September 9, 2018a
Volume 2018, 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-119a
Q1. arXiv.1801.03751:[astro-ph.IM]: The Use of Color Sensors for Spectrographic Calibration: Neil Thomas: (Submitted on 11 Jan 2018): The wavelength calibration of spectrographs is an essential but challenging task in many disciplines. Calibration is traditionally accomplished by imaging the spectrum of a light source containing features that are known to appear at certain wavelengths and mapping this to their location on the sensor. This is typically required in conjunction with each scientific observation to account for mechanical and optical variations of the instrument over time, which may span years for certain projects. The method presented here investigates the usage of color itself instead of spectral features to calibrate a spectrograph. The primary advantage of such a calibration is that any broad-spectrum light source such as the sky or an incandescent bulb is suitable. This method allows for calibration using the full optical pathway of the instrument instead of incorporating separate calibration equipment that may introduce errors. This paper focuses on the potential for color calibration in the field of radial velocity astronomy, in which instruments must be finely calibrated for long periods of time to detect tiny Doppler wavelength shifts. This paper demonstrates that color sensors have the potential to provide calibration with greatly reduced complexity. The analysis and simulation of a new method of spectral calibration using color sensors has shown the potential to provide calibration with reduced instrumentation and simplified processing. Calibration is performed with no specialized light source and no optics other than those used for the scientific observation. The method is limited by the quality of the initial characterization of the sensor’s color filters. Recommendations for experimentation using either color sensors or color filters have been presented. Positive results from experimentation may lead to a more widely available means of calibrated spectroscopy for radial velocity studies or in other fields where simplicity and compactness is
a. effective. b. visible c. superficial d. critical
a. effective. b. visible c. superficial d. critical
Q2. arXiv:1801.01889 [astro-ph.HE]: 5 Jan 2018: MNRAS 000, 1–16 (2017) Preprint 9 January 2018: Multiband counterparts of two eclipsing ultra-luminous X-ray sources in M51: R. Urquhart, et al., International Centre for Radio Astronomy Research, Curtin University, GPO Box U1987, Perth, WA 6845, Australia. ABSTRACT We present the discovery and interpretation of ionized nebulae around two ultra-luminous X-ray sources in M51; both sources share the rare property of showing X-ray eclipses by their companion stars, and are therefore prime targets for follow-up studies. Using archival Hubble Space Telescope images, we found an elongated, 100-pc-long emission-line structure associated with one X-ray source (CXOM51 J132940.0+471237; ULX-1 for simplicity), and a more circular, ionized nebula at the location of the second source (CXOM51 J132939.5+471244; ULX-2 for simplicity). We observed both nebulae with the Large Binocular Telescope’s Multi-Object Double Spectrograph. From our analysis of the optical spectra, we argue that the gas in the ULX-1 bubble is shock-ionized, consistent with the effect of a jet with a kinetic power of≈2×10^39 erg s−1. Additional X-ray photo-ionization may also be present, to explain the strength of high-ionization lines such as He ii λ4686 and [Ne v] λ3426. On the other hand, the emission lines from the ULX-2 bubble are typical for photoionization by normal O stars suggesting that the nebula is actually an H ii region not physically related to the ULX but is simply a chance alignment. From archival Very Large Array data, we also detect spatially extended, steep-spectrum radio emission at the location of the ULX-1 bubble (consistent with its jet origin), but no radio counterpart for ULX-2 (consistent with the lack of shock-ionized gas around that ........).
a. λ3426 b. source. c. galaxy d. X-ray source
Q3. arXiv:1801.06211 [astro-ph.GA]: The Enigmatic (Almost) Dark Galaxy Coma P: The Atomic Interstellar Medium. Catherine Ball et al., (Submitted on 18 Jan 2018). We present new high-resolution HI spectral line imaging of Coma P, the brightest HI source in the system HI 1232+20. ABSTRACT: This extremely low surface brightness galaxy was first identified in the ALFALFA survey as an "(Almost) Dark" object: a clearly extragalactic HI source with no obvious optical counterpart in existing optical survey data (although faint ultraviolet emission was detected in archival GALEX imaging). Using a combination of data from the Westerbork Synthesis Radio Telescope and the Karl G. Jansky Very Large Array, we investigate the HI morphology and kinematics at a variety of physical scales. The HI morphology is irregular, reaching only moderate maxima in mass surface density (peak σHI∼10 M⊙ pc−2). Gas of lower surface brightness extends to large radial distances, with the HI diameter measured at 4.0±0.2kpc inside the 1 M⊙ pc−2 level. We quantify the relationships between HI gas mass surface density and various types of star formation by considering GALEX far ultraviolet observations and Hα non-detections. We describe Coma P's complex HI kinematics using spatially resolved position-velocity analysis and three-dimensional modelling. Both methods of analysis suggest that Coma P's kinematics show signatures of either the collision of two HI disks or a significant infall event. Coma P is just consistent (within 3σ) with the known MHI -- DHI scaling relation. It is either too large for its HI mass, has too low an HI mass for its HI size, or the two HI components artificially extend its HI size. Coma P lies within the empirical scatter at the faint end of the baryonic Tully--Fisher relation, although the complexity of the HI dynamics complicates the interpretation. The collective HI characteristics of Coma P make it unusual among known galaxies in the nearby
a. universe b. galaxy c. star d. optical universe.
Q4. arXiv:1801.06236[astro-ph.GA]: The complex kinematics of rotating star clusters in a tidal field: Maria Tiongco, Enrico Vesperini, Anna Lisa Varri, (Submitted on 18 Jan 2018). We broaden the investigation of the dynamical properties of tidally perturbed, rotating star clusters by relaxing the traditional assumptions of coplanarity, alignment, and synchronicity between the internal and orbital angular velocity vector of their initial conditions. We show that the interplay between the internal evolution of these systems and their interaction with the external tidal field naturally leads to the development of a number of evolutionary features in their three-dimensional velocity space, including a precession and nutation of the global rotation axis and a variation of its orientation with the distance from the cluster centre. In some cases, such a radial variation may manifest itself as a counter-rotation of the outermost regions relative to the inner ones. The projected morphology of these systems is characterized by a non-monotonic ellipticity profile and, depending on the initial inclination of the rotation axis, it may also show a twisting of the projected isodensity contours. These results provide guidance in the identification of non-trivial features which may emerge in upcoming investigations of star cluster kinematics and a dynamical framework to understand some of the complexities already hinted by recent observational studies. Such a degree of generality suggests that these properties might be widespread in globular clusters (with the exception of the dynamically oldest clusters that may have completely lost any memory of the initial rotation). Our study provides guidance in the identification of non-trivial features which may emerge in up coming investigations of star cluster kinematics and a dynamical framework to understand some of the complexities already hinted by recent observational
a. discoveries b. hypothesis. c. studies d. findings.
Q5. arXiv:1803.01898 [physics.app-ph]:Fiber-shaped lithium-ion batteries with metallic electrodes; H. Qu, X. Lu, M. Skorobogatiy, (Submitted on 5 Mar 2018), ABSTRACT: We have demonstrated a fiber lithium ion battery (LIB) fabricated by co-twisting a LiFePO4 composite-coated copper wire (cathode) together with an aluminum wire (anode). An all-solid LiPF6 composite layer functioning both as the electrolyte and battery separator is deposited onto the two electrode wires before twisting. To characterize the electrochemical properties of the battery, charge-discharge tests with different C-rates are performed. The fiber LIB has an open-circuit voltage of ~3.4 V, and the typical specific capacity is found to be ~87 mAh g^-1 at 0.5 C charge-discharge rate. Besides, the proposed battery has a Coulombic efficiency of more than 82% throughout all the charge-discharge tests. We also find that bending of the fiber battery has insignificant influence on the battery electrochemical properties. Within this strategic project, we reported an all-solid, fiber LIB that has a LiFePO4 composite athode wire twisted with an aluminum anode wire. The cathode wire is fabricated by depositing a LiFePO4 composite layer and a LiPF6-composite layer on a copper-wire substrate using a dip-and-dry method. The anode wire is fabricated by depositing the LiPF6-composite layer on an aluminum wire also using the dip-and-dry method. Then, the two electrode wires are twisted together using a home-made jig to constitute a full LIB. The proposed LIB shows an open-circuit voltage of ~3.3 V. The experimental results of the charge-discharge tests suggest that the battery has a specific capacity of ~87 mAhg^-1 at 0.5 C rate. Moreover, the battery could retain well its capacity after intensive cyclic charge-discharge operation. During all the battery operation, the coulombic efficiency of the battery remains above ~82%. We also find that the electrochemical properties of the fiber battery is virtually independent of bending actions. The fabrication of the battery is extremely simple and economic, and all of the battery component materials are inexpensive and commercially available. Compared to the majority of currently existing fiber- (cable-) shaped LIBs that utilize electrolytes based on liquid organic solutions, the proposed LIB is much more advantageous for wearable applications thanks to its all-solid
a. operations b. structure c. samples d. methods
a. operations b. structure c. samples d. methods
Q6. arXiv:1801.06246 [astro-ph.HE]: Kicks of magnetized strange quark stars induced by anisotropic emission of neutrinos. Alejandro Ayala, D. Manreza Paret, A. Pérez Martínez, Gabriella Piccinelli, Angel Sánchez, Jorge S. Ruíz Montaño. (Submitted on 18 Jan 2018). ABSTRACT: We study the anisotropic neutrino emission from the core of neutron stars induced by the star's magnetic field. We model the core as made out of a magnetized ideal gas of strange quark matter and implement the conditions for stellar equilibrium in this environment. The calculation is performed without resorting to analytical simplifications and for temperature, density and magnetic field values corresponding to typical conditions for a neutron star's evolution. The anisotropic neutrino emission produces a rocket effect that contributes to the star's kick velocity. We find that the computed values for the kick velocity lie within the range of the observed values, reaching velocities of the order of 1000 km s^−1 for magnetic fields between 10^15 − 10^18 G and radii of 20 to 5 km, respectively. For typical values of densities an temperatures, the inclusion of stellar equilibrium conditions and the dependence of all thermodynamical quantities on the magnetic field allow us to obtain a more realistic model to describe the kick velocity mechanism and cover a wider range of magnetic field values. DETAILS: Our result for the kick velocity tends asymptotically to the one where the ideal condition of χ = 1 was used, implying very high magnetic fields. The anisotropic neutrino emission as a source of NS’s kick velocities faces many challenges. In thermal equilibrium no asymmetry can be produced, even in the presence of parity-violating processes, such as the one considered in the present work. Therefore, the process is more significant during stages where the NS’s core is out of equilibrium, such as the very early times after the NS’s birth or during posterior phase transitions of quark matter inside the core. The problem can be translated to the small neutrino mean free path within the thermalized matter. It should be noted however that the magnetic field effect on the interaction rate and thus on the mean free path has not yet been calculated and that, when the magnetic field strength is high, a strong modification of such interaction may be expected. Studies aiming to incorporate non-trivial effects of magnetic fields have been performed. Other effects such as the magnetic field induced anisotropic pressures should be consistently accounted for the study of the structural and polarization properties of a strongly magnetized stellar object. In particular, the effect of a smaller longitudinal pressure than the transverse one, produces the appearance of a longitudinal instability of the NS’s matter when the magnetic field exceeds some critical
a. value b. magnitude c. property d. dimension.
|
Q7. arXiv:1801.07253 [astro-ph.GA]: Gravity drives the evolution of infrared dark hubs: JVLA observations of SDC13: Gwenllian M. Williams, Nicolas Peretto, Adam Avison, Ana Duarte-Cabral, Gary A. Fuller: (Submitted on 22 Jan 2018): Converging networks of interstellar filaments i.e. hubs, have been recently linked to the formation of stellar clusters and massive stars. The goal is to study the kinematic and density structure of the SDC13 hub at high angular resolution to determine what drives its evolution and fragmentation. We have mapped SDC13, a 1000Msun infrared dark hub, in NH3(1,1) and NH3(2,2) emission lines, with both the JVLA and GBT down to 0.07pc. The mass-per-unit-lengths of all four hub filaments are thermally super-critical, consistent with the presence of tens of gravitationally bound cores along them. These cores exhibit regular separation of 0.37 +/- 0.16 pc suggesting gravitational instabilities running along these super-critical filaments are responsible for their fragmentation. The observed local increase of the dense gas velocity dispersion towards starless cores is believed to be a consequence of such fragmentation process. We see velocity gradient peaks towards 63% of the cores as expected during the early stages of filament fragmentation. The most massive cores are located at the filament junctions, where the velocity dispersion is the largest. We interpret this as the result of the hub morphology generating the largest acceleration gradients near the hub centre. We propose a scenario for the evolution of the SDC13 hub in which filaments first form as post-shock structures in a supersonic turbulent flow. Then gravity takes over and starts shaping the evolution of the hub, both fragmenting filaments and pulling the gas towards the centre of the gravitational well. By doing so, gravitational energy is converted into kinetic energy in both local (cores) and global (hub centre) potential well minima. Furthermore, the generation of larger gravitational acceleration gradients at the filament junctions promotes the formation of more massive
a. dumps b. cores c. triangles d. clusters.
Q8.arXiv:1801.07277 [astro-ph.HE]: A Multi-Component Model for the Observed Astrophysical Neutrinos: Andrea Palladino, Walter Winter: (Submitted on 22 Jan 2018): We propose a multi-component model for the observed diffuse neutrino flux, including the residual atmospheric backgrounds, a Galactic contribution (such as from cosmic ray interactions with gas), an extra-galactic contribution from pp interactions (such as from starburst galaxies) and a hard extragalatic contribution from photo-hadronic interactions at the highest energies (such as from Tidal Disruption Events or Active Galactic Nuclei). We demonstrate that this model can address the key problems of astrophysical neutrino data, such as the different observed spectral indices in the high-energy starting and through-going muon samples, a possible anisotropy due to Galactic events, the non-observation of point sources, and the constraint from the extragalatic diffuse gamma-ray background. Furthermore, the recently observed muon track with a deposited energy of 4.5 PeV might be interpreted as evidence for the extragalactic photo-hadronic contribution. We perform the analysis based on the observed events instead of the unfolded fluxes by computing the probability distributions for the event type and reconstructed neutrino energy. As a consequence, we give the probability to belong to each of these astrophysical components on an event-to-event basis. We conclude that a self-consistent description of the observed diffuse neutrino flux requires multiple contributions to the diffuse astrophysical neutrino flux, and we have drawn a self-consistent picture describing these contributions by their generic characteristics in terms of spectrum, sky distribution and neutrino production mechanism. Our model solves the key challenges in current neutrino data, including multi-messenger constraints. In the future, it may be helpful to obtain neutrino constraints on the individual contributions in addition to the total spectrum to disentangle the contributions from different source
a. categories b. considerations c. variants. d. classes.
Q9. arxiv.org/abs/1801.07437: CANDIDATE WATER VAPOR LINES TO LOCATE THE H2O SNOWLINE THROUGH HIGH-DISPERSION SPECTROSCOPIC OBSERVATIONS. III. SUB-MILLIMETER H216O AND H218O LINES: Shota Notsu, et al., Department of Astronomy, Graduate School of Science, Kyoto University, Kitashirakawa-Oiwake-cho, Sakyo-ku, Kyoto 606-8502, Japan; (Received August 9, 2017; Revised January 20, 2018; Accepted January 22, 2018, in The Astrophysical Journal): ABSTRACT: In this paper, we extended our previous work (papers I and II, Notsu et al. 2016, 2017) on using the profiles of ortho-H216O lines for tracing the location of the H2O snowline in a Herbig Ae disk and a T Tauri disk, to inclide sub-millimeter para-H216O and ortho- and paraH218O lines. The number densities of the para-H216O molecules are around one third smaller than that of ortho-H216O, thus the para-H216O line can trace deeper into the disk than the ortho-H216O lines. Since the number densities of H218O molecules are around 560 times smaller than those of H216O, they can probe deeper into the disk than the H216O lines (down to z = 0) and thus they are better candidates for detecting water emission within the H2O snowline at the disk midplane. If the dust opacity of the disk is much larger than that adopted in our disk model, the H216O lines and lines with longer wavelengths are better candidates for submillimeter detection of the inner water reservoir. This is because the dust opacity becomes larger as the line frequency increases. In addition, the temperature is higher as the disk height is higher and thus the temperature around τul ∼ 1 of H216O lines is higher than those of H218O lines. Therefore, the line intensities are larger. in the case of H216O lines, compared with the case of H218O lines. The values of the Einstein A coefficients of sub-millimeter candidate water lines tend to be smaller (typically <10−4 s−1) than infrared candidate water lines (see paper II). Thus, in the case of sub-millimeter candidate water lines, the local intensity from the outer optically thin region in the disk is around 104 times smaller than that in infrared candidate water line cases (see paper II). Therefore, in the case of sub-millimeter lines, especially for H218O and para-H216O, lines with relatively smaller upper state energies (∼ a few 100 K) can also be used to trace the location of the water snowline. The values of candidate water line fluxes of the T Tauri disk are around 1 − 5 × 102 smaller than those of the Herbig Ae disk, because the location of the H2O snowline in the T Tauri disk exists at a smaller radius from the star than that in the Herbig Ae disk. There are several candidate water lines that trace the hot water gas inside H2O snowline in ALMA Bands 5−10. The successful detection of candidate water lines in Herbig Ae disks and younger T Tauri disks could be achieved with current ALMA capabilities. In this paper, we extended our previous work (papers I and II, Notsu et al. 2016, 2017) on using the profiles of ortho-H216O lines for tracing the location of the H2O snowline in a Herbig Ae disk and a T Tauri disk, to inclide sub-millimeter para-H216O and ortho- and paraH218O lines. The number densities of the para-H216O molecules are around one third smaller than that of ortho-H216O, thus the para-H216O line can trace deeper into the disk than the ortho-H216O lines. Since the number densities of H218O molecules are around 560 times smaller than those of H216O, they can probe deeper into the disk than the H216O lines (down to z = 0) and thus they are better candidates for detecting water emission within the H2O snowline at the disk midplane. If the dust opacity of the disk is much larger than that adopted in our disk model, the H216O lines and lines with longer wavelengths are better candidates for submillimeter detection of the inner water reservoir. This is because the dust opacity becomes larger as the line frequency increases. In addition, the temperature is higher as the disk height is higher and thus the temperature around τul ∼ 1 of H216O lines is higher than those of H218O lines. Therefore, the line intensities are larger. in the case of H216O lines, compared with the case of H218O lines. The values of the Einstein A coefficients of sub-millimeter candidate water lines tend to be smaller (typically <10−4 s−1) than infrared candidate water lines (see paper II). Thus, in the case of sub-millimeter candidate water lines, the local intensity from the outer optically thin region in the disk is around 104 times smaller than that in infrared candidate water line cases (see paper II). Therefore, in the case of sub-millimeter lines, especially for H218O and para-H216O, lines with relatively smaller upper state energies (∼ a few 100 K) can also be used to trace the location of the water snowline. The values of candidate water line fluxes of the T Tauri disk are around 1 − 5 × 10^2 smaller than those of the Herbig Ae disk, because the location of the H2O snowline in the T Tauri disk exists at a smaller radius from the star than that in the Herbig Ae disk. There are several candidate water lines that trace the hot water gas inside H2O snowline in ALMA Bands 5−10. The successful detection of candidate water lines in Herbig Ae disks and younger T Tauri disks could be achieved with current ALMA
a. lines b. capabilities c. assurance d. capacities.
Q10. arxiv.org/abs/1801.07592: (Submitted on 21 Jan 2018): The 1916 PhD Thesis of Johannes Droste and the Discovery of Gravitational Repulsion Charles H. McGruder III and B. Wieb VanDerMeer Western Kentucky University: Abstract One of the biggest mysteries of astrophysics is the question of how highly energetic particles in relativistic jets and cosmic rays are accelerated. Recently, it has been suggested that gravitational repulsion is the mechanism responsible for these phenomena. The little known concept of gravitational repulsion was first introduced by Johannes Droste in his Ph.D. thesis submitted to H.A. Lorentz in 1916. It was written in Dutch. We provide a translation. Introduction We observe highly energetic particles in the universe and we do not know how these particles are accelerated. We observe relativistic jets with speeds up to 0.8c (pulsar IGR J11014-6103) and apparent superluminal sources, which must have v > 0.707c. In addition we observe cosmic rays up to 1020 eV, whereby the most powerful manmade accelerator (Large Hadron Collider) can achieve proton-proton collisions of only 1012 eV. It has been suggested that the particles in relativistic jets (Gariel et al. 2016 and 2017) and cosmic ray particles (McGruder, 2017) are accelerated to high energies via gravitational repulsion. However, the concept of gravitational repulsion is not widely known even though as far back as 1916 Johannes Droste submitted a PhD thesis on general relativity to his advisor H.A. Lorentz in which he calculated the motion of a particle in what we call today the Schwarzschild field and found that highly relativistic particles experience gravitational repulsion. Thus, his thesis written in Dutch and never before translated contains the discovery of gravitational repulsion. Einstein was familiar with Droste’s thesis, saying it is “good” (Schilling 2018). In 1687 Newton published his universal law of gravitation, which states that the gravitational force is always attractive. This law is based on our terrestrial experience with slowly moving bodies (v << c). General Relativity (also referred to as Einstein’s Theory of Gravitation) is valid not just for slowly moving bodies but also for those with relativistic velocities. After Einstein completed his formulation of General Relativity on 25 November 1915 (Janssen and Renn 2015), Johannes Droste on 8 December 1916 submitted his PhD thesis in Dutch containing the discovery that particles of sufficiently high velocity in a spherical symmetric gravitational field of a point mass according to Einstein’s theory do not experience attraction rather repulsion. Fifteen days later on 23 December 1916 Hilbert submitted to the Society of Sciences in Göttingen a manuscript, which proved that Einstein’s theory contains the concept of gravitational repulsion. Hilbert’s work was published in 1917. Also in 1917 Droste published an abbreviated account of his thesis in English, which contained the concept of gravitational repulsion. In 1922 Bauer independently discovered this effect. Thus, Droste was the first to publish on gravitational repulsion in Einstein’s theory of Gravitation and it is therefore historically incorrect to call the phenomenon “Hilbert Repulsion” as some authors do. (Loinger and Marsico 2009a, 2009b, 2010 and Célérier et al. 2017). Section 42 contains the discovery of gravitational repulsion discovered in
a. 2018 b. 2000 c. 1916 d. 1956.
Q11. arXiv:1801.07713 [cond-mat.mes-hall]: Anomalous Hall effect in magnetized graphene: intrinsic and extrinsic transport mechanisms approaching the quantized regime: Manuel Offidani, Aires Ferreira: (Submitted on 23 Jan 2018):ABSTRACT: We present a unified theory of the anomalous Hall effect (AHE) in magnetized graphene sheets in the presence of dilute disorder. The analytical study of Berry curvature and transport coefficients in a 4-band Dirac model [2 (spin) ×2 (pseudo-spin)] unveils a delicate balance between intrinsic and extrinsic contributions owing to the skyrmionic spin texture of magnetic Dirac bands. We show that the anomalous Hall conductivity changes sign when the Fermi energy approaches the topological gap as result of competing spin Lorentz forces. The predicted effect foreruns the quantum anomalous Hall regime and allows estimation of proximity spin-orbit strength directly from a Hall measurement. Our findings are relevant to outline a systematic route towards the demonstration of novel topological insulating phases in magnetized Dirac fermion systems. The predictions of topological insulating phases in 2D Dirac systems have triggered numerous efforts aimed to realize topological fermions in ultra-clean graphene heterostructures. To guide such efforts, it is essential to characterize the response of magnetized Dirac systems to external fields in the presence of disorder corrections, as the current work shows. In this respect, our unified theory, incorporating extrinsic and intrinsic contributions to the anomalous Hall effect on equal footing, and unveiling a skew-scattering mechanism modulated by the rich spin texture of magnetic Dirac states—constitutes a major step towards the understanding of transport phenomena in graphene–magnetic insulator
a. fields b. hetero-structures c. structures d. transformations
Q12. arXiv:1801.07776 [cond-mat.mes-hall]: Long-term drift of Si-MOS quantum dots with intentional donor implants: Martin Rudolph, Bahman Sarabi, Roy Murray, Malcolm S. Carrol, Neil M. Zimmerman: (Submitted on 23 Jan 2018): ABSTRACT:Charge noise can be detrimental to the operation of quantum dot (QD) based semiconductor qubits. We study the low-frequency charge noise by charge offset drift measurements for Si-MOS devices with intentionally implanted donors near the QDs. We show that the MOS system exhibits non-equilibrium drift characteristics in the form of transients and discrete jumps that are not dependent on the properties of the donor implants. The equilibrium charge noise indicates a 1/f noise dependence, and a noise strength as low as 1 μeV/√Hz, comparable to that reported in more model GaAs and Si/SiGe systems (which have also not been implanted). We demonstrate that implanted qubits, therefore, can be fabricated without detrimental effects on long-term drift or 1/f noise. To summarize, we suggest that expressing the charge offset drift in energy units is particularly useful in the contexts of i) dephasing in qubits and/or ii) read-out with a SET or point contact that has a cusp-like response, where the width of the cusp is set by an energy scale. In addition, units of energy will provide a natural comparison between charge noise and other mechanisms that can coupled to the qubit system, such as phonons16. We suggest that expressing the drift in charge units is useful in discussing i) digital integration of multiple qubits and ii) comparing the behavior of different devices, especially from different groups. The characteristics of the drift observed (Fig. 2) in the devices can be separated into three categories. 1. A transient relaxation. This can occur after a thermal shock such as a cooldown. Measurements were performed within a few hours of cooldown for devices DA, DE, and DF, and the chemical potential position initially follows a quasi-exponential relaxation until the saturation after about 2 days. Regions of thermally induced transients are indicated by ( ). Transient relaxation also occurs after a non-equilibrium charge reconfiguration due to an external voltage shock. This is evident in device DB where the spikes observed at hours 24, 48, and 72 were induced by work being performed near the cryostat. Device DE has two shock events as well. The relaxation here is also on the order of a day. Electrostatically induced transients are indicated by ( ). 2. Isolated discrete jumps. Reconfiguration of isolated charges in the device can induce a chemical potential shift with no subsequent relaxation. Two such events are visible in device DB at hours 75 and 110. Devices DC, DE, and DR also display this behavior, which are indicated by (F). 3. Local fluctuations about a stable mean value are present in all measurements and originate from the charge noise induced by remote charge reconfigurations and gate noise. Examples of these are highlighted in the figure. The size and spectrum of these local fluctuations measure the intrinsic equilibrium charge noise of the system. For device DA, there exists a dominant slow two-level-fluctuator, while the equilibrium fluctuations for the other devices are on faster time scales. Device DD shows significantly different behavior than the others, with a slow, non-monotonic drift dominating the charge offset
Q10. arxiv.org/abs/1801.07592: (Submitted on 21 Jan 2018): The 1916 PhD Thesis of Johannes Droste and the Discovery of Gravitational Repulsion Charles H. McGruder III and B. Wieb VanDerMeer Western Kentucky University: Abstract One of the biggest mysteries of astrophysics is the question of how highly energetic particles in relativistic jets and cosmic rays are accelerated. Recently, it has been suggested that gravitational repulsion is the mechanism responsible for these phenomena. The little known concept of gravitational repulsion was first introduced by Johannes Droste in his Ph.D. thesis submitted to H.A. Lorentz in 1916. It was written in Dutch. We provide a translation. Introduction We observe highly energetic particles in the universe and we do not know how these particles are accelerated. We observe relativistic jets with speeds up to 0.8c (pulsar IGR J11014-6103) and apparent superluminal sources, which must have v > 0.707c. In addition we observe cosmic rays up to 1020 eV, whereby the most powerful manmade accelerator (Large Hadron Collider) can achieve proton-proton collisions of only 1012 eV. It has been suggested that the particles in relativistic jets (Gariel et al. 2016 and 2017) and cosmic ray particles (McGruder, 2017) are accelerated to high energies via gravitational repulsion. However, the concept of gravitational repulsion is not widely known even though as far back as 1916 Johannes Droste submitted a PhD thesis on general relativity to his advisor H.A. Lorentz in which he calculated the motion of a particle in what we call today the Schwarzschild field and found that highly relativistic particles experience gravitational repulsion. Thus, his thesis written in Dutch and never before translated contains the discovery of gravitational repulsion. Einstein was familiar with Droste’s thesis, saying it is “good” (Schilling 2018). In 1687 Newton published his universal law of gravitation, which states that the gravitational force is always attractive. This law is based on our terrestrial experience with slowly moving bodies (v << c). General Relativity (also referred to as Einstein’s Theory of Gravitation) is valid not just for slowly moving bodies but also for those with relativistic velocities. After Einstein completed his formulation of General Relativity on 25 November 1915 (Janssen and Renn 2015), Johannes Droste on 8 December 1916 submitted his PhD thesis in Dutch containing the discovery that particles of sufficiently high velocity in a spherical symmetric gravitational field of a point mass according to Einstein’s theory do not experience attraction rather repulsion. Fifteen days later on 23 December 1916 Hilbert submitted to the Society of Sciences in Göttingen a manuscript, which proved that Einstein’s theory contains the concept of gravitational repulsion. Hilbert’s work was published in 1917. Also in 1917 Droste published an abbreviated account of his thesis in English, which contained the concept of gravitational repulsion. In 1922 Bauer independently discovered this effect. Thus, Droste was the first to publish on gravitational repulsion in Einstein’s theory of Gravitation and it is therefore historically incorrect to call the phenomenon “Hilbert Repulsion” as some authors do. (Loinger and Marsico 2009a, 2009b, 2010 and Célérier et al. 2017). Section 42 contains the discovery of gravitational repulsion discovered in
a. 2018 b. 2000 c. 1916 d. 1956.
