September 9, 2018b
Volume 2018b, Issue No.10, Dated: 9 September 2018
[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-119b
a. particle b. perturbation c. collision d. giant
Q63.arXiv:1804.01699 [astro-ph.GA]: Discovery of a vast ionized gas cloud in the M51 system. Aaron E. Watkins, J. Christopher Mihos, Matthew Bershady, Paul Harding. (Submitted on 5 Apr 2018). ABSTRACT: We present the discovery of a vast cloud of ionized gas 13′ (32 kpc) north of the interacting system M51. We detected this cloud via deep narrow-band imaging with the Burrell Schmidt Telescope, where it appears as an extended, diffuse Hα-emitting feature with no embedded compact regions. The Cloud spans ∼10′×3′ (25×7.5 kpc) in size and has no stellar counterpart; comparisons with our previous deep broadband imaging show no detected continuum light to a limit of μlim,B∼30 mag arcsec−2. WIYN SparsePak observations confirm the cloud's kinematic association with M51, and the high NII/Hα, SII/Hα, and OI/Hα line ratios we measure imply a hard ionization source such as AGN photoionization or shock heating rather than photoionization due to young stars. Given the strong NII emission, we infer roughly solar metallicity for the cloud, ruling out an origin due to infall of primordial gas. Instead we favor models where the gas has been expelled from the inner regions of the M51 system due to tidal stripping or starburst/AGN winds and has been subsequently ionized either by shocks or a fading AGN. This latter scenario raises the intriguing possibility that M51 may be the nearest example of an AGN fossil nebula or light echo, akin to the famous "Hanny's Voorwerp" in the IC 2497 system. CONCLUSIONS:To discriminate between these various scenarios for the Cloud’s origin, additional spectroscopic observations are needed which target emission lines that probe the Cloud’s density and temperature structure, better constrain its metallicity, and differentiate between photoionization and shockheating models for the Cloud. Additional information would come from mapping the line ratios and kinematics of the Cloud across its spatial extent as well. The Cloud’s size and structure—and, perhaps most importantly, the proximity of the M51 system — provide a unique opportunity to study the detailed effects of feedback and ionization on the circumgalactic environments of galaxies. The local universe contains very few known examples of extended diffuse emission sources like the Cloud; each new example provides a wealth of new information about tidal interactions, feedback processes, and the mutual interaction between galaxies and their environment. In particular, if the Cloud is a fossil nebula or echo of strong AGN activity in M51, it would be the most near by example of a rapidly fading AGN,and also represent a new and critical piece to our understanding of the iconic M51
a. system b. galaxy c. cloud d. environment
Q63.arXiv:1804.01699 [astro-ph.GA]: Discovery of a vast ionized gas cloud in the M51 system. Aaron E. Watkins, J. Christopher Mihos, Matthew Bershady, Paul Harding. (Submitted on 5 Apr 2018). ABSTRACT: We present the discovery of a vast cloud of ionized gas 13′ (32 kpc) north of the interacting system M51. We detected this cloud via deep narrow-band imaging with the Burrell Schmidt Telescope, where it appears as an extended, diffuse Hα-emitting feature with no embedded compact regions. The Cloud spans ∼10′×3′ (25×7.5 kpc) in size and has no stellar counterpart; comparisons with our previous deep broadband imaging show no detected continuum light to a limit of μlim,B∼30 mag arcsec−2. WIYN SparsePak observations confirm the cloud's kinematic association with M51, and the high NII/Hα, SII/Hα, and OI/Hα line ratios we measure imply a hard ionization source such as AGN photoionization or shock heating rather than photoionization due to young stars. Given the strong NII emission, we infer roughly solar metallicity for the cloud, ruling out an origin due to infall of primordial gas. Instead we favor models where the gas has been expelled from the inner regions of the M51 system due to tidal stripping or starburst/AGN winds and has been subsequently ionized either by shocks or a fading AGN. This latter scenario raises the intriguing possibility that M51 may be the nearest example of an AGN fossil nebula or light echo, akin to the famous "Hanny's Voorwerp" in the IC 2497 system. CONCLUSIONS:To discriminate between these various scenarios for the Cloud’s origin, additional spectroscopic observations are needed which target emission lines that probe the Cloud’s density and temperature structure, better constrain its metallicity, and differentiate between photoionization and shockheating models for the Cloud. Additional information would come from mapping the line ratios and kinematics of the Cloud across its spatial extent as well. The Cloud’s size and structure—and, perhaps most importantly, the proximity of the M51 system — provide a unique opportunity to study the detailed effects of feedback and ionization on the circumgalactic environments of galaxies. The local universe contains very few known examples of extended diffuse emission sources like the Cloud; each new example provides a wealth of new information about tidal interactions, feedback processes, and the mutual interaction between galaxies and their environment. In particular, if the Cloud is a fossil nebula or echo of strong AGN activity in M51, it would be the most near by example of a rapidly fading AGN,and also represent a new and critical piece to our understanding of the iconic M51
a. system b. galaxy c. cloud d. environment
Q64. arXiv:1804.01992 [hep-ph]: Constraining Axion-Like-Particles with Hard X-ray Emission from Magnetars. Jean-François Fortin, Kuver Sinha. (Submitted on 5 Apr 2018),ABSTRACT: Axion-like particles (ALPs) produced in the core of a magnetar will convert to photons in the magnetosphere, leading to possible signatures in the hard X-ray band. We perform a detailed calculation of the ALP-to-photon conversion probability in the magnetosphere, recasting the coupled differential equations that describe ALP-photon propagation into a form that is efficient for large scale numerical scans. We show the dependence of the conversion probability on the ALP energy, mass, ALP-photon coupling, magnetar radius, surface magnetic field, and the angle between the magnetic field and direction of propagation. Along the way, we develop an analytic formalism to perform similar calculations in more general n-state oscillation systems. Assuming ALP emission rates from the core that are just subdominant to neutrino emission, we calculate the resulting constraints on the ALP mass versus ALP-photon coupling space, taking SGR 1806-20 as an example. In particular, we take benchmark values for the magnetar radius and core temperature, and constrain the ALP parameter space by the requirement that the luminosity from ALP-to-photon conversion should not exceed the total observed luminosity from the magnetar. The resulting constraints are competitive with constraints from helioscope experiments in the relevant part of ALP parameter space. DETAILS: Magnetars constitute an interesting subclass of neutron stars characterized by extremely strong magnetic fields. Assuming that their rapid rotational spin down is caused by magnetic dipole torques, X-ray timing properties of magnetars yield field values that generally exceed the quantum critical value Bc = me^2 /e=4.414X10^13 G. In the presence of an external magnetic field, ALPs can convert into photons, and vice versa, via the Primakoff process. Can ALPs produced inside the neutron star lead to observational signatures via ALP-to-photon conversion in the magnetosphere? Conclusion: Magnetars, with their extremely strong magnetic fields, form a natural arena for investigating ALPs. Our basic idea was to consider the conversion of ALPs emitted from the core of the neutron star into photons in the magnetosphere. We assumed that the emission rate for ALPs is just subdominant to the neutrino emission rate for a given temperature. For nucleonnucleon bremsstrahlung, we obtain a broad ALP spectrum peaked around ω ∼ 3.3T. The coupled differential equations describing ALP-photon propagation in the magnetosphere were converted into a form that is efficient for extensive scans over multiple parameters. We then presented the conversion probability as a function of the ALP energy, mass, coupling g, surface magnetic field strength B0 of the magnetar, magnetar radius r0, and angle between the magnetic field and the direction of propagation θ. Along the way, we developed an analytic formalism to perform similar calculations in more general n-state oscillation systems. Taking benchmark values of the radius, magnetic field, and core temperature of SGR 1806-20, we then constrained the ALP-photon coupling by requiring that the photon flux coming from ALP conversion cannot exceed the observed luminosity of the magnetar. Our results are depicted in Fig. 5. There are several future directions that would be interesting to explore. Firstly, our approach has been to consider the photon flux from ALP-to-photon conversion for the entire energy range between ω = 1−200keV, and compare that to the broad band spectrum of the quiescent emission from SGR 1806-20 in the same range. It would be interesting to perform a bin-by-bin spectral analysis, and presumably the constraints one would obtain from such an analysis would be more stringent. Another aspect of our work that merits further study is the incorporation of other ALP production mechanisms – such as electron bremsstrahlung on the surface – and their relation to ALP-photon conversion. Finally, our analytical treatment of the ALP-photon conversion probability can be utilized in other contexts, apart from magnetar physics, for example, in extra-galactic ALP-photon
a. generation b. conversion c. degradation d. uplift.
Q65. arXiv:1804.03678 [cond-mat.mtrl-sci]: Role of intra-band transitions in photo-carrier generation. Shunsuke A. Sato, Matteo Lucchini, Mikhail Volkov, Fabian Schlaepfer, Lukas Gallmann, Ursula Keller, Angel Rubio. (Submitted on 10 Apr 2018). ABSTRACT: We theoretically investigate the role of intra-band transitions in laser-induced carrier-generation for different photon energy regimes: (i) strongly off-resonant, (ii) multi-photon resonant, and (iii) resonant conditions. Based on the analysis for the strongly off-resonant and multi-photon resonant cases, we find that intra-band transitions strongly enhance photo-carrier generation in both multi-photon absorption and tunneling excitation regimes, and thus, they are indispensable for describing the nonlinear photo-carrier generation processes. Furthermore, we find that intra-band transitions enhance photo-carrier generation even in the resonant condition, opening additional multi-photon excitation channels once the laser irradiation becomes sufficiently strong. The above findings suggest a potential for efficient control of photo-carrier generation via multi-color laser pulses through optimization of the contributions from intra-band transitions. SUMMARY: we investigated the electron-hole (e-h) pair distribution as a function of the e-h excitation energy. As a result, we found that the e-h pair distribution under a strong field shows a multi-peak structure with a plateau region (see Fig. 4). A similar feature has been found in above-threshold-ionization (ATI) photoelectron spectra of atoms. The origin of the plateau of the ATI spectra has been understood as the scattering of ionized electrons from the parent ion based on the semi-classical model [53]. Therefore, the formation of the plateau in the e-h pair distribution might also be explained by a semi-classical description. We then investigated photo-carrier generation in the three-photon resonant condition, where the mean photon-energy is identical to one third of the band gap. We found that intra-band transitions largely enhance the three-photon absorption process. To clarify the origin of the enhancement, we analytically studied the three photon absorption based on the perturbation theory. As a result, we found that intra-band transitions open additional excitation paths that generate photo-carriers much more efficiently than the pure inter-band excitation path. We note that, if intra-band transitions are induced by a static electric field, the mechanism corresponds to photo-assisted tunneling, or the so-called Franz-Keldysh effect. We then investigated the carrier-injection in the resonant condition, where the mean photon-energy of the laser field is identical to the band gap. When the field is weak enough, the carrier-injection is dominated by single photon absorption, and intra-band transitions do not play any role. In contrast, once the field becomes strong enough, intra-band transitions significantly enhance the photo-carrier generation. Based on the energy-resolved e-h distribution analysis, we clarified that the enhancement of the photo-carrier generation originates from additional multi-photon excitation paths opened by intraband transitions. Starting from the above analysis, we can conclude that intra-band transitions largely enhance the carrier injection once nonlinear effects become substantial. This finding indicates a potential to control photo-carrier injection by employing multi-color laser pulses: some of the pulses mainly induce the carrier-injection via interband transitions, while the others assist it by opening efficient excitation paths via intra-band transitions. Here, in addition to the photon-energy of each pulse, the pulse width, the relative time delay, and the relative carrier envelope phase can be optimizable parameters. An efficient enhancement or suppression of the carrier-injection by optical laser pulses will be important for technological applications such as light-driven control of material properties as well as for fundamental investigations of electron dynamics in
a. liquids b. solids c. materials d. potential
a. liquids b. solids c. materials d. potential
Q66. arXiv:1804.03751 [cond-mat.mtrl-sci]: ABSTRACT: Conversion of Heat into Charge Current by the Spin Wave Anomalous Nernst Effect. M. Mizuguchi, K. Hasegawa, J. Ohe, M. Tsujikawa, M. Shirai, K. Takanashi. (Submitted on 10 Apr 2018). Novel process of spin conversion from a temperature gradient to a transverse voltage is addressed in this paper, viz. the anomalous Nernst effect (ANE) in a ferromagnetic metal. We report that an additional voltage is superposed on the conventional anomalous Nernst voltage in FePt crystalline thin films. The dynamics of the local magnetization is modulated by the heat current and excites spin waves. These generate a conduction electron spin current via s-d coupling, which flows along the temperature gradient, and the spin current is converted to a Nernst voltage by the inverse spin Hall effect. SUMMARY: The ANE signal increases with temperature and the contribution of the conduction electron spin current saturates over 100 K. From this simulation, we conclude that the magnetic order is excited significantly only over 100 K for this FePt which agrees with the α xy enhancement beyond the Mott relation. It can be considered that this spin wave excitation by the temperature gradient converted to the pure conduction electron spin current and eventually enhanced the ANE in FePt. This novel process is expected to pave a new way for renewed energy conversion systems which will serve a useful energy sources in our daily life. The expectations of realization of ANE-based thermoelectric devices strongly rise by employing this novel spin conversion
a. gradient b. uplift c. strategy d. process.
a. gradient b. uplift c. strategy d. process.
Q67.arXiv:1804.03950 [cond-mat.mtrl-sci]: Electron-plasmon and electron-phonon satellites in the angle-resolved photoelectron spectra of n-doped anatase TiO2. Fabio Caruso, Carla Verdi, Samuel Poncé, Feliciano Giustino. (Submitted on 11 Apr 2018). ABSTRACT: We develop a first-principles approach based on many-body perturbation theory to investigate the effects of the interaction between electrons and carrier plasmons on the electronic properties of highly-doped semiconductors and oxides. Through the evaluation of the electron self-energy, we account simultaneously for electron-plasmon and electron-phonon coupling in theoretical calculations of angle-resolved photoemission spectra, electron linewidths, and relaxation times. We apply this methodology to electron-doped anatase TiO2 as an illustrative example. The simulated spectra indicate that electron-plasmon coupling in TiO2 underpins the formation of satellites at energies comparable to those of polaronic spectral features. At variance with phonons, however, the energy of plasmons and their spectral fingerprints depends strongly on the carrier concentration, revealing a complex interplay between plasmon and phonon satellites. The electron-plasmon interaction accounts for approximately 40% of the total electron-boson interaction strength and it is key to improve the agreement with measured quasiparticle spectra. Phys. Rev. B 97, 165113 (2018). SUMMARY: In n-type (p-type) doped semiconductors, the extrinsic carriers injected in the conduction (valence) band through the dopant atoms may host carrier plasmons, that is, low-energy plasmons with characteristic energies set by the carrier concentration n via ωpl = (4πn/mb \epsilon∞)^1/2 , with mb and \epsilon∞ being the band effective mass and the high-frequency dielectric constant, respectively. Hartree atomic units are used throughout. At variance with metals and undoped semiconductors, where the plasmon energy is of the order of 5-15 eV, for degenerate doping densities (10^17-10^19 cm^−3), the characteristic energy of carrier plasmons is typically smaller than 100 meV and it is thus comparable with the phonon energies of solids. At these energy scales, plasmons influence pervasively the electronic properties of doped semiconductors. CONCLUSIONS: In conclusion, these results suggest that the interplay of electrons, plasmons, and phonons underpin a complex scenario of many-body interaction in TiO2, whereby the simultaneous coupling to different bosonic modes depends pronouncedly on the concentration of extrinsic carriers and influences pervasively photoemission satellites, linewidths, and quasiparticle weights. These aspects emphasize the importance of explicitly accounting for the effects of both phonons and plasmons in future studies of highly-doped semiconductors and oxides. Accounting for these phenomena through first-principles approaches may provide a valuable tool to unravel the fundamental quantum-mechanical processes that underpin the formation of satellites in photoemission spectroscopy and the relaxation of excited
a. weights b. linewidths c. carriers d. results.
a. weights b. linewidths c. carriers d. results.
Q68. arXiv:1804.03902 [gr-qc]: Novel matter coupling in general relativity via canonical transformation. Katsuki Aoki, Chunshan Lin, Shinji Mukohyama. (Submitted on 11 Apr 2018). ABSTRACT: We study canonical transformations of general relativity (GR) to provide a novel matter coupling to gravity. Although the transformed theory is equivalent to GR in vacuum, the equivalence no longer holds if a matter field minimally couples to the canonically transformed gravitational field. We find that a naive matter coupling to the transformed field leads to the appearance of an extra mode in the phase space, rendering the theory inconsistent. We then find a consistent and novel way of matter coupling: after imposing a gauge fixing condition, a matter field can minimally couple to gravity without generating an unwanted extra mode. As a result, the way matter field couples to the gravitational field determines the preferred time direction and the resultant theory has only two gravitational degrees of freedom. We also discuss the cosmological solution and linear perturbations around it, and confirm that their dynamics indeed differ from those in GR. The novel matter coupling can be used for a new framework of modified gravity theories. SUMMARY: In the present paper, we have investigated canonical transformations of general relativity (GR) to generate “new” theories of gravity. We first confirmed that a canonical transformation does not change the constraint algebra of the theory and thus the transformed theory has only two gravitational degrees of freedom. We then discussed the matter coupling and found a novel and consistent way of the coupling although a naive coupling leads to an inconsistent result. The matter field is introduced as follows: We first introduce the gauge fixing condition G ≈0 before introducing the matter field in order to reduce one first class constraint H0 ≈ 0 to two second class constraints H0 ≈ 0, G ≈ 0 and then we introduce the matter field. As a result, the matter field fixes the preferred time direction as well as the preferred frame of the phase space. Besides the construction of the theory, we have discussed the cosmological dynamics and the linear perturbations. The canonical transformation generically changes the speed of the gravitational waves. Hence, the canonical transformation should reduce to a trivial transformation in the late-time universe since the speed of the gravitational waves has to be the same as the speed of light with a high degree of accuracy 10^−15 at the present universe. On the other hand, there is no model-independent constraint on the speed of gravitational waves in the early universe. We have thus given an example of the theory representing the ultraviolet modification of gravity which yields a non-singular universe where the universe starts from the Minkowski spacetime. Although we have considered a simple generating functional of the canonical transformation, one can consider more general canonical transformations. For instance, one may introduce the dependence of f on πikπjlγijγkl/detγ. Many new and yet unexplored theories of gravity can be generated from known theories via canonical transformations. Our procedure to introduce the matter field in a consistent way can be applied to the minimally modified theories of gravity. As pointed out in earlier, the matter coupling in the minimally modified theories of gravity is a nontrivial task. If a theory has a first class constraint, one may a priori introduce a gauge fixing condition just in the same way as in the present case. Then, the matter field can be consistently introduced. In summary, the present paper provides new gravitational theories with two physical degrees of freedom via the canonical transformation followed by a novel matter coupling. Since we now have a new matter coupling, it would be interesting to investigate observational consequences. For example, the theories obtained by the canonical transformation must admit black hole solutions since the theory is equivalent to GR in vacuum. However, it is nontrivial how the black hole is formed and observed in such theories because the matter propagates on the frame that is related to the original Einstein frame by a non-trivial canonical
a. transformation b. coupling c. gauge d. degrees of freedom.
a. transformation b. coupling c. gauge d. degrees of freedom.
Q69.arXiv:1804.04764 [cond-mat.mes-hall]; A fast quantum interface between spin qubits of different codes. A. Noiri, T. Nakajima, J. Yoneda, M. R. Delbecq, P. Stano, T. Otsuka, K. Takeda, S. Amaha, G. Allison, K. Kawasaki, A. Ludwig, A. D. Wieck, D. Loss, S. Tarucha. (Submitted on 13 Apr 2018); ABSTRACT: Single-spin qubits in semiconductor quantum dots proposed by Loss and DiVincenzo (LD qubits) hold promise for universal quantum computation with demonstrations of a high single-qubit gate fidelity above 99.9 % and two-qubit gates in conjunction with a long coherence time. However, initialization and readout of a qubit is orders of magnitude slower than control, which is detrimental for implementing measurement-based protocols such as error-correcting codes. In contrast, a singlet-triplet (ST) qubit, encoded in a two-spin subspace, has the virtue of fast readout with high fidelity and tunable coupling to the electric field. Here, we present a hybrid system which benefits from the different advantages of these two distinct spin-qubit implementations. A quantum interface between the two codes is realized by electrically tunable inter-qubit exchange coupling. We demonstrate a controlled-phase (CPHASE) gate that acts within 5.5 ns, much faster than the measured dephasing time of 211 ns. The presented hybrid architecture will be useful to settle remaining key problems with building scalable spin-based quantum computers. In summary, we have realized a fast quantum interface between a LD qubit and a ST qubit using a TQD. The CPHASE gate between these qubits is performed in 5.5 ns, much faster than its dephasing time of 211 ns and those ratio (∼38) would be high enough to provide a high fidelity CPHASE gate (Supplementary Material Sec. 7). Optimizing the magnet design to enhance the field gradient would allow even faster gate time beyond GHz with larger 𝐽QQ. At the same time, this technique is directly applicable to Si-based devices with much better single-qubit coherence5-9. Based on our results, we envisage coupling two ST qubits through an intermediate LD qubit, which would boost the two ST qubit gate speed by orders of magnitude compared to the capacitive coupling scheme16. Viewed from the opposite side, the fast (~ 100 ns25) ST qubit readout will allow the read out of a LD qubit in a quantum-non-demolition manner30 with a speed three orders of magnitude faster than a typical energy selective tunneling measurement3,4. Our approach will further push the demonstrated scalabitlity of spin qubits in quantum dot arrays beyond the conventional framework based on a unique spin-qubit
a. coding b. coherence c. tunnelling d. encoding
Q70. arXiv:1804.04871 [cond-mat.quant-gas];Spin-resolved single-atom imaging of 6Li in free space; Andrea Bergschneider, Vincent M. Klinkhamer, Jan Hendrik Becher, Ralf Klemt, Gerhard Zürn, Philipp M. Preiss, Selim Jochim. (Submitted on 13 Apr 2018) :ABSTRACT: We present a versatile imaging scheme for fermionic 6 Li-atoms with single-particle sensitivity. Our method works for freely propagating particles and completely eliminates the need for confining potentials during the imaging process. We illuminate individual atoms in free space with resonant light and collect their fluorescence on an electron-multiplying CCD camera using a high-NA imaging system. We detect approximately 20 photons per atom during an exposure of 20μs and identify individual atoms with a fidelity of (99.4±0.3) % . By addressing different optical transitions during two exposures in rapid succession, we additionally resolve the hyperfine spin state of each particle. The position uncertainty of the imaging scheme is 4.0μm, given by the diffusive motion of the particles during the imaging pulse. The absence of confining potentials enables new readout procedures, as an example of which we demonstrate the measurement of single-particle momenta in time-of-flight. DETAILS: Our imaging scheme is technically simple and easily adapted to other atomic species. Our detection scheme is based on fluorescence imaging of freely propagating fermionic 6Li atoms. We drive the D2-transition with resonant light at 671nm for a few hundred cycles and collect part of the scattered photons with an objective with a large numerical aperture. The collected photons are imaged onto a single-photon sensitive camera, where we can distinguish them from camera noise to identify single atoms. SUMMARY AND OUTLOOK: We have presented a new imaging method to characterize few-particle quantum states of 6Li on a single-particle level with spin and position resolution. We have demonstrated single-atom imaging by collecting about 20 fluorescence photons per atom on a single-photon sensitive camera. With this method we achieve a detection fidelity of up to (99.4±0.3)% and a position determination with an uncertainty of (4.0±0.4)µm. Our imaging technique has been applied to freely propagating atoms also after a coherent expansion in time-of-flight. We demonstrate the detection of momentum distribution on the single-atom level by an expansion in a waveguide trap. In the future, we will apply the free-space imaging also to systems containing more atoms and after more complex manipulations of the system. For example, a sequence of coherent expansions in different harmonic potentials could be used to magnify the quantum state in position space. In that way, we could access the in-situ distribution of atoms in multiple optical tweezers with single-atom sensitivity. This opens a path to studying correlation functions of complex quantum systems in two conjugate bases, real space and momentum
a. deviation b. sensitivity c. space d. volume
Q71.arXiv:1804.04920 [cond-mat.mtrl-sci]. Aggregation and Electronically-Induced Migration of Oxygen Vacancies in TiO2 Anatase. Martin Setvin, Michael Schmid, Ulrike Diebold. (Submitted on 13 Apr 2018): ANSTRACT: The influence of the electric field and electric current on the behavior of oxygen vacancies (VOs) in TiO2 anatase was investigated with Scanning Tunneling Microscopy (STM). At the anatase (101) surface VOs are not stable; they migrate into the bulk at temperatures above 200 K. Scanning a clean anatase (101) surface at a sample bias greater than +4.3 V results in surface VOs in the scanned area, suggesting that subsurface VOs migrate back to the surface. To test this hypothesis, surface VOs were first created through bombardment with energetic electrons. The sample was then mildly annealed, which caused the VOs to move to the subsurface region, where they formed vacancy clusters. These VO clusters have various, distinct shapes. Scanning VO clusters with a high STM bias reproducibly converts them back into groupings of surface VO, with a configuration that is characteristic for each type of cluster. The dependence of the subsurface-to-surface VO migration on the applied STM bias voltage, tunnelling current, and sample temperature was investigated systematically. The results point towards a key role of energetic, 'hot' electrons in this process. The findings are closely related to the memristive behaviour of oxides and oxygen diffusion in solid-oxide membranes. INTRODUCTION: The influence of electric fields on the behaviour of oxygen vacancies (VOs) in metal oxides is of key importance for several applications of these materials. For example, the memristive switching in oxides is a promising approach for data storing. While it is clear that field induced redox reactions and field-induced material migration play a key role, very little is known about the detailed physical mechanisms and processes occurring at atomic scale. Similar phenomena are also essential in solid-oxide fuel cells, where oxygen is transported from the cathode to the anode through the lattice of the oxide electrolyte (typically ZrO2 or CeO2) via migration of oxygen vacancies. CONCLUSIONS: We have shown that scanning the anatase (101) surface at high positive sample bias results in the appearance of surface VOs in the scanned area. We attribute this effect to a migration of VOs from the subsurface region to the surface. The process is self-limiting: presence of VOs on the surface prevents further subsurface-to-surface VO migration. Analysis of the experimental data indicates that the electric field penetrating into the sample is an important factor for reverting the energy balance between the surface and subsurface VOs. The hot electrons injected from the tip provide the activation energy necessary for the VO migration through the lattice. It was further shown that VOs can easily form subsurface clusters upon annealing. We identified VO clusters that contain two to five vacancies. Likely this is the initial step in the formation of extended defects and reduced TiO2−x phases. Subsurface aggregates of VOs can be converted back into single surface VOs by applying a suitable electric field. This process closely resembles memristive switching: Two distinct states exist, one that is reached upon thermal annealing and another one by applying a high electric field. The memristive behaviour of oxides have been investigated for more than 50 years, yet there is essentially no knowledge about processes occurring at atomic scale. Our results could provide a significant step forward to identifying the underlying physical
a. mechanisms b. order c. behaviour d. switching.
Q72. arXiv:1804.07471 [hep-ph]: Production of Purely Gravitational Dark Matter, Yohei Ema, Kazunori Nakayama, Yong Tang, (Submitted on 20 Apr 2018): ABSTRACT: n the purely gravitational dark matter scenario, the dark matter particle does not have any interaction except for gravitational one. We study the gravitational particle production of dark matter particle in such a minimal setup and show that correct amount of dark matter can be produced depending on the inflation model and the dark matter mass. In particular, we carefully evaluate the particle production rate from the transition epoch to the inflation oscillation epoch in a realistic inflation model and point out that the gravitational particle production is efficient even if dark matter mass is much larger than the Hubble scale during inflation as long as it is smaller than the inflation mass. We revisit the gravitational particle production in a realistic situation. It is often misunderstood that the gravitational particle production is not efficient if mχ >> Hinf. It is not always true, however. In many inflation models, there is a large hierarchy between the inflation mass scale and Hubble scale: mφ >> Hinf. Gravitational particle production is efficient even for mφ > mχ >> Hinf. This point is not stressed in literature except for a few works. Therefore we want to study the gravitational production in a comprehensive manner. We studied the gravitational production of scalar PGDM by tracing the evolution of its wave function from inflation to the reheating era. we note that our results depend on the assumption that the inflation field remains homogeneous over the horizon scale until the inflation coherent oscillation becomes purely harmonic. In actual situation, there can be some instability that tend to make the inflation field inhomogeneous. Although our results may not be affected much unless the inflation field becomes highly relativistic, further investigation is needed in order to correctly estimate the PGDM abundance in various inflation
a. data b. models c. works d. thoughts.
