schwarzschild space-time. We focus on null geodesics in particular. For the limit of light grazing the sun, asymptotic `spatial bending' and `time bending' become essentially equal, adding up to the total light deflection of 1.75 arc-seconds predicted by general relativity. However, for a much closer approach of the periastron to rS, `time bending' largely exceeds `spatial bending' of light, while their sum remains substantially below that of Schwarzschild space-time. DETAILS: For the ‘curved-time’ metric of ds2 =gµνdxµdxν =−(1− rS/r)*(cdt)2 + (dr)2+ r2(dθ)2 + r2 sin2 θ(dφ)2. Eq. (38), devoid of any spatial curvature, geodesic orbits have the same apsides as in Schwarzschild space-time. In particular, apsides of null geodesics obey a cubic αp3 = p−1, Eq. (41) that we solve. For the parameters and limitations of light grazing the sun, asymptotic ‘spatial bending’ and ‘time-bending’ become essentially equal, adding up to the total inward light deflection of 1.75 arc-seconds predicted by GR. However, for a much closer approach of rp to rS, ‘time-bending’ largely exceeds ‘spatial bending’ of light, while their sum remains substantially below that of Schwarzschild space-time.
a. Space b. Space-Time c. Time d. Radius.
Q5.arXiv:1812:03367:[physics.class-ph]: Irreducible matrix resolution of the elasticity tensor for symmetry systems: Yakov Ltin: (Submitted on 8 Dec 2018): ABSTRACT: December 11, 2018, file ElastMatrix1.tex: In linear elasticity, a fourth order elasticity (stiffness) tensor of 21 independent components completely describes deformation properties of a material. Due to Voigt, this tensor is conventionally represented by a 6×6 symmetric matrix. This classical matrix representation does not conform to the irreducible decomposition of the elasticity tensor. In this paper, we construct two alternative matrix representations. The 3×7 matrix representation is in with the permutation transformations of indices and with the general linear transformation of the basis. An additional representation of the elasticity tensor by three 3×3 matrices is suitable for describing the irreducible decomposition under the rotation transformations. We present the elasticity tensor of all crystal systems in these compact matrix forms and construct the hierarchy diagrams based on this representation. Conclusion: In this paper, we presented matrix representations of the elasticity tensor that confirm with its irreducible decompositions. In particular, (3×7) matrix corresponds to GL(3) decomposition of the elasticity tensor into Cauchy and non-Cauchy parts. When the traces of the elasticity Irreducible matrix resolution of the elasticity tensor 29 tensor are applied, an additional SO(3) irreducible decomposition emerges. We describe this decomposition with three (3×3) matrices. Two of these matrices are symmetric and one is of a general form. Since the symmetric matrices represent two second-order tensors, their traces are extracted in an invariant form and generate two linear invariants of the elasticity tensor. We apply the irreducible matrix decomposition to all symmetry classes and decompose correspondingly their elasticity tensors. This resolution of the symmetry classes yields a natural scheme of the hierarchy and inclusion of the symmetry
a. Space b. Space-Time c. Time d. Radius.
Q5.arXiv:1812:03367:[physics.class-ph]: Irreducible matrix resolution of the elasticity tensor for symmetry systems: Yakov Ltin: (Submitted on 8 Dec 2018): ABSTRACT: December 11, 2018, file ElastMatrix1.tex: In linear elasticity, a fourth order elasticity (stiffness) tensor of 21 independent components completely describes deformation properties of a material. Due to Voigt, this tensor is conventionally represented by a 6×6 symmetric matrix. This classical matrix representation does not conform to the irreducible decomposition of the elasticity tensor. In this paper, we construct two alternative matrix representations. The 3×7 matrix representation is in with the permutation transformations of indices and with the general linear transformation of the basis. An additional representation of the elasticity tensor by three 3×3 matrices is suitable for describing the irreducible decomposition under the rotation transformations. We present the elasticity tensor of all crystal systems in these compact matrix forms and construct the hierarchy diagrams based on this representation. Conclusion: In this paper, we presented matrix representations of the elasticity tensor that confirm with its irreducible decompositions. In particular, (3×7) matrix corresponds to GL(3) decomposition of the elasticity tensor into Cauchy and non-Cauchy parts. When the traces of the elasticity Irreducible matrix resolution of the elasticity tensor 29 tensor are applied, an additional SO(3) irreducible decomposition emerges. We describe this decomposition with three (3×3) matrices. Two of these matrices are symmetric and one is of a general form. Since the symmetric matrices represent two second-order tensors, their traces are extracted in an invariant form and generate two linear invariants of the elasticity tensor. We apply the irreducible matrix decomposition to all symmetry classes and decompose correspondingly their elasticity tensors. This resolution of the symmetry classes yields a natural scheme of the hierarchy and inclusion of the symmetry
a. Classes b. Groups c. Tensors d. Sets
Q6. arXiv:11812.03335 [astro-ph.GA: 8 Dec. 2018: Nearby void dwarf galaxies: recent results, the ongoing project, and prospects. S.A. Pustilnik, D.L. Makarov, A.L.Tepliakova: (Submitted on 8 Dec 2018): ABSTRACT: Properties of dwarf galaxies formed and evolved in the lowest density environment remain largely unexplored and poorly understood. Especially this concerns the low-mass end (M_bar < 10^9 Mo). We overview the results of a systematic study of a hundred void dwarfs from the nearby Lynx-Cancer void. We describe the ongoing project aiming to form Nearby Void galaxy sample (R < 25 Mpc) over the whole sky. 1354 objects with distances less than 25 Mpc fall within 25 voids delineated by 460 luminous galaxies/groups. The void major sizes range from 13 to 37 Mpc. 1088 of 1354 void galaxies reside deeply in voids, having distances to the nearest luminous neighbor of 2-11 Mpc. 195 nearest void galaxies reside in the Local Volume. We summarize the main statistical properties of the new sample and outline the prospects of the study of both, the void dwarf properties and the fine structure of voids. Summary and prospects The absolute majority of the Nearby Void dwarfs are irregular galaxies and late-type spirals. About 30 blue gas-rich dwarfs are candidates to VYGs. About 7% of the void sample are of early types: dE/E-S0 galaxies with a wide range of MB. Most of them are well isolated and thus can represent an unusual sub-type of field/void early-type galaxies. The new large sample of 1354 galaxies residing in the Nearby Voids opens the prospects of systematical studies of galaxy formation and evolution as well as of the properties of voids themselves. These include the following directions: 1) search for and study of the lowest mass void dwarfs, including candidates to the so-called Very Young Galaxies; 2) study the origin and evolution of early-type galaxies in voids; 3) search for appearance of cold accretion as a driving mechanism of galaxy evolution; 4) study of void small-scale structure, in particular as a probe of the predicted effect of voids as ’time machine and cosmic microscope’ (Aragon-Calvo & Szalay (2013)) and of the possible role of Warm Dark Matter in its
a. feasibility b. evolution c. formation d. sustenance
Q7. arXiv.1812.03622[astro-ph.HE]: 9 Dec. 2018: Vela as the Source of Galactic Cosmic Rays above 100 TeV. M.Bouyahiaoui, M.Kachelriess, D.V.Semkkoz: (Submitted on 9 Dec 2018); ABSTRACT: We model the contribution of the nearest young supernova remnant Vela to the local cosmic ray flux taking into account both the influence of the Local Superbubble and the effect of anisotropic diffusion. The dominant contribution of this source in the energy region around the cosmic ray knee can naturally explain the observed fluxes of individual groups of nuclei and their total flux. Adding the CR flux from a 2-3 Myr old local CR source suggested earlier, the CR spectra in the whole energy range between 200 GeV and the transition to extragalactic CRs are described well by the combined fluxes from these two local Galactic sources. Conclusions: In the standard diffusion picture it is assumed that Galactic CRs form a smooth, stationary “sea” around the Galactic disk. Evidence for this assumption comes from γ-ray observations, which indicate a rather small variation of the parent CR populations below ≈ 100GeV throughout the Galaxy outside of several kpc from the Galactic center [50]. Going to higher energies, CRs escape faster and thus the number of CR sources contributing to the local flux diminishes. Finally, we stress that, while including the effect of the Local Superbubble is an important improvement, the uncertainties connected to the strength and shape of the magnetic field in the bubble are large. In a future study, we plan therefore to study in depth the dependence of the spectrum and amplitude of the CR flux from Vela received on Earth on the parameters and the geometry of the Local Superbubble. Another important question to be addressed is how strong the dipole anisotropy from Vela will be decreased since the CR flux is effectively emitted not by a point source but the bubble wall. Last but not least, we note that the suggestion from a reference, that the Galactic soft neutrino component in the IceCube data is produced by CRs interacting in the wall of a superbubble fits well in the,
a. Scenario b. Picture c. Description d. Format.
Q8. arXiv:1812.03101 [astro-ph.SR]: 7 Dec. 2018: Impact of general differential rotation on gravity waves in rapidly rotating stars. Vincent Prat, Stéphane Mathis, Kyle Augustson, François Lignières, Jérôme Ballot, Lucie Alvan, Allan Sacha Brun. (Submitted on 7 Dec 2018). ABSTRACT: Differential rotation plays a key role in stellar evolution by triggering hydrodynamical instabilities and large-scale motions that induce transport of chemicals and angular momentum and by modifying the propagation and the frequency spectrum of gravito-inertial waves. It is thus crucial to investigate its effect on the propagation of gravity waves to build reliable seismic diagnostic tools, especially for fast rotating stars, where perturbative treatments of rotation fail. Generalising a previous work done in the case of uniform rotation, we derived a local dispersion relation for gravity waves in a differentially rotating star, taking the full effect of rotation (both Coriolis and centrifugal accelerations) into account. Then we modelled the propagation of axisymmetric waves as the propagation of rays. This allowed us to efficiently probe the properties of the waves in various regimes of differential rotation. DETAILS: Internal gravity waves are a unique way to probe stellar interiors for intermediate-mass and massive stars. Indeed, they provide us with constraints on mixing and rotation thanks to frequencies of gravity modes. CONCLUSIONS: We presented here axisymmetric waves. The dynamics of those waves still is to be explored, and this is a crucial step towards a description of the transport of angular momentum by gravito-inertial waves based on the ray theory since the transport arises from the different damping of prograde and retrograde
a. modes b. waves c. steps. d. rotations.
Q9. Mathematical Sciences Page 86 ABSTRACTS. On 5 January, 2019, Lovely Professional University, Jalandhar, CYCLIC AND V4 KLEIN GROUP ANALYSIS TO DESCRIBE VARIED MASS TERMS: Professor Dr. Kotcherlakota. L. N. trusciencetrutechnology@blogspot.com, 17-11-10, Narasimha Ashram, Maharanipeta.P.O. Visakhapatnam-530002.AP. Mobile No. 09491902867: ABSTRACT: The fourth order groups, the Cyclic, and the V4 Klein groups have been analyzed to obtain the mass-dependent Eigenvalues. The Cyclic group reveals both the real and imaginary Eigenvalues. The V4 Klein group, on the other hand, presents only real Eigenvalues. Both the positive and anti-positive mass terms are used adopting that the antiparticles have negative masses, like the electron-positron formulation. The different sets of mass values, adopting that the mass m2=-m1 positive masses and m4=-m3 for the anti-positive masses are adopted. The mass values m1 and m3 were varied from 0.1, 0.3, 0.4, 0.5, 0.6, 0.7, 0.9 and the respective Eigenvalues
a. evaluated b. realized c. obtained d. sought
Q10. Physical Sciences, Ph.72, ABSTRACTS: on 6 January, 2019: Lovely Professional University, Jalandhar, DIVERSE MANIFESTATION OF EARTH: Professor Dr. Kotcherlakota Lakshmi Narayana, trusciencetrutechnology@blogspot.com, 17-11-10, Narasimha Ashram, Official Colony, Maharanipeta.P.O, Visakhapatnam-530002. ABSTRACT: The present model envisages that graviton manifests itself, in diverse forms to intermingle with the Earthly dynamical system. On the surface, it devises itself as varied massive graviton of innumerable diversity and reforms itself as unimaginable complex quanta. But deep interior it breaks up into photons of unbelievable particulate matter of interior Earth. Present article expects the neutrino to catalyze the interaction of salt water with the graviton, producing new photons. The four parts of the Earth are Core, Mantle, Outer Core, and Inner Core. I expect all these four parts have distinct graviton mass and the new photons of extraordinary properties. The novel operator keeps the two photons γµ, γν bound in their interaction, and mµν with graviton. My model envisages newer photons of differing mass, transforms into electric and magnetic fields. How this happens is just a mystery and my model guarantees the unique transformation, hither too never thought by conventional
a. chemists b physicists c. mathematicians d. scientists
Q11. arXiv:1812.09472 [astro-ph.CO]: Big bang nucleosynthesis in a weakly non-ideal plasma, Dukjae Jang, Youngshin Kwon, Kyujin Kwak, Myung-Ki Cheoun, (Submitted on 22 Dec 2018): ABSTRACT: We propose a correction of standard big bang nucleosynthesis (BBN) scenario to resolve the primordial lithium problem by considering a possibility that the primordial plasma can deviate from the ideal state. In the standard BBN, the primordial plasma is assumed to be ideal, particles and photons satisfying the Maxwell-Boltzmann and Planck distribution, respectively. We suggest that this assumption of the primordial plasma being ideal might oversimplify the early universe and cause the lithium problem. We find that deviation of photon distribution from the Planck distribution, which is parameterized with the help of Tsallis statistics, can resolve the primordial lithium problem when the particle distributions of the primordial plasma still follow the Maxwell- Boltzmann distribution. We discuss how the primordial plasma can be weakly non-ideal in this specific fashion and its effects on the cosmic evolution. DETAILS: Big bang nucleosynthesis (BBN) is one of the most convincing evidence for the hot big bang cosmology. The precise measurement of the cosmic microwave background (CMB) and the accordingly determined value of the baryon-to-photon ratio, η = (6.094 ± 0.063) × 10^−10, imply that there is no free parameter left in the standard model of BBN (SBBN), which describes the formation of the lightest nuclides, such as D, 3He, 4He, and 7Li. SUMMARY: the present work proposes a suitable correction of plasma properties to the standard BBN scenario. Perceiving that the BBN plasma could not be perfectly ideal at T . 108 K, we considered the BBN plasma to be weakly non-ideal at T ≤ Ttr and used the distorted photon distribution in order to parametrize the non-ideality that causes the deviation of a blackbody spectrum of electromagnetic field in a plasma. With this correction, the calculated primordial abundances of the light elements are in excellent agreement with the recent observational data up to 7Li as shown in TableI. There are two main contributions of the distortion of photon distribution to the final abundances. The photodisintegration processes of light elements are enhanced, which plays a crucial role in reducing the primordial 7Li abundance. The change in photon energy density, on the other hand, makes the freeze-out time of light elements earlier so that the deuterium abundance is improved. It is advantageous that the physical idea behind our calculation is based just on the fundamentals of plasma physics, which will be discussed in more details in the future
a. Studies b. expectations c. thoughts d. decision
a. Studies b. expectations c. thoughts d. decision
Q12. arXiv:1812.09473 [astro-ph.HE]: Summing up Ultra-High-Energy Cosmic Rays from Radio Galaxies. Björn Eichmann: (Submitted on 22 Dec 2018): ABSTRACT: Radio galaxies are intensively discussed as the sources of cosmic rays observed above about 3 EeV, called ultra-high-energy cosmic rays (UHECRs). Here, the key issues from a recent investigation are summed up, where the individual characteristics of radio galaxies, as well as the impact by the extragalactic magnetic-field structures up to a distance of 120 Mpc has been taken into account. It is shown that the average contribution of radio galaxies taken over a very large volume cannot explain the observed features of UHECRs measured at Earth. However, we obtain excellent agreement with the spectrum, composition, and arrival-direction distribution of UHECRs measured by the Pierre Auger Observatory, if we assume that most UHECRs observed arise from only two sources: The ultra-luminous radio galaxy Cygnus A, providing a mostly light composition of nuclear species dominating up to about 60 EeV, and the nearest radio galaxy Centaurus A, providing a heavy composition dominating above 60 EeV. Here we have to assume that extragalactic magnetic fields out to 250 Mpc, which we did not include in the simulation, are able to isotropize the UHECR events at about 8 EeV arriving from Cygnus A. DETAILS: Can the origin of those extremely energetic particles be explained by radio galaxies? CONCLUSIONS: the dominance of a few single sources, whereof Centaurus A is only visible by Auger and Cygnus A is predominantly visible by TA, indicates the need for future investigations that include the impact of the GMF as well as the geometrical exposure of the experiments on the UHECRs from these sources. Further, the influence of the EGMF on the energy spectrum and composition of Cygnus A needs to be taken into account and a possible average contribution by the bulk of radio galaxies between the ankle and the second knee needs to be
Q14. arXiv:1812.09669 [gr-qc]: Pauli-type coupling between spinors and curved spacetime. J. Struckmeier, D. Vasak, A. Redelbach, P. Liebrich, H. Stöcker. (Submitted on 23 Dec 2018): ABSTRACT: On the basis of the regularized Dirac Lagrangian, we derive the Pauli interaction term of the subsequent field equation from the minimal coupling of the spinor ψ to an external electromagnetic field Aμ. An analogous coupling term emerges from the spinor's coupling to the spinor connection ωμ(x) in curved spacetime. In the ensuing field equation for the spinor, one thereby encounters an additional effective mass term, which is associated with a particular coupling constant M.This modifies the description of the dynamics of spinors in a gravitational field. For neutrinos, this could explain measurements indicating that all flavors of neutrinos apparently exhibit small but non-zero rest masses. Summary: Ultimately, any new contribution to neutrino masses from the Pauli-type coupling will have to be confronted with precision neutrino measurements. In this context, measurements of velocities of neutrinos within media of different curvatures would be particularly valuable. Measurements from OPERA and MINOS can also constrain such a new contribution. Also, the constraints coming from neutrino magnetic dipole moments will constrain contributions from this Pauli-type coupling and might favor large values of the unknown mass scale M for
a. studied b. researched c. investigated d. approximated
Q14. arXiv:1812.09669 [gr-qc]: Pauli-type coupling between spinors and curved spacetime. J. Struckmeier, D. Vasak, A. Redelbach, P. Liebrich, H. Stöcker. (Submitted on 23 Dec 2018): ABSTRACT: On the basis of the regularized Dirac Lagrangian, we derive the Pauli interaction term of the subsequent field equation from the minimal coupling of the spinor ψ to an external electromagnetic field Aμ. An analogous coupling term emerges from the spinor's coupling to the spinor connection ωμ(x) in curved spacetime. In the ensuing field equation for the spinor, one thereby encounters an additional effective mass term, which is associated with a particular coupling constant M.This modifies the description of the dynamics of spinors in a gravitational field. For neutrinos, this could explain measurements indicating that all flavors of neutrinos apparently exhibit small but non-zero rest masses. Summary: Ultimately, any new contribution to neutrino masses from the Pauli-type coupling will have to be confronted with precision neutrino measurements. In this context, measurements of velocities of neutrinos within media of different curvatures would be particularly valuable. Measurements from OPERA and MINOS can also constrain such a new contribution. Also, the constraints coming from neutrino magnetic dipole moments will constrain contributions from this Pauli-type coupling and might favor large values of the unknown mass scale M for
a. electrons b. neutrinos c. spinors d. space-time.
Q15. arXiv:1812.08575 [astro-ph.GA]: Modelling Cosmic Infrared Background with evolving galaxies: A.A. Ermash, S.V. Pilipenko, V.N. Lukash. (Submitted on 20 Dec 2018) ABSTRACT: Sensitivity of future far infrared space telescopes like Millimetron will be limited by a confusion noise created by distant galaxies. We construct a model of the Cosmic Infrared Background (CIB) aimed at exploration of methods of prediction and reducing the confusion noise. The model is based on a public available eGALICS simulation. For each simulated galaxy, we construct a spectral energy distribution with the help of public GRASIL and CHE_EVO codes. In this paper, in order to put our model in the context of current CIB investigations, we compare the outputs of the model: luminosity and mass functions, source counts as a function of flux and redshift, spectrum of the CIB, prediction of confusion limit, with the available observational data and with three other models: one is a well known ` backward evolution' model of Bethermin et al. 2011 and two others are based on a simple mass-luminosity (M-L) relation applied to simulated dark matter halo catalogs. We conclude that our model reproduces the observational data reasonably well. All four models show significant differences in the predictions of the distribution of sources on the flux-redshift plane, especially at high redshifts. The predicted confusion noise on the wavelengths 70--350 microns is consistent between models, while for 650--2000 microns there are significant differences and M-L models should not be used. CONCLUSIONS: We used different methods to estimate confusion limits for telescopes with diameters of 0.85 m–25 m on wavelengths 75– 2000 µm.Itwasdiscussedhowtheshapeofthecurveofthesource number counts affects the confusion noise estimates. We conclude that simple models, based on the mass-luminosity relation, can be used to reliably predict the confusion noise for Millimetron or other 10-m class telescopes only for wavelengths shorter than 650 microns. For larger wavelengths, more sophisticated models are needed. Our new model, based on public eGALICS simulation and GRASIL and CHE_EVO codes, turned out to be consistent with observational data and allows to explore the confusion limit in the whole range of wavelengths accessible by Millimetron. We have also tested the source counts in optical wavelengths, which may be helpful in testing methods of reducing the confusion noise which uses information from
a. positive bands. b. multiple bands. c. noise. d. wavelengths.
a. positive bands. b. multiple bands. c. noise. d. wavelengths.
Q16.arXiv:1812.08281 [astro-ph.GA]: Dust charge distribution in the interstellar medium. Juan C. Ibáñez-Mejía, Stefanie Walch, Alexei V. Ivlev, Seamus Clarke, Paola Caselli, Prabesh R. Joshi. (Submitted on 19 Dec 2018): ABSTRACT: We investigate the equilibrium charge distribution of dust grains in the interstellar medium (ISM). Our treatment accounts for collisional charging by electrons and ions, photoelectric charging due to a background interstellar radiation field, the collection of suprathermal cosmic ray electrons and photoelectric emission due to a cosmic ray induced ultraviolet radiation field within dense molecular clouds. We find that the charge equilibrium assumption is valid throughout the multi-phase ISM conditions investigated here, and should remain valid for simulations with resolutions down to AU scales. The charge distribution of dust grains is size, composition, and ISM environment dependent: local radiation field strength, G, temperature, T, and electron number density, ne. The charge distribution is tightly correlated with the `charging parameter', G√T / ne. In the molecular medium, both carbonaceous and silicate grains have predominantly negative or neutral charges with narrow distributions. In the cold neutral medium, carbonaceous and silicate grains vary from negative and narrow distributions to predominantly positive and wide distributions depending on the magnitude of the charging parameter. In the warm neutral medium, grains of all sizes are positively charged with wide distributions. We derive revised parametric expressions that can be used to recover the charge distribution function of carbonaceous and silicate grains from 3.5Å to 0.25μm as a function of the size, composition and ambient ISM parameters. Finally, we find that the parametric equations can be used in environments other than Solar neighborhood conditions, recovering the charge distribution function of dust grains in photon-dominated regions. Finally, we test the validity of the assumption of the charge equilibrium used to calculate the distribution function by comparing the charging timescale of dust grains with the hydrodynamical timescale constrained by the simulation timestep. We find that the equilibrium charge distribution assumption is valid for ISM simulations with sub-parsec resolution, and would remain valid for simulations with AU scale
a. resolution b. dependence c. distribution d. parameter.
Q17. arXiv:1812.10543 [astro-ph.SR]: Time evolution of rotating and magnetized white dwarf stars. Laura Becerra, Kuantay Boshkayev, Jorge. A. Rueda, Remo Ruffini. (Submitted on 26 Dec 2018): ABSTRACT: We investigate the evolution of isolated, zero and finite temperature, massive, uniformly rotating and highly magnetized white dwarf stars under angular momentum loss driven by magnetic dipole braking. We consider the structure and thermal evolution of the white dwarf isothermal core taking also into account the nuclear burning and neutrino emission processes. We estimate the white dwarf lifetime before it reaches the condition either for a type Ia supernova explosion or for the gravitational collapse to a neutron star. We analyze the behavior of the WD parameters such as the central density, radius, moment of inertia, angular momentum, angular velocity, central temperature and magnetic field intensity as a function of lifetime. In addition, we compute the characteristic time of nuclear reactions and dynamical time scale. The astrophysical consequences of the results are discussed. DETAILS: In this work we investigate the time evolution of massive, uniformly rotating, highly magnetized white dwarfs (WDs) when they lose angular momentum owing to magnetic dipole braking. We have different important reasons to perform such an investigation. CONCLUDING REMARKS We have investigated in this work the evolution of the WD structure while it loses angular momentum via magnetic dipole braking. We obtained the following conclusion. We have computed the life time of SCWD sas the total time it spends in reaching one of the following possible instabilities: massshedding, secular axisymmetric instability and inverse β decay instability. The life time is inversely proportional both to the magnetic field and to the mass of the
a. SCWD b. neutron star c. magnetic dipole d. WD.
Q18. arXiv:1812.10440 [astro-ph.SR]: On the mechanism of radio emission in type III Solar Radiobursts. Vladimir Krasnoselskikh, Andrii Voshchepynets, Milan Maksimovic. (Submitted on 26 Dec 2018): ABSTRACT: Type III solar radio bursts are generated by streams of energetic electrons accelerated at the Sun during periods of the solar activity. The generation occurs in two steps. Initially, electron beams generate electrostatic Langmuir waves and then these waves are transformed in electromagnetic emissions. It is widely accepted that the mechanism of generation of emission on fundamental frequency close to plasma frequency is due to induced scattering of Langmuir waves into electromagnetic. However this process imposes quite restrictive limit of the ratios of effective brightness temperatures of electromagnetic and Langmuir waves in the source region. Recent studies showed that the level of density fluctuations in the solar wind and in the solar corona is so high that it may significantly affect beam-plasma interaction. Here we show that the presence of intense density fluctuations not only crucially influence the process of beam plasma interaction but also changes the mechanism of energy transfer from electrostatic waves into electromagnetic. Reflection of the Langmuir waves from the density inhomogeneities may result in partial transformation of the energy of electrostatic wave into electromagnetic. We show that the linear wave energy transformation for the level of fluctuations of the order of 1\% or higher may be significantly more efficient for generation of type III solar radio bursts than conventionally considered process of nonlinear conversion due to induced scattering on ions. DETAILS: Solar type III radio bursts are amongst the strongest radio emissions in the heliosphere. It is wildly accepted that the high energy electrons ∼ 5−30 keV, accelerated during reconnection of the magnetic flied lines in solar atmosphere, are responsible for generation of these radio emission. CONCLUSIONS: We show that the process of linear conversion of Langmuir waves onto electromagnetic on density fluctuations can be dominant for the generation of the type III radio emissions and is significantly more efficient than conventionally accepted nonlinear process of induced scattering of Langmuir waves on ions. As we show the efficiency of linear conversion is strongly dependent upon statistical properties of density fluctuations and their gradients. These characteristics may significantly vary with the distance from the
a. plasma b. Waves c. Sun d. atmosphere
Q19. Q19. arXiv:1812.08811 [astro-ph.SR]: Infrared Spectroscopy of Symbiotic Stars. XII. The Neutron Star SyXB System 4U 1700+24 = V934 Herculis. K. H. Hinkle, F. C. Fekel, R. R. Joyce, J. Mikołajewska, C. Galan, T. Lebzelter. (Submitted on 20 Dec 2018): ABSTRACT: V934 Her = 4U1700+24 is an M giant-neutron star (NS) X-ray symbiotic (SyXB) system. Employing optical and infrared radial velocities spanning 29 years combined with the extensive velocities in the literature, we compute the spectroscopic orbit of the M giant in that system. We determine an orbital period of 4391 days or 12.0 yr, the longest for any SyXB, and far longer than the 404 day orbit commonly cited for this system in the literature. In addition to the 12.0 yr orbital period we find a shorter period of 420 days, similar to the one previously found. Instead of orbital motion, we attribute this much shorter period to long secondary pulsation of the M3 III SRb variable. Our new orbit supports earlier work that concluded that the orbit is seen nearly pole on, which is why X-ray pulsations associated with the NS have not been detected. We estimate an orbital inclination of 11.3± 0.4∘. Arguments are made that this low inclination supports a pulsation origin for the 420 day long secondary period. We also measure CNO and Fe peak abundances of the M giant and find it to be slightly metal poor compared to the Sun with no trace of the NS forming SN event. Basic properties of the M giant and NS are derived. We discuss the possible evolutionary paths that this system has taken to get to its current state. DETAILS: Garcia et al. (1983) found three emission lines in the IUE ultraviolet spectrum of HD 154791 that are not seen in normal M giant spectra. These UV emission lines have variable strengths associated with variations in the X-ray flux, strengthening the connection with an accretion process. In addition, It is found the He I 10830 ˚A line is present with strong emission and absorption. The He I 10830 ˚A 2 3S - 2 3P line has a metastable lower state 20 eV above the ground state and is diagnostic of binary star X-ray activity. However, Sokoloski et al. found no flickering in B with a limit of ∼10 mmag. CONCLUSIONS: We have compared the properties of the V934 Her M giant to those of the M giant in the SyXB binary V2116 Oph. Both are of similar luminosity and both appear to be on the giant branch or early AGB. It seems likely that V2116 Oph is the most X-ray luminous of the SyXB because of higher mass loss from its cooler M5/6 giant combined with a relatively short, for an SyXB, 3.18 yr orbital period. The separation between the components in the V2116 Oph system is about half that of the V934 Her system. V2116 Oph and V934 Her are the only two members of the SyXB group with determined orbits. The lack of optical emission lines in the M giant spectra and the ultra-long NS pulse periods in other SyXB strongly suggest that these systems are similar to V934 Her with long orbital
a. luminity b. giants c. periods d. losses
Q20. arXiv:1812.07735 [astro-ph.SR]: 3He-Rich Solar Energetic Particles from Sunspot Jets. R. Bucik, M. E. Wiedenbeck, G. M. Mason, R. Gomez-Herrero, N. Nitta, L. Wang (Submitted on 19 Dec 2018): ABSTRACT: Solar sources of suprathermal (<1 MeV/nucleon) 3He-rich solar energetic particles (SEPs) have been commonly associated with jets originating in small, compact active regions at the periphery of near-equatorial coronal holes. Sources of relatively rare, high-energy (>10 MeV/nucleon) 3He-rich SEPs remain unexplored. Here we present two of the most intense 3He-rich (3He/4He>1) SEP events of the current solar cycle 24 measured on the Advanced Composition Explorer at energy >10 MeV/nucleon. Although 3He shows high intensities, Z>2 ions are below the detection threshold. The events are accompanied by type-III radio bursts, but no type-II emission as typically seen for suprathermal 3He-rich SEPs. The corresponding solar sources were analyzed using high-resolution, extreme-ultraviolet imaging and photospheric magnetic field observations on the Solar Dynamics Observatory. We find the sources of these events associated with jets originating at the boundary of large sunspots with complex beta-gamma-delta magnetic configuration. Thus, details of the underlying photospheric field apparently are important to produce 3He to high energies in the examined events. DETAILS: 3He-rich solar energetic particles (SEPs) are characterized by a peculiar ion composition markedly different from the coronaor solarwind. The abundance of 3He is enhanced by factors up to 104; heavy (Ne–Fe) and ultra-heavy ions (Z>30) show enhancement by factors ~3–10 and >100, respectively, independently of 3He enhancement. 3He-rich SEPs are firmly associated with type-III radio bursts and their parent low-energy electrons. DISCUSSION AND SUMMARY: We have examined the solar sources of the two most intense high-energy (>10MeVnucleon^ −1) 3He-rich SEP events of the current solar cycle. We have found that the solar sources of the 3He-rich SEPs were structured jets, in one case with an untwisting motion. A striking feature of the investigated events is their association with jets originating at the boundaries of large and complex sunspots with βγδ magnetic class. The sunspots produced numerous (63 and 129) X-ray flares during their disk transit. The August 24 event was accompanied by four type-III bursts within one hour, suggesting that the extreme 3He intensity may be related to unresolved multiple ion injections. The February 18 event was associated with only a single type,
a. extreme. b. III burst. c. IV burst d. flare.
Q21.arXiv:1901.11290 [astro-ph.SR]: Rotating Solar Models with Low Metal Abundances as Good as Those with High Metal Abundances. Wuming Yang. (Submitted on 31 Jan 2019). ABSTRACT: Standard solar models (SSM) constructed in accord with low metal abundances disagree with the seismically inferred results. We constructed rotating solar models with low metal abundances that included enhanced settling and convection overshoot. In one of our rotating models, \textbf{AGSSr2a}, the convection overshoot allowed us to recover the radius of the base of convection zone (CZ) at a level of 1σ . The rotational mixing almost completely counteracts the enhanced settling for the surface helium abundance, but only partially for the surface heavy-element abundance. At the level of 1σ, the combination of rotation and enhanced settling brings the surface helium abundance into agreement with the seismically inferred value of 0.2485±0.0035 , and makes the model have better sound-speed and density profiles than SSM constructed in accordance with high metal abundances. The radius of the base of the CZ and the surface helium abundance of \textbf{AGSSr2a} are 0.713R ⊙ and 0.2472 , respectively; the absolute values of the relative differences in sound speed and density between it and the Sun are less than 0.0025 and 0.015, respectively. Moreover, predicted neutrino fluxes of our model are comparable with the predictions of previous research works. CONCLUSION: The main effect of convection overshoot is to bring the radius of the BCZ into agreement with the seismically inferred value at the level of 1σ. In the model, the velocities of diffusion and settling of helium and heavy elements of Thoul, Bahcall & Loeb (1994) are enhanced by 50%. Rotational mixing almost completely counteracts the increased settling for the surface helium abundance, but only partially for the heavyelement abundance in the CZ. As a consequence, the surface helium abundance of AGSSr2a is almost as high as that of GS98M, but the surface heavy-element abundance is lower. A combination of the enhanced settling and the effects of rotation allows us to recover the surface helium abundance at the level of 1σ and makes the model have better sound-speed and density profiles than GS98M. The effects of rotation should not be neglected in solar models. However, the internal angular velocity and total angular momentum of the rotating model are higher than the seismically inferred values. A mechanism mainly taking effect in inner layers of models’ radiative region is needed to solve the fast rotation
a. evolution b. problem c. assertion d. degradation.
Q22. arXiv:1901.11406 [physics.space-ph]: The Interplay of the Solar Wind Core and Suprathermal Electrons: A Quasilinear Approach for Firehose Instability. S.M.Shaaban, M. Lazar, P.H.Yoon, S. Poedts. (Submitted on 31 Jan 2019): ABSTRACT: In the solar wind an equipartition of kinetic energy densities can be easily established between thermal and suprathermal electrons and the instability conditions are markedly altered by the interplay of these two populations. The new thresholds derived here for the periodic branch of firehose instability shape the limits of temperature anisotropy reported by the observations for both electron populations. This instability constraint is particularly important for the suprathermal electrons which, by comparison to thermal populations, are even less controlled by the particle-particle collisions. An extended quasilinear approach of this instability confirms predictions from linear theory and unveil the mutual effects of thermal and suprathermal electrons in the relaxation of their temperature anisotropies and the saturation of growing fluctuations. CONCLUSION: In this study, we have restricted ourselves to the unstable periodic firehose modes that develop with a highest growth rate in directions parallel to the background magnetic field. A QL approach of the aperiodic firehose modes growing faster in the oblique directions is not yet feasible, but our present results will certainly stimulate an extended analysis. Furthermore, the influence of the solar wind inhomogeneity has not been considered in the present analysis, and their interplay with the effects of suprathermal electrons will be investigated in the
a. past b. study c. future d. advance.
a. Constraints b. Laggrangians c. symmetry d. Standard Model.
Q25. arXiv:1901.11025 [quant-ph]: Two body problems with magnetic interactions. Hesham Mansour, Ahmed Gamal. (Submitted on 30 Jan 2019)ABSTRACT: In the present work, we present different two body potentials which have oscillatory shapes. The eigenvalues and eigenfunctions are obtained for those problems by solving Schrodinger equation using Nikiforov Uvarov method. Conclusion: In the present paper, we discussed some special cases of the two-body potentials which have an oscillatory shape. The energy eigenvalues and eigenfunctions for bound states of such potentials have been obtained by Nikiforov-Uvarov method. The obtained results are useful in nuclear physics and quantum mechanics for magnetic
a. discord b. interfeerence c. measurement d. disobediance.
Q27. arXiv:1812.08048 [cond-mat.mes-hall]: Electric dipole spin resonance at shallow donors in quantum wires. D.V. Khomitsky, E.A. Lavrukhina, E.Ya. Sherman. (Submitted on 19 Dec 2018 (v1), last revised 31 Jan 2019 (this version, v2)): ABSTRACT: Electric dipole spin resonance is studied theoretically at a shallow donor formed in a nanowire with spin-orbit coupling in a magnetic field. Such system may represent a donor-based qubit. The single discrete energy level of the donor is accompanied by the set of continuum states, which provide a non-trivial interplay for the picture of electric dipole spin resonance driven by an external monochromatic field. Strongly nonlinear dependencies of spin flip time as well as of the coordinate mean values on the electric field amplitude are observed, demonstrating the significance of coupling to the continuum for spin-based qubits manipulation in nanostructures. INTRODUCTION: Electric dipole spin resonance (EDSR), that is the ability to manipulate spins of charge carriers by electic rather than by a magnetic field, is one of the most distinctive features of spin-orbit coupling (SOC). Being theoretically predicted [1] and initially experimentally observed for itinerant electrons in bulk crystals [2–4], soon it was studied theoretically in detail for electrons localized on donors [5] and for holes on the acceptor centers [6]. More recently, it was shown that the EDSR is a powerful tool for spin manipulation in quantum wells [7] and other twodimensional heterostructures with spin-orbit coupling [8]. In addition, the EDSR can be used to manipulate electic current in low-dimensional conductors [9]. Observation of the EDSR in quantum dots [10] opened a venue for their applications in spin-based quantum computing, where spin of a carrier localized in a quantum dot is considered as a qubit. CONCLUSIONS: We studied the electric dipole spin resonance for a nanowire-based donor states coupled to the continuum, the latter playing a critical role in the dynamics. The continuum leads to a strongly nonlinear dependence of the evolution of spin and position on the electric field. The observed characteristics of both spin and position dynamics, having much in common, for different values of magnetic field and spin-orbit coupling, can be of interest for designing novel types of spin and charge qubits when the confining potentials are shallow, and the discrete states strongly interact with the continuum during the qubit operation. For this reason, these effects should be taken into account for possible applications of materials with strong spin-orbit coupling such as InSb for fabricating the qubit-processing
a. resolution b. dependence c. distribution d. parameter.
Q17. arXiv:1812.10543 [astro-ph.SR]: Time evolution of rotating and magnetized white dwarf stars. Laura Becerra, Kuantay Boshkayev, Jorge. A. Rueda, Remo Ruffini. (Submitted on 26 Dec 2018): ABSTRACT: We investigate the evolution of isolated, zero and finite temperature, massive, uniformly rotating and highly magnetized white dwarf stars under angular momentum loss driven by magnetic dipole braking. We consider the structure and thermal evolution of the white dwarf isothermal core taking also into account the nuclear burning and neutrino emission processes. We estimate the white dwarf lifetime before it reaches the condition either for a type Ia supernova explosion or for the gravitational collapse to a neutron star. We analyze the behavior of the WD parameters such as the central density, radius, moment of inertia, angular momentum, angular velocity, central temperature and magnetic field intensity as a function of lifetime. In addition, we compute the characteristic time of nuclear reactions and dynamical time scale. The astrophysical consequences of the results are discussed. DETAILS: In this work we investigate the time evolution of massive, uniformly rotating, highly magnetized white dwarfs (WDs) when they lose angular momentum owing to magnetic dipole braking. We have different important reasons to perform such an investigation. CONCLUDING REMARKS We have investigated in this work the evolution of the WD structure while it loses angular momentum via magnetic dipole braking. We obtained the following conclusion. We have computed the life time of SCWD sas the total time it spends in reaching one of the following possible instabilities: massshedding, secular axisymmetric instability and inverse β decay instability. The life time is inversely proportional both to the magnetic field and to the mass of the
a. SCWD b. neutron star c. magnetic dipole d. WD.
Q18. arXiv:1812.10440 [astro-ph.SR]: On the mechanism of radio emission in type III Solar Radiobursts. Vladimir Krasnoselskikh, Andrii Voshchepynets, Milan Maksimovic. (Submitted on 26 Dec 2018): ABSTRACT: Type III solar radio bursts are generated by streams of energetic electrons accelerated at the Sun during periods of the solar activity. The generation occurs in two steps. Initially, electron beams generate electrostatic Langmuir waves and then these waves are transformed in electromagnetic emissions. It is widely accepted that the mechanism of generation of emission on fundamental frequency close to plasma frequency is due to induced scattering of Langmuir waves into electromagnetic. However this process imposes quite restrictive limit of the ratios of effective brightness temperatures of electromagnetic and Langmuir waves in the source region. Recent studies showed that the level of density fluctuations in the solar wind and in the solar corona is so high that it may significantly affect beam-plasma interaction. Here we show that the presence of intense density fluctuations not only crucially influence the process of beam plasma interaction but also changes the mechanism of energy transfer from electrostatic waves into electromagnetic. Reflection of the Langmuir waves from the density inhomogeneities may result in partial transformation of the energy of electrostatic wave into electromagnetic. We show that the linear wave energy transformation for the level of fluctuations of the order of 1\% or higher may be significantly more efficient for generation of type III solar radio bursts than conventionally considered process of nonlinear conversion due to induced scattering on ions. DETAILS: Solar type III radio bursts are amongst the strongest radio emissions in the heliosphere. It is wildly accepted that the high energy electrons ∼ 5−30 keV, accelerated during reconnection of the magnetic flied lines in solar atmosphere, are responsible for generation of these radio emission. CONCLUSIONS: We show that the process of linear conversion of Langmuir waves onto electromagnetic on density fluctuations can be dominant for the generation of the type III radio emissions and is significantly more efficient than conventionally accepted nonlinear process of induced scattering of Langmuir waves on ions. As we show the efficiency of linear conversion is strongly dependent upon statistical properties of density fluctuations and their gradients. These characteristics may significantly vary with the distance from the
a. plasma b. Waves c. Sun d. atmosphere
Q19. Q19. arXiv:1812.08811 [astro-ph.SR]: Infrared Spectroscopy of Symbiotic Stars. XII. The Neutron Star SyXB System 4U 1700+24 = V934 Herculis. K. H. Hinkle, F. C. Fekel, R. R. Joyce, J. Mikołajewska, C. Galan, T. Lebzelter. (Submitted on 20 Dec 2018): ABSTRACT: V934 Her = 4U1700+24 is an M giant-neutron star (NS) X-ray symbiotic (SyXB) system. Employing optical and infrared radial velocities spanning 29 years combined with the extensive velocities in the literature, we compute the spectroscopic orbit of the M giant in that system. We determine an orbital period of 4391 days or 12.0 yr, the longest for any SyXB, and far longer than the 404 day orbit commonly cited for this system in the literature. In addition to the 12.0 yr orbital period we find a shorter period of 420 days, similar to the one previously found. Instead of orbital motion, we attribute this much shorter period to long secondary pulsation of the M3 III SRb variable. Our new orbit supports earlier work that concluded that the orbit is seen nearly pole on, which is why X-ray pulsations associated with the NS have not been detected. We estimate an orbital inclination of 11.3± 0.4∘. Arguments are made that this low inclination supports a pulsation origin for the 420 day long secondary period. We also measure CNO and Fe peak abundances of the M giant and find it to be slightly metal poor compared to the Sun with no trace of the NS forming SN event. Basic properties of the M giant and NS are derived. We discuss the possible evolutionary paths that this system has taken to get to its current state. DETAILS: Garcia et al. (1983) found three emission lines in the IUE ultraviolet spectrum of HD 154791 that are not seen in normal M giant spectra. These UV emission lines have variable strengths associated with variations in the X-ray flux, strengthening the connection with an accretion process. In addition, It is found the He I 10830 ˚A line is present with strong emission and absorption. The He I 10830 ˚A 2 3S - 2 3P line has a metastable lower state 20 eV above the ground state and is diagnostic of binary star X-ray activity. However, Sokoloski et al. found no flickering in B with a limit of ∼10 mmag. CONCLUSIONS: We have compared the properties of the V934 Her M giant to those of the M giant in the SyXB binary V2116 Oph. Both are of similar luminosity and both appear to be on the giant branch or early AGB. It seems likely that V2116 Oph is the most X-ray luminous of the SyXB because of higher mass loss from its cooler M5/6 giant combined with a relatively short, for an SyXB, 3.18 yr orbital period. The separation between the components in the V2116 Oph system is about half that of the V934 Her system. V2116 Oph and V934 Her are the only two members of the SyXB group with determined orbits. The lack of optical emission lines in the M giant spectra and the ultra-long NS pulse periods in other SyXB strongly suggest that these systems are similar to V934 Her with long orbital
a. luminity b. giants c. periods d. losses
Q20. arXiv:1812.07735 [astro-ph.SR]: 3He-Rich Solar Energetic Particles from Sunspot Jets. R. Bucik, M. E. Wiedenbeck, G. M. Mason, R. Gomez-Herrero, N. Nitta, L. Wang (Submitted on 19 Dec 2018): ABSTRACT: Solar sources of suprathermal (<1 MeV/nucleon) 3He-rich solar energetic particles (SEPs) have been commonly associated with jets originating in small, compact active regions at the periphery of near-equatorial coronal holes. Sources of relatively rare, high-energy (>10 MeV/nucleon) 3He-rich SEPs remain unexplored. Here we present two of the most intense 3He-rich (3He/4He>1) SEP events of the current solar cycle 24 measured on the Advanced Composition Explorer at energy >10 MeV/nucleon. Although 3He shows high intensities, Z>2 ions are below the detection threshold. The events are accompanied by type-III radio bursts, but no type-II emission as typically seen for suprathermal 3He-rich SEPs. The corresponding solar sources were analyzed using high-resolution, extreme-ultraviolet imaging and photospheric magnetic field observations on the Solar Dynamics Observatory. We find the sources of these events associated with jets originating at the boundary of large sunspots with complex beta-gamma-delta magnetic configuration. Thus, details of the underlying photospheric field apparently are important to produce 3He to high energies in the examined events. DETAILS: 3He-rich solar energetic particles (SEPs) are characterized by a peculiar ion composition markedly different from the coronaor solarwind. The abundance of 3He is enhanced by factors up to 104; heavy (Ne–Fe) and ultra-heavy ions (Z>30) show enhancement by factors ~3–10 and >100, respectively, independently of 3He enhancement. 3He-rich SEPs are firmly associated with type-III radio bursts and their parent low-energy electrons. DISCUSSION AND SUMMARY: We have examined the solar sources of the two most intense high-energy (>10MeVnucleon^ −1) 3He-rich SEP events of the current solar cycle. We have found that the solar sources of the 3He-rich SEPs were structured jets, in one case with an untwisting motion. A striking feature of the investigated events is their association with jets originating at the boundaries of large and complex sunspots with βγδ magnetic class. The sunspots produced numerous (63 and 129) X-ray flares during their disk transit. The August 24 event was accompanied by four type-III bursts within one hour, suggesting that the extreme 3He intensity may be related to unresolved multiple ion injections. The February 18 event was associated with only a single type,
a. extreme. b. III burst. c. IV burst d. flare.