Q11. arXiv:1801.07713 [cond-mat.mes-hall]: Anomalous Hall effect in magnetized graphene: intrinsic and extrinsic transport mechanisms approaching the quantized regime: Manuel Offidani, Aires Ferreira: (Submitted on 23 Jan 2018):ABSTRACT: We present a unified theory of the anomalous Hall effect (AHE) in magnetized graphene sheets in the presence of dilute disorder. The analytical study of Berry curvature and transport coefficients in a 4-band Dirac model [2 (spin) ×2 (pseudo-spin)] unveils a delicate balance between intrinsic and extrinsic contributions owing to the skyrmionic spin texture of magnetic Dirac bands. We show that the anomalous Hall conductivity changes sign when the Fermi energy approaches the topological gap as result of competing spin Lorentz forces. The predicted effect foreruns the quantum anomalous Hall regime and allows estimation of proximity spin-orbit strength directly from a Hall measurement. Our findings are relevant to outline a systematic route towards the demonstration of novel topological insulating phases in magnetized Dirac fermion systems. The predictions of topological insulating phases in 2D Dirac systems have triggered numerous efforts aimed to realize topological fermions in ultra-clean graphene heterostructures. To guide such efforts, it is essential to characterize the response of magnetized Dirac systems to external fields in the presence of disorder corrections, as the current work shows. In this respect, our unified theory, incorporating extrinsic and intrinsic contributions to the anomalous Hall effect on equal footing, and unveiling a skew-scattering mechanism modulated by the rich spin texture of magnetic Dirac states—constitutes a major step towards the understanding of transport phenomena in graphene–magnetic insulator
a. fields b. hetero-structures c. structures d. transformations
Q12. arXiv:1801.07776 [cond-mat.mes-hall]: Long-term drift of Si-MOS quantum dots with intentional donor implants: Martin Rudolph, Bahman Sarabi, Roy Murray, Malcolm S. Carrol, Neil M. Zimmerman: (Submitted on 23 Jan 2018): ABSTRACT:Charge noise can be detrimental to the operation of quantum dot (QD) based semiconductor qubits. We study the low-frequency charge noise by charge offset drift measurements for Si-MOS devices with intentionally implanted donors near the QDs. We show that the MOS system exhibits non-equilibrium drift characteristics in the form of transients and discrete jumps that are not dependent on the properties of the donor implants. The equilibrium charge noise indicates a 1/f noise dependence, and a noise strength as low as 1 μeV/√Hz, comparable to that reported in more model GaAs and Si/SiGe systems (which have also not been implanted). We demonstrate that implanted qubits, therefore, can be fabricated without detrimental effects on long-term drift or 1/f noise. To summarize, we suggest that expressing the charge offset drift in energy units is particularly useful in the contexts of i) dephasing in qubits and/or ii) read-out with a SET or point contact that has a cusp-like response, where the width of the cusp is set by an energy scale. In addition, units of energy will provide a natural comparison between charge noise and other mechanisms that can coupled to the qubit system, such as phonons16. We suggest that expressing the drift in charge units is useful in discussing i) digital integration of multiple qubits and ii) comparing the behavior of different devices, especially from different groups. The characteristics of the drift observed (Fig. 2) in the devices can be separated into three categories. 1. A transient relaxation. This can occur after a thermal shock such as a cooldown. Measurements were performed within a few hours of cooldown for devices DA, DE, and DF, and the chemical potential position initially follows a quasi-exponential relaxation until the saturation after about 2 days. Regions of thermally induced transients are indicated by ( ). Transient relaxation also occurs after a non-equilibrium charge reconfiguration due to an external voltage shock. This is evident in device DB where the spikes observed at hours 24, 48, and 72 were induced by work being performed near the cryostat. Device DE has two shock events as well. The relaxation here is also on the order of a day. Electrostatically induced transients are indicated by ( ). 2. Isolated discrete jumps. Reconfiguration of isolated charges in the device can induce a chemical potential shift with no subsequent relaxation. Two such events are visible in device DB at hours 75 and 110. Devices DC, DE, and DR also display this behavior, which are indicated by (F). 3. Local fluctuations about a stable mean value are present in all measurements and originate from the charge noise induced by remote charge reconfigurations and gate noise. Examples of these are highlighted in the figure. The size and spectrum of these local fluctuations measure the intrinsic equilibrium charge noise of the system. For device DA, there exists a dominant slow two-level-fluctuator, while the equilibrium fluctuations for the other devices are on faster time scales. Device DD shows significantly different behavior than the others, with a slow, non-monotonic drift dominating the charge offset
| a. drift b. measurement c. behaviour d. scenario. |
Q13. arXiv:1801.07974 [cond-mat.mes-hall]: ABSTRACT: Excitonic structure of the optical conductivity in MoS2 : monolayers: Emilia Ridolfi, Caio H. Lewenkopf, Vitor M. Pereira: (Submitted on 24 Jan 2018): We investigate the excitonic spectrum of MoS2 monolayers and calculate its optical absorption properties over a wide range of energies. Our approach takes into account the anomalous screening in two dimensions and the presence of a substrate, both cast by a suitable effective Keldysh potential. We solve the Bethe-Salpeter equation using as a basis a Slater-Koster tight-binding model parameterized to fit ab initio MoS2 band structure calculations. The resulting optical conductivity is in good quantitative agreement with existing measurements up to ultraviolet energies. We establish that the electronic contributions to the C excitons arise not from states in the vicinity of the Γ point, but from a set of k -points over extended portions of the Brillouin zone. Our results reinforce the advantages of approaches based on effective models to expeditiously explore the properties and tunability of excitons in TMD systems. SUMMARY:We revisited the problem of calculating the excitonic spectrum in the MoS2 monolayer. It has been shown that many-body effects strongly restructure the optical absorption spectrum over an unusually large range of energies in comparison with the single-particle picture. Our approach accounts for the anomalous screening in two dimensions and for the presence of a substrate, both cast by a suitable effective Keldysh potential. We solve the Bethe-Salpeter equation for the interacting electron-hole excitations by using a Slater-Koster tight-binding model parametrized to fit the calculated first-principles band structure of the material. The optical conductivity that emerges captures with good accuracy both the shape and absolute magnitude of the experimental data. Seeing that our result captures well the experimental spectrum up to ∼3eV, we relied on the predictions of this model to investigate the effects and characteristics of the so-called C excitons. Notably, we explicitly showed that they arise from electronic contributions localized in thin rings centered at the K point. The interplay between the texture of the excitonic wavefunctions and the one-electron dipole matrix elements is responsible for the massive transfer of spectral weight seen in the conductivity when compared with results at the one-electron level. Our results also suggest a cautionary word when it comes to effective mass descriptions of the MoS2 band structure, especially if the aim is to describe the optical excitations in the vicinity of EC. In this case, a model that captures only the band structure at the Γ point will be certainly insufficient for that. Throughout our analysis, we presented results obtained with two different tight-binding descriptions of the underlying single-particle band structure. This affords a perspective over some aspects that are robust in this approach and others that depend on fine details of the parameterization. Overall, the accuracy of our results based on the SK model developed in by E. Ridolfi et al., , , vividly supports the use of effective models to expeditiously explore the properties of excitons in 2D materials. This work shows it to be a reliable strategy, provided that the starting Hamiltonian faithfully describes the quasiparticle corrected band structure. These approaches are orders of magnitude faster in CPU time than complete first principles solutions of the BSE. Such an advantage facilitates properly addressing the optical response of MoS2 at energies around the C excitons, where a fine sampling of the k-space is necessary. We believe that, due to their intrinsic flexibility to model reliably a variety of conditions such as hetero-structures, disorder and strain, effective models open the path for a more comprehensive investigation of the optical properties of TMDs where interaction effects play a fundamental
a. step b. role c. rule. d. manifestation.
Q14. arXiv:1801.08057 [quant-ph]: Energy-temperature uncertainty relation in quantum thermodynamics: Harry J. D. Miller, Janet Anders: (Submitted on 24 Jan 2018): Much like Heisenberg's uncertainty principle in quantum mechanics, there exists the thermodynamic uncertainty relation in classical statistical mechanics that limits simultaneous estimations of energy and temperature for a system in equilibrium. However, for nanoscale systems deviations from standard thermodynamics arise due to non-negligible interactions with the environment. Here we include interactions and, using quantum estimation theory, derive a generalised thermodynamic uncertainty relation valid for classical and quantum systems at all coupling strengths. We show that the non-commutativity between the system's state and its effective energy operator gives rise to additional quantum fluctuations that increase the uncertainty in temperature and modify the heat capacity. Surprisingly, these quantum fluctuations are described by the average Wigner-Yanase-Dyson skew information, a quantity intimately connected to measures of coherence. For temperature estimation we demonstrate that the optimal signal-to-noise ratio is constrained not only by the heat capacity, but an additional dissipative term arising from the non-negligible interactions. Practically this will inform the design of optimal nanoscale thermometers. On the fundamental side the results shed light on the interplay between classical and non-classical fluctuations in quantum thermodynamics. Details: Bohr suggested that there should exist a form of complementarity between temperature and energy in thermodynamics similar to that of position and momentum in quantum theory. His reasoning was that in order to assign a definite temperature T to a system it must be brought in contact with a thermal reservoir, in which case the energy U of the system fluctuates due to exchanges with the reservoir. On the other hand, to assign a sharp energy to the system it must be isolated from the reservoir, rendering the system’s temperature T uncertain. Based on this heuristic argument Bohr conjectured the thermodynamic uncertainty relation: ∆U ∆β ≥ 1, (1) with β = (kBT)−1 the inverse temperature. The presented approach opens up opportunities for exploring the intermediate regime between the limiting cases of standard thermodynamics with negligible interactions and those where correlations play a prominent role. The results establish a new connection between abstract measures of quantum information theory, such as the quantum Fisher information and skew information, and a material’s effective thermodynamic properties. This provides a starting point for future investigations into nanoscale thermodynamics, extending into the regime where the weak coupling assumption is not
a. correct b. genuine c. exemplary d. justified.
Q15. arXiv:1801.07486 [cond-mat.mtrl-sci]: Direct observation of strain-induced orbital valence band splitting in HfSe2 by sodium intercalation: T. Eknapakul, I. Fongkaew, S. Siriroj, W. Jindata, S. Chaiyachad, S.-K. Mo, S. Thakur, L. Petaccia, H. Takagi, S. Limpijumnong, W. Meevasana: (Submitted on 23 Jan 2018): ABSTRACT: By using angle-resolved photoemission spectroscopy (ARPES), the variation of the electronic structure of HfSe2 has been studied as a function of sodium intercalation. We observe how this drives a band splitting of the p-orbital valence bands and a simultaneous reduction of the indirect band gap by values of up to 400 and 280 meV respectively. Our calculations indicate that such behaviour is driven by the band deformation potential, which is a result of our observed anisotropic strain induced by sodium intercalation. The applied uniaxial strain calculations based on density functional theory (DFT) agree strongly with the experimental ARPES data. These findings should assist in studying the physical relationship between doping and strain, as well as for large-scale two-dimensional straintronics. In summary, we have observed an increase in orbital valence band splitting, band gap shrinkage and anisotropic unit cell enlargement by evaporating sodium onto HfSe2 surfaces corresponding to 27% surface doping concentration (equivalent to 0.27 electrons donated per surface unit cell). Our experimental ARPES data are well-supported by computational DFT calculations of fully relaxed Na0.25HfSe2, where the calculations showed the HfSe2 layer anisotropically distorted with about 5% strain due to sodium intercalants. Overall, it can be concluded that the presence of effective armchair-tensile strain is induced by sodium intercalation. We have also demonstrated the possibility of orbital control at the valence band maximum with ’valley physics’. In future work, this could be achieved by applying opposite uniaxial strain by introduction of different cationic (Na, K) or anionic (Cl, Br) intercalants or ionic liquids. These observations support an overall understanding of doping/strain physics to facilitate exploration of novel phenomena among layered-TMDs. This could also be used as a direct technique for large-scale strain engineering in tuning optical and electronic properties as well as for straintronics such as nanoscale stress sensors and tuneable photonic
a. devices b. controls c. interactions d. concentration.
Q16.arXiv:1801.07486 [cond-mat.mtrl-sci]: Direct observation of strain-induced orbital valence band splitting in HfSe2 by sodium intercalation: T. Eknapakul, I. Fongkaew, S. Siriroj, W. Jindata, S. Chaiyachad, S.-K. Mo, S. Thakur, L. Petaccia, H. Takagi, S. Limpijumnong, W. Meevasana: (Submitted on 23 Jan 2018): ABSTRACT: By using angle-resolved photoemission spectroscopy (ARPES), the variation of the electronic structure of HfSe2 has been studied as a function of sodium intercalation. We observe how this drives a band splitting of the p-orbital valence bands and a simultaneous reduction of the indirect band gap by values of up to 400 and 280 meV respectively. Our calculations indicate that such behaviour is driven by the band deformation potential, which is a result of our observed anisotropic strain induced by sodium intercalation. The applied uniaxial strain calculations based on density functional theory (DFT) agree strongly with the experimental ARPES data. These findings should assist in studying the physical relationship between doping and strain, as well as for large-scale two-dimensional straintronics. In summary, we have observed an increase in orbital valence band splitting, band gap shrinkage and anisotropic unit cell enlargement by evaporating sodium onto HfSe2 surfaces corresponding to 27% surface doping concentration (equivalent to 0.27 electrons donated per surface unit cell). Our experimental ARPES data are well-supported by computational DFT calculations of fully relaxed Na0.25HfSe2, where the calculations showed the HfSe2 layer anisotropically distorted with about 5% strain due to sodium intercalants. Overall, it can be concluded that the presence of effective armchair-tensile strain is induced by sodium intercalation. We have also demonstrated the possibility of orbital control at the valence band maximum with ’valley physics’. In future work, this could be achieved by applying opposite uniaxial strain by introduction of different cationic (Na, K) or anionic (Cl, Br) intercalants or ionic liquids. These observations support an overall understanding of doping/strain physics to facilitate exploration of novel phenomena among layered-TMDs. This could also be used as a direct technique for large-scale strain engineering in tuning optical and electronic properties as well as for straintronics such as nanoscale stress sensors and tuneable photonic
a. strains b. straintronics c. valley Physics d. devices
Q17. arXiv:astro-ph/0702045: The Cosmic Ray Distribution in Sagittarius B: Roland M. Crocker et al., (Submitted on 1 Feb 2007 (v1), last revised 23 Mar 2007 (this version, v2)): ABSTRACT: The HESS instrument has observed a diffuse flux of ∼ TeV γ-rays from a large solid angle around the Galactic center (GC). This emission is correlated with the distribution of gas in the region suggesting that the γ-rays originate in collisions between cosmic ray hadrons (CRHs) and ambient matter. Of particular interest, HESS has detected γ-rays from the Sagittarius (Sgr) B Molecular Cloud Complex. Prompted by the suggestion of a hadronic origin for the gamma rays, we have examined archival 330 and 74 MHz Very Large Array radio data and 843 MHz Sydney University Molonglo Sky Survey data covering Sgr B, looking for synchrotron emission from secondary electrons and positrons (expected to be created in the same interactions that supply the observed gamma rays). Intriguingly, we have uncovered non-thermal emission, but at a level exceeding expectation. Adding to the overall picture, recent observations by the Atacama Pathfinder Experiment telescope show that the cosmic ray ionization rate is ten times greater in the Sgr B2 region of Sgr B than the local value. Lastly, Sgr B2 is also a very bright X-ray source. We examine scenarios for the spectra of CRHs and/or primary electrons that would reconcile all these different data. We determine that (i) a hard (∼ E−2.2), high-energy (& TeV) population CRHs is unavoidably required by the HESS γ-ray data and (ii) the remaining broad-band, non-thermal phenomenology is explained either by a rather steep (∼ E−2.9) spectrum of primary electrons or a (∼ E−2.7) population of CRHs. Perhaps unsurprisingly, no single, power-law population of either leptons or hadrons can explain the totality of broadband, non-thermal Sgr B phenomenology. CONCLUSIONS: A major result of this work is that we get far too little radio flux from secondary leptons (normalized to the HESS γ-ray data) to explain the VLA and SUMSS observations for reasonable magnetic field values and assuming a power-law (in momentum) behavior of the initiating CRH primaries. Furthermore – making the (perhaps naive) assumption that the CRHs be governed by a single power law in momentum from ultra-relativistic energies down to the sub-relativistic regime – the cosmic ray ionization rate ζCR implied by the CRH population inferred from the HESS γ-ray data is far too small to be reconciled with recent determinations of this quantity for Sgr B2. Conversely, a simple interpretation of the ionization rate in this cloud being maintined solely by the CRH distribution would then overproduce TeV photons via pp scattering events compared to what is measured by HESS (again, assuming a pure power law). Another major result is that it seems almost certain that one needs a hard, high-energy cosmic-ray hadron population to explain the HESS TeV+ γ-ray data: a particular model introduced by Yusef-Zadeh et al. (2006) that would seek to explain this emission by inverse Compton scattering by a population of primary cosmic ray electrons seems to break down when considered in detail. Certainly, as for the comsic ray hadron case, a single power-law distribution of primary electrons cannot account for all Sgr B phenomenology. We have investigated two scenarios that can be reconciled with all the data:
1. A scenario invoking two CRH power law populations (with a steep spectrum dominant at low energy). This scenario requires an ambient magnetic field in the Sgr B Complex in the range 2-4 mG that, while apparently not excluded by existing Zeeman splitting and polarimetry data, may be uncomfortably high. Future submillimetre polarimetry measurements may soon rule in or rule out the necessary field strength. Zeeman splitting measurements at mm wavelengths with the next generation of instruments such as the Atacama Large Millimeter Array (ALMA: Wootten (2006)) may also have sufficient sensitivity to detect these high field strengths, even in lower density regions.
2. Following a path blazed by Yusef-Zadeh et al. (2006), we have investigated the idea that primary electrons play a significant role and, in fact, explain the bulk of the non-thermal Sgr B phenomenology. Unfortunately we find that the particular instantiation of a leptonic model arrived at by Yusef-Zadeh et al. (2006) does not seem to be phenomenologically viable (requiring as it does too small a magnetic field to be reconcilable with the data) or self-consistent (in its treatment of spectral distortion due to ionization cooling at low energies). We have found, however, a leptonic scenario which does satisfactorily account for much of the phenomenology of Sgr B (viz., the CR ionization rate, the X-ray continuum emission, and the 330 and 843 MHz radio emission) but a hadronic component, contrary to the opinions of Yusef-Zadeh et al. (2006), is apparently necessary to explain the gamma-ray emission as mentioned
a. separately b. cursorily c. evidently d. above.
Q18. arXiv:1801.08396 [gr-qc]: Dark Matter: The Problem of Motion: Magd E. Kahil: (Submitted on 25 Jan 2018): ABSTRACT: Equations of non-geodesic and non-geodesic deviations for different particles are obtained, using a specific type of classes of the Bazanski Lagrangian. Such type of paths has been found to describe the problem of variable mass in the presence of Riemannian geometry. This may give rise to detect the effect of dark matter which reveals the mystery of motion of celestial objects that are not responding neither to Newtonian nor Einsteinian gravity. An important link between non-geodesic equations and the dipolar particle or fluids has been introduced to apply the concept of geometrization of physics. This concept has been already extended to represent the hydrodynamic equations in a geometric way. Such an approach, demands to seek for an appropriate theory of gravity able to describe different regions, eligible for detecting dark matter. Using different versions of bi-metric theory of gravity, to examine their associate non-geodesic paths. Due to implementing the geometrization concept, the stability problem of non-geodesic equations are essential to be studied for detecting the behaviour of those objects in the presence of dark matter. DETAILS: The quest of flat rotational curves for spiral galaxies cannot be explained neither classical nor general relativistic gravity, such a violation can be regarded to the existence of dark matter. In our Galaxy, several meticulous observations have confirmed that, the rotational velocities are ranging between 200 ∼ 300km/s, based on considering it as a function of the distance r from the SgrA*. Yet, such a tendency to express to include DM in the halo as dipolar particles is constraining this effect al galactic level, which is a violation to apparent observation that DM is also existed in the Universe as well as being felt to associated incidences of excess of γ-ray radiation as an indicator of self annihilation DM-particles in the AGNs, as well as nearby neutron stars, binary pulsars. This can be revealed by applying Blanchet’s approach of replacing the dipolar particles by dipolar fluids. In favor of this idea, the dipolar fluid may feel the interaction with dark energy and that itself quite reasonable due to the dominance of dark energy 74% while dark matter occupies 23% due to the well known observations, while baryonic matter is about 4%. Recently, due to ESA’s Planck mission DM has been found to be
a. 26% b. 48% c. 18% d.38%
Q19. arXiv:1801.08146 [astro-ph.HE]: From the earliest pulses to the latest flares in long GRBs: A. Pescalli, M. Ronchi, G. Ghirlanda, G. Ghisellini: (Submitted on 24 Jan 2018): ABSTRACT: The prompt emission of Gamma Ray Bursts extends from the early pulses observed in gamma-rays (>15 keV) to very late flares of X-ray photons (0.3-10keV). The duration of prompt gamma-ray pulses is rather constant while the width of X-ray flares correlates with their peak time suggesting a possible different origin. However, pulses and flares have similar spectral properties. Considering internal and external shock scenarios, we derive how the energy and duration of pulses scale with their time of occurrence and we compare with observations. The absence of an observed correlation between prompt emission pulse duration and its time of occurrence favours an "internal" origin and confirms the earlier results of Ramirez-Ruiz & Fenimore. We show that also the energetic and temporal properties of X-ray flares are consistent with being produced by internal shocks between slow fireballs with a small contrast between their bulk Lorentz factors. These results relax the requirement of a long lasting central engine to explain the latest X-ray flares. There can be two phases of accretion on to the black hole. The first is the accretion of the very dense material left over by the collapse of the core of the star. This dense material can sustain very large magnetic fields that can extract the spin energy of the black hole. The power so extracted is very large allowing the formation of shells of very large Γ–factors. If the accretion is modulated, or quasi–intermittent, then it is possible to form shells with very different energetics and bulk Lorentz factors. This phase is followed by the accretion of fall-back material, less dense. This corresponds to the extraction of less spin energy from the black hole, and presumably both the maximum and the average values of the bulk Lorentz factors are smaller, as well as the Γ–contrast between consecutive
a. factors b. fall back c. fields d. shells
Q20. arXiv:1801.08197 [astro-ph.GA]: ABSTRACT: Modelling CO, CO2 and H2O ice abundances in the envelopes of young stellar objects in the Magellanic Clouds: Tyler Pauly, R. T. Garrod: (Submitted on 24 Jan 2018): Massive young stellar objects in the Magellanic Clouds show infrared absorption features corresponding to significant abundances of CO, CO2 and H2O ice along the line of sight, with the relative abundances of these ices differing between the Magellanic Clouds and the Milky Way. CO ice is not detected towards sources in the Small Magellanic Cloud, and upper limits put its relative abundance well below sources in the Large Magellanic Cloud and the Milky Way. We use our gas-grain chemical code MAGICKAL, with multiple grain sizes and grain temperatures, and further expand it with a treatment for increased interstellar radiation field intensity to model the elevated dust temperatures observed in the MCs. We also adjust the elemental abundances used in the chemical models, guided by observations of HII regions in these metal-poor satellite galaxies. With a grid of models, we are able to reproduce the relative ice fractions observed in MC massive young stellar objects (MYSOs), indicating that metal depletion and elevated grain temperature are important drivers of the MYSO envelope ice composition. Magellanic Cloud elemental abundances have a sub-galactic C/O ratio, increasing H2O ice abundances relative to the other ices; elevated grain temperatures favor CO2 production over H2O and CO. The observed shortfall in CO in the Small Magellanic Cloud can be explained by a combination of reduced carbon abundance and increased grain temperatures. The models indicate that a large variation in radiation field strength is required to match the range of observed LMC abundances. CH3OH abundance is found to be enhanced in low-metallicity models, providing seed material for complex organic molecule formation in the Magellanic Clouds. The Magellanic Clouds, local dwarf satellites of the Milky Way, provide an astronomical laboratory to study the processof star formationin a metal-poorenvironment. Comparison studies between sites of star formation in the Magellanic Clouds and the Milky Way can illuminate the metallicity dependence of local physical processes via observational tracers such as molecular emission and absorption features. We leave some issues to be addressed in future work. Thermal processing of the ice is important for matching observed ice abundances, and it is not included in these models. We find significant growth in the [dust+mantle] radius, which affects both the dust temperature and surface chemistry; however, we assume a Qabs of carbonaceous dust for temperature calculations, though the Qabs of ice will differ. We also use a grain size distribution found for silicate grains; this could be resolved by using values for silicate or carbonaceous grains throughout, or by attempting to model both populations. Future models could investigate the dependence on cosmic ray ionization rate, a parameter with large variation across the
a. DMC b. LMC c. BMC d. AMC.
a. step b. role c. rule. d. manifestation.
Q14. arXiv:1801.08057 [quant-ph]: Energy-temperature uncertainty relation in quantum thermodynamics: Harry J. D. Miller, Janet Anders: (Submitted on 24 Jan 2018): Much like Heisenberg's uncertainty principle in quantum mechanics, there exists the thermodynamic uncertainty relation in classical statistical mechanics that limits simultaneous estimations of energy and temperature for a system in equilibrium. However, for nanoscale systems deviations from standard thermodynamics arise due to non-negligible interactions with the environment. Here we include interactions and, using quantum estimation theory, derive a generalised thermodynamic uncertainty relation valid for classical and quantum systems at all coupling strengths. We show that the non-commutativity between the system's state and its effective energy operator gives rise to additional quantum fluctuations that increase the uncertainty in temperature and modify the heat capacity. Surprisingly, these quantum fluctuations are described by the average Wigner-Yanase-Dyson skew information, a quantity intimately connected to measures of coherence. For temperature estimation we demonstrate that the optimal signal-to-noise ratio is constrained not only by the heat capacity, but an additional dissipative term arising from the non-negligible interactions. Practically this will inform the design of optimal nanoscale thermometers. On the fundamental side the results shed light on the interplay between classical and non-classical fluctuations in quantum thermodynamics. Details: Bohr suggested that there should exist a form of complementarity between temperature and energy in thermodynamics similar to that of position and momentum in quantum theory. His reasoning was that in order to assign a definite temperature T to a system it must be brought in contact with a thermal reservoir, in which case the energy U of the system fluctuates due to exchanges with the reservoir. On the other hand, to assign a sharp energy to the system it must be isolated from the reservoir, rendering the system’s temperature T uncertain. Based on this heuristic argument Bohr conjectured the thermodynamic uncertainty relation: ∆U ∆β ≥ 1, (1) with β = (kBT)−1 the inverse temperature. The presented approach opens up opportunities for exploring the intermediate regime between the limiting cases of standard thermodynamics with negligible interactions and those where correlations play a prominent role. The results establish a new connection between abstract measures of quantum information theory, such as the quantum Fisher information and skew information, and a material’s effective thermodynamic properties. This provides a starting point for future investigations into nanoscale thermodynamics, extending into the regime where the weak coupling assumption is not
a. correct b. genuine c. exemplary d. justified.