Q73. arXiv:1804.08402 [astro-ph.HE]: The geometric distance and binary orbit of PSR B1259-63: James C. A. Miller-Jones, Adam T. Deller , Ryan M. Shannon, Richard Dodson, Javier Moldón, Marc Ribó, Guillaume Dubus, Simon Johnston, Josep M. Paredes, Scott M. Ransom, John A. Tomsick (Submitted on 23 Apr 2018): ABSTRACT: The pulsar/massive star binary system PSR B1259-63 / LS 2883 is one of the best-studied gamma-ray binaries, a class of systems whose bright gamma-ray flaring can provide important insights into high-energy physics. Using the Australian Long Baseline Array we have conducted very long baseline interferometric observations of PSR B1259-63 over 4.4 years, fully sampling the 3.4-year orbital period. Inverting our measured parallax gives a distance of 2.59 + 0.37 −0.28 kpc, which when modified to account for the Lutz-Kelker bias gives a corrected distance of 2.70(+0.41 or −0.31)kpc. We find that the binary orbit is viewed at an angle of 153.4 (+3.2 or −3.0) degrees to the line of sight, implying that the pulsar moves clockwise around its orbit as viewed on the sky. Taking our findings together with previous results from pulsar timing observations, all seven orbital elements for the system are now fully determined. We use our measurement of the inclination angle to constrain the mass of the stellar companion to lie in the range 14.2-29.8⊙ Our measured distance and proper motion are consistent with the system having originated in the Cen OB1 association and receiving a modest natal kick, causing it to have moved ∼ 8 pc from its birthplace over the past ∼3× 10^5years. The orientation of the orbit on the plane of the sky matches the direction of motion of the X-ray synchrotron-emitting knot observed by the Chandra X-ray Observatory to be moving away from the system. SUMMARY: The pulsar rotates clockwise around its orbit, and the orientation of that orbit on the plane of the sky is consistent with the extended X-ray emission moving away in the direction of apastron. Our measured proper motion implies a space velocity of 38±9kms^-1 relative to Cen OB1, and is consistent with the system having been formed in that association and receiving a natal kick on the formation of the neutron
a. magnitude b. quark c. star d. pulsar
a. data b. models c. works d. thoughts.
Q73. arXiv:1804.08402 [astro-ph.HE]: The geometric distance and binary orbit of PSR B1259-63: James C. A. Miller-Jones, Adam T. Deller , Ryan M. Shannon, Richard Dodson, Javier Moldón, Marc Ribó, Guillaume Dubus, Simon Johnston, Josep M. Paredes, Scott M. Ransom, John A. Tomsick (Submitted on 23 Apr 2018): ABSTRACT: The pulsar/massive star binary system PSR B1259-63 / LS 2883 is one of the best-studied gamma-ray binaries, a class of systems whose bright gamma-ray flaring can provide important insights into high-energy physics. Using the Australian Long Baseline Array we have conducted very long baseline interferometric observations of PSR B1259-63 over 4.4 years, fully sampling the 3.4-year orbital period. Inverting our measured parallax gives a distance of 2.59 + 0.37 −0.28 kpc, which when modified to account for the Lutz-Kelker bias gives a corrected distance of 2.70(+0.41 or −0.31)kpc. We find that the binary orbit is viewed at an angle of 153.4 (+3.2 or −3.0) degrees to the line of sight, implying that the pulsar moves clockwise around its orbit as viewed on the sky. Taking our findings together with previous results from pulsar timing observations, all seven orbital elements for the system are now fully determined. We use our measurement of the inclination angle to constrain the mass of the stellar companion to lie in the range 14.2-29.8⊙ Our measured distance and proper motion are consistent with the system having originated in the Cen OB1 association and receiving a modest natal kick, causing it to have moved ∼ 8 pc from its birthplace over the past ∼3× 10^5years. The orientation of the orbit on the plane of the sky matches the direction of motion of the X-ray synchrotron-emitting knot observed by the Chandra X-ray Observatory to be moving away from the system. SUMMARY: The pulsar rotates clockwise around its orbit, and the orientation of that orbit on the plane of the sky is consistent with the extended X-ray emission moving away in the direction of apastron. Our measured proper motion implies a space velocity of 38±9kms^-1 relative to Cen OB1, and is consistent with the system having been formed in that association and receiving a natal kick on the formation of the neutron
a. magnitude b. quark c. star d. pulsar
Q74. arXiv:1804.06298 [gr-qc]: Photon-graviton scattering: a new way to detect anisotropic gravitational waves?icola Bartolo, Ahmad Hoseinpour, Giorgio Orlando, Sabino Matarrese, Moslem Zarei(Submitted on 17 Apr 2018):ABSTRACT: Gravitons are the quantum counterparts of gravitational waves in low-energy theories of gravity. Using Feynman rules one can compute scattering amplitudes describing the interaction between gravitons and other fields. Here, we consider the interaction between gravitons and photons. Using the quantum Boltzmann equation formalism, we derive fully general equations describing the radiation transfer of photon polarization, due to the forward scattering with gravitons. We show that the Q and U photon linear polarization modes couple with the V photon circular polarization mode, if gravitons have anisotropies in their power-spectrum statistics. As an example, we apply our results to the case of primordial gravitons, considering models of inflation where an anisotropic primordial graviton distribution is produced. Finally, we evaluate the effect on Cosmic Microwave Background (CMB) polarization, showing that in general the expected effects on the observable CMB frequencies are very small. However, our result is promising, since it could provide a novel tool for detecting anisotropic backgrounds of gravitational waves, as well as for getting further insight on the physics of gravitational waves. SUMMARY: it is straightforward to verify that the source terms appearing in the right-hand sides all identically vanish when photons interact with gravitons that are characterised by a statistically isotropic power-spectrum. Thus, to achieve a non-trivial result, we need the photon to interact with an anisotropic background of gravitons. In the latter case, Q and U photon polarization states couple with the V polarization state, while the I unpolarized state remains unchanged. Notice that this result can be applied in full generality to the interactions involving gravitons and photons of whatever origin. In the next section we will give some examples applying our results to study the effect on the photon polarization due to the forward scattering with primordial gravitons generated during
a. refraction. b. inflation c. waves generation d. their origin.
Q75. International Letters of Chemistry, Physics and Astronomy Submitted:2017-12-15 ISSN: 2299-3843, Vol. 78, pp 39-50 Revised:2018-03-11: Accepted:2018-03-30 © 2018 SciPress Ltd., Switzerland The gravitational field in the relativistic uniform model within the framework of the covariant theory of gravitation. Sergey G. Fedosin. ABSTRACT: For the relativistic uniform system with an invariant mass density the exact expressions are determined for the potentials and strengths of the gravitational field, the energy of particles and fields. It is shown that, as in the classical case for bodies with a constant mass density, in the system with a zero vector potential of the gravitational field, the energy of the particles, associated with the scalar field potential, is twice as large in the absolute value as the energy defined by the tensor invariant of the gravitational field. The problem of inaccuracy of the use of the field’s stress-energy tensors for calculating the system’s mass and energy is considered. The found expressions for the gravitational field strengths inside and outside the system allow us to explain the occurrence of the large-scale structure of the observable Universe, and also to relate the energy density of gravitons in the vacuum field with the limiting mass density inside the proton. Both the Universe and the proton turn out to be relativistic uniform systems with the maximum possible parameters. The described approach allows us to calculate the maximum possible Lorentz factor of the matter particles at the center of the neutron star and at the center of the proton, and also to estimate the radius of action of the strong and ordinary gravitation in cosmological space. SUMMARY:The metric near the solitary massive body was determined, with the help of which it was shown that the covariant theory of gravitation successfully explains the anomalous precession of Mercury's perihelion, the deviation of particles and light in the gravitational field, the gravitational time delay and the gravitational redshift of light, as well as the Pioneer anomaly. As a uniform relativistic system the spherical system is considered, which consists of the particles that can also have the electrical charge. The stability of the system is maintained by the action of its proper gravitation, the internal pressure field and the acceleration field of the particles [17, 18]. CONCLUSIONS: The Neutron Star In the previous section the estimate of the Lorentz factor at the center of the proton was obtained: γc ≈ 1.9 Similarly, it is possible to calculate the Lorentz factor for the particles at the center of a typical neutron star with the mass of 1.35 Solar masses, the radius of Rs = 12km, and the average density of ρs = 3.7 x 10^17kg/m^3. For the star we need to take into account the ratio η ≈ 3/5 G and the angle of δs = Rs/c * sqrt(4*pi*η*ρs) ≈ 0.546 radians. Substituting now in (4) i.e., mb= m* γc * {1- 3*η*m/(10*a*c^2)} the star mass instead of mb , δs instead of a/c*sqrt(4*pi*η*ρs) , γcs instead of γc , and replacing 'a' by the star radius Rs , we find γ cs ≈ 1.04. This allows us to calculate the kinetic energy Es= (γcs - 1)mp c^2 of the proton as a certain typical particle, moving at the center of the neutron star, and to estimate the temperature at the center of the star: T= 2.8x10^11K using the equation Es=3/2*kT, where k is the Boltzmann constant and mp is the
a. neutron mass b. average density c. Redshift d. proton mass
a. refraction. b. inflation c. waves generation d. their origin.
Q75. International Letters of Chemistry, Physics and Astronomy Submitted:2017-12-15 ISSN: 2299-3843, Vol. 78, pp 39-50 Revised:2018-03-11: Accepted:2018-03-30 © 2018 SciPress Ltd., Switzerland The gravitational field in the relativistic uniform model within the framework of the covariant theory of gravitation. Sergey G. Fedosin. ABSTRACT: For the relativistic uniform system with an invariant mass density the exact expressions are determined for the potentials and strengths of the gravitational field, the energy of particles and fields. It is shown that, as in the classical case for bodies with a constant mass density, in the system with a zero vector potential of the gravitational field, the energy of the particles, associated with the scalar field potential, is twice as large in the absolute value as the energy defined by the tensor invariant of the gravitational field. The problem of inaccuracy of the use of the field’s stress-energy tensors for calculating the system’s mass and energy is considered. The found expressions for the gravitational field strengths inside and outside the system allow us to explain the occurrence of the large-scale structure of the observable Universe, and also to relate the energy density of gravitons in the vacuum field with the limiting mass density inside the proton. Both the Universe and the proton turn out to be relativistic uniform systems with the maximum possible parameters. The described approach allows us to calculate the maximum possible Lorentz factor of the matter particles at the center of the neutron star and at the center of the proton, and also to estimate the radius of action of the strong and ordinary gravitation in cosmological space. SUMMARY:The metric near the solitary massive body was determined, with the help of which it was shown that the covariant theory of gravitation successfully explains the anomalous precession of Mercury's perihelion, the deviation of particles and light in the gravitational field, the gravitational time delay and the gravitational redshift of light, as well as the Pioneer anomaly. As a uniform relativistic system the spherical system is considered, which consists of the particles that can also have the electrical charge. The stability of the system is maintained by the action of its proper gravitation, the internal pressure field and the acceleration field of the particles [17, 18]. CONCLUSIONS: The Neutron Star In the previous section the estimate of the Lorentz factor at the center of the proton was obtained: γc ≈ 1.9 Similarly, it is possible to calculate the Lorentz factor for the particles at the center of a typical neutron star with the mass of 1.35 Solar masses, the radius of Rs = 12km, and the average density of ρs = 3.7 x 10^17kg/m^3. For the star we need to take into account the ratio η ≈ 3/5 G and the angle of δs = Rs/c * sqrt(4*pi*η*ρs) ≈ 0.546 radians. Substituting now in (4) i.e., mb= m* γc * {1- 3*η*m/(10*a*c^2)} the star mass instead of mb , δs instead of a/c*sqrt(4*pi*η*ρs) , γcs instead of γc , and replacing 'a' by the star radius Rs , we find γ cs ≈ 1.04. This allows us to calculate the kinetic energy Es= (γcs - 1)mp c^2 of the proton as a certain typical particle, moving at the center of the neutron star, and to estimate the temperature at the center of the star: T= 2.8x10^11K using the equation Es=3/2*kT, where k is the Boltzmann constant and mp is the
a. neutron mass b. average density c. Redshift d. proton mass
Q76. arXiv:1805.00927 [gr-qc]: Transferring Energy in General Relativity. Rituparno Goswami, George F. R. Ellis. (Submitted on 2 May 2018). ABSTRACT: A problem in general relativity is, how the gravitational field can transfer energy and momentum between different distant places. The issue is that matter stress tensor is locally conserved, with no explicit interaction with the free gravitational field, which is represented by the Weyl tensor. In this paper we explicitly construct an interaction tensor for free gravity and matter, that depicts the interplay between the energy momentum tensor of free gravity, which is taken to be the symmetric two index square root of Bell-Robinson tensor, and matter. This is examined both in the case of Coulomb-like Petrov type D spacetimes and radiation like Petrov type N spacetimes, where a unique square root exists. The first case generalises the Tweedledum and Tweedledee thought experiment regarding gravitational induction in Newtonian gravity to general relativistic scenarios, and the second gives a proposal for how gravitational radiation can transfer energy and momentum between distant objects separated by a vacuum. DETAILS:Of course, in general relativity, gravity can transfer energy via two mechanisms: Firstly by gravitational induction, which is similar to the Newtonian case, governed by the electric part of the Weyl tensor Eab = Cacbd ucud where ua is the timelike normalised 4-velocity of the fluid; the magnetic part Hab of the Weyl tensor plays no role. This is for example the way the Moon causes tides on Earth. The second mechanism is gravitational radiation (which has no counterpart in Newtonian gravity), that isallowed by the magnetic part of the Weyl tensor Hab = 1/2 Qade Cdebc uc where Qabc = ηabcd ud is the volume element of the spacelike 3-space perpendicular to
a. Qabc b. ua. c. weyl tensor d. vacuum.
Q77. arXiv:1804.00070 [gr-qc]: Value of the Cosmological Constant in Emergent Quantum Gravity. Craig Hogan. (Submitted on 30 Mar 2018). ABSTRACT: It is suggested that the exact value of the cosmological constant could be derived from first principles, based on entanglement of the Standard Model field vacuum with emergent holographic quantum geometry. For the observed value of the cosmological constant, geometrical information is shown to agree closely with the spatial information density of the QCD vacuum, estimated in a free-field approximation. The comparison is motivated by a model of exotic rotational fluctuations in the inertial frame that can be precisely tested in laboratory experiments. Cosmic acceleration in this model is always positive, but fluctuates with characteristic coherence length≈100km and bandwidth≈3000Hz. DETAILS:The cosmological constant Λ was introduced by Einstein just over a century ago into the fundamental equations of general relativity. Its physical effect is to accelerate the expansion of empty space: in the absence of any form of gravitating matter, two test particles at separation r accelerate apart at a rate sqrt(¨r/r) = sqrt(Λ/3) ≡ HΛ. CONCLUSIONS: The cosmic acceleration is not actually constant, but fluctuates in a new way: the entanglement of emergent quantum geometry with QCD “shakes the universe apart”. The radial cosmic acceleration can be visualized as a centrifugal effect of the exotic rotational fluctuations of the inertial frame, as they “drag” the field vacuum. The rotational fluctuations create a kinematical mean square centrifugal
a. velocity b. momentum c. acceleration. d. force
Q78. arXiv:1804.00594 [gr-qc]: Spontaneous growth of spinor fields in gravity. Fethi M Ramazanoğlu. (Submitted on 2 Apr 2018): ABSTRACT: We show that spinor fields nonminimally coupled to gravity can grow spontaneously in the presence of matter. We name this phenomenon spontaneous spinorization after the spontaneous scalarization scenario in scalar-tensor theories. Underlying reason for the growth of the spinor is an instability similar to the tachyon of spontaneous scalarization. We first present the structure of a tachyonic Dirac equation, and incorporate it into the matter coupling in gravity. This causes the zero-spinor solution to be unstable and leads to spontaneous growth. We investigate the behaviour of the resulting theory for a spherically symmetric neutron star that has grown a spinor cloud. Spontaneous spinorization has the potential to lead to order-of-unity deviations from general relativity in strong fields in a similar manner to its close relative spontaneous scalarization. This makes the theory especially relevant to gravitational wave science and neutron star astrophysics. DETAILS: We constructed a theory of spontaneously growing spinors inspired by spontaneous scalarization and the general framework of regularized instabilities. Despite differences between their mathematical structures, the usual recipe for scalars and vectors also works on spinors, leading to spontaneous spinorization. Mathematical details are more laborious, and a pure tachyonic spinor is quite different from a tachyonic tensor, but the essence of the spontaneous spinorization mechanism is still an instability, showing their universal power beyond tensor fields. We also investigated the spinorization of a non-rotating NS as an important astrophysical example, and showed that this phenomena is qualitatively quite similar to ghost-based spontaneous scalarization. For example, if spinorized NSs are stable, which we think is the likely case, they necessarily have a cusp-like structure in their density profiles which probably leads to strong observable signals. Hence, we expect the βψ−m parameter space of spontaneous spinorization to be quickly restrained by NS observations which are increasing in number. Gravitational wave signals from mergers of spinorized NSs are likely to provide clear differences from those in GR. Moreover, radical differences in star structure might even be observable for isolated stars or stars in binaries far from mergers. We have seen that the lack of a scaling symmetry in spontaneously spinorizing NSs necessitates to interpret our spinors as classical objects, possibly aside from some inconsequential solutions which accidentally have unit occupation. However, a scaling is more natural for exotic objects such as boson stars. If a boson star is spontaneously spinorized, it is possible to scale the whole system to make the occupation number of each spinor exactly 1, and interpret the spinor cloud as a fermion at least in some effective sense. However, when the occupation number of the spinor is 1, the mass of the spinor cloud is within the order of magnitude of the mass of the spinor m, hence such objects might be more aptly considered as particles rather than stars. Such systems where bosons and fermions are naturally associated might be interesting from the point of view of particle physics. Spinors are essential in describing the universe and its contents. In this work, we have shown that spontaneous growth ideas can be generalized to spinor fields. This demonstrates the universal power of regularized instabilities to cause spontaneous growth in the whole spectrum of field theories, and specifically beyond tensors. Our future work will concentrate on establishing the relevance of spontaneous spinorization and other spontaneously growing fields to astrophysical
a. observations b. findings c. spinorization d. views
Q79. arXiv:1802.00058 [gr-qc]: Redshift and lateshift from homogeneous and isotropic modified dispersion relations. Christian Pfeifer. (Submitted on 31 Jan 2018 (v1), last revised 14 Mar 2018 (this version, v3)): ABSTRACT: Observables which would indicate a modified vacuum dispersion relations, possibly caused by quantum gravity effects, are a four momentum dependence of the cosmological redshift and the existence of a so called lateshift effect for massless or very light particles. Existence or non-existence of the later is currently analyzed on the basis of the available observational data from gamma ray bursts and compared to predictions of specific modified dispersion relation models. We consider the most general perturbation of the general relativistic dispersion relation of freely falling particles on homogeneous and isotropic spacetimes and derive the red- and lateshift to first order in the perturbation. Our result generalizes the existing formulae in the literature and we find that there exist modified dispersion relations causing both, one or none of the two effects to first order. DETALS: One most prominent signature would be a so called lateshift observation, i.e. an advance or a delay in the expected time of arrival of high energetic photons and neutrinos from the same source compared to low energetic ones emitted at the same time. Recently a preliminary analysis of the ICECUBE data for such a lateshift has been performed, as well as an analysis of GRBs detected with the Fermi Gamma-Ray Space Telescope. Conclusion: Starting from a general first order perturbation of the general relativistic homogeneous and isotropic dispersion relation of freely falling point particles (10) we derived the observables redshift (15) and lateshift (20). Compared to general relativity the redshift generically becomes energy dependent and the lateshift for simultaneously emitted photons emerges. With help of the new general first order formulae obtained here it was possible to demonstrate that there exist particular MDRs in which only one or none of the effects appear. Observation or non-observations of a four momentum dependent redshift or lateshift of particles from the same source emitted at the same time now directly leads to bounds, which the first order perturbation of the dispersion relation must satisfy. The interpretation of a lateshift observation must however be done with care due to uncertainties in the simultaneity of the emission time of the particles. To identify the effects coming from a quantum gravity induced MDR it is necessary to take such emission delays into
a. bounds b. lateshifts c. account d. observation
Q80.An uncertainty principle for star formation–II. A new method for characterising the cloud-scale physics of star formation and feed back across cosmic history. J. M. Diederik Kruijssen, Andreas Schruba,4 Alexander P. S. Hygate, Chia-Yu Hu, Daniel T. Haydon and Steven N. Longmore, Accepted 2018 April 27. Received 2018 April 23; in original form 2017 October 5.ABSTRACT The cloud-scale physics of star formation and feedback represent the main uncertainty in galaxy formation studies. Progress is hampered by the limited empirical constraints outside the restricted environment of the Local Group. In particular, the poorly-quantified time evolution of the molecular cloud life cycle, star formation, and feedback obstructs robust predictions on the scales smaller than the disc scale height that are resolved in modern galaxy formation simulations. We present a new statistical method to derive the evolutionary time line of molecular clouds and star-forming regions. By quantifying the excess or deficit of the gas-to-stellar flux ratio around peaks of gas or star formation tracer emission, we directly measure the relative rarity of these peaks, which allows us to derive their lifetimes. We present a step-by-step, quantitative description of the method and demonstrate it spractical application. The method’s accuracy is tested in nearly 300 experiments using simulated galaxy maps, showing that it is capable of constraining the molecular cloud lifetime and feedback time-scale to < 0.1 dex precision. Access to the evolutionary timeline provides a variety of additional physical quantities, such as the cloud-scale star formation efficiency, the feedback outflow velocity, the mass loading factor, and the feedback energy or momentum coupling efficiencies to the ambient medium. We show that the results are robust for a wide variety of gas and star formation tracers, spatial resolutions, galaxy inclinations, and galaxy sizes. Finally,we demonstrate that our method can be applied out to high redshift (z<~4) with a feasible time investment on current large-scale observatories. This is a major shift from previous studies that constrained the physics of star formation and feedback in the immediate vicinity of the Sun. DETAILS: With the presented method at hand, it is possible to empirically constrain the main unknown singalaxy formation simulations, such as the star formation time-scale, the star formation efficiency, the feedback outflow rate, and its coupling efficiency. We are currently carrying out systematic applications of the method to a large sample of nearby galaxies aimed at probing and understanding these physical quantities as a function of the galactic environment. Initially,thisfocusesonsingle-tracerobservationsofindividualgalaxies, such as NGC300 (Kruijssen et al. 2018), M33 (Hygate et al. in prep.), and M31 (Schruba et al. in prep.), enabling a detailed understanding of the interplay between galactic environment and the cloud life cycle across the face of nearby
a. stars b. galaxies c. quasars d. singalaxy
a. bounds b. lateshifts c. account d. observation
Q80.An uncertainty principle for star formation–II. A new method for characterising the cloud-scale physics of star formation and feed back across cosmic history. J. M. Diederik Kruijssen, Andreas Schruba,4 Alexander P. S. Hygate, Chia-Yu Hu, Daniel T. Haydon and Steven N. Longmore, Accepted 2018 April 27. Received 2018 April 23; in original form 2017 October 5.ABSTRACT The cloud-scale physics of star formation and feedback represent the main uncertainty in galaxy formation studies. Progress is hampered by the limited empirical constraints outside the restricted environment of the Local Group. In particular, the poorly-quantified time evolution of the molecular cloud life cycle, star formation, and feedback obstructs robust predictions on the scales smaller than the disc scale height that are resolved in modern galaxy formation simulations. We present a new statistical method to derive the evolutionary time line of molecular clouds and star-forming regions. By quantifying the excess or deficit of the gas-to-stellar flux ratio around peaks of gas or star formation tracer emission, we directly measure the relative rarity of these peaks, which allows us to derive their lifetimes. We present a step-by-step, quantitative description of the method and demonstrate it spractical application. The method’s accuracy is tested in nearly 300 experiments using simulated galaxy maps, showing that it is capable of constraining the molecular cloud lifetime and feedback time-scale to < 0.1 dex precision. Access to the evolutionary timeline provides a variety of additional physical quantities, such as the cloud-scale star formation efficiency, the feedback outflow velocity, the mass loading factor, and the feedback energy or momentum coupling efficiencies to the ambient medium. We show that the results are robust for a wide variety of gas and star formation tracers, spatial resolutions, galaxy inclinations, and galaxy sizes. Finally,we demonstrate that our method can be applied out to high redshift (z<~4) with a feasible time investment on current large-scale observatories. This is a major shift from previous studies that constrained the physics of star formation and feedback in the immediate vicinity of the Sun. DETAILS: With the presented method at hand, it is possible to empirically constrain the main unknown singalaxy formation simulations, such as the star formation time-scale, the star formation efficiency, the feedback outflow rate, and its coupling efficiency. We are currently carrying out systematic applications of the method to a large sample of nearby galaxies aimed at probing and understanding these physical quantities as a function of the galactic environment. Initially,thisfocusesonsingle-tracerobservationsofindividualgalaxies, such as NGC300 (Kruijssen et al. 2018), M33 (Hygate et al. in prep.), and M31 (Schruba et al. in prep.), enabling a detailed understanding of the interplay between galactic environment and the cloud life cycle across the face of nearby
a. stars b. galaxies c. quasars d. singalaxy
Q81. arXiv:1805.02710 [physics.app-ph]: On the solution of coupled heat and moisture transport in porous material. Julien Berger (LOCIE), Suelen Gasparin (LAMA), Denys Dutykh (LAMA), Nathan Mendes (PUCPR), Arxiv Org, / Hal. (Submitted on 20 Apr 2018). BSTRACT: Comparisons of experimental observation of heat and moisture transfer through porous building materials with numerical results have been presented in numerous studies reported in literature. However, some discrepancies have been observed, highlighting underestimation of sorption process and overestimation of desorption process. Some studies intend to explain the discrepancies by analysing the importance of hysteresis effects as well as carrying out sensitivity analyses on the input parameters as convective transfer coefficients. This article intends to investigate the accuracy and efficiency of the coupled solution by adding advective transfer of both heat and moisture in the physical model. In addition, the efficient Scharfetter and Gummel numerical scheme is proposed to solve the system of advection-diffusion equations, which has the advantages of being well-balanced and asymptotically preserving. Moreover, the scheme is particularly efficient in terms of accuracy and reduction of computational time when using large spatial discretisation parameters. Several linear and non-linear cases are studied to validate the method and highlight its specific features. At the end, an experimental benchmark from the literature is considered. The numerical results are compared to the experimental data for a pure diffusive model and also for the proposed model. The latter presents better agreement with the experimental data. The influence of the hysteresis effects on the moisture capacity is also studied, by adding a third differential equation. CONCLUSIONS: the improved advective–diffusive model, there is a better agreement between the numerical results and the experimental data. The momentum equation has not been taken into account in the physical model. Thus, a constant mass average velocity within the material porous structure has been estimated. Despite the inclusion of the advection transfer mechanism provides a better agreement with the experimental data, some of discrepancies still remain, particularly at the end of the desorption cycle, which might be due to the presence of hysteresis effects in the moisture capacity of the material. Thus, the model has been improved by adding also a third differential equation on the moisture capacity, enabling to interpolate between the adsorption and desorption equilibrium curves. This hysteretic diffusive–advective model provided the best results with a residual lower than 0.04 for the vapor pressure and 1.4 · 10^−3 for the
a. temperature b. presuure c. hysteresis d. diffusion.
a. temperature b. presuure c. hysteresis d. diffusion.