Q21.arXiv:1901.11290 [astro-ph.SR]: Rotating Solar Models with Low Metal Abundances as Good as Those with High Metal Abundances. Wuming Yang. (Submitted on 31 Jan 2019). ABSTRACT: Standard solar models (SSM) constructed in accord with low metal abundances disagree with the seismically inferred results. We constructed rotating solar models with low metal abundances that included enhanced settling and convection overshoot. In one of our rotating models, \textbf{AGSSr2a}, the convection overshoot allowed us to recover the radius of the base of convection zone (CZ) at a level of 1σ . The rotational mixing almost completely counteracts the enhanced settling for the surface helium abundance, but only partially for the surface heavy-element abundance. At the level of 1σ, the combination of rotation and enhanced settling brings the surface helium abundance into agreement with the seismically inferred value of 0.2485±0.0035 , and makes the model have better sound-speed and density profiles than SSM constructed in accordance with high metal abundances. The radius of the base of the CZ and the surface helium abundance of \textbf{AGSSr2a} are 0.713R ⊙ and 0.2472 , respectively; the absolute values of the relative differences in sound speed and density between it and the Sun are less than 0.0025 and 0.015, respectively. Moreover, predicted neutrino fluxes of our model are comparable with the predictions of previous research works. CONCLUSION: The main effect of convection overshoot is to bring the radius of the BCZ into agreement with the seismically inferred value at the level of 1σ. In the model, the velocities of diffusion and settling of helium and heavy elements of Thoul, Bahcall & Loeb (1994) are enhanced by 50%. Rotational mixing almost completely counteracts the increased settling for the surface helium abundance, but only partially for the heavyelement abundance in the CZ. As a consequence, the surface helium abundance of AGSSr2a is almost as high as that of GS98M, but the surface heavy-element abundance is lower. A combination of the enhanced settling and the effects of rotation allows us to recover the surface helium abundance at the level of 1σ and makes the model have better sound-speed and density profiles than GS98M. The effects of rotation should not be neglected in solar models. However, the internal angular velocity and total angular momentum of the rotating model are higher than the seismically inferred values. A mechanism mainly taking effect in inner layers of models’ radiative region is needed to solve the fast rotation
a. evolution b. problem c. assertion d. degradation.
Q22. arXiv:1901.11406 [physics.space-ph]: The Interplay of the Solar Wind Core and Suprathermal Electrons: A Quasilinear Approach for Firehose Instability. S.M.Shaaban, M. Lazar, P.H.Yoon, S. Poedts. (Submitted on 31 Jan 2019): ABSTRACT: In the solar wind an equipartition of kinetic energy densities can be easily established between thermal and suprathermal electrons and the instability conditions are markedly altered by the interplay of these two populations. The new thresholds derived here for the periodic branch of firehose instability shape the limits of temperature anisotropy reported by the observations for both electron populations. This instability constraint is particularly important for the suprathermal electrons which, by comparison to thermal populations, are even less controlled by the particle-particle collisions. An extended quasilinear approach of this instability confirms predictions from linear theory and unveil the mutual effects of thermal and suprathermal electrons in the relaxation of their temperature anisotropies and the saturation of growing fluctuations. CONCLUSION: In this study, we have restricted ourselves to the unstable periodic firehose modes that develop with a highest growth rate in directions parallel to the background magnetic field. A QL approach of the aperiodic firehose modes growing faster in the oblique directions is not yet feasible, but our present results will certainly stimulate an extended analysis. Furthermore, the influence of the solar wind inhomogeneity has not been considered in the present analysis, and their interplay with the effects of suprathermal electrons will be investigated in the
a. past b. study c. future d. advance.
Q23. arXiv:1901.11214 [gr-qc]: Charged Particle and Strong Cosmic Censorship in Reissner-Nordström-de Sitter Black Holes. Yongwan Gim, Bogeun Gwak. (Submitted on 31 Jan 2019). ABSTRACT: We investigate the instability of the unstable circular orbit of a charged null particle to test the strong cosmic censorship conjecture in the near-extremal Reissner-Nordström-de Sitter black hole. The instability is estimated as the Lyapunov exponent and found to depend on the mass and charge of the black hole. Then, we explicitly show that the charged null particle in the unstable circular orbits corresponds to the charged massless scalar field in the eikonal limit. This provides a compact relation representing the quasinormal frequency in terms of the characteristics of unstable circular orbits. According to the relation, the strong cosmic censorship conjecture is valid. Summary: We investigated the validity of the SCC conjecture in the near-extremal RNdS black hole using the Lyapunov exponent of the charged null particle in the circular null geodesic. Since the SCC conjecture has to be discussed in QNMs, the relationship between the Lyapunov exponent and QNMs is generalized to the case of the charged massless scalar field corresponding to the charged null particle. Then, we compute the Lyapunov exponent representing the instabilities of orbits in RNdS black holes. By using the instability time scale associated with the Lyapunov exponent, the circular null orbits of the charged null particle around the extremal black hole in ri = ro are more stable than those around the extremal black hole in ro = rc. Further, since the decay rate in the QNM with the eikonal limit can be written in the analytical form in the case of the near-extremal RNdS black hole, we imposed the same assumption on the Lyapunov exponent of the charged null particle. Thus, we found the compact relationship between the Lyapunov exponent and QNMs in Eq.(49) for the charged case. According to the compact relationship in the charged case, the decay rate in the near-extremal black hole of ro = rc represents β < 1/2. This implies that the SCC conjecture is valid in our analysis based on the Lyapunov
a. exponent b. charg c. particle d. conjecture
Q24. arXiv:1901.11312 [gr-qc]: Spin connection formulations of real Lorentzian General Relativity, Ermis Mitsou, (Submitted on 31 Jan 2019):ABSTRACT: We derive the pure spin connection and constraint-free BF formulations of real four-dimensional Lorentzian vacuum General Relativity. In contrast to the existing complex formulations, an important advantage is that they do not require the reality constraints that complicate quantization. We also consider the corresponding modified gravity theories and point out that, contrary to their self-dual analogues, they are not viable because they necessarily contain ghosts. In particular, this constrains the set of potentially viable unified theories one can build by extending the gauge group to the ones with the action structure of General Relativity. We find, however, that the resulting theories do not admit classical solutions. This issue can be solved by introducing extra dynamical fields which, incidentally, could also provide a way to include a matter sector. INTRODUCTION:Alternative formulations of classical General Relativity (GR) provide us with important insights about the theory, new perspectives for potential modifications or extensions and also genuinely new starting points for approaching the quantum theory. One line of research in this direction are the so-called “pure connection” formulations, where the usual gravitational field that is a metric or a vierbein, is replaced by a connection associated with some group, in close analogy with the mathematical description we have for the rest of the known forces of nature. In fact, this suggestive resemblance is an important motivation for this approach, because enlarging the gauge group leads to extra connection components and therefore constitutes an elegant potential path towards unification (see the review [1] and references therein). If one considers the metric formalism, then the only available group is the diffeomorphism group, so extending it necessarily introduces extra dimensions. In the vierbein formalism, however, we have the internal action of the Lorentz group, so the latter can be extended without altering the dimensionality of space-time. CONCLUSION:In particular, the vacuum solution of physical interest, where space-time exists and the extra forces are trivial, would correspond to the VEV of z2 being some pure-Lorentz invariant matrix, thus providing the desired dynamical symmetry breaking mechanism G → SO(1,3)×G′. Observe also that it is necessary to make hα dynamical, because otherwise it would alter the ψ-dependence of the action, thus introducing ghosts. In fact, although we have maintained the GR structure in this extension, it is not at all guaranteed that a Lagrangian of the form maintains the desired second-class constraints, or that it is devoid of pathologies in general, and a dedicated study should be carried out. We leave this to future work. Finally, note that the presence of fields like hα and πα is also welcome for another reason, namely, because they allow us to include the type of fields one encounters in the matter sector of the a. Constraints b. Laggrangians c. symmetry d. Standard Model.
Q25. arXiv:1901.11025 [quant-ph]: Two body problems with magnetic interactions. Hesham Mansour, Ahmed Gamal. (Submitted on 30 Jan 2019)ABSTRACT: In the present work, we present different two body potentials which have oscillatory shapes. The eigenvalues and eigenfunctions are obtained for those problems by solving Schrodinger equation using Nikiforov Uvarov method. Conclusion: In the present paper, we discussed some special cases of the two-body potentials which have an oscillatory shape. The energy eigenvalues and eigenfunctions for bound states of such potentials have been obtained by Nikiforov-Uvarov method. The obtained results are useful in nuclear physics and quantum mechanics for magnetic
a. profiles b. potntials c.interactions. d. superpositins
Q26. arXiv:1901.11514 [quant-ph]: How to observe and quantify quantum-discorded states. Matthew A. Hunt, Igor V. Lerner, Igor V. Yurkevich, Yuval Gefen. (Submitted on 31 Jan 2019): ABSTRACT: Quantum correlations between parts of a composite system most clearly reveal themselves through entanglement. Designing, maintaining, and controlling entangled systems is very demanding, which raises the stakes for understanding the efficacy of entanglement-free, yet quantum, correlations, exemplified by quantum discord. Discord is defined via conditional mutual entropies of parts of a composite system, and its direct measurement is hardly possible even via full tomographic characterization of the system state. Here we design a simple protocol to detect quantum discord and characterize a discorded state in an unentangled bipartite system. Our protocol is based on an electronic setup and relies on a characteristic of discord that can be extracted from repeated direct measurements of current correlations between subsystems. The proposed protocol opens a way of extending experimental studies of discord to many-body condensed matter systems. Conclusion. We have proposed a new characterization of quantum discord based on measuring crosscorrelations in non-entangled bipartite systems and thus linear in density matrix ρ, in contrast to other quantifiers, notably geometric discord, that require full or partial quantum tomography for reconstruction of ρ. The linearity of the proposed quantifier opens a path to extending experimental research of discord into electronic condensed matter systems. We have considered in detail one possible implementation via devices built of Mach – Zehnder interferometers in quantum Hall systems, where our quantifier is quite robust against external noise and uctuations: as long as the Aharonov–Bohm oscillations are resolvable [31], the appropriate interference pattern may serve as a pictorial discord witness, as illustrated above in Figs. 2 and 3. Finally, our discord quantifier is qualitatively consistent, and quantitatively very close to the original measure. The relative simplicity of this protocol, and the fact that it is based on presently existing measurement technologies and available setups (electronic Mach-Zehnder interferometers) is bound to stimulate experiments in this direction. While the present analysis addresses discord of bi-partite systems, an intriguing generalization of our protocol to multiply-partite systems is possible by introducing a number of coupled interferometers Extension of our protocol to anyon-based states (employing anyonic interferometers) or other topological states may open the horizon to topology-based study of a. discord b. interfeerence c. measurement d. disobediance.
Q27. arXiv:1812.08048 [cond-mat.mes-hall]: Electric dipole spin resonance at shallow donors in quantum wires. D.V. Khomitsky, E.A. Lavrukhina, E.Ya. Sherman. (Submitted on 19 Dec 2018 (v1), last revised 31 Jan 2019 (this version, v2)): ABSTRACT: Electric dipole spin resonance is studied theoretically at a shallow donor formed in a nanowire with spin-orbit coupling in a magnetic field. Such system may represent a donor-based qubit. The single discrete energy level of the donor is accompanied by the set of continuum states, which provide a non-trivial interplay for the picture of electric dipole spin resonance driven by an external monochromatic field. Strongly nonlinear dependencies of spin flip time as well as of the coordinate mean values on the electric field amplitude are observed, demonstrating the significance of coupling to the continuum for spin-based qubits manipulation in nanostructures. INTRODUCTION: Electric dipole spin resonance (EDSR), that is the ability to manipulate spins of charge carriers by electic rather than by a magnetic field, is one of the most distinctive features of spin-orbit coupling (SOC). Being theoretically predicted [1] and initially experimentally observed for itinerant electrons in bulk crystals [2–4], soon it was studied theoretically in detail for electrons localized on donors [5] and for holes on the acceptor centers [6]. More recently, it was shown that the EDSR is a powerful tool for spin manipulation in quantum wells [7] and other twodimensional heterostructures with spin-orbit coupling [8]. In addition, the EDSR can be used to manipulate electic current in low-dimensional conductors [9]. Observation of the EDSR in quantum dots [10] opened a venue for their applications in spin-based quantum computing, where spin of a carrier localized in a quantum dot is considered as a qubit. CONCLUSIONS: We studied the electric dipole spin resonance for a nanowire-based donor states coupled to the continuum, the latter playing a critical role in the dynamics. The continuum leads to a strongly nonlinear dependence of the evolution of spin and position on the electric field. The observed characteristics of both spin and position dynamics, having much in common, for different values of magnetic field and spin-orbit coupling, can be of interest for designing novel types of spin and charge qubits when the confining potentials are shallow, and the discrete states strongly interact with the continuum during the qubit operation. For this reason, these effects should be taken into account for possible applications of materials with strong spin-orbit coupling such as InSb for fabricating the qubit-processing
a. fields b. structures c. qubits d. electric fields
Q28. February 02, 2019 7:13 IST: United States: Death toll crosses 2 dozen as polar vortex moves in. Hennepin Healthcare in Minneapolis normally sees around 30 frostbite patients in an entire winter. It admitted 18 in the past week.
arXiv:1901.08588 [gr-qc]: 23 Jan. 2019: On the cosmological constant problem. Lucas Lombriser. (Submitted on 23 Jan 2019): ABSTRACT: An additional variation of the Einstein-Hilbert action with respect to the Planck mass provides a constraint on the average Ricci scalar that prevents vacuum energy from gravitating. Consideration of the evolution of the inhomogeneous matter distribution in the Universe with evaluation of the averaging constraint on disconnected matter cells that ultimately form isolated gravitationally bound structures yields a backreaction effect that self-consistently produces the cosmological constant of the background. A uniform prior on our location in the formation of these isolated structures implies a mean expectation for the present cosmological constant energy density parameter of Ω =0.704, giving rise to a late-time acceleration of the cosmic expansion and a coincident current energy density of matter. Introduction: The physical nature of the cosmological constant remains a persistent enigma immanent to Einstein’s Theory of General Relativity. It is generally thought to represent the gravitational contribution of vacuum fluctuations, anticipated of adequate magnitude to account for the observed late-time accelerated expansion of our Universe. CONCLUSIONS: A new framework was presented here that proposes the additional variation of the Einstein-Hilbert action with respect to the quadratic Planck mass on top of the usual metric variation. It offers the interpretation of identifying the Planck mass with a global Lagrange multiplier that imposes general relativistic dynamics on the metric prescribing the space-time for the matter fields. The variation provides a constraint equation on the average Ricci scalar that acts to prevent vacuum energy from gravitating. The evaluation of this constraint under consideration of the evolution of the inhomogeneous matter distribution in the Universe in form of disconnected matter cells representing ultimately isolated gravitationally bound structures yields a backreaction effect that self-consistently produces the cosmological constant of the background. With the application of a uniform prior on the dimensionless physical size of these structures as a measure of likelihood determining our location in the cosmic history, one finds a mean expectation for the current energy density parameter of the cosmological constant of ΩΛ = 0.704. The result is in good agreement with current cosmological observations, giving rise to a late-time acceleration of the cosmic expansion and a coincident current energy density of matter. Future analysis will reveal if the presented framework allows for a reinterpretation and possible unraveling of some cosmological obscurities such as coincidences identified for the epochs of recombination, reionization, and the star formation peak with the times of equality between the energy densities of radiation, baryons, and the cosmological constant. It may also motivate new approaches for other unresolved problems of
a. Relativity b. Gravitation c. Cosmology d. radiation
Q29. arXiv:1901.11223 [cond-mat.mtrl-sci]: Charge Density Wave Hampers Exciton Condensation in 1T-TiSe2. Chao Lian, Zulfikhar A. Ali, Bryan M. Wong. (Submitted on 31 Jan 2019): ABSTRACT: The Bose-Einstein condensation of excitons continues to garner immense attention as a prototypical example for observing emergent properties from many-body quantum effects. In particular, Titanium Diselenide (TiSe2) is a promising candidate for realizing exciton condensation and was experimentally observed only very recently [{this https URL\%2Fscience.aam6432}{Science \textbf{358} 1314 (2017)}]. Surprisingly, the condensate was experimentally characterized by a soft plasmon mode that only exists near the transition temperature, Tc, of the charge density wave (CDW). Here, we characterize and analyze the experimental spectra using linear-response time-dependent density functional theory and find that the soft mode can be attributed to interband electronic transitions. At the CDW state below Tc, the periodic lattice distortions hamper the spontaneous formation of the exciton by introducing a CDW gap. Our surprising results contradict previous simplistic analytical models commonly used in the scientific literature. In addition, we find that a finite electronic temperature, Te, introduces an effective band gap and prevents the condensation above Tc. The band gap lifts the soft mode and merges it into the regular intraband plasmon. The combined effect of the CDW and Te explains the fragile temperature-dependence of the exciton condensation. Taken together, our work provides the first \textit{ab initio} atomic-level framework for rationalizing recent experiments and further manipulating exciton condensates in TiSe2. INTRODUCTION: Bose-Einstein condensates (BECs) exhibit exotic transport phenomena such as superfluity in liquid Helium and superconductivity via Cooper pairs. Other bosonic quasiparticles, such as excitons, polaritons, and magnons can also form a BEC, with exciton condensation particularly drawing immense recent attention. The exciton condensate is predicted to form a superfluid current, which not only is an exotic emergent phenomenon in fundamental quantum research, but also vital for designing next-generation, scatteringfree electronic devices. CONCLUSIONS: Both the CDW and effective band gaps lift the soft mode and merge it into the regular intraband plasmon, which explains why the soft mode is only observed at Tc. As such, our ab initio framework provides critical mechanistic insight into recent exciton condensation experiments and presents additional avenues to experimentalists for further manipulating exciton condensates in
a. TiSe3 b.TiSe2 c. TiSe4 d. TiSe
Q30. arXiv:1901.11243 [nlin.PS]: Interactions of solitons with positive and negative masses: Shuttle motion and co-acceleration. Hidetsugu Sakaguchi, Boris A. Malomed. (Submitted on 31 Jan 2019):ABSTRACT: We consider a possibility to realize self-accelerating motion of interacting states with effective positive and negative masses in the form of pairs of solitons in two-component BEC loaded in an optical-lattice (OL) potential. A crucial role is played by the fact that gap solitons may feature a negative dynamical mass, keeping their mobility in the OL. First, the respective system of coupled Gross-Pitaevskii equations (GPEs) is reduced to a system of equations for envelopes of the lattice wave functions. Two generic dynamical regimes are revealed by simulations of the reduced system, viz., shuttle oscillations of pairs of solitons with positive and negative masses, and splitting of the pair. The co-accelerating motion of the interacting solitons, which keeps constant separation between them, occurs at the boundary between the shuttle motion and splitting. The position of the co-acceleration regime in the system's parameter space can be adjusted with the help of an additional gravity potential, which induces its own acceleration, that may offset the relative acceleration of the two solitons, while gravity masses of both solitons remain positive. The numerical findings are accurately reproduced by a variational approximation. Collisions between shuttling or co-accelerating soliton pairs do not alter the character of the dynamical regime. Finally, regimes of the shuttle motion, co-acceleration, and splitting are corroborated by simulations of the original GPE system, with the explicitly present OL potential. CONCLUSION: The objective of this work is to establish the framework which admits co-accelerating motion of interacting objects with opposite signs of the effective mass, using pairs of matter-wave solitons which move against the background of the OL (optical-lattice) potential. The effective negative mass of one component is provided by the known property of gap solitons. Reducing the full system of the GPEs (Gross-Pitaevskii equations), which includes the OL potential,to equations for slowly varying envelopes, systematic simulations and the VA (variational approximation) reveal two generic dynamical regimes, viz., spontaneous shuttle oscillations of the mean position of the soliton pair, in the course of which the solitons periodically pass through each other, and splitting of the
a. threesome b. pair c. foursum d. matter-wave.
Q31. arXiv:1902.00410 [physics.app-ph]: Light Enhanced Blue Energy Generation using MoS2 Nanopores. Michael Graf, Martina Lihter, Dmitrii Unuchek, Aditya Sarathy, Jean-Pierre Leburton, Andras Kis, Aleksandra Radenovic. (Submitted on 1 Feb 2019) ABSTRACT: Blue energy relies on the chemical potential difference generated between solutions of high and low ionic strength and would provide a sun-and-wind independent energy source at estuaries around the world. Converting this osmotic energy through reverse-electrodialysis relies on ion-selective membranes. A novel generation of these membranes is based on atomically thin MoS2 membranes to decrease the resistance to current flow to increase power output. By modulating the surface charge by light we are able to raise the ion selectivity of the membrane by a factor of 5 while staying at a neutral pH. Furthermore, we find that the behavior of small nanopores is dominated by surface conductance. We introduce a formalism based on the Dukhin number to quantify these effects in the case of a concentration gradient system. As a consequence, the charges created by light illumination provoke two important changes. Increased surface charge at the pore rim enhances the ion selectivity and therefore larger osmotic voltage (dominating in small pores), while the increased surface charge of the overall membrane enhances the surface conductance and therefore the osmotic current (dominating in larger pores). The combination of these effects might be able to efficiently boost the energy generation with arrays of nanopores with varying pore sizes. Introduction: The term blue energy embodies all the attempts to harvest energy coming from the spontaneous and irreversible mixing of sea-water and river-water. The chemical potential difference between two liquids of different salt concentration holds immense amounts of energy: 2.3MJ of theoretical energy is buried in each cubic meter of water. CONCLUSIONS:The continuum PNP model described above is quite useful to investigate electrodiffusion of charged species in ion channels, however there are a few known shortcomings. These include the neglect of finite volume effect of the ionic particles and correlation effects (such as ionion interactions and steric effects). While there have been a few known corrections and modifications to the PNP theory, they have not been considered in our model. Alternately, many other ab-initio methods can also be used to investigate electrodiffusion in narrowly confined ion channels such as Molecular Dynamics (MD), Brownian Dynamics (BD) and Monte-Carlo
a. calculations b. expectations c. simulations d. aspects.
Q32. arXiv:1902.00540 [astro-ph.CO]: New insight into EM radiation from spinning dust and its influence on the Cosmic Microwave Background. Ariel Guerreiro, José Tito Mendonça, Robert Bingham. (Submitted on 1 Feb 2019): ABSTRCT: Dust is ubiquitous in the Universe and its influence on the observed Electromagnetic (EM) radiation needs to be correctly addressed. In recent years it became clear that scattering of EM radiation from interstellar dust grains could change the local properties of the observed Cosmic Microwave Background (CMB) radiation. Here we consider the relevant processes of emission and scattering of EM radiation from spinning dust particles, and discuss their possible influence on the CMB. In particular, we show that scattered radiation can establish a correlation between different spectral components of galactic dipolar emission. This could explain the observed correlation between the CMB and the 100-micron thermal emission form interstellar dust. Another important property of CMB is related with its polarisation anisotropies, and the observation of a cosmological B-mode. We show that scattering of CMB radiation from dust grains in the presence of a static magnetic field could indeed create a B-mode spectral component, which is very similar to that due to primordial gravitational waves. This can be described by a kind of Cotton-Mutton effect on the CMB radiation. INTRODUCTION: Currently, the analysis of the influence of the dust dynamics on the CMB depend on a large degree of extrapolation and modelling of the rotational dynamics of the grains [6]. Of particular importance in the study of CMB are the anisotropies of their fundamental parameters, most notably the temperature and polarisation anisotropies. In the case of the later, the analysis is done in terms of the B and E modes, measured in terms of two Stokes parameters Q and U that are analogous to decomposing a vector field into a gradient part (E) and a divergence free curl part (B). The accurate detection of the B and E mode are extremely important in the understanding of the structure of the early Universe. CONCLUSIONS: This dust induced delensing results from a kind of collective Cotton-Mouton effect, which was described here with the help of a ray-tracing code for the two orthogonal polarization states associated with the magnetized dust gas. The ray-tracing simulations have also shown that, both magnetic field perturbations and dust density modulations can leave an imprint on the polarization pattern of the broad band radiation spectrum. For specific dust density modulation conditions, formation of caustics can take place, which however disappears with propagation. Our results could be useful to the understanding of CMB polarization. The importance of dust in the explanation of the observed B-mode signature was noticed before [8]. Previous models were based on thermal radiation from dust grains. Here we provide an alternative and more specific process, which can be used to explain qualitatively the observed phenomena. This, in a sense, completes the demonstration that dust is the main ingredient leading to the formation of a B-mode on the polarization pattern of the CMB radiation. Specific models of dust grain distributions will have to be establish in order to bring the explanation to more a quantitative accuracy
a. standard b. level c. exponent d. threshold.
Q33.arXiv:1902.00798 [astro-ph.GA]: The role of magnetic field in molecular cloud formation and evolution. Patrick Hennebelle, Shu-ichiro Inutsuka. (Submitted on 2 Feb 2019): ABSTRACT: We review the role that magnetic field may have on the formation and evolution of molecular clouds. After a brief presentation and main assumptions leading to ideal MHD equations, their most important correction, namely the ion-neutral drift is described. The nature of the multi-phase interstellar medium (ISM) and the thermal processes that allows this gas to become denser are presented. Then we discuss our current knowledge of compressible magnetized turbulence, thought to play a fundamental role in the ISM. We also describe what is known regarding the correlation between the magnetic and the density fields. Then the influence that magnetic field may have on the interstellar filaments and the molecular clouds is discussed, notably the role it may have on the prestellar dense cores as well as regarding the formation of stellar clusters. Finally we briefly review its possible effects on the formation of molecular clouds themselves. We argue that given the magnetic intensities that have been measured, it is likely that magnetic field is i) responsible of reducing the star formation rate in dense molecular cloud gas by a factor of a few, ii) strongly shaping the interstellar gas by generating a lot of filaments and reducing the numbers of clumps, cores and stars, although its exact influence remains to be better understood. % by a factor on the order of at least 2. Moreover at small scales, magnetic braking is likely a dominant process that strongly modifies the outcome of the star formation process. Finally, we stress that by inducing the formation of more massive stars, magnetic field could possibly enhance the impact of stellar feedback. INTRODUCTION: The interstellar cycle, which takes place within galaxies, is fundamental for our universe as it controls the formation of stars and therefore the evolution of galaxies. Yet given the broad range of spatial scales and the profusion of physical processes involved, our understanding is still very incomplete. Amongst other processes, namely gravity, compressible turbulence, radiation, cosmic rays and stellar feedback, magnetic field is also contributing significantly to the evolution of the interstellar medium (ISM) and more specifically to the formation of stars. As a matter of evidence, the magnetic energy in the ISM is comparable to the other energies as for example the kinematic one. Deciphering the various roles that magnetic field is playing is however not obvious, i) because measuring it remains a challenge, ii) because magnetic field is not a mere pressure and is highly non-isotropic in nature, iii) because observations do not allow us to easily vary the parameters as it is possible to do in experiments. This however can be done in numerical simulations where the influence of a specific parameter, like the magnetic intensity, can be modified and studied. CONCLUSIONS: While it is now almost certain that magnetic fields do not regulate the star formation process by reducing the star formation rate drastically, as proposed three decades ago, it is likely the case that magnetic fields contribute to reduce it by a factor of a few. Moreover since it has been found by various groups that magnetic field tends to reduce the fragmentation and to produce stars with larger mass, another possible consequence of magnetic field is to enhance stellar feedback and therefore to reduce the star formation rate and efficiency in molecular clouds. This latter aspect remains however to be confirmed as numerical simulations are not able now to cover the necessary range of scales. Finally we stress that magnetic field is likely to have drastic consequences on the formation of protoplanetary disks through magnetic braking by reducing and even possibly controlling their
a. crticallity b. strength c. formation d. size.
Q34. arXiv:1902.01140 [astro-ph.SR]: Variable emission mechanism of a Type IV radio burst. D. E. Morosan, E. K. J. Kilpua, E. P. Carley, C. Monstein. (Submitted on 4 Feb 2019):ABSTRACT: The Sun is an active star and the source of the largest explosions in the solar system, such as flares and coronal mass ejections (CMEs). Flares and CMEs are powerful particle accelerators that can generate radio emission through various emission mechanisms. Aims. CMEs are often accompanied by Type IV radio bursts that are observed as continuum emission in dynamic spectra at decimetric and metric wavelengths, but their emission mechanism can vary from event to event. Here, we aim to determine the emission mechanism of a complex Type IV burst that accompanied the flare and CME on 22 September 2011. Methods. We used radio imaging from the Nançay Radioheliograph, spectroscopic data from the e-Callisto network, ARTEMIS, Ondrejov, and Phoenix3 spectrometers combined with extreme-ultraviolet observations from NASA's Solar Dynamic Observatory to analyse the Type IV radio burst and determine its emission mechanism. Results. We show that the emission mechanism of the Type IV radio burst changes over time. We identified two components in the Type IV radio burst: an earlier stationary Type IV showing gyro-synchrotron behaviour, and a later moving Type IV burst covering the same frequency band. This second component has a coherent emission mechanism. Fundamental plasma emission and the electroncyclotron maser emission are further investigated as possible emission mechanisms for the generation of the moving Type IV burst. Conclusions. Type IV bursts are therefore complex radio bursts, where multiple emission mechanisms can contribute to the generation of the wide-band continuum observed in dynamic spectra. Imaging spectroscopy over a wide frequency band is necessary to determine the emission mechanisms of Type IV bursts that are observed in dynamic spectra. INTRODUCTION: CMEs can also be accompanied by continuum emission at decimetric and metric wavelengths, so-called Type IV radio bursts, which can have either stationary or moving sources and various emission mechanisms. CONCLUSIONS: Our analysis of the Type IV radio burst highlights the necessity of instruments capable of high-frequency and temporal resolution spectroscopy to complement the imaging capabilities of the NRH and instruments capable of imaging above the NRH frequency range.The Expanded Owens Valley Solar Array (EOVSA) is currently capable of such observations, but it is limited to higher frequency ranges of 1–18 GHz. Other instruments are now available at lower frequencies (<300 MHz), such as the Low Frequency Array (LOFAR) and the Murchinson Widefield Array (MWA), but there is still a need to provide imaging spectroscopy with high resolution at frequencies between 400-1000 MHz. These instruments would provide the possibility of answering outstanding questions on the emission mechanisms of TypeIV radio bursts and their potential in estimating CME magnetic fields for space weather
a. purposes b. conditions c. modification d. resolutions.
Q35. arXiv:1811.01078 [gr-qc]: On a soliton-type spacetime defect. F.R. Klinkhamer. (Submitted on 5 Nov 2018 (v1), last revised 4 Feb 2019 (this version, v3)): ABSTRACT: We review the construction of a particular soliton-type solution of the classical Einstein and matter-field equations. This localized finite-energy static classical solution can be interpreted as a single spacetime defect embedded in Minkowski spacetime and may give rise to several new effects. For a Skyrme-type theory with small enough matter-field energy scale compared to the Planck energy scale and for a sufficiently small defect length scale, the existence of a globally regular solution requires a negative active gravitational mass, so that the defect repels a distant test particle ("antigravity"). There also exist "stealth defects" which have a vanishing asymptotic gravitational mass. These stealth defects are, however, not entirely invisible as they bring about a new type of gravitational lensing. INTRODUCTION: One hypothesis is that the Universe started out in some form of “quantum phase” which gave rise to classical spacetime and gravity, as described by Einstein’s General Theory of Relativity. It is then possible that this process is analogous to the cooling of a liquid, which produces an atomic crystal. But, if the cooling of the latter process is rapid, the resulting crystal will be imperfect, containing crystallographic defects. For the above-mentioned quantum phase and the resulting classical spacetime, the analogy suggests the possibility of having “spacetime defects” (i.e., imperfections in the fabric of spacetime). Remark that, historically, some of the earliest ideas on a foam-like structure of spacetime go back to Wheeler in the 1950s.CONCLUSION: The issue of (genuine or effective) topology change is essential for a proper understanding of the small-scale structure of spacetime, which brings us back to the quantum
a. Jump b. relaxation c. phase d. transions
Q36. arXiv:1902.01180 [cond-mat.mes-hall]: Single-photon light emitting diodes based on pre-selected quantum dots using a deterministic lithography technique. Marc Sartison, Simon Seyfferle, Sascha Kolatschek, Stefan Hepp, Michael Jetter, Peter Michler, Simone Luca Portalupi: (Submitted on 4 Feb 2019): ABSTRACT: In the present study, we developed a fabrication process of an electrically driven single-photon LED based on InP QDs emitting in the red spectral range, the wavelength of interest coinciding with the high efficiency window of Si APDs. A deterministic lithography technique allowed for the pre-selection of a suitable QD, here exclusively operated under electrical carrier injection. The final device was characterized under micro-electroluminescence in direct current, as well as in pulsed excitation mode. In particular, under pulsed excitation of one device, single-photon emission of a spectral line, identified as an exciton, has been observed with g(2)raw (0)=0.42±0.02 where the non-zero g(2) -value is mainly caused by background contribution in the spectrum and re-excitation processes due to the electrical pulse length. The obtained results constitute an important step forward in the fabrication of electrically driven single-photon sources, where deterministic lithography techniques can be used to sensibly improve the device performances. In principle, the developed process can be extended to any desired emitter wavelength above 600nm up to the telecom bands. In conclusion, we realized a QD-based single-photon LED, operating at the absolute efficiency maximum of Si APDs, via an optimized deterministic fabrication technique. QDs were here pre-selected in µ-EL and the device was fabricated via state-of-the-art low temperature in-situ lithography and standard clean room fabrication techniques. The successful deterministic integration of QDs could be verified by the acquisition of µ-EL maps combined with reflectivity maps. Furthermore, the device performances were characterized under pulsed electrical excitation by means of EL polarization dependence, time-resolved EL decay time and photon-autocorrelation measurements. A decay time of 599ps under triggered electrical excitation compares well with already reported values for InP QDs in literature. Additionally, a g(2) dcc(0) value of 0.41±0.03 could be recorded, only corrected for the detector induced dark count contribution, thus indicating dominant single-photon emission. By accounting also for the spectral background contribution, a corrected g(2)bgc(0) value of 0.23±0.05 could be estimated. The deterministic fabrication process of SPLEDs developed in this work can be applied to any electrically driven emitter from the red spectral range up to the telecom regimes. The proof of principle measurements presented here show the possibility of combining in-situ optical lithography with electrically driven non-classical light sources. It enables the route towards electrically driven cavity systems and high brightness devices. Improving the performances of single QD devices via deterministic lithography techniques will be of key importance in a range of quantum technology implementations, from quantum distribution to quantum enhanced
a. metrology b. meteorology c. light-source d. emission.
Q37. arXiv:1902.01409 [astro-ph.GA]: The Physical Nature of Neutral Hydrogen Intensity Structure. S.E. Clark, J.E.G. Peek, M.-A. Miville-Deschênes. (Submitted on 4 Feb 2019). ABSTRACT: We investigate the physical properties of structures seen in channel map observations of 21-cm neutral hydrogen (HI) emission. HI intensity maps display prominent linear structures that are well aligned with the ambient magnetic field in the diffuse ISM. Some literature holds that these structures are "velocity caustics", fluctuations imprinted by the turbulent velocity field, and are not three-dimensional density structures in the interstellar medium. We test this hypothesis by stacking probes of the density field -- broadband far infrared (FIR) emission and the integrated HI column density (NHI) -- at the locations of linear HI intensity structures. We find that the HI intensity features are real density structures and not velocity caustics. We generalize the investigation to all small-scale structure in HI channel maps, and analyze this correlation as a function of velocity channel width, finding no measurable contribution from velocity caustics to the HI channel map emission. Further, we find that small-scale HI channel maps structures have elevated FIR/NHI, implying that this emission originates from a colder, denser phase of the ISM than the surrounding material. The data are consistent with a multi-phase diffuse ISM in which small-scale structures in narrow HI channel maps are preferentially cold neutral medium (CNM) that is anisotropically distributed and aligned with the local magnetic field. The shallow spatial power spectrum of narrow HI channels is often attributed to velocity caustics. We conjecture instead that the small-scale structure and narrow linewidths typical of CNM explain the observed relationship between the spatial power spectrum and channel width. DETAILS: The diffuse interstellar medium (ISM) fills most of the volume of the Milky Way. This material, the progenitor of dense structures that eventually form stars, is multiphase, magnetized, and turbulent. The ISM is broadly partitioned into ionized, molecular, and atomic components, with the atomic gas composed of a cold neutral medium (CNM), warm neutral medium (WNM), and a thermally unstable component. Understanding the distribution of matter and energy within and between these phases is a major goal of ISM research. CONCLUSIONS: Software: astropy (Astropy Collaboration etal. 2013, 2018), cmocean (Thyng et al. 2016), matplotlib (Hunter 2007), numpy (Oliphant 2015). A shallower spatial power spectrum slope measured in narrower velocity channels is qualitatively consistent with a higher contribution to the intensity in narrow channels from CNM gas. Previous work has attributed such a change in the spatial power spectrum to velocity fluctuations, and used this to derive the slope of the turbulent velocity power spectrum in the gas. This work calls those analyses into question. This work calls for a significant reassessment of many observational and theoretical studies of turbulence in
a. He b. Hi c. Hydrogen d. Helium.
Q38. arXiv:1902.01440 [astro-ph.GA]: Radio Source Extraction with ProFound. C. L. Hale, A. S. G. Robotham, L. J. M. Davies, M. J. Jarvis, S. P. Driver, I. Heywood. (Submitted on 4 Feb 2019). ABSTRACT: In the current era of radio astronomy, continuum surveys observe a multitude of objects with complex morphologies and sizes, and are not limited to observing point sources. Typical radio source extraction software generates catalogues by using Gaussian components to form a model of the emission. This may not be well suited to complicated jet structures and extended emission, particularly in the era of interferometers with a high density of short baselines, that are sensitive to extended emission. In this paper, we investigate how the optically-motivated source detection package ProFound (Robotham et al. 2018) may be used to model radio emission of both complicated and point-like radio sources. We use a combination of observations and simulations to investigate how ProFound compares to other source extractor packages used for radio surveys. We find that ProFound can accurately recover both the flux densities of simulated Gaussian sources as well as extended radio galaxies. ProFound can create models that trace the complicated nature of these extended galaxies, which we show is not necessarily the case with other source extraction software. Our work suggests that our knowledge of the emission from extended radio objects may be both over or under-estimated using traditional software. We suggest that ProFound offers a useful alternative to the fitting of Gaussian components for generating catalogues from current and future radio surveys. Furthermore, ProFound's multi-wavelength capabilities will be useful in investigating radio sources in combination with multi-wavelength data. DETAILS: Modern radio surveys are able to combine deep and widearea observations of the sky with greater ease than ever before. CONCLUSIONS: We therefore feel that ProFound may be a beneficial source extraction software for both current as well as the future radio surveys that we expect to complete at higher angular resolutions and greater depths. Not only this, but as ProFound is designed to be used within a multi-wavelength framework. This can therefore be used to generate consistent flux extraction of sources across the electromagnetic spectrum. This is by using segments defined by ProFound at one wavelength to calculate fluxes at another. This will be useful for not only obtaining consistently extracted fluxes at different radio frequencies but can also be important in making use of observations across the electromagnetic spectrum. This is advantageous in the era of multi-wavelength
a. frame-work b. data c. astronomy d. astrophysics.
Q39. arXiv:1902.01675 [astro-ph.GA]: The mass, location and heating of the dust in the Cassiopeia A supernova remnant. F. D. Priestley, M. J. Barlow, I. De Looze. (Submitted on 5 Feb 2019): ABSTRACT: We model the thermal dust emission from dust grains heated by synchrotron radiation and by particle collisions, under conditions appropriate for four different shocked and unshocked gas components of the Cassiopeia A (Cas A) supernova remnant (SNR). By fitting the resulting spectral energy distributions (SEDs) to the observed SNR dust fluxes, we determine the required mass of dust in each component. We find the observed SED can be reproduced by ∼0.6 M⊙ of silicate grains, the majority of which is in the unshocked ejecta and heated by the synchrotron radiation field. Warmer dust, located in the X-ray emitting reverse shock and blastwave regions, contribute to the shorter wavelength infrared emission but make only a small fraction of the total dust mass. Carbon grains can at most make up ∼25% of the total dust mass. Combined with estimates for the gas masses, we obtain dust-to-gas mass ratios for each component, which suggest that the condensation efficiency in the ejecta is high, and that dust in the shocked ejecta clumps is well protected from destruction by sputtering in the reverse shock. DETAILS: Previous modelling of the Cas A dust emission has been based on fitting the spectral energy distribution (SED) with some number of temperature components for a given dust composition (i.e. ‘hot’ and ‘cold’ dust). This assumes all dust grains radiate at the same temperature for each component, but grains of different sizes will in general have different equilibrium temperatures for the same heating source. Additionally, smaller grains can undergo large temperature fluctuations. CONCLUSIONS: This is consistent with dust grains being efficiently sputtered at high temperatures, whereas in the ejecta clumps which have passed through the reverse shock, the dust is more resilient to destruction. Magnesium silicate grains, with possible iron inclusions, are found to reproduce almost all of the observed Cas A dust spectrum, with a relatively minor amount of another species (FeO, SiO2 or Mg0.7SiO2.7) required to reproduce the 21µm emission peak. While carbon grains may be present, they cannot make up a large fraction of the dust mass in the X-ray emitting gas (< 25%) without predicting NIR fluxes in excess of those observed. If the mass fractions do not vary significantly between the shocked and unshocked ejecta, carbon dust can be ruled out as a major constituent of the ejecta dust. The unshocked and clumped ejecta dust, making up the majority of the mass, is heated mostly by the remnant’s synchrotron radiation field, while the diffuse and blastwave dust, which dominates the total SED luminosity, is heated by collisions with electrons and nuclei. The total dust mass in Cas A is consistent with CCSNe being significant contributors to the dust in high-redshift galaxies, particularly if much of it is present in clumps which survive the passage of the reverse shock without
a. disruption b. destruction c. resolution d. prediction.