Q15. arXiv:1801.07486 [cond-mat.mtrl-sci]: Direct observation of strain-induced orbital valence band splitting in HfSe2 by sodium intercalation: T. Eknapakul, I. Fongkaew, S. Siriroj, W. Jindata, S. Chaiyachad, S.-K. Mo, S. Thakur, L. Petaccia, H. Takagi, S. Limpijumnong, W. Meevasana: (Submitted on 23 Jan 2018): ABSTRACT: By using angle-resolved photoemission spectroscopy (ARPES), the variation of the electronic structure of HfSe2 has been studied as a function of sodium intercalation. We observe how this drives a band splitting of the p-orbital valence bands and a simultaneous reduction of the indirect band gap by values of up to 400 and 280 meV respectively. Our calculations indicate that such behaviour is driven by the band deformation potential, which is a result of our observed anisotropic strain induced by sodium intercalation. The applied uniaxial strain calculations based on density functional theory (DFT) agree strongly with the experimental ARPES data. These findings should assist in studying the physical relationship between doping and strain, as well as for large-scale two-dimensional straintronics. In summary, we have observed an increase in orbital valence band splitting, band gap shrinkage and anisotropic unit cell enlargement by evaporating sodium onto HfSe2 surfaces corresponding to 27% surface doping concentration (equivalent to 0.27 electrons donated per surface unit cell). Our experimental ARPES data are well-supported by computational DFT calculations of fully relaxed Na0.25HfSe2, where the calculations showed the HfSe2 layer anisotropically distorted with about 5% strain due to sodium intercalants. Overall, it can be concluded that the presence of effective armchair-tensile strain is induced by sodium intercalation. We have also demonstrated the possibility of orbital control at the valence band maximum with ’valley physics’. In future work, this could be achieved by applying opposite uniaxial strain by introduction of different cationic (Na, K) or anionic (Cl, Br) intercalants or ionic liquids. These observations support an overall understanding of doping/strain physics to facilitate exploration of novel phenomena among layered-TMDs. This could also be used as a direct technique for large-scale strain engineering in tuning optical and electronic properties as well as for straintronics such as nanoscale stress sensors and tuneable photonic
a. devices b. controls c. interactions d. concentration.
Q16.arXiv:1801.07486 [cond-mat.mtrl-sci]: Direct observation of strain-induced orbital valence band splitting in HfSe2 by sodium intercalation: T. Eknapakul, I. Fongkaew, S. Siriroj, W. Jindata, S. Chaiyachad, S.-K. Mo, S. Thakur, L. Petaccia, H. Takagi, S. Limpijumnong, W. Meevasana: (Submitted on 23 Jan 2018): ABSTRACT: By using angle-resolved photoemission spectroscopy (ARPES), the variation of the electronic structure of HfSe2 has been studied as a function of sodium intercalation. We observe how this drives a band splitting of the p-orbital valence bands and a simultaneous reduction of the indirect band gap by values of up to 400 and 280 meV respectively. Our calculations indicate that such behaviour is driven by the band deformation potential, which is a result of our observed anisotropic strain induced by sodium intercalation. The applied uniaxial strain calculations based on density functional theory (DFT) agree strongly with the experimental ARPES data. These findings should assist in studying the physical relationship between doping and strain, as well as for large-scale two-dimensional straintronics. In summary, we have observed an increase in orbital valence band splitting, band gap shrinkage and anisotropic unit cell enlargement by evaporating sodium onto HfSe2 surfaces corresponding to 27% surface doping concentration (equivalent to 0.27 electrons donated per surface unit cell). Our experimental ARPES data are well-supported by computational DFT calculations of fully relaxed Na0.25HfSe2, where the calculations showed the HfSe2 layer anisotropically distorted with about 5% strain due to sodium intercalants. Overall, it can be concluded that the presence of effective armchair-tensile strain is induced by sodium intercalation. We have also demonstrated the possibility of orbital control at the valence band maximum with ’valley physics’. In future work, this could be achieved by applying opposite uniaxial strain by introduction of different cationic (Na, K) or anionic (Cl, Br) intercalants or ionic liquids. These observations support an overall understanding of doping/strain physics to facilitate exploration of novel phenomena among layered-TMDs. This could also be used as a direct technique for large-scale strain engineering in tuning optical and electronic properties as well as for straintronics such as nanoscale stress sensors and tuneable photonic
a. strains b. straintronics c. valley Physics d. devices
Q17. arXiv:astro-ph/0702045: The Cosmic Ray Distribution in Sagittarius B: Roland M. Crocker et al., (Submitted on 1 Feb 2007 (v1), last revised 23 Mar 2007 (this version, v2)): ABSTRACT: The HESS instrument has observed a diffuse flux of ∼ TeV γ-rays from a large solid angle around the Galactic center (GC). This emission is correlated with the distribution of gas in the region suggesting that the γ-rays originate in collisions between cosmic ray hadrons (CRHs) and ambient matter. Of particular interest, HESS has detected γ-rays from the Sagittarius (Sgr) B Molecular Cloud Complex. Prompted by the suggestion of a hadronic origin for the gamma rays, we have examined archival 330 and 74 MHz Very Large Array radio data and 843 MHz Sydney University Molonglo Sky Survey data covering Sgr B, looking for synchrotron emission from secondary electrons and positrons (expected to be created in the same interactions that supply the observed gamma rays). Intriguingly, we have uncovered non-thermal emission, but at a level exceeding expectation. Adding to the overall picture, recent observations by the Atacama Pathfinder Experiment telescope show that the cosmic ray ionization rate is ten times greater in the Sgr B2 region of Sgr B than the local value. Lastly, Sgr B2 is also a very bright X-ray source. We examine scenarios for the spectra of CRHs and/or primary electrons that would reconcile all these different data. We determine that (i) a hard (∼ E−2.2), high-energy (& TeV) population CRHs is unavoidably required by the HESS γ-ray data and (ii) the remaining broad-band, non-thermal phenomenology is explained either by a rather steep (∼ E−2.9) spectrum of primary electrons or a (∼ E−2.7) population of CRHs. Perhaps unsurprisingly, no single, power-law population of either leptons or hadrons can explain the totality of broadband, non-thermal Sgr B phenomenology. CONCLUSIONS: A major result of this work is that we get far too little radio flux from secondary leptons (normalized to the HESS γ-ray data) to explain the VLA and SUMSS observations for reasonable magnetic field values and assuming a power-law (in momentum) behavior of the initiating CRH primaries. Furthermore – making the (perhaps naive) assumption that the CRHs be governed by a single power law in momentum from ultra-relativistic energies down to the sub-relativistic regime – the cosmic ray ionization rate ζCR implied by the CRH population inferred from the HESS γ-ray data is far too small to be reconciled with recent determinations of this quantity for Sgr B2. Conversely, a simple interpretation of the ionization rate in this cloud being maintined solely by the CRH distribution would then overproduce TeV photons via pp scattering events compared to what is measured by HESS (again, assuming a pure power law). Another major result is that it seems almost certain that one needs a hard, high-energy cosmic-ray hadron population to explain the HESS TeV+ γ-ray data: a particular model introduced by Yusef-Zadeh et al. (2006) that would seek to explain this emission by inverse Compton scattering by a population of primary cosmic ray electrons seems to break down when considered in detail. Certainly, as for the comsic ray hadron case, a single power-law distribution of primary electrons cannot account for all Sgr B phenomenology. We have investigated two scenarios that can be reconciled with all the data:
1. A scenario invoking two CRH power law populations (with a steep spectrum dominant at low energy). This scenario requires an ambient magnetic field in the Sgr B Complex in the range 2-4 mG that, while apparently not excluded by existing Zeeman splitting and polarimetry data, may be uncomfortably high. Future submillimetre polarimetry measurements may soon rule in or rule out the necessary field strength. Zeeman splitting measurements at mm wavelengths with the next generation of instruments such as the Atacama Large Millimeter Array (ALMA: Wootten (2006)) may also have sufficient sensitivity to detect these high field strengths, even in lower density regions.
2. Following a path blazed by Yusef-Zadeh et al. (2006), we have investigated the idea that primary electrons play a significant role and, in fact, explain the bulk of the non-thermal Sgr B phenomenology. Unfortunately we find that the particular instantiation of a leptonic model arrived at by Yusef-Zadeh et al. (2006) does not seem to be phenomenologically viable (requiring as it does too small a magnetic field to be reconcilable with the data) or self-consistent (in its treatment of spectral distortion due to ionization cooling at low energies). We have found, however, a leptonic scenario which does satisfactorily account for much of the phenomenology of Sgr B (viz., the CR ionization rate, the X-ray continuum emission, and the 330 and 843 MHz radio emission) but a hadronic component, contrary to the opinions of Yusef-Zadeh et al. (2006), is apparently necessary to explain the gamma-ray emission as mentioned
a. separately b. cursorily c. evidently d. above.
Q18. arXiv:1801.08396 [gr-qc]: Dark Matter: The Problem of Motion: Magd E. Kahil: (Submitted on 25 Jan 2018): ABSTRACT: Equations of non-geodesic and non-geodesic deviations for different particles are obtained, using a specific type of classes of the Bazanski Lagrangian. Such type of paths has been found to describe the problem of variable mass in the presence of Riemannian geometry. This may give rise to detect the effect of dark matter which reveals the mystery of motion of celestial objects that are not responding neither to Newtonian nor Einsteinian gravity. An important link between non-geodesic equations and the dipolar particle or fluids has been introduced to apply the concept of geometrization of physics. This concept has been already extended to represent the hydrodynamic equations in a geometric way. Such an approach, demands to seek for an appropriate theory of gravity able to describe different regions, eligible for detecting dark matter. Using different versions of bi-metric theory of gravity, to examine their associate non-geodesic paths. Due to implementing the geometrization concept, the stability problem of non-geodesic equations are essential to be studied for detecting the behaviour of those objects in the presence of dark matter. DETAILS: The quest of flat rotational curves for spiral galaxies cannot be explained neither classical nor general relativistic gravity, such a violation can be regarded to the existence of dark matter. In our Galaxy, several meticulous observations have confirmed that, the rotational velocities are ranging between 200 ∼ 300km/s, based on considering it as a function of the distance r from the SgrA*. Yet, such a tendency to express to include DM in the halo as dipolar particles is constraining this effect al galactic level, which is a violation to apparent observation that DM is also existed in the Universe as well as being felt to associated incidences of excess of γ-ray radiation as an indicator of self annihilation DM-particles in the AGNs, as well as nearby neutron stars, binary pulsars. This can be revealed by applying Blanchet’s approach of replacing the dipolar particles by dipolar fluids. In favor of this idea, the dipolar fluid may feel the interaction with dark energy and that itself quite reasonable due to the dominance of dark energy 74% while dark matter occupies 23% due to the well known observations, while baryonic matter is about 4%. Recently, due to ESA’s Planck mission DM has been found to be
a. 26% b. 48% c. 18% d.38%
Q19. arXiv:1801.08146 [astro-ph.HE]: From the earliest pulses to the latest flares in long GRBs: A. Pescalli, M. Ronchi, G. Ghirlanda, G. Ghisellini: (Submitted on 24 Jan 2018): ABSTRACT: The prompt emission of Gamma Ray Bursts extends from the early pulses observed in gamma-rays (>15 keV) to very late flares of X-ray photons (0.3-10keV). The duration of prompt gamma-ray pulses is rather constant while the width of X-ray flares correlates with their peak time suggesting a possible different origin. However, pulses and flares have similar spectral properties. Considering internal and external shock scenarios, we derive how the energy and duration of pulses scale with their time of occurrence and we compare with observations. The absence of an observed correlation between prompt emission pulse duration and its time of occurrence favours an "internal" origin and confirms the earlier results of Ramirez-Ruiz & Fenimore. We show that also the energetic and temporal properties of X-ray flares are consistent with being produced by internal shocks between slow fireballs with a small contrast between their bulk Lorentz factors. These results relax the requirement of a long lasting central engine to explain the latest X-ray flares. There can be two phases of accretion on to the black hole. The first is the accretion of the very dense material left over by the collapse of the core of the star. This dense material can sustain very large magnetic fields that can extract the spin energy of the black hole. The power so extracted is very large allowing the formation of shells of very large Γ–factors. If the accretion is modulated, or quasi–intermittent, then it is possible to form shells with very different energetics and bulk Lorentz factors. This phase is followed by the accretion of fall-back material, less dense. This corresponds to the extraction of less spin energy from the black hole, and presumably both the maximum and the average values of the bulk Lorentz factors are smaller, as well as the Γ–contrast between consecutive
a. factors b. fall back c. fields d. shells
Q20. arXiv:1801.08197 [astro-ph.GA]: ABSTRACT: Modelling CO, CO2 and H2O ice abundances in the envelopes of young stellar objects in the Magellanic Clouds: Tyler Pauly, R. T. Garrod: (Submitted on 24 Jan 2018): Massive young stellar objects in the Magellanic Clouds show infrared absorption features corresponding to significant abundances of CO, CO2 and H2O ice along the line of sight, with the relative abundances of these ices differing between the Magellanic Clouds and the Milky Way. CO ice is not detected towards sources in the Small Magellanic Cloud, and upper limits put its relative abundance well below sources in the Large Magellanic Cloud and the Milky Way. We use our gas-grain chemical code MAGICKAL, with multiple grain sizes and grain temperatures, and further expand it with a treatment for increased interstellar radiation field intensity to model the elevated dust temperatures observed in the MCs. We also adjust the elemental abundances used in the chemical models, guided by observations of HII regions in these metal-poor satellite galaxies. With a grid of models, we are able to reproduce the relative ice fractions observed in MC massive young stellar objects (MYSOs), indicating that metal depletion and elevated grain temperature are important drivers of the MYSO envelope ice composition. Magellanic Cloud elemental abundances have a sub-galactic C/O ratio, increasing H2O ice abundances relative to the other ices; elevated grain temperatures favor CO2 production over H2O and CO. The observed shortfall in CO in the Small Magellanic Cloud can be explained by a combination of reduced carbon abundance and increased grain temperatures. The models indicate that a large variation in radiation field strength is required to match the range of observed LMC abundances. CH3OH abundance is found to be enhanced in low-metallicity models, providing seed material for complex organic molecule formation in the Magellanic Clouds. The Magellanic Clouds, local dwarf satellites of the Milky Way, provide an astronomical laboratory to study the processof star formationin a metal-poorenvironment. Comparison studies between sites of star formation in the Magellanic Clouds and the Milky Way can illuminate the metallicity dependence of local physical processes via observational tracers such as molecular emission and absorption features. We leave some issues to be addressed in future work. Thermal processing of the ice is important for matching observed ice abundances, and it is not included in these models. We find significant growth in the [dust+mantle] radius, which affects both the dust temperature and surface chemistry; however, we assume a Qabs of carbonaceous dust for temperature calculations, though the Qabs of ice will differ. We also use a grain size distribution found for silicate grains; this could be resolved by using values for silicate or carbonaceous grains throughout, or by attempting to model both populations. Future models could investigate the dependence on cosmic ray ionization rate, a parameter with large variation across the
a. DMC b. LMC c. BMC d. AMC.
Q21.arXiv:1801.08538 [physics.ins-det]: A Radiation Tolerant Light Pulser for Particle Physics Applications: A. Grummer, M. R. Hoeferkamp, S. Seidel:(Submitted on 25 Jan 2018):A light emitting diode (LED) pulser has been developed that can be used for tests or calibration of timing and amplitude sensitivity of particle physics detectors. A comparative study is performed on the components and pulser output characteristics before and after application of 800 MeV protons and cobalt-60 gammas. The gamma and proton irradiated components were removed from the pulser boards after irradiation. The pulse width of the pulser before and after gamma irradiation to doses of 0.1, 0.5, 1.0, 3.0, and 5.0 Mrad. Data shown are the averaged values of two devices at each dose. Measured forward current and applied forward voltage of irradiated versus non-irradiated LED 465E components. LEDs’ current versus voltage (IV) characteristics were measured. The IV curves of the gamma irradiated LEDs overlap the IV curves of the nonirradiated ones. In the proton irradiated devices the forward threshold voltage is increased and for any given forward voltage the output current (and thus the output light) is diminished in proportion to the applied proton fluence. Fig. 9 examines the effect of the radiation on the transistors’ gain; we show here an example of the IC vs VBE of the BFR93A NPN transistor. Data from the gamma-irradiated devices again overlap the data from the non-irradiated transistors. The proton irradiated transistors exhibit a higher shift in VBE threshold voltage and a decrease in transistor gain. Similar results are measured on the BFT92 PNP transistor. All other components (thick film resistors, ceramic capacitors, and a wire-wound ferrite core inductor) were found to have been unaffected by both the gamma and the proton exposures. Visual inspection shows the LED to be discolored by both gamma and proton exposure. We conclude that the reduction of the PMT output amplitude of the gamma irradiated devices is due to discoloration of the clear LED casing. The reduction of the PMT output amplitude seen in the proton irradiated devices is due to the effects on the semiconductor material in the LEDs and transistors as well as the LED casing discoloration. This device is demonstrated to be tolerant to fluences up to 6.7 x10^13 800-MeV-p/cm^2 and gamma doses up to 5 Mrad. A pulser circuit suitable for operation in radiation fields up to at least 6.7 x 10^13 800-MeV-protons/cm^2 and 5 Mrad gammas has been developed. Pulse widths are largely unchanged due to the irradiations and remain in the 4-12 ns range depending upon input voltage. Output amplitude and thus the light output decreases proportionally to the proton and gamma exposure but preserves 80% (in the case of gammas) and 50% (in the case of hadrons) at the highest exposure. The affected components of the pulser board are the RF transistors and the LEDs. The LED cases are sensitive to both species, while the semiconductors are changed by the hadrons only. The device is compact, economical, and applicable to a variety of particle physics experimental
a. environments b. conditions c. boosts d. pulses.
a. environments b. conditions c. boosts d. pulses.
Q22. arXiv:1801.08645 [physics.app-ph]: Hybrid photo-electrochemical and photo-voltaic cells (HPEV cells): Gideon Segev, Jeffery Beeman, Ian D. Sharp: (Submitted on 26 Jan 2018): ABSTRACT: The majority of photoelectrochemical (PEC) water splitting cells cannot drive the overall water splitting reactions without the assistance of an external power source. To provide added power, the cells are usually connected to photovoltaic (PV) devices in a tandem arrangement. This approach suffers from severe disadvantages since the PEC cell is connected in series to the PV cell and the overall current is typically limited by the saturation current of the PEC component. Thus, the operating point of the PV cell is often far from optimal and the overall system efficiency tends to be low. We propose a multi-terminal hybrid PV and PEC system (HPEV). As in tandem arrangements, the PEC cell is optically connected in series with the PV cell. However, a second back contact is used to extract the PV cell surplus current and allow parallel production of both electrical power and chemical fuel. Devices consisting of three-terminal silicon photovoltaic cells coupled to titanium dioxide water splitting layers are simulated and fabricated. The cells are shown to produce electricity with little reduction in the water splitting current, surpass the current mismatch limits, and increase the overall system efficiency. A new class of devices, the hybrid photoelectrochemical and photovoltaic cells, were proposed. These devices are dual junction photoelectrochemical cells in which a second back contact is added to extract charge carriers that cannot be injected into the top junction due to current mismatches. The functional performance of the cells was studied with finite elements modelling and verified in prototypes fabricated from a silicon bottom junction and a TiO2 top junction. It is shown that charge carriers that do not contribute to the chemical reaction can be harvested as electrical power at the maximum power point with a negligible effect on the chemical output. Equivalent circuit based modelling shows that HPEV cells made from off the shelf back contact solar cell can at least double the overall output of system for top junctions with band gaps above
a. 2.1eV b. 1.8eV c. 2.3eV d. 1.5eV
Q23. arXiv:1802.00005 [astro-ph.GA]: Magnetic fields at the onset of high-mass star formation: H. Beuther, et al., (Submitted on 31 Jan 2018). Context: The importance of magnetic fields at the onset of star formation related to the early fragmentation and collapse processes is largely unexplored today. Aims: We want to understand the magnetic field properties at the earliest evolutionary stages of high-mass star formation. Methods: The Atacama Large Millimeter Array is used at 1.3mm wavelength in full polarization mode to study the polarized emission and by that the magnetic field morphologies and strengths of the high-mass starless region IRDC183 10^-4. Results: The polarized emission is clearly detected in four sub-cores of the region. In general it shows a smooth distribution, also along elongated cores. Estimating the magnetic field strength via the Davis-Chandrasekhar-Fermi method and following a structure function analysis, we find comparably large magnetic field strengths between ~0.6 and 3.7mG. Comparing the data to spectral line observations, the turbulent-to-magnetic energy ratio is low, indicating that turbulence does not significantly contribute to the stability of the gas clump. A mass-to-flux ratio around the critical value 1.0 - depending on column density - indicates that the region starts to collapse which is consistent with the previous spectral line analysis of the region. Conclusions: While this high-mass region is collapsing and thus at the verge of star formation, the high magnetic field values and the smooth spatial structure indicate that the magnetic field is important for the fragmentation and collapse process. This single case study can only be the starting point for larger sample studies of magnetic fields at the onset of star formation. The importance of magnetic fields during the formation of stars has been topic of great controversy over the last decades. While some groupsstress that magneticfields have to be important during cloud formation and core collapse processes. Others consider that the effects of turbulence and gravity are far more important for governing star formation. Even the interpretation of a single dataset can be extremely controversial regarding the importance of magnetic fields. Although the sensitivity of these da ta is not sufficient to detect cores below 1M⊙, the fact that massive non-fragmenting cores at the given spatial resolution are identified, is indicative of large magnetic fields that we observe now with the new ALMA data. The overall smooth spatial structure of the polarization angles is additional evidence for the dynamic importance of the magnetic field. In summary, while the maternal gas clump is collapsing at large, the polarization data reveal that the magnetic field is important for the fragmentation and star formation process in this
a. space b. field c. area d. region.
Q24. arXiv:1802.00191 [astro-ph.SR]: Powerful Solar Flares of September 2017: Correspondence Between Parameters of Microwave Bursts and Proton Fluxes near Earth I. M. Chertok, (Submitted on 1 Feb 2018): ABSTRACT: In this note, we consider radio characteristics of three proton flares that caused discrete enhancements of solar energetic particles (SEPs) near Earth. The analysis confirmed that the flux density and frequency spectrum of microwave bursts, although the latter are generated by electrons propagating to the photosphere, reflect the number and energy spectrum of accelerated particles, including the 10-100 MeV protons coming to Earth. A strong outburst of solar activity occurred on 2017 September 4–10, when approaching a minimum of Cycle 24. It was due to the sharp development and evolution of the active region 12673 during its passage across the western half of the visible disk. Numerous strong flares occurred at this time, including 27 M-class and 4 X-class flares. Among the latter, the X9.3 flare on September 6 was the most powerful in the last 10 years. It is not surprising that this activity and associated space weather disturbances arouse great interest, and many publications have already been devoted to their study. In this note, we consider radio characteristics of three proton flares that caused discrete enhancements of solar energetic particles (SEPs) near Earth.The September 10 event has quite different characteristics. Its radio spectrum shows a sharp increase from 3 to 15 GHz and should be considered as hard. The maximum radio flux at 15 GHz is very large S15 ≈ 21,000 sfu (1 sfu = 10−22 W m^−2 Hz^−1). In accordance with these radio parameters, the observed SEP, as a typical western event, was very intense (J10 ≈ 1000 pfu) and had a rather hard proton energy spectrum with γ ≈ 1.4. The September 6 event has intermediate features both on the radio spectrum and on the proton flux parameters. Its radio spectrum indicates a decimetre portion and an increasing microwave component with the peak flux at 15 GHz S15 ≈ 8100 sfu. This corresponds to the observed SEP of a rather hard energy spectrum with the index γ ≈ 1.5 estimated by the flux in the >50 and 100 MeV channels. Before and after this SEP, the >10 Mev proton flux was disturbed by CME from the September 4 flare and the subsequent geomagnetic
a. flare b. storm c. disturbance d. spectrum.
Q25.arXiv:1802.00204 [astro-ph.HE]:High-energy Emission Properties of Pulsars: Christo Venter, Alice K. Harding, Isabelle Grenier ABSTRACT: (Submitted on 1 Feb 2018):The sheer number of new gamma-ray pulsar discoveries by the Fermi Large Area Telescope (LAT) since 2008, combined with the quality of new multi-frequency data, has caused a revolution in the field of high-energy (HE) rotation-powered pulsars. These rapidly rotating neutron stars exhibit rich spectral and temporal phenomenology, indicating that there are still many unsolved mysteries regarding the magnetospheric conditions in these stars - even after 50 years of research! Indeed, 2017 marks the golden anniversary of the discovery of the first radio pulsar, and theorists and observers alike are looking forward to another half-century of discovery, with many new experiments coming online in the next decades. In this review paper, we will briefly summarise recent HE pulsar observations, mention some theoretical models that provide a basic framework within which to make sense of the varied measurements, and finally review some of the latest theoretical developments in pulsar emission modelling. DETAILS: Pulsars are seen across the electromagnetic spectrum. Their light curves vary with energy and time, but radio light curves1 averaged over pulsation period are usually quite stable. Their spectra span a very wide range in energy, making these rotating neutron stars true multi-frequency objects. Fundamental electrodynamical questions emerged: How and where is the current closed so that the outflow of particles is sustainable (i.e., what is the global current flow pattern)? What is the role of pair formation? What is the injection rate of plasma from the stellar surface? Where do acceleration gaps develop (where E|| is not fully screened) and how are they sustained? Where does acceleration of particles to relativistic energies take place? What is the emission mechanism for each of the multi-frequency components we observe? The conductivity in the macroscopic dissipative models is supplied by the electron-positron pair plasma at a microscopic level. Where and how this pair plasma originates is currently not completely understood. Important constraints on the location of pair plasma production in the pulsar magnetosphere as well as its spectrum will come from observations in the 100 keV to 10 MeV band. They assumed that optical to hard X-ray emission is produced by SR from electron-positron pairs and γ -ray emission is due to either CR or SR from primary
a. electrons b. protons c. pairs d. emissions
Q26. arXiv:1802.00224 [astro-ph.SR]: Polarimetry and Spectroscopy of the `Oxygen Flaring' DQ Herculis-like nova: V5668 Sagittarii (2015): E. J. Harveyet al., (Submitted on 1 Feb 2018): ABSTRACT: Classical novae are eruptions on the surface of a white dwarf in a binary system. The material ejected from the white dwarf surface generally forms an axisymmetric shell of gas and dust around the system. The three-dimensional structure of these shells is difficult to untangle when viewed on the plane of the sky. In this work a geometrical model is developed to explain new observations of the 2015 nova V5668 Sagittarii. To understand the ionisation structure in terms of the nova shell morphology and estimate the emission distribution directly following the light-curve's dust-dip. High-cadence optical polarimetry and spectroscopy observations of a nova are presented. The ejecta is modelled in terms of morpho-kinematics and photoionisation structure. Initially observational results are presented, including broadband polarimetry and spectroscopy of V5668 Sgr nova during eruption. Variability over these observations provides clues towards the evolving structure of the nova shell. The position angle of the shell is derived from polarimetry, which is attributed to scattering from small dust grains. Shocks in the nova outflow are suggested in the photometry and the effect of these on the nova shell are illustrated with various physical diagnostics. Changes in density and temperature as the super soft source phase of the nova began are discussed. Gas densities are found to be of the order of 10^9 cm ^−3 for the nova in its auroral phase. The blackbody temperature of the central stellar system is estimated to be around 2.2x10^5K at times coincident with the super soft source turn-on. It was found that the blend around 4640 $\rm{\AA}$ commonly called `nitrogen flaring' is more naturally explained as flaring of the O~{\sc ii} multiplet (V1) from 4638 - 4696 $\rm{\AA}$, i.e. `oxygen flaring'. Novae are known to be a distinct stellar event and in their simplest terms are considered as either fast (t3 < 20 days) or slow (t3 > 20 days, where t3 is the time taken for a nova’s magnitude to decrease by 3). Fast novae occur on more massive white dwarfs than slow novae and require less accreted matter in order to ignite the thermonuclear runaway and experience higher ejection velocities, e.g. Yaron et al. (2005). Slower novae counterparts typically occur on lower mass white dwarfs, eject more previously-accreted-material during eruption and the outflow has lower ejection velocities which creates rich dust formation factories. These objects are well observed during eruption where optical photometry and spectroscopy are the most thoroughly practiced approaches. Conclusions: The observations reveal variability of the absolute polarisation before and after nights that hint towards internal shocks in the nova outflow. Along with the available high-quality gamma, Xray, UV and IR observations on this nova, the polarimetry allowed for the estimation of the nova shell position angle and provided information on the dust grains causing the scattering. The spectroscopy then allowed for derivation of the physical conditions on separate nights, including outflow velocity and structure, nebular density, temperature and ionisation conditions. Following on from this extensive analysis, morpho-kinematic and photo-ionisation models were formulated and combined to give a deeper insight into the nova system as a whole. Finally we note that, for slow novae in particular, the regularly referred to ‘nitrogen flaring’ is in fact more likely to be ‘oxygen flaring’. Scattering due to
a. nitrogen flaring b. novae c. dust grains d. oxygen flaring.