Q82. arXiv:1805.03311 [gr-qc]: Shadow of a black hole at cosmological distance. Gennady S. Bisnovatyi-Kogan, Oleg Yu. Tsupko. (Submitted on 8 May 2018): ABSTRACT: Cosmic expansion is expected to influence on the size of black hole shadow observed by co-moving observer. Except the simplest case of Schwarzschild black hole in de Sitter universe, analytical approach for calculation of shadow size in expanding universe is still not developed. In this paper we present approximate method based on using angular size redshift relation. This approach is appropriate for general case of any multicomponent universe (with matter, radiation and dark energy). In particular, we have shown that supermassive black holes at large cosmological distances in the universe with matter may give a shadow size approaching to the shadow size of the black hole in the centre of our galaxy, and present sensitivity limits. Concluding remarks (i) As discussed above, it seems to be very difficult to calculate exactly the shadow size in a general case of the expanding universe. Here we have derived the approximate formula for the shadow size as seen by a distant co-moving observer using angular diameter redshift relation and effective linear size of the shadow. Formula can be easily applied for calculation of the shadow in any multicomponent universe (with matter, radiation and dark energy), in approximation that co-moving observer is far from a black hole. In particular case of Schwarzschild–de-Sitter (when the expansion is driven by cosmological constant only) our approximate results agree with known exact solution. Our formula also gives the correct results for a case of small z. (ii) Spectacular thing following from our consideration is that in presence of the matter component the shadow size of supermassive black holes at cosmological distances may reach the values which are only one order of magnitude less than the shadow size in the center of our galaxy and the present sensitivity limits. Moreover, black holes at larger values of z will lead to even larger size of the shadow. Recent radio observations of absorption background 21 cm line have revealed some properties of universe up to z ≃ 20. Outstanding future project ’James Webb Space Telescope’ (https://jwst.nasa.gov) designed for observations at large z in infrared would be able to discover the objects presumably of such large redshifts. Subsequent observations of these objects with high resolution can reveal the shadow of supermassive black hole at large cosmological
a. expansion b. detour c. sensitivity d. distances
Q83. arXiv:1805.03629 [astro-ph.CO]: General Modified Gravity With 21cm Intensity Mapping: Simulations and Forecast. C. Heneka, L. Amendola. (Submitted on 9 May 2018): ABSTRACT: Line intensity mapping opens up a new and exciting window for probing cosmology and fundamental physics during the Epoch of Reionisation, extending to redshifts previously untested by galaxy surveys. The power spectra of these line fluctuations are a promising tool to test gravity over a large range of scales and redshifts. We simulate cosmological volumes of 21cm fluctuations in general parametrisations of modified gravity, in order to calculate the corresponding power spectra, where additional parameters are the initial condition of matter perturbations α and the scale-dependent defied gravity parameter Y (also known as Geff ) that measures deviations from GR in the Poisson equation. We show the impact of these model-independent modifications of gravity, to either delay or expedite reionisation. For the 21cm intensity mapping survey to be performed by the SKA mission, we forecast the ability of line intensity mapping to constrain the parameters Y and α at redshifts z=6−11 , where Y is assumed constant during this epoch (but without requiring constancy at all times). In our most conservative scenario, the Y parameter can be constrained at the tens of percent level, while for improved modelling of foregrounds as well as of the (mildly) non-linear regime, up to sub-percent level constraints are attainable. We show the impact of jointly estimating reionisation model parameters and corresponding parameter correlations, as well as of foreground removal. CONCLUSIONS: We note, that tomography is crucial for constraints not to degrade significantly when adding reionisation model parameters. We showed with a Fisher matrix forecast, that the constraints on modified gravity parameters, alongside with the standard matter density Ωm,0 and dark energy equation of state parameters w0 and wa, can reach the sub-percent level for example for a deviation of Y from a GR Poisson equation, when assuming an intensity mapping experiment of the type of SKA stage 1. When disregarding scales beyond the shot-noise scale, reaching for example 4% constraints on Y is within reach. Whether these levels can be reached, crucially depends on the foreground treatment and modelling of the (mildly) non-linear regime. Extending the set of parameters from cosmology-only to reionisation model parameters for our fiducial model, chosen to match available present-day constraints both for cosmology and astrophysics, does not degrade parameter constraints significantly. Here we note, that having different tomographic bins in redshift is a deciding factor for parameter constraints not to degrade. We also stress that modelling the (mildly) non-linear regime turns out to be more crucial for stringent constraints on general modifications of gravity, than for example degeneracies with astrophysical model parameters. To conclude, competitive constraints on modifications of gravity at redshifts during the EoR untested so far are possible for the first time with tomographic 21cm experiments. This brings even testing time- or scale-dependence for modifications of gravity at high redshift within reach of upcoming intensity mapping
a. inclusions. b. experiments c. results d. domains
Q84. arXiv:1805.03229 [cond-mat.stat-mech]: Hermite polynomials and Fibonacci Oscillators. Andre A. Marinho, Francisco A. Brito. (Submitted on 8 May 2018). ABSTRACT: We compute the (q1,q2)-deformed Hermite polynomials by replacing the quantum harmonic oscillator problem to Fibonacci oscillators. We do this by applying the Jackson derivative. The deformed energy spectrum is also found in terms of these parameters. We conclude that the deformation is more effective in higher excited states. We conjecture that this achievement may find applications in the inclusion of disorder and impurity in quantum systems. The ordinary quantum mechanics is easily recovered as q1 = q2 = 1. INTRODUCTION: A new proposal for the q-calculation is the inclusion of two distinct deformation parameters in some physical applications. Starting with the generalization of q-algebra, was generalized the Fibonacci sequence. Here, the numbers are in that sequence of generalized Fibonacci oscillators, where new parameters (q1,q2) are introduced. They provide a unification of quantum oscillators with quantum groups, keeping the degeneracy property of the spectrum invariant under the symmetries of the quantum group. The quantum algebra with two deformation parameters may have a greater flexibility when it comes to applications in realistic phenomenological physical models. CONCLUSIONS: the Fibonacci oscillators have modified behaviour in the stationary states. It is clear that as the deformation parameters decrease in relation to the undeformed case q1 = q2 = 1, the differentiated behaviour of the curves becomes more evident. This also becomes clear as we look at the Hermite polynomials where H3 feels a greater presence of q1 and q2 than H1. We can conclude that the more the states are excited the more strong is the deformation on them. This may find interesting applications in quantum mechanics such as inclusion of disorders and impurities in the quantum system. For instance, in several studies were put forward uncovering the fact that the q-deformation affects the oscillator frequency which may be associated with the changing in the strength of the ‘spring constant’ associated with such an oscillator as a consequence of introduction of impurities or disorders in the
a. system b. configuration c. evident d. symmetries
Q85. arXiv:1805.03529 [cond-mat.str-el]: Spectroscopic evidence for temperature-dependent convergence of light and heavy hole valence bands of PbQ (Q=Te, Se, S). J. Zhao, C. D. Malliakas, K. Wijayaratne, V. Karlapati, N. Appathurai, D. Y. Chung, S. Rosenkranz, M. G. Kanatzidis, U. Chatterjee. (Submitted on 9 May 2018): ABSTACT: We have conducted temperature dependent Angle Resolved Photoemission Spectroscopy (ARPES) study of the electronic structures of PbTe, PbSe and PbS. Our ARPES data provide direct evidence for the \emph{light} hole upper valence bands (UVBs) and hitherto undetected \emph{heavy} hole lower valence bands (LVBs) in these materials. An unusual temperature dependent relative movement between these bands leads to a monotonic decrease in the energy separation between their maxima with increasing temperature, which is referred as band convergence and has long been believed to be the driving factor behind extraordinary thermoelectric performances of these compounds at elevated temperatures. DETAILS: The positions of ΩU and ΩC agree well with the peak positions of the second derivative of the EDC. Therefore, ∆(T)=ΩU(T)-ΩL(T) of PbTe like PbSe or PbS can be plotted. It is evident that ∆ of each PbQ sample decreases monotonically with increasing T In the T range of our measurements. ∆(T) can be well represented by straight lines. From linear extrapolation of ∆(T) to zero, a characteristic temperature T∗ can be defined, at which the BM of the LVB is expected to merge with that of the UVB. Estimated value of merging temperature T∗∼813K (PbTe), 1148K (PbSe) and 1296K (PbS). Although such estimation of T∗ involves an extrapolation over a large T range, the values of T∗ obtained from our ARPES data agree reasonably with those from recent magnetic and optics measurements. We provide further details concerning the connection between various attributes of our T dependent measurements and those from the literature in the supplementary section. Monotonic T dependence of ∆ suggests that PbQ should become semiconductors with indirect band gap for T>T∗, where the heavy hole LVB rises in energy above the light hole UVB. In this scenario, the charge transport in PbQ should be dominated by the heavy holes created due to thermal excitations as T approaches T∗ and ∆(T=T∗)∼kBT∗. This band convergence increases the density of states of heavier holes, and thus, results in an enhanced Seebeck coefficient and thermoelectric power factor at higher T’s. All these are responsible for superior thermoelectric performance of PbQ at elevated
a. electric fields b. scenarios c. temperatures d. performance
Q86. arXiv:1805.01602 [physics.app-ph]: Silicon Oxide Electron-Emitting Nanodiodes. Gongtao Wu, Zhiwei Li, Zhiqiang Tang, Dapeng Wei, Gengmin Zhang, Qing Chen, Lian-Mao Peng, Xianlong Wei (Submitted on 4 May 2018). ABSTRACT: Electrically driven on-chip electron sources that do not need to be heated have been long pursued because the current thermionic electron sources show the problems of high power consumption, slow temporal response, bulky size, etc., but their realization remains challenging. Here we show that a nanogap formed by two electrodes on a silicon oxide substrate functions as an electron-emitting nanodiode after the silicon oxide in the nanogap is electrically switched to a high-resistance conducting state. A nanodiode based on graphene electrodes can be turned on by a voltage of ~7 V in ~100 ns and show an emission current of up to several microamperes, corresponding to an emission density of ~10^6 A cm^-2 and emission efficiency as high as 16.6%. We attribute the electron emission to be generated from a metal-insulator-metal tunnelling diode on the substrate surface formed by the rupture of conducting filaments in silicon oxide. An array of 100 nanodiodes exhibits a global emission density of 5 A cm^-2 and stable emission with negligible current degradation over tens of hours under modest vacuum. The combined advantages of a low operating voltage, fast temporal response, high emission density and efficiency, convenient fabrication and integration, and stable emission in modest vacuum make silicon oxide electron-emitting nanodiodes a promising on-chip alternative to thermionic emission sources. CONCLUSIONS: In summary, by electrically forming a surface M-I-M tunnelling diode in silicon oxide, a nanogap spaced by two electrodes on a silicon oxide substrate functions as an electron emitting nanodiode with low operating voltage, fast temporal response, and dense, efficient and stable emission in a modest vacuum. The outstanding electron emission performances and the convenient fabrication and integration by using microfabrication technologies make the EEND a promising on-chip electron source in the forms of both single nanoscale sources for micro/nanoscale vacuum electronic devices and large scale source arrays to replace thermionic electron sources in conventional vacuum electronic devices. The on-chip nature of EENDs also provides a new route of scaling down vacuum electronic devices on a
a. chip b. diode c. nanodiode d. substrate.
Q87. arXiv:1805.03447 [astro-ph.HE]: The necessity of including magnetic fields in simulating core collapse supernovae. Noam Soker (Technion, Israel): (Submitted on 9 May 2018): ABSTRACT: I find that an ingredient that was added in a recent study to facilitate the delayed neutrino explosion mechanism of core collapse supernovae, namely, large scale perturbations in the pre-collapse core, has a larger positive influence on the jittering jets explosion mechanism. By following the specific angular momentum of the accreted mass on to the newly born neutron star, I find that the accreted mass is likely to form intermittent accretion belts and disks, although they might lack axisymmetrical structure. These accretion belts and disks are likely to launch jets, but this can be simulated only if magnetic fields are included in the numerical code, as well as high numerical resolution that follows the rotation of the newly born neutron star and the shear in the accretion flow. I also discuss the possibility that the rotation of the pre-collapse core is important in increasing the shear in the accretion flow, hence the amplification of the magnetic fields. I repeat again my call for a paradigm shift from a neutrino-driven to a jet-driven explosion mechanism of massive stars. Such a paradigm shift will bring the recognition that to simulate core collapse supernovae one must use magneto-hydrodynamical numerical codes. SUMMARY: The main result of this study is that the angular momentum of the accreted mass in the simulation of Mu¨ller et al. who introduced perturbations in the pre-collapse core, can lead to the formation of intermittent accretion belts and disks around the newly born neutron star. However, to derive bipolar outflows, namely jets, from this accretion flow one must include magnetic fields in the simulations, as well as high resolution that enables to follows the shear between the down flows and the rotating neutron star. The magnetic fields are expected to be very strong. Firstly, the pre-collapse core is likely to amplify magnetic fields. Zilberman et al., concluded from their study of the rotational shear in pre-collapsing cores that even slowly rotating pre-collapse cores might amplify magnetic fields in the core, and after collapse in the zone above the newly born neutron star. Secondly, instabilities above the newly born neutron star can further amplify the magnetic field. Thirdly, the accretion disks and accretion belts substantially increase the magnetic field strength. I repeat again my call for a paradigm shift from a neutrino-driven to a jet-driven explosion mechanism of massive stars. Most CCSNe are exploded by jittering jets, but some are exploded by jets that maintain a fixed axis. In the present study this call is supported by the finding that an ingredient that was added to facilitate the delayed neutrino mechanism, namely, large scale perturbations in the pre-collapse core, has a larger positive influence on the jittering jets explosion
a. studies b. views c. jitters d. mechanism.
Q88. arXiv:1712.01153 [astro-ph.CO]: Gravitational clustering of cosmic relic neutrinos in the Milky Way. Jue Zhang, Xin Zhang. (Submitted on 4 Dec 2017 (v1), last revised 9 May 2018 (this version, v2)): ABSTRACT: The standard model of cosmology predicts the existence of cosmic neutrino background in the present Universe. To detect cosmic relic neutrinos in the vicinity of the Earth, it is necessary to evaluate the gravitational clustering effects on relic neutrinos in the Milky Way. Here we introduce a reweighting technique in the N-one-body simulation method, so that a single simulation can yield neutrino density profiles for different neutrino masses and phase space distributions. In light of current experimental results that favour small neutrino masses, the neutrino number density contrast around the Earth is found to be almost proportional to the square of neutrino mass. The density contrast-mass relation and the reweighting technique are useful for studying the phenomenology associated with the future detection of the cosmic neutrino background. DETAILS: In order to detect them in the neighbourhood of the Earth, a prerequisite would be to figure out the number density of relic neutrinos at our local environment. Although the standard model of cosmology does predict that the average number density of relic neutrinos in the current Universe is about 56 cm^−3 for each flavour, more relic neutrinos can be accreted around the Earth, due to the fact that massive neutrinos suffer from the gravitational potential of both dark matter (DM) and baryonic matter in the Milky Way (MW). Investigating the gravitational clustering of relic neutrinos is thus a necessary step towards interpreting the results from the future detection of cosmic neutrino background. CONCLUSIONS: In all the three physics scenarios considered in this work, the nature of Dirac neutrinos is assumed. Therefore, lepton number is conserved and thus only neutrinos, not anti-neutrinos, can be captured. Regarding the neutrino helicity states, in the early Universe both left-handed and right-handed chiral states are relativistic, and therefore they are left-handed and right-handed helical states as well. In the evolution of the Universe, the helicites of neutrinos are preserved, so that at the present time the left-handed and right-handed helical neutrino states correspond to the left-handed and right-handed chiral states in the early Universe, respectively. In Standard Case, the standard model of cosmology predicts the average number density of left-handed helical neutrino states to be n0 = 56 cm^−3 for each mass eigenstate at the present time, while almost no existence of right-handed helical states. For a given value of the total neutrino mass sum(mν), we can obtain the three individual neutrino masses with the two mass-squared differences from neutrino oscillation experiments. Here we adopt ∆m^221 ≡ (m2^2 − m1^2) = 7.56 × 10^−5 eV^2 and |∆m^231| ≡ |m3^2 −m1^2 | = 2.55×10^−3 eV^2. Taking neutrino mass sum(mν) = 0.23 eV as an example, we obtain (m1,m2,m3) = (0.0711 eV,0.0717 eV,0.087 eV) in NH. From the fitted function we find that the neutrino density contrasts δν are (0.22,0.23,0.35) for the three mass eigenstates, respectively, and therefore the corresponding number densities of left-handed helical states around the Earth are 68.44 cm^−3, 68.64 cm^−3 and 75.53 cm^−3. Finally, we obtain the capture rate Γ = 4.97 yr^−1 in this case. The calculation of capture rates in NP Case I and II can be performed similarly, except that in NP Case Iand II there are additional contributions from the right-handed helical states of neutrinos, whose average number densities at the present time are taken to be 0.28n0 and 0.52n0 for each mass eigenstate in NP Case I and II, respectively. Gravitational clustering effects on the right-handed helical states are calculated in the same way as the left-handed helical states, except that in NP Case II the fitted relation for the fully-degenerate phase space distribution should be
a. adopted b. used c. adopted d. curtailed
Q89. arXiv:1805.03753 [quant-ph]: Projecting onto any two-photon polarization state using linear optics. G. S. Thekkadath, L. Giner, X. Ma, J. Flórez, J. S. Lundeen. (Submitted on 9 May 2018): ABSTRACT: Projectors are a simple but powerful tool for manipulating and probing quantum systems. For instance, projecting two-qubit systems onto maximally entangled states can enable quantum teleportation. While such projectors have been extensively studied, partially-entangling measurements have been largely overlooked, especially experimentally, despite their important role in quantum foundations and quantum information. Here, we propose a way to project two polarized photons onto any state with a single experimental setup. Our scheme does not require optical non-linearities or additional photons. Instead, the entangling operation is provided by Hong-Ou-Mandel interference and post-selection. The efficiency of the scheme is between 50% and 100%, depending on the projector. We perform an experimental demonstration and reconstruct the operator describing our measurement using detector tomography. Finally, we flip the usual role of measurement and state in Hardy's test by performing a partially-entangling projector on separable states. The results verify the entangling nature of our measurement with six standard deviations of confidence. CONCLUSIONS: In summary, we proposed a straightforward way of projecting two polarized photons onto any state. Our scheme has an efficiency of at least 50% which far exceeds that of any scheme based on a probabilistic CNOT gate (11%). We performed an experimental demonstration and reconstructed the operator describing our measurement using detector tomography. Finally, we flipped the usual role of measurement and state in Hardy’s test and verified the entangling nature of our measurement. We anticipate that our scheme will find applications in quantum metrology and quantum information. In single-parameter estimation problems, entangling measurements cannot in general extract more information about that parameter than separable measurements. However, in multi-parameter problems such as state estimation or certain phase estimation scenarios, our scheme could be used to implement the partiallyor maximally-entangling projectors that optimize the amount of information extracted. Although limited to two qubits, such a measurement would be of foundational importance in quantum information as it saturates a fundamental limit in the amount of information that can be extracted from quantum systems. Finally, our scheme can also be used prepare any two-photon polarization state, uniquely without modifying the photon
a. axis b. state c. scheme d. source.
Q90. arXiv:1805.05341 [astro-ph.GA]: The Galactic Centre source G2 was unlikely born in any of the known massive binaries. Diego Calderón, Jorge Cuadra, Marc Schartmann, Andreas Burkert, Philipp Plewa, Frank Eisenhauer, Maryam Habibi. (Submitted on 14 May 2018). ABSTRACT:The source G2 has already completed its pericentre passage around Sgr A*, the super-massive black hole in the centre of our Galaxy. Although it has been monitored for 15 years, its astrophysical nature and origin still remain unknown. In this work, we aim to test the hypothesis of G2 being the result of a stellar wind collision. To do so, we study the motion and final fate of gas clumps formed as a result of collisions of stellar winds in massive binaries. Our approach is based on a test-particle model in order to describe the trajectories of such clumps. The model takes into account the gravitational field of Sgr A*, the interaction of the clumps with the interstellar medium as well as their finite lifetimes. Our analysis allows us to reject the hypothesis based on four arguments: i) if G2 has followed a purely Keplerian orbit since its formation, it cannot have been produced in any of the known massive binaries since their motions are not consistent; ii) in general, gas clumps are evaporated through thermal conduction on very short timescale (< 100yr) before getting close enough to Sgr A*; iii) IRS 16SW, the best candidate for the origin of G2, cannot generate clumps as massive as G2; and iv) clumps ejected from IRS 16SW describe trajectories significantly different to the observed motion of G2. DETAILS:Massive binaries orbiting Sgr A*. The inner parsec of our Galaxy hosts about 30 Wolf-Rayet stars. Photometric and spectroscopic studies have provided valuable information of their orbits and stellar winds. Years of monitoring allowed to identify three binary systems among this sample (Martins et al. 2006; Pfuhl et al. 2014). However, there are other four sources considered as binary candidates (see Pfuhl et al. 2014). Although some of them showed changes on either brightness or radial velocity, there are not enough observations to confirm their binarity. Furthermore, only two of them are within half a parsec from Sgr A*. The other two are at ∼ 1.5 pc, so latest surveys did not include them. Therefore, throughout this work we focus uniquely on systems already confirmed as binaries. CONCLUSIONS: Our analytical and test-particle simulation results show that we cannot reconcile the hypothesis of G2 being a gas clump formed in any known massive binary system with its observed motion. The results that support this conclusion are the following. (i) G2 orbital fit is not consistent with an origin in IRS 16SW. It is not possible to match IRS 16SW and G2 positions on the sky if we trace their orbits back in time. Their projected separation (lower limit of the physical separation) always remains larger than ∼ 0.2 arcsec. (ii) Cold gas clumps do not live long enough. The hot environment close to Sgr A* evaporates cold clumps very rapidly via thermal conduction. At the orbit of IRS 16SW, massive clump lifetimes and the free-fall timescale are comparable (∼ 200 yr). Therefore, only the most massive of them would live long enough to reach the vicinity of Sgr A*. (iii) IRS 16SW cannot produce massive enough clumps. Given its orbital and stellar wind parameters, we can expect it to create clumps with initial masses of at most 3 Earth masses. Roughly half of that mass would be lost before reaching Sgr A*, in disagreement with the observed G2 mass. (iv) Our test-particle simulations cannot reproduce G2 observations. A model based on IRS 16SW ejecting clumps along its orbit is not capable of producing any clump that matches the observed G2 positions on the sky and radial velocity measurements. These results, together with our previous work on encounters between single stars (Caldero´n et al. 2016), reject the idea of G2 being created in a stellar wind collision. However, our work does not rule out the “purely gaseous cloud” scenario in general. Other gas cloud models remain as possible explanations. In order to reject those, following a procedure similar to the one presented in this paper, it would be necessary to first identify candidate progenitors, e.g., a star recently going through a nova outburst, or being partially
a. disturbed b. disrupted c. destroyed d. condoned.
Q91. arXiv:1805.05365 [astro-ph.GA]: Metals and dust in the neutral ISM: the Galaxy, Magellanic Clouds, and damped Lyman-α absorbers. Annalisa De Cia. (Submitted on 14 May 2018). ABSTRACT: Context. The presence of dust in the neutral interstellar medium (ISM) dramatically changes the metal abundances that we measure. Understanding the metal content in the neutral ISM, and a direct comparison between different environments, has been hampered to date because of the degeneracy to the observed ISM abundances caused by the effects of metallicity, the presence of dust, and nucleosynthesis. Aims. We study the metal and dust content in the neutral ISM consistently in different environments, and assess the universality of recently discovered sequences of relative abundances. We also intend to assess the validity of [Zn/Fe] as a tracer of dust in the ISM. This has recently been cast into doubt based on observations of stellar abundances, and needs to be addressed before we can safely use it to study the ISM. Methods. In this letter we present a simple comparison of relative abundances observed in the neutral ISM in the Galaxy, the Magellanic Clouds, and damped Lyman-{\alpha} Absorbers (DLAs). The main novelty in this comparison is the inclusion of the Magellanic Clouds. Results. The same sequences of relative abundances are valid for the Galaxy, Magellanic Clouds, and DLAs. These sequences are driven by the presence of dust in the ISM and seem 'universal'. Conclusions. The metal and dust properties in the neutral ISM appear to follow a similar behaviour in different environments. This suggests that a dominant fraction of the dust budget is built up from grain growth in the ISM depending of the physical conditions and regardless of the star formation history of the system. In addition, the DLA gas behaves like the neutral ISM, at least from a chemical point of view. Finally, despite the deviations in [Zn/Fe] observed in stellar abundances, [Zn/Fe] is a robust dust tracer in the ISM of different environments, from the Galaxy to DLAs. DETAILS: The understanding of metal content in the neutral ISM and a direct comparison of different environments has been hampered for years by the degeneracy to the metal budget of the neutral ISM caused by the effects of metallicity, dust depletion, and nucleosynthesis. A leap forward was made by De Cia et al. (2016), who found empirical relations (sequences) between relative abundances observed in the ISM of the Galaxy and DLAs. This was used in turn to develop a new method for characterizing dust depletion in different environments. CONCLUSIONS: We conclude that the DLA gas mostly behaves like the neutral ISM, at least from a chemical point of view, and is unlikely to be associated with the CGM at large distances from the DLA galaxy. This strengthens the case for using DLAs as a complementary tool to study galaxies, out to high redshift and down to low masses. Finally, we demonstrate the validity of [Zn/Fe] as a robust dust tracer in the ISM of different environments, from the Galaxy to
a. Its centre b. other Galaxies c. DLA galaxy d. DLAs.
Q92. arXiv:1805.05577 [astro-ph.CO]: Axion dark matter and the 21-cm signal. .Pierre Sikivie. (Submitted on 15 May 2018): ABSTRACT: It was shown in ref. [1] that cold dark matter axions reach thermal contact with baryons, and therefore cool them, shortly after the axions thermalize among themselves and form a Bose-Einstein condensate. The recent observation by the EDGES collaboration of a baryon temperature at cosmic dawn lower than expected under "standard" assumptions is interpreted as new evidence that the dark matter is axions, at least in part. Baryon cooling by dark matter axions is found to be consistent with the observation of baryon acoustic oscillations. DETAILS: The observation of the trough in the spectrum of cosmic microwave radiation caused by its absorption by neutral hydrogen atoms [3] at cosmic dawn, i.e. when the universe is bathed in starlight for the first time. Assuming it is correct, the EDGES observation reveals new important information. It informs us that the first stars formed approximately 180 million years after the Big Bang and that the primeval gas was heated to above the photon temperature approximately 100 million years later. Most importantly for the present discussion, it tells us the spin temperature of hydrogen atoms during this 100 million year epoch. The spin temperature Ts is, by definition, related to the relative population of the spin 1 and spin 0 lowest energy states of hydrogen: n1 n0 ≡ 3 × e−ω0/Ts where ω0 = (2π) 1.42 GHz is the angular frequency associated with hyperfine splitting in hydrogen, the so-called 21 cm line. We use units in which ¯ h = c = kB throughout. The spin temperature is intermediate between the baryon kinetic temperature Tk and the photon temperature Tγ (Tk ≤ Ts ≤ Tγ) being driven toward Tγ by 21 cm emission and absorption but driven towards Tk by atomic collisions and by Lyman-alpha emission and absorption. CONCLUSIONS: This fairly large value suggests that absorption of 21 cm radiation, which drives Ts up, may compete with the Wouthuysen-Field effect driving it down. In that case the absorption would saturate before Ts reaches Tk. Whether baryon cooling by dark matter axions agrees with all observations remains to be seen. Eq. (2) allows predictions to be made. One concern is whether the drag on baryons dampens baryon acoustic oscillations. The damping of baryon acoustic oscillations by WIMP dark matter has been considered in refs. [25] and constraints on the scattering cross-section between WIMPs and baryons have been derived on this basis. Using Eq. (3), the fraction of energy removed from the baryon-photon fluid per Hubble time shortly before recombination is found to be of order 3·10−5 Y ℓ/t, which seems safely
a. big b. small c. oscillatory d. Intermediate.