Q40. arXiv:1902.01550 [cond-mat.mes-hall]: Coherent spin control of s-, p-, d- and f-electrons in a silicon quantum dot. R. C. C. Leon, C. H. Yang, J. C. C. Hwang, J. Camirand Lemyre, T. Tanttu, W. Huang, K. W. Chan, K. Y. Tan, F. E. Hudson, K. M. Itoh, A. Morello, A. Laucht, M. Pioro-Ladriere, A. Saraiva, A. S. Dzurak. (Submitted on 5 Feb 2019): ABSTRACT: Once the periodic properties of atoms were unveiled, chemical bonds could be understood in terms of the valence of atoms. Ideally, this rationale would extend to quantum dots, and quantum computation would be performed by merely controlling electrons in the outer shell. Imperfections in the semiconductor material, even at the atomic scale, disrupt this analogy between atoms and quantum dots, so that real devices seldom display such intelligible many-electron arrangement. We demonstrate here an electrostatic quantum dot that overcomes the hardships of disorder and reveals a well defined shell structure. We observe four shells (31 electrons) with multiplicities given by spin and valley degrees of freedom. We explore various fillings consisting of a single valence electron -- namely 1, 5, 13 and 25 electrons -- as potential qubits. An integrated micromagnet allows us to perform electrically driven spin resonance (EDSR). Higher shell states are shown to be more susceptible to the driving field, leading to faster Rabi rotations of the qubit. We investigate the impact of orbital excitations of the p and d-shell electrons on single qubits as a function of the dot deformation. This allows us to tune the dot excitation spectrum and exploit it for faster qubit control. Furthermore, hotspots arising from this tunable energy level structure provide a pathway towards fast spin initialisation. DETAILS:We demonstrate here an electrostatic quantum dot that overcomes the hardships of disorder and reveals a well defined shell structure. We observe four shells (31 electrons) with multiplicities given by spin and valley degrees of freedom3,4,7. We explore various fillings consisting of a single valence electron – namely 1, 5, 13 and 25 electrons – as potential qubits. CONCLUSIONS: The present work experimentally demonstrates that purely spin-based qubits may be implemented in multielectron quantum dots. This could be a desirable feature as long as the shell structure is well preserved, such as in very small SiMOS electrostatic quantum dots. Operation based on EDSR takes advantage of the extended wavefunction to drive the qubit with higher control fidelity and longer distance J coupling between qubits. A multielectron system results in a richer many-body excitation spectrum, which could have higher Rabi frequencies for fast qubit gates and enhanced relaxation rates for quick qubit initialization. We anticipate the possibility of complex two qubit physics, with a possible singlettriplet inversion, mimicking the physics of paramagnetic bonding. This would require a revision of the two qubits gate strategies, as well as the spin-to-charge conversion techniques for qubit
a. In-read b. contacts c. dots d. read-out.
Q41.arXiv:1902.02474 [hep-ph]: Isoscalar and isovector kaon form factors from e + e − and τ data. K.I. Beloborodov, V.P. Druzhinin, S.I. Serednyakov. (Submitted on 7 Feb 2019): ABSTRACT: The recent precise measurements of the e+ e−→KSKL and e+ e− → K+ K−cross sections and the hadronic spectral function of the τ−→K−KS ντ decay are used to extract the isoscalar and isovector electromagnetic kaon form factors and their relative phase in a model independent way. The experimental results are compared with a fit based on the vector-meson-dominance model. INTRODUCTION: Kaon electromagnetic form factors are the key objects in hadron physics describing electromagnetic interaction of kaons and providing important information about their internal structure. In conclusion, we have used recent precise measurements of the e+ e− → K ¯ K cross sections and the K−KS spectrum in the τ− → K−KS ντ decay to separate the isoscalar and isovector electromagnetic kaon form factors and determine the relative phase between them in a model independent way. The latter shows an unexpected energy dependence in the energy range from 1.06 to 1.5 GeV. It is almost constant and close to zero. We have simultaneously fitted to the e+e− → K+K− and e+e− → KSKL cross-section data and the hadronic mass spectrum in the τ− → K−KS ντ decay in the framework of the VMD model. The fit reproduces data reasonably well and shows that the CVC hypothesis for the K ¯ K system works with a few percent accuracy. To explain the specific energy dependence of the relative phase between the isoscalar and isovector form factors the large difference between parameters cρ' and cω' is required, which contradicts to the quark model expectation
a. cρ' = cω' b. cρ' differs cω' c. cρ' = cω'. d. cρ' not equal cω'.
Q42. arXiv:1902.02691 [hep-ph]: The symmetry of 4×4 mass matrices predicted by the spin-charge-family theory --- SU(2)×SU(2)×U(1) --- remains in all loop corrections. A. Hernandez-Galeana, N.S. Mankoc Borstnik. (Submitted on 8 Jan 2019): ABSTRACT: The spin-charge-family theory predicts the existence of the fourth family to the observed three. The 4×4 mass matrice, determined by the nonzero vacuum expectation values of the two triplet scalars, the gauge fields of the two groups of SU˜(2) determining family quantum numbers, and by the contributions of the dynamical fields of the two scalar triplets and the three scalar singlets with the family members quantum numbers ( τα = (Q, Q′ , Y′ ) ) --- manifest the symmetry SU˜(2)×SU˜(2)×U(1) . All scalars carry the weak and the hyper charge of the standard model higgs field ( ± 1/2, ∓1/2, respectively). It is demonstrated, using the massless spinor basis, that the symmetry of the 4×4 mass matrices remains SU(2)×SU(2)×U(1) in all loop corrections, and it is discussed under which conditions this symmetry is kept under all corrections, that is with the corrections induced by the repetition of the nonzero vacuum expectation values included. CONCLUSION: After the electroweak phase transition, caused by the scalar fields with the space index, the two groups of four families become massive. The lowest of the two groups of four families contains the observed three, while the fourth remains to be measured. The lowest of the upper four families is the candidate for the dark
a. space b. matter c. matrices d. fields
Q43. arXiv:1902.02373 [astro-ph.GA]: A Near Infrared View of Nearby Galaxies: The Case of NGC 6300. Gaia Gaspar, Rubén Díaz, Damián Mast, Ary D'Ambra, María Paz Agüero, Guillermo Günthardt. (Submitted on 6 Feb 2019): ABSTRACT: We present a near-infrared study of the Seyfert 2 galaxy NGC6300, based on subarcsecond images and long slit spectroscopy obtained with Flamingos-2 at Gemini South. We have found that the peak of the nuclear continuum emission in the Ks band and the surrounding nuclear disk are 25pc off-center with respect to the center of symmetry of the larger scale circumnuclear disk, suggesting that this black hole is still not fixed in the galaxy potential well. The molecular gas radial velocity curve yields a central black hole upper mass estimation of M_{SMBH}^{upper}=(6+ or - 2)x10^{7} Msun. The Paβ emission line has a strongly asymmetric profile with a blueshifted broad component that we associate with a nuclear ionized gas outflow. We have found in the Ks -band spectra that the slope of the continuum becomes steeper with increasing radii, which can be explained as the presence of large amounts of hot dust not only in the nucleus but also in the circumnuclear region up to r=27pc. In fact, the nuclear red excess obtained after subtracting the stellar contribution resembles to that of a blackbody with temperatures around 1200K. This evidence supports the idea that absorbing material located around the nucleus, but not close enough to be the torus of the unified model, could be responsible for at least part of the nuclear obscuration in this Seyfert 2 nucleus. DETAILS:Active Galactic Nuclei are among the most intriguing objects because they are present throughout most of the universe’s history, meaning they must be an essential ingredient in the galactic and cosmic evolution, yet there are several aspects that are still not completely understood. The near-infrared (NIR) bands offer the advantage of lowering the galactic extinction both in the Milky Way and in the host galaxy, reaching 10% of the V-band extinction in the Ks band. This allows NIR photons to escape easily and provides a more detailed view of the structure and physical state of the circumnuclear regions. At the same time, more energetic photons absorbed by dust are re-emitted in the infrared allowing us to map the most dusty regions. In particular, in the K band is possible to observe a red excess associated with hot dust in the nuclear regions. NIR also has the advantage of being observable from the ground and now we count with several facilities optimized for imaging and spectroscopy in the NIR bands. CONCLUSIONS: The results presented in this work provide different elements that help to understand the way in which an obscured AGN of intermediate-low mass grows its mass in the presence of a weak bar and with large amounts of circumnuclear dust. But there are many questions that arise and require a systematic study in a statistically significant sample. What is the relationship between nuclear feeding mechanisms in Seyfert galaxies and the strength of the bar? How the appearance of the circum nuclear ring, the growth of the SMBH, the AGN duty cycle, and the life cycle of the barall linked? And finally, how does the distribution of circum nuclear dust influence the Seyfert1/Seyfert2 classification? All this places obscured AGN as the most appropriate objects to deepen those aspects of the Unified Model that are still under strong
a. debate b. doubt c. expectation d. influence.
Q44. arXiv:1902.03106 [gr-qc]: A hydrodynamic approach to the classical ideal gas. Bartolomé Coll, Joan Josep Ferrando, Juan Antonio Sáez. (Submitted on 8 Feb 2019): ABSTRACT: The necessary and sufficient condition for a conservative perfect fluid energy tensor to be the energetic evolution of a classical ideal gas is obtained. This condition forces the square of the speed of sound to have the form c^2s=γp / ρ+p in terms of the hydrodynamic quantities, energy density ρ and pressure p, γ being the (constant) adiabatic index. The {\em inverse problem} for this case is also solved, that is, the determination of all the fluids whose evolutions are represented by a conservative energy tensor endowed with the above expression of c^2s , and it shows that these fluids are, and only are, those fulfilling a Poisson law. The relativistic compressibility conditions for the classical ideal gases and the Poisson gases are analyzed in depth and the values for the adiabatic index γ for which the compressibility conditions hold in physically relevant ranges of the hydrodynamic quantities ρ,p are obtained. Some scenarios that model isothermal or isentropic evolutions of a classical ideal gas are revisited, and preliminary results are presented in applying our hydrodynamic approach to looking for perfect fluid solutions that model the evolution of a classical ideal gas or of a Poisson gas. DETAILS: In the relativistic framework, a perfect fluid is usually assumed to be a perfect energy tensor, T ≡ (ρ + p)u ⊗ u+pg, solution to the conservation equations ∇·T = 0. It can model a test fluid in any given space-time, or the source of a solution of the Einstein field equations G = kT. Nevertheless, complementary physical requirements on the hydrodynamic quantities (the unit velocity u, the energy density ρ, and the pressure p) must be imposed for T to represent the energetic evolution of a realistic thermodynamic fluid in local thermal equilibrium.CONCLUSIONS: For a family of perfect fluid solutions of the Einstein field equations with perfect energy tensor T ≡ (u,ρ,p), our method consist in the following steps. In a first step we impose the generic hydrodynamic constraint and obtain the indicatrix function χ = χ(ρ,p) for the subfamily that verifies it. In a second step we detect the subfamily with an ideal gas indicatrix by imposing χ = χ(π) not equal to π. Finally, in a third step, when this function does not coincide with the CIG indicatrix for any value of the involved parameters, we can look for solutions that approximates a
a. front b. background c. matter d. possibility
Q65.arXiv:1905.10717 [astro-ph.HE]: Black Hole Spin Signature in the Black Hole Shadow of M87 in the Flaring State. Tomohisa Kawashima, Motoki Kino, Kazunori Akiyama. (Submitted on 26 May 2019): ABSTRACT: Imaging the immediate vicinity of supermassive black holes (SMBH) and extracting a BH-spin signature is one of the grand challenges in astrophysics. M87 is known as one of the best targets for imaging the BH shadow and it can be partially thick against synchrotron self-absorption (SSA), particularly in a flaring state with high mass accretion rate. However, little is known about influences of the SSA-thick region on BH shadow images. Here we investigate BH shadow images of M87 at 230 GHz properly taking into account the SSA-thick region. When the BH has a high spin value, the corresponding BH shadow image shows the positional offset between the centre of the photon ring and that of the SSA-thick ring at the innermost stable circular orbit (ISCO) due to the frame-dragging effect in the Kerr spacetime. As a result, we find that a dark-crescent structure is generally produced between the photon ring and the SSA-thick ISCO ring in the BH shadow image. The scale size of the dark-crescent increase with BH spin: its width reaches up to ∼2 gravitational radius when the BH spin is 99.8% of its maximum value. The dark crescent is regarded as a new signature of a highly spinning BH. This feature is expected to appear in flaring states with relatively high mass accretion rate rather than the quiescent states. We have simulated the image reconstruction of our theoretical image by assuming the current and future Event Horizon Telescope (EHT) array, and have found that the future EHT including space-very long baseline interferometry in 2020s can detect the dark crescent. CONCLUSIONS: We emphasize the importance of 350 GHz VLBI observations in the future, because the width of the dark crescent is larger at 350 GHz due to the decrease of the optical depth for SSA, which results in the more robust detectability of the dark crescent in future EHT observation. Toward realizing the transcontinental VLBI at 350 GHz, the 12 m diameter radio telescope is now almost deployed to the Summit Station in Greenland. The telescope (Greenland Telescope, GLT) is to become one of the VLBI stations at 350 GHz, providing the longest baseline, longer than 9000 km to achieve an exceptional angular resolution of 20 µas, and we will be able to conduct observations at event horizon angular
a. crescent b. image c. resolution d. departure.
Q66. arXiv:1905.11149 [astro-ph.HE]: The self-control of Cosmic Rays. Pasquale Blasi (GSSI). (Submitted on 27 May 2019): ABSTRACT: Several independent pieces of information have recently hinted at a prominent role of cosmic rays in controlling their own transport, within and around the sources as well as throughout their propagation on Galactic scales and even possibly during their escape from the Galaxy. I will discuss this topic with special attention to the theoretical implications and possible additional observational evidence that we may seek with upcoming experiments. Introduction The bulk of cosmic rays (CRs) is made of fully ionized light nuclei, moving at speeds close to the speed of light. In all cases of astrophysical interest, these particles propagate diffusively through magnetized media, with the possible exception of CRs at the highest energies, which might propagate quasi-ballistically. The diffusive ansatz seems appropriate to both acceleration regions and transport through the Galaxy. Yet, many aspects of this ansatz are somewhat less clear than one would think. CONCLUSION: This chain of events causes CRs to be advected away from our Galaxy and to develop an over density in a region of the order of a few galactic disc radii, several tens of kpc. In this region the occasional interactions of accumulated CRs with the gas in the circum-galactic medium leads to the production of neutrinos (through the decay of charged pions) and gamma rays (through the decay of neutral pions). The neutrino flux compares well with the observations of IceCube, provided there is an over density of∼100−200 in the gas, compatible with what is expected inside the virial radius of a structure such as our Galaxy. Interestingly, a diffuse gamma ray emission has recently been measured by Fermi-LAT from a large region around the Andromeda
a. cluster of stars b. transport c. complex d. galaxy.
Q67. arXiv:1905.11429 [astro-ph.GA]: Discovery of nine new stellar groups in the Orion complex. Boquan Chen, Elena D'Onghia, João Alves, Angela Adamo. (Submitted on 27 May 2019):ABSTRACT: We use two unsupervised machine learning algorithms, Shared Nearest Neighbor (SNN) and \textit{EnLink}, as a single approach to identify stellar groupings in the Orion star-forming complex as an application to the 5-dimensional astrometric data from Gaia DR2. The algorithms present two different ways to limit user bias when evaluating the relative weights among the astrometric parameters, automatically determined by the machine and through a standard procedure by monitoring several outcome measures. Both algorithms complement each other and produce similar stellar groups. Because SNN groups have a much smaller spread in proper motions compared to \textit{EnLink}, we use \textit{EnLink}, which requires no input, as a first pass tool for group identification and validation. We then used the SNN algorithm to dissect the Orion star-forming complex. We identify 21 spatially- and kinematically-coherent groups in the Orion complex, nine of which previously unknown. The groups show a wide distribution of distances extending as far as about 150 pc in front of the star-forming Orion clouds, to about 50 pc beyond them where we find, unexpectedly, three groups. Our results expose to view the wealth of sub-structure in the OB association, within and beyond the classical Blaauw Orion OBI sub-groups. A full characterization of the new groups is of the essence as it offers the potential to unveil how star formation proceeds globally in large complexes such as Orion. The data and code that generated the groups is provided in this Letter. DETAILS: An obvious target to disentangle young populations leaving their natal gas is the Orion complex, the closest massive star forming region to Earth. CONCLUSIONS: The analysis in this work should be repeated including the sixth dimension, radial velocity. We expect radial velocity to be available for more stars in the Orion complex from Gaia DR3 or ongoing GALAH observations. The addition of radial velocity will allow us to produce stellar groups consistent in 6d phase space and study the kinematics of these groups. GaiaDR3 will provide more precise parallaxes and proper motions, which would further improve clustering results. For now, a full characterization of the new groups is of the essence as it offers the potential to unveil how star formation proceeds globally in large complexes such as
a. analysis b. observations c. subsystem d. whole universe.
Q82. arXiv:1906.02712 [astro-ph.GA]: Dust properties and star formation of about a thousand local galaxies. Sophia Lianou, Pauline Barmby, Aleksandr Mosenkov, Matthew Lehnert, Oskar Karczewski. (Submitted on 6 Jun 2019): ABSTRACT: We derive the dust properties for 753 local galaxies and examine how these relate to some of their physical properties. We model their global dust-SEDs, treated statistically as an ensemble within a hierarchical Bayesian dust-SED modeling approach. The model-derived properties are the dust masses (Mdust), the average interstellar radiation field intensities (Uav), the mass fraction of very small dust grains ('QPAH' fraction), as well as their standard deviations. In addition, we use mid-IR observations to derive SFR and Mstar, quantities independent of the modeling. We derive distribution functions of the properties for the galaxy ensemble and per galaxy type. The mean value of Mdust for the ETGs is lower than that for the LTGs and IRs, despite ETGs and LTGs having Mstar spanning across the whole range observed. The Uav and 'QPAH' fraction show no difference among different galaxy types. When fixing Uav to the Galactic value, the derived 'QPAH' fraction varies across the Galactic value (0.071). The sSFR increases with galaxy type, while this is not the case for the dust-sSFR (=SFR/Mdust), showing an almost constant SFE per galaxy type. The galaxy sample is characterised by a tight relation between Mdust and Mstar for the LTGs and Irs, while ETGs scatter around this relation and tend towards smaller Mdust. While the relation indicates that Mdust may fundamentally be linked to Mstar, metallicity and Uav are the second parameter driving the scatter, which we investigate in a forthcoming work. We use the extended KS law to estimate Mgas and the GDR. The Mgas derived from the extended KS law is on average ~20% higher than that derived from the KS law, and a large standard deviation indicates the importance of the average SF present to regulate star formation and gas supply. The average GDR for the LTGs and IRs is 370, while including the ETGs gives an average of 550. INTRODUCTION: For the 753 galaxies considered here, the median number of bands used in the SED modelling is twelve. The minimum number of bands used is four (in only one galaxy, NGC4636) and the maximum number of bands used is seventeen, i.e. the maximum possible (for four galaxies: NGC3256, NGC3982, NGC6946, UGC12160), while another three galaxies have only six bands (PGC029653; NGC2974; ESO411013). There are 740 galaxies with WISE22µm observations, and 99 galaxies with Spitzer IRAC8µm observations. We have included the Spitzer IRAC8µm due to the unique constraint to the mid-IR part of the dust-SED it provides. Dust grains are characterised by their chemical composition, size distribution, shape, and abundances (Savage & Mathis 1979; Zubko et al. 2004; Draine 2009). The main principle of the THEMIS model is that dust evolves in response to the physical conditions of its local environment and is not characterised by the same properties everywhere; therefore, dust has different chemical composition, structure, shape, according to the physical conditions exposed, which in turn affects its optical properties (Jones et al. 2017). The THEMIS model is built, as much as possible, upon laboratory measurements of dust material analogues to the interstellar dust, and modifications necessary to provide better fits to the observed interstellar dust properties have been made (Jones et al. 2013). The dust grain composition in the THEMIS model is a mixture of amorphous silicates, with iron and iron-sulphide nano-inclusions, and hydrogenated amorphous carbon materials (a-C(:H)). A mass element of the ISM is assumed to be illuminated by a non-uniform interstellar radiation field. The latter is described by a heating intensity U, with U=1 corresponding to the intensity of the solar neighbourhood, U=2.2×10^−5 Wm^−2. Then, the distribution of the dust masses per unit heating intensity is described by the power law over heating intensities: dMdust/dU∝U^−α, with Umin < U < Umin + ∆U. Integrating the above expression between Umin to Umin + ∆U results in the total dust mass, Mdust,for the assumed mass element. CONCLUSIONS: We emphasise that the strength of our results rely both on one of the largest galaxy samples in the local Universe with imaging treated homogeneously and on the statistical constraints posed on the properties of the galaxy sample modelled as an ensemble with a hierarchical Bayesian dust-SED model. These two elements make this study unique. As a follow up to what is presented here, we perform small physical scale analyses of as many galaxies as permitted (spatialconstraints), so as to be able to understand the local variations of the dust properties versus the star formation
a. story b. incidence c. model d. history.
Q83. arXiv:1906.02221 [astro-ph.HE]: Probing high-energy interactions of atmospheric and astrophysical neutrinos. Spencer R. Klein. (Submitted on 5 Jun 2019):ABSTRACT: Astrophysical and atmospheric neutrinos are important probes of the powerful accelerators that produce cosmic-rays with EeV energies. Understanding these accelerators is a key goal of neutrino observatories, along with searches for neutrinos from supernovae, from dark matter annihilation, and other astrophysics topics. Here, we discuss how neutrino observatories like IceCube and future facilities like KM3NeT and IceCube-Gen2 can study the properties of high-energy (above 1 TeV) neutrino interactions. This is far higher than is accessible at man-made accelerators, where the highest energy neutrino beam reached only 500 GeV. In contrast, neutrino observatories have observed events with energies above 5 PeV - 10,000 times higher in energy - and future large observatories may probe neutrinos with energies up to 10^20 eV. These data have implications for both Standard Model measurements, such as of low Bjorken −x parton distributions and gluon shadowing, and also for searches for beyond Standard Model physics. This chapter will review the existing techniques and results, and discuss future prospects. INTRODUCTION: The observed neutrino flux in neutrino telescopes includes contributions from conventional atmospheric neutrinos, prompt atmospheric neutrinos and an astrophysical flux. Conventional atmospheric neutrinos come from the decay of π±, K± and K0 produced in cosmic-ray air showers, while prompt atmospheric neutrinos arise from the decays of similarly produced charmed hadrons. CONCLUSIONS: Neutrino telescopes offer an opportunity to study neutrino physics at energies up to a few PeV, many orders of magnitude higher than are available at accelerators. Studies have been made of both the neutrino cross-sections, and also the final states produced, specifically the neutrino inelasticity distribution. These measurements are sensitive to many aspects of standard-model neutrino physics, and are also sensitive to some beyond standard-model physics. Future measurements with radio-Cherenov detectors should reach energies above 10^17 eV, enough to probe new physics at energies beyond those accessible at the LHC. Although the energy reach is impressive, the limited neutrino flux and large detector granularity limit the precision of current measurements. However, they are our only probe of neutrino energies above 1 TeV, and provide a useful new window for neutrino physics reaching up to and beyond LHC energies.
a. limits b. energies c. flux d. detectors.
Q84.arXiv:1906.05878 [astro-ph.HE]: Fast Radio Bursts: An Extragalactic Enigma. James M. Cordes, Shami Chatterjee. (Submitted on 13 Jun 2019): ABSTRACT: We summarize our understanding of millisecond radio bursts from an extragalactic population of sources. FRBs occur at an extraordinary rate, thousands per day over the entire sky with radiation energy densities at the source about ten billion times larger than those from Galactic pulsars. We survey FRB phenomenology, source models and host galaxies, coherent radiation models, and the role of plasma propagation effects in burst detection. The FRB field is guaranteed to be exciting: new telescopes will expand the sample from the current ∼80 unique burst sources (and a few secure localizations and redshifts) to thousands, with burst localizations that enable host-galaxy redshifts emerging directly from interferometric surveys. * FRBs are now established as an extragalactic phenomenon. * Only a few sources are known to repeat. Despite the failure to redetect other FRBs, they are not inconsistent with all being repeaters. * FRB sources may be new, exotic kinds of objects or known types in extreme circumstances. Many inventive models exist, ranging from alien spacecraft to cosmic strings but those concerning compact objects and supermassive black holes have gained the most attention. A rapidly rotating magnetar is a promising explanation for FRB 121102 along with the persistent source associated with it, but alternative source models are not ruled out for it or other FRBs. * FRBs are powerful tracers of circumsource environments, `missing baryons' in the IGM, and dark matter. * The relative contributions of host galaxies and the IGM to propagation effects have yet to be disentangled, so dispersion measure distances have large uncertainties. INTRODUCTION: Fast radio bursts (FRBs) are millisecond-duration pulses that originate from as-yet unidentified extragalactic sources. They are similar in some respects to pulses from Galactic radio pulsars, but the flux density is of order ten billion times larger and their spectra are radically different from most pulsar spectra and most other radio sources. CONCLUSIONS: The detection of rare weak bursts in massive volumes of survey data is a difficult problem, made more challenging by the steadily worsening radio frequency interference (RFI) environment. Machine learning techniques have been proposed and have already demonstrated dramatic results, and crossdisciplinary collaboration will continue to bear fruit. Manifestation of the cosmologically nearby FRB population is probably limited by the low burst rate per source, but sufficient dwell times on galaxy clusters may provide detections of nearby galaxies that are easier to characterize than more distant ones. If our Galaxy (or a neighboring one) hosts an FRB source, we might experience rare but extraordinarily bright bursts with (relatively) low pulse DM. Such bursts would be difficult to distinguish from RFI, but may be detectable with all-sky dipole antennas or as a citizen science project using mobile phone
a. noise b. emission c. spread d. regions.
Q92. arXiv:1906.07197 [astro-ph.GA]: Lyα Halos Around z∼6 Quasars: Alyssa B. Drake, Emanuele Paolo Farina, Marcel Neeleman, Fabian Walter, Bram Venemans, Eduardo Banados, Chiara Mazzucchelli, Roberto Decarli. (Submitted on 17 Jun 2019): ABSTRACT: We present deep MUSE observations of five quasars within the first Gyr of the Universe (z≳6 ), four of which display extended Lyα halos. After PSF-subtraction, we reveal halos surrounding two quasars for the first time, as well as confirming the presence of two more halos for which tentative detections exist in long-slit spectroscopic observations and narrow-band imaging. The four Lyα halos presented here are diverse in morphology and size, they each display spatial asymmetry, and none are centred on the position of the quasar. Spectra of the diffuse halos demonstrate that none are dramatically offset in velocity from the systemic redshift of the quasars (Δ v <200kms^−1), however each halo shows a broad Lyα line, with a velocity width of order ∼1000kms^−1. Total Lyα luminosities range between ∼2×10^43erg s^−1 and ∼2× 10^44 erg s^−1, reaching maximum radial extents of 13−30pkpc from the quasar positions. We find larger sizes and higher Lyα luminosities than previous literature results at this redshift, but find no correlation between the quasar properties and the Lyα halo, suggesting that the detected emission is most closely related to the physical properties of the circum-galactic medium. INTRODUCTION The importance of studying the gas immediately surrounding galaxies has long been understood. In particular, as the circum-galactic medium (CGM) lies at the interface between galaxies themselves, and the diffuse hydrogen in the intergalactic medium (IGM) it holds the key to understanding some of the most fundamental concepts of galaxy formation and evolution. CONCLUSIONS: Overall, our results are consistent with a picture in which the physical properties of the CGM evolve with cosmic time, manifesting as an observed evolution of Lyα halo properties. Before this scenario can be confirmed or clarified, a larger sample of QSO observations at z ∼ 6 is called for, and observations of more diagnostic lines (e.g. with the upcoming JWST mission). This will help to elucidate the processes governing the growth of the first galaxies and black
a. entities b. bodies c. times d. holes.
Q93.arXiv:1906.07262 [astro-ph.HE]: Superheavy Gravitinos and Ultra-High Energy Cosmic Rays. Krzysztof A. Meissner, Hermann Nicolai. (Submitted on 17 Jun 2019): ABSTRACT: We argue that the superheavy gravitinos that we had previously proposed as candidates for Dark Matter can offer a possible explanation for the ultra-high energy cosmic ray (UHECR) events observed at the Pierre Auger Observatory, via gravitino anti-gravitino annihilation in the `skin' of neutron stars. The large mass and strong interactions of these particles, together with their stability against decays into standard matter are essential for the proposed explanation to work. In particular, it ensues that UHECR events can be understood to originate from neutron stars inside a GKZ horizon of 50 Mpc. The composition of neutron stars near their surface could play a crucial role in explaining the presence of heavy ions in these events. If confirmed, the present results can be taken as evidence for the fundamental ansatz towards unification on which they are based. INTRODUCTION: This is based on our previous work [5, 6] where we have raised the possibility that dark matter (DM) could consist at least in part of an extremely dilute gas of very massive stable gravitinos, which are furthermore fractionally charged and strongly interacting. As we will argue here these can in principle furnish a fairly simple explanation for the most energetic cosmic ray energy events, both qualitatively and quantitatively. : Both the large gravitino mass and the amount of accumulated mass of these particles, which is on the order of the combined DM mass in the Universe, are necessary to understand the large energies and the rates of the observed UHECR events, as we shall now explain. In addition we need to make one important further assumption concerning the local distribution of DM in stellar systems. CONCLUSIONS: To be sure, the UHECR emitters are not evenly distributed throughout the universe, and we therefore expect an increased number of events to originate from superclusters of galaxies rich in neutron stars (the super-galactic plane, in particular). In particular the integral for NE may receive its dominant contribution from a disk rather than the full ball. We also note that with a maximum available energy of O(10^22 eV) our proposal can also explain the existence of (very rare) UHECR events exceeding the GKZ bound, if these originate from neutron stars within the Milky Way or nearby
a. stars b. galaxies c. quasars d. systems.
arXiv:1901.08588 [gr-qc]: 23 Jan. 2019: On the cosmological constant problem. Lucas Lombriser. (Submitted on 23 Jan 2019): ABSTRACT: An additional variation of the Einstein-Hilbert action with respect to the Planck mass provides a constraint on the average Ricci scalar that prevents vacuum energy from gravitating. Consideration of the evolution of the inhomogeneous matter distribution in the Universe with evaluation of the averaging constraint on disconnected matter cells that ultimately form isolated gravitationally bound structures yields a backreaction effect that self-consistently produces the cosmological constant of the background. A uniform prior on our location in the formation of these isolated structures implies a mean expectation for the present cosmological constant energy density parameter of Ω =0.704, giving rise to a late-time acceleration of the cosmic expansion and a coincident current energy density of matter. Introduction: The physical nature of the cosmological constant remains a persistent enigma immanent to Einstein’s Theory of General Relativity. It is generally thought to represent the gravitational contribution of vacuum fluctuations, anticipated of adequate magnitude to account for the observed late-time accelerated expansion of our Universe. CONCLUSIONS: A new framework was presented here that proposes the additional variation of the Einstein-Hilbert action with respect to the quadratic Planck mass on top of the usual metric variation. It offers the interpretation of identifying the Planck mass with a global Lagrange multiplier that imposes general relativistic dynamics on the metric prescribing the space-time for the matter fields. The variation provides a constraint equation on the average Ricci scalar that acts to prevent vacuum energy from gravitating. The evaluation of this constraint under consideration of the evolution of the inhomogeneous matter distribution in the Universe in form of disconnected matter cells representing ultimately isolated gravitationally bound structures yields a backreaction effect that self-consistently produces the cosmological constant of the background. With the application of a uniform prior on the dimensionless physical size of these structures as a measure of likelihood determining our location in the cosmic history, one finds a mean expectation for the current energy density parameter of the cosmological constant of ΩΛ = 0.704. The result is in good agreement with current cosmological observations, giving rise to a late-time acceleration of the cosmic expansion and a coincident current energy density of matter. Future analysis will reveal if the presented framework allows for a reinterpretation and possible unraveling of some cosmological obscurities such as coincidences identified for the epochs of recombination, reionization, and the star formation peak with the times of equality between the energy densities of radiation, baryons, and the cosmological constant. It may also motivate new approaches for other unresolved problems of
a. Relativity b. Gravitation c. Cosmology d. radiation
Q29. arXiv:1901.11223 [cond-mat.mtrl-sci]: Charge Density Wave Hampers Exciton Condensation in 1T-TiSe2. Chao Lian, Zulfikhar A. Ali, Bryan M. Wong. (Submitted on 31 Jan 2019): ABSTRACT: The Bose-Einstein condensation of excitons continues to garner immense attention as a prototypical example for observing emergent properties from many-body quantum effects. In particular, Titanium Diselenide (TiSe2) is a promising candidate for realizing exciton condensation and was experimentally observed only very recently [{this https URL\%2Fscience.aam6432}{Science \textbf{358} 1314 (2017)}]. Surprisingly, the condensate was experimentally characterized by a soft plasmon mode that only exists near the transition temperature, Tc, of the charge density wave (CDW). Here, we characterize and analyze the experimental spectra using linear-response time-dependent density functional theory and find that the soft mode can be attributed to interband electronic transitions. At the CDW state below Tc, the periodic lattice distortions hamper the spontaneous formation of the exciton by introducing a CDW gap. Our surprising results contradict previous simplistic analytical models commonly used in the scientific literature. In addition, we find that a finite electronic temperature, Te, introduces an effective band gap and prevents the condensation above Tc. The band gap lifts the soft mode and merges it into the regular intraband plasmon. The combined effect of the CDW and Te explains the fragile temperature-dependence of the exciton condensation. Taken together, our work provides the first \textit{ab initio} atomic-level framework for rationalizing recent experiments and further manipulating exciton condensates in TiSe2. INTRODUCTION: Bose-Einstein condensates (BECs) exhibit exotic transport phenomena such as superfluity in liquid Helium and superconductivity via Cooper pairs. Other bosonic quasiparticles, such as excitons, polaritons, and magnons can also form a BEC, with exciton condensation particularly drawing immense recent attention. The exciton condensate is predicted to form a superfluid current, which not only is an exotic emergent phenomenon in fundamental quantum research, but also vital for designing next-generation, scatteringfree electronic devices. CONCLUSIONS: Both the CDW and effective band gaps lift the soft mode and merge it into the regular intraband plasmon, which explains why the soft mode is only observed at Tc. As such, our ab initio framework provides critical mechanistic insight into recent exciton condensation experiments and presents additional avenues to experimentalists for further manipulating exciton condensates in
a. TiSe3 b.TiSe2 c. TiSe4 d. TiSe
Q30. arXiv:1901.11243 [nlin.PS]: Interactions of solitons with positive and negative masses: Shuttle motion and co-acceleration. Hidetsugu Sakaguchi, Boris A. Malomed. (Submitted on 31 Jan 2019):ABSTRACT: We consider a possibility to realize self-accelerating motion of interacting states with effective positive and negative masses in the form of pairs of solitons in two-component BEC loaded in an optical-lattice (OL) potential. A crucial role is played by the fact that gap solitons may feature a negative dynamical mass, keeping their mobility in the OL. First, the respective system of coupled Gross-Pitaevskii equations (GPEs) is reduced to a system of equations for envelopes of the lattice wave functions. Two generic dynamical regimes are revealed by simulations of the reduced system, viz., shuttle oscillations of pairs of solitons with positive and negative masses, and splitting of the pair. The co-accelerating motion of the interacting solitons, which keeps constant separation between them, occurs at the boundary between the shuttle motion and splitting. The position of the co-acceleration regime in the system's parameter space can be adjusted with the help of an additional gravity potential, which induces its own acceleration, that may offset the relative acceleration of the two solitons, while gravity masses of both solitons remain positive. The numerical findings are accurately reproduced by a variational approximation. Collisions between shuttling or co-accelerating soliton pairs do not alter the character of the dynamical regime. Finally, regimes of the shuttle motion, co-acceleration, and splitting are corroborated by simulations of the original GPE system, with the explicitly present OL potential. CONCLUSION: The objective of this work is to establish the framework which admits co-accelerating motion of interacting objects with opposite signs of the effective mass, using pairs of matter-wave solitons which move against the background of the OL (optical-lattice) potential. The effective negative mass of one component is provided by the known property of gap solitons. Reducing the full system of the GPEs (Gross-Pitaevskii equations), which includes the OL potential,to equations for slowly varying envelopes, systematic simulations and the VA (variational approximation) reveal two generic dynamical regimes, viz., spontaneous shuttle oscillations of the mean position of the soliton pair, in the course of which the solitons periodically pass through each other, and splitting of the
a. threesome b. pair c. foursum d. matter-wave.
Q31. arXiv:1902.00410 [physics.app-ph]: Light Enhanced Blue Energy Generation using MoS2 Nanopores. Michael Graf, Martina Lihter, Dmitrii Unuchek, Aditya Sarathy, Jean-Pierre Leburton, Andras Kis, Aleksandra Radenovic. (Submitted on 1 Feb 2019) ABSTRACT: Blue energy relies on the chemical potential difference generated between solutions of high and low ionic strength and would provide a sun-and-wind independent energy source at estuaries around the world. Converting this osmotic energy through reverse-electrodialysis relies on ion-selective membranes. A novel generation of these membranes is based on atomically thin MoS2 membranes to decrease the resistance to current flow to increase power output. By modulating the surface charge by light we are able to raise the ion selectivity of the membrane by a factor of 5 while staying at a neutral pH. Furthermore, we find that the behavior of small nanopores is dominated by surface conductance. We introduce a formalism based on the Dukhin number to quantify these effects in the case of a concentration gradient system. As a consequence, the charges created by light illumination provoke two important changes. Increased surface charge at the pore rim enhances the ion selectivity and therefore larger osmotic voltage (dominating in small pores), while the increased surface charge of the overall membrane enhances the surface conductance and therefore the osmotic current (dominating in larger pores). The combination of these effects might be able to efficiently boost the energy generation with arrays of nanopores with varying pore sizes. Introduction: The term blue energy embodies all the attempts to harvest energy coming from the spontaneous and irreversible mixing of sea-water and river-water. The chemical potential difference between two liquids of different salt concentration holds immense amounts of energy: 2.3MJ of theoretical energy is buried in each cubic meter of water. CONCLUSIONS:The continuum PNP model described above is quite useful to investigate electrodiffusion of charged species in ion channels, however there are a few known shortcomings. These include the neglect of finite volume effect of the ionic particles and correlation effects (such as ionion interactions and steric effects). While there have been a few known corrections and modifications to the PNP theory, they have not been considered in our model. Alternately, many other ab-initio methods can also be used to investigate electrodiffusion in narrowly confined ion channels such as Molecular Dynamics (MD), Brownian Dynamics (BD) and Monte-Carlo
a. calculations b. expectations c. simulations d. aspects.
Q32. arXiv:1902.00540 [astro-ph.CO]: New insight into EM radiation from spinning dust and its influence on the Cosmic Microwave Background. Ariel Guerreiro, José Tito Mendonça, Robert Bingham. (Submitted on 1 Feb 2019): ABSTRCT: Dust is ubiquitous in the Universe and its influence on the observed Electromagnetic (EM) radiation needs to be correctly addressed. In recent years it became clear that scattering of EM radiation from interstellar dust grains could change the local properties of the observed Cosmic Microwave Background (CMB) radiation. Here we consider the relevant processes of emission and scattering of EM radiation from spinning dust particles, and discuss their possible influence on the CMB. In particular, we show that scattered radiation can establish a correlation between different spectral components of galactic dipolar emission. This could explain the observed correlation between the CMB and the 100-micron thermal emission form interstellar dust. Another important property of CMB is related with its polarisation anisotropies, and the observation of a cosmological B-mode. We show that scattering of CMB radiation from dust grains in the presence of a static magnetic field could indeed create a B-mode spectral component, which is very similar to that due to primordial gravitational waves. This can be described by a kind of Cotton-Mutton effect on the CMB radiation. INTRODUCTION: Currently, the analysis of the influence of the dust dynamics on the CMB depend on a large degree of extrapolation and modelling of the rotational dynamics of the grains [6]. Of particular importance in the study of CMB are the anisotropies of their fundamental parameters, most notably the temperature and polarisation anisotropies. In the case of the later, the analysis is done in terms of the B and E modes, measured in terms of two Stokes parameters Q and U that are analogous to decomposing a vector field into a gradient part (E) and a divergence free curl part (B). The accurate detection of the B and E mode are extremely important in the understanding of the structure of the early Universe. CONCLUSIONS: This dust induced delensing results from a kind of collective Cotton-Mouton effect, which was described here with the help of a ray-tracing code for the two orthogonal polarization states associated with the magnetized dust gas. The ray-tracing simulations have also shown that, both magnetic field perturbations and dust density modulations can leave an imprint on the polarization pattern of the broad band radiation spectrum. For specific dust density modulation conditions, formation of caustics can take place, which however disappears with propagation. Our results could be useful to the understanding of CMB polarization. The importance of dust in the explanation of the observed B-mode signature was noticed before [8]. Previous models were based on thermal radiation from dust grains. Here we provide an alternative and more specific process, which can be used to explain qualitatively the observed phenomena. This, in a sense, completes the demonstration that dust is the main ingredient leading to the formation of a B-mode on the polarization pattern of the CMB radiation. Specific models of dust grain distributions will have to be establish in order to bring the explanation to more a quantitative accuracy
a. standard b. level c. exponent d. threshold.
Q33.arXiv:1902.00798 [astro-ph.GA]: The role of magnetic field in molecular cloud formation and evolution. Patrick Hennebelle, Shu-ichiro Inutsuka. (Submitted on 2 Feb 2019): ABSTRACT: We review the role that magnetic field may have on the formation and evolution of molecular clouds. After a brief presentation and main assumptions leading to ideal MHD equations, their most important correction, namely the ion-neutral drift is described. The nature of the multi-phase interstellar medium (ISM) and the thermal processes that allows this gas to become denser are presented. Then we discuss our current knowledge of compressible magnetized turbulence, thought to play a fundamental role in the ISM. We also describe what is known regarding the correlation between the magnetic and the density fields. Then the influence that magnetic field may have on the interstellar filaments and the molecular clouds is discussed, notably the role it may have on the prestellar dense cores as well as regarding the formation of stellar clusters. Finally we briefly review its possible effects on the formation of molecular clouds themselves. We argue that given the magnetic intensities that have been measured, it is likely that magnetic field is i) responsible of reducing the star formation rate in dense molecular cloud gas by a factor of a few, ii) strongly shaping the interstellar gas by generating a lot of filaments and reducing the numbers of clumps, cores and stars, although its exact influence remains to be better understood. % by a factor on the order of at least 2. Moreover at small scales, magnetic braking is likely a dominant process that strongly modifies the outcome of the star formation process. Finally, we stress that by inducing the formation of more massive stars, magnetic field could possibly enhance the impact of stellar feedback. INTRODUCTION: The interstellar cycle, which takes place within galaxies, is fundamental for our universe as it controls the formation of stars and therefore the evolution of galaxies. Yet given the broad range of spatial scales and the profusion of physical processes involved, our understanding is still very incomplete. Amongst other processes, namely gravity, compressible turbulence, radiation, cosmic rays and stellar feedback, magnetic field is also contributing significantly to the evolution of the interstellar medium (ISM) and more specifically to the formation of stars. As a matter of evidence, the magnetic energy in the ISM is comparable to the other energies as for example the kinematic one. Deciphering the various roles that magnetic field is playing is however not obvious, i) because measuring it remains a challenge, ii) because magnetic field is not a mere pressure and is highly non-isotropic in nature, iii) because observations do not allow us to easily vary the parameters as it is possible to do in experiments. This however can be done in numerical simulations where the influence of a specific parameter, like the magnetic intensity, can be modified and studied. CONCLUSIONS: While it is now almost certain that magnetic fields do not regulate the star formation process by reducing the star formation rate drastically, as proposed three decades ago, it is likely the case that magnetic fields contribute to reduce it by a factor of a few. Moreover since it has been found by various groups that magnetic field tends to reduce the fragmentation and to produce stars with larger mass, another possible consequence of magnetic field is to enhance stellar feedback and therefore to reduce the star formation rate and efficiency in molecular clouds. This latter aspect remains however to be confirmed as numerical simulations are not able now to cover the necessary range of scales. Finally we stress that magnetic field is likely to have drastic consequences on the formation of protoplanetary disks through magnetic braking by reducing and even possibly controlling their
a. crticallity b. strength c. formation d. size.