Q27. arXiv:1801.03157 [gr-qc]: The massive Dirac equation in the curved spacetime of the Kerr-Newman (anti) de Sitter black hole: G. V. Kraniotis: (Submitted on 9 Jan 2018 (v1), last revised 30 Jan 2018 (this version, v2)): ABSTRACT: Exact solutions of the Dirac general relativistic equation that describe the dynamics of a massive, electrically charged with half integer spin particle in the curved spacetime geometry of an electrically charged, rotating Kerr-Newman-(anti) de Sitter black hole are investigated. We first, derive the Dirac equation in the Kerr-Newman-de Sitter (KNdS) black hole background using a generalised Kinnersley null tetrad in the Newman-Penrose formalism. Subsequently in this frame and in the KNdS black hole space-time, we prove the separation of the Dirac equation into ordinary differential equations for the radial and angular parts. For the case of a massive fermion in the background of a Kerr-Newman (KN) black hole we first prove that the radial and angular equations that result from the separation of Dirac's equation reduce to the generalised Heun differential equation (GHE). The local solutions of such GHE are derived and can be described by holomorphic functions whose power series coefficients are determined by a four-term recurrence relation. In addition using asymptotic analysis we derive the solutions for the massive fermion far away from the KN black hole and the solutions near the event horizon. details: The problem of massive perturbations in the strong gravity background of a black hole is a fascinating and of fundamental significance problem, as has been demonstrated recently for the case of scalar perturbations. Massive Fermion in
a. KN black hole b. KNdS black hole c. GHE d. event horizon.
Q28. arXiv:1801.08084 [gr-qc]: Regularity of high energy photon events from gamma ray bursts: Haowei Xu, Bo-Qiang Ma: (Submitted on 24 Jan 2018): The effect of Quantum Gravity (QG) may bring a tiny light speed variation as v(E)=c(1−E/ELV), where E is the photon energy and ELV is a Lorentz violation scale. A remarkable regularity was suggested in previous studies to look for the light speed variation from high energy photon events of Gamma Ray Bursts (GRBs). We provide a general analysis on the data of 25 bright GRBs observed by the Fermi Gamma-ray Space Telescope (FGST). Such method allows a completed scan over all possibilities in a more clean and impartial way without any bias compared to previous intuitive analysis. The results show that with the increase in the intrinsic energies of photons, such regularity truly emerges and gradually becomes significant. The speed of light is assumed to be a constant c in Einstein’s relativity. However, it is speculated from quantum gravity theories that Lorentz invariance is violated at the Planck scale (E ∼ EPl =sqrt(hcross*c5/G) ≈ 1.22×10^19 GeV. A possible consequence is that the speed of light is no longer a constant c but energy dependent. In conclusion, we use a general method to analyze the data of 25 bright GRBs detected by FGST. The results suggest that for photons with energy higher than 40 GeV, the regularity of high energy photon events from different GRB s exists at a significance of 3-5σ with ELV = 3.6×10^17 GeV determined by the GRB data. Tiny speed variation due to
a. ELV b. QG c. GRB d. FGST
Q29. arXiv:1802.00236 [physics.app-ph]: Laser induced breakdown spectroscopy for multielement analysis of powder materials utilized in additive technologies: V.N. Lednev et al.,, (Submitted on 1 Feb 2018): ABSTRACT: Powder materials utilized in additive technologies were quantitatively analyzed by laser induced breakdown spectroscopy for the first time. Laser induced breakdown spectroscopy mapping of loose metal powder attached to the double-sided adhesive tape provided high reproducibility of measurements even for powder mixtures with large difference of particles densities (tungsten carbide particles in nickel alloy powder). Laser induced breakdown spectroscopy analytical capabilities for tungsten and carbon analysis were estimated by calibration curve construction and accuracy estimation by leave-one-out cross-validation procedure. Laser induced breakdown spectroscopy and X-ray fluorescence spectroscopy techniques comparison revealed better results for laser induced breakdown spectroscopy analysis. Improved accuracy of analysis and capability to quantify light elements (carbon etc.) demonstrated large perspectives of laser induced breakdown spectroscopy as a technique for express on-site multelement analysis of powder materials utilized in additive technologies. Laser induced breakdown spectroscopy is an express multielemental analytical technique for analysis of almost any sample in any environment. LIBS technique utilized powerful laser pulse to induce plasma providing emission spectrum which is further analyzed according to atomic/ionic lines. LIBS is a laser based analytical technique quantifying elemental composition with high lateral resolution (typically, 10-50 µm) including depth profile analysis without any sample preparation . The remarkable LIBS feature is a capability to perform simultaneous chemical mapping of almost all elements including light elements as carbon, boron or silicon. A feasibility of laser induced breakdown spectroscopy (LIBS) for quantitative analysis of metal powders utilized in additive technologies was demonstrated for the first time. A simple and effective sampling procedure of loose metal powder on double sided adhesive tape was utilized. LIBS mapping revealed that uniform grains distribution can be achieved for adhesive tape sampling despite 3-fold difference of WC and 1540-alloy particles densities. Sampling area dimensions was optimized to fulfill requirements for representative LIBS analysis while minimizing time needed for LIBS measurements. LIBS analytical capabilities for tungsten and carbon analysis were estimated by calibration curve construction with focusing on linearity and root mean square of cross-validation (RMSECV) metrics. LIBS results for tungsten analysis was better than for XRF measurements due to better reproducibility of sampling procedure. LIBS technique was also capable to quantitatively analyze carbon in metal powders. Current study revealed bright perspectives of LIBS for express on-site analysis of powder materials utilized in additive
a. technologies b. methods c. samples d. analysis.
Q30. arXiv:1802.00395 [cond-mat.mes-hall]: Hole spin resonance in Ge double quantum dots: Hannes Watzinger et al., (Submitted on 1 Feb 2018): ABSTRACT: Spins in isotopically purified Si have shown record coherence times and fidelities making them promising candidates for scalable quantum circuits. One of the key ingredients for realizing such circuits will be a strong coupling of spins to superconducting resonators. This has been recently achieved for Si by dressing electrons with spin orbit coupling. Ge, on the other hand, has by itself strong and tunable spin orbit coupling and gives good contacts to superconductors. However, in Ge no spin qubit has been realized so far. Here we do a first important step in this direction. We demonstrate for the first time electric dipole spin resonance (EDSR) of holes in Ge. From the line width of the EDSR peak we extract a lower limit for the dephasing time of about 70\,ns. The obtained results underline the importance of Ge as an alternative system for the realization of scalable hole spin qubits. A solution can come from so called hut wires (HWs), Ge nanowiresmonolithically grown on Si with a height of about 2nm.17–21 As has been very recently reported,19 holes localized in Ge HWs are of almost pure heavy-hole (HH) character making them thus an appealing system for hosting hole qubits with long dephasing times.22 To move towards a Ge spin 3/2 qubit we have realized double quantum dot (DQD) devices from HWs. By using PSB in DQD we have demonstrated electrically driven hole spin rotations in Ge. The reported dephasing times in combination with the strong spin orbit interaction underline the potential of holes in Ge as long lived electrically tunable spin qubits. In addition, their good electrical contacts to superconductors make them promising candidates for strong coupling to superconducting cavities. Such strong spin-photon coupling will pave the wave towards long-range two qubit-gates and spin
a. orderliness b. flipping c. entanglement d. connections
a. parameter b. Spin Vector c. Ferromagnet d. subscript
Q43.arXiv:1802.02930 [q-bio.NC]: Evolution of the Science Fiction Writer's Capacity to Imagine the Future: Liane Gabora:(Submitted on 7 Feb 2018): ABSTRACT: Drawing upon a body of research on the evolution of creativity, this paper proposes a theory of how, when, and why the forward-thinking story-telling abilities of humans evolved, culminating in the visionary abilities of science fiction writers. The ability to recursively chain thoughts together evolved approximately two million years ago. Language abilities, and the ability to shift between different modes of thought, evolved approximately 100,000 years ago. Science fiction dates to at least the second Century AD. It is suggested that well before this time, but after 100,000 years ago, and concurrent with the evolution of a division of labour between creators and imitators there arose a division of labour between past, present, and future thinkers. Agent-based model research suggests there are social benefits to the evolution of individual differences in creativity such that there is a balance between novelty-generating creators and continuity-perpetuating imitators. A balance between individuals focused on the past, present, and future would be expected to yield similar adaptive benefits. FEATURES: the earliest forms of storytelling are thought to be oral, in conjunction with gestures and expressions (Banks-Wallace 2002). It was possible to think about an idea in relation to other closely related ideas and thereby forge clusters of mutually consistent ideas, which allowed for a narrow kind of creativity, limited to minor adaptations of existing ideas. However, the mind was not integrated, nor truly creative, until it could forge connections between seemingly disparate ideas as in the formation of analogies. The ancient Indian thought contributed a lot to human creativity as evident in Jataka Stories, Panch Tantra episodes, Kalidas's Sanskrit revelations, Home embedded children stories, King and Queen episodes, Arya Bhattaas Cosmic statements etc. Futurists, inventors, and writers of science fiction, are more likely to focus on, and think most clearly about, the future. It is not that they cannot or do not think about the past or present but, that they tend to view the past and present as seeds for speculation and prediction about what has yet to pass. Thus, it is proposed that the evolution of individual differences in the extent to which we focus along the spectrum from past to present to future paved the way for the fantastical stories of future events and far-off worlds that we now enjoy. The ‘divide and conquer’ strategy is well-known to Mother Nature, and it has previously been suggested that its effectiveness can account for individual differences in human creativity. Skillful use of it by the Foreign rulers in India has not destroyed the native and sole power of Indian Thought and revealed the Hindu diversity in Science episodes projection with objective
a. projection b. thoughts c.reality d. confirmation
Q44.arXiv:1802.03451 [stat.ML]: Estimating the Spectral Density of Large Implicit Matrices: Ryan P. Adams et al. (Submitted on 9 Feb 2018): ABSTRACT: Many important problems are characterized by the eigenvalues of a large matrix. For example, the difficulty of many optimization problems, such as those arising from the fitting of large models in statistics and machine learning, can be investigated via the spectrum of the Hessian of the empirical loss function. Network data can be understood via the eigenstructure of a graph Laplacian matrix using spectral graph theory. Quantum simulations and other many-body problems are often characterized via the eigenvalues of the solution space, as are various dynamic systems. However, naive eigenvalue estimation is computationally expensive even when the matrix can be represented; in many of these situations the matrix is so large as to only be available implicitly via products with vectors. Even worse, one may only have noisy estimates of such matrix vector products. In this work, we combine several different techniques for randomized estimation and show that it is possible to construct unbiased estimators to answer a broad class of questions about the spectra of such implicit matrices, even in the presence of noise. We validate these methods on large-scale problems in which graph theory and random matrix theory provide ground truth. DETAILS:The behaviors of scientific phenomena and complex engineered systems are often characterized via matrices. The entries of these matrices may reflect interactions between variables, edges between vertices in a graph, or the local geometry of a complicated surface. When the systems under consideration become large, these matrices also become large and it rapidly becomes uninformativy and potentially infeasible, to investigate the individual entries. Instead, we frame our questions about these matrices in terms of aggregate properties that are insensitive to irrelevant details. Discussion: In this work we have described a framework for estimation of spectral densities of large matrices. Our primary objective has been to construct a tool for the empirical investigation of matrices that can only be probed in implicit and noisy ways. Our overall approach has been to combine ideas that have been proposed across several different fields into an estimation framework that provides unbiased estimates with controlled variance, even when the matrices become large. We use this framework to then construct smoothed estimates of the overall density. This smoothing necessarily introduces bias, but it allows us to visualize spectra whose atomic nature would otherwise make them difficult to
a. interrogate b. evaluate c. discuss d. project
Q45. arXiv:1802.03785 [eess.SP]: Generalized Uncertainty Principles for the Offset Linear Canonical Transform: Haiye Huo: (Submitted on 11 Feb 2018): ABSTRACT:The offset linear canonical transform (OLCT) provides a more general framework for a number of well known linear integral transforms in signal processing and optics, such as Fourier transform, fractional Fourier transform, linear canonical transform. In this paper, to characterize simultaneous localization of a signal and its OLCT, we generalize some different uncertainty principles (UPs), including Nazarov's UP, Hardy's UP, Beurling's UP, logarithmic UP and entropic UP, which have already been well studied in the Fourier transform domain over the last few decades, to the OLCT domain in a broader sense. DETAILS: Uncertainty principle (UP) plays an important role in quantum mechanics [7] and signal processing [2]. In quantum mechanics, UP was first proposed by the German physicist W. Heisenberg in 1927 [7]. It indicates that the position and momentum of the particles cannot have finite values at the same time, i.e., the more precisely the position is determined, the less precisely its momentum can be known. From the perspective of signal processing, UP can be described as follows: “One cannot sharply localize a nonzero function and its Fourier transform simultaneously”. By using different notations of essential support, there are many different kinds of UPs associated with the transform, like Heisenberg’s UP [1927)] Nazarov’s UP [(1993), Hardy’s UP (1933), Beurling’s UP (2007), logarithmic UP (1995), entropic UP (1957), and so on. UPs associated with transforms
a. of momentum b. transverse c. longitudinal d. Fourier
Q46.arXiv:1802.03393 [cs.CY]: A Study of WhatsApp Usage Patterns and Prediction Models without Message Content. Avi Rosenfeld et al. (Submitted on 9 Feb 2018):ABSTRACT: Internet social networks have become a ubiquitous application allowing people to easily share text, pictures, and audio and video files. Popular networks include WhatsApp, Facebook, Reddit and LinkedIn. We present an extensive study of the usage of the WhatsApp social network, an Internet messaging application that is quickly replacing SMS messaging. In order to better understand people's use of the network, we provide an analysis of over 6 million messages from over 100 users, with the objective of building demographic prediction models using activity data. We performed extensive statistical and numerical analysis of the data and found significant differences in WhatsApp usage across people of different genders and ages. We also inputted the data into the Weka data mining package and studied models created from decision tree and Bayesian network algorithms. We found that different genders and age demographics had significantly different usage habits in almost all message and group attributes. We also noted differences in users' group behavior and created prediction models, including the likelihood a given group would have relatively more file attachments, if a group would contain a larger number of participants, a higher frequency of activity, quicker response times and shorter messages. We were successful in quantifying and predicting a user's gender and age demographic. Similarly, we were able to predict different types of group usage. All models were built without analyzing message content. We present a detailed discussion about the specific attributes that were contained in all predictive models and suggest possible applications based on these results. CONCLUSIONS: we found that many message and group characteristics significantly differed across users of different demographics, such as gender and age, and present these results through performing extensive statistical analysis. Additionally, we believe that one key novelty of this work is that we use data analytics to predict users’ gender, age and group activity. As our work is data driven, we base our findings on the algorithms’ output, and did not attempt to verify any specific thesis as had been previously done. This is one key advantage to using data analytics, and this difference is especially clear from the decision ......... results presented in this paper.
a. uphill b. tree c. branch d. futuristic
Q47.arXiv:1802.03712 [cs.CL]: Syntax and Semantics of Italian Poetry in the First Half of the 20th Century. Rodolfo Delmonte (Submitted on 11 Feb 2018): ABSTRACT: In this paper we study, analyse and comment rhetorical figures present in some of most interesting poetry of the first half of the twentieth century. These figures are at first traced back to some famous poet of the past and then compared to classical Latin prose. Linguistic theory is then called in to show how they can be represented in syntactic structures and classified as noncanonical structures, by positioning discontinuous or displaced linguistic elements in Spec XP projections at various levels of constituency. Then we introduce LFG (Lexical Functional Grammar) as the theory that allows us to connect syntactic noncanonical structures with informational structure and psycholinguistic theories for complexity evaluation. We end up with two computational linguistics experiments and then evaluate the results. The first one uses best online parsers of Italian to parse poetic structures; the second one uses Getarun, the system created at Ca Foscari Computational Linguistics Laboratory. As will be shown, the first approach is unable to cope with these structures due to the use of only statistical probabilistic information. On the contrary, the second one, being a symbolic rule based system, is by far superior and allows also to complete both semantic an pragmatic
a. analysis b. results c. consistency d. orientation
Q48. arXiv:1802.03469 [nucl-th]: Cosmological Lithium Problems, C.A. Bertulani etal.,(Submitted on 9 Feb 2018): ABSTRACT: We briefly describe the cosmological lithium problems followed by a summary of our recent theoretical work on the magnitude of the effects of electron screening, the possible existence of dark matter parallel universes and the use of non-extensive (Tsallis) statistics during big bang nucleosynthesis. Solutions within nuclear physics are also discussed and recent measurements of cross-sections based on indirect experimental techniques are summarized. DARK MATTER: Most of the matter in the universe consists of an obscure kind of Dark Matter (DM) which interacts very weakly with the visible matter. In fact, we only know that it interacts gravitationally and large scale experimental searches are underway to identify if DM interacts with visible matter by other means [31–33]. The existence of DM is based on astronomical observations of galaxy clusters dynamics and on the anisotropies of the Cosmic Microwave Background (CMB). Perhaps Weakly Interacting Massive Particles (WIMPs),supersymmetric particles, sterile neutrinos,or any other hitherto undiscovered particles are responsible for its composition. It has also been hypothesized that DM is a mirror sector of particles such as dark photons, dark electrons, etc., which interact in nearly the same way as Standard Model (SM) particles, but only within their own sector. They interact very weakly across sectors, i.e. between the DM sector and the visible sector. Besides, the particle copies in the dark sector do not need to have the same masses and couplings as in the visible sector, opening a huge number of possible scenarios for DM. The work published was cited as a research highlight by the American Astronomical Society. It attests the relevance of the lithium puzzle and the anxiety that its solution entails for the astronomical community. The puzzle has been around the literature for a few decades already. The exercise played shows that a solution might be the outcome of a fine tuning of the physics during the
a. SM b. DM c. BBN d. DSM
Q49. arXiv:1802.02864 [hep-ph]: Gauge Invariant Noether's Theorem and The Proton Spin Crisis: Gouranga C Nayak: (Submitted on 8 Feb 2018): ABSTRACT: Due to proton spin crisis it is necessary to understand the gauge invariant definition of the spin and orbital angular momentum of the quark and gluon from first principle. In this paper we derive the gauge invariant Noether's theorem by using combined Lorentz transformation plus local gauge transformation. We find that the notion of the gauge invariant definition of the spin (or orbital) angular momentum of the electromagnetic field does not exist in Dirac-Maxwell theory although the notion of the gauge invariant definition of the spin (or orbital) angular momentum of the electron exists. We find that the gauge invariant definition of the spin angular momentum of the electromagnetic field in the literature is not correct because of the non-vanishing surface term in Dirac-Maxwell theory although the corresponding surface term vanishes for linear momentum. We also show that the Belinfante-Rosenfeld tensor is not required to obtain symmetric and gauge invariant energy-momentum tensor of the electron and the electromagnetic field in Dirac-Maxwell theory. DETAILS: The spin of the proton at rest is 1/2. When the proton is in motion, like that at high energy colliders, its helicity (which is the projection of the proton spin along its direction of motion) is conserved with the quantized value ±1/2. In the naive parton model it was predicted that the proton spin is carried by the quarks (plus antiquarks) inside the proton. However, the famous European muon collaboration (EMC) experiment at CERN revealed that the total contribution to the proton spin from the quarks (plus antiquarks) is almost zero. This is known as the ”proton spin crisis” which is one of the most important unsolved problem in particle physics. CONCLUSIONS:Due to proton spin crisis it is necessary to understand the gauge invariant definition of the spin and orbital angular momentum of the quark and gluon from first principle. In this paper we have derived the gauge invariant Noether’s theorem by using combined Lorentz transformation plus local gauge transformation. We have found that the notion of the gauge invariant definition of the spin (or orbital) angular momentum of the electromagnetic field does not exist in Dirac-Maxwell theory although the notion of the gauge invariant definition of the spin (or orbital) angular momentum of the electron exists. We have found that the gauge invariant definition of the spin angular momentum of the electromagnetic field in the literature, is not correct because of the non-vanishing surface term, in Dirac-Maxwell theory although the corresponding surface term vanishes for linear momentum. We have also shown that the Belinfante-Rosenfeld tensor is not required to obtain symmetric and gauge invariant energy-momentum tensor of the electron and the electromagnetic field in Dirac-Maxwell theory. Hence we conclude that although the high energy collider experiments have measured the spin dependent gluon distribution function inside proton but we do not have a gauge invariant definition of the spin dependent gluon distribution function in QCD consistent with the gauge invariant theorem by,
a. Maxwell b. Noether's c. Gouarang Naik d. Dirac
Q50. arXiv:1803.01452 [astro-ph.EP]: The when and where of water in the history of the universe: Karla de Souza Torres, Othon Cabo Winter, (Submitted on 5 Mar 2018): ABSTRACT:It is undeniable that life as we know it depends on liquid water. It is difficult to imagine any biochemical machinery that does not require water. On Earth, life adapts to the most diverse environments and, once established, it is very resilient. Considering that water is a common compound in the Universe, it seems possible (maybe even likely) that one day we will find life elsewhere in the universe. In this study, we review the main aspects of water as an essential compound for life: when it appeared since the Big Bang, and where it spread throughout the diverse cosmic sites. Then, we describe the strong relation between water and life, as we know it. DETAILS:Two thirds of the Earth’s surface is covered by water, however fresh water is most valuable as a resource for animals and plants. Thus, sustainability of our planet’s fresh water reserves is an important issue as population numbers increase. Water accounts for 75% of human body mass and is the major constituent of organism fluids. All these facts indicate that water is one of the most important elements for life on Earth. Thus, “follow the water” has become a mantra of the science of astrobiology. At standard pressure1, water boils at 100◦C. The pressure on the top of Mount Everest is 260Pa, where the boiling point of water is 69C. NUCLEOSYNTHESIS OF CARBON AND OXYGEN: When the fusion of protons into helium continues until the star has exhausted its hydrogen, the temperature in its core rises to about a few times 108 K, allowing the fusion of helium into heavier nuclei. In the first reaction two nuclei of helium, 4He, fuse with each other, creating the nucleus of beryllium, 8Be. However, the 8Be nucleus has an extremely short mean life of just 1016 s, before it decays back again to two 4He nuclei. The rate of production equals the rate of destruction of 8Be nucleus: 4He +4 He ↔8 Be (.4) Nevertheless, the 8Be can capture another 4He nucleus producing the 12C nucleus by the reaction: 8Be +4 He −→12 C + γ (.5) The reactions in Equations .4 and .5 are called the triple-alpha reaction, because three 4He nuclei or alpha particles are necessary for the creation of 12C. This reaction can only create carbon in appreciable amounts because of the existence of a resonance in 12C at the relevant energy for helium burning. Through this resonance the reaction in Equation .5 is enhanced by many orders of magnitude. The production of oxygen nuclei 16O is the result of a capture of another 4He nucleus by the carbon nuclei created in helium burning: 12C +4 He −→16 O + γ (.6) About half of the carbon nuclei produced are converted into
a. helium b. nucleus c. berillium d. oxygen
Q51. arXiv:1803.01157 [gr-qc]: Parameterizing theories of gravity on large and small scales in cosmology, Timothy Clifton, Viraj A. A. Sanghai, (Submitted on 3 Mar 2018); ABSTRACT: We present a link between parameterizations of alternative theories of gravity on large and small scales in cosmology. This relationship is established using theoretical consistency conditions only. We find that in both limits the "slip" and "effective Newton's constant" can be written in terms of a set of four functions of time, two of which are direct generalizations of the α and γ parameters from post-Newtonian physics. To the best of our knowledge, this is the first time that a link between parameterizations of gravity on these very different scales has been established. We expect our result to facilitate the imposition of observational constraints, by drastically reducing the number of functional degress of freedom required to consistently test gravity on multiple scales in cosmology. Conclusions – We have obtained a direct link between horizon-sized cosmological perturbations, and those on smaller non-linear scales, in terms of a set of just four functions of time: {α,γ,αc,γc}. This set of functions parameterize a wide array of minimal modifications to GR, of the type that has been long used to test gravity in the Solar System and binary pulsars. Here we have found that they can be used to describe gravitational physics in the Solar System, astrophysical and small cosmological scales, all the way up to super-horizon scales. To the best of our knowledge, this is the first time that theories of gravity have been parameterized consistently on such a large range of scales, using such a compact set of parameters. These results can be contrasted with the parameterized post-Friedmannian (PPF) and effective field theory (EFT) approaches, which can contain larger numbers of unknown functions, and that often require the degrees of freedom in the theory to be specified from the outset. We expect our parameterization to be useful for testing minimal deviations from GR with future large-scale
a. sets b. surveys c. parameters d. pulsars
Q52. arXiv:1803.01287 [hep-th]: Cosmological correlation functions including a massive scalar field and an arbitrary number of soft-gravitons. Ryo Saito, (Submitted on 4 Mar 2018): ABSTRACT: We study the imprint of a massive scalar particle on cosmological correlation functions, and suggest the way to determine the mass of the newly introduced particle, which is expected to be around 10^14 GeV. After reviewing the basic theory by Maldacena and the effective field theory (EFT) of inflation by Cheung et al., we apply these two theories to construct new couplings of a massive scalar field with primordial fluctuations including an arbitrary number of gravitons. We compute some correlation functions including these couplings in the soft-graviton limit. We show that when the number of soft-gravitons is getting larger, the peak of the correlation function is shifted to larger mass of the scalar particle. In addition we derive a relation, which relates correlation functions with N+1 to N soft-gravitons when the mass of the scalar particle becomes much higher than 10^14 GeV, and confirm the relation by numerical analysis. DETAILS: The methods to obtain the information during inflation have been developed in various ways. One of the most innovative works was done by Maldacena, who applied the quantum field theory to cosmology and computed the three point functions of primordial fluctuations, ζ (scalar fluctuation) and γij (tensor fluctuation or ‘graviton’). Especially the three point function of ζ is important because it tells us the deviation from the Gaussian features of the cosmic state, which is called ‘non-Gaussianity’. CONCLUSIONS:The mass can be around 1014 GeV, which can be estimated as the energy scale during inflation and cannot be detected in terrestrial accelerators. Such a way, which regards inflation as a particle detector, has been developed recently; considering higher spins[8][9], the Standard Model background[10], and so on. Therefore, we hope that our results will give one of the hints to the future observation to seek for unknown
a. spins b. gravitons c. particles d. Quanta
Q53. Ph.D. Thesis by Lady Marjolein Helder: Founder Plant-e from Netherlands: Three plant species were tested (Arundo donax, Spartina anglica and Arundinella anomala). With two of those, Spartina anglica and Arundinella anomala, we were capable of producing bio-electricity and biomass concurrently in the P-MFC. Spartina anglica outperformed Arundinella anomala considering maximum power output (0.22 W m^-2 vs. 0.021 W m^-2). Since Spartina anglica outperformed Arundinella anomala and Spartina anglica is a salttolerant species that can be found under various circumstances around the world, we focused on Spartina anglica for the rest of the thesis. SUMMARY: With Spartina anglica, the maximum power density of the P-MFC was increased to 0.22 W m-2, over 3 times as much as in the first experiment by Strik et al. in 2008. Power output could not be maintained over a longer period of time and polarisation curves showed the anode to be limiting the power output. The plant-growth medium used in the P-MFC contained a lot of nitrate. Removing the nitrate from the plant-growth medium and replacing it for ammonium led to a maximum power density of 0.21 W m-2, and maintain a much higher power density over a longer period of time; 0.15 W m-2. Removing sulphate from the plant-growth medium did not lead to higher power densities. Removal of sulphate from the plant-growth medium resulted in a decrease in power output. The effect of sulphur-cycling within the anode of the P-MFC is still not fully understood and should be researched further. When taking the normal projected efflux of total carbon in the form of CO2 from pastures of 0.09-0.12 kg C m-2 year-1, we could theoretically produce 30-40 mols of electrons per m^2 per year. This would lead to a current density of 0.092-0.122 A m^-2, which was regularly achieved or exceeded during this and other researches. At a voltage of 0.5 V – a cautious estimate of 50% voltage efficiency for the MFC – a power density of 0.046-0.061 W m-2 would be achieved. This is lower than the power density achieved before the start of this thesis project. Three explanations are possible for this difference in numbers: 1. We overestimated our power output per m^2 due to overestimation of the biomass growth. Data from Kuzyakov underestimate the efflux of C from the soil, so in practice breakdown of organic matter is faster than projected and more electrons are released. 2. Microbial activity and carbon turnover is enhanced in the P-MFC due to the availability a new electron-acceptor in the form of the anode. The results with the new plant-growth medium were achieved in a new flat-plate design PMFC. The flat-plate design resulted in a lower internal resistance for the P-MFC as compared to the previously used tubular P-MFC. In total internal resistance can maximally be 0.094 Ω.m^2 in order to reach 3.2 W m^-2. Internal resistance in our experiments ranges from 2-10 Ω.m^2, so power density doesn’t exceed 0.4 W m^-2 and current density doesn’t exceed 1.6 A m^-2. In the tubular system highest partial internal resistance was transport resistance, which was limited in the flat-plate system due to a smaller anode-cathode
a. distance b. power c. area d. configuration.