Q93. arXiv:1805.05642 [astro-ph.HE]: Gamma-Ray Astrophysics. Alessandro De Angelis, Manuela Mallamaci. (Submitted on 15 May 2018). ABSTRACT: High-energy photons are a powerful probe for astrophysics and for fundamental physics in extreme conditions. During the recent years, our knowledge of the most violent phenomena in the Universe has impressively progressed thanks to the advent of new detectors for gamma rays, both at ground and on satellites. This article reviews the present status of high-energy gamma-ray astrophysics, with emphasis on the recent results and a look to the future. DETAILS: We will focus on the most energetic photons, indicated as gamma rays. In general, the term denotes the electromagnetic radiation above some 100keV, but we will dedicate the discussion especially to gamma rays in the high energy (between a few MeV and ∼ 30 GeV) and very high energy (& 30 GeV) regions. There is little doubt on the existence of photons in the PeV-EeV range, but so far cosmic gamma rays have been unambiguously detected in high energy and very high energy domains, the most energetic reaching ∼ 100TeV. During the recent years, a large amount of sources has been detected, revealing the existence of a very heterogeneous population that lights up the gamma-ray sky, in our Galaxy and beyond. Understanding and modelling the gamma-ray emission are compelling aspects per se, but have also other facets. Gamma rays are indeed intimately related to all cosmic messengers: charged cosmic rays, neutrinos and gravitational waves. Besides, they are an indirect probe for questions related to fundamental physics. This was decisive for obtaining the first successful localization of the first gamma ray emitter: the Crab Nebula was detected above 0.7TeV in 1989 by the Whipple collaboration, 37 years after the initial Cherenkov light pulse observation. Given a primary photon of 100 GeV, about 10 Cherenkov photons per square meter arrive at the level of mountain altitudes around 2000 m above sea level (a.s.l.). A collection area of 100 m2 is therefore sufficient to detect gamma ray showers. Since the Cherenkov light is faint, clear and almost dark nights are required for observations. As a consequence, this kind of instruments are characterized by a low duty cycle of about 15%. In addition, they have a small FoV ( . 5◦), but a high sensitivity and a low energy threshold. FUTURE DIRECTIONS: The current generation of detectors, both in space and on ground, is providing a wealth of information about the non-thermal Universe in the GeV-TeV energy band, as highlighted in the previous sections. However a key piece is missing: the MeV energy range. This scarcely explored domain is important since it is characteristic of nuclear transitions and of the nuclear de-excitation of molecular clouds excited by colliding CRs; in addition, it is the energy range where one expects the exhaustion of the electromagnetic counterpart of gravitational wave events and where one expects gamma rays from the conversion of axions in the core of
a. supernovae b. CRs c. domains d. localizations.
Q94. arXiv:1805.06394 [gr-qc]: Quantum Gravity phenomenology and metric formalism. Niccoló Loret, Leonardo Barcaroli, Giulia Gubitosi. (Submitted on 16 May 2018). ABSTRACT: n this proceedings for the MG14 conference, we discuss the construction of a phenomenology of Planck-scale effects in curved space-times, underline a few open issues and describe some perspectives for the future of this research line. DETAILS: Even if in this formalism the Casimir and world-lines are invariant under some generalised boost transformations, it is not clear whether this is the case also for the momentum space and the space-time line element (dsHℓ)^2 , which are derived from the metric. In fact, since the metric is now explicitly (x, ˙x)-dependent, it may be not possible anymore to obtain a formalization of the invariant line-elements in terms of the coordinates differentials. This may not be a problem, since line-element and metric are not something we observe, but just useful tools we infer from particles’ dynamics. At the same time metric formalism is fundamental in many aspects of General Relativity and we would like to preserve it also in it’s deformed version that we may want to formulate one day. CONCLUSIONS: The situation we described in this proceedings shows some results achieved and many open issues to solve for what concerns the use of metrics to formalise space-time-symmetries deformation models. The road ahead presents many choices. We could focus in understanding under which assumptions can we inject all this model deformation just in one geometric object, leaving unchanged the remaining relativistic structure of he theory. In this sense, tetradic formalism has proved to be very fruitful, but at the same time how can we build a relativistic framework on the invariant line-element if at the end this one would not result a reliable landmark? A drastic solution to this problem could be to renounce to rely on metric formalism and investigate on Finsler geometry, as a way to formalise Planck-scale deformed relativistic symmetries, as an alternative to the implementation of those deformations directly on Riemannian geometry, since we don’t know yet if such an approach would or would not work. Another approach could be to build from scratch a theory which takes into account a complete scenario of curved phase-space, building a metric formalism from phase space
a. formalism b. discrete c. symmetries d. considerations
Q95. arXiv:1803.04973 [hep-th]: Quantum-first gravity. Steven B. Giddings. (Submitted on 13 Mar 2018 (v1), last revised 16 May 2018 (this version, v2)): ABSTRACT: This paper elaborates on an intrinsically quantum approach to gravity, which begins with a general framework for quantum mechanics and then seeks to identify additional mathematical structure on Hilbert space that is responsible for gravity and other phenomena. A key principle in this approach is that of correspondence: this structure should reproduce space-time, general relativity, and quantum field theory in a limit of weak gravitational fields. A central question is that of "Einstein separability," and asks how to define mutually independent subsystems, e.g. through localization. Familiar definitions involving tensor products or operator sub-algebras do not clearly accomplish this in gravity, as is seen in the correspondence limit. Instead, gravitational behaviour, particularly gauge invariance, suggests a network of Hilbert subspaces related via inclusion maps, contrasting with other approaches based on tensor-factorized Hilbert spaces. Any such localization structure is also expected to place strong constraints on evolution, which are also supplemented by the constraint of unitarity. CONCLUSIONS: In order to respect quantum mechanics, the evolution law must be unitary , e.g. yielding a unitary S-matrix in the context of states corresponding to asymptotically flat boundary conditions. Given the challenges of describing unitary quantum black hole (BH) evolution, this appears to be an important constraint. As a reminder, in an approximate description of black holes, the Hilbert space factorizes as HBH⊗Henv --> (4.1) corresponding to states of the BH and environment. Then, if the Hamiltonian does not allow transfer of information from HBH to Henv, and if HBH disappears as the black hole evaporates, as LQFT appears to indicate, unitarity is violated. This paper has reviewed arguments that a factorization (4.1) is not quite correct when one accounts for properties of gravity. However, subsystem structure that replaces (4.1) has also been described. An important question is whether the gravitational modifications to (4.1) that we have found are sufficient to resolve the unitarity problem – if nonlocality of quantized GR resolves the unitarity crises, we may see it perturbatively here. For example, while it has been noted that the leading-order description of standard dressing appears to rule out the suggested, role of soft quantum hair, it may be that a different higher-order effect leads to information about the internal state of a BH being accessible from outside. While this remains to be explored more completely, we have not seen an indication that the modifications to (4.1) are sufficient to restore unitarity. If perturbative modifications to subsystem structure, i.e. localization, in gravity do not directly resolve the unitarity problem, it appears that this provides an additional important clue about the nature of evolution – plausibly the existence of additional couplings between subsystems that go beyond quantized GR. The approach to modeling unitary evolution of BHs that has been proposed in, has been to parameterize such couplings, of a form that doesn’t violate our correspondence constraints. If this is the case, the necessity of consistent quantum evolution of BHs is providing us significant additional information about the non-perturbative structure of the
a Theory b. formalism c. evolution d. phenomenology.
Q96.arXiv:1805.02240 [gr-qc]: Graviton Mass and Memory. Ercan Kilicarslan, Bayram Tekin. (Submitted on 6 May 2018 (v1), last revised 16 May 2018 (this version, v2)). ABSTRACT: Gravitational memory (a residual change) arises after a finite gravitational wave pulse interacts with free masses. We calculate the memory effect for particle scattering in massive gravity as a function of graviton mass mg) and show that it is discretely different from the result of general relativity: the memory is reduced not just via the usual expected Yukawa decay but by a numerical factor which survives even in the massless limit. For mg ≤ 10^−29eV , the memory is significantly reduced for distances beyond 1Mpc as in the first observation of two black hole mergers which was at a distance of more than 200Mpc. Hence careful observations of the gravitational wave memory effect can rule out the graviton mass. We also show that adding higher curvature terms reduces the memory effect. DETAILS: All the effects of gravity are encoded in the metric tensor field g which needs no coordinates to be defined. General Relativity (GR) is intrinsically four dimensional and the full metric of space-time manifold g does not really evolve in time: it is what it is. So, if we had known how to obtain all the local observables from the metric for all physically relevant situations, we would not need any further nomenclatures such as memory effect, gravito-magnetism etc. But, since as local observers, we do not have full access to the fully consistent space-time, it pays to see space-time as space evolving in time, namely, to see space-time as a history of space. Such a dynamical picture requires a choice of time and other coordinates and leads to interesting phenomena and the gravitational memory is one such an event: the wave that enters the interaction with the detector masses differs in some well-defined sense from the wave that leaves the interaction. The best way to see the difference is to measure the change in the relative separation of the masses as this is related to the change in the wave profile. CONCLUSIONS: Recently gravitational memory effect received a renewed interest for general relativity with or without a cosmological constant, for various reasons some of which are: its related to black hole soft hair, asymptotic symmetries and its potential observation in the gravitational wave detectors. Here, we calculated the gravitational memory as a function of graviton mass and showed that for the strongest existing bounds on graviton mass, the memory is essentially wiped out for the sources located at distances above
a. 5Mpc b. 40Mpc c. 10Mpc d. 20Mpc
Q97.arXiv:1805.05875 [astro-ph.HE]: Low-energy electrons in GRB afterglow models. Guðlaugur Jóhannesson, Gunnlaugur Björnsson. (Submitted on 14 May 2018). ABSTRACT: Observations of gamma-ray burst (GRB) afterglows have long provided the most detailed information about the origin of this spectacular phenomena. The model that is most commonly used to extract physical properties of the event from the observations is the relativistic fireball model, where ejected material moving at relativistic speeds creates a shock wave when it interacts with the surrounding medium. Electrons are accelerated in the shock wave, generating the observed synchrotron emission through interactions with the magnetic field in the downstream medium. It is usually assumed that the accelerated electrons follow a simple power-law distribution in energy between specific energy boundaries and that no electron exists outside these boundaries. This work explores the consequences of adding a low-energy power-law segment to the electron distribution whose energy contributes insignificantly to the total energy budget of the distribution. The low-energy electrons have a significant impact on the radio emission, providing synchrotron absorption and emission at these long wavelengths. Shorter wavelengths are affected through the normalization of the distribution. The new model is used to analyze the light curves of GRB 990510 and the resulting parameters compared to a model without the extra electrons. The quality of the fit and the best fit parameters are significantly affected by the additional model component. The new component is in one case found to strongly affect the X-ray light curves showing how changes to the model at radio frequencies can affect light curves at other frequencies through changes in best fit model parameters. DETAILS: Gamma-ray bursts (GRBs) are the most powerful explosions in the Universe and can therefore be observed to very high redshift. They have been hypothesised to be tracers of star formation and thus be a probe of the star formation history of the early universe. CONCLUSIONS: The results of the analysis of GRB 990510 and the statistical preference for the additional electron component lend support to the need for more detailed treatment of the electron distribution in GRB afterglow modeling. This can in particular affect the determination of the energetics of the outflow and the density structure of the external medium. The power-law segment added in this work is just a simple modification of the electron energy distribution to explore its effects and further work is needed to get a more accurate physical picture. One such method is to simultaneously solve for the dynamics of the afterglow and the distribution of electrons. This was done in the work of (Geng et al. 2018) but their approach is limited to electron cooling and lacks the thermalization effect of the electrons that may be important for the lowest energy electrons. They also excluded several important effects, such as the EATS. Clearly, thereis room for considerable improvements in this area of GRB afterglow
a. self-interactions b. interactions c. large interactions d. oscillations.
Q102. arXiv:1806.10617 [astro-ph.HE]27 Jun 2018: Pulsar Astrophysics - The Next 50 Years Proceedings IAU Symposium No. 337, 2017 P. Weltevrede, B.B.P. Perera, L. Levin Preston & S. Sanidas. Pulsar observations at millimetre wavelengths., Spain email: torne@iram.es Abstract. Detecting and studying pulsars above a few GHz in the radio band is challenging due to the typical faintness of pulsar radio emission, their steep spectra, and the lack of observatories with sufficient sensitivity operating at high frequency ranges. Despite the difficulty, the observations of pulsars at high radio frequencies are valuable because they can help us to understand the radio emission process, complete a census of the Galactic pulsar population, and possibly discover the elusive population in the Galactic Centre, where low-frequency observations have problems due to the strong scattering. During the decades of the 1990s and 2000s, the availability of sensitive instrumentation allowed for the detection of a small sample of pulsars above 10GHz, and for the first time in the millimetre band. Recently, new attempts between 3 and 1mm (≈86−300GHz) have resulted in the detections of a pulsar and a magnetar up to the highest radio frequencies to date, reaching 291GHz (1.03mm). The efforts continue, and the advent of new or upgraded millimetre facilities like the IRAM 30-m, NOEMA, the LMT, and ALMA, warrants a new era of high-sensitivity millimetre pulsar astronomy in the upcoming years. DETAILS: One particular region where high-frequency surveys can be very useful is the centre of the Milky Way. Pulsars found in the Galactic Centre can help us to understand its enigmatic star formation history using their characteristics ages, map the gravitational potential using the pulsars as accelerometers, measure the gas properties and distribution and estimate the magnetic field through Faraday rotation effects. In addition, it is remarkable that one single pulsar in a suitable orbit around the supermassive black hole SgrA* would suffice to enable unprecedented black hole physics experiments and tests of General Relativity and alternative Gravity theories Summary The observations of pulsars at millimetre wavelengths are challenging, but provide unique insights into the pulsar emission properties, offer a way to probe dense ISM and find new pulsars and magnetars, and are a potential tool for precision black hole physics in the case that scattering prevents the detection of pulsars orbiting SgrA* at low frequencies. For this reason, we should continue the efforts to enable sensitive pulsar observations up to the highest possible frequencies. At the moment, at millimetre wavelengths the observations are concentrated at the IRAM 30-m radio telescope. In the future, larger facilities like NOEMA or the LMT have the potential to extend the sample of detectable pulsars between 3 and 0.8mm. Finally, a key facility will be ALMA, not only because it is the most sensitive (sub)millimetre telescope, but also because it is located in the southern hemisphere. Around 70% of all known pulsars have declination lower than zero degrees, and many of them are out of the visibility of the northern facilities. Therefore, the future observations with ALMA will offer the best chance to expand our comprehension of the pulsar emission physics, and have the potential to detect pulsars hidden at the Galactic Centre and other extreme-scattering
a. data b. regions c. amplitudes d. frequencies
Q103. arXiv:1806.10879 [astro-ph.HE]: Cosmogenic photon and neutrino fluxes in the Auger era, Rafael Alves Batista, Rogerio M. de Almeida, Bruno Lago, Kumiko Kotera. 28 Jun 2018/ ABSTRACT: The interaction of ultra-high-energy cosmic rays (UHECRs) with pervasive photon fields generates associated cosmogenic fluxes of neutrinos and photons due to photohadronic and photonuclear processes taking place in the intergalactic medium. We perform a fit of the UHECR spectrum and composition measured by the Pierre Auger Observatory for four source emissivity scenarios: power-law redshift dependence with one free parameter, active galactic nuclei, gamma-ray bursts, and star formation history. We show that negative source emissivity evolution is favoured if we treat the source evolution as a free parameter. In all cases, the best fit is obtained for relatively hard spectral indices and low maximal rigidities, for compositions at injection dominated by intermediate nuclei (nitrogen and silicon groups). In light of these results, we calculate the associated fluxes of neutrinos and photons. Finally, we discuss the prospects for the future generation of high-energy neutrino and gamma-ray observatories to constrain the sources of UHECRs. DETAILS: Ultra-high-energy cosmic rays (UHECRs) are particles, mostly atomic nuclei, with energies E >= 1 EeV (1 EeV ≡ 10^18 eV). Neither their origins nor the mechanisms whereby they are accelerated to such high energies have been unveiled. It is widely believed that UHECRs have extragalactic origin. Thus, they can interact with the intergalactic medium including photon fields such as the cosmic microwave background (CMB) and the extragalactic background light (EBL). Magnetic fields, too, play an important role in UHECR propagation. Because their distribution in the Universe is not well understood, the prospects for ultra-high-energy cosmic-ray astronomy are unclear. SUMMARY: Our study demonstrates that the detection of cosmogenic neutrinos is virtually guaranteed, even in the most pessimistic scenarios, provided that the projected instruments reach their expected sensitivities and that they operate for over a decade. From a different perspective, low cosmogenic fluxes as derived in the (1 + z)m scenario could be profitable for EeV neutrino astronomy. Such a scenario would imply that the neutrinos that would be detected first by future experiments would likely be those produced directly at the sources, via interactions of UHECRs with photon and baryon fields in the source environment. Abundant interactions should happen at the acceleration site of UHECRs, and theoretical models predict fluxes that are much higher than the level of cosmogenic neutrinos estimated there. In that case, it is advantageous that the cosmogenic neutrinos would constitute a low-level background, easing the identification of the first UHE neutrino point
a. views b. data c. scenario d. sources
Q104. arXiv:1807.08034 [astro-ph.HE]. Two novel approaches to the hadron-quark mixed phase in compact stars. Vahagn Abgaryan, David Alvarez-Castillo, Alexander Ayriyan, David Blaschke, Hovik Grigorian. (Submitted on 20 Jul 2018): ABSTRACT: First-order phase transitions, like the liquid-gas transition, proceed via formation of structures such as bubbles and droplets. In strongly interacting compact star matter, at the crust-core transition, but also at the hadron-quark transition in the core, these structures form different shapes dubbed "pasta phases". We describe two methods to obtain one-parameter families of hybrid equations of state (EoS) which mimic the thermodynamic behavior of pasta phases in between a low-density hadron and a high-density quark matter phase, thus generalizing the Maxwell construction. The first method replaces the behavior of pressure vs. chemical potential in a finite region around the critical %chemical potential pressure of the Maxwell construction by a polynomial interpolation. The second method uses extrapolations of the hadronic and quark matter EoS beyond the Maxwell point to define a mixing of both with weight functions bounded by finite limits around the Maxwell point. We apply both methods to the case of a hybrid EoS with a strong first order transition that entails the formation of a third family of compact stars and the corresponding mass twin phenomenon. We investigate for both models the robustness of this phenomenon against variation of the single parameter, the pressure increment at the critical chemical potential which quantifies the deviation from the Maxwell construction. We also show sets of results for other compact star observables than mass and radius, namely the moment of inertia and the baryon mass. DETAILS: The understanding of the properties of dense matter in compact star interiors is a subject of current research. Recently, great progress in this direction has been achieved by the detection of the gravitational radiation which emerged from the in spiral phase of two coalescing compact stars, an event named GW170817. Since it was observed also in all other bands of the electromagnetic spectrum, it marked the birth of multi-messenger astronomy. SUMMARY: The methods presented here can potentially be applied to the compact star crust-core transition as well. Just like at the hadron-quark boundary, the transition at the bottom of the crust may proceed via pasta phases dominated by Coulomb forces and surface tension effects Further astrophysical aspects of mixed phases inside neutron stars include potentially observable effects such as the rotational evolution, pulsar glitches, gravitational wave emission and cooling. They could be sufficiently sensible to the nature of the phase transition, proceeding via pasta phases or not, and thus provide potential signatures of the presence and extension of a mixed phase in stars which are.
a. diffuse b. compact c. reliable d. uncertain
Q105. arXiv:1807.08121 [astro-ph.SR]: Low resolution spectroscopic investigation of Am stars using Automated method. Kaushal Sharma, Santosh Joshi, H. P. Singh. (Submitted on 21 Jul 2018). ABSTRACT: Automated method of full spectrum fitting gives reliable estimates of stellar atmospheric parameters (Teff, logg and [Fe/H]) for late A, F, G and early K type stars. Recently, the technique was further improved in the cooler regime and the validity range was extended up to M6 - M7 spectral type (Teff ∼2900K). The present study aims to explore the application of this method on the low-resolution spectra of Am stars, a class of chemically peculiar (CP) stars, to examine its robustness for these objects. We use ULySS with MILES (Medium-resolution INT Library of Empirical Spectra) V2 spectral interpolator for parameter determination. Determined Teff and logg are found to be in good agreement with those obtained from high-resolution spectroscopy. PUBLISHED: Proceeding for "First Belgo-Indian Network for Astronomy & Astrophysics (BINA) workshop", held in Nainital (India), November 15-18, 2016. Published in Bulletin of Li\`ege Royal Society of Sciences Vol. 87, p. 121-124: Discussionandfutureplans These stars have recently been studied by Joshi et al. (2017) in high-resolution spectroscopic mode. Comparison of two series of measurements shows an average difference of −377±178K, and−0.48±0.32dex for Teff and logg respectively, whereas the mean estimated errors are 193K and 0.43dex for the two parameters. Within the uncertainties, the two series of measurements are consistent. Full spectrum fitting method has been employed on peculiar stars for the first time, therefore it is important to validate the method for a larger set of such objects. For this purpose, we plan to enhance our test sample by gathering the CP stars’ spectra from various spectral archives. Once validated, this method would be useful as a parameter reduction pipeline for the low resolution spectra obtained using FOSC and other future instruments at Devasthal Optical Telescope (DOT) using
a. 3.6-m b. 3.9-m c. 4.2-m d. 5.6-m
Q106. arXiv:1808.01778 [nucl-th]: Magnetic field distribution in magnetars. Debarati Chatterjee, Jerome Novak (LUTH), Micaela Oertel (LUTH). (Submitted on 6 Aug 2018): ABSTRACT: Using an axisymmetric numerical code, we perform an extensive study of the magnetic field configurations in non-rotating neutron stars, varying the mass, magnetic field strength and the equation of state. We find that the monopolar (spherically symmetric) part of the norm of the magnetic field can be described by a single profile, that we fit by a simple eighth-order polynomial, as a function of the star's radius. This new generic profile applies remarkably well to all magnetized neutron star configurations built on hadronic equations of state. We then apply this profile to build magnetized neutron stars in spherical symmetry, using a modified Tolman-Oppenheimer-Volkov system of equations. This new formalism satisfactorily reproduces the correct behavior of the neutron star total mass with increasing magnetic field. Our " universal " magnetic field profile is intended to serve as a tool for nuclear physicists to obtain estimates of magnetic field inside neutron stars, as a function of radial depth, in order to deduce its influence on composition and related properties. It possesses the advantage of being based on magnetic field distributions from realistic self-consistent computations, which are solutions of Maxwell's equations. DETAILS:Using the simple virial theorem, one may estimate the maximum interior magnetic field to be as high as 10^18 G. If such large fields exist in the interior, they may strongly affect the energy of the charged particles by confining their motion to quantized Landau levels and consequently modify the particle population, transport properties as well as the global structure. The only case where a noticeable difference appears is when using quark matter EoS. Therefore, we make the following conjecture: the monopolar part of the norm of the magnetic field follows a universal profile, up to minor variations, when considering different neutron star models with realistic hadronic EoSs. This “universal” profile has been fitted using a simple polynomial: b0(x) = bc×(1 − 1.6x^2 − x^4 + 4.2x^6 − 2.4x^8), where x = ¯r/rmean is the ratio between the radius ¯ r in Schwarzschild coordinates and the star’s mean (or areal) radius. CONCLUSIONS: proposed a “universal” parameterization of the magnetic field profile, as a function of dimensionless stellar radius, obtained from a full numerical calculation of the magnetic field distribution. We tested this profile against several realistic hadronic EoSs, based on completely different analytic approaches, and with different magnetic field strengths in order to confirm its universality. For the case of quark matter EoSs, preliminary investigations showed that although MIT bag models conform to the universality, other quark matter EoSs may not necessarily do so. The profile is intended to serve as a tool for nuclear physicists for practical purposes, namely to obtain an estimate of the maximum field strength as a function of radial depth (within error bars), in order to deduce the composition and related properties. We applied the proposed magnetic field profile in a modified TOV-like system of equations, that include the contribution of magnetic field to the energy density and pressure, and account for the anisotropy by introducing a Lorentz force term. Compared with full numerical structure calculations, we find that qualitatively the correct tendency is reproduced and quantitatively the agreement is acceptable for large masses and small magnetic fields. Thus, although we encourage to employ the profile proposed here to conclude about the importance of magnetic field effects on matter properties, we can only recommend the use of a full axisymmetric numerical solution for modelling magnetized neutron
a. densities b. anisotropy c. stars d. EoS
Q107. arXiv:1808.01373 [physics.atom-ph]:Two-photon optical frequency reference with active ac Stark shift cancellation. V. Gerginov, K. Beloy. (Submitted on 3 Aug 2018): ABSTRACT: An optical reference based on a two-photon optical transition with ac Stark shift cancellation is proposed. The reference uses two interrogating laser fields at different frequencies. Compared to conventional optical two-photon references, the new approach offers the possibility for improved short-term stability resulting from a higher signal-to-noise and improved long-term stability due to active ac Stark shift cancellation. We demonstrate the ac Stark shift cancellation method on the 5s^2 S1/2→5d^2 D5/2 two-photon transition in 87Rb. DETAILS: The rubidium two-photon 5s^2 S1/2→5d^2 D5/2 optical transition at 778nm has been recommended as a secondary representation of the second and has been investigated as an optical frequency reference. The reference is of particular interest because of the relative simplicity of the setup, high atomic Q-factor, and the possibility of using telecommunication components at 1560nm for both excitation and frequency division down to the microwave domain by optical frequency combs. In summary, the two-colour scheme described in this work offers the possibility of building a rubidium frequency reference based on telecom components with the option of controlling the largest systematic uncertainty contributions to levels below 10^−13/√τ. Such a device would full-fill the growing need for optical frequency references that outperform their commercial microwave counterparts both short- and long-term, and can operate with relaxed environmental control requirements compared to optical references based on cold
a. atoms b. plasma c. excitations d. references
Q108. arXiv:1808.01495 [astro-ph.SR]: Luminosity constraint and entangled solar neutrino signals. Francesco Vissani. (Submitted on 4 Aug 2018): ABSTRACT: Now that neutrino propagation phenomena are understood, solar neutrino physics is entering an era when observational progresses indicate new challenges. The luminosity constraint plays a key role for current needs. We present it in a new form, improving the coefficients originally obtained by J. Bahcall, Phys. Rev. C 65 (2002) 025801. It turns out that the PP- and CNO-neutrino signals are entangled: In fact, pp-neutrinos can be extracted from the luminosity constraint only when CNO-neutrinos are quantified; the interpretation of the results of the gallium experiments depends upon both fluxes; a precise knowledge of pep-neutrinos is a precondition to extract the CNO-neutrino signal with Borexino. DETAILS:An accurate description of the Sun, provided us by the standard solar model (SSM), has been a crucial tool to proceed in our understanding since the beginning of solar neutrino science. The values of the main 8 fluxes of solar neutrinos are usually given as Φi = ϕi × 10^αi / cm^2.s where i = pp, Be, pep, B, hep, N, O, F; the identification index i runs over the 5 neutrinos of the PP-chain and the 3 neutrinos of the CNO-cycle; αi are fixed exponents and ϕi are adimensional coefficients. Discussion: After the clarification of the flavor transformation phenomena in solar neutrinos, great results have been obtained thanks to observational neutrino astronomy and new ones are expected. In particular, there is a chance of measuring for the first time a signal from CNO-neutrinos, after those seen from the PP-neutrinos, that correspond to the two main astrophysical mechanisms that fuel the stars. The measured solar luminosity, with minimal theoretical inputs, leads to the luminosity constraint, that is based on the assumptions that we understand sufficiently well nuclear physics and the Sun is in equilibrium. This is a precious tool to proceed further in the study of the Sun; we have discussed it thoroughly, proposing an improved description. We have shown that the luminosity constraint and several other facts imply that the PP and CNO-neutrino signals are entangled by the empirical need to extract both of them from solar neutrino observations. This point should be taken into account to plan future steps forward at best: It motivates further efforts to understand the gallium cross section, whose current large uncertainty limits our possibilities to exploit the existing very precise results. More in general, the existence of the entanglement between CNO- and PP-neutrino signals emphasizes even further the importance of measuring the CNO-neutrinos for the
Q114. trusciencetrutechnology@blogspot.com Volume 2018, Issue No.7c, Dated: 16 July, 2018. The Indian Science Congress Association 106th Physics Session to be held, January 3-7, 2019.