Q34. arXiv:1902.01140 [astro-ph.SR]: Variable emission mechanism of a Type IV radio burst. D. E. Morosan, E. K. J. Kilpua, E. P. Carley, C. Monstein. (Submitted on 4 Feb 2019):ABSTRACT: The Sun is an active star and the source of the largest explosions in the solar system, such as flares and coronal mass ejections (CMEs). Flares and CMEs are powerful particle accelerators that can generate radio emission through various emission mechanisms. Aims. CMEs are often accompanied by Type IV radio bursts that are observed as continuum emission in dynamic spectra at decimetric and metric wavelengths, but their emission mechanism can vary from event to event. Here, we aim to determine the emission mechanism of a complex Type IV burst that accompanied the flare and CME on 22 September 2011. Methods. We used radio imaging from the Nançay Radioheliograph, spectroscopic data from the e-Callisto network, ARTEMIS, Ondrejov, and Phoenix3 spectrometers combined with extreme-ultraviolet observations from NASA's Solar Dynamic Observatory to analyse the Type IV radio burst and determine its emission mechanism. Results. We show that the emission mechanism of the Type IV radio burst changes over time. We identified two components in the Type IV radio burst: an earlier stationary Type IV showing gyro-synchrotron behaviour, and a later moving Type IV burst covering the same frequency band. This second component has a coherent emission mechanism. Fundamental plasma emission and the electroncyclotron maser emission are further investigated as possible emission mechanisms for the generation of the moving Type IV burst. Conclusions. Type IV bursts are therefore complex radio bursts, where multiple emission mechanisms can contribute to the generation of the wide-band continuum observed in dynamic spectra. Imaging spectroscopy over a wide frequency band is necessary to determine the emission mechanisms of Type IV bursts that are observed in dynamic spectra. INTRODUCTION: CMEs can also be accompanied by continuum emission at decimetric and metric wavelengths, so-called Type IV radio bursts, which can have either stationary or moving sources and various emission mechanisms. CONCLUSIONS: Our analysis of the Type IV radio burst highlights the necessity of instruments capable of high-frequency and temporal resolution spectroscopy to complement the imaging capabilities of the NRH and instruments capable of imaging above the NRH frequency range.The Expanded Owens Valley Solar Array (EOVSA) is currently capable of such observations, but it is limited to higher frequency ranges of 1–18 GHz. Other instruments are now available at lower frequencies (<300 MHz), such as the Low Frequency Array (LOFAR) and the Murchinson Widefield Array (MWA), but there is still a need to provide imaging spectroscopy with high resolution at frequencies between 400-1000 MHz. These instruments would provide the possibility of answering outstanding questions on the emission mechanisms of TypeIV radio bursts and their potential in estimating CME magnetic fields for space weather
a. purposes b. conditions c. modification d. resolutions.
Q35. arXiv:1811.01078 [gr-qc]: On a soliton-type spacetime defect. F.R. Klinkhamer. (Submitted on 5 Nov 2018 (v1), last revised 4 Feb 2019 (this version, v3)): ABSTRACT: We review the construction of a particular soliton-type solution of the classical Einstein and matter-field equations. This localized finite-energy static classical solution can be interpreted as a single spacetime defect embedded in Minkowski spacetime and may give rise to several new effects. For a Skyrme-type theory with small enough matter-field energy scale compared to the Planck energy scale and for a sufficiently small defect length scale, the existence of a globally regular solution requires a negative active gravitational mass, so that the defect repels a distant test particle ("antigravity"). There also exist "stealth defects" which have a vanishing asymptotic gravitational mass. These stealth defects are, however, not entirely invisible as they bring about a new type of gravitational lensing. INTRODUCTION: One hypothesis is that the Universe started out in some form of “quantum phase” which gave rise to classical spacetime and gravity, as described by Einstein’s General Theory of Relativity. It is then possible that this process is analogous to the cooling of a liquid, which produces an atomic crystal. But, if the cooling of the latter process is rapid, the resulting crystal will be imperfect, containing crystallographic defects. For the above-mentioned quantum phase and the resulting classical spacetime, the analogy suggests the possibility of having “spacetime defects” (i.e., imperfections in the fabric of spacetime). Remark that, historically, some of the earliest ideas on a foam-like structure of spacetime go back to Wheeler in the 1950s.CONCLUSION: The issue of (genuine or effective) topology change is essential for a proper understanding of the small-scale structure of spacetime, which brings us back to the quantum
a. Jump b. relaxation c. phase d. transions
Q36. arXiv:1902.01180 [cond-mat.mes-hall]: Single-photon light emitting diodes based on pre-selected quantum dots using a deterministic lithography technique. Marc Sartison, Simon Seyfferle, Sascha Kolatschek, Stefan Hepp, Michael Jetter, Peter Michler, Simone Luca Portalupi: (Submitted on 4 Feb 2019): ABSTRACT: In the present study, we developed a fabrication process of an electrically driven single-photon LED based on InP QDs emitting in the red spectral range, the wavelength of interest coinciding with the high efficiency window of Si APDs. A deterministic lithography technique allowed for the pre-selection of a suitable QD, here exclusively operated under electrical carrier injection. The final device was characterized under micro-electroluminescence in direct current, as well as in pulsed excitation mode. In particular, under pulsed excitation of one device, single-photon emission of a spectral line, identified as an exciton, has been observed with g(2)raw (0)=0.42±0.02 where the non-zero g(2) -value is mainly caused by background contribution in the spectrum and re-excitation processes due to the electrical pulse length. The obtained results constitute an important step forward in the fabrication of electrically driven single-photon sources, where deterministic lithography techniques can be used to sensibly improve the device performances. In principle, the developed process can be extended to any desired emitter wavelength above 600nm up to the telecom bands. In conclusion, we realized a QD-based single-photon LED, operating at the absolute efficiency maximum of Si APDs, via an optimized deterministic fabrication technique. QDs were here pre-selected in µ-EL and the device was fabricated via state-of-the-art low temperature in-situ lithography and standard clean room fabrication techniques. The successful deterministic integration of QDs could be verified by the acquisition of µ-EL maps combined with reflectivity maps. Furthermore, the device performances were characterized under pulsed electrical excitation by means of EL polarization dependence, time-resolved EL decay time and photon-autocorrelation measurements. A decay time of 599ps under triggered electrical excitation compares well with already reported values for InP QDs in literature. Additionally, a g(2) dcc(0) value of 0.41±0.03 could be recorded, only corrected for the detector induced dark count contribution, thus indicating dominant single-photon emission. By accounting also for the spectral background contribution, a corrected g(2)bgc(0) value of 0.23±0.05 could be estimated. The deterministic fabrication process of SPLEDs developed in this work can be applied to any electrically driven emitter from the red spectral range up to the telecom regimes. The proof of principle measurements presented here show the possibility of combining in-situ optical lithography with electrically driven non-classical light sources. It enables the route towards electrically driven cavity systems and high brightness devices. Improving the performances of single QD devices via deterministic lithography techniques will be of key importance in a range of quantum technology implementations, from quantum distribution to quantum enhanced
a. metrology b. meteorology c. light-source d. emission.
Q37. arXiv:1902.01409 [astro-ph.GA]: The Physical Nature of Neutral Hydrogen Intensity Structure. S.E. Clark, J.E.G. Peek, M.-A. Miville-Deschênes. (Submitted on 4 Feb 2019). ABSTRACT: We investigate the physical properties of structures seen in channel map observations of 21-cm neutral hydrogen (HI) emission. HI intensity maps display prominent linear structures that are well aligned with the ambient magnetic field in the diffuse ISM. Some literature holds that these structures are "velocity caustics", fluctuations imprinted by the turbulent velocity field, and are not three-dimensional density structures in the interstellar medium. We test this hypothesis by stacking probes of the density field -- broadband far infrared (FIR) emission and the integrated HI column density (NHI) -- at the locations of linear HI intensity structures. We find that the HI intensity features are real density structures and not velocity caustics. We generalize the investigation to all small-scale structure in HI channel maps, and analyze this correlation as a function of velocity channel width, finding no measurable contribution from velocity caustics to the HI channel map emission. Further, we find that small-scale HI channel maps structures have elevated FIR/NHI, implying that this emission originates from a colder, denser phase of the ISM than the surrounding material. The data are consistent with a multi-phase diffuse ISM in which small-scale structures in narrow HI channel maps are preferentially cold neutral medium (CNM) that is anisotropically distributed and aligned with the local magnetic field. The shallow spatial power spectrum of narrow HI channels is often attributed to velocity caustics. We conjecture instead that the small-scale structure and narrow linewidths typical of CNM explain the observed relationship between the spatial power spectrum and channel width. DETAILS: The diffuse interstellar medium (ISM) fills most of the volume of the Milky Way. This material, the progenitor of dense structures that eventually form stars, is multiphase, magnetized, and turbulent. The ISM is broadly partitioned into ionized, molecular, and atomic components, with the atomic gas composed of a cold neutral medium (CNM), warm neutral medium (WNM), and a thermally unstable component. Understanding the distribution of matter and energy within and between these phases is a major goal of ISM research. CONCLUSIONS: Software: astropy (Astropy Collaboration etal. 2013, 2018), cmocean (Thyng et al. 2016), matplotlib (Hunter 2007), numpy (Oliphant 2015). A shallower spatial power spectrum slope measured in narrower velocity channels is qualitatively consistent with a higher contribution to the intensity in narrow channels from CNM gas. Previous work has attributed such a change in the spatial power spectrum to velocity fluctuations, and used this to derive the slope of the turbulent velocity power spectrum in the gas. This work calls those analyses into question. This work calls for a significant reassessment of many observational and theoretical studies of turbulence in
a. He b. Hi c. Hydrogen d. Helium.
Q38. arXiv:1902.01440 [astro-ph.GA]: Radio Source Extraction with ProFound. C. L. Hale, A. S. G. Robotham, L. J. M. Davies, M. J. Jarvis, S. P. Driver, I. Heywood. (Submitted on 4 Feb 2019). ABSTRACT: In the current era of radio astronomy, continuum surveys observe a multitude of objects with complex morphologies and sizes, and are not limited to observing point sources. Typical radio source extraction software generates catalogues by using Gaussian components to form a model of the emission. This may not be well suited to complicated jet structures and extended emission, particularly in the era of interferometers with a high density of short baselines, that are sensitive to extended emission. In this paper, we investigate how the optically-motivated source detection package ProFound (Robotham et al. 2018) may be used to model radio emission of both complicated and point-like radio sources. We use a combination of observations and simulations to investigate how ProFound compares to other source extractor packages used for radio surveys. We find that ProFound can accurately recover both the flux densities of simulated Gaussian sources as well as extended radio galaxies. ProFound can create models that trace the complicated nature of these extended galaxies, which we show is not necessarily the case with other source extraction software. Our work suggests that our knowledge of the emission from extended radio objects may be both over or under-estimated using traditional software. We suggest that ProFound offers a useful alternative to the fitting of Gaussian components for generating catalogues from current and future radio surveys. Furthermore, ProFound's multi-wavelength capabilities will be useful in investigating radio sources in combination with multi-wavelength data. DETAILS: Modern radio surveys are able to combine deep and widearea observations of the sky with greater ease than ever before. CONCLUSIONS: We therefore feel that ProFound may be a beneficial source extraction software for both current as well as the future radio surveys that we expect to complete at higher angular resolutions and greater depths. Not only this, but as ProFound is designed to be used within a multi-wavelength framework. This can therefore be used to generate consistent flux extraction of sources across the electromagnetic spectrum. This is by using segments defined by ProFound at one wavelength to calculate fluxes at another. This will be useful for not only obtaining consistently extracted fluxes at different radio frequencies but can also be important in making use of observations across the electromagnetic spectrum. This is advantageous in the era of multi-wavelength
a. frame-work b. data c. astronomy d. astrophysics.
Q39. arXiv:1902.01675 [astro-ph.GA]: The mass, location and heating of the dust in the Cassiopeia A supernova remnant. F. D. Priestley, M. J. Barlow, I. De Looze. (Submitted on 5 Feb 2019): ABSTRACT: We model the thermal dust emission from dust grains heated by synchrotron radiation and by particle collisions, under conditions appropriate for four different shocked and unshocked gas components of the Cassiopeia A (Cas A) supernova remnant (SNR). By fitting the resulting spectral energy distributions (SEDs) to the observed SNR dust fluxes, we determine the required mass of dust in each component. We find the observed SED can be reproduced by ∼0.6 M⊙ of silicate grains, the majority of which is in the unshocked ejecta and heated by the synchrotron radiation field. Warmer dust, located in the X-ray emitting reverse shock and blastwave regions, contribute to the shorter wavelength infrared emission but make only a small fraction of the total dust mass. Carbon grains can at most make up ∼25% of the total dust mass. Combined with estimates for the gas masses, we obtain dust-to-gas mass ratios for each component, which suggest that the condensation efficiency in the ejecta is high, and that dust in the shocked ejecta clumps is well protected from destruction by sputtering in the reverse shock. DETAILS: Previous modelling of the Cas A dust emission has been based on fitting the spectral energy distribution (SED) with some number of temperature components for a given dust composition (i.e. ‘hot’ and ‘cold’ dust). This assumes all dust grains radiate at the same temperature for each component, but grains of different sizes will in general have different equilibrium temperatures for the same heating source. Additionally, smaller grains can undergo large temperature fluctuations. CONCLUSIONS: This is consistent with dust grains being efficiently sputtered at high temperatures, whereas in the ejecta clumps which have passed through the reverse shock, the dust is more resilient to destruction. Magnesium silicate grains, with possible iron inclusions, are found to reproduce almost all of the observed Cas A dust spectrum, with a relatively minor amount of another species (FeO, SiO2 or Mg0.7SiO2.7) required to reproduce the 21µm emission peak. While carbon grains may be present, they cannot make up a large fraction of the dust mass in the X-ray emitting gas (< 25%) without predicting NIR fluxes in excess of those observed. If the mass fractions do not vary significantly between the shocked and unshocked ejecta, carbon dust can be ruled out as a major constituent of the ejecta dust. The unshocked and clumped ejecta dust, making up the majority of the mass, is heated mostly by the remnant’s synchrotron radiation field, while the diffuse and blastwave dust, which dominates the total SED luminosity, is heated by collisions with electrons and nuclei. The total dust mass in Cas A is consistent with CCSNe being significant contributors to the dust in high-redshift galaxies, particularly if much of it is present in clumps which survive the passage of the reverse shock without
a. disruption b. destruction c. resolution d. prediction.
Q40. arXiv:1902.01550 [cond-mat.mes-hall]: Coherent spin control of s-, p-, d- and f-electrons in a silicon quantum dot. R. C. C. Leon, C. H. Yang, J. C. C. Hwang, J. Camirand Lemyre, T. Tanttu, W. Huang, K. W. Chan, K. Y. Tan, F. E. Hudson, K. M. Itoh, A. Morello, A. Laucht, M. Pioro-Ladriere, A. Saraiva, A. S. Dzurak. (Submitted on 5 Feb 2019): ABSTRACT: Once the periodic properties of atoms were unveiled, chemical bonds could be understood in terms of the valence of atoms. Ideally, this rationale would extend to quantum dots, and quantum computation would be performed by merely controlling electrons in the outer shell. Imperfections in the semiconductor material, even at the atomic scale, disrupt this analogy between atoms and quantum dots, so that real devices seldom display such intelligible many-electron arrangement. We demonstrate here an electrostatic quantum dot that overcomes the hardships of disorder and reveals a well defined shell structure. We observe four shells (31 electrons) with multiplicities given by spin and valley degrees of freedom. We explore various fillings consisting of a single valence electron -- namely 1, 5, 13 and 25 electrons -- as potential qubits. An integrated micromagnet allows us to perform electrically driven spin resonance (EDSR). Higher shell states are shown to be more susceptible to the driving field, leading to faster Rabi rotations of the qubit. We investigate the impact of orbital excitations of the p and d-shell electrons on single qubits as a function of the dot deformation. This allows us to tune the dot excitation spectrum and exploit it for faster qubit control. Furthermore, hotspots arising from this tunable energy level structure provide a pathway towards fast spin initialisation. DETAILS:We demonstrate here an electrostatic quantum dot that overcomes the hardships of disorder and reveals a well defined shell structure. We observe four shells (31 electrons) with multiplicities given by spin and valley degrees of freedom3,4,7. We explore various fillings consisting of a single valence electron – namely 1, 5, 13 and 25 electrons – as potential qubits. CONCLUSIONS: The present work experimentally demonstrates that purely spin-based qubits may be implemented in multielectron quantum dots. This could be a desirable feature as long as the shell structure is well preserved, such as in very small SiMOS electrostatic quantum dots. Operation based on EDSR takes advantage of the extended wavefunction to drive the qubit with higher control fidelity and longer distance J coupling between qubits. A multielectron system results in a richer many-body excitation spectrum, which could have higher Rabi frequencies for fast qubit gates and enhanced relaxation rates for quick qubit initialization. We anticipate the possibility of complex two qubit physics, with a possible singlettriplet inversion, mimicking the physics of paramagnetic bonding. This would require a revision of the two qubits gate strategies, as well as the spin-to-charge conversion techniques for qubit
a. In-read b. contacts c. dots d. read-out.
Q41.arXiv:1902.02474 [hep-ph]: Isoscalar and isovector kaon form factors from e + e − and τ data. K.I. Beloborodov, V.P. Druzhinin, S.I. Serednyakov. (Submitted on 7 Feb 2019): ABSTRACT: The recent precise measurements of the e+ e−→KSKL and e+ e− → K+ K−cross sections and the hadronic spectral function of the τ−→K−KS ντ decay are used to extract the isoscalar and isovector electromagnetic kaon form factors and their relative phase in a model independent way. The experimental results are compared with a fit based on the vector-meson-dominance model. INTRODUCTION: Kaon electromagnetic form factors are the key objects in hadron physics describing electromagnetic interaction of kaons and providing important information about their internal structure. In conclusion, we have used recent precise measurements of the e+ e− → K ¯ K cross sections and the K−KS spectrum in the τ− → K−KS ντ decay to separate the isoscalar and isovector electromagnetic kaon form factors and determine the relative phase between them in a model independent way. The latter shows an unexpected energy dependence in the energy range from 1.06 to 1.5 GeV. It is almost constant and close to zero. We have simultaneously fitted to the e+e− → K+K− and e+e− → KSKL cross-section data and the hadronic mass spectrum in the τ− → K−KS ντ decay in the framework of the VMD model. The fit reproduces data reasonably well and shows that the CVC hypothesis for the K ¯ K system works with a few percent accuracy. To explain the specific energy dependence of the relative phase between the isoscalar and isovector form factors the large difference between parameters cρ' and cω' is required, which contradicts to the quark model expectation
a. cρ' = cω' b. cρ' differs cω' c. cρ' = cω'. d. cρ' not equal cω'.
Q42. arXiv:1902.02691 [hep-ph]: The symmetry of 4×4 mass matrices predicted by the spin-charge-family theory --- SU(2)×SU(2)×U(1) --- remains in all loop corrections. A. Hernandez-Galeana, N.S. Mankoc Borstnik. (Submitted on 8 Jan 2019): ABSTRACT: The spin-charge-family theory predicts the existence of the fourth family to the observed three. The 4×4 mass matrice, determined by the nonzero vacuum expectation values of the two triplet scalars, the gauge fields of the two groups of SU˜(2) determining family quantum numbers, and by the contributions of the dynamical fields of the two scalar triplets and the three scalar singlets with the family members quantum numbers ( τα = (Q, Q′ , Y′ ) ) --- manifest the symmetry SU˜(2)×SU˜(2)×U(1) . All scalars carry the weak and the hyper charge of the standard model higgs field ( ± 1/2, ∓1/2, respectively). It is demonstrated, using the massless spinor basis, that the symmetry of the 4×4 mass matrices remains SU(2)×SU(2)×U(1) in all loop corrections, and it is discussed under which conditions this symmetry is kept under all corrections, that is with the corrections induced by the repetition of the nonzero vacuum expectation values included. CONCLUSION: After the electroweak phase transition, caused by the scalar fields with the space index, the two groups of four families become massive. The lowest of the two groups of four families contains the observed three, while the fourth remains to be measured. The lowest of the upper four families is the candidate for the dark
a. space b. matter c. matrices d. fields
Q43. arXiv:1902.02373 [astro-ph.GA]: A Near Infrared View of Nearby Galaxies: The Case of NGC 6300. Gaia Gaspar, Rubén Díaz, Damián Mast, Ary D'Ambra, María Paz Agüero, Guillermo Günthardt. (Submitted on 6 Feb 2019): ABSTRACT: We present a near-infrared study of the Seyfert 2 galaxy NGC6300, based on subarcsecond images and long slit spectroscopy obtained with Flamingos-2 at Gemini South. We have found that the peak of the nuclear continuum emission in the Ks band and the surrounding nuclear disk are 25pc off-center with respect to the center of symmetry of the larger scale circumnuclear disk, suggesting that this black hole is still not fixed in the galaxy potential well. The molecular gas radial velocity curve yields a central black hole upper mass estimation of M_{SMBH}^{upper}=(6+ or - 2)x10^{7} Msun. The Paβ emission line has a strongly asymmetric profile with a blueshifted broad component that we associate with a nuclear ionized gas outflow. We have found in the Ks -band spectra that the slope of the continuum becomes steeper with increasing radii, which can be explained as the presence of large amounts of hot dust not only in the nucleus but also in the circumnuclear region up to r=27pc. In fact, the nuclear red excess obtained after subtracting the stellar contribution resembles to that of a blackbody with temperatures around 1200K. This evidence supports the idea that absorbing material located around the nucleus, but not close enough to be the torus of the unified model, could be responsible for at least part of the nuclear obscuration in this Seyfert 2 nucleus. DETAILS:Active Galactic Nuclei are among the most intriguing objects because they are present throughout most of the universe’s history, meaning they must be an essential ingredient in the galactic and cosmic evolution, yet there are several aspects that are still not completely understood. The near-infrared (NIR) bands offer the advantage of lowering the galactic extinction both in the Milky Way and in the host galaxy, reaching 10% of the V-band extinction in the Ks band. This allows NIR photons to escape easily and provides a more detailed view of the structure and physical state of the circumnuclear regions. At the same time, more energetic photons absorbed by dust are re-emitted in the infrared allowing us to map the most dusty regions. In particular, in the K band is possible to observe a red excess associated with hot dust in the nuclear regions. NIR also has the advantage of being observable from the ground and now we count with several facilities optimized for imaging and spectroscopy in the NIR bands. CONCLUSIONS: The results presented in this work provide different elements that help to understand the way in which an obscured AGN of intermediate-low mass grows its mass in the presence of a weak bar and with large amounts of circumnuclear dust. But there are many questions that arise and require a systematic study in a statistically significant sample. What is the relationship between nuclear feeding mechanisms in Seyfert galaxies and the strength of the bar? How the appearance of the circum nuclear ring, the growth of the SMBH, the AGN duty cycle, and the life cycle of the barall linked? And finally, how does the distribution of circum nuclear dust influence the Seyfert1/Seyfert2 classification? All this places obscured AGN as the most appropriate objects to deepen those aspects of the Unified Model that are still under strong
a. debate b. doubt c. expectation d. influence.
Q44. arXiv:1902.03106 [gr-qc]: A hydrodynamic approach to the classical ideal gas. Bartolomé Coll, Joan Josep Ferrando, Juan Antonio Sáez. (Submitted on 8 Feb 2019): ABSTRACT: The necessary and sufficient condition for a conservative perfect fluid energy tensor to be the energetic evolution of a classical ideal gas is obtained. This condition forces the square of the speed of sound to have the form c^2s=γp / ρ+p in terms of the hydrodynamic quantities, energy density ρ and pressure p, γ being the (constant) adiabatic index. The {\em inverse problem} for this case is also solved, that is, the determination of all the fluids whose evolutions are represented by a conservative energy tensor endowed with the above expression of c^2s , and it shows that these fluids are, and only are, those fulfilling a Poisson law. The relativistic compressibility conditions for the classical ideal gases and the Poisson gases are analyzed in depth and the values for the adiabatic index γ for which the compressibility conditions hold in physically relevant ranges of the hydrodynamic quantities ρ,p are obtained. Some scenarios that model isothermal or isentropic evolutions of a classical ideal gas are revisited, and preliminary results are presented in applying our hydrodynamic approach to looking for perfect fluid solutions that model the evolution of a classical ideal gas or of a Poisson gas. DETAILS: In the relativistic framework, a perfect fluid is usually assumed to be a perfect energy tensor, T ≡ (ρ + p)u ⊗ u+pg, solution to the conservation equations ∇·T = 0. It can model a test fluid in any given space-time, or the source of a solution of the Einstein field equations G = kT. Nevertheless, complementary physical requirements on the hydrodynamic quantities (the unit velocity u, the energy density ρ, and the pressure p) must be imposed for T to represent the energetic evolution of a realistic thermodynamic fluid in local thermal equilibrium.CONCLUSIONS: For a family of perfect fluid solutions of the Einstein field equations with perfect energy tensor T ≡ (u,ρ,p), our method consist in the following steps. In a first step we impose the generic hydrodynamic constraint and obtain the indicatrix function χ = χ(ρ,p) for the subfamily that verifies it. In a second step we detect the subfamily with an ideal gas indicatrix by imposing χ = χ(π) not equal to π. Finally, in a third step, when this function does not coincide with the CIG indicatrix for any value of the involved parameters, we can look for solutions that approximates a
a. CKT b. CIG c. CDG d. CFG
45.arXiv:1902.02832 [astro-ph.CO]: CO luminosity-Linewidth correlation of low and high redshift galaxies and its possible cosmological utilization. Yi-han Wu (Nthu), Tomotsugu Goto, Ece Kilerci Eser, Tetsuya Hashimoto, Seong-jin Kim, Chia-ying Chiang, Ting-chi Huang. (Submitted on 7 Feb 2019): ABSTRACT: A linear correlation has been proposed between the CO luminosity (L′CO) and full-width at half maximum (FWHM) for high-redshift (z > 1) submillimeter galaxies. However, the controversy concerning the L′CO-FWHM correlation seems to have been caused by the use of heterogeneous samples (e.g., different transition lines) and/or data with large measurement uncertainties. In order to avoid the uncertainty caused by using different rotational transitions, in this work we make an extensive effort to select only CO(J=−0) data from the literature. We separate these wide-ranging redshift data into two samples : the low-redshift (z < 1) and high-redshift (z > 1) samples. The samples are corrected for lensing magnification factors if gravitational-lensing effects appeared in the observations. The correlation analysis shows that there exists significant L ′ CO -FWHM correlations for both the low-redshift and high-redshift samples. A comparison of the low- and high-redshift ′ CO -FWHM correlations does not show strong evolution with redshift. Assuming that there is no evolution, we can use this relation to determine the model independent distances of high-redshift galaxies. We then constrain cosmological models with the calibrated high-redshift CO data and the sample of Type Ia supernovae in the Union 2.1 compilation. In the constraint for wCDM with our samples, the derived values are w_{0} = -1.02 {\pm} 0.17, {\Omega}_{m0} = 0.30{\pm}0.02, and H_{0} = 70.00 {\pm}0.60 km\,s^{-1}\,Mpc^{-1}. DETAILS: the current observations of SNe Ia are limited up to around z '2 and the number of SNe Ia events decreases toward higher redshifts. It may take a few Gyrs for a white dwarf binary to reach Chandrasekhar mass to explode. Due to these reasons, it will be difficult to investigate the variable nature of dark energy if we rely on SNe Ia only. CONCLUSIONS: The paramers that were constrained in the wCDM model improved on Ωm0 and w0 by adding the calibrated high-z sample galaxies. Furthermore, the improvement on the constraint contour of the w0 − wa plane in the CPL model is significant. Through this preliminary test with the calibrated high-z sample galaxies on the cosmological constraints, we present the potential application of CO data as an indicator to probe dark energy. Once the errors of individual CO measurements are reduced, tighter constraints can be obtained. Therefore, it is essential to increase the number of CO galaxies and improve the distance calibration so that constraints can become more
a. uncertain b. irregular c. insignificant d. reliable.
a. uncertain b. irregular c. insignificant d. reliable.
Q46. arXiv:1902.07730 [astro-ph.HE]: Pulsar Radio Emission Mechanism: Radio Nanoshots as a Low Frequency Afterglow of Relativistic Magnetic Reconnection. Alexander Philippov, Dmitri A. Uzdensky, Anatoly Spitkovsky, Benoît Cerutti, (Submitted on 20 Feb 2019): ABSTRACT: In this Letter we propose that coherent radio emission of Crab, other young energetic pulsars, and millisecond pulsars is produced in the magnetospheric current sheet beyond the light cylinder. We carry out global and local two-dimensional kinetic plasma simulations of reconnection to illustrate the coherent emission mechanism. Reconnection in the current sheet beyond the light cylinder proceeds in the very efficient plasmoid-dominated regime, and current layer gets fragmented into a dynamic chain of plasmoids which undergo successive coalescence. Mergers of sufficiently large plasmoids produce secondary perpendicular current sheets, which are also plasmoid-unstable. Collisions of plasmoids with each other and with the upstream magnetic field eject fast-magnetosonic waves, which propagate upstream across the background field and successfully escape from the plasma as electromagnetic waves that fall in the radio band. This model successfully explains many important features of the observed radio emission from Crab and other pulsars with high magnetic field at the light cylinder: phase coincidence with the high-energy emission, nano-second duration (nanoshots), and extreme instantaneous brightness of individual pulses. Results Reconnection starts as the tearing instability breaks up the current layer into a chain of plasmoids. As these primary plasmoids move along the sheet, secondary current sheets between them become sufficiently elongated and also become unstable, yielding a hierarchical fragmented structure (see Figure 2a for the snapshot of magnetic field lines and plasma density). Over time, plasmoids grow and merge into larger ones. Current sheets perpendicular to the main current sheet form between sufficiently large merging plasmoids. These sheets also become unstable to secondary tearing and form secondary plasmoids as shown in the density map in Figure 2b. Both small plasmoids in the main sheet and plasmoids in the secondary perpendicular current sheets can reach relativistic velocities. As they merge with each other or collide with the upstream magnetic field ( as is the case for plasmoids in secondary perpendicular current sheets), coherent time-dependent currents are generated at the interface and launch a powerful EM wave that lasts until the merger is complete. These waves are fast magnetosonic waves, which in the high-σ limit become vacuum EM waves.
a. Sonic waves b. EM waves c. plasmoids d. velocities.
Q47. arXiv:1902.07943 [astro-ph.HE]: The Energy Sources of Superluminous Supernovae. S. Q. Wang, L. J. Wang, Z. G. Dai: (Submitted on 21 Feb 2019): ABSTRACT: Supernovae (SNe) are the most brilliant optical stellar-class explosions. Over the past two decades, several optical transient survey projects discovered more than ∼100 so-called superluminous supernovae (SLSNe) whose peak luminosities and radiated energy are ≳7× 10^43erg s−1 and ≳ 10^51 erg, at least an order of magnitude larger than that of normal SNe. According to their optical spectra features, SLSNe have been split into two broad categories of type I that are hydrogen-deficient and type II that are hydrogen-rich. Investigating and determining the energy sources of SLSNe would be of outstanding importance for understanding the stellar evolution and explosion mechanisms. The energy sources of SLSNe can be determined by analyzing their light curves (LCs) and spectra. The most prevailing models accounting for the SLSN LCs are the 56Ni cascade decay model, the magnetar spin-down model, the ejecta-CSM interaction model, and the jet-ejecta interaction model. In this \textit{review}, we present several energy-source models and their different combinations. INTRODUCTION: Supernovae (SNe) are believed to be violent explosions of massive stars or white dwarfs. Determining the energy sources powering the LCs of SLSNe is be of outstanding importance for understandingthe stellar evolutionand explosion mechanisms.We can concludethat the LCs of most ordinary SNe must be powered by 56Ni cascade decay and/or ionized hydrogen recombination. The 56Ni Model: When massive stars explode as Fe-core core-collapse SNe launch energetic shocks which can heat the stellar mantles to a temperature & 5 × 10^9 K. CONCLUSIONS: Although the most prevailing semi-analytic models can yield LCs that are in good agreement with the photometricobservations,their disadvantagesare obvious:neglecting the time- and space-dependent effect of optical opacity, the mixing effect, and the two/three-dimensional effect. Besides, some very luminousoptical transientshaving very bright peak luminosities (peak absolute magnitudes are. −20.5 mag) and very short rising time scales (. 10 days) cannot be well explained by any models mentioned above. More detailed modeling might provide more useful information and eventually determine their nature and their energy sources. Determining the energy sources of SLSNe requires more dedicated observations and theoretical studies. Radio and X-ray observations for the remnants of some SLSNe also help us to judge whether or not the LCs of SLSNe are powered by magnetars or the ejecta-CSM interactions or other complicated models. New sky-survey programs (the Zwicky Transient Facility (ZTF), Law et al. 2009) and the upcoming sky-survey programs (e.g., the Large Synoptic Survey Telescope (LSST), Ivezic et al. 2008; LSST Science Collaborations et al. 2009), would discover more nearby SLSNe and intense follow-up photometric and spectral observations for them would shed more light on the nature of these optical
a. data b. parameters c. transients d. features.
Q48 arXiv:1902.08156 [astro-ph.CO]: Optical analysis of a CMB cosmic string candidate. O. S. Sazhina, D. Scognamiglio, M.V. Sazhin, M. Capaccioli. (Submitted on 21 Feb 2019): ABSTRACT: The complexity of the cosmological scenario regarding cosmic strings (CSs) stands still in the way of a complete understanding. We describe here a promising strategy for the possible detection of these elusive physical entities. It is based on the search of strong gravitational lensing events in the location area of the CS candidate (CSc-1), which was declared in a previous work by CMB analysis. Using photometric and geometric criteria, we identified pairs of candidates of lensed galaxies (LGCs) in the "string field" (SF), which were then compared with the average density of background galaxy pairs in a set of "control fields" (CFs). We found an excess of 22% (per sq. deg.) of the LGCs in SF, which exceeds the estimated cosmic dispersion. We also found that the number of LGCs is in excess of 29.2% in the angular separation bin [ 8′′, 9′′]. Finally, we analysed the possibility of a preferred orientation of the line connecting the centres of the LGCs. The orientation is statistically significant for an angular separation bin [4′′,6′′]. Therefore, we found two "windows" for the preferred angular separation for LGCs along the possible CS. However, the confirmation of the gravitational lensing origin of our LGCs requires spectroscopic observations which seem to be justified by the present results. We plan to acquire their spectra as well as to continue the study of the spectral and morphological features of the LGCs in the CSc-1 field and to analyse the other CS-candidates using the same strategy. INTRODUCTION: The search for cosmic strings (CSs) is one of the intriguing problems of modern astronomy, cosmology, and particle physics. CSs are hypothetical one-dimensional objects at cosmological scales which, while predicted by the theory, have not yet been detected. Their “zoo” is quite rich. They can be purely topological entities (endless or infinite and closed loops), formed as a result of phase transitions in the vacuum stages of the expansion and cooling of the early universe, or hybrid topological and field configurations (for example, the “necklace”, a CS with monopoles at its ends and collections of such elements. There is also the possibility of fundamental F-strings and D-strings of cosmological sizes, which could be generated during highenergy interactions of the extra dimensions in the early universe. D=8πGµ/ c^2 Here µ is the total CS mass per unit length (linear density) which is proportional to the square root of the CS energy as (mstring/mPlanck)^2 = Gµ<< 1 (for GUT scale CS the energy will be 10^16GeV), G is the Newtonian gravitational constant, and c is the speed of the light. CONCLUSIONS: Even if no definitive conclusion can be drawn at this point, this study provides intriguing hints on the fact that CSc-1 might indeed be a cosmic string. A stronger test of the true gravitational nature of the lens candidates requires a spectroscopic investigation. But the experimentum crucis remains the detection of cuts in the outer isophotes of found resolved lens candidates. For this purpose, high angular resolution images of the lensed sources are in order.
a. sequence b. order c. hints d. collections.
Q49.arXiv:1905.06347 [astro-ph.SR]: Planetary Nebulae and How to Find Them: Color Identification in Big Broadband Surveys.George Vejar, Rodolfo Montez Jr., Margaret Morris, Keivan G. Stassun.(Submitted on 15 May 2019) :ABSTRACT: Planetary nebulae (PNe) provide tests of stellar evolution, can serve as tracers of chemical evolution in the Milky Way and other galaxies, and are also used as a calibrator of the cosmological distance ladder. Current and upcoming large scale photometric surveys have the potential to complete the census of PNe in our galaxy and beyond, but it is a challenge to disambiguate partially or fully unresolved PNe from the myriad other sources observed in these surveys. Here we carry out synthetic observations of nebular models to determine ugrizy color-color spaces that can successfully identify PNe among billions of other sources. As a primary result we present a grid of synthetic absolute magnitudes for PNe at various stages of their evolution, and we make comparisons with real PNe colors from the Sloan Digital Sky Survey. We find that the r−i versus g−r , and the r−i versus u−g , color-color diagrams show the greatest promise for cleanly separating PNe from stars, background galaxies, and quasars. Finally, we consider the potential harvest of PNe from upcoming large surveys. For example, for typical progenitor host star masses of 3 M⊙, we find that the Large Synoptic Survey Telescope (LSST) should be sensitive to virtually all PNe in the Magellanic Clouds with extinction up to AV of ∼ 5 mag; out to the distance of Andromeda, LSST would be sensitive to the youngest PNe (age less than ∼ 6800 yr) and with AV up to 1 mag. CONCLUSIONS: In this work we presented synthetic absolute magnitudes in the ugrizy filters of 13 PN models representing the evolution of a PN for a 3 M⊙ progenitor star over ∼5,000 years (Table 4). We have calculated the colors for various photometric aperture sizes to explore spatially resolved and unresolved cases. We showed that our model magnitudes and colors are consistent with real observations for both resolved and unresolved cases. We also showed that LSST will allow for the identification of many PNe in the Milky Way and neighbouring
a. confirmed b. Supported c. validated d. ascertained.
Q64. arXiv:1905.10767 [gr-qc]: Neutron stars in general relativity and scalar-tensor theory of gravity. F. J. Fattoyev. (Submitted on 26 May 2019): ABSTRACT: The masses and radii of neutron stars are discussed in general relativity and scalar-tensor theory of gravity and the differences are compared with the current uncertainties stemming from the nuclear equation of state in the relativistic mean-field framework. It is shown that astrophysical and gravitational waves observations of radii of neutron stars with masses M≲1.4 M⊙ constrain only the nuclear equation of state, and in particular the density dependence of the nuclear symmetry energy. Future observations of massive neutron stars may constrain the coupling parameters of the scalar-tensor theory provided that a general consensus on the dense nuclear matter equation of state is reached. INTRODUCTION: Neutron stars exhibit a strong curvature, and it is not yet clear whether gravitational field of such compact objects is fully described by GR. The structure of neutron stars is sensitive to the equation of state of cold, fully catalyzed, and neutron-rich matter. The matter inside neutron stars span many orders of magnitude in density leading to rich and exotic phases in their interiors. Conclusions: We would like to note that our work does not take into account the possibility that the core of neutron stars may have exotic degrees of freedom, such as hyperons, meson condensates, or quarks. In particular, the central density in neutron stars with M >~ 1.4M —for which spontaneous scalarization occurs—reaches nuclear densities of ρc >~ 2.5ρ0, where our knowledge of strong interaction is limited. Certainly there could still be a degeneracy between the scalar-tensor model of gravity and models of strong interaction at high densities. Much collaborative theoretical and observational efforts of both nuclear physics and gravitational physics community are therefore required on this a. Sonic waves b. EM waves c. plasmoids d. velocities.
Q47. arXiv:1902.07943 [astro-ph.HE]: The Energy Sources of Superluminous Supernovae. S. Q. Wang, L. J. Wang, Z. G. Dai: (Submitted on 21 Feb 2019): ABSTRACT: Supernovae (SNe) are the most brilliant optical stellar-class explosions. Over the past two decades, several optical transient survey projects discovered more than ∼100 so-called superluminous supernovae (SLSNe) whose peak luminosities and radiated energy are ≳7× 10^43erg s−1 and ≳ 10^51 erg, at least an order of magnitude larger than that of normal SNe. According to their optical spectra features, SLSNe have been split into two broad categories of type I that are hydrogen-deficient and type II that are hydrogen-rich. Investigating and determining the energy sources of SLSNe would be of outstanding importance for understanding the stellar evolution and explosion mechanisms. The energy sources of SLSNe can be determined by analyzing their light curves (LCs) and spectra. The most prevailing models accounting for the SLSN LCs are the 56Ni cascade decay model, the magnetar spin-down model, the ejecta-CSM interaction model, and the jet-ejecta interaction model. In this \textit{review}, we present several energy-source models and their different combinations. INTRODUCTION: Supernovae (SNe) are believed to be violent explosions of massive stars or white dwarfs. Determining the energy sources powering the LCs of SLSNe is be of outstanding importance for understandingthe stellar evolutionand explosion mechanisms.We can concludethat the LCs of most ordinary SNe must be powered by 56Ni cascade decay and/or ionized hydrogen recombination. The 56Ni Model: When massive stars explode as Fe-core core-collapse SNe launch energetic shocks which can heat the stellar mantles to a temperature & 5 × 10^9 K. CONCLUSIONS: Although the most prevailing semi-analytic models can yield LCs that are in good agreement with the photometricobservations,their disadvantagesare obvious:neglecting the time- and space-dependent effect of optical opacity, the mixing effect, and the two/three-dimensional effect. Besides, some very luminousoptical transientshaving very bright peak luminosities (peak absolute magnitudes are. −20.5 mag) and very short rising time scales (. 10 days) cannot be well explained by any models mentioned above. More detailed modeling might provide more useful information and eventually determine their nature and their energy sources. Determining the energy sources of SLSNe requires more dedicated observations and theoretical studies. Radio and X-ray observations for the remnants of some SLSNe also help us to judge whether or not the LCs of SLSNe are powered by magnetars or the ejecta-CSM interactions or other complicated models. New sky-survey programs (the Zwicky Transient Facility (ZTF), Law et al. 2009) and the upcoming sky-survey programs (e.g., the Large Synoptic Survey Telescope (LSST), Ivezic et al. 2008; LSST Science Collaborations et al. 2009), would discover more nearby SLSNe and intense follow-up photometric and spectral observations for them would shed more light on the nature of these optical
a. data b. parameters c. transients d. features.
Q48 arXiv:1902.08156 [astro-ph.CO]: Optical analysis of a CMB cosmic string candidate. O. S. Sazhina, D. Scognamiglio, M.V. Sazhin, M. Capaccioli. (Submitted on 21 Feb 2019): ABSTRACT: The complexity of the cosmological scenario regarding cosmic strings (CSs) stands still in the way of a complete understanding. We describe here a promising strategy for the possible detection of these elusive physical entities. It is based on the search of strong gravitational lensing events in the location area of the CS candidate (CSc-1), which was declared in a previous work by CMB analysis. Using photometric and geometric criteria, we identified pairs of candidates of lensed galaxies (LGCs) in the "string field" (SF), which were then compared with the average density of background galaxy pairs in a set of "control fields" (CFs). We found an excess of 22% (per sq. deg.) of the LGCs in SF, which exceeds the estimated cosmic dispersion. We also found that the number of LGCs is in excess of 29.2% in the angular separation bin [ 8′′, 9′′]. Finally, we analysed the possibility of a preferred orientation of the line connecting the centres of the LGCs. The orientation is statistically significant for an angular separation bin [4′′,6′′]. Therefore, we found two "windows" for the preferred angular separation for LGCs along the possible CS. However, the confirmation of the gravitational lensing origin of our LGCs requires spectroscopic observations which seem to be justified by the present results. We plan to acquire their spectra as well as to continue the study of the spectral and morphological features of the LGCs in the CSc-1 field and to analyse the other CS-candidates using the same strategy. INTRODUCTION: The search for cosmic strings (CSs) is one of the intriguing problems of modern astronomy, cosmology, and particle physics. CSs are hypothetical one-dimensional objects at cosmological scales which, while predicted by the theory, have not yet been detected. Their “zoo” is quite rich. They can be purely topological entities (endless or infinite and closed loops), formed as a result of phase transitions in the vacuum stages of the expansion and cooling of the early universe, or hybrid topological and field configurations (for example, the “necklace”, a CS with monopoles at its ends and collections of such elements. There is also the possibility of fundamental F-strings and D-strings of cosmological sizes, which could be generated during highenergy interactions of the extra dimensions in the early universe. D=8πGµ/ c^2 Here µ is the total CS mass per unit length (linear density) which is proportional to the square root of the CS energy as (mstring/mPlanck)^2 = Gµ<< 1 (for GUT scale CS the energy will be 10^16GeV), G is the Newtonian gravitational constant, and c is the speed of the light. CONCLUSIONS: Even if no definitive conclusion can be drawn at this point, this study provides intriguing hints on the fact that CSc-1 might indeed be a cosmic string. A stronger test of the true gravitational nature of the lens candidates requires a spectroscopic investigation. But the experimentum crucis remains the detection of cuts in the outer isophotes of found resolved lens candidates. For this purpose, high angular resolution images of the lensed sources are in order.
a. sequence b. order c. hints d. collections.