Q54. arXiv:1803.01639 [q-bio.PE]: When do we have the power to detect biological interactions in spatial point patterns? T. Rajala, S. Olhede, D.J. Murrell: (Submitted on 5 Mar 2018): ABSTRACT: Determining the relative importance of environmental factors, biotic interactions and stochasticity in assembling and maintaining species-rich communities remains a major challenge in ecology. In plant communities, interactions between individuals of different species are expected to leave a spatial signature in the form of positive or negative spatial correlations over distances relating to the spatial scale of interaction. Most studies using spatial point process tools have found relatively little evidence for interactions between pairs of species. More interactions tend to be detected in communities with fewer species. However, there is currently no understanding of how the power to detect spatial interactions may change with sample size, or the scale and intensity of interactions. We use a simple 2-species model where the scale and intensity of interactions are controlled to simulate point pattern data. In combination with an approximation to the variance of the spatial summary statistics that we sample, we investigate the power of current spatial point pattern methods to correctly reject the null model of bivariate species independence. We show that the power to detect interactions is positively related to the abundances of the species tested, and the intensity and scale of interactions. Increasing imbalance in abundances has a negative effect on the power to detect interactions. At population sizes typically found in currently available datasets for species-rich plant communities we find only a very low power to detect interactions. Differences in power may explain the increased frequency of interactions in communities with fewer species. Furthermore, the community-wide frequency of detected interactions is very sensitive to a minimum abundance criterion for including species in the analyses. In conclusion, we hope our main contribution is to encourage more users to consider explicitly the ability of the spatial point pattern tests to detect significant associations between species. We have shown that the data requirements to detect even strong interactions may be quite high, mirroring results for null model tests of species co-occurrences in community matrix data. On this basis, we suggest it is desirable to only interpret the frequency of interactions across large numbers of species once the effect of different powers to detect interactions for pairs of species of given population sizes has been (even approximately) factored out. This seems especially important in comparative analyses across different communities where the spatial scales, strengths of interactions and the species abundance distributions may differ and affect the power to detect
a. abundances b. methods c. communities d. interactions
Q55.arXiv:1803.00940 [cs.CV]: Protecting JPEG Images Against Adversarial Attacks: Aaditya Prakash, Nick Moran, Solomon Garber, Antonella DiLillo, James Storer: (Submitted on 2 Mar 2018): ABSTRACT: As deep neural networks (DNNs) have been integrated into critical systems, several methods to attack these systems have been developed. These adversarial attacks make imperceptible modifications to an image that fool DNN classifiers. We present an adaptive JPEG encoder which defends against many of these attacks. Experimentally, we show that our method produces images with high visual quality while greatly reducing the potency of state-of-the-art attacks. Our algorithm requires only a modest increase in encoding time, produces a compressed image which can be decompressed by an off-the-shelf JPEG decoder, and classified by an unmodified classifier. DETAILS: Deep neural networks (DNNs) have shown tremendous success in image recognition tasks, even surpassing human capability. DNNs have become components of many critical systems, such as self-driving cars, medical image segmentation, surveillance, and malware classification. However, recent research has shown that DNNs are vulnerable to adversarial attacks, in which minute, carefully-chosen image perturbations can result in misclassification of the image by the neural network. In most cases, this change is imperceptible to humans (the resulting image is visually indistinguishable from the original). CONCLUSIONS:We have presented Aug-MSROI, an augmentation of MSROI [17] to employ semantic JPEG compression as an effective defenseagainststate-of-the-artadversarialattacks. In our experiments, JPEG compression employing Aug-MSROI produces compressed images, which, when decompressed, have high visual quality while at the same time preserving the accuracy of classification by a neural network. A key advantage of our approach is that, with only a modest increase in encoding time, like standard MSROI, it produces compressed images that can be decompressed by any off-the-shelf JPEG
a. segment b. decoder c. encoder d. Splaser
Q56. arXiv:1803.02163 [astro-ph.HE]: Revisit of cosmic ray antiprotons from dark matter annihilation with updated constraints on the background model from AMS-02 and collider data: Ming-Yang Cui, Xu Pan, Qiang Yuan, Yi-Zhong Fan, Hong-Shi Zong: (Submitted on 6 Mar 2018): ABSTRACT: We study the cosmic ray antiprotons with updated constraints on the propagation, proton injection, and solar modulation parameters based on the newest AMS-02 data near the Earth and Voyager data in the local interstellar space, and on the cross section of antiproton production due to proton-proton collisions based on new collider data. We use a Bayesian approach to properly consider the uncertainties of the model predictions of both the background and the dark matter (DM) annihilation components of antiprotons. We find that including an extra component of antiprotons from the annihilation of DM particles into a pair of quarks can improve the fit to the AMS-02 antiproton data considerably. The favored mass of DM particles is about 60∼100GeV, and the annihilation cross section is just at the level of the thermal production of DM (⟨σv⟩∼O(10^−26) cm^ 3~s^−1). DETAILS: Cosmic ray (CR) antiprotons are one of the most important probes to indirectly detect dark matter (DM) particles.The antiproton background produced by inelastic collisions between protons and the interstellar medium can be calculated using the same propagation, proton injection, and solar modulation parameters (referred to as background parameters hereafter) obtained through fitting to the proton flux data. CONCLUSIONS: We find that the AMS-02 antiproton data favor a DM component with mass of 60 ∼ 100 GeV and annihilation cross section of (0.7 ∼ 7)× 10−26 cm3 s−1, for an assumed b¯ b channel. The Bayes factor of the DM component is about 8.4. These results are consistent with previous works based on different propagation parameters and antiproton production cross sections. There is probably one caveat of the current study. We have assumed that the solar modulation effects of protons and antiprotons are similar, with the only difference of the data-taking time which corresponds to different solar activities. It is, however, possible that the solar modulation is charge-sign-
a. Independant b. Oscillatory c. dependant d. reversal.
Q57. arXiv:1803.01866 [hep-ph]: Spin-2 Portal Dark Matter: Nicolas Bernal, Maira Dutra, Yann Mambrini, Keith A. Olive, Marco Peloso, Mathias Pierre;(Submitted on 5 Mar 2018); ABSTRACT: We generalize models invoking a spin-2 particle as a mediator between the dark sector and the Standard Model. We show that a massive spin-2 messenger can efficiently play the role of a portal between the two sectors. The dark matter is then produced via a freeze-in mechanism during the reheating epoch. In a large part of the parameter space, production through the exchange of a massive spin-2 mediator dominates over processes involving a graviton with Planck suppressed couplings. We perform a systematic analysis of such models for different values of the spin-2 mass relative to the maximum and the final temperature attained at reheating. DETAILS: Although there is a large amount of indirect evidence for the presence of dark matter in the Universe from astrophysical observations, its precise nature remains elusive. Moreover, although there has been an impressive increased sensitivity in direct and indirect detection searches, no signal has been confirmed so far. CONCLUSIONS: We generalized our study to any massive spin-2 state with stress-energy tensor couplings to the standard model and the dark sector. In a large part of the parameter space, the massive spin-2 portal dominates over the (Planck-suppressed) graviton exchange. We have performed an exhaustive analysis, considering cases where the spin-2 field is both heavier and lighter than the reheating temperature. In both cases, the freeze-in process dominates the production, while enhanced during the reheating phase (heavy mediator case) or through its resonant production (light mediator case). We have also shown that our results are greatly influenced by taking into account the effects of non-instantaneous reheating. Not only do we recover boost factors in the production due to the large dependence on the temperature of the rate R(T), but we have also shown that the presence of a mediator between TRH and Tmax strongly enhances the relic abundance due to rapid s-channel production when T ~ m˜ h. IMPORTANT:We have shown that dark matter can naturally be produced through a spin-2
a. portal b. graviton c. mass d. state
Q58. arXiv:1803.01109 [gr-qc]: Structure of Strange quark star in dilaton gravity: A.R.Peivand, K.Naficy, G.H.Bordbar; (Submitted on 3 Mar 2018): ABSTRACT: In this work, we have first obtained the hydrostatic equilibrium equation in dilaton gravity. Then we have examined some of the structural characteristics of strange quark star in dilaton gravity with a background of Einstein gravity. We have shown that the variations of dilaton parameter do not affect the maximum mass of quark star, while the variations of the cosmological constant lead to change in the structural characteristics of the quark star. We have investigated the stability of strange quark stars that studied by MIT Bag model, in dilaton gravity. We have also provided limiting values for the dilaton field parameter and the cosmological constant.We have also studied the effects of dilaton gravity on the other properties of quark star such as the mean density and gravitational redshift. We have concluded that the last reported value for cosmological constant does not affect on maximum mass of strange quark star. CONCLUSIONS: We have obtained HEE of a compact object in dilaton gravity by using two approaches and then by using the obtained HEEs we have calculated some structural properties of SQS. We have assumed that the dilaton gravity has constructed from dilaton field with a potential, including two Liouville type terms in the background of Einstein gravity. We have seen that in the values of α and Λ where HEE in dilaton gravity has a logical answer, SQS does not change with variations of α. This behavior also persists in different values of the bag constant. On the other hand, increasing Λ enhances the maximum mass. We have seen that the percentage increase of maximum mass of SQS has higher values for SQSs that are more stable than others. We have shown that effect of dilaton gravity and applying smaller bag constant in EoS of SQM on the SQS has led to existence SQSs with bigger masses and radii that are more stable than SQSs in Einstein gravity. Since the values of Mmax and radius for Λ < 10^−14 are the same values for Λ = 0 and cosmological observations suggest Λ ≤ 3×10^−56cm^−2, it can be concluded that this limit of the cosmological constant does not affect on SQS structure in dilaton
a. cosmology b. HEE c. gravity d. gravitation
Q59. arXiv:1804.01234 [math-ph]:Taking Inspiration from Quantum-Wave Analogies --- Recent Results for Photonic Crystals: Max Lein, (Submitted on 4 Apr 2018): ABSTRACT: Similarities between quantum systems and analogous systems for classical waves have been used to great effect in the physics community, be it to gain an intuition for quantum systems or to anticipate novel phenomena in classical waves. This proceeding reviews recent advances in putting these quantum-wave analogies on a mathematically rigorous foundation for classical electromagnetism. Not only has this Schr\"odinger formalism of electromagnetism led to new, interesting mathematical problems for so-called Maxwell-type operators, it has also improved the understanding of the physics of topological phenomena in electromagnetic media. For example, it enabled us to classify electromagnetic media by their material symmetries, and explained why "fermionic time-reversal symmetries" --- that were conjectured to exist in the physics literature --- are in fact forbidden. CONCLUSIONS: In summary, the Schrödinger formalism of electromagnetism and other classical waves opens the door to systematically adapting techniques from quantum mechanics to classical Systematically developing mathematical techniques for Maxwell-type operators waves. Two specific cases were covered here, effective dynamics in adiabatically perturbed photonic crystals and the topological classification of electromagnetic media. This is not just relevant to mathematical physicists, but at least the latter result is new for and of immediate interest to physicists. Going forward, quantum-wave analogies will continue to serve as inspiration for mathematical, theoretical and experimental physicists. Experimentalists enjoy the much wider latitude with which media for classical waves can be engineered. Depending on the circumstances, they may choose the most suitable wave (acoustic, electromagnetic, etc.) and wavelength regime. For instance, the dynamics of spin wave packets can be “filmed” because their propagation speed is much lower than that of light, something that would be very hard to impossible to realize with a quantum system. Theoreticians can rely on quantum-wave or wave-wave analogies to transfer insights from one physical system to another and to propose novel experiments. And mathematicians can find a whole host of interesting and non-trivial problems that are of immediate relevance to
a. Physics b. Mathphysics c. quantum systems d. Media.
Q60. Xiv:1804.00963 [math.GR]: The Spin Group in Superspace: Hennie De Schepper, Alí Guzmán Adán, Frank Sommen: (Submitted on 3 Apr 2018): ABSTRACT: There are two well-known ways of describing elements of the rotation group SO(m). First, according to the Caarrtan-Dieudonn\'e theorem, every rotation matrix can be written as an even number of reflections. And second, they can also be expressed as the exponential of some anti-symmetric matrix. In this paper, we study similar descriptions of the corresponding extension of SO(m) to superspace. The setting is natural to describe the behavior of bosonic and fermionic particles. This group of super-rotations SO0is also an extension of the symplectic group. While still being connected, it is thus no longer compact. As a consequence, it cannot be fully described by just one action of the exponential map on its Lie algebra. Instead, we obtain an Iwasawa-type decomposition for this group in terms of three exponentials acting on three direct summands of the corresponding Lie algebra of supermatrices. At the same time, SO0 strictly contains the group generated by super-vector reflections. Therefore, its Lie algebra is isomorphic to a certain extension of the algebra of superbivectors. This means that the Spin group in superspace has to be seen as the group generated by the exponentials of the so-called extended superbivectors in order to cover SO0. We also study the actions of this Spin group on supervectors and provide a proper subset of it that is a double cover of SO0. Finally, we show that every fractional Fourier transform in n bosonic dimensions can be seen as an element of the spin group in superspace. Conclusions and future work: In this paper we have shown that vector reflections in superspace are not enough to describe the set of linear transformations leaving the inner product invariant. This constitutes a very important difference with the classical case in which the algebra of bivectors x ∧ y is isomorphic to the special orthogonal algebra so(m). Such a property is no longer fulfilled in this setting. The real projection of the algebra of superbivectors R(2) m|2n (ΛN) does not include the symplectic algebra structure which is present in the Lie algebra of supermatrices so0, corresponding to the group of super rotations. That fact has an major impact on the definition of the Spin group in this setting. The set of elements defined through the multiplication of an even number of unit vectors in superspace does not suffice for describing Spin(m|2n)(ΛN). A suitable alternative, in this case, is to define the (super) spin elements as products of exponentials of extended superbivectors. Such an extension of the Lie algebra of superbivectors contains, through the corresponding identifications, harmonic oscillators. This way, we obtain the Spin group as a cover of the set of superrotations SO0 through the usual representation h. In addition, every fractional Fourier transform can be identified with a spin element. In forthcoming work, we will prove the invariance of the (super) Dirac operator ∂x under the corresponding actions of this (super) Spin group. We will also study the invariance of the Hermitian system under the action of the corresponding Spin subgroup in superspace.
a. pseudospace b. superspace c. representation d. setting.
Q61. arXiv:1804.00548 [quant-ph]: Relativistic probability amplitudes I. Massive particles of any spin: Scott E. Hoffmann: (Submitted on 30 Mar 2018): ABSTRACT: We consider a massive particle of arbitrary spin and the basis vectors that carry the unitary, irreducible representations of the Poincar\'e group. From the complex coefficients in normalizable superpositions of these basis vectors, we identify momentum/spin-component probability amplitudes with the same interpretation as in the nonrelativistic theory. We find the relativistic transformations of these amplitudes, which are unitary in that they preserve the modulus-squared of scalar products from frame to frame. Space inversion and time reversal are also treated. We reconsider the Newton- Wigner construction of eigenvectors of position and the position operator. Position/spin-component probability amplitudes are also identified and their relativistic, unitary, transformations derived. Again, space inversion and time reversal are considered. For reference, we show how to construct positive energy solutions of the Klein-Gordon and Dirac equations in terms of probability amplitudes. We find the boost transformation of the position operator in the spinless case and present some results on the relativity of position measurements. We consider issues surrounding the classical concept of causality as it applies in quantum mechanics. We briefly examine the relevance of the results presented here for theories of interaction. CONCLUSIONS: We have defined momentum/spin-component probability amplitudes and position/spin-component probability amplitudes for a massive particle of general spin. We have found their transformation properties under space-time translations, general Lorentz transformations, space inversion and time reversal. We have defined the position operator and derived its relativistic transformation properties. The results are all very close to what is done in nonrelativistic quantum mechanics. This should come as no surprise, since any relativistic theory must reduce to the nonrelativistic form for small velocities. We discussed the limitations on the concept of causality imposed by the uncertainty principle. We discussed how relativistic probability amplitudes must be a part of any theory of interaction, including quantum field
a. expression b. theory c. probability d. transformation.
Answers
a. space b. field c. area d. region.
Q24. arXiv:1802.00191 [astro-ph.SR]: Powerful Solar Flares of September 2017: Correspondence Between Parameters of Microwave Bursts and Proton Fluxes near Earth I. M. Chertok, (Submitted on 1 Feb 2018): ABSTRACT: In this note, we consider radio characteristics of three proton flares that caused discrete enhancements of solar energetic particles (SEPs) near Earth. The analysis confirmed that the flux density and frequency spectrum of microwave bursts, although the latter are generated by electrons propagating to the photosphere, reflect the number and energy spectrum of accelerated particles, including the 10-100 MeV protons coming to Earth. A strong outburst of solar activity occurred on 2017 September 4–10, when approaching a minimum of Cycle 24. It was due to the sharp development and evolution of the active region 12673 during its passage across the western half of the visible disk. Numerous strong flares occurred at this time, including 27 M-class and 4 X-class flares. Among the latter, the X9.3 flare on September 6 was the most powerful in the last 10 years. It is not surprising that this activity and associated space weather disturbances arouse great interest, and many publications have already been devoted to their study. In this note, we consider radio characteristics of three proton flares that caused discrete enhancements of solar energetic particles (SEPs) near Earth.The September 10 event has quite different characteristics. Its radio spectrum shows a sharp increase from 3 to 15 GHz and should be considered as hard. The maximum radio flux at 15 GHz is very large S15 ≈ 21,000 sfu (1 sfu = 10−22 W m^−2 Hz^−1). In accordance with these radio parameters, the observed SEP, as a typical western event, was very intense (J10 ≈ 1000 pfu) and had a rather hard proton energy spectrum with γ ≈ 1.4. The September 6 event has intermediate features both on the radio spectrum and on the proton flux parameters. Its radio spectrum indicates a decimetre portion and an increasing microwave component with the peak flux at 15 GHz S15 ≈ 8100 sfu. This corresponds to the observed SEP of a rather hard energy spectrum with the index γ ≈ 1.5 estimated by the flux in the >50 and 100 MeV channels. Before and after this SEP, the >10 Mev proton flux was disturbed by CME from the September 4 flare and the subsequent geomagnetic
a. flare b. storm c. disturbance d. spectrum.
Q25.arXiv:1802.00204 [astro-ph.HE]:High-energy Emission Properties of Pulsars: Christo Venter, Alice K. Harding, Isabelle Grenier ABSTRACT: (Submitted on 1 Feb 2018):The sheer number of new gamma-ray pulsar discoveries by the Fermi Large Area Telescope (LAT) since 2008, combined with the quality of new multi-frequency data, has caused a revolution in the field of high-energy (HE) rotation-powered pulsars. These rapidly rotating neutron stars exhibit rich spectral and temporal phenomenology, indicating that there are still many unsolved mysteries regarding the magnetospheric conditions in these stars - even after 50 years of research! Indeed, 2017 marks the golden anniversary of the discovery of the first radio pulsar, and theorists and observers alike are looking forward to another half-century of discovery, with many new experiments coming online in the next decades. In this review paper, we will briefly summarise recent HE pulsar observations, mention some theoretical models that provide a basic framework within which to make sense of the varied measurements, and finally review some of the latest theoretical developments in pulsar emission modelling. DETAILS: Pulsars are seen across the electromagnetic spectrum. Their light curves vary with energy and time, but radio light curves1 averaged over pulsation period are usually quite stable. Their spectra span a very wide range in energy, making these rotating neutron stars true multi-frequency objects. Fundamental electrodynamical questions emerged: How and where is the current closed so that the outflow of particles is sustainable (i.e., what is the global current flow pattern)? What is the role of pair formation? What is the injection rate of plasma from the stellar surface? Where do acceleration gaps develop (where E|| is not fully screened) and how are they sustained? Where does acceleration of particles to relativistic energies take place? What is the emission mechanism for each of the multi-frequency components we observe? The conductivity in the macroscopic dissipative models is supplied by the electron-positron pair plasma at a microscopic level. Where and how this pair plasma originates is currently not completely understood. Important constraints on the location of pair plasma production in the pulsar magnetosphere as well as its spectrum will come from observations in the 100 keV to 10 MeV band. They assumed that optical to hard X-ray emission is produced by SR from electron-positron pairs and γ -ray emission is due to either CR or SR from primary
a. electrons b. protons c. pairs d. emissions
Q26. arXiv:1802.00224 [astro-ph.SR]: Polarimetry and Spectroscopy of the `Oxygen Flaring' DQ Herculis-like nova: V5668 Sagittarii (2015): E. J. Harveyet al., (Submitted on 1 Feb 2018): ABSTRACT: Classical novae are eruptions on the surface of a white dwarf in a binary system. The material ejected from the white dwarf surface generally forms an axisymmetric shell of gas and dust around the system. The three-dimensional structure of these shells is difficult to untangle when viewed on the plane of the sky. In this work a geometrical model is developed to explain new observations of the 2015 nova V5668 Sagittarii. To understand the ionisation structure in terms of the nova shell morphology and estimate the emission distribution directly following the light-curve's dust-dip. High-cadence optical polarimetry and spectroscopy observations of a nova are presented. The ejecta is modelled in terms of morpho-kinematics and photoionisation structure. Initially observational results are presented, including broadband polarimetry and spectroscopy of V5668 Sgr nova during eruption. Variability over these observations provides clues towards the evolving structure of the nova shell. The position angle of the shell is derived from polarimetry, which is attributed to scattering from small dust grains. Shocks in the nova outflow are suggested in the photometry and the effect of these on the nova shell are illustrated with various physical diagnostics. Changes in density and temperature as the super soft source phase of the nova began are discussed. Gas densities are found to be of the order of 10^9 cm ^−3 for the nova in its auroral phase. The blackbody temperature of the central stellar system is estimated to be around 2.2x10^5K at times coincident with the super soft source turn-on. It was found that the blend around 4640 $\rm{\AA}$ commonly called `nitrogen flaring' is more naturally explained as flaring of the O~{\sc ii} multiplet (V1) from 4638 - 4696 $\rm{\AA}$, i.e. `oxygen flaring'. Novae are known to be a distinct stellar event and in their simplest terms are considered as either fast (t3 < 20 days) or slow (t3 > 20 days, where t3 is the time taken for a nova’s magnitude to decrease by 3). Fast novae occur on more massive white dwarfs than slow novae and require less accreted matter in order to ignite the thermonuclear runaway and experience higher ejection velocities, e.g. Yaron et al. (2005). Slower novae counterparts typically occur on lower mass white dwarfs, eject more previously-accreted-material during eruption and the outflow has lower ejection velocities which creates rich dust formation factories. These objects are well observed during eruption where optical photometry and spectroscopy are the most thoroughly practiced approaches. Conclusions: The observations reveal variability of the absolute polarisation before and after nights that hint towards internal shocks in the nova outflow. Along with the available high-quality gamma, Xray, UV and IR observations on this nova, the polarimetry allowed for the estimation of the nova shell position angle and provided information on the dust grains causing the scattering. The spectroscopy then allowed for derivation of the physical conditions on separate nights, including outflow velocity and structure, nebular density, temperature and ionisation conditions. Following on from this extensive analysis, morpho-kinematic and photo-ionisation models were formulated and combined to give a deeper insight into the nova system as a whole. Finally we note that, for slow novae in particular, the regularly referred to ‘nitrogen flaring’ is in fact more likely to be ‘oxygen flaring’. Scattering due to
a. nitrogen flaring b. novae c. dust grains d. oxygen flaring.
Q27. arXiv:1801.03157 [gr-qc]: The massive Dirac equation in the curved spacetime of the Kerr-Newman (anti) de Sitter black hole: G. V. Kraniotis: (Submitted on 9 Jan 2018 (v1), last revised 30 Jan 2018 (this version, v2)): ABSTRACT: Exact solutions of the Dirac general relativistic equation that describe the dynamics of a massive, electrically charged with half integer spin particle in the curved spacetime geometry of an electrically charged, rotating Kerr-Newman-(anti) de Sitter black hole are investigated. We first, derive the Dirac equation in the Kerr-Newman-de Sitter (KNdS) black hole background using a generalised Kinnersley null tetrad in the Newman-Penrose formalism. Subsequently in this frame and in the KNdS black hole space-time, we prove the separation of the Dirac equation into ordinary differential equations for the radial and angular parts. For the case of a massive fermion in the background of a Kerr-Newman (KN) black hole we first prove that the radial and angular equations that result from the separation of Dirac's equation reduce to the generalised Heun differential equation (GHE). The local solutions of such GHE are derived and can be described by holomorphic functions whose power series coefficients are determined by a four-term recurrence relation. In addition using asymptotic analysis we derive the solutions for the massive fermion far away from the KN black hole and the solutions near the event horizon. details: The problem of massive perturbations in the strong gravity background of a black hole is a fascinating and of fundamental significance problem, as has been demonstrated recently for the case of scalar perturbations. Massive Fermion in
a. KN black hole b. KNdS black hole c. GHE d. event horizon.