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 catalyse the interaction of salt water with the graviton, producing newer 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 newer photons of extraordinary properties. The novel operator
keep 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 physicists.
products of γµ , γν respectively in the first layer of the Earth, graviton becomes....... results in the two photons, that transform into compollnent form of electric and magnetic fields. The beauty of the theory is that it keeps the graviton as a single entity. The matrix (m11, m10, m1-1, m01, m00, m0-1, m-11 , m-10, m-1-1) of the nine fields goes with all the nine products of γµ , γν respectively.
Website : http://www.sciencecongress.nic.in
Submission of Papers for 106th ISC to respective sectional Presidents by 15th September 2018
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Q87. arXiv:1805.03447 [astro-ph.HE]: The necessity of including magnetic fields in simulating core collapse supernovae. Noam Soker (Technion, Israel): (Submitted on 9 May 2018): ABSTRACT: I find that an ingredient that was added in a recent study to facilitate the delayed neutrino explosion mechanism of core collapse supernovae, namely, large scale perturbations in the pre-collapse core, has a larger positive influence on the jittering jets explosion mechanism. By following the specific angular momentum of the accreted mass on to the newly born neutron star, I find that the accreted mass is likely to form intermittent accretion belts and disks, although they might lack axisymmetrical structure. These accretion belts and disks are likely to launch jets, but this can be simulated only if magnetic fields are included in the numerical code, as well as high numerical resolution that follows the rotation of the newly born neutron star and the shear in the accretion flow. I also discuss the possibility that the rotation of the pre-collapse core is important in increasing the shear in the accretion flow, hence the amplification of the magnetic fields. I repeat again my call for a paradigm shift from a neutrino-driven to a jet-driven explosion mechanism of massive stars. Such a paradigm shift will bring the recognition that to simulate core collapse supernovae one must use magneto-hydrodynamical numerical codes. SUMMARY: The main result of this study is that the angular momentum of the accreted mass in the simulation of Mu¨ller et al. who introduced perturbations in the pre-collapse core, can lead to the formation of intermittent accretion belts and disks around the newly born neutron star. However, to derive bipolar outflows, namely jets, from this accretion flow one must include magnetic fields in the simulations, as well as high resolution that enables to follows the shear between the down flows and the rotating neutron star. The magnetic fields are expected to be very strong. Firstly, the pre-collapse core is likely to amplify magnetic fields. Zilberman et al., concluded from their study of the rotational shear in pre-collapsing cores that even slowly rotating pre-collapse cores might amplify magnetic fields in the core, and after collapse in the zone above the newly born neutron star. Secondly, instabilities above the newly born neutron star can further amplify the magnetic field. Thirdly, the accretion disks and accretion belts substantially increase the magnetic field strength. I repeat again my call for a paradigm shift from a neutrino-driven to a jet-driven explosion mechanism of massive stars. Most CCSNe are exploded by jittering jets, but some are exploded by jets that maintain a fixed axis. In the present study this call is supported by the finding that an ingredient that was added to facilitate the delayed neutrino mechanism, namely, large scale perturbations in the pre-collapse core, has a larger positive influence on the jittering jets explosion
a. studies b. views c. jitters d. mechanism.
Q88. arXiv:1712.01153 [astro-ph.CO]: Gravitational clustering of cosmic relic neutrinos in the Milky Way. Jue Zhang, Xin Zhang. (Submitted on 4 Dec 2017 (v1), last revised 9 May 2018 (this version, v2)): ABSTRACT: The standard model of cosmology predicts the existence of cosmic neutrino background in the present Universe. To detect cosmic relic neutrinos in the vicinity of the Earth, it is necessary to evaluate the gravitational clustering effects on relic neutrinos in the Milky Way. Here we introduce a reweighting technique in the N-one-body simulation method, so that a single simulation can yield neutrino density profiles for different neutrino masses and phase space distributions. In light of current experimental results that favour small neutrino masses, the neutrino number density contrast around the Earth is found to be almost proportional to the square of neutrino mass. The density contrast-mass relation and the reweighting technique are useful for studying the phenomenology associated with the future detection of the cosmic neutrino background. DETAILS: In order to detect them in the neighbourhood of the Earth, a prerequisite would be to figure out the number density of relic neutrinos at our local environment. Although the standard model of cosmology does predict that the average number density of relic neutrinos in the current Universe is about 56 cm^−3 for each flavour, more relic neutrinos can be accreted around the Earth, due to the fact that massive neutrinos suffer from the gravitational potential of both dark matter (DM) and baryonic matter in the Milky Way (MW). Investigating the gravitational clustering of relic neutrinos is thus a necessary step towards interpreting the results from the future detection of cosmic neutrino background. CONCLUSIONS: In all the three physics scenarios considered in this work, the nature of Dirac neutrinos is assumed. Therefore, lepton number is conserved and thus only neutrinos, not anti-neutrinos, can be captured. Regarding the neutrino helicity states, in the early Universe both left-handed and right-handed chiral states are relativistic, and therefore they are left-handed and right-handed helical states as well. In the evolution of the Universe, the helicites of neutrinos are preserved, so that at the present time the left-handed and right-handed helical neutrino states correspond to the left-handed and right-handed chiral states in the early Universe, respectively. In Standard Case, the standard model of cosmology predicts the average number density of left-handed helical neutrino states to be n0 = 56 cm^−3 for each mass eigenstate at the present time, while almost no existence of right-handed helical states. For a given value of the total neutrino mass sum(mν), we can obtain the three individual neutrino masses with the two mass-squared differences from neutrino oscillation experiments. Here we adopt ∆m^221 ≡ (m2^2 − m1^2) = 7.56 × 10^−5 eV^2 and |∆m^231| ≡ |m3^2 −m1^2 | = 2.55×10^−3 eV^2. Taking neutrino mass sum(mν) = 0.23 eV as an example, we obtain (m1,m2,m3) = (0.0711 eV,0.0717 eV,0.087 eV) in NH. From the fitted function we find that the neutrino density contrasts δν are (0.22,0.23,0.35) for the three mass eigenstates, respectively, and therefore the corresponding number densities of left-handed helical states around the Earth are 68.44 cm^−3, 68.64 cm^−3 and 75.53 cm^−3. Finally, we obtain the capture rate Γ = 4.97 yr^−1 in this case. The calculation of capture rates in NP Case I and II can be performed similarly, except that in NP Case Iand II there are additional contributions from the right-handed helical states of neutrinos, whose average number densities at the present time are taken to be 0.28n0 and 0.52n0 for each mass eigenstate in NP Case I and II, respectively. Gravitational clustering effects on the right-handed helical states are calculated in the same way as the left-handed helical states, except that in NP Case II the fitted relation for the fully-degenerate phase space distribution should be
a. adopted b. used c. adopted d. curtailed
Q89. arXiv:1805.03753 [quant-ph]: Projecting onto any two-photon polarization state using linear optics. G. S. Thekkadath, L. Giner, X. Ma, J. Flórez, J. S. Lundeen. (Submitted on 9 May 2018): ABSTRACT: Projectors are a simple but powerful tool for manipulating and probing quantum systems. For instance, projecting two-qubit systems onto maximally entangled states can enable quantum teleportation. While such projectors have been extensively studied, partially-entangling measurements have been largely overlooked, especially experimentally, despite their important role in quantum foundations and quantum information. Here, we propose a way to project two polarized photons onto any state with a single experimental setup. Our scheme does not require optical non-linearities or additional photons. Instead, the entangling operation is provided by Hong-Ou-Mandel interference and post-selection. The efficiency of the scheme is between 50% and 100%, depending on the projector. We perform an experimental demonstration and reconstruct the operator describing our measurement using detector tomography. Finally, we flip the usual role of measurement and state in Hardy's test by performing a partially-entangling projector on separable states. The results verify the entangling nature of our measurement with six standard deviations of confidence. CONCLUSIONS: In summary, we proposed a straightforward way of projecting two polarized photons onto any state. Our scheme has an efficiency of at least 50% which far exceeds that of any scheme based on a probabilistic CNOT gate (11%). We performed an experimental demonstration and reconstructed the operator describing our measurement using detector tomography. Finally, we flipped the usual role of measurement and state in Hardy’s test and verified the entangling nature of our measurement. We anticipate that our scheme will find applications in quantum metrology and quantum information. In single-parameter estimation problems, entangling measurements cannot in general extract more information about that parameter than separable measurements. However, in multi-parameter problems such as state estimation or certain phase estimation scenarios, our scheme could be used to implement the partiallyor maximally-entangling projectors that optimize the amount of information extracted. Although limited to two qubits, such a measurement would be of foundational importance in quantum information as it saturates a fundamental limit in the amount of information that can be extracted from quantum systems. Finally, our scheme can also be used prepare any two-photon polarization state, uniquely without modifying the photon
a. axis b. state c. scheme d. source.
Q90. arXiv:1805.05341 [astro-ph.GA]: The Galactic Centre source G2 was unlikely born in any of the known massive binaries. Diego Calderón, Jorge Cuadra, Marc Schartmann, Andreas Burkert, Philipp Plewa, Frank Eisenhauer, Maryam Habibi. (Submitted on 14 May 2018). ABSTRACT:The source G2 has already completed its pericentre passage around Sgr A*, the super-massive black hole in the centre of our Galaxy. Although it has been monitored for 15 years, its astrophysical nature and origin still remain unknown. In this work, we aim to test the hypothesis of G2 being the result of a stellar wind collision. To do so, we study the motion and final fate of gas clumps formed as a result of collisions of stellar winds in massive binaries. Our approach is based on a test-particle model in order to describe the trajectories of such clumps. The model takes into account the gravitational field of Sgr A*, the interaction of the clumps with the interstellar medium as well as their finite lifetimes. Our analysis allows us to reject the hypothesis based on four arguments: i) if G2 has followed a purely Keplerian orbit since its formation, it cannot have been produced in any of the known massive binaries since their motions are not consistent; ii) in general, gas clumps are evaporated through thermal conduction on very short timescale (< 100yr) before getting close enough to Sgr A*; iii) IRS 16SW, the best candidate for the origin of G2, cannot generate clumps as massive as G2; and iv) clumps ejected from IRS 16SW describe trajectories significantly different to the observed motion of G2. DETAILS:Massive binaries orbiting Sgr A*. The inner parsec of our Galaxy hosts about 30 Wolf-Rayet stars. Photometric and spectroscopic studies have provided valuable information of their orbits and stellar winds. Years of monitoring allowed to identify three binary systems among this sample (Martins et al. 2006; Pfuhl et al. 2014). However, there are other four sources considered as binary candidates (see Pfuhl et al. 2014). Although some of them showed changes on either brightness or radial velocity, there are not enough observations to confirm their binarity. Furthermore, only two of them are within half a parsec from Sgr A*. The other two are at ∼ 1.5 pc, so latest surveys did not include them. Therefore, throughout this work we focus uniquely on systems already confirmed as binaries. CONCLUSIONS: Our analytical and test-particle simulation results show that we cannot reconcile the hypothesis of G2 being a gas clump formed in any known massive binary system with its observed motion. The results that support this conclusion are the following. (i) G2 orbital fit is not consistent with an origin in IRS 16SW. It is not possible to match IRS 16SW and G2 positions on the sky if we trace their orbits back in time. Their projected separation (lower limit of the physical separation) always remains larger than ∼ 0.2 arcsec. (ii) Cold gas clumps do not live long enough. The hot environment close to Sgr A* evaporates cold clumps very rapidly via thermal conduction. At the orbit of IRS 16SW, massive clump lifetimes and the free-fall timescale are comparable (∼ 200 yr). Therefore, only the most massive of them would live long enough to reach the vicinity of Sgr A*. (iii) IRS 16SW cannot produce massive enough clumps. Given its orbital and stellar wind parameters, we can expect it to create clumps with initial masses of at most 3 Earth masses. Roughly half of that mass would be lost before reaching Sgr A*, in disagreement with the observed G2 mass. (iv) Our test-particle simulations cannot reproduce G2 observations. A model based on IRS 16SW ejecting clumps along its orbit is not capable of producing any clump that matches the observed G2 positions on the sky and radial velocity measurements. These results, together with our previous work on encounters between single stars (Caldero´n et al. 2016), reject the idea of G2 being created in a stellar wind collision. However, our work does not rule out the “purely gaseous cloud” scenario in general. Other gas cloud models remain as possible explanations. In order to reject those, following a procedure similar to the one presented in this paper, it would be necessary to first identify candidate progenitors, e.g., a star recently going through a nova outburst, or being partially
a. disturbed b. disrupted c. destroyed d. condoned.
Q91. arXiv:1805.05365 [astro-ph.GA]: Metals and dust in the neutral ISM: the Galaxy, Magellanic Clouds, and damped Lyman-α absorbers. Annalisa De Cia. (Submitted on 14 May 2018). ABSTRACT: Context. The presence of dust in the neutral interstellar medium (ISM) dramatically changes the metal abundances that we measure. Understanding the metal content in the neutral ISM, and a direct comparison between different environments, has been hampered to date because of the degeneracy to the observed ISM abundances caused by the effects of metallicity, the presence of dust, and nucleosynthesis. Aims. We study the metal and dust content in the neutral ISM consistently in different environments, and assess the universality of recently discovered sequences of relative abundances. We also intend to assess the validity of [Zn/Fe] as a tracer of dust in the ISM. This has recently been cast into doubt based on observations of stellar abundances, and needs to be addressed before we can safely use it to study the ISM. Methods. In this letter we present a simple comparison of relative abundances observed in the neutral ISM in the Galaxy, the Magellanic Clouds, and damped Lyman-{\alpha} Absorbers (DLAs). The main novelty in this comparison is the inclusion of the Magellanic Clouds. Results. The same sequences of relative abundances are valid for the Galaxy, Magellanic Clouds, and DLAs. These sequences are driven by the presence of dust in the ISM and seem 'universal'. Conclusions. The metal and dust properties in the neutral ISM appear to follow a similar behaviour in different environments. This suggests that a dominant fraction of the dust budget is built up from grain growth in the ISM depending of the physical conditions and regardless of the star formation history of the system. In addition, the DLA gas behaves like the neutral ISM, at least from a chemical point of view. Finally, despite the deviations in [Zn/Fe] observed in stellar abundances, [Zn/Fe] is a robust dust tracer in the ISM of different environments, from the Galaxy to DLAs. DETAILS: The understanding of metal content in the neutral ISM and a direct comparison of different environments has been hampered for years by the degeneracy to the metal budget of the neutral ISM caused by the effects of metallicity, dust depletion, and nucleosynthesis. A leap forward was made by De Cia et al. (2016), who found empirical relations (sequences) between relative abundances observed in the ISM of the Galaxy and DLAs. This was used in turn to develop a new method for characterizing dust depletion in different environments. CONCLUSIONS: We conclude that the DLA gas mostly behaves like the neutral ISM, at least from a chemical point of view, and is unlikely to be associated with the CGM at large distances from the DLA galaxy. This strengthens the case for using DLAs as a complementary tool to study galaxies, out to high redshift and down to low masses. Finally, we demonstrate the validity of [Zn/Fe] as a robust dust tracer in the ISM of different environments, from the Galaxy to
a. Its centre b. other Galaxies c. DLA galaxy d. DLAs.
Q92. arXiv:1805.05577 [astro-ph.CO]: Axion dark matter and the 21-cm signal. .Pierre Sikivie. (Submitted on 15 May 2018): ABSTRACT: It was shown in ref. [1] that cold dark matter axions reach thermal contact with baryons, and therefore cool them, shortly after the axions thermalize among themselves and form a Bose-Einstein condensate. The recent observation by the EDGES collaboration of a baryon temperature at cosmic dawn lower than expected under "standard" assumptions is interpreted as new evidence that the dark matter is axions, at least in part. Baryon cooling by dark matter axions is found to be consistent with the observation of baryon acoustic oscillations. DETAILS: The observation of the trough in the spectrum of cosmic microwave radiation caused by its absorption by neutral hydrogen atoms [3] at cosmic dawn, i.e. when the universe is bathed in starlight for the first time. Assuming it is correct, the EDGES observation reveals new important information. It informs us that the first stars formed approximately 180 million years after the Big Bang and that the primeval gas was heated to above the photon temperature approximately 100 million years later. Most importantly for the present discussion, it tells us the spin temperature of hydrogen atoms during this 100 million year epoch. The spin temperature Ts is, by definition, related to the relative population of the spin 1 and spin 0 lowest energy states of hydrogen: n1 n0 ≡ 3 × e−ω0/Ts where ω0 = (2π) 1.42 GHz is the angular frequency associated with hyperfine splitting in hydrogen, the so-called 21 cm line. We use units in which ¯ h = c = kB throughout. The spin temperature is intermediate between the baryon kinetic temperature Tk and the photon temperature Tγ (Tk ≤ Ts ≤ Tγ) being driven toward Tγ by 21 cm emission and absorption but driven towards Tk by atomic collisions and by Lyman-alpha emission and absorption. CONCLUSIONS: This fairly large value suggests that absorption of 21 cm radiation, which drives Ts up, may compete with the Wouthuysen-Field effect driving it down. In that case the absorption would saturate before Ts reaches Tk. Whether baryon cooling by dark matter axions agrees with all observations remains to be seen. Eq. (2) allows predictions to be made. One concern is whether the drag on baryons dampens baryon acoustic oscillations. The damping of baryon acoustic oscillations by WIMP dark matter has been considered in refs. [25] and constraints on the scattering cross-section between WIMPs and baryons have been derived on this basis. Using Eq. (3), the fraction of energy removed from the baryon-photon fluid per Hubble time shortly before recombination is found to be of order 3·10−5 Y ℓ/t, which seems safely
a. big b. small c. oscillatory d. Intermediate.
Q93. arXiv:1805.05642 [astro-ph.HE]: Gamma-Ray Astrophysics. Alessandro De Angelis, Manuela Mallamaci. (Submitted on 15 May 2018). ABSTRACT: High-energy photons are a powerful probe for astrophysics and for fundamental physics in extreme conditions. During the recent years, our knowledge of the most violent phenomena in the Universe has impressively progressed thanks to the advent of new detectors for gamma rays, both at ground and on satellites. This article reviews the present status of high-energy gamma-ray astrophysics, with emphasis on the recent results and a look to the future. DETAILS: We will focus on the most energetic photons, indicated as gamma rays. In general, the term denotes the electromagnetic radiation above some 100keV, but we will dedicate the discussion especially to gamma rays in the high energy (between a few MeV and ∼ 30 GeV) and very high energy (& 30 GeV) regions. There is little doubt on the existence of photons in the PeV-EeV range, but so far cosmic gamma rays have been unambiguously detected in high energy and very high energy domains, the most energetic reaching ∼ 100TeV. During the recent years, a large amount of sources has been detected, revealing the existence of a very heterogeneous population that lights up the gamma-ray sky, in our Galaxy and beyond. Understanding and modelling the gamma-ray emission are compelling aspects per se, but have also other facets. Gamma rays are indeed intimately related to all cosmic messengers: charged cosmic rays, neutrinos and gravitational waves. Besides, they are an indirect probe for questions related to fundamental physics. This was decisive for obtaining the first successful localization of the first gamma ray emitter: the Crab Nebula was detected above 0.7TeV in 1989 by the Whipple collaboration, 37 years after the initial Cherenkov light pulse observation. Given a primary photon of 100 GeV, about 10 Cherenkov photons per square meter arrive at the level of mountain altitudes around 2000 m above sea level (a.s.l.). A collection area of 100 m2 is therefore sufficient to detect gamma ray showers. Since the Cherenkov light is faint, clear and almost dark nights are required for observations. As a consequence, this kind of instruments are characterized by a low duty cycle of about 15%. In addition, they have a small FoV ( . 5◦), but a high sensitivity and a low energy threshold. FUTURE DIRECTIONS: The current generation of detectors, both in space and on ground, is providing a wealth of information about the non-thermal Universe in the GeV-TeV energy band, as highlighted in the previous sections. However a key piece is missing: the MeV energy range. This scarcely explored domain is important since it is characteristic of nuclear transitions and of the nuclear de-excitation of molecular clouds excited by colliding CRs; in addition, it is the energy range where one expects the exhaustion of the electromagnetic counterpart of gravitational wave events and where one expects gamma rays from the conversion of axions in the core of
a. supernovae b. CRs c. domains d. localizations.
Q94. arXiv:1805.06394 [gr-qc]: Quantum Gravity phenomenology and metric formalism. Niccoló Loret, Leonardo Barcaroli, Giulia Gubitosi. (Submitted on 16 May 2018). ABSTRACT: n this proceedings for the MG14 conference, we discuss the construction of a phenomenology of Planck-scale effects in curved space-times, underline a few open issues and describe some perspectives for the future of this research line. DETAILS: Even if in this formalism the Casimir and world-lines are invariant under some generalised boost transformations, it is not clear whether this is the case also for the momentum space and the space-time line element (dsHℓ)^2 , which are derived from the metric. In fact, since the metric is now explicitly (x, ˙x)-dependent, it may be not possible anymore to obtain a formalization of the invariant line-elements in terms of the coordinates differentials. This may not be a problem, since line-element and metric are not something we observe, but just useful tools we infer from particles’ dynamics. At the same time metric formalism is fundamental in many aspects of General Relativity and we would like to preserve it also in it’s deformed version that we may want to formulate one day. CONCLUSIONS: The situation we described in this proceedings shows some results achieved and many open issues to solve for what concerns the use of metrics to formalise space-time-symmetries deformation models. The road ahead presents many choices. We could focus in understanding under which assumptions can we inject all this model deformation just in one geometric object, leaving unchanged the remaining relativistic structure of he theory. In this sense, tetradic formalism has proved to be very fruitful, but at the same time how can we build a relativistic framework on the invariant line-element if at the end this one would not result a reliable landmark? A drastic solution to this problem could be to renounce to rely on metric formalism and investigate on Finsler geometry, as a way to formalise Planck-scale deformed relativistic symmetries, as an alternative to the implementation of those deformations directly on Riemannian geometry, since we don’t know yet if such an approach would or would not work. Another approach could be to build from scratch a theory which takes into account a complete scenario of curved phase-space, building a metric formalism from phase space
a. formalism b. discrete c. symmetries d. considerations
Q95. arXiv:1803.04973 [hep-th]: Quantum-first gravity. Steven B. Giddings. (Submitted on 13 Mar 2018 (v1), last revised 16 May 2018 (this version, v2)): ABSTRACT: This paper elaborates on an intrinsically quantum approach to gravity, which begins with a general framework for quantum mechanics and then seeks to identify additional mathematical structure on Hilbert space that is responsible for gravity and other phenomena. A key principle in this approach is that of correspondence: this structure should reproduce space-time, general relativity, and quantum field theory in a limit of weak gravitational fields. A central question is that of "Einstein separability," and asks how to define mutually independent subsystems, e.g. through localization. Familiar definitions involving tensor products or operator sub-algebras do not clearly accomplish this in gravity, as is seen in the correspondence limit. Instead, gravitational behaviour, particularly gauge invariance, suggests a network of Hilbert subspaces related via inclusion maps, contrasting with other approaches based on tensor-factorized Hilbert spaces. Any such localization structure is also expected to place strong constraints on evolution, which are also supplemented by the constraint of unitarity. CONCLUSIONS: In order to respect quantum mechanics, the evolution law must be unitary , e.g. yielding a unitary S-matrix in the context of states corresponding to asymptotically flat boundary conditions. Given the challenges of describing unitary quantum black hole (BH) evolution, this appears to be an important constraint. As a reminder, in an approximate description of black holes, the Hilbert space factorizes as HBH⊗Henv --> (4.1) corresponding to states of the BH and environment. Then, if the Hamiltonian does not allow transfer of information from HBH to Henv, and if HBH disappears as the black hole evaporates, as LQFT appears to indicate, unitarity is violated. This paper has reviewed arguments that a factorization (4.1) is not quite correct when one accounts for properties of gravity. However, subsystem structure that replaces (4.1) has also been described. An important question is whether the gravitational modifications to (4.1) that we have found are sufficient to resolve the unitarity problem – if nonlocality of quantized GR resolves the unitarity crises, we may see it perturbatively here. For example, while it has been noted that the leading-order description of standard dressing appears to rule out the suggested, role of soft quantum hair, it may be that a different higher-order effect leads to information about the internal state of a BH being accessible from outside. While this remains to be explored more completely, we have not seen an indication that the modifications to (4.1) are sufficient to restore unitarity. If perturbative modifications to subsystem structure, i.e. localization, in gravity do not directly resolve the unitarity problem, it appears that this provides an additional important clue about the nature of evolution – plausibly the existence of additional couplings between subsystems that go beyond quantized GR. The approach to modeling unitary evolution of BHs that has been proposed in, has been to parameterize such couplings, of a form that doesn’t violate our correspondence constraints. If this is the case, the necessity of consistent quantum evolution of BHs is providing us significant additional information about the non-perturbative structure of the
a Theory b. formalism c. evolution d. phenomenology.
Q96.arXiv:1805.02240 [gr-qc]: Graviton Mass and Memory. Ercan Kilicarslan, Bayram Tekin. (Submitted on 6 May 2018 (v1), last revised 16 May 2018 (this version, v2)). ABSTRACT: Gravitational memory (a residual change) arises after a finite gravitational wave pulse interacts with free masses. We calculate the memory effect for particle scattering in massive gravity as a function of graviton mass mg) and show that it is discretely different from the result of general relativity: the memory is reduced not just via the usual expected Yukawa decay but by a numerical factor which survives even in the massless limit. For mg ≤ 10^−29eV , the memory is significantly reduced for distances beyond 1Mpc as in the first observation of two black hole mergers which was at a distance of more than 200Mpc. Hence careful observations of the gravitational wave memory effect can rule out the graviton mass. We also show that adding higher curvature terms reduces the memory effect. DETAILS: All the effects of gravity are encoded in the metric tensor field g which needs no coordinates to be defined. General Relativity (GR) is intrinsically four dimensional and the full metric of space-time manifold g does not really evolve in time: it is what it is. So, if we had known how to obtain all the local observables from the metric for all physically relevant situations, we would not need any further nomenclatures such as memory effect, gravito-magnetism etc. But, since as local observers, we do not have full access to the fully consistent space-time, it pays to see space-time as space evolving in time, namely, to see space-time as a history of space. Such a dynamical picture requires a choice of time and other coordinates and leads to interesting phenomena and the gravitational memory is one such an event: the wave that enters the interaction with the detector masses differs in some well-defined sense from the wave that leaves the interaction. The best way to see the difference is to measure the change in the relative separation of the masses as this is related to the change in the wave profile. CONCLUSIONS: Recently gravitational memory effect received a renewed interest for general relativity with or without a cosmological constant, for various reasons some of which are: its related to black hole soft hair, asymptotic symmetries and its potential observation in the gravitational wave detectors. Here, we calculated the gravitational memory as a function of graviton mass and showed that for the strongest existing bounds on graviton mass, the memory is essentially wiped out for the sources located at distances above
a. 5Mpc b. 40Mpc c. 10Mpc d. 20Mpc
Q97.arXiv:1805.05875 [astro-ph.HE]: Low-energy electrons in GRB afterglow models. Guðlaugur Jóhannesson, Gunnlaugur Björnsson. (Submitted on 14 May 2018). ABSTRACT: Observations of gamma-ray burst (GRB) afterglows have long provided the most detailed information about the origin of this spectacular phenomena. The model that is most commonly used to extract physical properties of the event from the observations is the relativistic fireball model, where ejected material moving at relativistic speeds creates a shock wave when it interacts with the surrounding medium. Electrons are accelerated in the shock wave, generating the observed synchrotron emission through interactions with the magnetic field in the downstream medium. It is usually assumed that the accelerated electrons follow a simple power-law distribution in energy between specific energy boundaries and that no electron exists outside these boundaries. This work explores the consequences of adding a low-energy power-law segment to the electron distribution whose energy contributes insignificantly to the total energy budget of the distribution. The low-energy electrons have a significant impact on the radio emission, providing synchrotron absorption and emission at these long wavelengths. Shorter wavelengths are affected through the normalization of the distribution. The new model is used to analyze the light curves of GRB 990510 and the resulting parameters compared to a model without the extra electrons. The quality of the fit and the best fit parameters are significantly affected by the additional model component. The new component is in one case found to strongly affect the X-ray light curves showing how changes to the model at radio frequencies can affect light curves at other frequencies through changes in best fit model parameters. DETAILS: Gamma-ray bursts (GRBs) are the most powerful explosions in the Universe and can therefore be observed to very high redshift. They have been hypothesised to be tracers of star formation and thus be a probe of the star formation history of the early universe. CONCLUSIONS: The results of the analysis of GRB 990510 and the statistical preference for the additional electron component lend support to the need for more detailed treatment of the electron distribution in GRB afterglow modeling. This can in particular affect the determination of the energetics of the outflow and the density structure of the external medium. The power-law segment added in this work is just a simple modification of the electron energy distribution to explore its effects and further work is needed to get a more accurate physical picture. One such method is to simultaneously solve for the dynamics of the afterglow and the distribution of electrons. This was done in the work of (Geng et al. 2018) but their approach is limited to electron cooling and lacks the thermalization effect of the electrons that may be important for the lowest energy electrons. They also excluded several important effects, such as the EATS. Clearly, thereis room for considerable improvements in this area of GRB afterglow
a. modelling b. scenario c. stastics d. incidence.