Q49.arXiv:1905.06347 [astro-ph.SR]: Planetary Nebulae and How to Find Them: Color Identification in Big Broadband Surveys.George Vejar, Rodolfo Montez Jr., Margaret Morris, Keivan G. Stassun.(Submitted on 15 May 2019) :ABSTRACT: Planetary nebulae (PNe) provide tests of stellar evolution, can serve as tracers of chemical evolution in the Milky Way and other galaxies, and are also used as a calibrator of the cosmological distance ladder. Current and upcoming large scale photometric surveys have the potential to complete the census of PNe in our galaxy and beyond, but it is a challenge to disambiguate partially or fully unresolved PNe from the myriad other sources observed in these surveys. Here we carry out synthetic observations of nebular models to determine ugrizy color-color spaces that can successfully identify PNe among billions of other sources. As a primary result we present a grid of synthetic absolute magnitudes for PNe at various stages of their evolution, and we make comparisons with real PNe colors from the Sloan Digital Sky Survey. We find that the r−i versus g−r , and the r−i versus u−g , color-color diagrams show the greatest promise for cleanly separating PNe from stars, background galaxies, and quasars. Finally, we consider the potential harvest of PNe from upcoming large surveys. For example, for typical progenitor host star masses of 3 M⊙, we find that the Large Synoptic Survey Telescope (LSST) should be sensitive to virtually all PNe in the Magellanic Clouds with extinction up to AV of ∼ 5 mag; out to the distance of Andromeda, LSST would be sensitive to the youngest PNe (age less than ∼ 6800 yr) and with AV up to 1 mag. CONCLUSIONS: In this work we presented synthetic absolute magnitudes in the ugrizy filters of 13 PN models representing the evolution of a PN for a 3 M⊙ progenitor star over ∼5,000 years (Table 4). We have calculated the colors for various photometric aperture sizes to explore spatially resolved and unresolved cases. We showed that our model magnitudes and colors are consistent with real observations for both resolved and unresolved cases. We also showed that LSST will allow for the identification of many PNe in the Milky Way and neighbouring
a. Stars b. Quasars c. galaxies d. supernova
Q50. arXiv:1905.06530 [astro-ph.EP]: The Pressure and Temperature Limits of Likely Rocky Exoplanets. Cayman T. Unterborn, Wendy R. Panero. (Submitted on 16 May 2019): ABSTRACT: The interior composition of exoplanets is not observable, limiting our direct knowledge of their structure, composition, and dynamics. Recently described observational trends suggest that rocky exoplanets, that is, planets without significant volatile envelopes, are likely limited to < 1.5 Earth radii. We show that given this likely upper limit in the radii of purely-rocky super-Earth exoplanets, the maximum expected core-mantle boundary pressure and adiabatic temperature is relatively moderate, 630 GPa and 5000 K, while the maximum central core pressure varies between 1.5 and 2.5 TPa. We further find that for planets with radii less than 1.5 Earth radii, core-mantle boundary pressure and adiabatic temperature are mostly a function of planet radius and insensitive to planet structure. The pressures and temperatures of rocky exoplanet interiors, then, are less than those explored in recent shock-compression experiments, ab-initio calculations, and planetary dynamical studies. We further show that the extrapolation of relevant equations of state does not introduce significant uncertainties in the structural models of these planets. Mass-radius models are more sensitive to bulk composition than any uncertainty in the equation of state, even when extrapolated to TPa
a. temperatures b. pressures c. experiments d. exoplanets.
Q51. arXiv:1905.06674 [astro-ph.HE]: Spectrum and fraction of cosmic ray positrons: results of the anomalous diffusion approach. ikolay Volkov, Anatoly Lagutin, Alexander Tyumentsev. (Submitted on 16 May 2019): ABSTRACT: We present the results of new calculations of the energy spectra of cosmic ray electrons, positrons and also positron fraction under assumption that both electrons and positrons are generated by the same Galactic sources, which accelerate particles with same power-law injection spectral index p. The value of the injection index p≈2.85 retrieved in our works from the analysis of the observed CR spectra has been used. The propagation of particles through the highly non-homogeneous interstellar medium has been described by the anomalous diffusion model. We show that proposed approach allows the self-consistent description of the recent AMS-02 data. In contrast to the conclusion made by AMS-02 collaboration about the different origin of the high-energy positrons and electrons, our results demonstrate that the differing behavior of spectral indices of electrons and positrons with energy can be described under the assumption that both positrons and electrons have common Galactic sources. Our prediction that the e + to total e− + e+ ratio reaches a constant value for E ≫200 GeV is a. temperatures b. pressures c. experiments d. exoplanets.
a. confirmed b. Supported c. validated d. ascertained.
Q52. arXiv:1905.07565 [gr-qc]: Probing dark matter and dark energy through Gravitational Time Advancement. Samrat Ghosh, Arunava Bhadra, Amitabha Mukhopadhyay. (Submitted on 18 May 2019): ABSTRACT: The expression of gravitational time advancement (negative time delay) for particles with non-zero mass in Schwarzschild geometry has been obtained. The influences of the gravitational field that describes the observed rotation curves of spiral galaxies and that of dark energy (in the form of cosmological constant) on time advancement of particles have also been studied. The present findings suggest that in presence of dark matter gravitational field the time advancement may take place irrespective of gravitational field of the observer, unlike the case of pure Schwarzschild geometry where gravitational time advancement takes place only when the observer is situated at stronger gravitational field compare to the gravitational field encountered by the particle during its journey. When applied to the well known case of SN 1987a, it is found that the net time delay of a photon/gravitational wave is much smaller than quoted in the literature. In the presence of dark matter field, the photon and neutrinos from SN 1987a should have been suffered gravitational time advancement rather than the delay. CONCLUSIONS: Subsequently we study the effect of dark matter and dark energy on gravitational time advancement. It is found that dark matter leads to larger gravitational time advancement whereas dark energy always produces time delay. We have demonstrated how the present findings can be tested in a real observational situation. Finally after applying our findings to neutrinos (and photons) from SN 1987, we have shown that the net time delay of a photon/gravitational wave is much smaller than quoted in the prevailing literature due to GTA effect. Recently ICECUBE experiment and Fermi telescope detected neutrinos and photons within a short time period from BLAZER TXS 0506+056. More such kind of detection from various sources are expected in near feature. The present findings will have direct application to test various underlying physics related issues of GR and particle physics from the measurement of the difference in time of arrivals of photons/gravitational wave and neutrinos from such astrophysical
a. differences b. criteria c. sources d. findings
Q53. arXiv:1905.08012 [gr-qc]: Testing general relativity with supermassive black holes using X-ray reflection spectroscopy. Askar B. Abdikamalov, Dimitry Ayzenberg, Cosimo Bambi, Sourabh Nampalliwar, Ashutosh Tripathi, Jelen Wong, Yerong Xu, Jinli Yan, Yunfeng Yan, Yuchan Yang. (Submitted on 20 May 2019): ABSTRACT: In this paper, we review our current efforts to test General Relativity in the strong field regime by studying the reflection spectrum of supermassive black holes. So far we have analyzed 11 sources with observations of NuSTAR, Suzaku, Swift, and XMM-Newton. Our results are consistent with general relativity, according to which the spacetime metric around astrophysical black holes should be well approximated by the Kerr solution. We discuss the systematic uncertainties in our model and we present a preliminary study on the impact of some of them on the measurement of the spacetime metric. CONCLUDING REMARKS: Thanks to a new generation of observational facilities, it is today possible to start testing Einstein’s Theory of General Relativity in the strong field regime and black hole tests with electromagnetic and gravitational wave techniques are becoming a hot topic among both the astrophysics and the theoretical physics communities. The results of our group using X-ray reflection spectroscopy are currently the only constraints from an electromagnetic method on the spacetime metric near black holes, and in this review paper we have summarized the state of the art of the measurements of supermassive black holes. Our current work is devoted to improve these results by looking for more suitable sources/data and by upgrading our theoretical model to reduce systematic
a. certainties b. uncertainties c. errors d. sources
Q54. arXiv:1905.08113 [gr-qc]: Introduction to Gauge Theory of Gravitation. Wytler Cordeiro dos Santos. (Submitted on 20 May 2019) :ABSTRACT: The fundamental interactions of nature, the electroweak and the quantum chromodynamics, are described in the Standard Model by the Gauge Theory under internal symmetries that maintain the invariance of the functional action. The fundamental interaction of gravitation is very well described by Einstein's General Relativity in a Riemannian spacetime metric, but General Relativity has been over time a gravitational field theory apart from the Standard Model. The theory of Gauge allows under symmetries of the group of Poincaré to impose invariances in the functional of the action of the spinor field that result in the gravitational interaction with the fermions. In this approach the gravitational field, besides being described by the equation similar to General Relativity, also brings a spin-gravitational interaction in a Riemann-Cartan spacetime. The Einstein-Cartan theory of gravitation in spacetime with torsion adds to gravitation the existence of a weak interaction between the gravitational field and the fermionic matter. Calculations and discussions have shown that the density of matter containing fermions with intrinsic angular momentum in units of ~ 2 , must be of the order of 1047 g/cm^3 for electrons and 1054 g/cm^3 for neutrons, so that there was the possibility of estimating significant deviations from the predictions of General Relativity. To have an idea of these dimensions, compare the matter density of a neutron star that is of the order of 1016 g/cm^3.Certainly for such high densities, the expected effects that fermionic matter can twist the spacetime must be for extreme conditions in the gravitational collapses approached in cosmology and in the big bang. There are also expectations of such spin-torsion effects occurring on the Planck scale where quantum gravity processes begin to be
a. relevant b. specific c. assertive d. irrelevant.
Q55. arXiv:1905.07736 [physics. Optics]: Slow and fast light enhanced light drag in a moving microcavity. Tian Qin, Jianfan Yang, Fangxing Zhang, Yao Chen, Dongyi Shen, Wei Liu, Lei Chen, Yuanlin Zheng, Xianfeng Chen, Wenjie Wan: (Submitted on 19 May 2019): ABSTRACT: Fizeau experiment, inspiring Einstein's special theory of relativity, reveals a small dragging effect of light inside a moving medium. Dispersion can enhance such light drag according to Lorentz's predication. Here we experimentally demonstrate slow and fast light enhanced light drag in a moving optical microcavity through stimulated Brillouin scattering induced transparency and absorption. The strong dispersion provides an enhancement factor up to ~10^4, greatly reducing the system size down to the micro-meter range. These results may offer a unique platform for a compact, integrated solution to motion sensing and ultrafast signal processing applications. DETAILS: Previously, strong dispersion enhanced light drag has been observed in highly dispersive media such as atomic vapours, cold atoms and rare-earth doped crystals, where ultra-narrow linewidth atomic resonances can enormously enhance the drag effect up to∼ 105 times as compared to low dispersive media like water or glass, greatly reducing the system sizes down to the milli-meter scale. CONCLUSIONS: In summary, we have theoretically and experimentally exam Lorentz's prediction of dispersion enhanced Fresnel light drag in both slow and fast light configurations. Compared with prior works, our new platform is implemented on a solid-state microcavity with a micro-meter dimension and a speed sensitivity down to cm/s, thanks to a ∼ 104 dispersion enhancement factor introduced by the stimulated Brillouin scattering process inside the optical microcavity. Both slow and fast light enhanced light dragging effects have been demonstrated with a flexible tunability from active pumping or detuning, paving a way for related and highly demanded applications in inertial, gyroscopic motional sensing. The demonstrated compact system also offers a new avenue for all-optical and on-chip photonics
a. devices b. arrangements c. applications d. setups
Q56. arXiv:1905.07847 [physics. plasm-ph]: Positron beam acceleration driven by laser-accelerated electron beam. Zhangli Xu, Baifei Shen, Jiancai Xu, Tongjun Xu, Lingang Zhang, Shun Li, Liangliang Ji, Zhizhan Xu. (Submitted on 20 May 2019): ABSTRACT: A positron beam, produced in copper target based on laser-accelerated energetic electrons, is accelerated from a few MeVs to several hundred MeV's in strong longitudinal electric field induced by the co-propagating high-density electron beam. This new acceleration scheme for positron beams is demonstrated by two-dimensional particle-in-cell simulation and Monte-Carlo code. The electron beam after passing through the copper target keeps its high density ~10^17cm^-3 for 0.7 m propagation distance, with the guiding from an external longitudinal magnetic field of 30 T and provides a strong acceleration field of GV/m for the positrons. Simulation results indicate that a positron beam with an initial Maxwellian-energy-spectrum of Tp = 24.1 MeV is accelerated to quasi-monoenergetic peaks up to 796.5 MeV with energy spread of 18.7% when 10 PW laser pulse is employed. The angular divergence of the positron beam is 2.3 m-rad and the charge is 12 pC. This proposed method resolves the creation, injection and acceleration of positrons in a single set-up, which offers a new way to accelerate high-energy positrons for potential modest-sized all-optical electron-positron colliders. :CONCLUSION:, we presented a simple novel scheme for GeV-level positron acceleration based on laser-accelerated high-density electron beam. The positrons created from routine BH process in copper target get high-energy gain from longitudinal electric field induced by co-propagating electrons after the copper target. Series of simulations (EPOCH-Geant4-EPOCH) confirmed that positrons with an initial Maxwellian energy distribution with temperature of Tp = 24.1 MeV are able to be accelerated to 796.5 MeV with an energy spread of 18.7% and a small angular divergence of 2.3 m-rad (FWHM). This acceleration method is able to provide high-energy positron beam with narrow energy spread and offers a new concept towards modest-sized all-optical electron-positron
Q61. arXiv:1905.09842 [astro-ph.GA]: Simulating cosmological substructure in the solar neighbourhood. Christine M. Simpson, Ignacio Gargiulo, Facundo A. Gómez, Robert J. J. Grand, Nicolás Maffione, Andrew P. Cooper, Alis J. Deason, Carlos Frenk, John Helly, Federico Marinacci, Rüdiger Pakmor. (Submitted on 23 May 2019): ABSTRACT: We explore the predictive power of cosmological, hydrodynamical simulations for stellar phase space substructure and velocity correlations with the Auriga simulations and Aurigaia mock-Gaia catalogues. We show that at the solar circle the Auriga simulations commonly host phase space structures in the stellar component that have constant orbital energies and arise from accreted subhaloes. These structures can persist for a few Gyrs, even after coherent streams in position space have been erased. We also explore velocity two-point correlation functions and find this diagnostic is not deterministic for particular clustering patterns in phase space. Finally, we explore these structure diagnostics with the Aurigaia catalogues and show that the current catalogues have the ability to recover some structures in phase space but careful consideration is required to separate physical structures from numerically seeded structures. CONCLUSIONS: Prominent substructures with high velocities points toward their importance in determining the Galactic mass from high-velocity stars. The gaia mission has expanded our understanding of the MW’s accretion history. Cosmological simulations will be an important tool for interpreting these data and this letter has provided the first proof of concept of this strategy. We have described notable caveats to working with mock data, but we anticipate further improvements to simulations and mock generation methods will result in a robust tool for theoretical interpretation of the mission’s data in this
a. certainties b. uncertainties c. errors d. sources
Q54. arXiv:1905.08113 [gr-qc]: Introduction to Gauge Theory of Gravitation. Wytler Cordeiro dos Santos. (Submitted on 20 May 2019) :ABSTRACT: The fundamental interactions of nature, the electroweak and the quantum chromodynamics, are described in the Standard Model by the Gauge Theory under internal symmetries that maintain the invariance of the functional action. The fundamental interaction of gravitation is very well described by Einstein's General Relativity in a Riemannian spacetime metric, but General Relativity has been over time a gravitational field theory apart from the Standard Model. The theory of Gauge allows under symmetries of the group of Poincaré to impose invariances in the functional of the action of the spinor field that result in the gravitational interaction with the fermions. In this approach the gravitational field, besides being described by the equation similar to General Relativity, also brings a spin-gravitational interaction in a Riemann-Cartan spacetime. The Einstein-Cartan theory of gravitation in spacetime with torsion adds to gravitation the existence of a weak interaction between the gravitational field and the fermionic matter. Calculations and discussions have shown that the density of matter containing fermions with intrinsic angular momentum in units of ~ 2 , must be of the order of 1047 g/cm^3 for electrons and 1054 g/cm^3 for neutrons, so that there was the possibility of estimating significant deviations from the predictions of General Relativity. To have an idea of these dimensions, compare the matter density of a neutron star that is of the order of 1016 g/cm^3.Certainly for such high densities, the expected effects that fermionic matter can twist the spacetime must be for extreme conditions in the gravitational collapses approached in cosmology and in the big bang. There are also expectations of such spin-torsion effects occurring on the Planck scale where quantum gravity processes begin to be
a. relevant b. specific c. assertive d. irrelevant.
Q55. arXiv:1905.07736 [physics. Optics]: Slow and fast light enhanced light drag in a moving microcavity. Tian Qin, Jianfan Yang, Fangxing Zhang, Yao Chen, Dongyi Shen, Wei Liu, Lei Chen, Yuanlin Zheng, Xianfeng Chen, Wenjie Wan: (Submitted on 19 May 2019): ABSTRACT: Fizeau experiment, inspiring Einstein's special theory of relativity, reveals a small dragging effect of light inside a moving medium. Dispersion can enhance such light drag according to Lorentz's predication. Here we experimentally demonstrate slow and fast light enhanced light drag in a moving optical microcavity through stimulated Brillouin scattering induced transparency and absorption. The strong dispersion provides an enhancement factor up to ~10^4, greatly reducing the system size down to the micro-meter range. These results may offer a unique platform for a compact, integrated solution to motion sensing and ultrafast signal processing applications. DETAILS: Previously, strong dispersion enhanced light drag has been observed in highly dispersive media such as atomic vapours, cold atoms and rare-earth doped crystals, where ultra-narrow linewidth atomic resonances can enormously enhance the drag effect up to∼ 105 times as compared to low dispersive media like water or glass, greatly reducing the system sizes down to the milli-meter scale. CONCLUSIONS: In summary, we have theoretically and experimentally exam Lorentz's prediction of dispersion enhanced Fresnel light drag in both slow and fast light configurations. Compared with prior works, our new platform is implemented on a solid-state microcavity with a micro-meter dimension and a speed sensitivity down to cm/s, thanks to a ∼ 104 dispersion enhancement factor introduced by the stimulated Brillouin scattering process inside the optical microcavity. Both slow and fast light enhanced light dragging effects have been demonstrated with a flexible tunability from active pumping or detuning, paving a way for related and highly demanded applications in inertial, gyroscopic motional sensing. The demonstrated compact system also offers a new avenue for all-optical and on-chip photonics
a. devices b. arrangements c. applications d. setups
Q56. arXiv:1905.07847 [physics. plasm-ph]: Positron beam acceleration driven by laser-accelerated electron beam. Zhangli Xu, Baifei Shen, Jiancai Xu, Tongjun Xu, Lingang Zhang, Shun Li, Liangliang Ji, Zhizhan Xu. (Submitted on 20 May 2019): ABSTRACT: A positron beam, produced in copper target based on laser-accelerated energetic electrons, is accelerated from a few MeVs to several hundred MeV's in strong longitudinal electric field induced by the co-propagating high-density electron beam. This new acceleration scheme for positron beams is demonstrated by two-dimensional particle-in-cell simulation and Monte-Carlo code. The electron beam after passing through the copper target keeps its high density ~10^17cm^-3 for 0.7 m propagation distance, with the guiding from an external longitudinal magnetic field of 30 T and provides a strong acceleration field of GV/m for the positrons. Simulation results indicate that a positron beam with an initial Maxwellian-energy-spectrum of Tp = 24.1 MeV is accelerated to quasi-monoenergetic peaks up to 796.5 MeV with energy spread of 18.7% when 10 PW laser pulse is employed. The angular divergence of the positron beam is 2.3 m-rad and the charge is 12 pC. This proposed method resolves the creation, injection and acceleration of positrons in a single set-up, which offers a new way to accelerate high-energy positrons for potential modest-sized all-optical electron-positron colliders. :CONCLUSION:, we presented a simple novel scheme for GeV-level positron acceleration based on laser-accelerated high-density electron beam. The positrons created from routine BH process in copper target get high-energy gain from longitudinal electric field induced by co-propagating electrons after the copper target. Series of simulations (EPOCH-Geant4-EPOCH) confirmed that positrons with an initial Maxwellian energy distribution with temperature of Tp = 24.1 MeV are able to be accelerated to 796.5 MeV with an energy spread of 18.7% and a small angular divergence of 2.3 m-rad (FWHM). This acceleration method is able to provide high-energy positron beam with narrow energy spread and offers a new concept towards modest-sized all-optical electron-positron
a. collisions b. scattering c. dispersion d. colliders.
Q57.arXiv:1905.08250 [astro-ph.HE]: Ultra High Energy Cosmic Rays and the Highest Energies Universe. Roberto Aloisio. (Submitted on 20 May 2019):ABSTRACT: We will discuss the main relevant aspects of the physics of ultra high energy cosmic rays. After a short recap of the experimental evidences, we will review theoretical models aiming at describing the sources of these extremely energetic particles opening a window on the highest energies universe. We will discuss the production of secondary particles and the possible tests of new physics that ultra high energy cosmic rays could provide. DETAILS: The study of the highest energies universe is inextricably tied to Ultra High Energy Cosmic Rays (UHECR) the highest energy particles ever observed with energies ranging from 10^17 eV up to energies in excess 10^20 eV. The observation of UHECR brings informations about the most energetic events in the universe and it could unveil new physical phenomena at energetic regimes not accessible otherwise. New physics: the super heavy dark matter hypothesis. The extreme energies of UHECR, as high as 1011 GeV, eleven orders of magnitude above the proton mass and ”only” eight below the Planck mass, are a unique workbench to probe new ideas, models and theories which show their effects at energies much larger than those ever obtained, or obtainable in the future, in accelerator experiments. An interesting class of exotic models that can be tested trough UHECR are top-down models for the production of these extremely energetic particles. CONCLUSIONS: After the first detection of astrophysical neutrinos at energies below few ×1015 eV by the IceCube collaboration [27], the study of HE and UHE neutrinos attracted a renewed interest. The observations of IceCube, being at relatively low energy, can be only marginally explained in the framework of cosmogenic neutrinos coming from UHECR interactions, also given the large uncertainties on the EBL background at high red-shift [17]. At high energies (E ≥ 1018) neutrino production is critically related with the mass composition of UHECR and with cosmological evolution of
a. collaborations b. sources c. experiments d. neutrinos
Q58. arXiv:1905.08262 [astro-ph.CO]: Cosmological Information Contents on the Light-Cone. Jaiyul Yoo (1), Ermis Mitsou (1), Nastassia Grimm (1), Ruth Durrer (2), Alexandre Refregier (3) ((1) Zürich, (2) Geneva, (3) ETH Zürich): (Submitted on 20 May 2019): ABSTRACT: We develop a theoretical framework to describe the cosmological observables on the past light cone such as the luminosity distance, weak lensing, galaxy clustering, and the cosmic microwave background anisotropies. We consider that all the cosmological observables include not only the background quantity, but also the perturbation quantity, and they are subject to cosmic variance, which sets the fundamental limits on the cosmological information that can be derived from such observables, even in an idealized survey with an infinite number of observations. To quantify the maximum cosmological information content, we apply the Fisher information matrix formalism and spherical harmonic analysis to cosmological observations, in which the angular and the radial positions of the observables on the light cone carry different information. We discuss the maximum cosmological information that can be derived from five different observables: (1) type Ia supernovae, (2) cosmic microwave background anisotropies, (3) weak gravitational lensing, (4) local baryon density, and (5) galaxy clustering. We compare our results with the cosmic variance obtained in the standard approaches, which treat the light cone volume as a cubic box of simultaneity. We discuss implications of our formalism and ways to overcome the fundamental limit. Discussion and Summary: In this paper, we have developed a theoretical framework to describe cosmological observables on the light cone and we have derived the Fisher information matrix to quantify the maximum cosmological information obtainable from cosmological observables such as the luminosity distance, weak gravitational lensing, galaxy clustering, and the cosmic microwave background (CMB) anisotropies. As all the cosmological observables contain perturbations, their measurements are subject to the cosmic variance, and in computing the cosmic variance, we have taken into account that the survey geometry is the light cone
a. simultaneity b. baryon density c. Matrix d. volume.
a. simultaneity b. baryon density c. Matrix d. volume.
Q59. arXiv:1905.08361 [astro-ph.SR]: Introduction to the physics of solar eruptions and their space weather impact. Vasilis Archontis, Loukas Vlahos.(Submitted on 20 May 2019): ABSTRACT: The physical processes, which drive powerful solar eruptions, play an important role in our understanding of the Sun-Earth connection. In this Special Issue, we firstly discuss how magnetic fields emerge from the solar interior to the solar surface, to build up active regions, which commonly host large-scale coronal disturbances, such as coronal mass ejections (CMEs). Then, we discuss the physical processes associated with the driving and triggering of these eruptions, the propagation of the large-scale magnetic disturbances through interplanetary space and the interaction of CMEs with Earth's magnetic field. The acceleration mechanisms for the solar energetic particles related to explosive phenomena (e.g. flares and/or CMEs) in the solar corona are also discussed. The main aim of this Issue, therefore, is to encapsulate the present state-of-the-art in research related to the genesis of solar eruptions and their space-weather implications. Summary In this Special Issue we present the ongoing research, the main advances and the open questions shaping our understanding of solar eruptions and their Space Weather impact. The phenomena associated with Space Weather are a paradigm for many astrophysical plasmas. Many of the problems addressed in this issue are important space physics problems on magnetic stability, propagation of heliospheric disturbances and their interaction with planetary magnetospheres. The topics presented in this issue include contributions from the three tenets of basic research (observations, theory and modelling) and extend into the largely unexplored areas (in Helio-physics) of research-to-operations issues, including forecasting tools and assessment, forecasting and now-casting, near-real time modelling and its
a. challenges b. outlook c. impact d. stability.
a. challenges b. outlook c. impact d. stability.
Q60. arXiv:1905.08626 [gr-qc]: Quantum Fluctuations at the Planck Scale. Fulvio Melia. (Submitted on 17 May 2019) :ABSTRACT: The recently measured cut-off, k_min=[4.34(+/-)0.50]/r_cmb (with r_cmb the comoving distance to the last scattering surface), in the fluctuation spectrum of the cosmic microwave background, appears to disfavour slow-roll inflation and the associated transition of modes across the horizon. We show in this Letter that k_min instead corresponds to the first mode emerging out of the Planck domain into the semi-classical universe. The required scalar-field potential is exponential, though not inflationary, and satisfies the zero active mass condition, rho_phi+3p_phi=0. Quite revealingly, the observed amplitude of the temperature anisotropies requires the quantum fluctuations in phi to have classicalized at ~3.5x10^15 GeV, consistent with the energy scale in grand unified theories. Such scalar-field potentials are often associated with Kaluza-Klein cosmologies, string theory and even supergravity. CONCLUSIONS: All of the numen QFs with a given k have the same phase because they emerge from the Planck domain at a fixed time tk. The numen mechanism is a little simpler because it requires fewer steps and, at the same time, appears to avoid at least some of the difficulties faced by conventional inflation. Our final conclusion from this discussion is that if the early universe was indeed dominated by a single numen field, then we know its potential quite precisely. Exponential forms such as these are well motivated in Kaluza-Klein cosmologies, string theories, and even
a. Planck domain b. unified theories c. supergravity d. string theories
ANSWERS: Q1a. Q2d. Q3c. Q4b. Q5a. Q6c. Q7b. Q8b. Q9c. Q10b. Q11a. Q12c. Q13a. Q14b. Q15b. Q16a. Q17d. Q18c. Q19c. Q20b. Q21b. Q22c. Q23a. Q24d. Q25c. Q26a. Q27b. Q28c. Q29b. Q30b. Q31c. Q32b. Q33d. Q34a. Q35c. Q36a. Q37b. Q38c. Q39a. Q40d. Q41c. Q42b. Q43a. Q44b. Q45d. Q46b. Q47c. Q48b. Q49c. Q50b. Q51a. Q52c. Q53b. Q54a. Q55c. Q56d. Q57b. Q58d. Q59a. Q60c.
a. Planck domain b. unified theories c. supergravity d. string theories
ANSWERS: Q1a. Q2d. Q3c. Q4b. Q5a. Q6c. Q7b. Q8b. Q9c. Q10b. Q11a. Q12c. Q13a. Q14b. Q15b. Q16a. Q17d. Q18c. Q19c. Q20b. Q21b. Q22c. Q23a. Q24d. Q25c. Q26a. Q27b. Q28c. Q29b. Q30b. Q31c. Q32b. Q33d. Q34a. Q35c. Q36a. Q37b. Q38c. Q39a. Q40d. Q41c. Q42b. Q43a. Q44b. Q45d. Q46b. Q47c. Q48b. Q49c. Q50b. Q51a. Q52c. Q53b. Q54a. Q55c. Q56d. Q57b. Q58d. Q59a. Q60c.
TRUWIZ 120b
trusciencetrutechnology@blogspot.com
Volume 2019, Dated: 9 September 2019
[Initiated by Prof. Dr. K. Lakshmi Narayana]
In Memory of
Late Professor Kotcherlakota Rangadhama Rao
D.Sc. (Madras). D.Sc. (London).
(Birth on 9 September 1899 Early Morning, Berhampur
Demise on 20 June 1972 at 9h09m at Visakhapatnam),
at his residence, Narasimha Ashram, Official Colony,
Maharanipeta. P. O., Visakhapatnam 530002.
[Mrs. Peramma Rangadhama Rao demise on 31 Dec 1971 around 10 AM.]
TRUWIZ-120b
Q61. arXiv:1905.09842 [astro-ph.GA]: Simulating cosmological substructure in the solar neighbourhood. Christine M. Simpson, Ignacio Gargiulo, Facundo A. Gómez, Robert J. J. Grand, Nicolás Maffione, Andrew P. Cooper, Alis J. Deason, Carlos Frenk, John Helly, Federico Marinacci, Rüdiger Pakmor. (Submitted on 23 May 2019): ABSTRACT: We explore the predictive power of cosmological, hydrodynamical simulations for stellar phase space substructure and velocity correlations with the Auriga simulations and Aurigaia mock-Gaia catalogues. We show that at the solar circle the Auriga simulations commonly host phase space structures in the stellar component that have constant orbital energies and arise from accreted subhaloes. These structures can persist for a few Gyrs, even after coherent streams in position space have been erased. We also explore velocity two-point correlation functions and find this diagnostic is not deterministic for particular clustering patterns in phase space. Finally, we explore these structure diagnostics with the Aurigaia catalogues and show that the current catalogues have the ability to recover some structures in phase space but careful consideration is required to separate physical structures from numerically seeded structures. CONCLUSIONS: Prominent substructures with high velocities points toward their importance in determining the Galactic mass from high-velocity stars. The gaia mission has expanded our understanding of the MW’s accretion history. Cosmological simulations will be an important tool for interpreting these data and this letter has provided the first proof of concept of this strategy. We have described notable caveats to working with mock data, but we anticipate further improvements to simulations and mock generation methods will result in a robust tool for theoretical interpretation of the mission’s data in this
a. area b. regime c. structures d. strategy.
Q62. arXiv:1905.10025 [astro-ph.HE]: A counter-top search for macroscopic dark matter. Jagjit Singh Sidhu, Glenn Starkman, Ralph Harvey. (Submitted on 24 May 2019): ABSTRACT: A number of dark matter candidates have been discussed that are macroscopic, of approximately nuclear density, and scatter ordinary matter essentially elastically with approximately their geometric cross-section. A wide range of mass and geometric cross-section is still unprobed for these "macros." Macros passing through rock would melt the material in cylinders surrounding their long nearly straight trajectories. Once cooled, the resolidified rock would be easily distinguishable from its surroundings. We discuss how, by visually examining ordinary slabs of rock such as are widely available commercially for kitchen countertops, one could probe an interesting segment of the open macro parameter space. CONCLUSIONS: we see that a manageable search for features that can easily be identified by eye, in a quantity of granite slabs such as are normally found at a typical commercial countertop showroom, will begin to probe unexplored regions of parameter space, but not down to nuclear density. Since we do not know the detailed microphysics of macros, it is valuable to probe all open parameter values. Moreover, this search would serve as an important proof-of-concept for scaling up to the largescale effort that would be required to push down to the nuclear-density
a. limit b. space c. parameter d. line
a. limit b. space c. parameter d. line
Q63. arXiv:1905.10127 [astro-ph.HE]: Penetrating component in cosmic rays. Sergey Shaulov. (Submitted on 24 May 2019): ABSTRACT: We present a study of the high energy spectra of hadrons in cores of extensive air showers. These data were obtained for the first time in the hybrid {\it HADRON} experiment (Tien-Shan) by means of a large X-ray emulsion chamber combined with the shower array. In the local energy interval 3--100 PeV an increase in the energy of hadrons was found, which means the appearance of a penetrating component. This component in our experiment was observed in the atmosphere that indicates the presence of a penetrating strongly interacting component in primary cosmic rays. Along with that, it is worth emphasising that the region where this component is observed coincides with the region of the so-called knee in the spectrum of cosmic rays. On this basis, a new hypothesis of knee formation can be put forward. CONCLUSIONS: There is only one such variant among the known strongly interacting particles — nuclei, among which protons are the most penetrating component. So we should assume the appearance of a new CR component which consist mainly of protons for the energies about ∼ 10 PeV and heavier nuclei in the energy range of 10–100 PeV. Such a model clearly requires astrophysical justification. The main doubt is related to the incomprehensible correlation between the intensity and energy of the galactic and new CR component. If the new component is of extragalactic origin, the correlation of these parameters looks extremely unconvincing. The model of a single close source is more preferable but also raises doubts mainly because of the need large proportion of protons in the nuclear composition of the radiation. It seems that the data presented here make look for more convincing ways to interpret the knee in the EAS
a. intensity b. energy c. spectrum d. data.
a. intensity b. energy c. spectrum d. data.
a. front b. background c. matter d. possibility
Q65.arXiv:1905.10717 [astro-ph.HE]: Black Hole Spin Signature in the Black Hole Shadow of M87 in the Flaring State. Tomohisa Kawashima, Motoki Kino, Kazunori Akiyama. (Submitted on 26 May 2019): ABSTRACT: Imaging the immediate vicinity of supermassive black holes (SMBH) and extracting a BH-spin signature is one of the grand challenges in astrophysics. M87 is known as one of the best targets for imaging the BH shadow and it can be partially thick against synchrotron self-absorption (SSA), particularly in a flaring state with high mass accretion rate. However, little is known about influences of the SSA-thick region on BH shadow images. Here we investigate BH shadow images of M87 at 230 GHz properly taking into account the SSA-thick region. When the BH has a high spin value, the corresponding BH shadow image shows the positional offset between the centre of the photon ring and that of the SSA-thick ring at the innermost stable circular orbit (ISCO) due to the frame-dragging effect in the Kerr spacetime. As a result, we find that a dark-crescent structure is generally produced between the photon ring and the SSA-thick ISCO ring in the BH shadow image. The scale size of the dark-crescent increase with BH spin: its width reaches up to ∼2 gravitational radius when the BH spin is 99.8% of its maximum value. The dark crescent is regarded as a new signature of a highly spinning BH. This feature is expected to appear in flaring states with relatively high mass accretion rate rather than the quiescent states. We have simulated the image reconstruction of our theoretical image by assuming the current and future Event Horizon Telescope (EHT) array, and have found that the future EHT including space-very long baseline interferometry in 2020s can detect the dark crescent. CONCLUSIONS: We emphasize the importance of 350 GHz VLBI observations in the future, because the width of the dark crescent is larger at 350 GHz due to the decrease of the optical depth for SSA, which results in the more robust detectability of the dark crescent in future EHT observation. Toward realizing the transcontinental VLBI at 350 GHz, the 12 m diameter radio telescope is now almost deployed to the Summit Station in Greenland. The telescope (Greenland Telescope, GLT) is to become one of the VLBI stations at 350 GHz, providing the longest baseline, longer than 9000 km to achieve an exceptional angular resolution of 20 µas, and we will be able to conduct observations at event horizon angular
a. crescent b. image c. resolution d. departure.
Q66. arXiv:1905.11149 [astro-ph.HE]: The self-control of Cosmic Rays. Pasquale Blasi (GSSI). (Submitted on 27 May 2019): ABSTRACT: Several independent pieces of information have recently hinted at a prominent role of cosmic rays in controlling their own transport, within and around the sources as well as throughout their propagation on Galactic scales and even possibly during their escape from the Galaxy. I will discuss this topic with special attention to the theoretical implications and possible additional observational evidence that we may seek with upcoming experiments. Introduction The bulk of cosmic rays (CRs) is made of fully ionized light nuclei, moving at speeds close to the speed of light. In all cases of astrophysical interest, these particles propagate diffusively through magnetized media, with the possible exception of CRs at the highest energies, which might propagate quasi-ballistically. The diffusive ansatz seems appropriate to both acceleration regions and transport through the Galaxy. Yet, many aspects of this ansatz are somewhat less clear than one would think. CONCLUSION: This chain of events causes CRs to be advected away from our Galaxy and to develop an over density in a region of the order of a few galactic disc radii, several tens of kpc. In this region the occasional interactions of accumulated CRs with the gas in the circum-galactic medium leads to the production of neutrinos (through the decay of charged pions) and gamma rays (through the decay of neutral pions). The neutrino flux compares well with the observations of IceCube, provided there is an over density of∼100−200 in the gas, compatible with what is expected inside the virial radius of a structure such as our Galaxy. Interestingly, a diffuse gamma ray emission has recently been measured by Fermi-LAT from a large region around the Andromeda
a. cluster of stars b. transport c. complex d. galaxy.
Q67. arXiv:1905.11429 [astro-ph.GA]: Discovery of nine new stellar groups in the Orion complex. Boquan Chen, Elena D'Onghia, João Alves, Angela Adamo. (Submitted on 27 May 2019):ABSTRACT: We use two unsupervised machine learning algorithms, Shared Nearest Neighbor (SNN) and \textit{EnLink}, as a single approach to identify stellar groupings in the Orion star-forming complex as an application to the 5-dimensional astrometric data from Gaia DR2. The algorithms present two different ways to limit user bias when evaluating the relative weights among the astrometric parameters, automatically determined by the machine and through a standard procedure by monitoring several outcome measures. Both algorithms complement each other and produce similar stellar groups. Because SNN groups have a much smaller spread in proper motions compared to \textit{EnLink}, we use \textit{EnLink}, which requires no input, as a first pass tool for group identification and validation. We then used the SNN algorithm to dissect the Orion star-forming complex. We identify 21 spatially- and kinematically-coherent groups in the Orion complex, nine of which previously unknown. The groups show a wide distribution of distances extending as far as about 150 pc in front of the star-forming Orion clouds, to about 50 pc beyond them where we find, unexpectedly, three groups. Our results expose to view the wealth of sub-structure in the OB association, within and beyond the classical Blaauw Orion OBI sub-groups. A full characterization of the new groups is of the essence as it offers the potential to unveil how star formation proceeds globally in large complexes such as Orion. The data and code that generated the groups is provided in this Letter. DETAILS: An obvious target to disentangle young populations leaving their natal gas is the Orion complex, the closest massive star forming region to Earth. CONCLUSIONS: The analysis in this work should be repeated including the sixth dimension, radial velocity. We expect radial velocity to be available for more stars in the Orion complex from Gaia DR3 or ongoing GALAH observations. The addition of radial velocity will allow us to produce stellar groups consistent in 6d phase space and study the kinematics of these groups. GaiaDR3 will provide more precise parallaxes and proper motions, which would further improve clustering results. For now, a full characterization of the new groups is of the essence as it offers the potential to unveil how star formation proceeds globally in large complexes such as
a. OB group b. Orion c. GALA d. GaiaDR3.
Q68. arXiv:1905.11727 [astro-ph.SR]: Spectroscopy of supergiants with infrared excess: results of 1998-2018. V.G. Klochkova. (Submitted on 28 May 2019):ABSTRACT: The results of our second stage (1998-2018) of the detailed spectroscopy of peculiar supergiants identified with galactic infrared sources, performed mainly at the 6-meter BTA telescope are summarized. The main aspect of the program is a search for the evolutionary variations in the chemical composition of stars, past the AGB stage and the TDU, as well as an analysis of spectral manifestations of kinematic processes in their extended, often unstable, atmospheres and in the envelopes. The most significant result is detection of the s-process element excesses in seven single post-AGB stars, which confirms the theory of evolution of this type of stars. In three of these stars we for the first time discovered the ejection of the s-process heavy metals to the circumstellar envelopes. A lithium excess was found in the atmospheres of two peculiar supergiants V2324 Cyg and V4334 Sgr. The results of investigation of the kinematical state of atmospheres and envelopes will clarify the equilibrium of matter produced by stars in the AGB and post-AGB stages and delivered to the interstellar medium. CONCLUSIONS: The results obtained during the PPN spectroscopy program allow us to distinguish the priority directions in the further study of objects at the stage of transition of a star to a planetary nebula and related objects. First of all, a further investigation of the ‘spectroscopic mimicry’ problem is required, which allows peculiar low-mass supergiants to disguise themselves as the most massive stars of high luminosity. Secondly, we believe that we should further focus on the spectral monitoring of selected variable and rapidly evolving objects. Thirdly, a detailed study of the structure of circumstellar envelopes is required, attracting the spectropolarimetry method too to clarify the mechanisms of the outflow and accretion of
a. matter b. nebula c. stars d. supergiants.
a. matter b. nebula c. stars d. supergiants.
Q69. arXiv:1905.11919 [gr-qc]: Hamiltonian Analysis In New General Relativity. Daniel Blixt, Manuel Hohmann, Martin Krššák, Christian Pfeifer.(Submitted on 28 May 2019):ABSTRACT: It is known that one can formulate an action in teleparallel gravity which is equivalent to general relativity, up to a boundary term. In this geometry we have vanishing curvature, and non-vanishing torsion. The action is constructed by three different contractions of torsion with specific coefficients. By allowing these coefficients to be arbitrary we get the theory which is called `new general relativity'. In this note, the Lagrangian for new general relativity is written down in ADM-variables. In order to write down the Hamiltonian we need to invert the velocities to canonical variables. However, the inversion depends on the specific combination of constraints satisfied by the theory (which depends on the coefficients in the Lagrangian). It is found that one can combine these constraints in 9 different ways to obtain non-trivial theories, each with a different inversion formula. Introduction: Gravity is conventionally described with the Levi-Civita connection which is induced by a pseudo-Riemannian metric. This means that the covariant derivative of the metric is zero, and the connection is torsion-free but has curvature. However, there are equivalent theories to general relativity. We will focus on teleparallel gravity where we have vanishing curvature, but non-vanishing torsion. CONCLUSIONS: One can distinguish 9 different classes of NGR theories by the presence or absence of primary constraints appearing in their Hamiltonian formulation. What remains to be determined is how many secondary constraints are induced by demanding closure of the constraint
a. arithmetic b. variables c. algebra d. supersymmetry.
a. arithmetic b. variables c. algebra d. supersymmetry.
Q70. arXiv:1905.12643 [astro-ph.HE]: Solar luminosity bounds on mirror matter. Erez Michaely, Itzhak Goldman, Shmuel Nussinov. (Submitted on 29 May 2019): ABSTRACT: We present bounds on mirror dark matter scenario derived by using the effect of mirror matter on the luminosity of the Sun. In the perturbative regime where the mirror matter concentration is small relative to the ordinary matter we estimate the heat transfer from ordinary matter to the mirror sector by simple analytic consideration. That amount of heat transfer is radiated via mirror photons and increases the required energy production in order to maintain the observed luminosity. We then present more detailed numerical calculations of the total amount of this energy transfer. INTRODUCTION: Finding the nature of Dark Matter (DM) which most likely contributes ∼ 25% of the energy density of the universe is an outstanding challenge Feng (2010). Some types of DM which arise beyond the standard model (BSM) of particle physics are being experimentally searched and or are constrained by astrophysics. In particular DM particles such as axions, dark photons and new types of neutrinos can be emitted from and lead to excessive cooling of neutron stars, white dwarfs red giants etc. CONCLUSIONS: The point is that in these models both σxx′ and η are fixed by the same single dimensionless kinetic mixing parameter epsilon of the photon and mirror photon. Specifically epsilon2 appears in the mirrorordinary matter Ruthdeford like scattering above. In order to evade the apparent difficulties associated with mirror matter forming a disc overlaping the ordinary Milky Way disc one needs a minimal σxx′ corresponding to a high epsilon value of ∼ 10^−9. The parameter epsilon also controls the expected fraction of mirror matter η ∼ epsilon2 which is mixed into the presolar cloud. This preferred optimal value yields the η ∼ 10^−5 and σxx′ ∼ 10^−36. The product ησxx′ ∼ 10^−41 will then exceed the maximum value we found from the 4% limit of the solar luminosity emitted via mirror photons to be ησxx′ ∼ 10^−51 , by a factor of 1010! Thus our new limits tends to most strongly exclude the above optimal ǫ value and the large class of almost exactly symmetric mirror models which depend on
Q81. arXiv:1906.02211 [gr-qc]: Primordial fluctuations from quantum gravity. Francesco Gozzini, Francesca Vidotto. (Submitted on 5 Jun 2019): ABSTRACT: We study fluctuations and correlations between spacial regions, generated by the primordial quantum gravitational phase of the universe. We do so by a numerical evaluation of Lorentzian amplitudes in Loop Quantum Gravity, in a non-semiclassical regime. We find that the expectation value of the quantum state of the geometry emerging from the early quantum phase of the universe is a homogeneous space but fluctuations are very large and correlations are strong, although not maximal. In particular, this suggests that early quantum gravitational effects could be sufficient to solve the cosmological horizon problem. INTRODUCTION: The universe emerged from its early quantum gravitational phase in a state that included fluctuations with correlations between distinct regions of space. These primordial fluctuations play a key role in cosmology — with or without inflation — in particular as seeds for structure formation. Here we explore the physical genesis of these fluctuations from the primordial quantum gravitational cosmological state. We use Loop Quantum Gravity (LQG) and a simple model of the early universe. CONCLUSIONS: Finally, we also computed the entanglement entropy of a single region viewed as a quantum subsystem of the whole universe. We found that our proposed cosmological state is highly non-typical, showing an entanglement entropy that is apparently reaching an asymptotic value as the scale factor increases. It would be interesting to link this peculiar behaviour to some geometrical properties of our model, and more ambitiously to some large-scale effect that could be tested by
a. it b. photons c. optimal value d. epsilon.