Q28. arXiv:1801.08084 [gr-qc]: Regularity of high energy photon events from gamma ray bursts: Haowei Xu, Bo-Qiang Ma: (Submitted on 24 Jan 2018): The effect of Quantum Gravity (QG) may bring a tiny light speed variation as v(E)=c(1−E/ELV), where E is the photon energy and ELV is a Lorentz violation scale. A remarkable regularity was suggested in previous studies to look for the light speed variation from high energy photon events of Gamma Ray Bursts (GRBs). We provide a general analysis on the data of 25 bright GRBs observed by the Fermi Gamma-ray Space Telescope (FGST). Such method allows a completed scan over all possibilities in a more clean and impartial way without any bias compared to previous intuitive analysis. The results show that with the increase in the intrinsic energies of photons, such regularity truly emerges and gradually becomes significant. The speed of light is assumed to be a constant c in Einstein’s relativity. However, it is speculated from quantum gravity theories that Lorentz invariance is violated at the Planck scale (E ∼ EPl =sqrt(hcross*c5/G) ≈ 1.22×10^19 GeV. A possible consequence is that the speed of light is no longer a constant c but energy dependent. In conclusion, we use a general method to analyze the data of 25 bright GRBs detected by FGST. The results suggest that for photons with energy higher than 40 GeV, the regularity of high energy photon events from different GRB s exists at a significance of 3-5σ with ELV = 3.6×10^17 GeV determined by the GRB data. Tiny speed variation due to
a. ELV b. QG c. GRB d. FGST
Q29. arXiv:1802.00236 [physics.app-ph]: Laser induced breakdown spectroscopy for multielement analysis of powder materials utilized in additive technologies: V.N. Lednev et al.,, (Submitted on 1 Feb 2018): ABSTRACT: Powder materials utilized in additive technologies were quantitatively analyzed by laser induced breakdown spectroscopy for the first time. Laser induced breakdown spectroscopy mapping of loose metal powder attached to the double-sided adhesive tape provided high reproducibility of measurements even for powder mixtures with large difference of particles densities (tungsten carbide particles in nickel alloy powder). Laser induced breakdown spectroscopy analytical capabilities for tungsten and carbon analysis were estimated by calibration curve construction and accuracy estimation by leave-one-out cross-validation procedure. Laser induced breakdown spectroscopy and X-ray fluorescence spectroscopy techniques comparison revealed better results for laser induced breakdown spectroscopy analysis. Improved accuracy of analysis and capability to quantify light elements (carbon etc.) demonstrated large perspectives of laser induced breakdown spectroscopy as a technique for express on-site multelement analysis of powder materials utilized in additive technologies. Laser induced breakdown spectroscopy is an express multielemental analytical technique for analysis of almost any sample in any environment. LIBS technique utilized powerful laser pulse to induce plasma providing emission spectrum which is further analyzed according to atomic/ionic lines. LIBS is a laser based analytical technique quantifying elemental composition with high lateral resolution (typically, 10-50 µm) including depth profile analysis without any sample preparation . The remarkable LIBS feature is a capability to perform simultaneous chemical mapping of almost all elements including light elements as carbon, boron or silicon. A feasibility of laser induced breakdown spectroscopy (LIBS) for quantitative analysis of metal powders utilized in additive technologies was demonstrated for the first time. A simple and effective sampling procedure of loose metal powder on double sided adhesive tape was utilized. LIBS mapping revealed that uniform grains distribution can be achieved for adhesive tape sampling despite 3-fold difference of WC and 1540-alloy particles densities. Sampling area dimensions was optimized to fulfill requirements for representative LIBS analysis while minimizing time needed for LIBS measurements. LIBS analytical capabilities for tungsten and carbon analysis were estimated by calibration curve construction with focusing on linearity and root mean square of cross-validation (RMSECV) metrics. LIBS results for tungsten analysis was better than for XRF measurements due to better reproducibility of sampling procedure. LIBS technique was also capable to quantitatively analyze carbon in metal powders. Current study revealed bright perspectives of LIBS for express on-site analysis of powder materials utilized in additive
a. technologies b. methods c. samples d. analysis.
Q30. arXiv:1802.00395 [cond-mat.mes-hall]: Hole spin resonance in Ge double quantum dots: Hannes Watzinger et al., (Submitted on 1 Feb 2018): ABSTRACT: Spins in isotopically purified Si have shown record coherence times and fidelities making them promising candidates for scalable quantum circuits. One of the key ingredients for realizing such circuits will be a strong coupling of spins to superconducting resonators. This has been recently achieved for Si by dressing electrons with spin orbit coupling. Ge, on the other hand, has by itself strong and tunable spin orbit coupling and gives good contacts to superconductors. However, in Ge no spin qubit has been realized so far. Here we do a first important step in this direction. We demonstrate for the first time electric dipole spin resonance (EDSR) of holes in Ge. From the line width of the EDSR peak we extract a lower limit for the dephasing time of about 70\,ns. The obtained results underline the importance of Ge as an alternative system for the realization of scalable hole spin qubits. A solution can come from so called hut wires (HWs), Ge nanowiresmonolithically grown on Si with a height of about 2nm.17–21 As has been very recently reported,19 holes localized in Ge HWs are of almost pure heavy-hole (HH) character making them thus an appealing system for hosting hole qubits with long dephasing times.22 To move towards a Ge spin 3/2 qubit we have realized double quantum dot (DQD) devices from HWs. By using PSB in DQD we have demonstrated electrically driven hole spin rotations in Ge. The reported dephasing times in combination with the strong spin orbit interaction underline the potential of holes in Ge as long lived electrically tunable spin qubits. In addition, their good electrical contacts to superconductors make them promising candidates for strong coupling to superconducting cavities. Such strong spin-photon coupling will pave the wave towards long-range two qubit-gates and spin
a. orderliness b. flipping c. entanglement d. connections
Q31. arXiv:1802.02576 [astro-ph.SR]: The Chemical Homogeneity of Sun-like Stars in the Solar Neighborhood: Megan Bedell et al., (Submitted on 7 Feb 2018): ABSRACT: The compositions of stars are a critical diagnostic tool for many topics in astronomy such as the evolution of our Galaxy, the formation of planets, and the uniqueness of the Sun. Previous spectroscopic measurements indicate a large intrinsic variation in the elemental abundance patterns of stars with similar overall metal content. However, systematic errors arising from inaccuracies in stellar models are known to be a limiting factor in such studies, and thus it is uncertain to what extent the observed diversity of stellar abundance patterns is real. Here we report the abundances of 30 elements with precisions of 2% for 79 Sun-like stars within 100 parsecs. Systematic errors are minimized in this study by focusing on solar twin stars and performing a line-by-line differential analysis using high-resolution, high-signal-to-noise spectra. We resolve [X/Fe] abundance trends in galactic chemical evolution at precisions of 10^-3 dex Gyr^-1 and reveal that stars with similar ages and metallicities have nearly identical abundance patterns. Contrary to previous results, we find that the ratios of carbon-to-oxygen and magnesium-to-silicon are homogeneous to within 10% throughout the solar neighborhood, implying that exoplanets may exhibit much less compositional diversity than previously thought. Finally, we demonstrate that the Sun has a subtle deficiency in refractory material relative to ~95% of solar twins, suggesting a possible signpost for planetary systems like our own. DETAILS: we also use abundance measurements of twelve heavy elements (Sr, Y, Zr, Ba, La, Ce, Pr, Nd, Sm, Eu, Gd, and Dy). These abundances are adopted from Spina et al. (2018), which uses the same combined HARPS spectra and the same strictly differential equivalent width method of abundance determination. The resulting dataset of 30 elemental abundances in 79 Sun-like stars is the most extensive set of extremely precise differential abundances produced to date. CONCLUSIONS: Using our extremely high-precision measurements of 30 elemental abundances across 79 Sun-like stars in the solar neighborhood, we have constrained galactic chemical evolution trends, investigated the star-to-star variations in key planetary building blocks, and shown that the Sun has an unusual abundance trend relative to the majority of its twins. The statistics of exoplanetary systems from the Kepler mission and radial velocity surveys have demonstrated that the architectures of most other planetary systems are dramatically different than our own, with approximately half of all Sun-like stars hosting likely volatilerich planets with super-Earth radii in orbits smaller than that of Mercury (Winn & Fabrycky 2015; Rogers 2015). The coincidence between the rarity of the Sun’s abundance pattern and the solar system architecture offers the intriguing possibility that stellar abundances can be used identify systems harboring planets that are more like the Earth than the typical exoplanet. We look forward to more detailed exploration of the connections between stellar abundances and planetary system properties as the sample of bright, spectroscopy-friendly stars with well-characterized characterized planets vastly expands in the upcoming era of TESS, Gaia, and next generation radial velocity
a. profiles b. data c. Spectrographs. d. spectrums
Q32. arXiv:1802.02636 [astro-ph.SR]:Discovery of a magnetic white dwarf with unusual short-period variability. Aleks Scholz (St Andrews), et al., (Submitted on 7 Feb 2018): We report the discovery of a magnetic white dwarf which shows periodic variability with P=110 min, color-dependent amplitudes and a transient phase shift in the blue compared to the red lightcurve - a previously unknown type of variability for this type of object. We attribute the variations either to a close ultracool (thus far undetected) companion or, more likely, to magnetic spots with unusual temperature structure. DETAILS: We obtained high signal-to-noise lightcurves for SDSS16+14 using Lowell Observatory’s Discovery Channel Telescope (DCT) and the Large Monolithic Imager (LMI), on June 15th and July 4th 2017. Here we observed in the three filters g, r, i quasi-simultaneously, i.e. switching filters every few minutes. The resulting multi-band lightcurves are shown in Figure 1. This dataset confirms the presence of a photometric period with P = 110±3min, averaged over the six lightcurves. The amplitudes in g, r, and i are 0.027, 0.021, 0.021 in the first run and 0.030, 0.021, 0.019 in the second run, respectively. Interestingly, the first set of observations shows a clear offset in phase of ∼ 0.2 between the r/i-band lightcurves and the one in the g-band. This offset was not observed (or is significantly smaller) in the second run. Both times, the g-band lightcurve is deviating from the sinusoidal variations seen in r- and i-band. There are two ways to explain this type of variability. The first option is to postulate the presence of a cool, unresolved companion, with the period being the orbital period. The observed period and amplitude fit into the small group of white plus brown dwarf systems in the literature (Casewell et al. 2018). The variability could be produced by reflected light, thermal re-radiation, accretion, or beaming (Maoz et al. 2015). The phaseshift may be caused by more than one of these mechanisms being involved. To validate this hypothesis, we searched for the IR excess caused by the companion, using deep H- and K-band imaging from Subaru/IRCS, in an observing run on July 1-2 2017. The object is clearly detected as a single point source, and we measure magnitudes of H = 18.1±0.1 and K = 18.3±0.1. Within the errorbars, this is consistent with a 10000K blackbody scaled to the Sloan g-band magnitude of SDSS16+14 and rules out L-type companions with T > 1000K. Radial velocity monitoring is needed to exclude even cooler companions. In absence of an IR excess, the favoured explanation is the presence of magnetic spots and a rotational modulation of the flux. In terms of period, amplitude, temperature and magnetic field strength, SDSS16+14 fits into the sample of magnetic white dwarfs with measured rotation periods by Brinkworth et al. (2013). Simple blackbody spot models,such as used by Scholz et al. (2009), match the color dependence of the amplitudes, with spot temperature around 5000K and a filling factor of 2-3%. If this interpretation is correct, SDSS16+14 is one of the fastest known rotating white dwarfs (Kawaler 2015) and among the spotted white dwarfs with the strongest magnetic field. The phaseshift observed in one of the DCT runs requires an unusual temperature structure in the, (e.g., a hot spot and a cool spot offset in longitude).
a. phases b. spots c. amplitudes d. flux
Q33.arXiv:1802.02822 [astro-ph.HE]: The Crab pulsar: ion-proton plasma and high-frequency radio spectrum: P B Jones (Submitted on 8 Feb 2018): ABSTRACT: Salient features of the remarkable band structure seen in the high-frequency interpulse of the Crab pulsar are summarized. It is argued that its source must lie in a current sheet, probably coincident with the open-closed magnetosphere separatrix, and that the mechanism is a form of one-pass free-electron laser. An outward moving electron component in the current sheet interacts with the longitudinal electric field of an inward directed ion-proton Lamgmuir mode. The band structure is then a natural consequence of the differing charge-to-mass ratios of the ions, which are a return current component of those accelerated, as in almost all pulsars, from the polar cap to the light cylinder. The Crab pulsar has spin Ω and polarcap magnetic flux density B such that Ω·B < 0 in common with most of the observed radio pulsars. The sign of Ω·B is important because it determines the degrees of freedom and nature of the open magnetosphere plasma. The positive sign (negative Goldreich-Julian charge density) allows the emission of electrons only. The magnetosphere above the polar cap is of electrons, governed by Maxwell’s equations with boundary conditions: natural frequencies are limited to the electron cyclotron and plasma frequencies, although pair creation may be possible. These limitations are unlikely to be consistent with the wide range of phenomena, mode-changes and nulls, observed in radio pulsars and it is unsurprising that a physical understanding of them has not been achieved with this sign assumption. The opposite sign leads to the formation of an ion-proton plasma whose properties are functions of the nature of the condensed-matter surface of the star. Investigations of this have shown that, although of greater complexity, it does provide the basis for an understanding of the observed phenomena but unfortunately involves parameters, particularly polar-cap atomic number and whole-surface temperature, that are not well known. CONCLUSIONS: The distribution of ion charges and mass numbers produced by the decay of the giant dipole states formed in electromagnetic showers at the polar cap and by subsequent photo-ionization is not well known. Thus observations on single pulses with bandwidth much increased from the existing 4 GHz would be of the greatest interest. Eilek & Hankins have suggested that, given adequate observing bandwidth, a complete set of emission lines extending from 5 to 28 GHz might be seen in a single pulse, but our model predicts that this should not be so. The band structure in any single pulse would be centred on hνi and the νi simply represent the distribution of Zi/Ai that exists in the return flow and the values of γ and the velocities vp and vi at that
a. moment b. flows c. interests d. instant
Q34.arXiv:1707.05003 [hep-th]:Phys. Rev. D 97, 044002 (2018): Condensate of Massive Graviton and Dark Matter: Katsuki Aoki, Kei-ichi Maeda,(Submitted on 17 Jul 2017 (v1), last revised 8 Feb 2018): ABSTRCT: We study coherently oscillating massive gravitons in the ghost-free bigravity theory. This coherent field can be interpreted as a condensate of the massive gravitons. We first define the effective energy-momentum tensor of the coherent massive gravitons in a curved spacetime. We then study the background dynamics of the universe and the cosmic structure formation including the effects of the coherent massive gravitons. We find that the condensate of the massive graviton behaves as a dark matter component of the universe. From the geometrical point of view the condensate is regarded as a spacetime anisotropy. Hence, in our scenario, dark matter is originated from the tiny deformation of the spacetime. We also discuss a production of the spacetime anisotropy and find that the extragalactic magnetic field of a primordial origin can yield a sufficient amount for dark matter. DETAILS: The existence of gravitational waves was indeed confirmed by the direct detections, and their quantum counterpart is called gravitons. The gravitons are defined by perturbations around a background spacetime. The effective energy-momentum tensor of the high-frequency gravitons in General Relativity (GR) was derived by Isaacson which enables us to treat the gravitons as massless spin-2 particles whose energy and momentum change the background geometry. Due to the nonlinear features of the Einstein equations the effective energymomentum tensor cannot be straightforwardly defined. The gravitons are well-defined when their frequencies (and their momenta) are high enough compared with the curvature scale of the background and then the energymomentum tensor is defined via a non-local operation which projects the nonlinear quantities of the gravitons onto those in low-frequency modes. However, the low energy states of gravitons, i.e., low frequency/momentum modes of gravitons, should be ill-defined in GR. This is not the case when a graviton is massive. The bigravity theory has received much attentions related to the discovery of dark energy and dark matter. If the graviton mass is extremely small such as m ∼10^−33 eV, the present accelerating expansion of the Universe can be explained by the tiny graviton mass. Other range of the mass may explain the origin of dark matter. For instance, dark matter is originated from a matter field in the “dark sector” when m & 10^−27 eV, whereas the massive graviton itself is a candidate of dark matter when 10^−4 eV < m < 10^7 eV . Conclusions: we comment on an interesting remaining question: Is the almost homogeneous configuration of ϕµν the Bose-Einstein condensate of the massive graviton? As is well-known, a coherent massive scalar field, for example axion, is a viable dark matter candidate. This coherent scalar field is interpreted as the Bose-Einstein condensate. Our result would be a generalization of the Bose-Einstein condensate of the massive scalar field to that of the massive tensor
a. field b. quantity c. entity d. sector.
Q35.arXiv:1802.02657 [hep-ph]: Dirac and Majorana Feynman Rules with four-fermions: Michael Paraskevas: (Submitted on 7 Feb 2018): ABSTRACT: A compact method for amplitude calculations in theories with Dirac and Majorana effective operators is discussed. Using the renormalizable formalism of Denner et al., [1,2] for propagators, vertices and fermion (number) flow and introducing new "reading-rules", it is shown that fermions can be treated as scalars in the diagrams. The effect of Fermi-statistics appears only in overall signs and is determined once for whole classes of diagrams. Each vertex in this method corresponds to two or more vertices in the standard treatment of effective theories. As such, the advantages of this approach grow together with the number of four-fermion vertices in a given diagram. The discussion develops around effective field theories based on the Standard Model, up to four-fermions and to any order in perturbation
a. formalism b. theory c. grading d. approach
Q36.arXiv:1802.02661 [gr-qc]: Gravitation in terms of observables: Rodolfo Gambini, Jorge Pullin: (Submitted on 7 Feb 2018): ABSTRACT: In the 1960's, Mandelstam proposed a new approach to gauge theories and gravity based on loops. The program for gauge theories was completed for Yang--Mills theories by Gambini and Trias in the 1980's. Gauge theories could be understood as representations of certain group: the group of loops. The same formalism could not be implemented at that time for the gravitational case. Here we would like to propose an extension to the case of gravity. The resulting theory is described in terms of loops and open paths and can provide the underpinning for a new quantum representation for gravity distinct from the one used in loop quantum gravity or string theory. In it, space-time points are emergent entities that would only have quasi-classical status. The formulation may be given entirely in terms of Dirac observables that form a complete set of gauge invariant functions that completely define the Riemannian geometry of the spacetime. At the quantum level this formulation will lead to a reduced phase space quantization free of any constraints. CONCLUSIONS:In the intrinsic description of gravity a physical point is given by the equivalence class of paths that differ by loops that may be defined by the repeated action of the loop derivative. In the quantum theory, a fluctuation of the geometry in any region of space-time will change that equivalence class, that is, some of the paths that led to that point will fail to arrive to it. This will induce fluctuations in the points that must be considered as emergent objects of an underlying structure of paths. The fluctuations of the space-time points will be more important in a quantum region like near where black holes have their classical singularities. Close to a region with big quantum fluctuations the fields will stop being local, in particular scalar fields associated to nearby points will not commute, irrespective of the separation being space-like or time-like. Note that the non-locality is also in time, which makes the causal structure of events become fuzzy. The question remains of what happens at the horizon of a black hole, since although for large RSchwarzschild/ℓPlanck the effects will be small, the horizon amplifies non-localities. The intrinsic description naturally operates with space-time paths. However, even if one considers spatial paths one could end up in points that are in the future of where one started. This will require special care at the time of quantization, as was already observed by Mandelstam. The whole construction is locally Lorentz invariant but there may be a distortion of the invariance, unrelated to the ones due to granular descriptions of space-time, due to the fluctuation of the points. Further studies of the quantization are needed to understand the non-local effects induced by time-like paths. In a forthcoming paper we will discuss the Poisson algebra of path dependent fields including gravity and its
a. non-locality b. time-like path c. space-time d. quantization.
Q37. arXiv:1801.02392 [hep-th]: Axially-symmetric stationary solutions in a pure SU(3) QCD:
a. profiles b. data c. Spectrographs. d. spectrums
Q32. arXiv:1802.02636 [astro-ph.SR]:Discovery of a magnetic white dwarf with unusual short-period variability. Aleks Scholz (St Andrews), et al., (Submitted on 7 Feb 2018): We report the discovery of a magnetic white dwarf which shows periodic variability with P=110 min, color-dependent amplitudes and a transient phase shift in the blue compared to the red lightcurve - a previously unknown type of variability for this type of object. We attribute the variations either to a close ultracool (thus far undetected) companion or, more likely, to magnetic spots with unusual temperature structure. DETAILS: We obtained high signal-to-noise lightcurves for SDSS16+14 using Lowell Observatory’s Discovery Channel Telescope (DCT) and the Large Monolithic Imager (LMI), on June 15th and July 4th 2017. Here we observed in the three filters g, r, i quasi-simultaneously, i.e. switching filters every few minutes. The resulting multi-band lightcurves are shown in Figure 1. This dataset confirms the presence of a photometric period with P = 110±3min, averaged over the six lightcurves. The amplitudes in g, r, and i are 0.027, 0.021, 0.021 in the first run and 0.030, 0.021, 0.019 in the second run, respectively. Interestingly, the first set of observations shows a clear offset in phase of ∼ 0.2 between the r/i-band lightcurves and the one in the g-band. This offset was not observed (or is significantly smaller) in the second run. Both times, the g-band lightcurve is deviating from the sinusoidal variations seen in r- and i-band. There are two ways to explain this type of variability. The first option is to postulate the presence of a cool, unresolved companion, with the period being the orbital period. The observed period and amplitude fit into the small group of white plus brown dwarf systems in the literature (Casewell et al. 2018). The variability could be produced by reflected light, thermal re-radiation, accretion, or beaming (Maoz et al. 2015). The phaseshift may be caused by more than one of these mechanisms being involved. To validate this hypothesis, we searched for the IR excess caused by the companion, using deep H- and K-band imaging from Subaru/IRCS, in an observing run on July 1-2 2017. The object is clearly detected as a single point source, and we measure magnitudes of H = 18.1±0.1 and K = 18.3±0.1. Within the errorbars, this is consistent with a 10000K blackbody scaled to the Sloan g-band magnitude of SDSS16+14 and rules out L-type companions with T > 1000K. Radial velocity monitoring is needed to exclude even cooler companions. In absence of an IR excess, the favoured explanation is the presence of magnetic spots and a rotational modulation of the flux. In terms of period, amplitude, temperature and magnetic field strength, SDSS16+14 fits into the sample of magnetic white dwarfs with measured rotation periods by Brinkworth et al. (2013). Simple blackbody spot models,such as used by Scholz et al. (2009), match the color dependence of the amplitudes, with spot temperature around 5000K and a filling factor of 2-3%. If this interpretation is correct, SDSS16+14 is one of the fastest known rotating white dwarfs (Kawaler 2015) and among the spotted white dwarfs with the strongest magnetic field. The phaseshift observed in one of the DCT runs requires an unusual temperature structure in the, (e.g., a hot spot and a cool spot offset in longitude).
a. phases b. spots c. amplitudes d. flux
Q33.arXiv:1802.02822 [astro-ph.HE]: The Crab pulsar: ion-proton plasma and high-frequency radio spectrum: P B Jones (Submitted on 8 Feb 2018): ABSTRACT: Salient features of the remarkable band structure seen in the high-frequency interpulse of the Crab pulsar are summarized. It is argued that its source must lie in a current sheet, probably coincident with the open-closed magnetosphere separatrix, and that the mechanism is a form of one-pass free-electron laser. An outward moving electron component in the current sheet interacts with the longitudinal electric field of an inward directed ion-proton Lamgmuir mode. The band structure is then a natural consequence of the differing charge-to-mass ratios of the ions, which are a return current component of those accelerated, as in almost all pulsars, from the polar cap to the light cylinder. The Crab pulsar has spin Ω and polarcap magnetic flux density B such that Ω·B < 0 in common with most of the observed radio pulsars. The sign of Ω·B is important because it determines the degrees of freedom and nature of the open magnetosphere plasma. The positive sign (negative Goldreich-Julian charge density) allows the emission of electrons only. The magnetosphere above the polar cap is of electrons, governed by Maxwell’s equations with boundary conditions: natural frequencies are limited to the electron cyclotron and plasma frequencies, although pair creation may be possible. These limitations are unlikely to be consistent with the wide range of phenomena, mode-changes and nulls, observed in radio pulsars and it is unsurprising that a physical understanding of them has not been achieved with this sign assumption. The opposite sign leads to the formation of an ion-proton plasma whose properties are functions of the nature of the condensed-matter surface of the star. Investigations of this have shown that, although of greater complexity, it does provide the basis for an understanding of the observed phenomena but unfortunately involves parameters, particularly polar-cap atomic number and whole-surface temperature, that are not well known. CONCLUSIONS: The distribution of ion charges and mass numbers produced by the decay of the giant dipole states formed in electromagnetic showers at the polar cap and by subsequent photo-ionization is not well known. Thus observations on single pulses with bandwidth much increased from the existing 4 GHz would be of the greatest interest. Eilek & Hankins have suggested that, given adequate observing bandwidth, a complete set of emission lines extending from 5 to 28 GHz might be seen in a single pulse, but our model predicts that this should not be so. The band structure in any single pulse would be centred on hνi and the νi simply represent the distribution of Zi/Ai that exists in the return flow and the values of γ and the velocities vp and vi at that
a. moment b. flows c. interests d. instant
Q34.arXiv:1707.05003 [hep-th]:Phys. Rev. D 97, 044002 (2018): Condensate of Massive Graviton and Dark Matter: Katsuki Aoki, Kei-ichi Maeda,(Submitted on 17 Jul 2017 (v1), last revised 8 Feb 2018): ABSTRCT: We study coherently oscillating massive gravitons in the ghost-free bigravity theory. This coherent field can be interpreted as a condensate of the massive gravitons. We first define the effective energy-momentum tensor of the coherent massive gravitons in a curved spacetime. We then study the background dynamics of the universe and the cosmic structure formation including the effects of the coherent massive gravitons. We find that the condensate of the massive graviton behaves as a dark matter component of the universe. From the geometrical point of view the condensate is regarded as a spacetime anisotropy. Hence, in our scenario, dark matter is originated from the tiny deformation of the spacetime. We also discuss a production of the spacetime anisotropy and find that the extragalactic magnetic field of a primordial origin can yield a sufficient amount for dark matter. DETAILS: The existence of gravitational waves was indeed confirmed by the direct detections, and their quantum counterpart is called gravitons. The gravitons are defined by perturbations around a background spacetime. The effective energy-momentum tensor of the high-frequency gravitons in General Relativity (GR) was derived by Isaacson which enables us to treat the gravitons as massless spin-2 particles whose energy and momentum change the background geometry. Due to the nonlinear features of the Einstein equations the effective energymomentum tensor cannot be straightforwardly defined. The gravitons are well-defined when their frequencies (and their momenta) are high enough compared with the curvature scale of the background and then the energymomentum tensor is defined via a non-local operation which projects the nonlinear quantities of the gravitons onto those in low-frequency modes. However, the low energy states of gravitons, i.e., low frequency/momentum modes of gravitons, should be ill-defined in GR. This is not the case when a graviton is massive. The bigravity theory has received much attentions related to the discovery of dark energy and dark matter. If the graviton mass is extremely small such as m ∼10^−33 eV, the present accelerating expansion of the Universe can be explained by the tiny graviton mass. Other range of the mass may explain the origin of dark matter. For instance, dark matter is originated from a matter field in the “dark sector” when m & 10^−27 eV, whereas the massive graviton itself is a candidate of dark matter when 10^−4 eV < m < 10^7 eV . Conclusions: we comment on an interesting remaining question: Is the almost homogeneous configuration of ϕµν the Bose-Einstein condensate of the massive graviton? As is well-known, a coherent massive scalar field, for example axion, is a viable dark matter candidate. This coherent scalar field is interpreted as the Bose-Einstein condensate. Our result would be a generalization of the Bose-Einstein condensate of the massive scalar field to that of the massive tensor
a. field b. quantity c. entity d. sector.
Q35.arXiv:1802.02657 [hep-ph]: Dirac and Majorana Feynman Rules with four-fermions: Michael Paraskevas: (Submitted on 7 Feb 2018): ABSTRACT: A compact method for amplitude calculations in theories with Dirac and Majorana effective operators is discussed. Using the renormalizable formalism of Denner et al., [1,2] for propagators, vertices and fermion (number) flow and introducing new "reading-rules", it is shown that fermions can be treated as scalars in the diagrams. The effect of Fermi-statistics appears only in overall signs and is determined once for whole classes of diagrams. Each vertex in this method corresponds to two or more vertices in the standard treatment of effective theories. As such, the advantages of this approach grow together with the number of four-fermion vertices in a given diagram. The discussion develops around effective field theories based on the Standard Model, up to four-fermions and to any order in perturbation
a. formalism b. theory c. grading d. approach
Q36.arXiv:1802.02661 [gr-qc]: Gravitation in terms of observables: Rodolfo Gambini, Jorge Pullin: (Submitted on 7 Feb 2018): ABSTRACT: In the 1960's, Mandelstam proposed a new approach to gauge theories and gravity based on loops. The program for gauge theories was completed for Yang--Mills theories by Gambini and Trias in the 1980's. Gauge theories could be understood as representations of certain group: the group of loops. The same formalism could not be implemented at that time for the gravitational case. Here we would like to propose an extension to the case of gravity. The resulting theory is described in terms of loops and open paths and can provide the underpinning for a new quantum representation for gravity distinct from the one used in loop quantum gravity or string theory. In it, space-time points are emergent entities that would only have quasi-classical status. The formulation may be given entirely in terms of Dirac observables that form a complete set of gauge invariant functions that completely define the Riemannian geometry of the spacetime. At the quantum level this formulation will lead to a reduced phase space quantization free of any constraints. CONCLUSIONS:In the intrinsic description of gravity a physical point is given by the equivalence class of paths that differ by loops that may be defined by the repeated action of the loop derivative. In the quantum theory, a fluctuation of the geometry in any region of space-time will change that equivalence class, that is, some of the paths that led to that point will fail to arrive to it. This will induce fluctuations in the points that must be considered as emergent objects of an underlying structure of paths. The fluctuations of the space-time points will be more important in a quantum region like near where black holes have their classical singularities. Close to a region with big quantum fluctuations the fields will stop being local, in particular scalar fields associated to nearby points will not commute, irrespective of the separation being space-like or time-like. Note that the non-locality is also in time, which makes the causal structure of events become fuzzy. The question remains of what happens at the horizon of a black hole, since although for large RSchwarzschild/ℓPlanck the effects will be small, the horizon amplifies non-localities. The intrinsic description naturally operates with space-time paths. However, even if one considers spatial paths one could end up in points that are in the future of where one started. This will require special care at the time of quantization, as was already observed by Mandelstam. The whole construction is locally Lorentz invariant but there may be a distortion of the invariance, unrelated to the ones due to granular descriptions of space-time, due to the fluctuation of the points. Further studies of the quantization are needed to understand the non-local effects induced by time-like paths. In a forthcoming paper we will discuss the Poisson algebra of path dependent fields including gravity and its
a. non-locality b. time-like path c. space-time d. quantization.