Q98.arXiv:1805.04123 [astro-ph.HE]: Pulsar magnetospheres in General Relativity. Federico Carrasco, Carlos Palenzuela, Oscar Reula. (Submitted on 10 May 2018). ABSTRACT: The main contribution to the pulsar power can be calculated by assuming a rotating magnetically-dominated magnetosphere described by the force-free approximation. Although this simple model has been used thoroughly to study pulsar magnetospheres in the flat spacetime regime, only few works have considered the relativistic corrections introduced by the curvature and frame-dragging effects induced by a rotating neutron star. Here we revisit the problem and describe pulsar magnetospheres within full General Relativity, quantifying the corrections as a function of the angular velocity, the compactness of the star and the misalignment angle between the spin and the magnetic dipole. We provide analytical expressions for the pulsar luminosity by fitting our numerical results. Finally, we also analyze the effect of the relativistic corrections on the braking index, which indicates a slight increment in its value. DETAILS: Pulsars are bright sources of electromagnetic radiation, emitting from radio to gamma-ray frequencies. Even though the main picture –consisting on a rotating magnetized neutron star– is rather simple, a full solution that explain the diverse observational phenomenology still remains elusive due to the extreme conditions found on neutron stars. With typical radius R = 10−13km and stellar masses between M ≈ 1.2−2.0Msun they are very compact astrophysical objects, only exceeded by black holes. Moreover, their rotation periods ranges from seconds to millisecond, and their surface magnetic field intensities, inferred by timing properties, vary from ∼ 10^8 to ∼ 10^15G.CONCLUSIONS: We have presented a formalism and a numerical code to carefully analyze the force-free magnetospheres of neutron stars, by extending previous studies on black hole magnetospheres. We have performed several tests to 10 There are many caveats regarding coherent timing analysis that difficult the comparison: possible occurrence of unseen glitches, shape of the residuals, choice of integration time, among others. show the correct implementation of the boundary conditions at the stellar surface, which is the main difference with respect to the previous code. A careful and detailed decomposition of the eigenvectors of the evolution equations is required to apply suitable inner boundary conditions of our domain, which corresponds to a perfectly conducting neutron star. We have studied, through three-dimensional timedependent numerical simulations, general-relativistic neutron star magnetosphere within the force-free approximation. Our results confirm other recent numerical investigations, in particular regarding the total electromagnetic power radiated by the neutron star. By performing suitable fits of our results, we provide a quite generic formula for the luminosity of a rotating dipolar magnetic field as a function of the compactness of the neutron star, its angular velocity, and the misalignment angle between the spin and the magnetic dipolar moment. From this formula, we have estimated deviations from the standard braking index value which will generally depend on these adimensional parameters. These deviations are rather modest, leading to n = 3.2 ± 0.2 for realistic millisecond pulsars. Unfortunately, current astrophysical observations are not accurate enough to distinguish such small differences on the braking index. Even for the pulsars displaying an almost constant braking index which could be measured with high precision, the observed values are systematically below the standard n = 3. As it has been confirmed in this work, these deviations can not be associated to relativistic effects. Therefore, we can only conclude that, if the measurements are correct, there must be other physical mechanisms modifying the luminosity of a pulsar magnetosphere which are not captured by the simple force-free
a. structure b. moment c. formula d. model
a. structure b. moment c. formula d. model
Q99.arXiv:1805.06592 [physics.optics]: Ghost Diffraction in Time Domain: Two-Photon Reciprocal Two-Slit Diffraction-Interference. Yoshiki O-oka and Susumu Fukatsu, Tokyo 153-8902, Japan. ABSTRACT: Temporal ghost diffraction (TGD) is observed by taking two-photon cross-correlation in the configuration of reciprocal two-slit diffraction (2SD) where interference fringes develop on the light source side as opposed to the detector side. To this end, a narrow-band chaotic light source and a gated detector are used in the frequency-time domain, which emulate a randomly pointing incoherent light source and a stationary pinhole detector in the momentum-space domain, respectively. Spectral fringes with visibility that closely follows a sinc function of spectral bandwidth are clear evidence that legitimate TGD fringes due to two-photon interference develop even with classical light. DETAILS: Photon correlation has been the target of continued scientific interest for decades from not only the fundamental but application points of view in the context of quantum physics and quantum information processing. RESULTS: The detector is a photon-counting device with 25×25µm2 aperture. Apparently, a close match is found between the solid line (red) and the interference fringes due to normal 2SD shown by the dotted line (black). This has the following implications. First of all, the pinhole detector is now given the role of the hypothetical light source, which explains why it must be point-like. Second, which-path information must be erased on both sides of the slit for interferences to occur. Last but significant, device functions do not count, so ”source” and ”detector” are interchangeable. Thus one can design a two-photon reciprocal 2SD setup with two
a. sources b. apertures c. detectors d. processors.
Q100. arXiv:1806.02687 [astro-ph.GA]: Evidence for the existence of abundant intracluster light at z= 1.24, Jongwan Ko, M. James Jee, (Submitted on 7 Jun 2018), ABSTRACT: Intracluster stars are believed to be unbound from their progenitor galaxies and diffused throughout the galaxy cluster, creating intracluster light (ICL). However, when and how these stars form are still in debate. To directly constrain the origin, one powerful method is to study clusters at the epoch when mature galaxy clusters began to appear. We report measurements of the spatial distribution, color, and quantity of diffuse intracluster stars for a massive galaxy cluster at a redshift of 1.24. This is the most distant galaxy cluster to date for which those three properties of the ICL have been quantified simultaneously. Our detection of the significant ICL fraction in this unprecedentedly high redshift regime strongly indicates that intracluster stars, contrary to most previous studies, might have formed during a short period and early in the history of the Virgo-like massive cluster formation and might be concurrent with the formation of the brightest cluster galaxy. DETAILS:Not all stars in the universe are gravitationally bound to galaxies. Since first discovered in 1951 (Zwicky 1951), observations have clearly revealed that a significant stellar component fills the space between galaxies in nearby galaxy clusters CONCLUSIONS:We have presented the ICL study of MOO J1014+0038 at z = 1.24. This is the highest-redshift cluster to date, for which we measure the two-dimensional distribution, as well as the radial color profile. The high-quality HST/WFC3 near-IR imaging data enables us to reach a very low surface brightness threshold (∼29 mag arcsec−2) and obtain a clear two-dimensional ICL map out to ∼200 kpc from the cluster BCG. We find that the ICL color is consistent with that of the bright, red cluster galaxies. However, unlike the radial color variation of galaxies, we do not detect any significant radial dependence of the ICL color. Using simple stellar population synthesis with an exponentially decaying star formation model, we estimate that the ICL stars had formed at z ∼ 2 or earlier. When estimating the ICL fraction, we take into account the contributions from the pixels outside our masking regions and from undetected faint, diffuse galaxies. In our most conservative case, the unmasked pixels contribute as much as ∼80% of the total diffuse light within r = 200 kpc. It is remarkable that despite this conservative analysis, the integrated ICL fraction still exceeds ∼10% of the total cluster light at r < 200 kpc, comparable to measurements in low-redshift clusters. Currently, two dominant physical mechanisms have been proposed to explain the formation of ICL: tidal stripping of the outskirts of infalling/satellite galaxies (e.g., Contini et al. 2014; Cooper et al. 2015) and violent mergers of cluster members during the formation of the BCG (e.g., Murante et al. 2007; Conroy et al. 2007). Both mechanisms may be at work. However, the dominance may be a function of time during the hierarchical growth of the cluster. The time difference between the cluster redshift (z = 1.24) and the formation epoch z = 2 (3) is ∼1.7 (2.8) Gyrs, during which the cluster galaxies can traverse the cluster only once or twice (assuming a free fall time for a massive cluster with a radius of ∼1 Mpc and a velocity dispersion of ∼1000km s−1). Thus, if the ICL formation is an ongoing process and predominated by the stripping of the outskirts of infalling/satellite galaxies, we should be able to observe the evolution of ICL fraction between z = 0 and 1. However, the presence of the significant ICL fraction at z = 1.24 strongly supports the paradigm that the dominant process for the ICL production is linked to the BCG formation, although we need to perform further analysis on more galaxy clusters at z > 1 to confirm that the cluster sample studied here is not
a. fruitful b.exceptional c. exclusive d. rudimentary.
Q101.arXiv:1805.02016 [hep-ph]: Black Hole Spin Constraints on the Mass Spectrum and Number of Axion-like Fields; Matthew J. Stott, David J. E. Marsh; (Submitted on 5 May 2018 (v1), last revised 7 Jun 2018 (this version, v2)); ABSTRACT: Astrophysical observations of spinning BHs, which span 5 M⊙ ≲ M BH≲ 5×10^8M⊙, can be used to exclude the existence of certain massive bosons via the superradiance phenomenon. In this work, we explore for the first time how these measurements can be used to constrain properties of statistical distributions for the masses of multiple bosonic fields. Quite generally, our methodology excludes Nax ≳ 30 scalar fields with a range of mass distribution widths and central values spanning many orders of magnitude. We demonstrate this for the specific example of axions in string theory and M-theory, where the mass distributions in certain cases take universal forms. We place upper bounds on Nax for certain scenarios of interest realised approximately as mass distributions in M-theory, including the QCD axion, grand unified theories, and fuzzy dark matter. CONCLUSIONS: We have studied this possibility, and used BH superradiance to exclude certain distributions of axion masses. The constraints become more severe with larger numbers of axion-like fields due to the increased probability of drawing an outlier. This allows us to place constraints on the number of axion-like fields, Nax. Models for axions coming from string theory and M-theory typically involve many axion-like fields. These fields have their masses determined by microscopic quantities related to the geometry of the compact space. Their masses, however, are expected to follow particular statistical distributions independently of the microscopic details. We have considered various different distributions, log-flat, log-normal, and Marčhenko-Pastur, using BH superradiance to bound both the parameters of the distribution, and, more significantly, the number of light axions within that distribution. Constraints on Nax from a process such as BH superradiance, which relies only on the existence of the vacuum fluctuations of the given field, are extremely powerful, and could be used in this context to bound the dimensionality of phenomenologically consistent moduli spaces in string/M-theory. Indeed we have seen that the benchmark value of Nax ≈ 30 found in the majority of known Calabi-Yau manifolds can be excluded for a wide range of distribution parameters. Only a small number of fields should obtain masses anywhere in the BH superradiance region from 10^−10 eV <= µax <= 10^−20 eV, which can be accommodated with a single very wide distribution σ >~ 30, or bimodal distributions containing only very light or relatively heavy axions. Our analysis has neglected axion self-interactions, which shut off BH superradiance if they are strong, and other constraints, for example coming from the relic abundance. It would be interesting in this regard to combine our previous analysis, with the current analysis and compute, in addition to axion masses, the axion decay constants, relic density, and self-interaction potential. The present work is more model-independent, since it does not rely on any cosmological assumptions, and applies to any model for light scalars with sufficiently small a. sources b. apertures c. detectors d. processors.
Q100. arXiv:1806.02687 [astro-ph.GA]: Evidence for the existence of abundant intracluster light at z= 1.24, Jongwan Ko, M. James Jee, (Submitted on 7 Jun 2018), ABSTRACT: Intracluster stars are believed to be unbound from their progenitor galaxies and diffused throughout the galaxy cluster, creating intracluster light (ICL). However, when and how these stars form are still in debate. To directly constrain the origin, one powerful method is to study clusters at the epoch when mature galaxy clusters began to appear. We report measurements of the spatial distribution, color, and quantity of diffuse intracluster stars for a massive galaxy cluster at a redshift of 1.24. This is the most distant galaxy cluster to date for which those three properties of the ICL have been quantified simultaneously. Our detection of the significant ICL fraction in this unprecedentedly high redshift regime strongly indicates that intracluster stars, contrary to most previous studies, might have formed during a short period and early in the history of the Virgo-like massive cluster formation and might be concurrent with the formation of the brightest cluster galaxy. DETAILS:Not all stars in the universe are gravitationally bound to galaxies. Since first discovered in 1951 (Zwicky 1951), observations have clearly revealed that a significant stellar component fills the space between galaxies in nearby galaxy clusters CONCLUSIONS:We have presented the ICL study of MOO J1014+0038 at z = 1.24. This is the highest-redshift cluster to date, for which we measure the two-dimensional distribution, as well as the radial color profile. The high-quality HST/WFC3 near-IR imaging data enables us to reach a very low surface brightness threshold (∼29 mag arcsec−2) and obtain a clear two-dimensional ICL map out to ∼200 kpc from the cluster BCG. We find that the ICL color is consistent with that of the bright, red cluster galaxies. However, unlike the radial color variation of galaxies, we do not detect any significant radial dependence of the ICL color. Using simple stellar population synthesis with an exponentially decaying star formation model, we estimate that the ICL stars had formed at z ∼ 2 or earlier. When estimating the ICL fraction, we take into account the contributions from the pixels outside our masking regions and from undetected faint, diffuse galaxies. In our most conservative case, the unmasked pixels contribute as much as ∼80% of the total diffuse light within r = 200 kpc. It is remarkable that despite this conservative analysis, the integrated ICL fraction still exceeds ∼10% of the total cluster light at r < 200 kpc, comparable to measurements in low-redshift clusters. Currently, two dominant physical mechanisms have been proposed to explain the formation of ICL: tidal stripping of the outskirts of infalling/satellite galaxies (e.g., Contini et al. 2014; Cooper et al. 2015) and violent mergers of cluster members during the formation of the BCG (e.g., Murante et al. 2007; Conroy et al. 2007). Both mechanisms may be at work. However, the dominance may be a function of time during the hierarchical growth of the cluster. The time difference between the cluster redshift (z = 1.24) and the formation epoch z = 2 (3) is ∼1.7 (2.8) Gyrs, during which the cluster galaxies can traverse the cluster only once or twice (assuming a free fall time for a massive cluster with a radius of ∼1 Mpc and a velocity dispersion of ∼1000km s−1). Thus, if the ICL formation is an ongoing process and predominated by the stripping of the outskirts of infalling/satellite galaxies, we should be able to observe the evolution of ICL fraction between z = 0 and 1. However, the presence of the significant ICL fraction at z = 1.24 strongly supports the paradigm that the dominant process for the ICL production is linked to the BCG formation, although we need to perform further analysis on more galaxy clusters at z > 1 to confirm that the cluster sample studied here is not
a. fruitful b.exceptional c. exclusive d. rudimentary.
a. self-interactions b. interactions c. large interactions d. oscillations.
Q102. arXiv:1806.10617 [astro-ph.HE]27 Jun 2018: Pulsar Astrophysics - The Next 50 Years Proceedings IAU Symposium No. 337, 2017 P. Weltevrede, B.B.P. Perera, L. Levin Preston & S. Sanidas. Pulsar observations at millimetre wavelengths., Spain email: torne@iram.es Abstract. Detecting and studying pulsars above a few GHz in the radio band is challenging due to the typical faintness of pulsar radio emission, their steep spectra, and the lack of observatories with sufficient sensitivity operating at high frequency ranges. Despite the difficulty, the observations of pulsars at high radio frequencies are valuable because they can help us to understand the radio emission process, complete a census of the Galactic pulsar population, and possibly discover the elusive population in the Galactic Centre, where low-frequency observations have problems due to the strong scattering. During the decades of the 1990s and 2000s, the availability of sensitive instrumentation allowed for the detection of a small sample of pulsars above 10GHz, and for the first time in the millimetre band. Recently, new attempts between 3 and 1mm (≈86−300GHz) have resulted in the detections of a pulsar and a magnetar up to the highest radio frequencies to date, reaching 291GHz (1.03mm). The efforts continue, and the advent of new or upgraded millimetre facilities like the IRAM 30-m, NOEMA, the LMT, and ALMA, warrants a new era of high-sensitivity millimetre pulsar astronomy in the upcoming years. DETAILS: One particular region where high-frequency surveys can be very useful is the centre of the Milky Way. Pulsars found in the Galactic Centre can help us to understand its enigmatic star formation history using their characteristics ages, map the gravitational potential using the pulsars as accelerometers, measure the gas properties and distribution and estimate the magnetic field through Faraday rotation effects. In addition, it is remarkable that one single pulsar in a suitable orbit around the supermassive black hole SgrA* would suffice to enable unprecedented black hole physics experiments and tests of General Relativity and alternative Gravity theories Summary The observations of pulsars at millimetre wavelengths are challenging, but provide unique insights into the pulsar emission properties, offer a way to probe dense ISM and find new pulsars and magnetars, and are a potential tool for precision black hole physics in the case that scattering prevents the detection of pulsars orbiting SgrA* at low frequencies. For this reason, we should continue the efforts to enable sensitive pulsar observations up to the highest possible frequencies. At the moment, at millimetre wavelengths the observations are concentrated at the IRAM 30-m radio telescope. In the future, larger facilities like NOEMA or the LMT have the potential to extend the sample of detectable pulsars between 3 and 0.8mm. Finally, a key facility will be ALMA, not only because it is the most sensitive (sub)millimetre telescope, but also because it is located in the southern hemisphere. Around 70% of all known pulsars have declination lower than zero degrees, and many of them are out of the visibility of the northern facilities. Therefore, the future observations with ALMA will offer the best chance to expand our comprehension of the pulsar emission physics, and have the potential to detect pulsars hidden at the Galactic Centre and other extreme-scattering
a. data b. regions c. amplitudes d. frequencies
Q103. arXiv:1806.10879 [astro-ph.HE]: Cosmogenic photon and neutrino fluxes in the Auger era, Rafael Alves Batista, Rogerio M. de Almeida, Bruno Lago, Kumiko Kotera. 28 Jun 2018/ ABSTRACT: The interaction of ultra-high-energy cosmic rays (UHECRs) with pervasive photon fields generates associated cosmogenic fluxes of neutrinos and photons due to photohadronic and photonuclear processes taking place in the intergalactic medium. We perform a fit of the UHECR spectrum and composition measured by the Pierre Auger Observatory for four source emissivity scenarios: power-law redshift dependence with one free parameter, active galactic nuclei, gamma-ray bursts, and star formation history. We show that negative source emissivity evolution is favoured if we treat the source evolution as a free parameter. In all cases, the best fit is obtained for relatively hard spectral indices and low maximal rigidities, for compositions at injection dominated by intermediate nuclei (nitrogen and silicon groups). In light of these results, we calculate the associated fluxes of neutrinos and photons. Finally, we discuss the prospects for the future generation of high-energy neutrino and gamma-ray observatories to constrain the sources of UHECRs. DETAILS: Ultra-high-energy cosmic rays (UHECRs) are particles, mostly atomic nuclei, with energies E >= 1 EeV (1 EeV ≡ 10^18 eV). Neither their origins nor the mechanisms whereby they are accelerated to such high energies have been unveiled. It is widely believed that UHECRs have extragalactic origin. Thus, they can interact with the intergalactic medium including photon fields such as the cosmic microwave background (CMB) and the extragalactic background light (EBL). Magnetic fields, too, play an important role in UHECR propagation. Because their distribution in the Universe is not well understood, the prospects for ultra-high-energy cosmic-ray astronomy are unclear. SUMMARY: Our study demonstrates that the detection of cosmogenic neutrinos is virtually guaranteed, even in the most pessimistic scenarios, provided that the projected instruments reach their expected sensitivities and that they operate for over a decade. From a different perspective, low cosmogenic fluxes as derived in the (1 + z)m scenario could be profitable for EeV neutrino astronomy. Such a scenario would imply that the neutrinos that would be detected first by future experiments would likely be those produced directly at the sources, via interactions of UHECRs with photon and baryon fields in the source environment. Abundant interactions should happen at the acceleration site of UHECRs, and theoretical models predict fluxes that are much higher than the level of cosmogenic neutrinos estimated there. In that case, it is advantageous that the cosmogenic neutrinos would constitute a low-level background, easing the identification of the first UHE neutrino point
a. views b. data c. scenario d. sources
Q104. arXiv:1807.08034 [astro-ph.HE]. Two novel approaches to the hadron-quark mixed phase in compact stars. Vahagn Abgaryan, David Alvarez-Castillo, Alexander Ayriyan, David Blaschke, Hovik Grigorian. (Submitted on 20 Jul 2018): ABSTRACT: First-order phase transitions, like the liquid-gas transition, proceed via formation of structures such as bubbles and droplets. In strongly interacting compact star matter, at the crust-core transition, but also at the hadron-quark transition in the core, these structures form different shapes dubbed "pasta phases". We describe two methods to obtain one-parameter families of hybrid equations of state (EoS) which mimic the thermodynamic behavior of pasta phases in between a low-density hadron and a high-density quark matter phase, thus generalizing the Maxwell construction. The first method replaces the behavior of pressure vs. chemical potential in a finite region around the critical %chemical potential pressure of the Maxwell construction by a polynomial interpolation. The second method uses extrapolations of the hadronic and quark matter EoS beyond the Maxwell point to define a mixing of both with weight functions bounded by finite limits around the Maxwell point. We apply both methods to the case of a hybrid EoS with a strong first order transition that entails the formation of a third family of compact stars and the corresponding mass twin phenomenon. We investigate for both models the robustness of this phenomenon against variation of the single parameter, the pressure increment at the critical chemical potential which quantifies the deviation from the Maxwell construction. We also show sets of results for other compact star observables than mass and radius, namely the moment of inertia and the baryon mass. DETAILS: The understanding of the properties of dense matter in compact star interiors is a subject of current research. Recently, great progress in this direction has been achieved by the detection of the gravitational radiation which emerged from the in spiral phase of two coalescing compact stars, an event named GW170817. Since it was observed also in all other bands of the electromagnetic spectrum, it marked the birth of multi-messenger astronomy. SUMMARY: The methods presented here can potentially be applied to the compact star crust-core transition as well. Just like at the hadron-quark boundary, the transition at the bottom of the crust may proceed via pasta phases dominated by Coulomb forces and surface tension effects Further astrophysical aspects of mixed phases inside neutron stars include potentially observable effects such as the rotational evolution, pulsar glitches, gravitational wave emission and cooling. They could be sufficiently sensible to the nature of the phase transition, proceeding via pasta phases or not, and thus provide potential signatures of the presence and extension of a mixed phase in stars which are.
a. diffuse b. compact c. reliable d. uncertain
Q105. arXiv:1807.08121 [astro-ph.SR]: Low resolution spectroscopic investigation of Am stars using Automated method. Kaushal Sharma, Santosh Joshi, H. P. Singh. (Submitted on 21 Jul 2018). ABSTRACT: Automated method of full spectrum fitting gives reliable estimates of stellar atmospheric parameters (Teff, logg and [Fe/H]) for late A, F, G and early K type stars. Recently, the technique was further improved in the cooler regime and the validity range was extended up to M6 - M7 spectral type (Teff ∼2900K). The present study aims to explore the application of this method on the low-resolution spectra of Am stars, a class of chemically peculiar (CP) stars, to examine its robustness for these objects. We use ULySS with MILES (Medium-resolution INT Library of Empirical Spectra) V2 spectral interpolator for parameter determination. Determined Teff and logg are found to be in good agreement with those obtained from high-resolution spectroscopy. PUBLISHED: Proceeding for "First Belgo-Indian Network for Astronomy & Astrophysics (BINA) workshop", held in Nainital (India), November 15-18, 2016. Published in Bulletin of Li\`ege Royal Society of Sciences Vol. 87, p. 121-124: Discussionandfutureplans These stars have recently been studied by Joshi et al. (2017) in high-resolution spectroscopic mode. Comparison of two series of measurements shows an average difference of −377±178K, and−0.48±0.32dex for Teff and logg respectively, whereas the mean estimated errors are 193K and 0.43dex for the two parameters. Within the uncertainties, the two series of measurements are consistent. Full spectrum fitting method has been employed on peculiar stars for the first time, therefore it is important to validate the method for a larger set of such objects. For this purpose, we plan to enhance our test sample by gathering the CP stars’ spectra from various spectral archives. Once validated, this method would be useful as a parameter reduction pipeline for the low resolution spectra obtained using FOSC and other future instruments at Devasthal Optical Telescope (DOT) using
a. 3.6-m b. 3.9-m c. 4.2-m d. 5.6-m
Q106. arXiv:1808.01778 [nucl-th]: Magnetic field distribution in magnetars. Debarati Chatterjee, Jerome Novak (LUTH), Micaela Oertel (LUTH). (Submitted on 6 Aug 2018): ABSTRACT: Using an axisymmetric numerical code, we perform an extensive study of the magnetic field configurations in non-rotating neutron stars, varying the mass, magnetic field strength and the equation of state. We find that the monopolar (spherically symmetric) part of the norm of the magnetic field can be described by a single profile, that we fit by a simple eighth-order polynomial, as a function of the star's radius. This new generic profile applies remarkably well to all magnetized neutron star configurations built on hadronic equations of state. We then apply this profile to build magnetized neutron stars in spherical symmetry, using a modified Tolman-Oppenheimer-Volkov system of equations. This new formalism satisfactorily reproduces the correct behavior of the neutron star total mass with increasing magnetic field. Our " universal " magnetic field profile is intended to serve as a tool for nuclear physicists to obtain estimates of magnetic field inside neutron stars, as a function of radial depth, in order to deduce its influence on composition and related properties. It possesses the advantage of being based on magnetic field distributions from realistic self-consistent computations, which are solutions of Maxwell's equations. DETAILS:Using the simple virial theorem, one may estimate the maximum interior magnetic field to be as high as 10^18 G. If such large fields exist in the interior, they may strongly affect the energy of the charged particles by confining their motion to quantized Landau levels and consequently modify the particle population, transport properties as well as the global structure. The only case where a noticeable difference appears is when using quark matter EoS. Therefore, we make the following conjecture: the monopolar part of the norm of the magnetic field follows a universal profile, up to minor variations, when considering different neutron star models with realistic hadronic EoSs. This “universal” profile has been fitted using a simple polynomial: b0(x) = bc×(1 − 1.6x^2 − x^4 + 4.2x^6 − 2.4x^8), where x = ¯r/rmean is the ratio between the radius ¯ r in Schwarzschild coordinates and the star’s mean (or areal) radius. CONCLUSIONS: proposed a “universal” parameterization of the magnetic field profile, as a function of dimensionless stellar radius, obtained from a full numerical calculation of the magnetic field distribution. We tested this profile against several realistic hadronic EoSs, based on completely different analytic approaches, and with different magnetic field strengths in order to confirm its universality. For the case of quark matter EoSs, preliminary investigations showed that although MIT bag models conform to the universality, other quark matter EoSs may not necessarily do so. The profile is intended to serve as a tool for nuclear physicists for practical purposes, namely to obtain an estimate of the maximum field strength as a function of radial depth (within error bars), in order to deduce the composition and related properties. We applied the proposed magnetic field profile in a modified TOV-like system of equations, that include the contribution of magnetic field to the energy density and pressure, and account for the anisotropy by introducing a Lorentz force term. Compared with full numerical structure calculations, we find that qualitatively the correct tendency is reproduced and quantitatively the agreement is acceptable for large masses and small magnetic fields. Thus, although we encourage to employ the profile proposed here to conclude about the importance of magnetic field effects on matter properties, we can only recommend the use of a full axisymmetric numerical solution for modelling magnetized neutron
a. densities b. anisotropy c. stars d. EoS
Q107. arXiv:1808.01373 [physics.atom-ph]:Two-photon optical frequency reference with active ac Stark shift cancellation. V. Gerginov, K. Beloy. (Submitted on 3 Aug 2018): ABSTRACT: An optical reference based on a two-photon optical transition with ac Stark shift cancellation is proposed. The reference uses two interrogating laser fields at different frequencies. Compared to conventional optical two-photon references, the new approach offers the possibility for improved short-term stability resulting from a higher signal-to-noise and improved long-term stability due to active ac Stark shift cancellation. We demonstrate the ac Stark shift cancellation method on the 5s^2 S1/2→5d^2 D5/2 two-photon transition in 87Rb. DETAILS: The rubidium two-photon 5s^2 S1/2→5d^2 D5/2 optical transition at 778nm has been recommended as a secondary representation of the second and has been investigated as an optical frequency reference. The reference is of particular interest because of the relative simplicity of the setup, high atomic Q-factor, and the possibility of using telecommunication components at 1560nm for both excitation and frequency division down to the microwave domain by optical frequency combs. In summary, the two-colour scheme described in this work offers the possibility of building a rubidium frequency reference based on telecom components with the option of controlling the largest systematic uncertainty contributions to levels below 10^−13/√τ. Such a device would full-fill the growing need for optical frequency references that outperform their commercial microwave counterparts both short- and long-term, and can operate with relaxed environmental control requirements compared to optical references based on cold
a. atoms b. plasma c. excitations d. references
Q108. arXiv:1808.01495 [astro-ph.SR]: Luminosity constraint and entangled solar neutrino signals. Francesco Vissani. (Submitted on 4 Aug 2018): ABSTRACT: Now that neutrino propagation phenomena are understood, solar neutrino physics is entering an era when observational progresses indicate new challenges. The luminosity constraint plays a key role for current needs. We present it in a new form, improving the coefficients originally obtained by J. Bahcall, Phys. Rev. C 65 (2002) 025801. It turns out that the PP- and CNO-neutrino signals are entangled: In fact, pp-neutrinos can be extracted from the luminosity constraint only when CNO-neutrinos are quantified; the interpretation of the results of the gallium experiments depends upon both fluxes; a precise knowledge of pep-neutrinos is a precondition to extract the CNO-neutrino signal with Borexino. DETAILS:An accurate description of the Sun, provided us by the standard solar model (SSM), has been a crucial tool to proceed in our understanding since the beginning of solar neutrino science. The values of the main 8 fluxes of solar neutrinos are usually given as Φi = ϕi × 10^αi / cm^2.s where i = pp, Be, pep, B, hep, N, O, F; the identification index i runs over the 5 neutrinos of the PP-chain and the 3 neutrinos of the CNO-cycle; αi are fixed exponents and ϕi are adimensional coefficients. Discussion: After the clarification of the flavor transformation phenomena in solar neutrinos, great results have been obtained thanks to observational neutrino astronomy and new ones are expected. In particular, there is a chance of measuring for the first time a signal from CNO-neutrinos, after those seen from the PP-neutrinos, that correspond to the two main astrophysical mechanisms that fuel the stars. The measured solar luminosity, with minimal theoretical inputs, leads to the luminosity constraint, that is based on the assumptions that we understand sufficiently well nuclear physics and the Sun is in equilibrium. This is a precious tool to proceed further in the study of the Sun; we have discussed it thoroughly, proposing an improved description. We have shown that the luminosity constraint and several other facts imply that the PP and CNO-neutrino signals are entangled by the empirical need to extract both of them from solar neutrino observations. This point should be taken into account to plan future steps forward at best: It motivates further efforts to understand the gallium cross section, whose current large uncertainty limits our possibilities to exploit the existing very precise results. More in general, the existence of the entanglement between CNO- and PP-neutrino signals emphasizes even further the importance of measuring the CNO-neutrinos for the
a, last time b. observation c. inputs d. first time.