Q71.arXiv:1905.12836 [astro-ph.CO]: Bounding the mass of graviton in a dynamic regime with binary pulsars. Xueli Miao, Lijing Shao, Bo-Qiang Ma. (Submitted on 30 May 2019): ABSTRACT: In Einstein's general relativity, gravity is mediated by a massless spin-2 metric field, and its extension to include a mass for the graviton has profound implication for gravitation and cosmology. In 2002, Finn and Sutton used the gravitational-wave (GW) back-reaction in binary pulsars, and provided the first bound on the mass of graviton. Here we provide an improved analysis using 9 well-timed binary pulsars with a phenomenological treatment. First, individual mass bounds from each pulsar are obtained in the frequentist approach with the help of an ordering principle. The best upper limit on the graviton mass, m g <3.5×10^−20 eV/c^2 (90% C.L.), comes from the Hulse-Taylor pulsar PSR B1913+16. Then, we combine individual pulsars using the Bayesian theorem, and get mg<5.2×10^−21eV/c^2 (90% C.L.) with a uniform prior for ln mg. This limit improves the Finn-Sutton limit by a factor of more than 10. Though it is not as tight as those from GWs and the Solar System, it provides an independent and complementary bound from a dynamic regime. CONCLUSION: we would like to stress that, same as the well-recognized limit from Finn and Sutton, our limits are based on the phenomenological action. It is a phenomenological treatment of a linearized version of a massive rank-2 tensor field gµν; it should not be taken as a full and sophisticatedly designed theory. The behaviour of the tensor modes is the same as that in a healthy theory of massive gravity and the bound which comes from the Finn-Sutton method is in principle applicable to binary pulsar systems. This viewpoint also applies to the limits obtained from the propagation of GWs and the Yukawa potential. These generic limits do not necessarily mean that they are applicable to all theories of massive gravity. Nevertheless, they are still useful as simple empirical results on the mass of
a. pulsar b. tensor field c. GWs d. graviton.
a. pulsar b. tensor field c. GWs d. graviton.
Q72.arXiv:1905.13103 [astro-ph.HE]: On the nature of radio filaments near the Galactic Center. Maxim V. Barkov, Maxim Lyutikov. (Submitted on 30 May 2019): ABSTRACT: We suggest that narrow, long radio filaments near the Galactic Center arise as kinetic jets - streams of high energy particles escaping from ram-pressure confined pulsar wind nebulae (PWNe). The reconnection between the PWN and interstellar magnetic field allows pulsar wind particles to escape, creating long narrow features. They are the low frequency analogs of kinetic jets seen around some fast-moving pulsars, such as The Guitar and The Lighthouse PWNe. The radio filaments trace a population of pulsars also responsible for the Fermi GeV excess produced by the Inverse Compton scattering by the pulsar wind particles. The magnetic flux tubes are stretched radially by the large scale Galactic winds. In addition to PWNe accelerated particles can be injected at supernovae remnants. The model predicts variations of the structure of the largest filaments on scales of ∼dozens of years - smaller variations can occur on shorter time scales. We also encourage targeted observations of the brightest sections of the filaments and of the related unresolved point sources in search of the powering PWNe and pulsars. INTRODUCTION: In the present paper we advance a model of Galactic Centre’s NTFs as low frequency analogues of extended features seen around some ram pressure-confined PWN, such as the Guitar and the Lighthouse. Using 3D relativistic MHD simulations Barkov et al. showed that these features can’t have hydrodynamical origin and have to be kinetically streaming pulsar wind particles that escaped into the interstellar medium (ISM) due to reconnection between the PWN and ISM magnetic fields. CONCLUSIONS: Finally, some NTFs seem to connect to individual SNRs or to large scale bubbles formed by merged SNRs or Particle source in the galactic centre. SNRs are well known source of accelerated non-thermal leptons. Non-thermal particles that can escape along magnetic fields and can produce similar extended features. If SNR is an origin, one then expects a kinetic jet on both sides. One possibility is that kinetic jets end in SNRs: locally generated turbulence impedes propagation of particles, terminating the kinetic jet. The drop of magnetic field intensity on the scale SNR also can explain strong asymmetry of
a. SNR b. leptons c. NTFs d. particles.
a. SNR b. leptons c. NTFs d. particles.
Q73.arXiv:1905.12635 [hep-ph]: Direct Detection Signals from Absorption of Fermionic Dark Matter. Jeff A. Dror, Gilly Elor, Robert McGehee. (Submitted on 29 May 2019): ABSTRACT: We present a new class of direct detection signals; absorption of fermionic dark matter. We enumerate the operators through dimension six which lead to fermionic absorption, study their direct detection prospects, and summarize additional constraints on their suppression scale. Such dark matter is inherently unstable as there is no symmetry which prevents dark matter decays. Nevertheless, we show that fermionic dark matter absorption can be observed in direct detection and neutrino experiments while ensuring consistency with the observed dark matter abundance and required lifetime. For dark matter masses well below the GeV scale, dedicated searches for these signals at current and future experiments can probe orders of magnitude of unexplored parameter space. DISCUSSION: we have introduced a novel class of signals from fermionic DM absorption in direct detection and neutrino experiments. We have studied the sensitivities of future and current experiments to neutral current signals from the process χ + N → ν + N. This neutral current causes target isotopes to recoil with distinct energies and correlated rates, enabling significant background reduction in searches. We have also studied the sensitivities of current experiments to induced β− decays from the process χ+A ZX → e−+ A Z+1X + ∗ . This charged current enjoys distinct signatures from a sequence of events starting with a nuclear recoil and ejected e−, followed by a likely γ decay and often a final β decay or electron capture event several days later. For both signals, ongoing experiments can probe orders of magnitude of unexplored parameter space by performing dedicated
a. experiments b. searches c. signals d. events.
Q74. arXiv:1905.12779 [hep-ph]: Is the Y(2175) a Strangeonium Hybrid Meson? J. Ho, R. Berg, T. G. Steele, W. Chen, D. Harnett. (Submitted on 29 May 2019): ABSTRACT: QCD Gaussian sum-rules are used to explore the vector (JPC=1−−) Strangeonium hybrid interpretation of the Y(2175) . Using a two-resonance model consisting of the Y(2175) and an additional resonance, we find that the relative resonance strength of the Y(2175) in the Gaussian sum-rules is less than 5% that of a heavier 2.9 GeV state. This small relative strength presents a challenge to a dominantly-hybrid interpretation of the Y(2175). DISCUSSION: In summary, we have used QCDGSRs to study the Strangeonium hybrid interpretation of the Y(2175). Compared with LSRs, the advantage of the GSRs approach is its comparable sensitivity to multiple states in a hadronic spectral function. This allows us to explore the relative coupling to the hybrid current for the Y(2175) and an additional unknown resonance. We find excellent agreement between the QCD prediction and hadronic model, and determine an upper bound r ≤ 5% for the relative coupling strength of the Y(2175). Although this result seems to preclude a dominantly hybrid interpretation of the Y(2175), further studies such as the partial widths for a Y(2175) hybrid are necessary to determine whether the small relative coupling is in tension with the decay patterns of the
a. QCD b. LSRs c. current d. Y(175).
a. QCD b. LSRs c. current d. Y(175).
Q75. arXiv:1905.13115 [physics.geo-ph]: Evolution of the inner core of the earth: consequences for geodynamo. M. Yu. Reshetnyak. (Submitted on 22 May 2019): ABSTRACT: Using models of the Earth's core evolution and the length of the day observations the change of the dimensionless geodynamo parameters is considered. The evolutionary model includes cooling of the liquid adiabatic core, growing solid core, and the region in the outer part of the core with a subadiabatic temperature gradient. The model covers time period 4.5Ga in the past till 1.5Gy to the future, and produce evolution of the energy sources of the thermal and compositional convection, spatial scales of the convective zone. These quantities are used for Ekman, Rayleigh and Rossby numbers estimates. So far these numbers determine regime of the geomagnetic field generation, we discuss evolution of the geomagnetic field over Earth's evolution. CONCLUSIONS: The evolutionary models predict existence of the young inner core ∼ 1Ga. Switch on of the compositional convection, concerned with the inner core solidification, leads to increase of convection intensity in the core. In units of its critical value the Rayleigh number increases in factor 20 that corresponds to increase of the intensity of the geomagnetic field times (20)^1/3 ≈ 2.7. Moreover, influence of the inner core on the magnetic field generation can be even smaller. The reason is that compositional convection generates magnetic field located deeper in the liquid core, and as a result, intensity of the magnetic field at the surface of the planet is weaker than in the case of the thermal convection. In some sense our result confirms recent results that switch on of the compositional convection does not change generation of the magnetic field essentially, as it was supposed earlier. However the absolute values of the Rayleigh numbers are still under consideration, and their comparison for the compositional and thermal convection models is a tricky procedure, the time evolution of these parameters is not so questionable: the considered above scenarios predict increase of the geomagnetic reversals frequency with the inner core growth in agreement with observations. It is worth noting that our analysis includes two independent physical data: concerned with the thermal evolution of the core, and evolution of the length of the day, based on observations. Of course, these data are interrelated, and the more complicated physical model is required for description. The hint is that identification of the break in the curve of length of the day with the origin of the inner core simplifies the general evolution scenario for the considered model. In this case the young inner core is more
a. complicated b. likely c. simplified d. assertive.
a. complicated b. likely c. simplified d. assertive.
Q76.https://arxiv.org/abs/1905.11725: Role of Ligand Conformation on Nanoparticle Protein Interactions. Federica Simonelli, Giulia Rossi and Luca Monticelli. ABSTRACT : Engineered biomedical nanoparticles (NP) administered via intravenous routes are prone to associate to serum proteins. The protein corona can mask the NP surface functionalization and hamper the delivery of the NP to its biological target. The design of corona-free NPs relies on our understanding of the chemical-physical features of the NP surface driving the interaction with serum proteins. Here we address, by computational means, the interaction between human serum albumin (HSA) and a prototypical monolayer-protected Au nanoparticle. We show that both the chemical composition (charge, hydrophobicity) and the conformational preferences of the ligands decorating the NP surface affect the NP propensity to bind HSA. INTRODUCTION: Nanoparticles designed to be administered via intravenous routes are prone to interact with serum proteins, which can stably cluster around the nanoparticle forming a protein corona. The non-specific adsorption of proteins on NPs alters their designed function and influence their fate in the body. CONCLUSIONS: Our data show that ligand conformation is as relevant as chemical affinity in determining protein-NP interactions. As a result, we propose that the design of protein-repellent NP functionalization should consider carefully the importance of both ligand conformation and ligand chemical composition. Computational models, also at coarse-grained level, are paramount for the prediction of ligand conformations relevant to the NP-protein interface, and we envision that they will contribute more in the future to quantify the relative weight of structural and chemical factors influencing NP-protein
a. collisions b. complexities c. interactions d. conformations.
Q77. arXiv:1906.02203 [astro-ph.HE]: The dust content of the Crab Nebula. I. De Looze, M.J. Barlow, R. Bandiera, A. Bevan, M.F. Bietenholz, H. Chawner, H.L. Gomez, M. Matsuura, F. Priestley, R. Wesson. (Submitted on 5 Jun 2019):ABSTRACT: We have modelled the near-infrared to radio images of the Crab Nebula with a Bayesian SED model to simultaneously fit its synchrotron, interstellar and supernova dust emission. We infer an interstellar dust extinction map with an average AV =1.08 ±0.38 mag, consistent with a small contribution (<22%) to the Crab's overall infrared emission. The Crab's supernova dust mass is estimated to be between 0.032 and 0.049 M⊙ (for amorphous carbon grains) with an average dust temperature Tdust =41±3K, corresponding to a dust condensation efficiency of 8-12%. This revised dust mass is up to an order of magnitude lower than some previous estimates, which can be attributed to our different interstellar dust corrections, lower SPIRE flux densities, and higher dust temperature than were used in previous studies. The dust within the Crab is predominantly found in dense filaments south of the pulsar, with an average V-band dust extinction of AV=0.20-0.39 mag, consistent with recent optical dust extinction studies. The modelled synchrotron power-law spectrum is consistent with a radio spectral index αradio=0.297 ±0.009 and an infrared spectral index αIR=0.429±0.021. We have identified a millimetre excess emission in the Crab's central regions, and argue that it most likely results from two distinct populations of synchrotron emitting particles. We conclude that the Crab's efficient dust condensation (8-12%) provides further evidence for a scenario where supernovae can provide substantial contributions to the interstellar dust budgets in galaxies. INTRODUCTION: Early dust formation in the Universe has been suggested to result from an efficient condensation of dust species in the aftermaths of core-collapse supernovae (CCSNe), requiring each supernova remnant (SNR) to produce a net dust mass ranging between 0.1 and 1M. In this paper, we study the formation of dust in the Crab Nebula, a Galactic pulsar wind nebula (PWN) located at a distance of 2kpc1. The Crab Nebula is believed to be the remnant of a supernova of type II-P from a 8-11M progenitor star which exploded in 1054AD. CONCLUSIONS: The mm excess component is less prominent in the best-fit model with a peak flux density of 46Jy at 131GHz (compared to 69Jy at 163GHz for a broken power-law synchrotron model), which might suggest that an evolutionary synchrotron model is able to account for part of the mm excess emission observed in the
a. collisions b. complexities c. interactions d. conformations.
Q77. arXiv:1906.02203 [astro-ph.HE]: The dust content of the Crab Nebula. I. De Looze, M.J. Barlow, R. Bandiera, A. Bevan, M.F. Bietenholz, H. Chawner, H.L. Gomez, M. Matsuura, F. Priestley, R. Wesson. (Submitted on 5 Jun 2019):ABSTRACT: We have modelled the near-infrared to radio images of the Crab Nebula with a Bayesian SED model to simultaneously fit its synchrotron, interstellar and supernova dust emission. We infer an interstellar dust extinction map with an average AV =1.08 ±0.38 mag, consistent with a small contribution (<22%) to the Crab's overall infrared emission. The Crab's supernova dust mass is estimated to be between 0.032 and 0.049 M⊙ (for amorphous carbon grains) with an average dust temperature Tdust =41±3K, corresponding to a dust condensation efficiency of 8-12%. This revised dust mass is up to an order of magnitude lower than some previous estimates, which can be attributed to our different interstellar dust corrections, lower SPIRE flux densities, and higher dust temperature than were used in previous studies. The dust within the Crab is predominantly found in dense filaments south of the pulsar, with an average V-band dust extinction of AV=0.20-0.39 mag, consistent with recent optical dust extinction studies. The modelled synchrotron power-law spectrum is consistent with a radio spectral index αradio=0.297 ±0.009 and an infrared spectral index αIR=0.429±0.021. We have identified a millimetre excess emission in the Crab's central regions, and argue that it most likely results from two distinct populations of synchrotron emitting particles. We conclude that the Crab's efficient dust condensation (8-12%) provides further evidence for a scenario where supernovae can provide substantial contributions to the interstellar dust budgets in galaxies. INTRODUCTION: Early dust formation in the Universe has been suggested to result from an efficient condensation of dust species in the aftermaths of core-collapse supernovae (CCSNe), requiring each supernova remnant (SNR) to produce a net dust mass ranging between 0.1 and 1M. In this paper, we study the formation of dust in the Crab Nebula, a Galactic pulsar wind nebula (PWN) located at a distance of 2kpc1. The Crab Nebula is believed to be the remnant of a supernova of type II-P from a 8-11M progenitor star which exploded in 1054AD. CONCLUSIONS: The mm excess component is less prominent in the best-fit model with a peak flux density of 46Jy at 131GHz (compared to 69Jy at 163GHz for a broken power-law synchrotron model), which might suggest that an evolutionary synchrotron model is able to account for part of the mm excess emission observed in the
a. Crab Nebula b. 1054AD c. 163GHz d. Nebula.
Q78. arXiv:1906.02278 [astro-ph.HE]: On the Cosmological Evolution of Long Gamma-ray Burst Properties. Nicole M. Lloyd-Ronning, Aycin Aykutalp, Jarrett Johnson. (Submitted on 5 Jun 2019): ABSTRACT: We examine the relationship between a number of long gamma-ray burst (lGRB) properties (isotropic emitted energy, luminosity, intrinsic duration, jet opening angle) and redshift. We find that even when accounting for conservative detector flux limits, there appears to be a significant correlation between isotropic equivalent energy and redshift, suggesting cosmological evolution of the lGRB progenitor. Analyzing a sub-sample of lGRBs with jet opening angle estimates, we find the beaming-corrected lGRB emitted energy does not correlate with redshift, but jet opening angle does. Additionally, we find a statistically significant anti-correlation between the intrinsic prompt duration and redshift, even when accounting for potential selection effects. We also find that - for a given redshift - isotropic energy is positively correlated with intrinsic prompt duration. None of these GRB properties appear to be correlated with galactic offset. From our selection-effect-corrected redshift distribution, we estimate a co-moving rate density for lGRBs, and compare this to the global cosmic star formation rate (SFR). We find the lGRB rate mildly exceeds the global star formation rate between a redshift of 3 and 5, and declines rapidly at redshifts above this (although we cannot constrain the lGRB rate above a redshift of about 6 due to sample incompleteness). We find the lGRB rate diverges significantly from the SFR at lower redshifts. We discuss both the correlations and lGRB rate density in terms of various lGRB progenitor models and their apparent preference for low-metallicity environments. DATA: We take our data from Wang et al. (2019), who compiled all publicly available observations of 6289 gamma-ray bursts from 1991 to 2016. We searched this table for all GRBs that have a measured duration T90 > 2s, a redshift measurement and (therefore) an estimate of the isotropic emitted energy, Eiso. This leaves us with 376 data points - to our knowledge this is the most updated sample of measured redshifts analyzed to date (not including pseudo-redshifts, estimated through other correlations/techniques. CONCLUSIONS: We have speculated on many possible avenues to explain the results we find in this paper, in the context of various progenitor systems. We have not discussed many of the complicated details that play a role in the formation of lGRB progenitor stars, their deaths, and the subsequent formation of the GRB inner engine, the jet launch and its connection to observational variables. Nonetheless, the general trends we find must be accounted for, and may help guide us toward a better understanding of long gamma-ray burst progenitor systems in a cosmological
a. content b. progenitors c. context d. systems.
a. content b. progenitors c. context d. systems.
Q79. arXiv:1906.02508 [astro-ph.HE]: Cosmic Ray Acceleration in Hydromagnetic Flux Tubes. Anthony Bell, James Matthews, Katherine Blundell, Anabella Araudo. (Submitted on 6 Jun 2019): ABSTRACT: We find that hydromagnetic flux tubes in back-flows in the lobes of radio galaxies offer a suitable environment for the acceleration of cosmic rays (CR) to ultra-high energies. We show that CR can reach the Hillas (1984) energy even if the magnetised turbulence in the flux tube is not sufficiently strong for Bohm diffusion to apply. First-order Fermi acceleration by successive weak shocks in a hydromagnetic flux tube is shown to be equivalent to second-order Fermi acceleration by strong turbulence. INTRODUCTION: The origin of ultra-high energy cosmic rays (UHECR) is uncertain, and many possible sources have been proposed. Radio galaxies have long been considered a likely source of UHECR because of their high power, large size and longevity. CONCLUSIONS: The flow within lobes of radio galaxies is more complicated (see references in section 1) than allowed by our simplified model of one-dimensional flow in a steady uniform straight flux tube, and additional acceleration processes may be active. For example, the strong velocity differential across the edges of flux tubes may be a prime location for shear acceleration and for the growth of strong multi-dimensional turbulence due to the Kelvin-Helmholtz instability. Also, variations in the width of flux tubes along their length may give rise to lateral compressions and rarefactions that respectively accelerate and decelerate CR, although resulting changes in CR energy may be approximately adiabatic with limited overall effect. As shown by Achterberg, second-order Fermi acceleration is an umbrella term for a number of different effects that can be combined in a general quasi-linear theory of wave-particle interactions. The more general theory may provide a fruitful basis for an extended analysis in the complicated environment of a flux tube, and it may be possible to encompass first- and second-order Fermi acceleration and shear acceleration in a single comprehensive
a. thought b. analysis c. interactions d. flux-tube.
a. thought b. analysis c. interactions d. flux-tube.
Q80. arXiv:1906.02610 [astro-ph.HE]:The early life of millisecond magnetars. D I Jones. (Submitted on 5 Jun 2019):ABSTRACT: Some neutron stars may be born spinning fast and with strong magnetic fields---the so-called millisecond magnetars. It is important to understand how a star's magnetic axis moves with respect to the spin axis in the star's early life, as this effects both electromagnetic and gravitational wave emission. Previous studies have highlighted the importance of viscous dissipation within the star in this process. We advance this program by additionally considering the effect of the electromagnetic torque. We find an interesting interplay between the viscous dissipation, which makes the magnetic axis orthogonalise with respect to the spin, verses magnetic torques that tend to make the magnetic axis align with the spin axis. We present some results, and highlight areas where our model needs to be made more realistic. CONCLUSIONS: Opacity to neutrinos. When the star is sufficiently hot, it will be opaque to neutrinos. This could be accounted for in future work using the prescription of Lasky and Glampedakis, who switched bulk viscosity off above a critical temperature. Evolution of the temperature. Our prescription for evolving the temperature was particularly simple. In reality, additional cooling effects may be important in the early life of
a. neutrinos b. hot star c. evolution d. magnetars.
a. neutrinos b. hot star c. evolution d. magnetars.
a. analysis b. observations c. subsystem d. whole universe.
Q82. arXiv:1906.02712 [astro-ph.GA]: Dust properties and star formation of about a thousand local galaxies. Sophia Lianou, Pauline Barmby, Aleksandr Mosenkov, Matthew Lehnert, Oskar Karczewski. (Submitted on 6 Jun 2019): ABSTRACT: We derive the dust properties for 753 local galaxies and examine how these relate to some of their physical properties. We model their global dust-SEDs, treated statistically as an ensemble within a hierarchical Bayesian dust-SED modeling approach. The model-derived properties are the dust masses (Mdust), the average interstellar radiation field intensities (Uav), the mass fraction of very small dust grains ('QPAH' fraction), as well as their standard deviations. In addition, we use mid-IR observations to derive SFR and Mstar, quantities independent of the modeling. We derive distribution functions of the properties for the galaxy ensemble and per galaxy type. The mean value of Mdust for the ETGs is lower than that for the LTGs and IRs, despite ETGs and LTGs having Mstar spanning across the whole range observed. The Uav and 'QPAH' fraction show no difference among different galaxy types. When fixing Uav to the Galactic value, the derived 'QPAH' fraction varies across the Galactic value (0.071). The sSFR increases with galaxy type, while this is not the case for the dust-sSFR (=SFR/Mdust), showing an almost constant SFE per galaxy type. The galaxy sample is characterised by a tight relation between Mdust and Mstar for the LTGs and Irs, while ETGs scatter around this relation and tend towards smaller Mdust. While the relation indicates that Mdust may fundamentally be linked to Mstar, metallicity and Uav are the second parameter driving the scatter, which we investigate in a forthcoming work. We use the extended KS law to estimate Mgas and the GDR. The Mgas derived from the extended KS law is on average ~20% higher than that derived from the KS law, and a large standard deviation indicates the importance of the average SF present to regulate star formation and gas supply. The average GDR for the LTGs and IRs is 370, while including the ETGs gives an average of 550. INTRODUCTION: For the 753 galaxies considered here, the median number of bands used in the SED modelling is twelve. The minimum number of bands used is four (in only one galaxy, NGC4636) and the maximum number of bands used is seventeen, i.e. the maximum possible (for four galaxies: NGC3256, NGC3982, NGC6946, UGC12160), while another three galaxies have only six bands (PGC029653; NGC2974; ESO411013). There are 740 galaxies with WISE22µm observations, and 99 galaxies with Spitzer IRAC8µm observations. We have included the Spitzer IRAC8µm due to the unique constraint to the mid-IR part of the dust-SED it provides. Dust grains are characterised by their chemical composition, size distribution, shape, and abundances (Savage & Mathis 1979; Zubko et al. 2004; Draine 2009). The main principle of the THEMIS model is that dust evolves in response to the physical conditions of its local environment and is not characterised by the same properties everywhere; therefore, dust has different chemical composition, structure, shape, according to the physical conditions exposed, which in turn affects its optical properties (Jones et al. 2017). The THEMIS model is built, as much as possible, upon laboratory measurements of dust material analogues to the interstellar dust, and modifications necessary to provide better fits to the observed interstellar dust properties have been made (Jones et al. 2013). The dust grain composition in the THEMIS model is a mixture of amorphous silicates, with iron and iron-sulphide nano-inclusions, and hydrogenated amorphous carbon materials (a-C(:H)). A mass element of the ISM is assumed to be illuminated by a non-uniform interstellar radiation field. The latter is described by a heating intensity U, with U=1 corresponding to the intensity of the solar neighbourhood, U=2.2×10^−5 Wm^−2. Then, the distribution of the dust masses per unit heating intensity is described by the power law over heating intensities: dMdust/dU∝U^−α, with Umin < U < Umin + ∆U. Integrating the above expression between Umin to Umin + ∆U results in the total dust mass, Mdust,for the assumed mass element. CONCLUSIONS: We emphasise that the strength of our results rely both on one of the largest galaxy samples in the local Universe with imaging treated homogeneously and on the statistical constraints posed on the properties of the galaxy sample modelled as an ensemble with a hierarchical Bayesian dust-SED model. These two elements make this study unique. As a follow up to what is presented here, we perform small physical scale analyses of as many galaxies as permitted (spatialconstraints), so as to be able to understand the local variations of the dust properties versus the star formation
a. story b. incidence c. model d. history.
Q83. arXiv:1906.02221 [astro-ph.HE]: Probing high-energy interactions of atmospheric and astrophysical neutrinos. Spencer R. Klein. (Submitted on 5 Jun 2019):ABSTRACT: Astrophysical and atmospheric neutrinos are important probes of the powerful accelerators that produce cosmic-rays with EeV energies. Understanding these accelerators is a key goal of neutrino observatories, along with searches for neutrinos from supernovae, from dark matter annihilation, and other astrophysics topics. Here, we discuss how neutrino observatories like IceCube and future facilities like KM3NeT and IceCube-Gen2 can study the properties of high-energy (above 1 TeV) neutrino interactions. This is far higher than is accessible at man-made accelerators, where the highest energy neutrino beam reached only 500 GeV. In contrast, neutrino observatories have observed events with energies above 5 PeV - 10,000 times higher in energy - and future large observatories may probe neutrinos with energies up to 10^20 eV. These data have implications for both Standard Model measurements, such as of low Bjorken −x parton distributions and gluon shadowing, and also for searches for beyond Standard Model physics. This chapter will review the existing techniques and results, and discuss future prospects. INTRODUCTION: The observed neutrino flux in neutrino telescopes includes contributions from conventional atmospheric neutrinos, prompt atmospheric neutrinos and an astrophysical flux. Conventional atmospheric neutrinos come from the decay of π±, K± and K0 produced in cosmic-ray air showers, while prompt atmospheric neutrinos arise from the decays of similarly produced charmed hadrons. CONCLUSIONS: Neutrino telescopes offer an opportunity to study neutrino physics at energies up to a few PeV, many orders of magnitude higher than are available at accelerators. Studies have been made of both the neutrino cross-sections, and also the final states produced, specifically the neutrino inelasticity distribution. These measurements are sensitive to many aspects of standard-model neutrino physics, and are also sensitive to some beyond standard-model physics. Future measurements with radio-Cherenov detectors should reach energies above 10^17 eV, enough to probe new physics at energies beyond those accessible at the LHC. Although the energy reach is impressive, the limited neutrino flux and large detector granularity limit the precision of current measurements. However, they are our only probe of neutrino energies above 1 TeV, and provide a useful new window for neutrino physics reaching up to and beyond LHC energies.
a. limits b. energies c. flux d. detectors.
Q84.arXiv:1906.05878 [astro-ph.HE]: Fast Radio Bursts: An Extragalactic Enigma. James M. Cordes, Shami Chatterjee. (Submitted on 13 Jun 2019): ABSTRACT: We summarize our understanding of millisecond radio bursts from an extragalactic population of sources. FRBs occur at an extraordinary rate, thousands per day over the entire sky with radiation energy densities at the source about ten billion times larger than those from Galactic pulsars. We survey FRB phenomenology, source models and host galaxies, coherent radiation models, and the role of plasma propagation effects in burst detection. The FRB field is guaranteed to be exciting: new telescopes will expand the sample from the current ∼80 unique burst sources (and a few secure localizations and redshifts) to thousands, with burst localizations that enable host-galaxy redshifts emerging directly from interferometric surveys. * FRBs are now established as an extragalactic phenomenon. * Only a few sources are known to repeat. Despite the failure to redetect other FRBs, they are not inconsistent with all being repeaters. * FRB sources may be new, exotic kinds of objects or known types in extreme circumstances. Many inventive models exist, ranging from alien spacecraft to cosmic strings but those concerning compact objects and supermassive black holes have gained the most attention. A rapidly rotating magnetar is a promising explanation for FRB 121102 along with the persistent source associated with it, but alternative source models are not ruled out for it or other FRBs. * FRBs are powerful tracers of circumsource environments, `missing baryons' in the IGM, and dark matter. * The relative contributions of host galaxies and the IGM to propagation effects have yet to be disentangled, so dispersion measure distances have large uncertainties. INTRODUCTION: Fast radio bursts (FRBs) are millisecond-duration pulses that originate from as-yet unidentified extragalactic sources. They are similar in some respects to pulses from Galactic radio pulsars, but the flux density is of order ten billion times larger and their spectra are radically different from most pulsar spectra and most other radio sources. CONCLUSIONS: The detection of rare weak bursts in massive volumes of survey data is a difficult problem, made more challenging by the steadily worsening radio frequency interference (RFI) environment. Machine learning techniques have been proposed and have already demonstrated dramatic results, and crossdisciplinary collaboration will continue to bear fruit. Manifestation of the cosmologically nearby FRB population is probably limited by the low burst rate per source, but sufficient dwell times on galaxy clusters may provide detections of nearby galaxies that are easier to characterize than more distant ones. If our Galaxy (or a neighboring one) hosts an FRB source, we might experience rare but extraordinarily bright bursts with (relatively) low pulse DM. Such bursts would be difficult to distinguish from RFI, but may be detectable with all-sky dipole antennas or as a citizen science project using mobile phone
a. setups b. systems c. devices d. receivers.
Q85.arXiv:1906.05892 [astro-ph.EP]: Was the Sun a Slow Rotator? -- Sodium and Potassium Constraints from the Lunar Regolith. Prabal Saxena, Rosemary M. Killen, Vladimir Airapetian, Noah E. Petro, Natalie M. Curran, Avi M. Mandell. (Submitted on 13 Jun 2019):ABSTRACT: While the Earth and Moon are generally similar in composition, a notable difference between the two is the apparent depletion in moderately volatile elements in lunar samples. This is often attributed to the formation process of the Moon and demonstrates the importance of these elements as evolutionary tracers. Here we show that paleo space weather may have driven the loss of a significant portion of moderate volatiles, such as sodium and potassium from the surface of the Moon. The remaining sodium and potassium in the regolith is dependent on the primordial rotation state of the Sun. Notably, given the joint constraints shown in the observed degree of depletion of sodium and potassium in lunar samples and the evolution of activity of solar analogues over time, the Sun is highly likely to have been a slow rotator. Since the young Sun's activity was important in affecting the evolution of planetary surfaces, atmospheres, and habitability in the early Solar System, this is an important constraint on the solar activity environment at that time. Finally, since solar activity was strongest in the first billion years of the Solar System, when the Moon was most heavily bombarded by impactors, evolution of the Sun's activity may also be recorded in lunar crust and would be an important well-preserved and relatively accessible record of past Solar System processes. INTRODUCTION The evolution of the Sun’s magnetic activity throughout the history of the Solar System is a key factor in understanding the past and current state of surfaces and atmospheres of planets in the inner Solar System. Solar activity could have played an important role in the habitability of a number of planets, including Earth, and may also have affected the evolution of planetary atmospheres and surfaces by influencing atmospheric loss and chemistry. Indeed, evidence from meteorites suggests a period of higher solar activity early in the Solar Systems’ history. Data from the Kepler space telescope on the activity of solar analogues has provided important evidence on different pathways the Sun may have followed with respect to stellar activity. CONCLUSIONS: Additionally, while most sputtered moderate volatiles would escape during CME passage, some proportion would return to the surface and would preferentially stick to colder surfaces towards the poles and ’permanently shadowed regions’ (PSRs). Given the increased loss early on, PSRs that existed prior to and after potential reorientation episodes of the Moon may exhibit higher abundances of these moderate volatiles (and may track reorientation episodes by capturing volatility influenced abundance gradients). In these cases, PSRs that remained largely shadowed over time may contain a vertical profile of deposited material (though again subject to mixing by regolith churn) that reflects volatile transport at least partially influenced by space weather activity. This may also be true of ancient lava tubes which similarly would protect volatiles once they become trapped. For PSRs that eventually became exposed to sunlight due to obliquity variations or reorientation, the total abundance and preferential loss of specific elements based upon their volatility may provide not only a proxy of the nature of reorientation events but also of deposition prior to and between these
a. events b. activities c. episodes d. reorientations.
Q86. arXiv:1906.05935 [astro-ph.HE]: Study of PeV neutrinos around dwarf galaxies near giant lobes of Centaurus A. E. Aguilar-Ruiz, N. Fraija, A. Galván-Gámez, J. A. De Diego, A. Marinelli. (Submitted on 13 Jun 2019) :ABSTRACT: The origin of recently discovered PeV neutrinos is an unsolved problem. In this work we consider a hadronic scenario to produce PeV neutrinos from a region around giant lobes of Centaurus A. Although ultrahigh-energy cosmic rays (UHECRs) are accelerated and confined by giant lobes, they can escape to be later injected in the inter-group medium where galaxies near the giant lobes provides the condition to confine them. UHECRs interact with low-energy photons and protons producing high-energy photons and neutrinos. We found that the IC35 event cannot be generated neither inside the giant lobes nor galaxies close to the lobes of Centaurus A. INTRODUCTION: Neutrinos are considered perfect astronomical messenger due to their very low capacity to interact with matter and radiation. They are able to escape from environment in which they are created and because of the lack of electric charge, they can travel large distances without being deflected by magnetic fields. Therefore, high-energy neutrinos could give us an indirect signal of the cosmic ray origins which have been a mystery up to now. CONCLUSIONS: In this work we have analysed the possible emission of the event IC35 from regions around of CenA. In this scenario, giant lobes of CenA provides a powerful place to accelerate UHECRs at energies as high as EeV. In the scenario where accelerated carbon nuclei escape from giant lobes and later are confined by galaxies, especially ESO324-G024 and NGC4945, we find that although nuclei-proton efficiencies are high in these places cannot produce a PeV neutrino event in IceCube detector. Therefore, we do not find enough evidence to correlate IC35 with UHECRs detected by
a. UHECRs b. IC35 c. PAO d. GO24.
Q87. arXiv:1906.06055 [astro-ph.SR]: High-resolution optical spectroscopy of Nova V392 Per. K. A. Stoyanov, T. Tomov, I. Stateva, S. Georgiev. (Submitted on 14 Jun 2019) : ABSTRACT:Here we analyze high-resolution spectra of the Nova V392 Per obtained during the 2018 outburst. The Hα and Hβ emission lines show a triple-peak structure with radial velocities of about -2000 km/s, -250 km/s and 1900 km/s respectively. The near infrared spectrum is dominated by the narrow and single-peaked Paschen lines of hydrogen and the OI λ8446 and OI λ7773 emission lines. Using DIBs and the KI line, we estimate the interstellar excess towards V392 Per. Based on AAVSO and ASAS-SN photometry data, we calculate that the t2 and t3 decline times are ∼3 d and ∼11 d respectively, which classifies V392 Per as a very fast nova. We also briefly discuss the similarity between V392 Per and other very fast novae and the possible future evolution of the system in terms of the hibernation model. INTRODUCTION: n the cataclysmic variables, the nova outburst is powered by thermonuclear runaway on the surface of the white dwarf (Bode & Evans 2008). Over long periods of time, the hydrogen-rich material is being accreted from the donor star and forms an envelope on the white dwarf. Once the critical temperature (a.k.a. Fermi temperature ∼ 7 × 107 K) and the critical pressure of the accreted material are reached, the thermonuclear runaway is ignited, causing a dramatic brightening with maximum magnitude in the range of -5 to -10.7. :CONCLUSIONS: As for the future evolution of V392 Per, there are two possible scenarios. According to the hibernation model, the system can appear as a nova-like variable star with a high accretion rate but no outbursts. As the accretion rate decreases, the system should transform into a dwarf nova. A similar evolution model is proposed for the dwarf nova BK Lyn that transformed from nova through a nova-like and finally into a dwarf nova. Another possibility is displaying recurrent nova outbursts with a recurrence time <100 yr, before entering hibernation. In any case, optical and spectral follow-up observations of V392 Per in the next decades will be much valuable for testing the cataclysmic variables and nova
a. evolution b. dwarfs c. outburst d. mixing.
Q89. arXiv:1906.06346 [astro-ph.HE]: Suppressed effective viscosity in the bulk intergalactic plasma. I. Zhuravleva, E. Churazov, A. A. Schekochihin, S. W. Allen, A. Vikhlinin, N. Werner. (Submitted on 14 Jun 2019): ABSTRACT: Transport properties, such as viscosity and thermal conduction, of the hot intergalactic plasma in clusters of galaxies, are largely unknown. While for laboratory plasmas these characteristics are derived from the gas density and temperature, such recipes can be fundamentally different for the intergalactic plasma due to a low rate of particle collisions and a weak magnetic field. In numerical simulations, one often cuts through these unknowns by modeling these plasmas as hydrodynamic fluids, even though local, non-hydrodynamic features observed in clusters contradict this assumption. Using deep Chandra observations of the Coma Cluster, we probe gas fluctuations in intergalactic medium down to spatial scales where the transport processes should prominently manifest themselves - at least if hydrodynamic models with pure Coulomb collision rates were indeed adequate. We find that they do not, implying that the effective isotropic viscosity is orders of magnitude smaller than naively expected. This indicates an enhanced collision rate in the plasma due to particle scattering off microfluctuations caused by plasma instabilities, or that the transport processes are anisotropic with respect to local magnetic field. For that reason, numerical models with high Reynolds number appear more consistent with observations. Our results also demonstrate that observations of turbulence in clusters are becoming a branch of astrophysics that can sharpen theoretical views on such plasmas. INTRODUCTION: Radio observations of Coma reveal extended non-thermal emission, suggesting the presence of a magnetic field with the strength ~ several µG20, which gives the ratio of thermal to magnetic pressure ~ 100. At the same time, the plasma is weakly collisional, i.e., the time between particles’ collisions via Coulomb interaction is longer than their gyration period in the magnetic fields. If such a plasma were described by a basic model of hydrodynamic fluid with a standard set of transport coefficients determined by Coulomb collisions, its turbulent motions would be strongly suppressed on spatial scales comparable to the Coulomb mean free path, λ, of electrons and protons. CONCLUSIONS: In contrast to the expectations for a Coulomb-collision-dominated plasma, the effective Reynolds number appears to be large. From the perspective of plasma physics, this finding is consistent with the presence of plasma instabilities that, by interacting with particles, effectively increase the collision rate of plasma, and/or with the establishment of a new type of turbulence in which motions adjust to be immune to the locally anisotropic plasma viscosity. From the perspective of hydrodynamic models of galaxy clusters, our finding favours the use of high-resolution simulations with the lowest possible numerical viscosity, as opposed to physical viscosity at the Spitzer a. events b. activities c. episodes d. reorientations.
Q86. arXiv:1906.05935 [astro-ph.HE]: Study of PeV neutrinos around dwarf galaxies near giant lobes of Centaurus A. E. Aguilar-Ruiz, N. Fraija, A. Galván-Gámez, J. A. De Diego, A. Marinelli. (Submitted on 13 Jun 2019) :ABSTRACT: The origin of recently discovered PeV neutrinos is an unsolved problem. In this work we consider a hadronic scenario to produce PeV neutrinos from a region around giant lobes of Centaurus A. Although ultrahigh-energy cosmic rays (UHECRs) are accelerated and confined by giant lobes, they can escape to be later injected in the inter-group medium where galaxies near the giant lobes provides the condition to confine them. UHECRs interact with low-energy photons and protons producing high-energy photons and neutrinos. We found that the IC35 event cannot be generated neither inside the giant lobes nor galaxies close to the lobes of Centaurus A. INTRODUCTION: Neutrinos are considered perfect astronomical messenger due to their very low capacity to interact with matter and radiation. They are able to escape from environment in which they are created and because of the lack of electric charge, they can travel large distances without being deflected by magnetic fields. Therefore, high-energy neutrinos could give us an indirect signal of the cosmic ray origins which have been a mystery up to now. CONCLUSIONS: In this work we have analysed the possible emission of the event IC35 from regions around of CenA. In this scenario, giant lobes of CenA provides a powerful place to accelerate UHECRs at energies as high as EeV. In the scenario where accelerated carbon nuclei escape from giant lobes and later are confined by galaxies, especially ESO324-G024 and NGC4945, we find that although nuclei-proton efficiencies are high in these places cannot produce a PeV neutrino event in IceCube detector. Therefore, we do not find enough evidence to correlate IC35 with UHECRs detected by
a. UHECRs b. IC35 c. PAO d. GO24.
Q87. arXiv:1906.06055 [astro-ph.SR]: High-resolution optical spectroscopy of Nova V392 Per. K. A. Stoyanov, T. Tomov, I. Stateva, S. Georgiev. (Submitted on 14 Jun 2019) : ABSTRACT:Here we analyze high-resolution spectra of the Nova V392 Per obtained during the 2018 outburst. The Hα and Hβ emission lines show a triple-peak structure with radial velocities of about -2000 km/s, -250 km/s and 1900 km/s respectively. The near infrared spectrum is dominated by the narrow and single-peaked Paschen lines of hydrogen and the OI λ8446 and OI λ7773 emission lines. Using DIBs and the KI line, we estimate the interstellar excess towards V392 Per. Based on AAVSO and ASAS-SN photometry data, we calculate that the t2 and t3 decline times are ∼3 d and ∼11 d respectively, which classifies V392 Per as a very fast nova. We also briefly discuss the similarity between V392 Per and other very fast novae and the possible future evolution of the system in terms of the hibernation model. INTRODUCTION: n the cataclysmic variables, the nova outburst is powered by thermonuclear runaway on the surface of the white dwarf (Bode & Evans 2008). Over long periods of time, the hydrogen-rich material is being accreted from the donor star and forms an envelope on the white dwarf. Once the critical temperature (a.k.a. Fermi temperature ∼ 7 × 107 K) and the critical pressure of the accreted material are reached, the thermonuclear runaway is ignited, causing a dramatic brightening with maximum magnitude in the range of -5 to -10.7. :CONCLUSIONS: As for the future evolution of V392 Per, there are two possible scenarios. According to the hibernation model, the system can appear as a nova-like variable star with a high accretion rate but no outbursts. As the accretion rate decreases, the system should transform into a dwarf nova. A similar evolution model is proposed for the dwarf nova BK Lyn that transformed from nova through a nova-like and finally into a dwarf nova. Another possibility is displaying recurrent nova outbursts with a recurrence time <100 yr, before entering hibernation. In any case, optical and spectral follow-up observations of V392 Per in the next decades will be much valuable for testing the cataclysmic variables and nova
a. evolution b. dwarfs c. outburst d. mixing.
a. constant b. value c. free path d. collision rate.