Q37. arXiv:1801.02392 [hep-th]: Axially-symmetric stationary solutions in a pure SU(3) QCD:
D. G. Pak, P.M. Zhang: ABSTRACT: We propose an ansatz for a class of regular axially-symmetric solutions in SU(3) QCD. After averaging over time period the solution can be treated as a non-topological monopole-antimonopole pair. We demonstrate that QCD Lagrangian on the space of such solutions is explicitly Weyl symmetric and reduces to a generalized φ4 model with four independent fields. All solutions possess quantum stability under vacuum gluon fluctuations. CONCLUSIONS: We propose an ansatz for a class of regular axially-symmetric solutions in SU(3) QCD. After averaging over time period the solution can be treated as a non-topological monopole-antimonopole pair. We demonstrate that QCD Lagrangian on the space of such solutions is explicitly Weyl symmetric and reduces to a generalized φ4 model with four independent fields. All solutions possess quantum stability under vacuum gluon fluctuations. we propose a new class of regular stationary solutions with a finite energy density in a pure SU(3) QCD. Recently it has been proved that the stationary spherically symmetric monopole and monopole-antimonopole pair solutions are stable against small quantum gluon fluctuations. We expect that the whole class of considered regular stationary solutions possesses quantum stability as well. We have considered a class of regular Abelian stationary solutions and have proved thier stability under small quantum gluon fluctuations. Since the Abelian solutions possess the classical stability as well, they provide the most preferable field configurations for the QCD vacuum in quasiclassical approximation. We suppose that the regular stationary solutions play an important role in microscopic description of the QCD vacuum
a. approximation b. field c. formation d. fluctuation
a. approximation b. field c. formation d. fluctuation
Q38. arXiv:1802.02898 [nucl-th]: Spectroscopic Criteria for Identification of Nuclear Tetrahedral and Octahedral Symmetries: Illustration on a Rare Earth Nucleus. J. Dudek, et al. (Submitted on 8 Feb 2018): ABSTRACT: We formulate criteria of identification of the nuclear tetrahedral and octahedral symmetries and illustrate for the first time their possible realization in a Rare Earth nucleus 152Sm. We use realistic nuclear mean-field theory calculations with the phenomenological macroscopic-microscopic method, the Gogny-Hartree-Fock-Bogoliubov approach and the general point-group theory considerations to guide the experimental identification method illustrated on published experimental data. Following group-theory the examined symmetries imply existence of exotic rotational bands on whose properties the spectroscopic identification criteria are based. These bands may contain simultaneously states of even and odd spins, of both parities and parity doublets at well defined spins. In the exact-symmetry limit those bands involve no E2-transitions. We show that coexistence of tetrahedral and octahedral deformations is essential when calculating the corresponding energy minima and surrounding barriers and, as discussed in the article, has a characteristic impact on the rotational bands. The symmetries in question imply the existence of long-lived shape-isomers and, possibly, new waiting point nuclei (impacting the nucleosynthesis processes in astrophysics) and an existence of 16-fold degenerate particle-hole excitations. Specifically designed experiments which aim at strengthening the identification arguments are briefly discussed. DETAILS: The chains of tetrahedral magic numbers Z/N = 16,20,32,40,56,64,70,90 and N = 112,136,142 – which correspond to increased nuclear stability at the tetrahedral geometry have been proposed. We demonstrate on the example of 152Sm, that using simultaneously what we call tetrahedral and octahedral deformations is essential when studying the implied exotic-symmetry minima. In summary: We showed that experimental results for 5 positive parity levels interpreted as A1g octahedralsymmetry sequence fit a single parabola in agreement with the group-theory interpretation, within over a 1000keV interval, with the r.m.s. deviation of 1.6keV. At the same time those for the experimental 6 negative parity levels interpreted as A2u octahedral-symmetry sequence fit another single parabola, within the interval of about 1200keV, with the r.m.s. deviation of
a. 7.5keV b. 10keV c. 5.5keV d. 6.5keV.
Q39. arXiv:1802.02807 [quant-ph]: Classical evolution of quantum systems: J. Sperling, I. A. Walmsley: (Submitted on 8 Feb 2018): ABSTRACT: For studying quantum phenomena in time, it is vital to have a profound understanding of the classical dynamics. For this reason, we derive equations of motions describing the classical propagation of a quantum system. A comparison of this classical evolution with the actual temporal behavior enables us to identify quantum effects of the evolution itself and distinguish them from static quantum features and quantum phenomena for a single point in time. As applications of our universal technique, we analyze nonlinear processes in quantum optics, semi-classical models, and the multipartite entanglement dynamics of macroscopic ensembles. DETAILS: Moreover, quantum features are essential for the development of technologies. New applications exploit the resources provided by quantum systems to perform tasks not achievable by classical means, e.g., quantum teleportation and dense coding. Other protocols rely on quantum properties to improve the communication security, such as quantum key distribution. Thus, the classical limitations of the underlying processes have to be known in order to assess the benefit of utilizing quantum phenomena. In summary, we devised a technique to describe the classical evolution of quantum systems. This allows us to compare the quantum dynamics with the classically predicted behavior for identifying nonclassical properties in time. Based on Hamilton’sequations,wederivedtheequationsofmotionsfor the parameters which characterize the set of classical states understudy. Consequently, the solutions are confined to those classical states for all times. Whenever the actual quantum dynamics is incompatible with the classical behavior, the quantum nature of the evolution is verified. To demonstrate the broad applicability, different applications were studied. Firstly, we analyzed the notion of nonclassicality in terms of coherent states to study processes in nonlinear quantum optics. We demonstrated that our classical equations of motion and the quantum-physical Heisenberg equations formally share the mestructure. However, these solutions ehibit distinguishing features. This was shown by analyzing the propagation in a Kerr medium. For the classical and quantum dynamics, we compared states which are initially classical or nonclassical to separate initial nonclassicalities from quantum features due to the quantum evolution. Secondly, we considered semi-classical models in which one part is a quantum system and the other one is classical. This is important, for instance, for studying quantum measurements processes with a macroscopic device in a consistent manner. Our method renders it possible to perform such a task as demonstrated for the example of a classical light field coupled to a two-level quantum atom. We could show that, despite of interactions with quantum subsystem, the field remains classical for all times, which cannot be achieved when applying standard approaches. Finally, we studied the entanglement dynamics of a system consisting of a macroscopic number of quantum-mechanical oscillators. In this scenario, the classical states are identified with separable ones. The classical dynamics resulting from our method is described in terms of Schr¨odinger-type equations for each subsystem separately. This is consistent with our recent approach and underlines the general potential of our method introduced here. As we have shown for different forms of separability (or, conversely, partial entanglement), the entanglement-generating evolution can be clearly distinguished from the classical one, even for initially fully separable mixed states. In conclusion, we developed a general and easily accessible approach to certify quantum properties in time. Our technique is not restricted to a specific type of classical states and applies to arbitrary time scales and interaction regimes. Thus, we believe that our method provides a powerful tool and versatile starting point for studies of temporal quantum
a. uncertainities b. oscillators c. phenomena d. states
Q40.arXiv:1802.01000 [physics.comp-ph]: A Software Package for Rigorously Calculating Optical Plasma Spectra and Automatically Rtrieving Plasma Properties:Xiaofeng Tan: (Submitted on 3 Feb 2018): ABSTRACT: In this article, a software package code named OPSIAL (Optical Plasma Spectral Calculation And Parameters Retrieval) for rigorously calculating optical plasma spectra and for automatically retrieving plasma parameters is presented. OPSIAL calculates the absolute spectral radiance caused by the bound-bound transitions of elemental species in the plasma by rigorously solving the equation of radiative transfer using an ultrafast line-by-line algorithm. OPSIAL supports both the local-thermodynamic-equilibrium (LTE) or partial LTE conditions and takes account of line broadenings due to the Doppler effect and collisions with electrons and other pseudo colliders in the plasma. An algorithm for fully automatically identifying elemental species and retrieving plasma parameters based on observed plasma emission spectra has been implemented into OPSIAL. The structure and theoretical framework of OPSIAL, together with a case study of using OPSIAL to analyze laser-induced breakdown spectral data of the ChemCam instrument onboard the Mars rover Curiosity, are presented. Conclusions In this paper we present the structure, theoretical framework, and workflow of the OPSIAL software package for fast and rigorous calculation of plasma optical emission spectra and for fully automatic plasma properties retrieval from the observed spectra. The fast calculation speed of OPSIAL coupled with its capabilities of treating the line broadening effects, multiple LOS segments, and NLTE temperatures makes OPSIAL a powerful and flexible software tool for quickly calculating and modeling plasma optical emission spectra. The utility of OPSIAL in processing plasma optical emission data with large number of spectral features is demonstrated in the test analysis of a ChemCam LIBS spectrum taken at the Gale crater on Mars. The analysis also shows that absolute spectral radiance calculated with OPSIAL can be of great value in fitting photo-metrically calibrated spectral data. The automatic plasma property retrieval algorithm in OPSIAL is still a work in progress. The PL of OPSIAL in the current version is currently trained with 9570 training records generated in the Monte Carlo simulations. It is demonstrated in the test analysis of the ChemCam spectrum that even with this limited number of training data OPSIAL produces encouraging results in identifying species in the test spectrum. A large training dataset together with specially designed simulations with the knowledge of the approximate compositions (e.g., what elements are likely presented) of the plasma for specific applications are expected to produce more favorable results for the species identification. The test does show potential difficulty for OPSIAL to identify species with few spectral features (e.g., Al in the test case) surrounded by large number of interference
a. factors b. features c. scenario d. analysis.
Q41. arXiv:1801.10153 [physics.space-ph]: Detection of short term response of the low ionosphere on gamma ray bursts. Aleksandra Nina et al.,(Submitted on 30 Jan 2018): ABSTRACT: In this paper, we study the possibility of detection of short term terrestrial lower ionospheric response to gamma ray bursts (GRBs) using a statistical analysis of perturbations of six very low or low frequency (VLF/LF) radio signals emitted by transmitters located worldwide and recorded by VLF/LF receiver located in Belgrade (Serbia). We consider a sample of 54 short lasting GRBs (shorter than 1 min) detected by the SWIFT satellite during the period 2009-2012. We find that a statistically significant perturbations can be present in the low ionosphere, and reactions on GRBs may be observed immediately after the beginning of the GRB event or with a time delay of 60 s - 90 s. DETAILS: Gamma-Ray Bursts (GRBs) are known as the most energetic phenomena in the Universe where a huge amount of energy is released and their investigation is of a great astrophysical importance. The aim of this paper is to present possible short duration ionospheric perturbations caused by GRB events. We used VLF (3 kHz - 30 kHz) and LF (30 kHz - 300 kHz) radio signals to detect ionosphere disturbances in a short period around GRB events for 54 GRBs observed by SWIFT during 2009 - 2012. we can point out the most important conclusion of this study: it confirms detectability of a short term reaction of the low ionosphere to GRBs which does not cause intense long term reactions in general. The important perturbations of the low ionospheric plasma occur at different times in relation to the beginning of GRB events which indicates a possibility of detection of ionization by the primary GRB radiation as well as by some of its secondary effects. The presented study indicates the possibility of intensive ionospheric perturbations during the
a. GRB event b. secondary effects c. night d. whole day
Q42. arXiv:1802.03591 [nlin.SI]:(Submitted on 10 Feb 2018): New Reductions of a Matrix Generalized Heisenberg Ferromagnet Equation: T. I. Valchev, A. B. Yanovski, E-mails: tiv@math.bas.bg, Alexandar.Ianovsky@uct.ac.za: Abstract: We present in this report 1 + 1 dimensional nonlinear partial differential equation integrable through inverse scattering transform. The integrable system under consideration is a pseudo-Hermitian reduction of a matrix generalization of classical 1 + 1 dimensional Heisenberg ferromagnet equation. We derive recursion operators and describe the integrable hierarchy related to that matrix equation.The Heisenberg ferromagnet equation (HF) St = S×Sxx, S2 = 1 is one of classical equations integrable through inverse scattering transform. Above, S = (S1,S2,S3) is the vector of a one-dimensional ferromagnet and subscripts mean partial derivatives with respect to space variable x and time t. HF can be written as the compatibility condition [L(λ),A(λ)] = 0 of the Lax operators: L(λ) = i∂x −λS, A(λ) = i∂t + iλ 2 [S,Sx] + 2λ2S where λ ∈ C is spectral parameter, i = √−1 and S = [ S3; S1 −iS2; S1 + iS2; −S3]. Where S isa. 7.5keV b. 10keV c. 5.5keV d. 6.5keV.
Q39. arXiv:1802.02807 [quant-ph]: Classical evolution of quantum systems: J. Sperling, I. A. Walmsley: (Submitted on 8 Feb 2018): ABSTRACT: For studying quantum phenomena in time, it is vital to have a profound understanding of the classical dynamics. For this reason, we derive equations of motions describing the classical propagation of a quantum system. A comparison of this classical evolution with the actual temporal behavior enables us to identify quantum effects of the evolution itself and distinguish them from static quantum features and quantum phenomena for a single point in time. As applications of our universal technique, we analyze nonlinear processes in quantum optics, semi-classical models, and the multipartite entanglement dynamics of macroscopic ensembles. DETAILS: Moreover, quantum features are essential for the development of technologies. New applications exploit the resources provided by quantum systems to perform tasks not achievable by classical means, e.g., quantum teleportation and dense coding. Other protocols rely on quantum properties to improve the communication security, such as quantum key distribution. Thus, the classical limitations of the underlying processes have to be known in order to assess the benefit of utilizing quantum phenomena. In summary, we devised a technique to describe the classical evolution of quantum systems. This allows us to compare the quantum dynamics with the classically predicted behavior for identifying nonclassical properties in time. Based on Hamilton’sequations,wederivedtheequationsofmotionsfor the parameters which characterize the set of classical states understudy. Consequently, the solutions are confined to those classical states for all times. Whenever the actual quantum dynamics is incompatible with the classical behavior, the quantum nature of the evolution is verified. To demonstrate the broad applicability, different applications were studied. Firstly, we analyzed the notion of nonclassicality in terms of coherent states to study processes in nonlinear quantum optics. We demonstrated that our classical equations of motion and the quantum-physical Heisenberg equations formally share the mestructure. However, these solutions ehibit distinguishing features. This was shown by analyzing the propagation in a Kerr medium. For the classical and quantum dynamics, we compared states which are initially classical or nonclassical to separate initial nonclassicalities from quantum features due to the quantum evolution. Secondly, we considered semi-classical models in which one part is a quantum system and the other one is classical. This is important, for instance, for studying quantum measurements processes with a macroscopic device in a consistent manner. Our method renders it possible to perform such a task as demonstrated for the example of a classical light field coupled to a two-level quantum atom. We could show that, despite of interactions with quantum subsystem, the field remains classical for all times, which cannot be achieved when applying standard approaches. Finally, we studied the entanglement dynamics of a system consisting of a macroscopic number of quantum-mechanical oscillators. In this scenario, the classical states are identified with separable ones. The classical dynamics resulting from our method is described in terms of Schr¨odinger-type equations for each subsystem separately. This is consistent with our recent approach and underlines the general potential of our method introduced here. As we have shown for different forms of separability (or, conversely, partial entanglement), the entanglement-generating evolution can be clearly distinguished from the classical one, even for initially fully separable mixed states. In conclusion, we developed a general and easily accessible approach to certify quantum properties in time. Our technique is not restricted to a specific type of classical states and applies to arbitrary time scales and interaction regimes. Thus, we believe that our method provides a powerful tool and versatile starting point for studies of temporal quantum
a. uncertainities b. oscillators c. phenomena d. states
Q40.arXiv:1802.01000 [physics.comp-ph]: A Software Package for Rigorously Calculating Optical Plasma Spectra and Automatically Rtrieving Plasma Properties:Xiaofeng Tan: (Submitted on 3 Feb 2018): ABSTRACT: In this article, a software package code named OPSIAL (Optical Plasma Spectral Calculation And Parameters Retrieval) for rigorously calculating optical plasma spectra and for automatically retrieving plasma parameters is presented. OPSIAL calculates the absolute spectral radiance caused by the bound-bound transitions of elemental species in the plasma by rigorously solving the equation of radiative transfer using an ultrafast line-by-line algorithm. OPSIAL supports both the local-thermodynamic-equilibrium (LTE) or partial LTE conditions and takes account of line broadenings due to the Doppler effect and collisions with electrons and other pseudo colliders in the plasma. An algorithm for fully automatically identifying elemental species and retrieving plasma parameters based on observed plasma emission spectra has been implemented into OPSIAL. The structure and theoretical framework of OPSIAL, together with a case study of using OPSIAL to analyze laser-induced breakdown spectral data of the ChemCam instrument onboard the Mars rover Curiosity, are presented. Conclusions In this paper we present the structure, theoretical framework, and workflow of the OPSIAL software package for fast and rigorous calculation of plasma optical emission spectra and for fully automatic plasma properties retrieval from the observed spectra. The fast calculation speed of OPSIAL coupled with its capabilities of treating the line broadening effects, multiple LOS segments, and NLTE temperatures makes OPSIAL a powerful and flexible software tool for quickly calculating and modeling plasma optical emission spectra. The utility of OPSIAL in processing plasma optical emission data with large number of spectral features is demonstrated in the test analysis of a ChemCam LIBS spectrum taken at the Gale crater on Mars. The analysis also shows that absolute spectral radiance calculated with OPSIAL can be of great value in fitting photo-metrically calibrated spectral data. The automatic plasma property retrieval algorithm in OPSIAL is still a work in progress. The PL of OPSIAL in the current version is currently trained with 9570 training records generated in the Monte Carlo simulations. It is demonstrated in the test analysis of the ChemCam spectrum that even with this limited number of training data OPSIAL produces encouraging results in identifying species in the test spectrum. A large training dataset together with specially designed simulations with the knowledge of the approximate compositions (e.g., what elements are likely presented) of the plasma for specific applications are expected to produce more favorable results for the species identification. The test does show potential difficulty for OPSIAL to identify species with few spectral features (e.g., Al in the test case) surrounded by large number of interference
a. factors b. features c. scenario d. analysis.
Q41. arXiv:1801.10153 [physics.space-ph]: Detection of short term response of the low ionosphere on gamma ray bursts. Aleksandra Nina et al.,(Submitted on 30 Jan 2018): ABSTRACT: In this paper, we study the possibility of detection of short term terrestrial lower ionospheric response to gamma ray bursts (GRBs) using a statistical analysis of perturbations of six very low or low frequency (VLF/LF) radio signals emitted by transmitters located worldwide and recorded by VLF/LF receiver located in Belgrade (Serbia). We consider a sample of 54 short lasting GRBs (shorter than 1 min) detected by the SWIFT satellite during the period 2009-2012. We find that a statistically significant perturbations can be present in the low ionosphere, and reactions on GRBs may be observed immediately after the beginning of the GRB event or with a time delay of 60 s - 90 s. DETAILS: Gamma-Ray Bursts (GRBs) are known as the most energetic phenomena in the Universe where a huge amount of energy is released and their investigation is of a great astrophysical importance. The aim of this paper is to present possible short duration ionospheric perturbations caused by GRB events. We used VLF (3 kHz - 30 kHz) and LF (30 kHz - 300 kHz) radio signals to detect ionosphere disturbances in a short period around GRB events for 54 GRBs observed by SWIFT during 2009 - 2012. we can point out the most important conclusion of this study: it confirms detectability of a short term reaction of the low ionosphere to GRBs which does not cause intense long term reactions in general. The important perturbations of the low ionospheric plasma occur at different times in relation to the beginning of GRB events which indicates a possibility of detection of ionization by the primary GRB radiation as well as by some of its secondary effects. The presented study indicates the possibility of intensive ionospheric perturbations during the
a. GRB event b. secondary effects c. night d. whole day
a. parameter b. Spin Vector c. Ferromagnet d. subscript
Q43.arXiv:1802.02930 [q-bio.NC]: Evolution of the Science Fiction Writer's Capacity to Imagine the Future: Liane Gabora:(Submitted on 7 Feb 2018): ABSTRACT: Drawing upon a body of research on the evolution of creativity, this paper proposes a theory of how, when, and why the forward-thinking story-telling abilities of humans evolved, culminating in the visionary abilities of science fiction writers. The ability to recursively chain thoughts together evolved approximately two million years ago. Language abilities, and the ability to shift between different modes of thought, evolved approximately 100,000 years ago. Science fiction dates to at least the second Century AD. It is suggested that well before this time, but after 100,000 years ago, and concurrent with the evolution of a division of labour between creators and imitators there arose a division of labour between past, present, and future thinkers. Agent-based model research suggests there are social benefits to the evolution of individual differences in creativity such that there is a balance between novelty-generating creators and continuity-perpetuating imitators. A balance between individuals focused on the past, present, and future would be expected to yield similar adaptive benefits. FEATURES: the earliest forms of storytelling are thought to be oral, in conjunction with gestures and expressions (Banks-Wallace 2002). It was possible to think about an idea in relation to other closely related ideas and thereby forge clusters of mutually consistent ideas, which allowed for a narrow kind of creativity, limited to minor adaptations of existing ideas. However, the mind was not integrated, nor truly creative, until it could forge connections between seemingly disparate ideas as in the formation of analogies. The ancient Indian thought contributed a lot to human creativity as evident in Jataka Stories, Panch Tantra episodes, Kalidas's Sanskrit revelations, Home embedded children stories, King and Queen episodes, Arya Bhattaas Cosmic statements etc. Futurists, inventors, and writers of science fiction, are more likely to focus on, and think most clearly about, the future. It is not that they cannot or do not think about the past or present but, that they tend to view the past and present as seeds for speculation and prediction about what has yet to pass. Thus, it is proposed that the evolution of individual differences in the extent to which we focus along the spectrum from past to present to future paved the way for the fantastical stories of future events and far-off worlds that we now enjoy. The ‘divide and conquer’ strategy is well-known to Mother Nature, and it has previously been suggested that its effectiveness can account for individual differences in human creativity. Skillful use of it by the Foreign rulers in India has not destroyed the native and sole power of Indian Thought and revealed the Hindu diversity in Science episodes projection with objective
a. projection b. thoughts c.reality d. confirmation
Q44.arXiv:1802.03451 [stat.ML]: Estimating the Spectral Density of Large Implicit Matrices: Ryan P. Adams et al. (Submitted on 9 Feb 2018): ABSTRACT: Many important problems are characterized by the eigenvalues of a large matrix. For example, the difficulty of many optimization problems, such as those arising from the fitting of large models in statistics and machine learning, can be investigated via the spectrum of the Hessian of the empirical loss function. Network data can be understood via the eigenstructure of a graph Laplacian matrix using spectral graph theory. Quantum simulations and other many-body problems are often characterized via the eigenvalues of the solution space, as are various dynamic systems. However, naive eigenvalue estimation is computationally expensive even when the matrix can be represented; in many of these situations the matrix is so large as to only be available implicitly via products with vectors. Even worse, one may only have noisy estimates of such matrix vector products. In this work, we combine several different techniques for randomized estimation and show that it is possible to construct unbiased estimators to answer a broad class of questions about the spectra of such implicit matrices, even in the presence of noise. We validate these methods on large-scale problems in which graph theory and random matrix theory provide ground truth. DETAILS:The behaviors of scientific phenomena and complex engineered systems are often characterized via matrices. The entries of these matrices may reflect interactions between variables, edges between vertices in a graph, or the local geometry of a complicated surface. When the systems under consideration become large, these matrices also become large and it rapidly becomes uninformativy and potentially infeasible, to investigate the individual entries. Instead, we frame our questions about these matrices in terms of aggregate properties that are insensitive to irrelevant details. Discussion: In this work we have described a framework for estimation of spectral densities of large matrices. Our primary objective has been to construct a tool for the empirical investigation of matrices that can only be probed in implicit and noisy ways. Our overall approach has been to combine ideas that have been proposed across several different fields into an estimation framework that provides unbiased estimates with controlled variance, even when the matrices become large. We use this framework to then construct smoothed estimates of the overall density. This smoothing necessarily introduces bias, but it allows us to visualize spectra whose atomic nature would otherwise make them difficult to
a. interrogate b. evaluate c. discuss d. project
Q45. arXiv:1802.03785 [eess.SP]: Generalized Uncertainty Principles for the Offset Linear Canonical Transform: Haiye Huo: (Submitted on 11 Feb 2018): ABSTRACT:The offset linear canonical transform (OLCT) provides a more general framework for a number of well known linear integral transforms in signal processing and optics, such as Fourier transform, fractional Fourier transform, linear canonical transform. In this paper, to characterize simultaneous localization of a signal and its OLCT, we generalize some different uncertainty principles (UPs), including Nazarov's UP, Hardy's UP, Beurling's UP, logarithmic UP and entropic UP, which have already been well studied in the Fourier transform domain over the last few decades, to the OLCT domain in a broader sense. DETAILS: Uncertainty principle (UP) plays an important role in quantum mechanics [7] and signal processing [2]. In quantum mechanics, UP was first proposed by the German physicist W. Heisenberg in 1927 [7]. It indicates that the position and momentum of the particles cannot have finite values at the same time, i.e., the more precisely the position is determined, the less precisely its momentum can be known. From the perspective of signal processing, UP can be described as follows: “One cannot sharply localize a nonzero function and its Fourier transform simultaneously”. By using different notations of essential support, there are many different kinds of UPs associated with the transform, like Heisenberg’s UP [1927)] Nazarov’s UP [(1993), Hardy’s UP (1933), Beurling’s UP (2007), logarithmic UP (1995), entropic UP (1957), and so on. UPs associated with transforms
a. of momentum b. transverse c. longitudinal d. Fourier
Q46.arXiv:1802.03393 [cs.CY]: A Study of WhatsApp Usage Patterns and Prediction Models without Message Content. Avi Rosenfeld et al. (Submitted on 9 Feb 2018):ABSTRACT: Internet social networks have become a ubiquitous application allowing people to easily share text, pictures, and audio and video files. Popular networks include WhatsApp, Facebook, Reddit and LinkedIn. We present an extensive study of the usage of the WhatsApp social network, an Internet messaging application that is quickly replacing SMS messaging. In order to better understand people's use of the network, we provide an analysis of over 6 million messages from over 100 users, with the objective of building demographic prediction models using activity data. We performed extensive statistical and numerical analysis of the data and found significant differences in WhatsApp usage across people of different genders and ages. We also inputted the data into the Weka data mining package and studied models created from decision tree and Bayesian network algorithms. We found that different genders and age demographics had significantly different usage habits in almost all message and group attributes. We also noted differences in users' group behavior and created prediction models, including the likelihood a given group would have relatively more file attachments, if a group would contain a larger number of participants, a higher frequency of activity, quicker response times and shorter messages. We were successful in quantifying and predicting a user's gender and age demographic. Similarly, we were able to predict different types of group usage. All models were built without analyzing message content. We present a detailed discussion about the specific attributes that were contained in all predictive models and suggest possible applications based on these results. CONCLUSIONS: we found that many message and group characteristics significantly differed across users of different demographics, such as gender and age, and present these results through performing extensive statistical analysis. Additionally, we believe that one key novelty of this work is that we use data analytics to predict users’ gender, age and group activity. As our work is data driven, we base our findings on the algorithms’ output, and did not attempt to verify any specific thesis as had been previously done. This is one key advantage to using data analytics, and this difference is especially clear from the decision ......... results presented in this paper.