Q109. arXiv:1808.00618 [astro-ph.SR] : The Double Dust Envelopes of R Coronae Borealis Stars. Edward J. Montiel, Geoffrey C. Clayton, B. E. K. Sugerman, A. Evans, D. A. Garcia-Hernández, Kameswara Rao, N., M. Matsuura, P. Tisserand. (Submitted on 2 Aug 2018):ABSTRACT: The study of extended, cold dust envelopes surrounding R Coronae Borealis (RCB) stars began with their discovery by IRAS. RCB stars are carbon-rich supergiants characterized by their extreme hydrogen deficiency and for their irregular and spectacular declines in brightness (up to 9 mags). We have analyzed new and archival Spitzer Space Telescope and Herschel Space Observatory data of the envelopes of seven RCB stars to examine the morphology and investigate the origin of these dusty shells. Herschel, in particular, has revealed the first ever bow shock associated with an RCB star with its observations of SU Tauri. These data have allowed the assembly of the most comprehensive spectral energy distributions (SEDs) of these stars with multi--wavelength data from the ultraviolet to the submillimeter. Radiative transfer modeling of the SEDs implies that the RCB stars in this sample are surrounded by an inner warm (up to 1,200 K) and an outer cold (up to 200 K) envelope. The outer shells are suggested to contain up to 10^−3 M⊙ of dust and have existed for up to 10^5 yr depending on the expansion rate of the dust. This age limit indicates that these structures have most likely been formed during the RCB phase. DETAILS: R Coronae Borealis (RCB) stars provide an excellent opportunity to understand more about the advanced stages of stellar evolution. They form a rare class of hydrogen–poor, carbon–rich supergiants. Two formation scenarios have been proposed for their origin: the single degenerate final helium-shell flash (FF) model and the double degenerate (DD) white dwarf (WD) merger model. The latter involves the merger of a CO and a He WD, while the former takes the hot evolved central star of a planetary nebula (PN) and turns it into a cool supergiant. The trademark behaviour of RCB stars is their spectacular and irregular declines in brightness. These declines can take an RCB star up to 9 magnitudes fainter than its peak brightness, and are caused by the formation of discrete, thick clouds of carbon dust along the line of sight. CONCLUSIONS: Recently, one HdC star, HD 175893, was found to have an IR excess from analysis of WISE colors and could either represent a missing link between the two classes of objects or an RCB star going through an extended period of low dust formation. The results of our sample were compared to the FF star, V605 Aql, and the findings of Clytonet al., presented the SED for V605 Aql, which indicates the presence of ~ 10^−3 M⊙ of dust associated with its 1919 ejecta. This is on a similar level to the dust masses derived from our MOCASSIN modeling for the outer shells. In this scenario, these envelopes would have been created in the recent past. However, the rapid evolution in the effective temperature of V605 Aql from 5,000 K to 95,00 K in around 80 years, has not been found in any RCB star. The Herschel observations of SU Tau with the PACS and SPIRE instruments have led to the discovery of a bow shock like structure. This is the first known RCB star to exhibit this type of feature, which represents interactions between the SU Tau CSM and the local interstellar medium (ISM). The bow shock extends between 3000 to 5000 from the central position of SU Tau with a brighter feature in the southeast possibly indicating a location where more material is beginning to pile up. RCB stars are among the most uncommon and bizarre objects discovered in the Universe. However, they provide the opportunity to greatly advance our knowledge in areas such as stellar evolution and stellar chemistry. Additional examination of these objects, especially at 21–cm, is needed to determine the origin of the cold, diffuse CSM seen around the
a. RCB stars b. CSM stars c. ISM stars d. Tau stars
Q110. arXiv:1808.01540 [cond-mat.mes-hall]: Hybrid k⋅p tight-binding model for sub-bands and infrared inter-sub-band optics in few-layer films of transition-metal dichalcogenides: MoS2 , MoSe2, and WSe2 David A. Ruiz-Tijerina, Mark Danovich, Celal Yelgel, Viktor Zólyomi, Vladimir I. Fal'ko. (Submitted on 4 Aug 2018): ABSTRACT: We present a density functional theory parametrized hybrid k-p tight binding model for electronic properties of atomically thin films of transition-metal dichalcogenides, 2H-MX2 (M =Mo, W; X =S, Se). We use this model to analyse inter-sub-band transitions in p- and n-doped 2H−MX2 films and predict the line shapes of the inter-sub-band excitations, determined by the sub-band-dependent two-dimensional electron and hole masses, as well as excitation lifetimes due to emission and absorption of optical phonons. We find that the inter-sub-band spectra of atomically thin films of the 2H-MX2 family with thicknesses of N=2 to 7 layers densely cover the infrared spectral range of wavelengths between 2 and 30μm. The detailed analysis presented in this paper shows that for thin n -doped films, the electronic dispersion and spin-valley degeneracy of the lowest-energy sub-bands oscillate between odd and even number of layers, which may also offer interesting opportunities. Finally, we propose a specific design of van der Waals multilayer structure utilizing the inter-sub-band transitions in atomically-thin films of TMDs. Applying a bias (and possibly also gate) voltage between the two electrodes results in a shift of the Dirac points relative to each other, and allows for the alignment of the Dirac point of the “top” graphene electrode with the lower-energy sub-band in the TMD, while keeping the Fermi level in graphene above the higher-energy sub-band. The carriers can then tunnel from the graphene electrode into the higher-energy sub-band. Once in the excited sub-band state, the carrier can undergo an inter-sub-band transition, emitting light polarized in the out-of-plane direction, followed by tunnelling to the second graphene electrode from the bottom sub-band state. A potentially more favourable realization of the above process which avoids carrier loss directly from the second sub-band, or carrier tunnelling into the bottom sub-band, involves using ABC-stacked few-layer graphene. The band structure of ABC few-layer graphene has a Van Hove singularity in its density of states at the edge between conduction and valence bands. Aligning the Van Hove singularities of two such electrodes with the second and first sub-bands, respectively, would enable one to achieve preferential injection and extraction of carriers into/from the TMD film, thus offering a new way to produce functional optical fibre cables. The proposed “LEGO”-type design of IR/THz emitting materials has potential for implementation as part of a composite optical fibre, where the coupling to the out-of-plane polarized photon would be supported by the wave-guide
a. solution b. pattern c. mode d. fibre
Q111.arXiv:1808.02830 [astro-ph.GA]:The alignment is in their stars: on the spin-alignment of stars in star clusters. Ramon Rey-Raposo, Justin Read. (Submitted on 8 Aug 2018): ABSTRACT: We simulate star formation in two molecular clouds extracted from a larger disc-galaxy simulation with a spatial resolution of ~0.1 pc, one exiting a spiral arm dominated by compression, and another in an inter-arm region more strongly affected by galactic shear. Treating the stars as 'sink particles', we track their birth angular momentum, and the later evolution of their angular momentum due to gas accretion. We find that in both clouds, the sinks have spin vectors that are aligned with one another, and with the global angular momentum vector of the star cluster. This alignment is present at birth, but enhanced by later gas accretion. In the compressive cloud, the sink-spins remain aligned with the gas for at least a free fall time. By contrast, in the shear cloud, the increased turbulent mixing causes the sinks to rapidly misalign with their birth cloud on approximately a gas free-fall time. In spite of this, both clouds show a strong alignment of sink-spins at the end of our simulations, independently of environment. Summary and Conclusions:In this Letter, we have studied the effect of the galactic environment in the transference of angular momentum between a parent gas cloud and its molecular cores. Our results suggest that, at creation, the spin of a sink particle follows the angular momentum of the gas in its local galactic environment. Even in two very different galactic environments, we find that the sinks are aligned both with the global angular momentum of the cluster, and with the average angular momentum of the stars. Our results require confirmation from simulations of a larger number of molecular clouds at higher resolution and including the physics of magnetic fields and stellar feedback. However, the fact that we find that star spins are strongly aligned in two very different galactic environments suggests that star-spin alignments may be ubiquitous. This has interesting implications for the formation of massive stellar binaries and their gravitational wave
a. dissipation b. emission c. randomness d. disturbance
Q112. Gravitational Resonance Phenomenon: DUST STORMS: TRU Literary works: A Science-Fact Episode: No.35: Date: 30 June 2018: Time:10:43:37: 35. Gravitational Resonance phenomenon: DUST STORMS ON MARS AND IN DELHI INDIA: by Professor Dr. Kotcherlakota Lakshmi Narayana: These full-scale events are estimated to occur about once every three to four Mars years (six to eight Earth years), and can last up to weeks or even months. The most recently recorded storm was in 2007. A huge dust storm began forming on Mars in May 2018 and had expanded to encircle the planet by mid-June. A giant dust storm has enveloped the entire planet of Mars, with dust clouds reaching up to 40 miles high. The one currently swirling above Opportunity now blankets 14 million square miles of the Martian surface, about a quarter of the planet. All Mars dust storms are powered by sunshine. Solar heating warms the Martian atmosphere and causes the air to move, lifting dust off the ground. The chance for storms is increased when there are great temperature variations like those seen at the equator during the Martian summer. Because the planet’s atmosphere is only about 1% as dense as Earth’s only the smallest dust grains hang in the air. Surprisingly, many of the dust storms on the planet originate from one impact basin. Hellas Basin is the deepest impact crater in the Solar System. It was formed more than three billion years ago during the Late Bombardment Period when a very large asteroid hit the surface of Mars. The temperatures at the bottom of the crater can be 10 degrees warmer than on the surface and the crater is deeply filled with dust. The difference in temperature fuels wind action that picks up the dust, then storm emerge from the basin. In 1971, Mariner 9 arrived at Mars during the biggest dust storm ever recorded. Mission controllers simply waited a few weeks for the storm to subside then carried on with the mission. The biggest issue that rovers face during a dust storm is the lack of sunlight. Without the light, the rovers have trouble generating enough power to keep their electronic warm enough to function. The Viking missions of 1976 easily withstood two big dust storms without being damaged. The storm is now about 10 billion acres in size, which is enough to cover North America and Russia, or more than one-quarter of Mars. Some regions of the Martian surface have become so obscured that daylight has turned to darkness. Dust storm in India is frustrating. Since four days Delhi is suffering from the Dust storms. In my observation the dust storms have a gravitational resonance phenomenon. The mars has a less gravitational force and hence not able to contain the storm. Why specific areas on the earth are experiencing the dust storms is of course intriguing. Nevertheless, the dust storm is a universal phenomenon. My finding of resonance occurrence of the dust storms, in the universe, is marvellous. Curiosity, is nuclear powered and is mostly unaffected by the dust storm. For NASA's scientists, Curiosity can offer an unprecedented chance to answer why some Martian dust storms last for months and grow massive, while others are small and last only a week. The Gravity Waves generation intricately connected with the Dark Matter and the Dark Energy criteria of the Earth’s environment especially near to the Earth centre. Gravity waves observed on 28 June 2018 at 6h03m PM at beach. Frequent observation of Gravity Waves in Visakhapatnam Beach is really
a. exciting b. fascinating c. astounding d. perplexing
Q113. arXiv:1808.02649 [physics.plasm-ph]: Peculiar Behavior of Si Cluster Ions in Solid Al. S. Kawata, C. Deutsch, Y. J. Gu. (Submitted on 8 Aug 2018); ABSTRACT: A peculiar ion behavior is found in a Si cluster, moving with a speed of ~0.22c (c: speed of light) in a solid Al plasma: the Si ion, moving behind the forward moving Si ion closely in a several angstrom distance in the cluster, feels the wake field generated by the forward Si. The interaction potential on the rear Si may balance the deceleration backward force by itself with the acceleration forward force by the forward Si in the longitudinal moving direction. The forward Si would be decelerated normally. However, the deceleration of the rear Si, moving behind closely, would be reduced significantly, and the rear Si may catch up and overtake the forward moving Si in the cluster during the Si cluster interaction with the high-density Al plasma. DETAILS: A cluster ion beam application to inertial fusion driver. In ion beam inertial fusion application especially, a preferable ion speed may be about 0.1c ∼ 0.25c, that is, around 10 ∼ 50Mev/u. Instead of ion beam, the cluster ion beam inertial fusion has been also proposed. In the cluster ion beam (CIB) driven inertial fusion (CIF), it is expected to deposit the cluster beam energy in a small volume of the energy absorber of an inertial fusion fuel pellet by the correlated ion stopping enhancement in plasmas. SUMMARY: The Si ion peculiar behavior discussed in this paper takes in a short time scale τ of about a few fs or less. In the present case, the collisional frequency νie between a Si ion moving with 0.221c and the electrons of the solid Al is much smaller than 1/τ. Therefore, the collective behavior of the high density Al electrons, that is, the wake field, mainly contributes to the Si cluster interaction in the solid Al during τ. In addition, it should be pointed out that the overtaking behavior of the Si ions focused in this paper is difficult to observe experimentally, because the phenomenon is fast, and it is hard to distinguish one Si from another in one Si cluster. In addition, in the solid Al, one Si cluster alignment control is also difficult. The wake field is localized in space, and therefore, if one Si cluster rotates in its moving direction, Si(2) may not be covered by the Si(1) wake field. In this case, the Si ion overtaking behavior may not be taken place. In this paper we have presented the peculiar ion motion in a cluster interacting with the solid Al. In the context of the ion beam inertial fusion, the target electron density is so high, and the ion or cluster speed is very high: v0/sqar(Te/me) >> 1. Therefore, the wake field created by each ion in one cluster influences ions just behind the ion concerned, though the wake field strength is high because of the ion high speed. In this extreme situation, the ion, just behind the forward-moving ion in the cluster, catches up the forward ion, and moves ahead of the other forward ion. though the front ion loses its energy normally. When the target becomes hot and dilute, the perfect vicinage effect, that is, the stopping power enhancement would be
a. anticipated b. imagined c. expected d. thought
a. RCB stars b. CSM stars c. ISM stars d. Tau stars
Q110. arXiv:1808.01540 [cond-mat.mes-hall]: Hybrid k⋅p tight-binding model for sub-bands and infrared inter-sub-band optics in few-layer films of transition-metal dichalcogenides: MoS2 , MoSe2, and WSe2 David A. Ruiz-Tijerina, Mark Danovich, Celal Yelgel, Viktor Zólyomi, Vladimir I. Fal'ko. (Submitted on 4 Aug 2018): ABSTRACT: We present a density functional theory parametrized hybrid k-p tight binding model for electronic properties of atomically thin films of transition-metal dichalcogenides, 2H-MX2 (M =Mo, W; X =S, Se). We use this model to analyse inter-sub-band transitions in p- and n-doped 2H−MX2 films and predict the line shapes of the inter-sub-band excitations, determined by the sub-band-dependent two-dimensional electron and hole masses, as well as excitation lifetimes due to emission and absorption of optical phonons. We find that the inter-sub-band spectra of atomically thin films of the 2H-MX2 family with thicknesses of N=2 to 7 layers densely cover the infrared spectral range of wavelengths between 2 and 30μm. The detailed analysis presented in this paper shows that for thin n -doped films, the electronic dispersion and spin-valley degeneracy of the lowest-energy sub-bands oscillate between odd and even number of layers, which may also offer interesting opportunities. Finally, we propose a specific design of van der Waals multilayer structure utilizing the inter-sub-band transitions in atomically-thin films of TMDs. Applying a bias (and possibly also gate) voltage between the two electrodes results in a shift of the Dirac points relative to each other, and allows for the alignment of the Dirac point of the “top” graphene electrode with the lower-energy sub-band in the TMD, while keeping the Fermi level in graphene above the higher-energy sub-band. The carriers can then tunnel from the graphene electrode into the higher-energy sub-band. Once in the excited sub-band state, the carrier can undergo an inter-sub-band transition, emitting light polarized in the out-of-plane direction, followed by tunnelling to the second graphene electrode from the bottom sub-band state. A potentially more favourable realization of the above process which avoids carrier loss directly from the second sub-band, or carrier tunnelling into the bottom sub-band, involves using ABC-stacked few-layer graphene. The band structure of ABC few-layer graphene has a Van Hove singularity in its density of states at the edge between conduction and valence bands. Aligning the Van Hove singularities of two such electrodes with the second and first sub-bands, respectively, would enable one to achieve preferential injection and extraction of carriers into/from the TMD film, thus offering a new way to produce functional optical fibre cables. The proposed “LEGO”-type design of IR/THz emitting materials has potential for implementation as part of a composite optical fibre, where the coupling to the out-of-plane polarized photon would be supported by the wave-guide
a. solution b. pattern c. mode d. fibre
Q111.arXiv:1808.02830 [astro-ph.GA]:The alignment is in their stars: on the spin-alignment of stars in star clusters. Ramon Rey-Raposo, Justin Read. (Submitted on 8 Aug 2018): ABSTRACT: We simulate star formation in two molecular clouds extracted from a larger disc-galaxy simulation with a spatial resolution of ~0.1 pc, one exiting a spiral arm dominated by compression, and another in an inter-arm region more strongly affected by galactic shear. Treating the stars as 'sink particles', we track their birth angular momentum, and the later evolution of their angular momentum due to gas accretion. We find that in both clouds, the sinks have spin vectors that are aligned with one another, and with the global angular momentum vector of the star cluster. This alignment is present at birth, but enhanced by later gas accretion. In the compressive cloud, the sink-spins remain aligned with the gas for at least a free fall time. By contrast, in the shear cloud, the increased turbulent mixing causes the sinks to rapidly misalign with their birth cloud on approximately a gas free-fall time. In spite of this, both clouds show a strong alignment of sink-spins at the end of our simulations, independently of environment. Summary and Conclusions:In this Letter, we have studied the effect of the galactic environment in the transference of angular momentum between a parent gas cloud and its molecular cores. Our results suggest that, at creation, the spin of a sink particle follows the angular momentum of the gas in its local galactic environment. Even in two very different galactic environments, we find that the sinks are aligned both with the global angular momentum of the cluster, and with the average angular momentum of the stars. Our results require confirmation from simulations of a larger number of molecular clouds at higher resolution and including the physics of magnetic fields and stellar feedback. However, the fact that we find that star spins are strongly aligned in two very different galactic environments suggests that star-spin alignments may be ubiquitous. This has interesting implications for the formation of massive stellar binaries and their gravitational wave
a. dissipation b. emission c. randomness d. disturbance
Q112. Gravitational Resonance Phenomenon: DUST STORMS: TRU Literary works: A Science-Fact Episode: No.35: Date: 30 June 2018: Time:10:43:37: 35. Gravitational Resonance phenomenon: DUST STORMS ON MARS AND IN DELHI INDIA: by Professor Dr. Kotcherlakota Lakshmi Narayana: These full-scale events are estimated to occur about once every three to four Mars years (six to eight Earth years), and can last up to weeks or even months. The most recently recorded storm was in 2007. A huge dust storm began forming on Mars in May 2018 and had expanded to encircle the planet by mid-June. A giant dust storm has enveloped the entire planet of Mars, with dust clouds reaching up to 40 miles high. The one currently swirling above Opportunity now blankets 14 million square miles of the Martian surface, about a quarter of the planet. All Mars dust storms are powered by sunshine. Solar heating warms the Martian atmosphere and causes the air to move, lifting dust off the ground. The chance for storms is increased when there are great temperature variations like those seen at the equator during the Martian summer. Because the planet’s atmosphere is only about 1% as dense as Earth’s only the smallest dust grains hang in the air. Surprisingly, many of the dust storms on the planet originate from one impact basin. Hellas Basin is the deepest impact crater in the Solar System. It was formed more than three billion years ago during the Late Bombardment Period when a very large asteroid hit the surface of Mars. The temperatures at the bottom of the crater can be 10 degrees warmer than on the surface and the crater is deeply filled with dust. The difference in temperature fuels wind action that picks up the dust, then storm emerge from the basin. In 1971, Mariner 9 arrived at Mars during the biggest dust storm ever recorded. Mission controllers simply waited a few weeks for the storm to subside then carried on with the mission. The biggest issue that rovers face during a dust storm is the lack of sunlight. Without the light, the rovers have trouble generating enough power to keep their electronic warm enough to function. The Viking missions of 1976 easily withstood two big dust storms without being damaged. The storm is now about 10 billion acres in size, which is enough to cover North America and Russia, or more than one-quarter of Mars. Some regions of the Martian surface have become so obscured that daylight has turned to darkness. Dust storm in India is frustrating. Since four days Delhi is suffering from the Dust storms. In my observation the dust storms have a gravitational resonance phenomenon. The mars has a less gravitational force and hence not able to contain the storm. Why specific areas on the earth are experiencing the dust storms is of course intriguing. Nevertheless, the dust storm is a universal phenomenon. My finding of resonance occurrence of the dust storms, in the universe, is marvellous. Curiosity, is nuclear powered and is mostly unaffected by the dust storm. For NASA's scientists, Curiosity can offer an unprecedented chance to answer why some Martian dust storms last for months and grow massive, while others are small and last only a week. The Gravity Waves generation intricately connected with the Dark Matter and the Dark Energy criteria of the Earth’s environment especially near to the Earth centre. Gravity waves observed on 28 June 2018 at 6h03m PM at beach. Frequent observation of Gravity Waves in Visakhapatnam Beach is really
a. exciting b. fascinating c. astounding d. perplexing
Q113. arXiv:1808.02649 [physics.plasm-ph]: Peculiar Behavior of Si Cluster Ions in Solid Al. S. Kawata, C. Deutsch, Y. J. Gu. (Submitted on 8 Aug 2018); ABSTRACT: A peculiar ion behavior is found in a Si cluster, moving with a speed of ~0.22c (c: speed of light) in a solid Al plasma: the Si ion, moving behind the forward moving Si ion closely in a several angstrom distance in the cluster, feels the wake field generated by the forward Si. The interaction potential on the rear Si may balance the deceleration backward force by itself with the acceleration forward force by the forward Si in the longitudinal moving direction. The forward Si would be decelerated normally. However, the deceleration of the rear Si, moving behind closely, would be reduced significantly, and the rear Si may catch up and overtake the forward moving Si in the cluster during the Si cluster interaction with the high-density Al plasma. DETAILS: A cluster ion beam application to inertial fusion driver. In ion beam inertial fusion application especially, a preferable ion speed may be about 0.1c ∼ 0.25c, that is, around 10 ∼ 50Mev/u. Instead of ion beam, the cluster ion beam inertial fusion has been also proposed. In the cluster ion beam (CIB) driven inertial fusion (CIF), it is expected to deposit the cluster beam energy in a small volume of the energy absorber of an inertial fusion fuel pellet by the correlated ion stopping enhancement in plasmas. SUMMARY: The Si ion peculiar behavior discussed in this paper takes in a short time scale τ of about a few fs or less. In the present case, the collisional frequency νie between a Si ion moving with 0.221c and the electrons of the solid Al is much smaller than 1/τ. Therefore, the collective behavior of the high density Al electrons, that is, the wake field, mainly contributes to the Si cluster interaction in the solid Al during τ. In addition, it should be pointed out that the overtaking behavior of the Si ions focused in this paper is difficult to observe experimentally, because the phenomenon is fast, and it is hard to distinguish one Si from another in one Si cluster. In addition, in the solid Al, one Si cluster alignment control is also difficult. The wake field is localized in space, and therefore, if one Si cluster rotates in its moving direction, Si(2) may not be covered by the Si(1) wake field. In this case, the Si ion overtaking behavior may not be taken place. In this paper we have presented the peculiar ion motion in a cluster interacting with the solid Al. In the context of the ion beam inertial fusion, the target electron density is so high, and the ion or cluster speed is very high: v0/sqar(Te/me) >> 1. Therefore, the wake field created by each ion in one cluster influences ions just behind the ion concerned, though the wake field strength is high because of the ion high speed. In this extreme situation, the ion, just behind the forward-moving ion in the cluster, catches up the forward ion, and moves ahead of the other forward ion. though the front ion loses its energy normally. When the target becomes hot and dilute, the perfect vicinage effect, that is, the stopping power enhancement would be
a. anticipated b. imagined c. expected d. thought
Q114. trusciencetrutechnology@blogspot.com Volume 2018, Issue No.7c, Dated: 16 July, 2018. The Indian Science Congress Association 106th Physics Session to be held, January 3-7, 2019.
DIVERSE MANIFESTATION OF EARTH
Professor Dr. Kotcherlakota Lakshmi Narayana,
trusciencetrutechnology@blogspot.com
17-11-10, Narasimha Ashram, Official Colony,
Maharanipeta.P.O, Visakhapatanam-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 catalyse the interaction of salt water with the graviton, producing newer 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 newer photons of extraordinary properties. The novel operator
keep 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 physicists.