Q89. arXiv:1906.06452 [astro-ph.SR]: Magnetic Flux Cancellation as the Trigger Mechanism of Solar Coronal Jets. Riley A. McGlasson, Navdeep K. Panesar, Alphonse C. Sterling, Ronald Moore. (Submitted on 15 Jun 2019) : ABSTRACT: Coronal jets are transient narrow features in the solar corona that originate from all regions of the solar disk: active regions, quiet sun, and coronal holes. Recent studies indicate that at least some coronal jets in quiet regions and coronal holes are driven by the eruption of a minifilament following flux cancellation at a magnetic neutral line. We have tested the veracity of that view by examining 60 random jets in quiet regions and coronal holes using multithermal (304 A, 171 A, 193 A, and 211 A) extreme ultraviolet (EUV) images from the Solar Dynamics Observatory (SDO)/Atmospheric Imaging Assembly (AIA) and line-of-sight magnetograms from the SDO/Helioseismic and Magnetic Imager (HMI). By examining the structure and changes in the magnetic field before, during, and after jet onset, we found that 85% of these jets resulted from a minifilament eruption triggered by flux cancellation at the neutral line. The 60 jets have a mean base diameter of 8800 +/- 3100 km and a mean duration of 9 +/-3.6 minutes. These observations confirm that minifilament eruption is the driver and magnetic flux cancellation is the primary trigger mechanism for most coronal hole and quiet region coronal jets. INTRODUCTION: Solar coronal jets are narrow, short-lived coronal features that occur frequently throughout the entire solar magnetic cycle. Jets in polar coronal holes occur at an average rate of 60 jets per day. DATA: This study uses multithermal (171 ˚A, 193 ˚A, 211 ˚ A, and 304 ˚A) EUV images from the Solar Dynamics Observatory (SDO)/Atmospheric Imaging Assembly (AIA) to study the eruption of the minifilament and jet spire. SDO/AIA takes high-resolution (000.6 pixel−1) and high temporal cadence (12s) full-Sun images in seven EUV wavelengths. CONCLUSION: we report observations of 60 random on-disk coronal jets in quiet regions and coronal holes. From our observations, we find that at least for the great majority of these jets, minifilament eruption is the driver and magnetic flux cancellation is the trigger mechanism for coronal hole and quiet region coronal
a. shapes b. ejections c. jets d. cycles.
a. shapes b. ejections c. jets d. cycles.
Q90.arXiv:1906.06953 [astro-ph.EP]: Dust Spreading in Debris Discs: Do Small Grains Cling on to Their Birth Environment? Nicole Pawellek, Attila Moór, Ilaria Pascucci, Alexander V. Krivov. (Submitted on 17 Jun 2019):ABSTRACT: Debris discs are dusty belts of planetesimals around main-sequence stars, similar to the asteroid and Kuiper belts in our solar system. The planetesimals cannot be observed directly, yet they produce detectable dust in mutual collisions. Observing the dust, we can try to infer properties of invisible planetesimals. Here we address the question of what is the best way to measure the location of outer planetesimal belts that encompass extrasolar planetary systems. A standard method is using resolved images at mm-wavelengths, which reveal dust grains with sizes comparable to the observational wavelength. Smaller grains seen in the infrared (IR) are subject to several non-gravitational forces that drag them away from their birth rings, and so may not closely trace the parent bodies. In this study, we examine whether imaging of debris discs at shorter wavelengths might enable determining the spatial location of the exo-Kuiper belts with sufficient accuracy. We find that around M-type stars the dust best visible in the mid-IR is efficiently displaced inward from their birth location by stellar winds, causing the discs to look more compact in mid-IR images than they actually are. However, around earlier-type stars where the majority of debris discs is found, discs are still the brightest at the birth ring location in the mid-IR regime. Thus, sensitive IR facilities with good angular resolution, such as MIRI on JWST, will enable tracing exo-Kuiper belts in nearby debris disc systems. INTRODUCTION: Debris discs are dusty belts of comets and asteroids around stars, left over in planetary systems as a by-product of planet formation. These small bodies, or planetesimals, remain invisible to our telescopes. However, they produce detectable dust grains in mutual collisions and other destructive processes. Thus the properties of these planetesimals can only be inferred from observations of their dust. Observations at different wavelengths trace dust particles of different sizes, with large grains being best probed by observations at long wavelengths. The main reason is that the emission efficiency of dust particles drops at wavelengths longer than their sizes. Particles with sizes above centimetres remain invisible at any wavelength, simply because the cross section they carry is too small for any reasonable slope of the dust grain size distribution. CONCLUSIONS: In this paper, we analysed the possibility of locating parent planetesimal belts of debris discs by observing their dust emission at different
a. distributions b. wavelengths c. wavelets d. particles.
Q91. arXiv:1906.06992 [astro-ph.HE]: Diagnostics of timing noise in middle aged pulsars. Nakornping Namkham (Chaing Mai University, Thailand), Phrudth Jaroenjittichai (NARIT, Thailand), Simon Johnston (CSIRO, Australia): (Submitted on 12 Jun 2019): ABSTRACT: Radio pulsars are often used as clocks in a wide variety of experiments. Imperfections in the clock, known as timing noise, have the potential to reduce the significance of, or even thwart e.g. the attempt to find a stochastic gravitational wave (GW) background. We measure the timing noise in a group of 129 mostly middle-aged pulsars (i.e. characteristic ages near 1~Myr) observed with the Parkes radio telescope on a monthly basis since 2014. We examine four different metrics for timing noise, but it remains unclear which, if any, provides the best determination. In spite of this, it is evident that these pulsars have significantly less timing noise than their younger counterparts, but significantly more than the (much older) millisecond pulsars (MSPs). As with previous authors, we find a strong correlation between timing noise and the pulsar spin-down rate, ν. However, for a given ν there is a spread of about a factor 30 in the strength of the timing noise likely indicating that nuclear conditions in the interior of the stars differs between objects. We briefly comment on the implications for GW detection through pulsar timing arrays as the level of timing noise in MSPs may be less than predicted. INTRODUCTION The rotation of a pulsar, coupled with a narrow beam of radio emission emanating from a small region around the magnetic poles, means that an Earth-based observer sees a regular pulse of radio emission once per rotation. This clock-like behaviour of pulsars has a wide variety of applications, from the testing of theories of gravity. RESULT: We therefore conclude that timing noise remains a factor in millisecond pulsar timing, but less so than once feared. In addition, the large spread in timing noise for given pulsar parameters should mean that there exists some millisecond pulsars with extremely low levels of timinga. distributions b. wavelengths c. wavelets d. particles.
a. noise b. emission c. spread d. regions.
Q92. arXiv:1906.07197 [astro-ph.GA]: Lyα Halos Around z∼6 Quasars: Alyssa B. Drake, Emanuele Paolo Farina, Marcel Neeleman, Fabian Walter, Bram Venemans, Eduardo Banados, Chiara Mazzucchelli, Roberto Decarli. (Submitted on 17 Jun 2019): ABSTRACT: We present deep MUSE observations of five quasars within the first Gyr of the Universe (z≳6 ), four of which display extended Lyα halos. After PSF-subtraction, we reveal halos surrounding two quasars for the first time, as well as confirming the presence of two more halos for which tentative detections exist in long-slit spectroscopic observations and narrow-band imaging. The four Lyα halos presented here are diverse in morphology and size, they each display spatial asymmetry, and none are centred on the position of the quasar. Spectra of the diffuse halos demonstrate that none are dramatically offset in velocity from the systemic redshift of the quasars (Δ v <200kms^−1), however each halo shows a broad Lyα line, with a velocity width of order ∼1000kms^−1. Total Lyα luminosities range between ∼2×10^43erg s^−1 and ∼2× 10^44 erg s^−1, reaching maximum radial extents of 13−30pkpc from the quasar positions. We find larger sizes and higher Lyα luminosities than previous literature results at this redshift, but find no correlation between the quasar properties and the Lyα halo, suggesting that the detected emission is most closely related to the physical properties of the circum-galactic medium. INTRODUCTION The importance of studying the gas immediately surrounding galaxies has long been understood. In particular, as the circum-galactic medium (CGM) lies at the interface between galaxies themselves, and the diffuse hydrogen in the intergalactic medium (IGM) it holds the key to understanding some of the most fundamental concepts of galaxy formation and evolution. CONCLUSIONS: Overall, our results are consistent with a picture in which the physical properties of the CGM evolve with cosmic time, manifesting as an observed evolution of Lyα halo properties. Before this scenario can be confirmed or clarified, a larger sample of QSO observations at z ∼ 6 is called for, and observations of more diagnostic lines (e.g. with the upcoming JWST mission). This will help to elucidate the processes governing the growth of the first galaxies and black
a. entities b. bodies c. times d. holes.
Q93.arXiv:1906.07262 [astro-ph.HE]: Superheavy Gravitinos and Ultra-High Energy Cosmic Rays. Krzysztof A. Meissner, Hermann Nicolai. (Submitted on 17 Jun 2019): ABSTRACT: We argue that the superheavy gravitinos that we had previously proposed as candidates for Dark Matter can offer a possible explanation for the ultra-high energy cosmic ray (UHECR) events observed at the Pierre Auger Observatory, via gravitino anti-gravitino annihilation in the `skin' of neutron stars. The large mass and strong interactions of these particles, together with their stability against decays into standard matter are essential for the proposed explanation to work. In particular, it ensues that UHECR events can be understood to originate from neutron stars inside a GKZ horizon of 50 Mpc. The composition of neutron stars near their surface could play a crucial role in explaining the presence of heavy ions in these events. If confirmed, the present results can be taken as evidence for the fundamental ansatz towards unification on which they are based. INTRODUCTION: This is based on our previous work [5, 6] where we have raised the possibility that dark matter (DM) could consist at least in part of an extremely dilute gas of very massive stable gravitinos, which are furthermore fractionally charged and strongly interacting. As we will argue here these can in principle furnish a fairly simple explanation for the most energetic cosmic ray energy events, both qualitatively and quantitatively. : Both the large gravitino mass and the amount of accumulated mass of these particles, which is on the order of the combined DM mass in the Universe, are necessary to understand the large energies and the rates of the observed UHECR events, as we shall now explain. In addition we need to make one important further assumption concerning the local distribution of DM in stellar systems. CONCLUSIONS: To be sure, the UHECR emitters are not evenly distributed throughout the universe, and we therefore expect an increased number of events to originate from superclusters of galaxies rich in neutron stars (the super-galactic plane, in particular). In particular the integral for NE may receive its dominant contribution from a disk rather than the full ball. We also note that with a maximum available energy of O(10^22 eV) our proposal can also explain the existence of (very rare) UHECR events exceeding the GKZ bound, if these originate from neutron stars within the Milky Way or nearby
a. stars b. galaxies c. quasars d. systems.
Q94. arXiv:1906.07534 [astro-ph.SR]: Cut-off features in interplanetary solar radio type IV emission. Silja Pohjolainen, Nasrin Talebpour Sheshvan. (Submitted on 18 Jun 2019) :ABSTRACT: Solar radio type IV bursts can sometimes show directivity, so that no burst is observed when the source region in located far from the solar disk centre. This has recently been verified also from space observations, at decameter wavelengths, using a 3D-view to the Sun with STEREO and Wind satellites. It is unclear whether the directivity is caused by the emission mechanism, by reduced radio wave formation toward certain directions, or by absorption/blocking of radio waves along the line of sight. We present here observations of three type IV burst events that occurred on 23, 25, and 29 July 2004, and originated from the same active region. The source location of the first event was near the solar disk centre and in the third event near the west limb. Our analysis shows that in the last two events the type IV bursts experienced partial cut-offs in their emission, that coincided with the appearance of shock-related type II bursts. The type II bursts were formed at the flanks and leading fronts of propagating coronal mass ejections (CMEs). These events support the suggestion of absorption toward directions where the type II shock regions are located. INTRODUCTION: Flares and coronal mass ejections (CMEs) are solar transients that can accelerate particles to high energies and create radio emission within large wavelength ranges. The directivity in IP type IV bursts was first reported by Gopalswamy et al. (2016). By comparing the radio spectra observed from three different viewing angles around the Sun (STEREO A and B, and Wind), they observed that the IP type IV bursts are visible only if their source location is within ∼60 degrees from the Sun centre. Their conclusion was that the type IV emission is directed along a narrow cone above the flare site, the emission mechanism is most probably plasma emission, and the type IV bursts are stationary, i.e., not associated with moving CME structures. CONCLUSIONS: We have presented here observations of three radio type IV burst events that occurred on three separate days but originated from the same active region. In the first event the source region was located near the solar disk centre, in the second event near W30, and in the third event near the west limb. Our analysis shows that in the last two events the type IV bursts experienced partial cut-offs in their emission. These two bursts were estimated to be the moving type, i.e., associated with upward-moving CME structures instead of stationary coronal loops. If radio type IV burst emission can be observed only if the burst source is located near the solar disk centre, this could be used to estimate the CME propagation direction. However, this is not possible if the observed directivity is caused by absorption/blocking of the type IV emission toward certain directions. Instead, the effect will tell if high density, shock-related regions are formed within CME structures, and where they may be
a. located b. centered c. moving d. influenced.
Q95. arXiv:1906.07584 [astro-ph.GA]: A radio ridge connecting two galaxy clusters in a filament of the cosmic web. F. Govoni, et al., (Submitted on 18 Jun 2019): ABSTRACT: Galaxy clusters are the most massive gravitationally bound structures in the Universe. They grow by accreting smaller structures in a merging process that produces shocks and turbulence in the intra-cluster gas. We observed a ridge of radio emission connecting the merging galaxy clusters Abell 0399 and Abell 0401 with the Low Frequency Array (LOFAR) at 140 MHz. This emission requires a population of relativistic electrons and a magnetic field located in a filament between the two galaxy clusters. We performed simulations to show that a volume-filling distribution of weak shocks may re-accelerate a pre-existing population of relativistic particles, producing emission at radio wavelengths that illuminates the magnetic ridge. Main Text: The matter distribution of the Universe is not uniform, but forms a cosmic web, with a structure of filaments and galaxy clusters surrounding large voids. Galaxy clusters form at the intersections of the cosmic web filaments and grow by accreting substructures in a merging process, which converts most of the in fall kinetic energy into thermal gas energy. We observed the region between Abell 0399 and Abell 0401 at radio wavelengths to investigate whether relativistic particles and magnetic fields exist on cosmic scales larger than those of galaxy clusters. CONCUSIONS: The non-thermal diffuse emission observed in the Abell 0399 – Abell 0401 system extends far beyond the boundaries of the two radio halos and fills a region in their outskirts which is still dynamically evolving. We interpret this as evidence of intergalactic magnetic fields connecting two galaxy clusters and of spatially distributed particle re-acceleration mechanisms in these
a. spaces b. domains. c. regions d. webs.
Q96.arXiv:1906.07199 [hep-th]: Notes on 8 Majorana Fermions. David Tong, Carl Turner. (Submitted on 17 Jun 2019) ABSTRACT: Eight Majorana fermions in d=1+1 dimensions enjoy a triality that permutes the representation of the SO(8) global symmetry in which the fermions transform. This triality plays an important role in the quantization of the superstring, and in the analysis of interacting topological insulators and the associated phenomenon of symmetric mass generation. The purpose of these notes is to provide an introduction to the triality and its applications, with careful attention paid to various Z2 global and gauge symmetries and their coupling to background spin structures. INTRODUCTION: The essence of the triality is that the fermions in each theory transform in different representations of the SO(8) global symmetry group. (Strictly speaking, this group is either Spin(8) or SO(8)/Z2 as we describe below.) CONCLUSIONS: This can be traced to number of sign choices that were made when the left- and right-handed partition functions were combined. The presence of this preferred spin structure means that it is not obvious how this triality extends to more general Riemann surfaces. It seems reasonable that on a general Riemann surface, a preferred reference spin structure (and a preferred choice of cycles in the first homology, a so-called marking) must be chosen to formulate such a duality. The reason is that such a choice is required in order to unambiguously define the phase of the chiral partition
a. data b. function c. rules d. surface.
a. data b. function c. rules d. surface.
Q97.arXiv:1906.07857 [astro-ph.HE]: On the fallback disk around the slowest isolated pulsar, 1E 161348−5055. Kun Xu, Xiang-Dong Li. (Submitted on 19 Jun 2019): ABSTRACT: The central compact object 1E 161348−5055 in the supernova remnant RCW 103 has a spin period ∼6.67hr, making it the slowest isolated pulsar. It is believed that a supernova fallback disk is required to spin down the neutron star to the current spin period within a few 10^3yr. The mass of the fallback disk around newborn neutron stars can provide useful information on the supernova processes and the possible detection limit with optical/infrared observations. However, it is controversial how massive the disk is in the case of 1E 161348-5055. In this work we simulate the spin evolution of a magnetar that is driven by the interaction between the disk and the star's magnetic field. Compared with previous studies, we take into account various critical conditions that affect the formation and evolution of the fallback disk. Our calculation shows that we can reproduce the extremely slow spin of 1E 161348−5055 when taking the initial disk mass Md∼10^−7M⊙ and the neutron star magnetic field B≥5×10^15 G. This implies that 1E 161348−5055 may be a magnetar with very special initial parameters. However, if future observations reveal more objects like 1E 161348−5055, then stringent constraints can be obtained on the supernova fallback. INTRODUCTION: However, there is no counterpart in optical or radio detected (Tuohy et al. 1983; De Luca et al. 2008), casting doubt on the binary nature. Tendulkar et al. (2017) report the detection of an infrared counterpart with Hubble Space Telescope after the latest outburst. The counterpart properties rule out the binary scenario and mimic the infrared emission of isolated NSs. Observations of outbursts from 1E 1613 and the evolution of the spectral and timing properties along the outburst decay indicate this source to be a magnetar. CONCLUSIONS: More or less massive disks are unable to spin down the NS to 6.67 hr period within ∼ 3 − 4 kyr. This implies that the current state of 1E1613 is actually very difficult to reach, so its evolution can provide very interesting constraints on the supernova fallback model. Among the known magnetars, 1E1613 is the only one with very long spin period. If future observations discover a population of extremely slowly spinning magnetars like 1E1613, it means that either the parameters of supernova fallback occupy a limited range or the model of fallback evolution should be significantly
a. altered b. changed c. limited d. revised.
Q98. arXiv:1906.07890 [astro-ph.SR]: Characterizing dynamical stages of open clusters located in the Sagittarius spiral arm. M. S. Angelo, A. E. Piatti, W. S. Dias, F. F. S. Maia. (Submitted on 19 Jun 2019): ABSTRACT: The study of dynamical properties of Galactic open clusters is a fundamental prerequisite for the comprehension of their dissolution processes. In this work, we characterized 12 open clusters, namely: Collinder 258, NGC 6756, Czernik 37, NGC 5381, Ruprecht 111, Ruprecht 102, NGC 6249, Basel 5, Ruprecht 97, Trumpler 25, ESO 129-SC32 and BH 150, projected against dense stellar fields. In order to do that, we employed Washington CT1 photometry and GAIA DR2 astrometry, combined with a decontamination algorithm applied to the three-dimensional astrometric space of proper motions and parallaxes. From the derived membership likelihoods, we built decontaminated colour-magnitude diagrams, while structural parameters were obtained from King profiles fitting. Our analysis revealed that they are relatively young open clusters (log(t yr^−1) ∼7.3-8.6), placed along the Sagittarius spiral arm, and at different internal dynamical stages. We found that the half-light radius to Jacobi radius ratio, the concentration parameter and the age to relaxation time ratio describe satisfactorily their different stages of dynamical evolution. Those relative more dynamically evolved open clusters have apparently experienced more important low-mass star loss. INTRODUCTION: It is known that the majority of stars are born embedded within giant molecular clouds, and form stellar aggregates named associations or open clusters (OCs). Whilst the first are loose and gravitationally unbound groups (typical dissolution times between ∼ 10−100Myr), the latter are long-lived stellar structures and their diversity in terms of age, stellar content and metallicity makes them ideal tracers of the Galaxy structure, providing information regarding its kinematical evolution and chemical enrichment. CONCLUSIONS: The set of investigated OCs are not in an advanced stage of dynamical evolution, since their concentration parameters span the lower part of the c regime (c <= 0.75). In general, the studied OCs present c values which are within the smallest ones for OCs of similar core radii. Their tidal radii reveal that they are relative small OCs as compared to the sizes of previously studied OCs. We verified a general trend in which the higher the concentration parameter, the higher the age/t rh. Those relative more dynamically evolved OCs have apparently experienced more important low-mass star
a. loss b. gain c. crunch d. abundance.
a. altered b. changed c. limited d. revised.
Q98. arXiv:1906.07890 [astro-ph.SR]: Characterizing dynamical stages of open clusters located in the Sagittarius spiral arm. M. S. Angelo, A. E. Piatti, W. S. Dias, F. F. S. Maia. (Submitted on 19 Jun 2019): ABSTRACT: The study of dynamical properties of Galactic open clusters is a fundamental prerequisite for the comprehension of their dissolution processes. In this work, we characterized 12 open clusters, namely: Collinder 258, NGC 6756, Czernik 37, NGC 5381, Ruprecht 111, Ruprecht 102, NGC 6249, Basel 5, Ruprecht 97, Trumpler 25, ESO 129-SC32 and BH 150, projected against dense stellar fields. In order to do that, we employed Washington CT1 photometry and GAIA DR2 astrometry, combined with a decontamination algorithm applied to the three-dimensional astrometric space of proper motions and parallaxes. From the derived membership likelihoods, we built decontaminated colour-magnitude diagrams, while structural parameters were obtained from King profiles fitting. Our analysis revealed that they are relatively young open clusters (log(t yr^−1) ∼7.3-8.6), placed along the Sagittarius spiral arm, and at different internal dynamical stages. We found that the half-light radius to Jacobi radius ratio, the concentration parameter and the age to relaxation time ratio describe satisfactorily their different stages of dynamical evolution. Those relative more dynamically evolved open clusters have apparently experienced more important low-mass star loss. INTRODUCTION: It is known that the majority of stars are born embedded within giant molecular clouds, and form stellar aggregates named associations or open clusters (OCs). Whilst the first are loose and gravitationally unbound groups (typical dissolution times between ∼ 10−100Myr), the latter are long-lived stellar structures and their diversity in terms of age, stellar content and metallicity makes them ideal tracers of the Galaxy structure, providing information regarding its kinematical evolution and chemical enrichment. CONCLUSIONS: The set of investigated OCs are not in an advanced stage of dynamical evolution, since their concentration parameters span the lower part of the c regime (c <= 0.75). In general, the studied OCs present c values which are within the smallest ones for OCs of similar core radii. Their tidal radii reveal that they are relative small OCs as compared to the sizes of previously studied OCs. We verified a general trend in which the higher the concentration parameter, the higher the age/t rh. Those relative more dynamically evolved OCs have apparently experienced more important low-mass star
a. loss b. gain c. crunch d. abundance.
Q99. arXiv:1906.08271 [astro-ph.GA]: The origin of the Galaxy's system of globular clusters. Davide Massari, Helmer H. Koppelman, Amina Helmi. (Submitted on 19 Jun 2019): ABSTRACT: Context. The assembly history experienced by the Milky Way is currently being unveiled thanks to the data provided the Gaia mission. It is likely that the globular cluster system of our Galaxy has followed a similarly intricate formation path. Aims. To unravel this formation path, we explore the link between the globular clusters and the hitherto known merging events that the Milky Way has experienced. Methods. To this end, we have combined the kinematic information provided by Gaia for almost all Galactic clusters, with the largest sample of cluster ages available after carefully correcting for systematics. To identify clusters with a common origin we analysed their dynamical properties, particularly in the space of integrals of motion. Results. We have found that about 40% of the clusters likely formed in-situ. A similarly large fraction, 35%, can be associated to the merger events, in particular to Gaia-Enceladus (19%), the Sagittarius dwarf galaxy (5%), the progenitor of the Helmi streams (6%) and to the Sequoia galaxy (5%), although some uncertainty remains due to some degree of overlap in their dynamical characteristics. Of the remaining clusters, 16% are tentatively associated to a group with high-binding energy, while the rest are all on loosely bound orbits and likely have a more heterogeneous origin. The resulting age-metallicity relations are remarkably tight and differ in their detailed properties depending on the progenitor, providing further confidence on the associations made. Conclusions. We provide a table listing the associations found which highlights the progress made in sorting out the assembly history of the Galactic globular clusters. Improved kinematic data by future Gaia data releases and especially a larger, systematic-free sample of cluster ages would help to further pin down this history. INTRODUCTION: According to the ΛCDM cosmological paradigm, structure formation proceeds bottom-up, as small structures merge together to build-up the larger galaxies we observe today. The Milky Way is a prime example of this formation mechanism, as demonstrated first by the discovery of the Sagittarius dwarf spheroidal galaxy in the process of disruption, halostellar streams crossing the Solar neighbourhood, and more recently by the discovery of stellar debris from GaiaEnceladus, revealing the last significant merger experienced by our Galaxy. SUMMARY: The remaining 36 clusters could be split in two groups based on orbital energy. While the class of GCs with low binding energy is very heterogeneous and likely has several sites of origin, the low energy (highly-bound) group with 25 tentative members is quite clustered in its dynamical properties and shows a reasonably tight and high-normalisation AMR, possibly suggesting the presence of debris towards the Galactic bulge from a hither to unknown large galaxy.
a. data b. neighbourhood c. galaxy d. merger.
Q100. arXiv:1906.08314 [astro-ph.HE]: The large gamma-ray flare of the FSRQ PKS 0346-27. R. Angioni, R. Nesci, J.D. Finke, S. Buson, S. Ciprini. (Submitted on 19 Jun 2019): ABSTRACT: In this paper, we characterize the first γ -ray flaring episode of the FSRQ PKS 0346-27 (z=0.991), as revealed by Fermi-LAT monitoring data, and the concurrent multi-wavelength variability observed from radio through X-rays. The quasi-simultaneous multi-wavelength coverage allowed us to construct time-resolved spectral energy distributions (SEDs). PKS 0346-27 entered an elevated γ-ray activity state starting from the beginning of 2018. The high-state continued throughout the year, displaying the highest fluxes in May 2018. We find evidence of short-time scale variability down to ∼1.5 hours, which constrains the γ -ray emission region to be compact. The extended flaring period was characterized by a persistently harder spectrum with respect to the quiescent state, indicating changes in the broadband spectral properties of the source. This was confirmed by the multi-wavelength observations, which show a shift in the position of the two SED peaks by ∼2 orders of magnitude in energy and peak flux value. As a result, during the high state the non-thermal jet emission completely outshines the thermal contribution from the dust torus and accretion disk. The broadband SED of PKS 0346-27 transitions from a typical Low-Synchrotron-Peaked (LSP) to the Intermediate-Synchrotron-Peaked (ISP) class, a behavior previously observed in other flaring γ -ray sources. Our one-zone leptonic emission model of the high-state SEDs constrains the γ-ray emission region to have a lower magnetic field, larger radius, and higher maximum electron Lorentz factors with respect to the quiescent SED. Finally, we note that the bright and hard γ -ray spectrum observed during the peak of flaring activity in May 2018 implies that PKS 0346-27 could be a promising target for future ground-based Cherenkov observatories such as the CTA. INTRODUCTION: Radio-loud Active Galactic Nuclei (AGN) are the most common astrophysical source class in the γ-ray sky. Their relativistic jets produced by the central black hole emit bright nonthermal radiation across a wide range of wavelengths and energies, from radio to TeV. The vast majority of γ-ray detected AGN are blazars, i.e. sources where the relativistic jet is aligned at a small angle with the observer’s line of sight, leading to strong relativistic Doppler boosting and beaming effects. CONCLUSIONS: Continued monitoring of the GeV sky by the Fermi-LAT is crucial in order to observe more flaring events from high-redshift (z >= 1) blazars and establish the duty cycles of γ-ray activity in relativistic jets. Moreover, the Fermi-LAT is an invaluable tool in order to trigger pointed observations by ground-based γ-ray observatories such as Cherenkov telescopes, including the upcoming CTA. Therefore, continued operations of the Fermi-LAT into the CTA era would be instrumental in order to gain insight into the physics of blazar jets, both in the local universe and at cosmological
a. data b. neighbourhood c. galaxy d. merger.
Q100. arXiv:1906.08314 [astro-ph.HE]: The large gamma-ray flare of the FSRQ PKS 0346-27. R. Angioni, R. Nesci, J.D. Finke, S. Buson, S. Ciprini. (Submitted on 19 Jun 2019): ABSTRACT: In this paper, we characterize the first γ -ray flaring episode of the FSRQ PKS 0346-27 (z=0.991), as revealed by Fermi-LAT monitoring data, and the concurrent multi-wavelength variability observed from radio through X-rays. The quasi-simultaneous multi-wavelength coverage allowed us to construct time-resolved spectral energy distributions (SEDs). PKS 0346-27 entered an elevated γ-ray activity state starting from the beginning of 2018. The high-state continued throughout the year, displaying the highest fluxes in May 2018. We find evidence of short-time scale variability down to ∼1.5 hours, which constrains the γ -ray emission region to be compact. The extended flaring period was characterized by a persistently harder spectrum with respect to the quiescent state, indicating changes in the broadband spectral properties of the source. This was confirmed by the multi-wavelength observations, which show a shift in the position of the two SED peaks by ∼2 orders of magnitude in energy and peak flux value. As a result, during the high state the non-thermal jet emission completely outshines the thermal contribution from the dust torus and accretion disk. The broadband SED of PKS 0346-27 transitions from a typical Low-Synchrotron-Peaked (LSP) to the Intermediate-Synchrotron-Peaked (ISP) class, a behavior previously observed in other flaring γ -ray sources. Our one-zone leptonic emission model of the high-state SEDs constrains the γ-ray emission region to have a lower magnetic field, larger radius, and higher maximum electron Lorentz factors with respect to the quiescent SED. Finally, we note that the bright and hard γ -ray spectrum observed during the peak of flaring activity in May 2018 implies that PKS 0346-27 could be a promising target for future ground-based Cherenkov observatories such as the CTA. INTRODUCTION: Radio-loud Active Galactic Nuclei (AGN) are the most common astrophysical source class in the γ-ray sky. Their relativistic jets produced by the central black hole emit bright nonthermal radiation across a wide range of wavelengths and energies, from radio to TeV. The vast majority of γ-ray detected AGN are blazars, i.e. sources where the relativistic jet is aligned at a small angle with the observer’s line of sight, leading to strong relativistic Doppler boosting and beaming effects. CONCLUSIONS: Continued monitoring of the GeV sky by the Fermi-LAT is crucial in order to observe more flaring events from high-redshift (z >= 1) blazars and establish the duty cycles of γ-ray activity in relativistic jets. Moreover, the Fermi-LAT is an invaluable tool in order to trigger pointed observations by ground-based γ-ray observatories such as Cherenkov telescopes, including the upcoming CTA. Therefore, continued operations of the Fermi-LAT into the CTA era would be instrumental in order to gain insight into the physics of blazar jets, both in the local universe and at cosmological
a. distances b. thresholds c. range d. jets.
Q101. arXiv:1906.08419 [astro-ph.GA]: The Dark Matter Profiles in the Milky Way. Hai-Nan Lin, Xin Li. (Submitted on 20 Jun 2019): ABSTRACT: We investigate the dark matter profile of the Milky Way using the observed rotation curve data out to 100 kpc. The baryonic matter of the Milky Way is divided into bulge, disk and gas components, and each component is modelled using various possible mass profiles available in literature. The arbitrary combination of seven bulge profiles, four disk profiles and two gas profiles results in fifty-six baryon models. These baryon models are combined with one of the four dark matter profiles: Burkert profile, core-modified profile, pseudo-isothermal profile and NFW profile, to fit the observed rotation curve data. Results show that in general the NFW profile fits the data better than the Burkert profile, while the core-modified profile and the pseudo-isothermal profile are essentially ruled out. The best-fitting NFW model has the scale length r0 =8.1±0.7 kpc, and the corresponding local density of dark matter is ρdm (R=R⊙)=0.51±0.09 GeV/cm^3. INTRODUCTION: In the early 1970s, it was noticed that the luminous mass in some galaxies cannot provides enough gravitational potential to support the observed rotation velocity in the outer of galaxies. This mass missing problem leads to the hypothesis that there is a large amount of non-luminous matter inside the galaxies which has not been seen yet, i.e. the dark matter hypothesis. Later on, the mass missing problem has been discovered in many more galaxies. The observed rotation velocity in the outer galaxy shows obvious deviation from the predicted r^−1/2 law, which implies the existence of dark matter. CONCLUSON: Finally, it should be noticed that there are additional uncertainties arising from the modelling of the baryon profiles. The baryon profiles considered in our paper have not taken into account the rings, the spiral arms, and other irregular structures, which may also affect the rotation velocity. In addition, due to historical reasons some of the baryon profiles may not be consistent with the present knowledge on our Galaxy. More precise observations on the baryon mass of the Milky Way are required to tightly constrain the dark matter
a. profile b. projection c. rings d. distributions.
a. profile b. projection c. rings d. distributions.
Q102. arXiv:1906.09277 [astro-ph.GA]: The Dust-to-Gas and Dust-to-Metals Ratio in Galaxies from z=0-6. Qi Li, Desika Narayanan, Romeel Davé. (Submitted on 21 Jun 2019): ABSTRACT: We present predictions for the evolution of the galaxy dust-to-gas (DGR) and dust-to-metal (DTM) ratios from z=0 to 6, using a model for the production, growth, and destruction of dust grains implemented into the \simba\ cosmological hydrodynamic galaxy formation simulation. In our model, dust forms in stellar ejecta, grows by the accretion of metals, and is destroyed by thermal sputtering and supernovae. Our simulation reproduces the observed dust mass function at z=0, but modestly under-predicts the mass function by ~x3 at z ~ 1-2. The z=0 DGR vs metallicity relationship shows a tight positive correlation for star-forming galaxies, while it is uncorrelated for quenched systems. There is little evolution in the DGR-metallicity relationship between z=0-6. We use machine learning techniques to search for the galaxy physical properties that best correlate with the DGR and DTM. We find that the DGR is primarily correlated with the gas-phase metallicity, though correlations with the depletion timescale, stellar mass and gas fraction are non-negligible. We provide a crude fitting relationship for DGR and DTM vs. the gas-phase metallicity, along with a public code package that estimates the DGR and DTM given a set of galaxy physical properties. INTRODUCTION: Dust plays a critical role in the physics of the interstellar medium (ISM) and galaxy evolution. The surfaces of dust grains catalyze a range of chemical reactions that influence the structure of ISM and star formation. CONCLUSIONS: Overall, the Simba dust model is at least as successful compared with other current dust models implemented in cosmological simulations. However, there remain various caveats and potential directions for improvement. These include having active dust (not tied to the gas), multiple dust grain sizes, and implementing more sophisticated dust cooling. Furthermore, there are various free parameters that are constrained indirectly by observations, which might be better constrained using high-resolution ISM simulation. By using such a multi-scale approach to combine high resolution simulations and observational constraints into a cosmological galaxy formation model, we are moving towards more comprehensively studying the evolution of galaxy dust on cosmological
a. weights b. scales c. times d. cooling.
Q103. arXiv:1906.09612 [astro-ph.GA]: Four newly discovered HII galaxies. O. Garde, P. Le Dû, M. Koenig, P. Dubreuil, A. Lopez, B. Guegan6. (Submitted on 23 Jun 2019): ABSTRACT: We present the results of spectroscopy campaigns for planetary nebula candidates, where we have identified four objects as Seyfert galaxies. All observations have been carried out by a group of French amateur astronomers. During the campaigns at the Cote d'Azur observatory at Calern (France), four HII galaxies could be identified. Using the naming convention of our campaign, these objects are (1) App 1 (RA: 22h 49m 20.23s, DEC: +46°07{\arcmin}37.17{\arcsec}), (2) Pre 21 (RA: 18h 04m 19.62s, DEC: +00°08{\arcmin}04.96{\arcsec}), (3) Pre 24 (RA: 04h 25m 53.63s, DEC: +39°49{\arcmin}19.69{\arcsec}), and (4) Ra 69 (RA: 19h 30m 23.64s, DEC: +37°37{\arcmin}06.58{\arcsec}). CONCLUSIONS: We are fully aware of the fact that our equipment’s capabilities are limited, for example by the low spectral dispersion of our spectra, so we cannot determine properly all emission-line ratios that are typically used for the BPT-classification method. But our intention was to show that amateur astronomers can contribute a small puzzle piece to extragalactic research, by persevering database research and own observation campaigns. Also, it would be interesting to check whether deep optical images can be used to detect details of the galactic discs of the
a. galaxies b. stars c. objects d. spectra.
a. galaxies b. stars c. objects d. spectra.
Q104. arXiv:1906.10316 [astro-ph.GA]: Constraining light fermionic dark matter with binary pulsars. L. Gabriel Gómez. (Submitted on 25 Jun 2019) :ABSTRACT: A binary system embedded in a Dark Matter (DM) background may experience a change in its orbital period due to dynamical friction as the binary moves through a wind of DM particles. We compute such a perturbative effect on the binary evolution considering that DM is constituted of degenerate gas of free fermions. The analysis point out that the secular change of the orbital period is more sensitive, and likely measurable, to degenerate fermions with masses ≳50 eV, depending slightly, but still being distinguishable, on the binary star configuration (e.g. NS-NS, NS-WD and WD-WD). Interestingly, we find that NS-NS binary systems with large orbital periods, Pb≳100 days, experience larger orbital period decays. We also show that this effect is clearly increased, under the former conditions, in binaries orbiting small DM halos, which correspond to extragalactic pulsars. This situation represents the best astrophysical scenario to test such effects of light fermionic DM. We use some available measurements of the orbital period time-derivative for long-period binaries in the Milky-Way to quantify more realistically this effect. For instance, measurements of the J1713+0747 pulsar set an upper bound on the fermion mass of mf≲1keV. This bound can be considerably improved by using pulsar timing observations of extragalactic pulsars. Under this perspective, high precision of timing pulsar observations will reveal whether DM dynamical friction effect may be tested with the upcoming generation of surveys leading to the possibility of constraining more strongly the properties of light fermionic DM. INTRODUCTION: As discussed, fermionic DM may play an important role in the description of cored DM halo 2. We focus then on self-gravitating degenerate gas of free fermions, also known as light (sub-keV) fermions, as a simple but well motivated realization of non-interacting fermionic DM to describe the DM distribution in galaxies. CONCLUSIONS: DM dynamical friction is an appealing effect on the binary evolution because it would permit us to put constraints on the local DM environment the binaries are embedded due to the high-precision measurements which is a characteristic property in such systems. We found as the main conclusion of this work that NS-NS binary systems with large orbital periods Pb >= 100 days orbiting small DM halos, composed of degenerate fermions of mf ∼ 200 eV, (which correspond to extragalactic pulsars), are the best astrophysical scenario to test the effect of dynamical friction of light fermionic DM once observational data of timing pulsar is available. Interestingly, there are promising pulsar surveys that can reach an astonishing sensitivity to test the theoretical predictions based on DM
a. structures b. halos c. models d. systems.
a. structures b. halos c. models d. systems.
Q105. arXiv:1906.10492 [astro-ph.SR]: The spectroscopic binaries RV Tauri and DF Cygni. Rajeev Manick, Devika Kamath, Hans Van Winckel, Alain Jorissen, Sanjay Sekaran, Dominic M. Bowman, Glenn-Michael Oomen, Jacques Kluska, Dylan Bollen, Christoffel Waelkens. (Submitted on 25 Jun 2019) :ABSTRACT: Aim: The focus of this paper is on two famous but still poorly understood RV Tauri stars: RV Tau and DFCyg. We aim at confirming their suspected binary nature and deriving their orbital elements to investigate the impact of their orbits on the evolution of these systems. This research is embedded into a wider endeavour to study binary evolution of low- and intermediate-mass stars. Method: The high amplitude pulsations were cleaned from the radial-velocity data to better constrain the orbital motion. We used Gaia DR2 parallaxes in combination with the SEDs to compute their luminosities which were complemented with the ones computed using a period-luminosity-colour relation. The ratio of the circumstellar infrared flux to the photospheric flux obtained from the SEDs was used to estimate the orbital inclination of each system. Results: DFCyg and RV Tau are binaries with spectroscopic orbital periods of 784±16 days and 1198±17 days, respectively. These orbital periods are found to be similar to the long-term periodic variability in the photometric time series, indicating that binarity indeed explains the long-term photometric variability. Both systems are surrounded by a circum-binary disc which is grazed by our line-of-sight. As a result, the stellar photometric flux is extinct periodically with the orbital period. Our derived orbital inclinations enabled us to obtain accurate companion masses for DFCyg and RV Tau. Analysis of the Kepler photometry of DFCyg revealed a power spectrum with side lobes around the fundamental pulsation frequency. This modulation corresponds to the spectroscopic orbital period and hence to the long-term photometric period. Finally we report on the evidence of high velocity absorption features related to the Hα profile in both objects, indicating outflows launched from around the companion. CONCLUSIONS: We have also analysed the high quality Kepler photometry of DFCyg and found evidence of modulation in the fundamental pulsation peak. The orbital period of the system can be constrained using the sidelobe features and we have shown that it corresponds to the orbital period found from both photometry and spectroscopy. We used a combination of the pulsation periods and the Gaia distances to compute their photospheric luminosities using two methods. The luminosities derived in both cases are in good agreement within their respective errors. Based on the luminosities, we conclude that RVTau is a post-AGB binary, while DFCyg is likely a post-RGB
a. pulsation b. binary c. features d. spectroscopy.
a. pulsation b. binary c. features d. spectroscopy.
Q106. arXiv:1907.10146 [astro-ph.IM]: Status of the Large Size Telescopes of the Cherenkov Telescope Array. Juan Cortina (for the CTA LST project). (Submitted on 19 Jul 2019):ABSTRACT: The Cherenkov Telescope Array (CTA) will consist of two arrays of Imaging Atmospheric Cherenkov Telescopes (IACTs) at the northern and southern hemispheres. CTA will feature IACTs with mirrors of three different sizes optimized to cover different energy ranges. The proposed sub-arrays of four Large Size Telescopes (LST) at CTA-North and CTA-South target the lowest energy range between around 20 GeV and 100 GeV. Thanks to their low weight of around 110 tons the LSTs can move by 180 deg in azimuth in 20 seconds for Gamma Ray Burst (GRB) follow-up. An LST has a tessellated parabolic mirror of 23 m diameter equipped with a system of actuators to correct for gravity-induced deformations during data taking. Its low-weight 2 ton camera at the prime focus has a 4.5 deg diameter, 1855 high QE PMTs and an embedded readout with 1 GSps sampling speed designed for data acquisition rates exceeding 10 kHz. A fully equipped LST has been installed at the CTA-North site in 2018 and is expected to be finished commissioning during 2019. The remaining three LSTs in the north will be installed by 2022. We will review the status of the LSTs, describe the installation of the first LST and report on the first results of the commissioning tests. Introduction: CTA[1] will consist of two arrays of IACTs at the northern and southern hemispheres. The IATCs will have mirrors of three different sizes optimised for different energy ranges. The proposed sub-arrays of four Large Size Telescopes (LST) at CTA-North and CTA-South feature the largest reflectors and target the lowest energies down to a threshold energy of ∼20 GeV. Major physics drivers in the LST energy range are transients, both galactic and extragalactic, pulsars and studies of the Extragalactic Background Light. The design grants special attention to the study of GRBs: the telescope has a very low weight to allow repointing by 180◦ in less than 20 seconds so as to detect the GRB prompt emission. Outlook: We expect to complete the commissioning of LST1 before the end of 2019. Observations with the telescope could then start although the performance of a single LST is significantly worse than the performance of the LST sub-array or the whole CTA-North. The plans to complete the four LSTs at the CTA North site are firm. The schedule of the production follows the funding flow in the countries with responsibilities in the LST project. A good fraction of the components is already available, others are under production. Installation of the telescopes is targeted before the end of 2022 and commissioning during will take place during the next,
a. year b. decade c. month d. observation.
a. year b. decade c. month d. observation.
Q107. arXiv:1907.10224 [astro-ph.GA]: Effects of infall and outflow on massive star-forming regions. Qiang Li, Jianjun Zhou, Jarken Esimbek, Yuxin He, Willem Baan, Dalei Li, Gang Wu, Xindi Tang, Weiguang Ji, Toktarkhan Komesh, Serikbek Sailanbek. (Submitted on 24 Jul 2019): ABSTRACT: A total of 188 high-mass outflows have been identified from a sample of 694 clumps from the Millimetre Astronomy Legacy Team 90 GHz survey, representing a detection rate of approximately 27%. The detection rate of outflows increases from the protostellar stage to the H II stage, but decreases again at the photodissociation (PDR) stage suggesting that outflows are being switched off during the PDR stage. An intimate relationship is found between outflow action and the presence of masers, and water masers appear together with 6.7 GHz methanol masers. Comparing the infall detection rate of clumps with and without outflows, we find that outflow candidates have a lower infall detection rate. Finally, we find that outflow action has some influence on the local environment and the clump itself, and this influence decreases with increasing evolutionary time as the outflow action ceases. INTRODUCTION: Star formation is an intrinsically complex process involving the collapse and accretion of matter onto proto-stellar objects (Lada 1985) and infall and outflow motions play an important role in the star formation processes. However, a comprehensive understanding of both processes, particularly towards massive star-forming regions, is still lacking. In part, this is because of the larger distances involved and the typically more clustered and complex nature of star formation regions, making it difficult to disentangle the infall and outflow properties of individual objects in a given cluster. CONCLUSIONS: Because MALT90 data have higher noise, some outflow candidates are likely not found and the reliability of some candidates may be low. This has some influence on our statistic results. Some data with lower noise is thus needed to further examine the accuracy of our conclusions. In addition, in order to exclude the influence of different clump masses. it is necessary to acquire some data for similar clump mass at the same stage to determine whether there is an obvious difference between clumps with and without
a. inflows b. candidates c. outflow d. masses.