INTRODUCTION
A new formulation of the Graviton and its manifest Earth’s modifications has been presented.[1,2] 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 physicists.
MY MODEL CONSIDERATIONS:
17:59 PM 02 June 2018: I regard the Earth to be a system of diverse manifestation, comprising of the outer Earthly space to be a dust & water vapour, and on the surface manifests as the Ocean system of salt water, and deep to 100km or about 60miles lithosphere crust. Essentially in fine particulate manner the outer Earthly space, with a joint system of dust & water vapour interaction. 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.
Neutrinos are categorised as three "flavours"; Electron, Muon and Tau, sometimes interact with matter through the Weak Force (one of the four fundamental forces of the universe) and gravity. 1. Present article expects the neutrino to catalyse the interaction of salt water with the graviton, producing newer photons. Apart from, a diverse manifestation of ocean system of salt water, graviton interacts with the ocean system, resulting in production of newer photons. These may have masses and different from the photons of the deep interior Earth system. 2. One cannot rule the possibility of neutrinos of different kind to exist and interact with the speculative newer photons of differing mass. Structure of Earth layered commonly divided into four parts: Silicate Crust, Viscous Mantle, Liquid iron-nickel outer core, and the solid iron-nickel inner core. One of the most prevalent views is that Yellowstone's super-volcano was formed by a vertical column of hot rocks rising from the top of the earth's core, known as a mantle plume. Essentially, the four parts of the Earth are Core, Mantle, Outer Core and Inner Core. 3. I expect all these four parts have distinct graviton mass and the newer photons of extraordinary properties.
Heat escaped from inner core, solid 3960mi, 6371km and causes electric currents in the conductive material of Outer core. Outer core, the flow of this liquid layer is very slow-moving (about a few km a year), it is what produces Earth's magnetic field. Our North and South Poles exist because of this liquid Outer core, even though it's almost 2,000 miles below us.
I expect that the newer photons of differing mass, inside the earth, sustains the Earth structure in a very timid fashion, to interact not only with the passing out neutrinos of three different types but also imbibe a consistent with the slow-moving liquid layer, of electric conductive currents, producing the Earth’s magnetic field. 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 physicists.
<g| mµν | (γµ γν )> in this matrix element I have used the novel operators and, mµν on the right hand side. Graviton of spin 2 resolves by the presence of these operators and mµν, the later with double, to go with the two photons each endowed with a single suffix. The novel operator keep the two photons γµ , γν bound in their interaction, and mµν with graviton. There are several interactions that the graviton undergoes. At first in the outer atmosphere of the Earth it interacts with the dust and moisture content, I anticipate with the interactions being distinct and unique. An increase in the load of aerosols, or tiny particulate matter (PM), in the atmosphere, with the dust grains graviton gets lost but emits away the photons. With the moisture, the graviton acquires the bond-bound transformation and the photons, are jolted out as radiation.
mµν | (γµ γν )> in this matrix element I have used the novel operators and, mµν on the right hand side. Graviton of spin 2 resolves by the presence of these operators and mµν, the later with double, to go with the two photons each endowed with a single suffix. The novel operator keep the two photons γµ , γν bound in their interaction, and mµν with graviton. There are several interactions that the graviton undergoes. At first in the outer atmosphere of the Earth it interacts with the dust and moisture content, I anticipate with the interactions being distinct and unique. An increase in the load of aerosols, or tiny particulate matter (PM), in the atmosphere, with the dust grains graviton gets lost but emits away the photons. With the moisture, the graviton acquires the bond-bound transformation and the photons, are jolted out as radiation.
In the sea or oceans of the earth graviton interacts with the salty water and the disintegrated two photons become the bumpy stride of the salt water, even measuring up with the distant objects like the Moon. Oscillatory nature of the salt water of the sea/ocean getting attracted by the far away objects suggests photon manifestation by the distant gravitons.
In the first layer of the Earth, graviton becomes massive, and interaction results in the two photons, that transform into component form, of electric and magnetic fields. The beauty of the theory is that it keeps the graviton as a single entity. Interaction operator mµν is unique and splits the graviton into two γµ , γν photons bound by . The right hand sides expanded we get the actual compact form explicitly given below.
mµν is unique and splits the graviton into two γµ , γν photons bound by . The right hand sides expanded we get the actual compact form explicitly given below.
<g| (m11.11 + m10.10 +m1-1.1(-1) + m01.01 + m00.0 0+ m0-1.0(-1) + m-11.(-1)1+ m-10.(-1)0 + m-1-1.(-1)(-1)>.
And the matrix (m11, m10, m1-1, m01, m00, m0-1, m-11 , m-10, m-1-1) of the nine fields goes with all the nine 1 + m10.10 +m1-1.1(-1) + m01.01 + m00.0 0+ m0-1.0(-1) + m-11.(-1)1+ m-10.(-1)0 + m-1-1.(-1)(-1)>.products of γµ , γν respectively in the first layer of the Earth, graviton becomes....... results in the two photons, that transform into compollnent form of electric and magnetic fields. The beauty of the theory is that it keeps the graviton as a single entity. The matrix (m11, m10, m1-1, m01, m00, m0-1, m-11 , m-10, m-1-1) of the nine fields goes with all the nine products of γµ , γν respectively.
REFERENCES:
1. June 5, 2018: Science News: ScienceDaily, University of Liverpool: New insight into Earth's crust, mantle and outer core interactions. A new study uses previously unavailable data to confirm a correlation between the movement of plate tectonics on the Earth's surface, the flow of mantle above the Earth's core and the of reversal of the Earth's magnetic field, which has long been hypothesized.
2. May 31, 2018: ScienceDaily: University of Maryland. How rate Earth slows the solar wind to a gentle breeze? NASA satellite data reveals electron-scale energy transformation at the leading edge of Earth's magnetic field. A new study describes the first observations of the process of electron heating in Earth's bow shock. The researchers found that when the electrons in the solar wind encounter the bow shock, they momentarily accelerate to such a high speed that the electron stream becomes unstable and breaks down. This breakdown process robs the electrons of their high speed and converts the energy to heat.
ACKNOWLEDGEMENT:
The author is greatly indebted to Late Prof K. R. Rao, D.Sc.(Madras), D.Sc.(London) for his guidance and encouragement, to publish newer thoughts in Science & Technology. I was with him at Andhra University, from 1949-1972, and learnt from him, many a research adventures. I am also grateful to Late Mrs. Peramma Rangadhama Rao for her support and interest in my works.
The author is greatly indebted to Late Prof K. R. Rao, D.Sc.(Madras), D.Sc.(London) for his guidance and encouragement, to publish newer thoughts in Science & Technology. I was with him at Andhra University, from 1949-1972, and learnt from him, many a research adventures. I am also grateful to Late Mrs. Peramma Rangadhama Rao for her support and interest in my works.
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The Indian Science Congress Association, 14, Dr. Biresh Guha St., Kolkata-700017. Tel. Nos. (033) 2287-4530/2281-5323, Fax No.91-33-2287-2551/2287-2551 E-mail : es.sciencecongress@nic.in / iscacal@vsnl.net,Website : http://www.sciencecongress.nic.in
Submission of Papers for 106th ISC to respective sectional Presidents by 15th September 2018
======================================================================
In the first layer of the Earth, graviton becomes
a. heavy b. light c. oscillatory. d. massive
115. trusciencetrutechnology@blogspot.com
=====================================================
x1:=3.8888;x2:=-2.3308;x3:=-2.779+i*0.295864;
x1:=63.49464;x2:=52.294641; x3:=-60.996419+i*5.295;
x1:=4.01739;x2:=-2.08390;x3:=-2.965+i*0.7;
x1:=3.8989;x2:=-4.3803; x3:=-1.7593+i*0.1942;
x1:=3.92885;x2:=-4.44195;x3:=-1.74343+i*0.148628;
m1:=0.5; m3:=0.5; l4-4.l3-3.77778.l2+1.1112.l-0.09875;
y3-4.88889.y2+7.97223.y-4.34028;
x1:=3.88884;x2:=-2.33076;x3:=-2.77904+i*0.29586;
y3-4.97889.y2+8.332223.y-4.72338;
x1:=3.98289;x2:=-2.129898;x3:=-2.926496+i*0.7;
a. heavy b. light c. oscillatory. d. massive
115. trusciencetrutechnology@blogspot.com
Volume 2018, Issue No.7d, Dated: 23 July 2018
=================================================
The Indian Science Congress Association 106th Mathematics & Statistics Session to be held, January 3-7, 2019. 14 Dr. Biresh Guha St. Kolkata-700017. =====================================================
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 analysed to obtain the mass dependent Eigen values. The Cyclic group reveals both the real and imaginary Eigen values. The V4 Klein group on the other hand presents only real Eigen values. Both the positive and anti-positive mass terms are used adopting that the anti-particles 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.
INTRODUCTION
Two different sets of Klein and the ordinary 4th order-matrices were used to generate the distinct groups. The ordinary 4th order-matrices gave distinct roots suggesting the complex and real roots of considerable complexity. All the roots possible are enlisted and complex terms indicated. Unlike this, the Klein set gave plain straight forward roots and several sets of roots are listed. They are found to be real and no complex behaviour evident. The calculations have thus brought out the distinctive features of the two different sets of Klein and ordinary 4th order-matrices which were presented in this paper.
The fourth order groups, the Cyclic and the V4 Klein groups have been analysed to obtain the mass dependent Eigen values. The Cyclic group reveals both the real and imaginary Eigen values. The V4 Klein group on the other hand presents only real Eigen values. Both the positive and anti-positive mass terms are used adopting that the anti-particles 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, 0.2, 0.4, 0.5, 0.6, 0.7, 0.9.
Cyclic group
m1:=0.5;m3:=0.5;l4+6.3222534.l3-114.9917341.l2-160.437934.l+2862.351717;x1:=3.8888;x2:=-2.3308;x3:=-2.779+i*0.295864;
x4:= -2.779-i*0.295864;
m1:=0.4;m3:=0.6; l4+6.207556.l3-115.644.l2-151.1417089.l+2901.352736;x1:=63.49464;x2:=52.294641; x3:=-60.996419+i*5.295;
x4:= -60.996419-i*5.295;
m1:=0.2; m3:=0.8; l4+5.823121.l3-120.5275984.l2-123.7828232.l+3186447232;x1:=4.01739;x2:=-2.08390;x3:=-2.965+i*0.7;
x4:= -2.965-i*0.7;
m1:=0.8;m3:=0.2;
l4+6.578668.l3-113.7629972.l2-83.2204372.l+2774.711933;
x1:=63.35153295;x2:=51.27793295;
x3:=-60.60406705+i*4.2396;x4:= -60.60406705-i*4.2396;
m1:=0.6;m3:=0.4; l4+6.417112198.l3-114.4915552.l2-168.5062189.l+2830.142332;x1:=3.8989;x2:=-4.3803; x3:=-1.7593+i*0.1942;
x4:= -1.7593-i*0.1942;
m1:=0.7;m3:=0.3; l4-4.l3-3.85778.l2+1.271112.l-0.1060436733;x1:=3.92885;x2:=-4.44195;x3:=-1.74343+i*0.148628;
x4:= -1.74343-i*0.148628;
V4 or Klein Group
Klein set of Matrices: The Vierergruppe is the Abelian abstract group on four elements that is isomorphic to the finite group c2xc2 and the dihedral group D2. The masses m1, m2, m3, m4 are set, such that m2=-m1 and m4=-m3. Later m1=m3 was used to simplify the matrix for diagonalization.
A:=<<e-m1-l,a,b,c|a,e-m2-l,c,b|b,c,e-m3-l|c,b,a,e-m4-l>>;
Also a=e=1 was chosen setting b=1/2, c=1/3.
The roots set as x1, x2, x3 and x4 for each set of m1 and m3 values.m1:=0.5; m3:=0.5; l4-4.l3-3.77778.l2+1.1112.l-0.09875;
y3-4.88889.y2+7.97223.y-4.34028;
x1:=3.88884;x2:=-2.33076;x3:=-2.77904+i*0.29586;
x4:= -2.77904-i*0.29586;
m1:=0.2; m3:=0.8;l4-4.l3-3.95778.l2+1.471112.l-0.11065y3-4.97889.y2+8.332223.y-4.72338;
x1:=3.98289;x2:=-2.129898;x3:=-2.926496+i*0.7;
x4:= -2.926496-i*0.7;
m1:=0.6;m3:=0.4; l4-4.l3-3.79778.l2+1.151112l-1.0087707;
y3-4.89889.y2+8.012223.y-4.382047;
x1:=3.8988;x2:=-3.37576;x3:=-2.26145+i*0.81478;
x4:= -2.26145-i*0.81478;
m1:=0.7;m3:=0.3;l4-4.l3-3.85778.l2+1.271112.l-0.1064367;
y3-4.92889.y2+8.132223.y-4.508547;
x1:=3.928891;x2:=-2.211821;x3:=-2.858535+i*0.5257028;
x4:= -2.858535-i*0.5257028;
m1:=0.1;m3:=0.9;l4-4.l3-4.09778.l2+1.751112.l-0.10871;
y3-5.04889.y2+8.612223.y-5.03255;
x1:=4.0488902;x2:=-2.0316578;x3:=-3.0086162+i*0.882414;
x4:= -3.0086162-i*0.882414;
REFERENCES
2. Cotton, F. A. Chemical Applications of Group Theory, 3rd ed. New York: Wiley, 1990.
CITE THIS AS: Weisstein, Eric W. "Cyclic Group C - 4." From MathWorld--A Wolfram Web Resource. http://mathworld.wolfram.com/CyclicGroupC4.html.
The mass values m1 and m3 were varied from 0.1, 0.2, 0.4, 0.5, 0.6, 0.7, 0.9 and the respective obtained
The mass values m1 and m3 were varied from 0.1, 0.2, 0.4, 0.5, 0.6, 0.7, 0.9 and the respective obtained
a. Eigenvalues b. Eigenvectors c. cyclic values d. c4 values
Q116. arXiv:1809.00146 [astro-ph.SR]: Dark structures in sunspot light bridges. Jingwen Zhang, et al. (Submitted on 1 Sep 2018): ABSTRACT: We present unprecedented high-resolution TiO images and Fe I 1565 nm spectropolarimetric data of two light bridges taken by the 1.6-m Goode Solar Telescope at Big Bear Solar Observatory. In the first light bridge (LB1), we find striking knot-like dark structures within the central dark lane. Many dark knots show migration away from the penumbra along the light bridge. The sizes, intensity depressions and apparent speeds of their proper motion along the light bridges of 33 dark knots identified from the TiO images are mainly in the ranges of 80∼ 200-km, 30\% ∼ 50\%, and 0.3 ∼ 1.2-km-s^−1, respectively. In the second light bridge (LB2), a faint central dark lane and striking transverse intergranular lanes were observed. These intergranular lanes have sizes and intensity depressions comparable to those of the dark knots in LB1, and also migrate away from the penumbra at similar speeds. Our observations reveal that LB2 is made up of a chain of evolving convection cells, as indicated by patches of blue shift surrounded by narrow lanes of red shift. The central dark lane generally corresponds to blueshifts, supporting the previous suggestion of central dark lanes being the top parts of convection upflows. In contrast, the intergranular lanes are associated with redshifts and located at two sides of each convection cell. The magnetic fields are stronger in intergranular lanes than in the central dark lane. These results suggest that these intergranular lanes are manifestations of convergent convective downflows in the light bridge. We also provide evidence that the dark knots observed in LB1 may have a similar origin. DETAILS: Sunspots, the darkest regions on the solar surface, are believed to result from strong magnetic fields inhibiting convection and thereby thereby blocking the passage of heat from the solar interior to the surface. The TiO filter with a 10 ˚A bandwidth was centered at the wavelength of 7057 *A. The TiO data were corrected for dark currents and flat fields. CONCLUSIONS: On the contrary, sections of the central dark lane bounded by two intergranular lanes correspond to blueshifts in the center of convection cells. We also find that LB2 evolves into a much narrower light bridge on 2015 June 22, when a central dark lane and dark knots can be clearly identified. These results suggest that a narrow light bridge is made up of a chain of convection cells, just like broader, granular light bridges. In the center of each convection cell, upflows raise up the τ=1 surface and result in a central dark lane. Whereas on the two endpoints of the convection cells, depending on the width a light bridge, converging downflows may create dot-like dark knots or elongated intergranular lanes. By observing the dynamics of these dark structures, we now can infer some detailed information about the evolution of the convection
a. lanes b. knots c. cells d. endpoint
Q117. arXiv:1809.01618 [astro-ph.SR]: Solar UV and X-Ray Spectral Diagnostics. Giulio Del Zanna, Helen E. Mason; (Submitted on 5 Sep 2018): ABSTRACT: X-Ray and Ultraviolet (UV) observations of the outer solar atmosphere have been used for many decades to measure the fundamental parameters of the solar plasma. This review focuses on the optically thin emission from the solar atmosphere, mostly found at UV and X-ray (XUV) wavelengths, and discusses some of the diagnostic methods that have been used to measure electron densities, electron temperatures, differential emission measure (DEM), and relative chemical abundances. We mainly focus on methods and results obtained from high-resolution spectroscopy, rather than broad-band imaging. However, we note that the best results are often obtained by combining imaging and spectroscopic observations. We also mainly focus the review on measurements of electron densities and temperatures obtained from single ion diagnostics, to avoid issues related to the ionisation state of the plasma. We start the review with a short historical introduction on the main XUV high-resolution spectrometers, then review the basics of optically thin emission and the main processes that affect the formation of a spectral line. We mainly discuss plasma in equilibrium, but briefly mention non-equilibrium ionisation and non-thermal electron distributions. We also summarise the status of atomic data, which are an essential part of the diagnostic process. We then review the methods used to measure electron densities, electron temperatures, the DEM, and relative chemical abundances, and the results obtained for the lower solar atmosphere (within a fraction of the solar radii), for coronal holes, the quiet Sun, active regions and flares. DETAILS: The solar corona is a very hot plasma (1 MK or more) that is mostly optically thin. The emission is due to highly-ionised atoms, which emit principally in the X-rays (5–50 ˚A), soft X-rays (50– 150 ˚A), Extreme Ultra-Violet (EUV, 150–900 ˚A) or far Ultra-Violet (UV, 900–2000 ˚A) region of the spectrum. Since radiation at these wavelengths cannot penetrate to the Earth’s surface, most of the observations and spectral diagnostics have been obtained from XUV (5–2000 ˚A) observations from space. CONCLUSIONS:There has been tremendous progress in the plasma diagnostics for XUV spectroscopy since the early rocket observations, in particular in the determination of the physical state of the emitting plasma. Great strides have been made with high cadence imaging instruments, such as SDO/AIA. A better knowledge of the contribution of spectral lines to the Hinode/XRT and SDO/AIA channels, for example using Hinode/EIS spectra has been very fruitful. A very powerful tool is provided by combining imaging and spectroscopic observations, in particular with the combination of SDO, Stereo, Hinode and IRIS instruments. XUV spectrometers have produced a large amount of data in the past couple of decades, however improvements in terms of spectral resolution, spatial resolution and radiometric calibration have been modest, when compared to earlier observations, for example Skylab and HRTS. More recent spectrometers, such as IRIS, have provided much improved spatial and spectral resolution, with high cadence, but only over a limited wavelength range and
a. HRTS b.IRIS c. Skylab d. FOV
Q118. arXiv:1808.09967 [astro-ph.EP]: Dust Production and Depletion in Evolved Planetary Systems. J. Farihi, et al. (Submitted on 29 Aug 2018): ABSTRAACT: The infrared dust emission from the white dwarf GD 56 is found to rise and fall by 20% peak-to-peak over 11.2 yr, and is consistent with ongoing dust production and depletion. It is hypothesized that the dust is produced via collisions associated with an evolving dust disk, temporarily increasing the emitting surface of warm debris, and is subsequently destroyed or assimilated within a few years. The variations are consistent with debris that does not change temperature, indicating that dust is produced and depleted within a fixed range of orbital radii. Gas produced in collisions may rapidly re-condense onto grains, or may accrete onto the white dwarf surface on viscous timescales that are considerably longer than Poynting-Robertson drag for micron-sized dust. This potential delay in mass accretion rate change is consistent with multi-epoch spectra of the unchanging Ca II and Mg II absorption features in GD 56 over 15 yr, although the sampling is sparse. Overall these results indicate that collisions are likely to be the source of dust and gas, either inferred or observed, orbiting most or all polluted white dwarfs. DETAILS:This paper reports long-term, 3−5µm infrared flux variations in the polluted white dwarf GD56 (= WD0408–041), a hydrogen atmosphere (DA-type) star with Teff ≈ 15000K and a cooling age around 200Myr. The variability in the infrared is presented together with optical spectroscopy that reveals constant, photospheric metal absorption over a similar timescale. Infrared data are comprised of nine Spitzer observational epochs spanning 11.2yr from 2006 to 2017, and are supplemented by multiepoch WISE data from 2010 and 2014–2017. There has been one substantial increase of at least 20%, and what appear to be two decaying trends of similar magnitude, all taking place over several years each. These changes are interpreted as the production (increase) of dust clouds, and their subsequent depletion (decrease), where possible scenarios may also account for the flux decrease at SDSS0959.CONCLUSIONS:Infrared observations of GD56 reveal both brightening and dimming events associated with circumstellar dust. Over a span of 11.2yr, the 3−5µm fluxes in both Spitzer and WISE are shown to increase and decrease, where the peak-to-peak changes are over 20% and a gradual dimmingis apparent for at least one and possibly two intervals. Incontrast, neither the flux ratios between the two shortest wavelength channels on both spacecraft, nor the photospheric metal absorption in the star appear to be changing. These collective results suggest dust is produced and later destroyed (or subsumed) without any significant change in the range of orbital radii; i.e. PR drag is not affecting the distribution of the emitting dust. Anygas resulting from the dust production process – including small dust grains that rapidly sublimate – may quickly re-condense onto grains or join an α-like accretion disk, and this may delay changes in mass accretion rate for decades or longer. Whilelikelynearing the end of their mission lifetimes, both Spitzer and NEOWISE currently offer the best observational constraints on the evolving and dusty planetary systems orbiting polluted white
a. holes b. giants c. dwarfs d. dust
a. HRTS b.IRIS c. Skylab d. FOV
Q118. arXiv:1808.09967 [astro-ph.EP]: Dust Production and Depletion in Evolved Planetary Systems. J. Farihi, et al. (Submitted on 29 Aug 2018): ABSTRAACT: The infrared dust emission from the white dwarf GD 56 is found to rise and fall by 20% peak-to-peak over 11.2 yr, and is consistent with ongoing dust production and depletion. It is hypothesized that the dust is produced via collisions associated with an evolving dust disk, temporarily increasing the emitting surface of warm debris, and is subsequently destroyed or assimilated within a few years. The variations are consistent with debris that does not change temperature, indicating that dust is produced and depleted within a fixed range of orbital radii. Gas produced in collisions may rapidly re-condense onto grains, or may accrete onto the white dwarf surface on viscous timescales that are considerably longer than Poynting-Robertson drag for micron-sized dust. This potential delay in mass accretion rate change is consistent with multi-epoch spectra of the unchanging Ca II and Mg II absorption features in GD 56 over 15 yr, although the sampling is sparse. Overall these results indicate that collisions are likely to be the source of dust and gas, either inferred or observed, orbiting most or all polluted white dwarfs. DETAILS:This paper reports long-term, 3−5µm infrared flux variations in the polluted white dwarf GD56 (= WD0408–041), a hydrogen atmosphere (DA-type) star with Teff ≈ 15000K and a cooling age around 200Myr. The variability in the infrared is presented together with optical spectroscopy that reveals constant, photospheric metal absorption over a similar timescale. Infrared data are comprised of nine Spitzer observational epochs spanning 11.2yr from 2006 to 2017, and are supplemented by multiepoch WISE data from 2010 and 2014–2017. There has been one substantial increase of at least 20%, and what appear to be two decaying trends of similar magnitude, all taking place over several years each. These changes are interpreted as the production (increase) of dust clouds, and their subsequent depletion (decrease), where possible scenarios may also account for the flux decrease at SDSS0959.CONCLUSIONS:Infrared observations of GD56 reveal both brightening and dimming events associated with circumstellar dust. Over a span of 11.2yr, the 3−5µm fluxes in both Spitzer and WISE are shown to increase and decrease, where the peak-to-peak changes are over 20% and a gradual dimmingis apparent for at least one and possibly two intervals. Incontrast, neither the flux ratios between the two shortest wavelength channels on both spacecraft, nor the photospheric metal absorption in the star appear to be changing. These collective results suggest dust is produced and later destroyed (or subsumed) without any significant change in the range of orbital radii; i.e. PR drag is not affecting the distribution of the emitting dust. Anygas resulting from the dust production process – including small dust grains that rapidly sublimate – may quickly re-condense onto grains or join an α-like accretion disk, and this may delay changes in mass accretion rate for decades or longer. Whilelikelynearing the end of their mission lifetimes, both Spitzer and NEOWISE currently offer the best observational constraints on the evolving and dusty planetary systems orbiting polluted white
a. holes b. giants c. dwarfs d. dust
Q119. arXiv:1809.01535 [physics.ins-det]: Suppression of the slow component of BaF2 crystal luminescence with a thin multilayer filter. A.M. Artikov et al. (Submitted on 5 Sep 2018) ABSTRACT: The fast component of the barium fluoride (BaF2) crystal luminescence with the emission peak at 220 nm allows those crystals to be employed in fast calorimeters operating in harsh radiation environment. However, the slow component with the emission peak at 330 nm and about 85\% of the total emission light could create big problems when working at a high radiation rate. In this work we report results of tests of multilayer filters that can suppress luminescence in the range from 250 nm to 400 nm, which covers most of the BaF2 slow component luminescence. The filters are made by spraying layers of rare earth oxides on a quartz glass substrate. Filters typically comprise 200-220 layers. A few filters were prepared by spraying thin layers on quartz glass. The filters have a peak transmittance of about 70-80\% in the range of 200-250 nm. Measurements of the light output of the BaF2 crystal with and without a filter between the crystal readout end and the PMT demonstrate substancial suppression of the slow component. To our knowledge, this kind of filters are produced and tested for the first time. DETAILS: Barium fluoride is an excellent candidate for the use in the EMC in harsh radiation environment due to its fast component of luminescence with the emission peak at 220 nm. However, the slow component of luminescence with the emission peak at 330 nm and about 85% of the total emission light needs to be suppressed to use at high radiation rate. The slow component of the BaF2 crystal luminescence could be suppressed by doping BaF2 with rare earth, depositing an atomic layer of interference filter to get solar blind windows on the sensors, applying nanoparticle coatings on sensors, and using external interference optical filters. In this work we report the results of the study of thin interference optical multilayer filters made by spraying layers of rare earth oxides on the quartz glass substrate. Such filters can suppress luminescence in the range of about 250 nm to 400 nm, which covers most of the BaF2 slow component. CONCLUSIONS: Thin multilayer interference filters made of up to 200 layers of rare earth oxides have been produced and tested with the BaF2 crystal. To our knowledge, this kind of filters were produced and tested for the first time. Such thin multilayer filters can suppress luminescence in the range from 250 nm to 400 nm and could be used for suppression of the slow component of BaF2 crystals. Tests of the filters made by spraying thin layers of rare earth oxides on a quartz glass substrate demonstrated that they suppress the total signals from the BaF2 crystal by a factor of 4. However, the results show that the fast component is suppressed by these developed filters as well. It is obvious that more research is required to improve the quality of the multilayer
a. filters b. oxides c. windows d. luminescence
Answers:
Q62d. Q63a. Q64b. Q65b. Q66d. Q67c. Q68a. Q69d.
Q70c. Q71a. Q72b. Q73c. Q74b. Q75d. Q76b. Q77c. Q78a. Q79c. Q80b. Q81a. Q82d.
Q83b. Q84a. Q85c. Q86a. Q87d. Q88b. Q89d. Q90b. Q91d. Q92b. Q93a. Q94c. Q95a.
Q96c. Q97a. Q98d. Q99c. Q100b. Q101a. Q102b. Q103d. Q104b. Q105a. Q106c. Q107a.
Q108d. Q109a. Q110b. Q111b. Q112a. Q113c. Q114d. Q115a. Q116c. Q117d. Q118c. Q119a.
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