Q108. . arXiv:1907.10375 [astro-ph.GA]: An accurate low-redshift measurement of the cosmic neutral hydrogen density. Wenkai Hu, Laura Hoppmann, Lister Staveley-Smith, Katinka Gereb, Tom Oosterloo, Raffaella Morganti, Barbara Catinella, Luca Cortese, Claudia del P. Lagos, Martin Meyer. (Submitted on 24 Jul 2019): ABSTRACT: Using a spectral stacking technique, we measure the neutral hydrogen (HI) properties of a sample of galaxies at z<0.11 across 35 pointings of the Westerbork Synthesis Radio Telescope (WSRT). The radio data contains 1,895 galaxies with redshifts and positions known from the Sloan Digital Sky Survey (SDSS). We carefully quantified the effects of sample bias, aperture used to extract spectra, sidelobes and weighting technique and use our data to provide a new estimate for the cosmic HI mass density. We find a cosmic HI mass density of ΩHI=(4.02±0.26)×10^−4h−170 at ⟨z⟩=0.066 , consistent with measurements from blind HI surveys and other HI stacking experiments at low redshifts. The combination of the small interferometer beam size and the large survey volume makes our result highly robust against systematic effects due to confusion at small scales and cosmic variance at large scales. Splitting into three sub-samples with ⟨z⟩= 0.038, 0.067 and 0.093 shows no significant evolution of the HI gas content at low redshift. CONCLUSIONS: Rather than attempting to identify, then remove potentially confused targets, which has the effect of removing massive centrals and gas-rich satellites, we corrected for residual confusion using a simulation. We also explore the robustness of the result to the effect of WSRT sidelobes. For both effects, the corrections were found to be small. Finally, we split our sample in three sub-samples with <z> = 0.038, 0.067 and 0.093 and find similar results. Our results agree well with previous ΩHI measurements from HI emission surveys, HI stacking and DLA surveys. Taken together, the results confirm that there seems to be little evolution in ΩHI at low
a. blueshifts b. redshift c. sub-samples d. surveys.
Q109. arXiv:1907.10541 [astro-ph.GA]: Planet formation in clusters. Susanne Pfalzner. (Submitted on 24 Jul 2019){ABSTRACT: One well-tested method in science is to separate the object of interest from its surroundings and look at it in isolation. The advantage is that unimportant information is removed and the true properties of the object are seen more clearly. However, sometimes the influences of the surroundings actually determine the properties of an object. In this case, not taking the environment into account can lead to incomplete or even false conclusions. In the context of planet formation this question arises to: is it sufficient to study the nascent planetary system in isolation? Stars usually do not form in isolation but as part of a stellar group. The first important question in this field is then: How important is the influence of the surrounding stars on circumstellar discs and forming planetary systems?} We can also pose a second question: Does radiation or gravitational interaction dominate? Here I give my perspective on these two questions. INTRODUCTION: The first important question in this field is then: How important is the influence of the surrounding stars on circumstellar discs and forming planetary systems? Distance to other stars in the same system is the key factor here, so the main parameter is obviously the local stellar density. CONCLSIONS: What next? As pointed out above, cluster dynamics is a key factor here. The wealth of the Gaia data will hopefully enable us to put even tighter constraints on the dynamics of young clusters and associations alike. Equally, it would be important to obtain better information on discs in the embedded phase and in dense clusters, which is admittedly an observational challenge. On the theoretical front, it is important to take the newly found observational constraints into account and eventually bridge the still existing gap between cluster formation models and the following phase of cluster expansion (Farias et al. 2019). Moreover, so far it is rarely taken into account that such clusters contain a large fraction of binaries and multiple systems, and future studies should include that. Given the considerable progress during the last few years, I think all these aims are reachable in the neara. inflows b. candidates c. outflow d. masses.
Q108. . arXiv:1907.10375 [astro-ph.GA]: An accurate low-redshift measurement of the cosmic neutral hydrogen density. Wenkai Hu, Laura Hoppmann, Lister Staveley-Smith, Katinka Gereb, Tom Oosterloo, Raffaella Morganti, Barbara Catinella, Luca Cortese, Claudia del P. Lagos, Martin Meyer. (Submitted on 24 Jul 2019): ABSTRACT: Using a spectral stacking technique, we measure the neutral hydrogen (HI) properties of a sample of galaxies at z<0.11 across 35 pointings of the Westerbork Synthesis Radio Telescope (WSRT). The radio data contains 1,895 galaxies with redshifts and positions known from the Sloan Digital Sky Survey (SDSS). We carefully quantified the effects of sample bias, aperture used to extract spectra, sidelobes and weighting technique and use our data to provide a new estimate for the cosmic HI mass density. We find a cosmic HI mass density of ΩHI=(4.02±0.26)×10^−4h−170 at ⟨z⟩=0.066 , consistent with measurements from blind HI surveys and other HI stacking experiments at low redshifts. The combination of the small interferometer beam size and the large survey volume makes our result highly robust against systematic effects due to confusion at small scales and cosmic variance at large scales. Splitting into three sub-samples with ⟨z⟩= 0.038, 0.067 and 0.093 shows no significant evolution of the HI gas content at low redshift. CONCLUSIONS: Rather than attempting to identify, then remove potentially confused targets, which has the effect of removing massive centrals and gas-rich satellites, we corrected for residual confusion using a simulation. We also explore the robustness of the result to the effect of WSRT sidelobes. For both effects, the corrections were found to be small. Finally, we split our sample in three sub-samples with <z> = 0.038, 0.067 and 0.093 and find similar results. Our results agree well with previous ΩHI measurements from HI emission surveys, HI stacking and DLA surveys. Taken together, the results confirm that there seems to be little evolution in ΩHI at low
a. blueshifts b. redshift c. sub-samples d. surveys.
a. scenario b. time c. decades d. future.
Q110. arXiv:1908.03413 [astro-ph.HE]: Constraining Axion Mass through Gamma-ray Observations of Pulsars. Sheridan J. Lloyd, Paula M. Chadwick, Anthony M. Brown. (Submitted on 9 Aug 2019): ABSTRACT: We analyze 9 years of PASS 8 Fermi -LAT data in the 60 − 500 MeV range and determine flux upper limits (UL) for 17 gamma-ray dark pulsars as a probe of axions produced by nucleon-nucleon Bremsstrahlung in the pulsar core. Using a previously published axion decay gamma-ray photon flux model for pulsars which relies on a high core temperature of 20 MeV, we improve the determination of the UL axion mass (ma), at 95 percent confidence level, to 9.6 ×10^−3 eV, which is a factor of 8 improvement on previous results. We show that the axion emissivity (energy loss rate per volume) at realistic lower pulsar core temperatures of 4 MeV or less is reduced to such an extent that axion emissivity and the gamma-ray signal becomes negligible. We consider an alternative emission model based on energy loss rate per mass to allow ma to be constrained with Fermi-LAT observations. This model yields a plausible UL ma of 10^−6 eV for pulsar core temperature < 0.1 MeV but knowledge of the extent of axion to photon conversion in the pulsar B field would be required to make a precise UL axion mass determination. The peak of axion flux is likely to produce gamma-rays in the ≤ 1 MeV energy range and so future observations with medium energy gamma-ray missions, such as AMEGO and e-ASTROGAM, will be vital to further constrain UL ma. :INTRODUCTION: The axion, a Nambu-Goldstone boson, is a solution to the strong CP problem of QCD and a plausible cold dark matter candidate. Galactic halo axions convert to microwave photons in a magnetic field, excluding ma in the range (1.9-3.53) × 10^-6 eV. The axion has a mass ma which is related to the PecceiQuinn scale fa through a scaling relation. ma ≈ 6µeV( fa /10^12 GeV)^-1 . CONCLUSIONS: We analyze data from 17 nearby pulsars using 9 years of Fermi-LAT data and detect none. Using the UL photon flux and the astrophysical model which assumes a pulsar core temperature of 20 MeV we determine an improved UL axion mass (ma) of 0.96 and 3.21 × 10^-2 eV for axions of energy 100 MeV and 200 MeV respectively. However, we show that at realistic pulsar core temperatures of <4 MeV, axion emissivity is so reduced that is unlikely a reasonable determination of UL ma can be made with this method. An alternative axion energy loss rate model yields a plausible range of UL ma values assuming low pulsar core temperatures but requires both the core temperature and the axion to photon conversion probability to be known to set a useful limit. Observation of the un-pulsed gamma-ray emission of our selected pulsar sample with future medium energy gamma-ray observatories such as AMEGO and e-ASTROGAM may allow a better determination of
a. UL b. ULb c. ULd d. UL ma.
Q111. arXiv:1908.03430 [astro-ph.CO]: The Novel Probes Project -- Tests of Gravity on Astrophysical Scales.Tessa Baker, Alexandre Barreira, Harry Desmond, Pedro Ferreira, Bhuvnesh Jain, Kazuya Koyama, Baojiu Li, Lucas Lombriser, Andrina Nicola, Jeremy Sakstein, Fabian Schmidt. (Submitted on 9 Aug 2019) :ABSTRACT: We introduce The Novel Probes Project, an initiative to advance the field of astrophysical tests of the dark sector by creating a forum that connects observers and theorists. This review focuses on tests of gravity and is intended to be of use primarily to observers, but also to theorists with interest in the development of experimental tests. It is twinned with a separate review on tests of dark matter self-interactions (Adhikari et al., in prep.). Our focus is on astrophysical probes of gravity in the weak-field regime, ranging from stars to quasilinear cosmological scales. These are complementary to both strong-field tests and background and linear probes in cosmology. In particular, the nonlinear screening mechanisms that are an integral part of viable modified gravity models lead to characteristic signals specifically on astrophysical scales. The constraining power of these signals is not limited by cosmic variance, but comes with the challenge of building robust theoretical models of the nonlinear dynamics of stars, galaxies, clusters and large scale structure. In this review we lay the groundwork for a thorough exploration of the astrophysical regime with an eye to using the current and next generation of observations for tests of gravity. We begin by setting the scene for how theories beyond General Relativity are expected to behave, focusing primarily on screened fifth forces. We describe the analytic and numerical techniques for exploring the pertinent astrophysical systems, as well as the signatures of modified gravity. With these in hand we present a range of observational tests, and discuss prospects for future measurements and theoretical developments. CONCLUSIONS: Laboratory tests of gravity: It was realized a few years ago [568–570] that sufficiently low-density environments in vacuum chambers should allow tests of the chameleon screening mechanism in the laboratory. Likewise, tests of axion physics in the laboratory have been proposed. Any new ways to constrain screening or other modified gravity effects in the laboratory could be powerful, considering the repeatable nature and sensitivity achievable with modern
a. apparatus b. tests c. effects d. chambers.
Q112. arXiv:1908.09926 [astro-ph.HE]: Eight Millisecond Pulsars Discovered in the Arecibo PALFA Survey. E. Parent, V. M. Kaspi, S. M. Ransom, P. C. C. Freire, A. Brazier, F. Camilo, S. Chatterjee, J. M. Cordes, F. Crawford, J. S. Deneva, R. D. Ferdman, J. W. T. Hessels, J. van Leeuwen, A. G. Lyne, E. C. Madsen, M. A. McLaughlin, C. Patel, P. Scholz, I. H. Stairs, B. W. Stappers, W.W. Zhu. (Submitted on 26 Aug 2019): ABSTRACT: We report on eight millisecond pulsars (MSPs) in binary systems discovered with the Arecibo PALFA survey. Phase-coherent timing solutions derived from 2.5 to 5 years of observations carried out at Arecibo and Jodrell Bank observatories are provided. PSR J1921+1929 is a 2.65-ms pulsar in a 39.6-day orbit for which we detect γ -ray pulsations in archival Fermi data. PSR J1928+1245 is a very low-mass-function system with an orbital period of 3.3 hours that belongs to the non-eclipsing black widow population. We also present PSR J1932+1756, the longest-orbital-period (41.5 days) intermediate-mass binary pulsar known to date. In light of the numerous discoveries of binary MSPs over the past years, we characterize the Galactic distribution of known MSP binaries in terms of binary class. Our results support and strengthen previous claims that the scatter in the Galactic scale height distribution correlates inversely with the binary mass function. We provide evidence of observational biases against detecting the most recycled pulsars near the Galactic plane, which overestimates the scale height of lighter systems. A possible bimodality in the mass function of MSPs with massive white dwarfs is also reported. DETAILS: Millisecond pulsars (MSPs) are short-period (P < ~ 100ms) neutron stars that differ from normal pulsars primarily because of their remarkably small spin-down rates ( ˙ P <~ 10^−17) and their different evolutionary histories. CONCLUSIONS: Among the discoveries are (1) a black widow pulsar (PSR J1928+1245) for which we do not detect eclipses, (2) a new γ-ray MSP (PSR J1921+1929) that we associate with a Fermi point source, and (3) an intermediate-mass binary pulsar (PSR J1932+1756) in a low-eccentricity orbit with a massive WD. Seven of the new discoveries are very fast-spinning (P <6ms), binary MSPs deep in the Galactic plane, which are particularly difficult to detect as a result of pulse dispersion and scattering by the dense interstellar medium. Most systems are in nearly circular orbits in which the most probable companions are He WDs. Except for γ-ray pulsations from PSR J1921+1929, we do not detect any other multiwavelength counterparts or possible associations to the
a. UL b. ULb c. ULd d. UL ma.
Q111. arXiv:1908.03430 [astro-ph.CO]: The Novel Probes Project -- Tests of Gravity on Astrophysical Scales.Tessa Baker, Alexandre Barreira, Harry Desmond, Pedro Ferreira, Bhuvnesh Jain, Kazuya Koyama, Baojiu Li, Lucas Lombriser, Andrina Nicola, Jeremy Sakstein, Fabian Schmidt. (Submitted on 9 Aug 2019) :ABSTRACT: We introduce The Novel Probes Project, an initiative to advance the field of astrophysical tests of the dark sector by creating a forum that connects observers and theorists. This review focuses on tests of gravity and is intended to be of use primarily to observers, but also to theorists with interest in the development of experimental tests. It is twinned with a separate review on tests of dark matter self-interactions (Adhikari et al., in prep.). Our focus is on astrophysical probes of gravity in the weak-field regime, ranging from stars to quasilinear cosmological scales. These are complementary to both strong-field tests and background and linear probes in cosmology. In particular, the nonlinear screening mechanisms that are an integral part of viable modified gravity models lead to characteristic signals specifically on astrophysical scales. The constraining power of these signals is not limited by cosmic variance, but comes with the challenge of building robust theoretical models of the nonlinear dynamics of stars, galaxies, clusters and large scale structure. In this review we lay the groundwork for a thorough exploration of the astrophysical regime with an eye to using the current and next generation of observations for tests of gravity. We begin by setting the scene for how theories beyond General Relativity are expected to behave, focusing primarily on screened fifth forces. We describe the analytic and numerical techniques for exploring the pertinent astrophysical systems, as well as the signatures of modified gravity. With these in hand we present a range of observational tests, and discuss prospects for future measurements and theoretical developments. CONCLUSIONS: Laboratory tests of gravity: It was realized a few years ago [568–570] that sufficiently low-density environments in vacuum chambers should allow tests of the chameleon screening mechanism in the laboratory. Likewise, tests of axion physics in the laboratory have been proposed. Any new ways to constrain screening or other modified gravity effects in the laboratory could be powerful, considering the repeatable nature and sensitivity achievable with modern
a. apparatus b. tests c. effects d. chambers.
Q112. arXiv:1908.09926 [astro-ph.HE]: Eight Millisecond Pulsars Discovered in the Arecibo PALFA Survey. E. Parent, V. M. Kaspi, S. M. Ransom, P. C. C. Freire, A. Brazier, F. Camilo, S. Chatterjee, J. M. Cordes, F. Crawford, J. S. Deneva, R. D. Ferdman, J. W. T. Hessels, J. van Leeuwen, A. G. Lyne, E. C. Madsen, M. A. McLaughlin, C. Patel, P. Scholz, I. H. Stairs, B. W. Stappers, W.W. Zhu. (Submitted on 26 Aug 2019): ABSTRACT: We report on eight millisecond pulsars (MSPs) in binary systems discovered with the Arecibo PALFA survey. Phase-coherent timing solutions derived from 2.5 to 5 years of observations carried out at Arecibo and Jodrell Bank observatories are provided. PSR J1921+1929 is a 2.65-ms pulsar in a 39.6-day orbit for which we detect γ -ray pulsations in archival Fermi data. PSR J1928+1245 is a very low-mass-function system with an orbital period of 3.3 hours that belongs to the non-eclipsing black widow population. We also present PSR J1932+1756, the longest-orbital-period (41.5 days) intermediate-mass binary pulsar known to date. In light of the numerous discoveries of binary MSPs over the past years, we characterize the Galactic distribution of known MSP binaries in terms of binary class. Our results support and strengthen previous claims that the scatter in the Galactic scale height distribution correlates inversely with the binary mass function. We provide evidence of observational biases against detecting the most recycled pulsars near the Galactic plane, which overestimates the scale height of lighter systems. A possible bimodality in the mass function of MSPs with massive white dwarfs is also reported. DETAILS: Millisecond pulsars (MSPs) are short-period (P < ~ 100ms) neutron stars that differ from normal pulsars primarily because of their remarkably small spin-down rates ( ˙ P <~ 10^−17) and their different evolutionary histories. CONCLUSIONS: Among the discoveries are (1) a black widow pulsar (PSR J1928+1245) for which we do not detect eclipses, (2) a new γ-ray MSP (PSR J1921+1929) that we associate with a Fermi point source, and (3) an intermediate-mass binary pulsar (PSR J1932+1756) in a low-eccentricity orbit with a massive WD. Seven of the new discoveries are very fast-spinning (P <6ms), binary MSPs deep in the Galactic plane, which are particularly difficult to detect as a result of pulse dispersion and scattering by the dense interstellar medium. Most systems are in nearly circular orbits in which the most probable companions are He WDs. Except for γ-ray pulsations from PSR J1921+1929, we do not detect any other multiwavelength counterparts or possible associations to the
a. pulsations b. massive WD c. pulsars d. medium.
Q113. arXiv:1908.10115 [astro-ph.GA]: Effect of galaxy mergers on star formation rates. W. J. Pearson, L. Wang, M. Alpaslan, I. Baldry, M. Bilicki, M. J. I. Brown, M. W. Grootes, B. W. Holwerda, T. D. Kitching, S. Kruk, F. F. S. van der Tak. (Submitted on 27 Aug 2019):ABSTRACT: Galaxy mergers and interactions are an integral part of our basic understanding of how galaxies grow and evolve over time. However, the effect that galaxy mergers have on star formation rates (SFR) is contested, with observations of galaxy mergers showing reduced, enhanced and highly enhanced star formation. We aim to determine the effect of galaxy mergers on the SFR of galaxies using statistically large samples of galaxies, totalling over 200\,000, over a large redshift range, 0.0 to 4.0. We train and use convolutional neural networks to create binary merger identifications (merger or non-merger) in the SDSS, KiDS and CANDELS imaging surveys. We then compare the galaxy main sequence subtracted SFR of the merging and non-merging galaxies to determine what effect, if any, a galaxy merger has on SFR. We find that the SFR of merging galaxies are not significantly different from the SFR of non-merging systems. The changes in the average SFR seen in the star forming population when a galaxy is merging are small, of the order of a factor of 1.2. However, the higher the SFR above the galaxy main sequence, the higher the fraction of galaxy mergers. Galaxy mergers have little effect on the SFR of the majority of merging galaxies compared to the non-merging galaxies. The typical change in SFR is less than 0.1~dex in either direction. Larger changes in SFR can be seen but are less common. The increase in merger fraction as the distance above the galaxy main sequence increases demonstrates that galaxy mergers can induce starbursts. DETAILS: More recent observations have shown that merger induced starbursts are found in the minority of merging systems. These studies have found that the typical increase in star formation rate (SFR) of a merger is at most a factor of two, much lower than what would typically be considered a starburst. Work by Knapen et al. has shown that the majority of galaxy mergers are found to cause a reduction in the SFR when compared to non-merging galaxies of comparable stellar masses. CONCLUSIONS: Instead of directly examining the fraction of starburst galaxies that are mergers, we examine the merger fraction as a function of distance above the MS. For the SDSS, CANDELS and KiDS the fraction of mergers increases as the distance above the MS increases. This is evidence that merger scan cause periods of enhanced star formation. Our current work does not determine the stage of the galaxy merger but we can see by eye that our merger samples include mergers at different stages. Thus, it is possible that the period during which SFR is boosted significantly is very short during the merging process and missed within our more time averaged analysis. It could also be that SFR is only boosted significantly for a small fraction of merger types or a combination of both scenarios. Future work will aim to overcome these shortcomings by determining the merger
a. period b. stage c. range d. scenario.
a. period b. stage c. range d. scenario.
Q114. arXiv:1908.09841 [hep-ph]: Dark Matter and Naturalness. Mark P. Hertzberg, McCullen Sandora. (Submitted on 26 Aug 2019): ABSTRACT: The Standard Model of particle physics is governed by Poincaré symmetry, while all other symmetries, exact or approximate, are essentially dictated by theoretical consistency with the particle spectrum. On the other hand, many models of dark matter exist that rely upon the addition of new added global symmetries in order to stabilize the dark matter particle and/or achieve the correct abundance. In this work we begin a systematic exploration into truly natural models of dark matter, organized by only relativity and quantum mechanics, without the appeal to any additional global symmetries, no fine-tuning, and no small parameters. We begin by reviewing how singlet dark sectors based on spin 0 or spin 1/2 should readily decay, while pure strongly coupled spin 1 models have an overabundance problem. This inevitably leads us to construct chiral models with spin 1/2 particles charged under confining spin 1 particles. This leads to stable dark matter candidates that are analogs of baryons, with a confinement scale that can be naturally O(100)TeV. This leads to the right freeze-out abundance by annihilating into massless unconfined dark fermions. The minimal model involves a dark copy of SU(3)×SU(2) with 1 generation of chiral dark quarks and leptons. The presence of massless dark leptons can potentially give rise to a somewhat large value of ΔNeff during BBN. In order to not upset BBN one may either appeal to a large number of heavy degrees of freedom beyond the Standard Model, or to assume the dark sector has a lower reheat temperature than the visible sector, which is also natural in this framework. This reasoning provides a robust set of dark matter models that are entirely natural. Some are concrete realizations of the nightmare scenario in which dark matter may be very difficult to detect, which may impact future search techniques. DETAILS: Furthermore, we will focus on models that are described by an effective field theory that has a cutoff well above the mass of the dark matter particle(s). The rules of relativity and quantum mechanics then leave only 5 possibilities for the spin of the particles s = 0, 1/2, 1, 3/2, 2, since it is thought there is no consistent effective field theory of particles of spin s > 2 with a high cutoff. Furthermore, we know s = 2 is the graviton, which is definitely not the dark matter (we assume a massless graviton here). Also the case s = 3/2 requires the introduction of supergravity, which is an interesting possibility, but we will not pursue this subject here (in any case, one would need to explain why it has a relatively low breaking scale for it to be relevant here). So our focus here will be on the only remaining possibilities for the spins of particles in the dark sector, namely s = 0, 1/2 , 1. CONCLUSIONS: Our simple estimates of the post-inflationary era suggest that the temperature of the dark sector may in fact be appreciably smaller (perhaps a factor of 10 or so) than the visible sector (unless one considers pseudo scalar inflatons or models with photon mixing, etc). If true, this would imply that the correction to Neff is essentially unobservable. Also, the simplest models have tiny scattering cross sections, meaning that they do not lead to any appreciable scattering in the galaxy. Furthermore, since many of the above classes of models have no renormalizable couplings to the Standard Model, and yet still produces a beautiful dark matter candidate, it seriously introduces the possible “nightmare scenario” in which dark matter will remain extremely difficult, if not impossible, to detect. Although this may seem unfortunate, it is a logically consistent possibility, and has completely natural embeddings within particle physics as seen here. In this case, new future search techniques would be
a. inappropriate b. undecided c. exemplary d. appropriate.
Q115. arXiv:1810.10686 [astro-ph.GA]: Magnetic Properties of Dust Grains, Effect of Precession and Radiative Torque Alignment. A Lazarian, Thiem Hoang. (Submitted on 25 Oct 2018 (v1), last revised 27 Aug 2019 (this version, v2)): ABSTRACT: Alignment of dust grains in astrophysical environments results in the polarization of starlight as well as the polarization of radiation emitted by dust. We demonstrate the advances in grain alignment theory allow the use of linear and circular polarization to probe not only the magnetic field, but also dust composition, the dust environment, etc. We revisit the process of grain alignment by Radiative Torques (RATs) and focus on constraining magnetic susceptibility of grains via observations. We discuss the possibility of observational testing of the magnetic properties of grains as the alignment changes from being in respect to the magnetic field to being in respect to the radiation direction. This opens both a possibility of constraining the uncertain parameters of the RATs theory and provides a new way of measuring magnetic fields in interstellar medium and circumstellar regions. We provide a detailed discussion of the precession induced both by the magnetic field and the anisotropic radiation and revisit a number of key processes related to magnetic response of the grains. We consider various effects that increase the rate of magnetic relaxation both in silicate and carbonaceous grains. In particular, we find a new relaxation process related to the change of the amplitude of internal magnetization within a wobbling triaxial grain and identify a range of grain sizes in which this effect can dominate the internal alignment of angular momentum within grain axes. We show that these relaxation processes significantly change the dynamics of grains in the presence of RATs. We apply our analysis for observed grain alignment in special environments to put constraints on the enhanced magnetic properties of dust grains in the cloud near supernovae, in cometary coma, and protoplanetary disks. DETAILS: Magnetic fields play a crucial role in many astrophysical processes, e.g., star formation, accretion of matter, transport processes, including heat conduction and propagation of cosmic rays. One of the easiest ways to study magnetic field topology is via polarization of radiation arising from extinction or/and emission by aligned dust grains. CONCLUSIONS: Our estimates of magnetic susceptibilities for dust grains provide the lower limit of the enhancement of 10, relative to the ordinary paramagnetic material, for sub-micron sized grains in the supernovae environment and cometary coma where the alignment is found to be along the magnetic field. We also find an upper limit of 1000 for mm-sized grains in protoplanetary disks where there is observational evidence for grains being aligned with the radiation direction. With the better constrained knowledge of the magnetic susceptibilities the transfer from B- to k-alignment provides a new way of measuring the strength of magnetic field. The alignment of carbonaceous and silicate grains by B-RATs and k-RATs is different, and such difference in the alignment direction of these two types of grains can shed light on the nature of the anomalous randomization of grains that is related to the interaction of grain electric moment with electric field arising from the grain motion in magnetic field.
a. direction b. field c. strength d. susceptibility.
a. inappropriate b. undecided c. exemplary d. appropriate.
Q115. arXiv:1810.10686 [astro-ph.GA]: Magnetic Properties of Dust Grains, Effect of Precession and Radiative Torque Alignment. A Lazarian, Thiem Hoang. (Submitted on 25 Oct 2018 (v1), last revised 27 Aug 2019 (this version, v2)): ABSTRACT: Alignment of dust grains in astrophysical environments results in the polarization of starlight as well as the polarization of radiation emitted by dust. We demonstrate the advances in grain alignment theory allow the use of linear and circular polarization to probe not only the magnetic field, but also dust composition, the dust environment, etc. We revisit the process of grain alignment by Radiative Torques (RATs) and focus on constraining magnetic susceptibility of grains via observations. We discuss the possibility of observational testing of the magnetic properties of grains as the alignment changes from being in respect to the magnetic field to being in respect to the radiation direction. This opens both a possibility of constraining the uncertain parameters of the RATs theory and provides a new way of measuring magnetic fields in interstellar medium and circumstellar regions. We provide a detailed discussion of the precession induced both by the magnetic field and the anisotropic radiation and revisit a number of key processes related to magnetic response of the grains. We consider various effects that increase the rate of magnetic relaxation both in silicate and carbonaceous grains. In particular, we find a new relaxation process related to the change of the amplitude of internal magnetization within a wobbling triaxial grain and identify a range of grain sizes in which this effect can dominate the internal alignment of angular momentum within grain axes. We show that these relaxation processes significantly change the dynamics of grains in the presence of RATs. We apply our analysis for observed grain alignment in special environments to put constraints on the enhanced magnetic properties of dust grains in the cloud near supernovae, in cometary coma, and protoplanetary disks. DETAILS: Magnetic fields play a crucial role in many astrophysical processes, e.g., star formation, accretion of matter, transport processes, including heat conduction and propagation of cosmic rays. One of the easiest ways to study magnetic field topology is via polarization of radiation arising from extinction or/and emission by aligned dust grains. CONCLUSIONS: Our estimates of magnetic susceptibilities for dust grains provide the lower limit of the enhancement of 10, relative to the ordinary paramagnetic material, for sub-micron sized grains in the supernovae environment and cometary coma where the alignment is found to be along the magnetic field. We also find an upper limit of 1000 for mm-sized grains in protoplanetary disks where there is observational evidence for grains being aligned with the radiation direction. With the better constrained knowledge of the magnetic susceptibilities the transfer from B- to k-alignment provides a new way of measuring the strength of magnetic field. The alignment of carbonaceous and silicate grains by B-RATs and k-RATs is different, and such difference in the alignment direction of these two types of grains can shed light on the nature of the anomalous randomization of grains that is related to the interaction of grain electric moment with electric field arising from the grain motion in magnetic field.
a. direction b. field c. strength d. susceptibility.
Q116.arXiv:1908.10873 [astro-ph.EP]: An empirical infrared transit spectrum of Earth: opacity windows and biosignatures. Evelyn J. R. Macdonald, Nicolas B. Cowan. (Submitted on 28 Aug 2019): ABSTRACT: The Atmospheric Chemistry Experiment's Fourier Transform Spectrometer on the SCISAT satellite has been measuring infrared transmission spectra of Earth during Solar occultations since 2004. We use these data to build an infrared transit spectrum of Earth. Regions of low atmospheric opacity, known as windows, are of particular interest, as they permit observations of the planet's lower atmosphere. Even in the absence of clouds or refraction, imperfect transmittance leads to a minimum effective thickness of h min ≈4 km in the 10^--12 μm opacity window at a spectral resolution of R= 10^3. Nonetheless, at R= 10^5, the maximum transmittance at the surface is around 70%. In principle, one can probe the troposphere of an Earth-like planet via high-dispersion transit spectroscopy in the mid-infrared; in practice aerosols and/or refraction likely make this impossible. We simulate the transit spectrum of an Earth-like planet in the TRAPPIST-1 system. We find that a long-term near-infrared campaign with JWST could readily detect CO2 and H2O, establishing the presence of an atmosphere. A mid-IR campaign or longer NIR campaign would be more challenging, but in principle could detect the biosignatures O3 and CH4. DETAILS: Spectroscopy is an observational method in which the flux of a star is measured as a function of wavelength during a planet’s transit. The partial obstruction of the star by the planet causes a decrease in flux proportional to the planet’s cross-sectional area. Absorption and scattering of photons by the planet’s atmosphere cause an additional, wavelength-dependent flux decrease. A rocky planet’s apparent radius is equal to the radius of the solid planet plus a wavelength-dependent term representing the contribution of its atmosphere to its transit depth; this is the atmosphere’s effective thickness. CONCLUSIONS: spectroscopy is an observational method in which the flux of a star is measured as a function of wavelength during a planet’s transit. The partial obstruction of the star by the planet causes a decrease in flux proportional to the planet’s cross-sectional area. Absorption and scattering of photons by the planet’s atmosphere cause an additional, wavelength-dependent flux decrease (Kreidberg 2017). A rocky planet’s apparent radius is equal to the radius of the solid planet plus a wavelength-dependent term representing the contribution of its atmosphere to its transit depth; this is the atmosphere’s effective
a. strength b. power c. thickness d. obstruction.
Q117. arXiv:1908.10878 [astro-ph.SR]: xions as a probe of solar metals. Joerg Jaeckel, Lennert J. Thormaehlen. (Submitted on 28 Aug 2019): ABSTRACT: If axions or axion-like particles exist and are detected, they will not only extend the standard model of particle physics but will also open a new way to probe their sources. Axion helioscopes aim to detect axions which are produced in the core of the sun. Their spectrum contains information about the solar interior and could in principle help to solve the conflict between high and low metallicity solar models. Using the planned International Axion Observatory (IAXO) as an example, we show that helioscopes could measure the strength of characteristic emission peaks caused by the presence of heavier elements with good precision. In order to determine unambiguously the elemental abundances from this information, an improved modelling of the states of atoms inside the solar plasma is required. DETAILS: Axions are light, weakly interacting pseudoscalar particles originally proposed to solve the strong CP problem . Axions as well as their relatives, axion-like particles, have since become attractive dark matter candidates and may also be able to explain astrophysical observations such as the anomalous cooling of stellar objects and the gamma-ray transparency of the universe. For simplicity we will henceforth just talk about axions, but axion-like particles are meant to be included. CONCLUSIONS: If axions are detected in the near future, they can provide a novel probe of the interior of our sun. We have shown that, in suitable regions of the axion parameter space, a helioscope like IAXO, equipped with sufficiently good energy resolving detectors, would allow a measurement of the strength of characteristic emission peaks in the axion spectrum. These peaks are due to the presence of heavier elements, most notably iron, neon and oxygen that are relevant to the solar abundance problem. As the peak strength is related to the elemental abundance, such a measurement could be an extremely powerful tool in resolving the solar abundance problem. Crucially, to realise this potential, an improved precision in the modelling of the atomic emission lines inside the plasma is mandatory. Turned around, such a measurement could also be used to test this modelling, e.g. by measuring different emission lines of the same
a. emission b. element c. spectrum d. plasma.
Q118. arXiv:1908.10988 [astro-ph.SR]: Spectroscopic Follow-Up of Discoveries from the NEOWISE Proper Motion Survey. Jennifer J. Greco, Adam C. Schneider, Michael C. Cushing, J. Davy Kirkpatrick, Adam J. Burgasser. (Submitted on 28 Aug 2019): ABSTRACT: We present low-resolution near-infrared spectra of discoveries from an all-sky proper motion search conducted using multi-epoch data from the Wide-field Infrared Survey Explorer. Using the data from NEOWISE, along with the AllWISE catalogue, (2016) conducted an all-sky proper motion survey to search for nearby objects with high proper motions. Here, we present a follow-up spectroscopic survey of 65 of their discoveries, which focused primarily on potentially nearby objects (d < 25 pc), candidate late-type brown dwarfs (>L7), and subdwarf candidates. We found 31 new M dwarfs, 18 new L dwarfs, and 11 new T dwarfs. Of these, 13 are sub dwarfs, including one new sdL1 and two new sdL7s. Eleven of these discoveries, with spectral types ranging from M7 to T7 (including one subdwarf) are predicted to be within 25 pc, adding to the number of known objects in the solar neighbourhood. We also discovered three new early-type T subdwarf candidates, one sdT1, one sdT2, and one sdT3, which would increase the number of known early-type T sub dwarfs from two to five. CONCLUSIONS: All three of the extreme sub dwarfs in our sample have v tan >= 250 km/s, putting them in the halo, as expected of older, lower metallicity sub dwarfs, which tend to be kinematically associated with the halo population. The dwarfs in our sample are likely clustered in the thin disk, though it is likely some are also in the thick disk. The sub dwarfs in our sample are likely distributed throughout the thick and thin disk. Three of our dwarfs have tangential velocities that place them in the halo: WISE 0101+0336 (355.0 ± 30.1 km/s), WISE 0924+0723 (290 ± 26 km/s), and WISE 1113+5010 (460 ± 76 km/s). The velocity of WISE 1113+5010 is approaching the escape velocity of the Galaxy, which is vtan=528(+24 or −25) km/s at the Sun’s
a. disk b. surface c. direction d. position.
a. Photon b. Dust c. captured d. Particle
a. strength b. power c. thickness d. obstruction.
Q117. arXiv:1908.10878 [astro-ph.SR]: xions as a probe of solar metals. Joerg Jaeckel, Lennert J. Thormaehlen. (Submitted on 28 Aug 2019): ABSTRACT: If axions or axion-like particles exist and are detected, they will not only extend the standard model of particle physics but will also open a new way to probe their sources. Axion helioscopes aim to detect axions which are produced in the core of the sun. Their spectrum contains information about the solar interior and could in principle help to solve the conflict between high and low metallicity solar models. Using the planned International Axion Observatory (IAXO) as an example, we show that helioscopes could measure the strength of characteristic emission peaks caused by the presence of heavier elements with good precision. In order to determine unambiguously the elemental abundances from this information, an improved modelling of the states of atoms inside the solar plasma is required. DETAILS: Axions are light, weakly interacting pseudoscalar particles originally proposed to solve the strong CP problem . Axions as well as their relatives, axion-like particles, have since become attractive dark matter candidates and may also be able to explain astrophysical observations such as the anomalous cooling of stellar objects and the gamma-ray transparency of the universe. For simplicity we will henceforth just talk about axions, but axion-like particles are meant to be included. CONCLUSIONS: If axions are detected in the near future, they can provide a novel probe of the interior of our sun. We have shown that, in suitable regions of the axion parameter space, a helioscope like IAXO, equipped with sufficiently good energy resolving detectors, would allow a measurement of the strength of characteristic emission peaks in the axion spectrum. These peaks are due to the presence of heavier elements, most notably iron, neon and oxygen that are relevant to the solar abundance problem. As the peak strength is related to the elemental abundance, such a measurement could be an extremely powerful tool in resolving the solar abundance problem. Crucially, to realise this potential, an improved precision in the modelling of the atomic emission lines inside the plasma is mandatory. Turned around, such a measurement could also be used to test this modelling, e.g. by measuring different emission lines of the same
a. emission b. element c. spectrum d. plasma.
Q118. arXiv:1908.10988 [astro-ph.SR]: Spectroscopic Follow-Up of Discoveries from the NEOWISE Proper Motion Survey. Jennifer J. Greco, Adam C. Schneider, Michael C. Cushing, J. Davy Kirkpatrick, Adam J. Burgasser. (Submitted on 28 Aug 2019): ABSTRACT: We present low-resolution near-infrared spectra of discoveries from an all-sky proper motion search conducted using multi-epoch data from the Wide-field Infrared Survey Explorer. Using the data from NEOWISE, along with the AllWISE catalogue, (2016) conducted an all-sky proper motion survey to search for nearby objects with high proper motions. Here, we present a follow-up spectroscopic survey of 65 of their discoveries, which focused primarily on potentially nearby objects (d < 25 pc), candidate late-type brown dwarfs (>L7), and subdwarf candidates. We found 31 new M dwarfs, 18 new L dwarfs, and 11 new T dwarfs. Of these, 13 are sub dwarfs, including one new sdL1 and two new sdL7s. Eleven of these discoveries, with spectral types ranging from M7 to T7 (including one subdwarf) are predicted to be within 25 pc, adding to the number of known objects in the solar neighbourhood. We also discovered three new early-type T subdwarf candidates, one sdT1, one sdT2, and one sdT3, which would increase the number of known early-type T sub dwarfs from two to five. CONCLUSIONS: All three of the extreme sub dwarfs in our sample have v tan >= 250 km/s, putting them in the halo, as expected of older, lower metallicity sub dwarfs, which tend to be kinematically associated with the halo population. The dwarfs in our sample are likely clustered in the thin disk, though it is likely some are also in the thick disk. The sub dwarfs in our sample are likely distributed throughout the thick and thin disk. Three of our dwarfs have tangential velocities that place them in the halo: WISE 0101+0336 (355.0 ± 30.1 km/s), WISE 0924+0723 (290 ± 26 km/s), and WISE 1113+5010 (460 ± 76 km/s). The velocity of WISE 1113+5010 is approaching the escape velocity of the Galaxy, which is vtan=528(+24 or −25) km/s at the Sun’s
a. disk b. surface c. direction d. position.
Q119. L1330 Life Member of ISCA. Dr. Biresh Guha Street, Kolkata-700017, The Indian Science Congress Association: The 107th session: year 2020, PHYSICS SESSION TO BE HELD IN JAN. 3-7, 2020. trusciencetrutechnology@blogspot.com; EARTH CENTERED GRAVITINS IN THE INNER AND THE OUTER CORES by Prof. Dr. Kotcherlakota Lakshminarayana, trusciencetrutechnology@blogspot.com, 17-11-10, Narasimha Ashram, Official Colony, Maharanipeta. P.O., Visakhapatnam-530002, AP. Cell: 9491902867: ABSTRACT: Both the Inner and the Outer cores of the Earth are considered to have the Gravitins, a totally new concept. The Inner core, with radius 1216 km, has the Iron, Nickel, Sulphur and Magnesium with 10% other minor metals and has the mass 13000 kg/m^3 with density 0.98e+23 kg. It has about 2.277e+24 Gravitins. On the other hand, the Outer core, with a radius of 2270 km, has only smaller mass of 3000 kg/m^3 with density 1.47 kg, in a liquid state. Both the Inner and the Outer cores, have freely moving 4s^2, 4s^2, 3s^2, 3s^2 electrons and both the cores are devoid of any magnetic field. Outer core has about 3.4167e+24 Gravitins. The freely moving electrons are combined with the
a. Gravitins b. Gravitons c. Gravity d. Gravitation.
Q120. L1330 Life Member of ISCA. Dr. Biresh Guha Street, Kolkata-700017, Indian Science Congress Association, 107th Session of Indian Science Congress to be held from 3-7 January 2020 at University of Agricultural Science, Bangalore. MATHEMATICS SCIENCES (INCLUDING STATISTICS): PART OF DUST AND PHOTONS MIXED DYNAMICS OF THE UNIVERSE: Kotcherlakota_l_n : trusciencetrutechnology@blogspot.com 17-11-10, Narasimha Ashram, Official Colony, Maharanipeta. P.O., Visakhapatnam-530002, AP.Cell: 9491902867 ABSTRACT Dust and Photon events all over the Universe are scintillating. I have formulated the description of a part of Dust mixed with Photons, in the universe by several degrees of variants. From the desert land of Earth, and Earth’s environment, to the Mars, Titan and various global entities of Universe, including the Galaxies, Super stars, and the vast expanse of free space in between the galaxies, the dust and mixed Photon, occurrence is described with the help of the concomitant structures. The tiny grains, each 10,000 times smaller than the eye of a needle, absorb light, scatter it, or change its wavelength so it’s invisible to the eye. In my opinion, the Universe began with a distribution of dust and not any gas. Some Dust grains mixed with Photons, on Earth surface 0.2mm-3, Mars 0.1mm-4, while on Titan 0.01mm-5 size. Saturn rings also exhibit the dust and Photon features. Tiny grains or the Dust specks do carry the Photons, a suggestion by me, along with them and are confined in different molds. The captured Photons have a significant role and sustain with the dust rings or their manifestations. Much dust combined Photon rings, like the ones in Saturn exhibit several colors and form a marvelous lot. The mixed Dust and Photons form a scalar entity of zero spin, devoid of any formal features. I have set Dust to have a spin 1( -1,0’,+1, 0’) while the Photon has the usual spin 1(+1,0, -1, 0). The singlet 0-triplet (1,0, -1)of Photon and singlet 0’- triplet (-1, 0’, +1) of Dust Spin 1, when combined which gives a total spin 0 for the joint system, of the Dust and the Photon. [Reference 4 listed].Spin 0 Scalar Particle of joint Dust of spin 1 (-1, 0, +1, 0) and the Photon of Spin 1 (1, 0, -1, 0) is fully illustrated with all the diagram technique of Particle Physics. On the right-hand side the self-energy of the Photon is explicitly detailed out while on the left-hand side the self-energy of the Dust is illustrated. Finally, they merge and again form the Spin 0 Scalar a. Photon b. Dust c. captured d. Particle
ANSWERS: Q61b. Q62d. Q63c. Q64a. q65c. Q66d. Q67b. Q68a. Q69c. Q70a. Q71d. Q72c. Q73b. Q74d. Q75b. Q76c. Q77a. Q78c. Q79b. Q80d. Q81b. Q82d. Q83b. Q84d. Q85a. Q86c. Q87a. Q88b. Q89c. Q90b. Q91a. Q92d. Q93b. Q94a. Q95c. Q96b. Q97d. Q98a. Q99c. Q100a. Q101d. Q102b. Q103a. Q104d. Q105b. Q106d. Q107b. Q108b. Q109d. Q110d. Q111a. Q112c. Q113b. Q114d. Q115b. Q116c. Q117b. Q118d. Q119a. Q120d.
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