a. uphill b. tree c. branch d. futuristic
Q47.arXiv:1802.03712 [cs.CL]: Syntax and Semantics of Italian Poetry in the First Half of the 20th Century. Rodolfo Delmonte (Submitted on 11 Feb 2018): ABSTRACT: In this paper we study, analyse and comment rhetorical figures present in some of most interesting poetry of the first half of the twentieth century. These figures are at first traced back to some famous poet of the past and then compared to classical Latin prose. Linguistic theory is then called in to show how they can be represented in syntactic structures and classified as noncanonical structures, by positioning discontinuous or displaced linguistic elements in Spec XP projections at various levels of constituency. Then we introduce LFG (Lexical Functional Grammar) as the theory that allows us to connect syntactic noncanonical structures with informational structure and psycholinguistic theories for complexity evaluation. We end up with two computational linguistics experiments and then evaluate the results. The first one uses best online parsers of Italian to parse poetic structures; the second one uses Getarun, the system created at Ca Foscari Computational Linguistics Laboratory. As will be shown, the first approach is unable to cope with these structures due to the use of only statistical probabilistic information. On the contrary, the second one, being a symbolic rule based system, is by far superior and allows also to complete both semantic an pragmatic
a. analysis b. results c. consistency d. orientation
Q48. arXiv:1802.03469 [nucl-th]: Cosmological Lithium Problems, C.A. Bertulani etal.,(Submitted on 9 Feb 2018): ABSTRACT: We briefly describe the cosmological lithium problems followed by a summary of our recent theoretical work on the magnitude of the effects of electron screening, the possible existence of dark matter parallel universes and the use of non-extensive (Tsallis) statistics during big bang nucleosynthesis. Solutions within nuclear physics are also discussed and recent measurements of cross-sections based on indirect experimental techniques are summarized. DARK MATTER: Most of the matter in the universe consists of an obscure kind of Dark Matter (DM) which interacts very weakly with the visible matter. In fact, we only know that it interacts gravitationally and large scale experimental searches are underway to identify if DM interacts with visible matter by other means [31–33]. The existence of DM is based on astronomical observations of galaxy clusters dynamics and on the anisotropies of the Cosmic Microwave Background (CMB). Perhaps Weakly Interacting Massive Particles (WIMPs),supersymmetric particles, sterile neutrinos,or any other hitherto undiscovered particles are responsible for its composition. It has also been hypothesized that DM is a mirror sector of particles such as dark photons, dark electrons, etc., which interact in nearly the same way as Standard Model (SM) particles, but only within their own sector. They interact very weakly across sectors, i.e. between the DM sector and the visible sector. Besides, the particle copies in the dark sector do not need to have the same masses and couplings as in the visible sector, opening a huge number of possible scenarios for DM. The work published was cited as a research highlight by the American Astronomical Society. It attests the relevance of the lithium puzzle and the anxiety that its solution entails for the astronomical community. The puzzle has been around the literature for a few decades already. The exercise played shows that a solution might be the outcome of a fine tuning of the physics during the
a. SM b. DM c. BBN d. DSM
Q49. arXiv:1802.02864 [hep-ph]: Gauge Invariant Noether's Theorem and The Proton Spin Crisis: Gouranga C Nayak: (Submitted on 8 Feb 2018): ABSTRACT: Due to proton spin crisis it is necessary to understand the gauge invariant definition of the spin and orbital angular momentum of the quark and gluon from first principle. In this paper we derive the gauge invariant Noether's theorem by using combined Lorentz transformation plus local gauge transformation. We find that the notion of the gauge invariant definition of the spin (or orbital) angular momentum of the electromagnetic field does not exist in Dirac-Maxwell theory although the notion of the gauge invariant definition of the spin (or orbital) angular momentum of the electron exists. We find that the gauge invariant definition of the spin angular momentum of the electromagnetic field in the literature is not correct because of the non-vanishing surface term in Dirac-Maxwell theory although the corresponding surface term vanishes for linear momentum. We also show that the Belinfante-Rosenfeld tensor is not required to obtain symmetric and gauge invariant energy-momentum tensor of the electron and the electromagnetic field in Dirac-Maxwell theory. DETAILS: The spin of the proton at rest is 1/2. When the proton is in motion, like that at high energy colliders, its helicity (which is the projection of the proton spin along its direction of motion) is conserved with the quantized value ±1/2. In the naive parton model it was predicted that the proton spin is carried by the quarks (plus antiquarks) inside the proton. However, the famous European muon collaboration (EMC) experiment at CERN revealed that the total contribution to the proton spin from the quarks (plus antiquarks) is almost zero. This is known as the ”proton spin crisis” which is one of the most important unsolved problem in particle physics. CONCLUSIONS:Due to proton spin crisis it is necessary to understand the gauge invariant definition of the spin and orbital angular momentum of the quark and gluon from first principle. In this paper we have derived the gauge invariant Noether’s theorem by using combined Lorentz transformation plus local gauge transformation. We have found that the notion of the gauge invariant definition of the spin (or orbital) angular momentum of the electromagnetic field does not exist in Dirac-Maxwell theory although the notion of the gauge invariant definition of the spin (or orbital) angular momentum of the electron exists. We have found that the gauge invariant definition of the spin angular momentum of the electromagnetic field in the literature, is not correct because of the non-vanishing surface term, in Dirac-Maxwell theory although the corresponding surface term vanishes for linear momentum. We have also shown that the Belinfante-Rosenfeld tensor is not required to obtain symmetric and gauge invariant energy-momentum tensor of the electron and the electromagnetic field in Dirac-Maxwell theory. Hence we conclude that although the high energy collider experiments have measured the spin dependent gluon distribution function inside proton but we do not have a gauge invariant definition of the spin dependent gluon distribution function in QCD consistent with the gauge invariant theorem by,
a. Maxwell b. Noether's c. Gouarang Naik d. Dirac
Q50. arXiv:1803.01452 [astro-ph.EP]: The when and where of water in the history of the universe: Karla de Souza Torres, Othon Cabo Winter, (Submitted on 5 Mar 2018): ABSTRACT:It is undeniable that life as we know it depends on liquid water. It is difficult to imagine any biochemical machinery that does not require water. On Earth, life adapts to the most diverse environments and, once established, it is very resilient. Considering that water is a common compound in the Universe, it seems possible (maybe even likely) that one day we will find life elsewhere in the universe. In this study, we review the main aspects of water as an essential compound for life: when it appeared since the Big Bang, and where it spread throughout the diverse cosmic sites. Then, we describe the strong relation between water and life, as we know it. DETAILS:Two thirds of the Earth’s surface is covered by water, however fresh water is most valuable as a resource for animals and plants. Thus, sustainability of our planet’s fresh water reserves is an important issue as population numbers increase. Water accounts for 75% of human body mass and is the major constituent of organism fluids. All these facts indicate that water is one of the most important elements for life on Earth. Thus, “follow the water” has become a mantra of the science of astrobiology. At standard pressure1, water boils at 100◦C. The pressure on the top of Mount Everest is 260Pa, where the boiling point of water is 69C. NUCLEOSYNTHESIS OF CARBON AND OXYGEN: When the fusion of protons into helium continues until the star has exhausted its hydrogen, the temperature in its core rises to about a few times 108 K, allowing the fusion of helium into heavier nuclei. In the first reaction two nuclei of helium, 4He, fuse with each other, creating the nucleus of beryllium, 8Be. However, the 8Be nucleus has an extremely short mean life of just 1016 s, before it decays back again to two 4He nuclei. The rate of production equals the rate of destruction of 8Be nucleus: 4He +4 He ↔8 Be (.4) Nevertheless, the 8Be can capture another 4He nucleus producing the 12C nucleus by the reaction: 8Be +4 He −→12 C + γ (.5) The reactions in Equations .4 and .5 are called the triple-alpha reaction, because three 4He nuclei or alpha particles are necessary for the creation of 12C. This reaction can only create carbon in appreciable amounts because of the existence of a resonance in 12C at the relevant energy for helium burning. Through this resonance the reaction in Equation .5 is enhanced by many orders of magnitude. The production of oxygen nuclei 16O is the result of a capture of another 4He nucleus by the carbon nuclei created in helium burning: 12C +4 He −→16 O + γ (.6) About half of the carbon nuclei produced are converted into
a. helium b. nucleus c. berillium d. oxygen
Q51. arXiv:1803.01157 [gr-qc]: Parameterizing theories of gravity on large and small scales in cosmology, Timothy Clifton, Viraj A. A. Sanghai, (Submitted on 3 Mar 2018); ABSTRACT: We present a link between parameterizations of alternative theories of gravity on large and small scales in cosmology. This relationship is established using theoretical consistency conditions only. We find that in both limits the "slip" and "effective Newton's constant" can be written in terms of a set of four functions of time, two of which are direct generalizations of the α and γ parameters from post-Newtonian physics. To the best of our knowledge, this is the first time that a link between parameterizations of gravity on these very different scales has been established. We expect our result to facilitate the imposition of observational constraints, by drastically reducing the number of functional degress of freedom required to consistently test gravity on multiple scales in cosmology. Conclusions – We have obtained a direct link between horizon-sized cosmological perturbations, and those on smaller non-linear scales, in terms of a set of just four functions of time: {α,γ,αc,γc}. This set of functions parameterize a wide array of minimal modifications to GR, of the type that has been long used to test gravity in the Solar System and binary pulsars. Here we have found that they can be used to describe gravitational physics in the Solar System, astrophysical and small cosmological scales, all the way up to super-horizon scales. To the best of our knowledge, this is the first time that theories of gravity have been parameterized consistently on such a large range of scales, using such a compact set of parameters. These results can be contrasted with the parameterized post-Friedmannian (PPF) and effective field theory (EFT) approaches, which can contain larger numbers of unknown functions, and that often require the degrees of freedom in the theory to be specified from the outset. We expect our parameterization to be useful for testing minimal deviations from GR with future large-scale
a. sets b. surveys c. parameters d. pulsars
Q52. arXiv:1803.01287 [hep-th]: Cosmological correlation functions including a massive scalar field and an arbitrary number of soft-gravitons. Ryo Saito, (Submitted on 4 Mar 2018): ABSTRACT: We study the imprint of a massive scalar particle on cosmological correlation functions, and suggest the way to determine the mass of the newly introduced particle, which is expected to be around 10^14 GeV. After reviewing the basic theory by Maldacena and the effective field theory (EFT) of inflation by Cheung et al., we apply these two theories to construct new couplings of a massive scalar field with primordial fluctuations including an arbitrary number of gravitons. We compute some correlation functions including these couplings in the soft-graviton limit. We show that when the number of soft-gravitons is getting larger, the peak of the correlation function is shifted to larger mass of the scalar particle. In addition we derive a relation, which relates correlation functions with N+1 to N soft-gravitons when the mass of the scalar particle becomes much higher than 10^14 GeV, and confirm the relation by numerical analysis. DETAILS: The methods to obtain the information during inflation have been developed in various ways. One of the most innovative works was done by Maldacena, who applied the quantum field theory to cosmology and computed the three point functions of primordial fluctuations, ζ (scalar fluctuation) and γij (tensor fluctuation or ‘graviton’). Especially the three point function of ζ is important because it tells us the deviation from the Gaussian features of the cosmic state, which is called ‘non-Gaussianity’. CONCLUSIONS:The mass can be around 1014 GeV, which can be estimated as the energy scale during inflation and cannot be detected in terrestrial accelerators. Such a way, which regards inflation as a particle detector, has been developed recently; considering higher spins[8][9], the Standard Model background[10], and so on. Therefore, we hope that our results will give one of the hints to the future observation to seek for unknown
a. spins b. gravitons c. particles d. Quanta
Q53. Ph.D. Thesis by Lady Marjolein Helder: Founder Plant-e from Netherlands: Three plant species were tested (Arundo donax, Spartina anglica and Arundinella anomala). With two of those, Spartina anglica and Arundinella anomala, we were capable of producing bio-electricity and biomass concurrently in the P-MFC. Spartina anglica outperformed Arundinella anomala considering maximum power output (0.22 W m^-2 vs. 0.021 W m^-2). Since Spartina anglica outperformed Arundinella anomala and Spartina anglica is a salttolerant species that can be found under various circumstances around the world, we focused on Spartina anglica for the rest of the thesis. SUMMARY: With Spartina anglica, the maximum power density of the P-MFC was increased to 0.22 W m-2, over 3 times as much as in the first experiment by Strik et al. in 2008. Power output could not be maintained over a longer period of time and polarisation curves showed the anode to be limiting the power output. The plant-growth medium used in the P-MFC contained a lot of nitrate. Removing the nitrate from the plant-growth medium and replacing it for ammonium led to a maximum power density of 0.21 W m-2, and maintain a much higher power density over a longer period of time; 0.15 W m-2. Removing sulphate from the plant-growth medium did not lead to higher power densities. Removal of sulphate from the plant-growth medium resulted in a decrease in power output. The effect of sulphur-cycling within the anode of the P-MFC is still not fully understood and should be researched further. When taking the normal projected efflux of total carbon in the form of CO2 from pastures of 0.09-0.12 kg C m-2 year-1, we could theoretically produce 30-40 mols of electrons per m^2 per year. This would lead to a current density of 0.092-0.122 A m^-2, which was regularly achieved or exceeded during this and other researches. At a voltage of 0.5 V – a cautious estimate of 50% voltage efficiency for the MFC – a power density of 0.046-0.061 W m-2 would be achieved. This is lower than the power density achieved before the start of this thesis project. Three explanations are possible for this difference in numbers: 1. We overestimated our power output per m^2 due to overestimation of the biomass growth. Data from Kuzyakov underestimate the efflux of C from the soil, so in practice breakdown of organic matter is faster than projected and more electrons are released. 2. Microbial activity and carbon turnover is enhanced in the P-MFC due to the availability a new electron-acceptor in the form of the anode. The results with the new plant-growth medium were achieved in a new flat-plate design PMFC. The flat-plate design resulted in a lower internal resistance for the P-MFC as compared to the previously used tubular P-MFC. In total internal resistance can maximally be 0.094 Ω.m^2 in order to reach 3.2 W m^-2. Internal resistance in our experiments ranges from 2-10 Ω.m^2, so power density doesn’t exceed 0.4 W m^-2 and current density doesn’t exceed 1.6 A m^-2. In the tubular system highest partial internal resistance was transport resistance, which was limited in the flat-plate system due to a smaller anode-cathode
a. distance b. power c. area d. configuration.
Q54. arXiv:1803.01639 [q-bio.PE]: When do we have the power to detect biological interactions in spatial point patterns? T. Rajala, S. Olhede, D.J. Murrell: (Submitted on 5 Mar 2018): ABSTRACT: Determining the relative importance of environmental factors, biotic interactions and stochasticity in assembling and maintaining species-rich communities remains a major challenge in ecology. In plant communities, interactions between individuals of different species are expected to leave a spatial signature in the form of positive or negative spatial correlations over distances relating to the spatial scale of interaction. Most studies using spatial point process tools have found relatively little evidence for interactions between pairs of species. More interactions tend to be detected in communities with fewer species. However, there is currently no understanding of how the power to detect spatial interactions may change with sample size, or the scale and intensity of interactions. We use a simple 2-species model where the scale and intensity of interactions are controlled to simulate point pattern data. In combination with an approximation to the variance of the spatial summary statistics that we sample, we investigate the power of current spatial point pattern methods to correctly reject the null model of bivariate species independence. We show that the power to detect interactions is positively related to the abundances of the species tested, and the intensity and scale of interactions. Increasing imbalance in abundances has a negative effect on the power to detect interactions. At population sizes typically found in currently available datasets for species-rich plant communities we find only a very low power to detect interactions. Differences in power may explain the increased frequency of interactions in communities with fewer species. Furthermore, the community-wide frequency of detected interactions is very sensitive to a minimum abundance criterion for including species in the analyses. In conclusion, we hope our main contribution is to encourage more users to consider explicitly the ability of the spatial point pattern tests to detect significant associations between species. We have shown that the data requirements to detect even strong interactions may be quite high, mirroring results for null model tests of species co-occurrences in community matrix data. On this basis, we suggest it is desirable to only interpret the frequency of interactions across large numbers of species once the effect of different powers to detect interactions for pairs of species of given population sizes has been (even approximately) factored out. This seems especially important in comparative analyses across different communities where the spatial scales, strengths of interactions and the species abundance distributions may differ and affect the power to detect
a. abundances b. methods c. communities d. interactions
Q55.arXiv:1803.00940 [cs.CV]: Protecting JPEG Images Against Adversarial Attacks: Aaditya Prakash, Nick Moran, Solomon Garber, Antonella DiLillo, James Storer: (Submitted on 2 Mar 2018): ABSTRACT: As deep neural networks (DNNs) have been integrated into critical systems, several methods to attack these systems have been developed. These adversarial attacks make imperceptible modifications to an image that fool DNN classifiers. We present an adaptive JPEG encoder which defends against many of these attacks. Experimentally, we show that our method produces images with high visual quality while greatly reducing the potency of state-of-the-art attacks. Our algorithm requires only a modest increase in encoding time, produces a compressed image which can be decompressed by an off-the-shelf JPEG decoder, and classified by an unmodified classifier. DETAILS: Deep neural networks (DNNs) have shown tremendous success in image recognition tasks, even surpassing human capability. DNNs have become components of many critical systems, such as self-driving cars, medical image segmentation, surveillance, and malware classification. However, recent research has shown that DNNs are vulnerable to adversarial attacks, in which minute, carefully-chosen image perturbations can result in misclassification of the image by the neural network. In most cases, this change is imperceptible to humans (the resulting image is visually indistinguishable from the original). CONCLUSIONS:We have presented Aug-MSROI, an augmentation of MSROI [17] to employ semantic JPEG compression as an effective defenseagainststate-of-the-artadversarialattacks. In our experiments, JPEG compression employing Aug-MSROI produces compressed images, which, when decompressed, have high visual quality while at the same time preserving the accuracy of classification by a neural network. A key advantage of our approach is that, with only a modest increase in encoding time, like standard MSROI, it produces compressed images that can be decompressed by any off-the-shelf JPEG
a. segment b. decoder c. encoder d. Splaser
Q56. arXiv:1803.02163 [astro-ph.HE]: Revisit of cosmic ray antiprotons from dark matter annihilation with updated constraints on the background model from AMS-02 and collider data: Ming-Yang Cui, Xu Pan, Qiang Yuan, Yi-Zhong Fan, Hong-Shi Zong: (Submitted on 6 Mar 2018): ABSTRACT: We study the cosmic ray antiprotons with updated constraints on the propagation, proton injection, and solar modulation parameters based on the newest AMS-02 data near the Earth and Voyager data in the local interstellar space, and on the cross section of antiproton production due to proton-proton collisions based on new collider data. We use a Bayesian approach to properly consider the uncertainties of the model predictions of both the background and the dark matter (DM) annihilation components of antiprotons. We find that including an extra component of antiprotons from the annihilation of DM particles into a pair of quarks can improve the fit to the AMS-02 antiproton data considerably. The favored mass of DM particles is about 60∼100GeV, and the annihilation cross section is just at the level of the thermal production of DM (⟨σv⟩∼O(10^−26) cm^ 3~s^−1). DETAILS: Cosmic ray (CR) antiprotons are one of the most important probes to indirectly detect dark matter (DM) particles.The antiproton background produced by inelastic collisions between protons and the interstellar medium can be calculated using the same propagation, proton injection, and solar modulation parameters (referred to as background parameters hereafter) obtained through fitting to the proton flux data. CONCLUSIONS: We find that the AMS-02 antiproton data favor a DM component with mass of 60 ∼ 100 GeV and annihilation cross section of (0.7 ∼ 7)× 10−26 cm3 s−1, for an assumed b¯ b channel. The Bayes factor of the DM component is about 8.4. These results are consistent with previous works based on different propagation parameters and antiproton production cross sections. There is probably one caveat of the current study. We have assumed that the solar modulation effects of protons and antiprotons are similar, with the only difference of the data-taking time which corresponds to different solar activities. It is, however, possible that the solar modulation is charge-sign-
a. Independant b. Oscillatory c. dependant d. reversal.
Q57. arXiv:1803.01866 [hep-ph]: Spin-2 Portal Dark Matter: Nicolas Bernal, Maira Dutra, Yann Mambrini, Keith A. Olive, Marco Peloso, Mathias Pierre;(Submitted on 5 Mar 2018); ABSTRACT: We generalize models invoking a spin-2 particle as a mediator between the dark sector and the Standard Model. We show that a massive spin-2 messenger can efficiently play the role of a portal between the two sectors. The dark matter is then produced via a freeze-in mechanism during the reheating epoch. In a large part of the parameter space, production through the exchange of a massive spin-2 mediator dominates over processes involving a graviton with Planck suppressed couplings. We perform a systematic analysis of such models for different values of the spin-2 mass relative to the maximum and the final temperature attained at reheating. DETAILS: Although there is a large amount of indirect evidence for the presence of dark matter in the Universe from astrophysical observations, its precise nature remains elusive. Moreover, although there has been an impressive increased sensitivity in direct and indirect detection searches, no signal has been confirmed so far. CONCLUSIONS: We generalized our study to any massive spin-2 state with stress-energy tensor couplings to the standard model and the dark sector. In a large part of the parameter space, the massive spin-2 portal dominates over the (Planck-suppressed) graviton exchange. We have performed an exhaustive analysis, considering cases where the spin-2 field is both heavier and lighter than the reheating temperature. In both cases, the freeze-in process dominates the production, while enhanced during the reheating phase (heavy mediator case) or through its resonant production (light mediator case). We have also shown that our results are greatly influenced by taking into account the effects of non-instantaneous reheating. Not only do we recover boost factors in the production due to the large dependence on the temperature of the rate R(T), but we have also shown that the presence of a mediator between TRH and Tmax strongly enhances the relic abundance due to rapid s-channel production when T ~ m˜ h. IMPORTANT:We have shown that dark matter can naturally be produced through a spin-2
a. portal b. graviton c. mass d. state
Q58. arXiv:1803.01109 [gr-qc]: Structure of Strange quark star in dilaton gravity: A.R.Peivand, K.Naficy, G.H.Bordbar; (Submitted on 3 Mar 2018): ABSTRACT: In this work, we have first obtained the hydrostatic equilibrium equation in dilaton gravity. Then we have examined some of the structural characteristics of strange quark star in dilaton gravity with a background of Einstein gravity. We have shown that the variations of dilaton parameter do not affect the maximum mass of quark star, while the variations of the cosmological constant lead to change in the structural characteristics of the quark star. We have investigated the stability of strange quark stars that studied by MIT Bag model, in dilaton gravity. We have also provided limiting values for the dilaton field parameter and the cosmological constant.We have also studied the effects of dilaton gravity on the other properties of quark star such as the mean density and gravitational redshift. We have concluded that the last reported value for cosmological constant does not affect on maximum mass of strange quark star. CONCLUSIONS: We have obtained HEE of a compact object in dilaton gravity by using two approaches and then by using the obtained HEEs we have calculated some structural properties of SQS. We have assumed that the dilaton gravity has constructed from dilaton field with a potential, including two Liouville type terms in the background of Einstein gravity. We have seen that in the values of α and Λ where HEE in dilaton gravity has a logical answer, SQS does not change with variations of α. This behavior also persists in different values of the bag constant. On the other hand, increasing Λ enhances the maximum mass. We have seen that the percentage increase of maximum mass of SQS has higher values for SQSs that are more stable than others. We have shown that effect of dilaton gravity and applying smaller bag constant in EoS of SQM on the SQS has led to existence SQSs with bigger masses and radii that are more stable than SQSs in Einstein gravity. Since the values of Mmax and radius for Λ < 10^−14 are the same values for Λ = 0 and cosmological observations suggest Λ ≤ 3×10^−56cm^−2, it can be concluded that this limit of the cosmological constant does not affect on SQS structure in dilaton
a. cosmology b. HEE c. gravity d. gravitation
Q59. arXiv:1804.01234 [math-ph]:Taking Inspiration from Quantum-Wave Analogies --- Recent Results for Photonic Crystals: Max Lein, (Submitted on 4 Apr 2018): ABSTRACT: Similarities between quantum systems and analogous systems for classical waves have been used to great effect in the physics community, be it to gain an intuition for quantum systems or to anticipate novel phenomena in classical waves. This proceeding reviews recent advances in putting these quantum-wave analogies on a mathematically rigorous foundation for classical electromagnetism. Not only has this Schr\"odinger formalism of electromagnetism led to new, interesting mathematical problems for so-called Maxwell-type operators, it has also improved the understanding of the physics of topological phenomena in electromagnetic media. For example, it enabled us to classify electromagnetic media by their material symmetries, and explained why "fermionic time-reversal symmetries" --- that were conjectured to exist in the physics literature --- are in fact forbidden. CONCLUSIONS: In summary, the Schrödinger formalism of electromagnetism and other classical waves opens the door to systematically adapting techniques from quantum mechanics to classical Systematically developing mathematical techniques for Maxwell-type operators waves. Two specific cases were covered here, effective dynamics in adiabatically perturbed photonic crystals and the topological classification of electromagnetic media. This is not just relevant to mathematical physicists, but at least the latter result is new for and of immediate interest to physicists. Going forward, quantum-wave analogies will continue to serve as inspiration for mathematical, theoretical and experimental physicists. Experimentalists enjoy the much wider latitude with which media for classical waves can be engineered. Depending on the circumstances, they may choose the most suitable wave (acoustic, electromagnetic, etc.) and wavelength regime. For instance, the dynamics of spin wave packets can be “filmed” because their propagation speed is much lower than that of light, something that would be very hard to impossible to realize with a quantum system. Theoreticians can rely on quantum-wave or wave-wave analogies to transfer insights from one physical system to another and to propose novel experiments. And mathematicians can find a whole host of interesting and non-trivial problems that are of immediate relevance to
a. Physics b. Mathphysics c. quantum systems d. Media.
Q60. Xiv:1804.00963 [math.GR]: The Spin Group in Superspace: Hennie De Schepper, Alí Guzmán Adán, Frank Sommen: (Submitted on 3 Apr 2018): ABSTRACT: There are two well-known ways of describing elements of the rotation group SO(m). First, according to the Caarrtan-Dieudonn\'e theorem, every rotation matrix can be written as an even number of reflections. And second, they can also be expressed as the exponential of some anti-symmetric matrix. In this paper, we study similar descriptions of the corresponding extension of SO(m) to superspace. The setting is natural to describe the behavior of bosonic and fermionic particles. This group of super-rotations SO0is also an extension of the symplectic group. While still being connected, it is thus no longer compact. As a consequence, it cannot be fully described by just one action of the exponential map on its Lie algebra. Instead, we obtain an Iwasawa-type decomposition for this group in terms of three exponentials acting on three direct summands of the corresponding Lie algebra of supermatrices. At the same time, SO0 strictly contains the group generated by super-vector reflections. Therefore, its Lie algebra is isomorphic to a certain extension of the algebra of superbivectors. This means that the Spin group in superspace has to be seen as the group generated by the exponentials of the so-called extended superbivectors in order to cover SO0. We also study the actions of this Spin group on supervectors and provide a proper subset of it that is a double cover of SO0. Finally, we show that every fractional Fourier transform in n bosonic dimensions can be seen as an element of the spin group in superspace. Conclusions and future work: In this paper we have shown that vector reflections in superspace are not enough to describe the set of linear transformations leaving the inner product invariant. This constitutes a very important difference with the classical case in which the algebra of bivectors x ∧ y is isomorphic to the special orthogonal algebra so(m). Such a property is no longer fulfilled in this setting. The real projection of the algebra of superbivectors R(2) m|2n (ΛN) does not include the symplectic algebra structure which is present in the Lie algebra of supermatrices so0, corresponding to the group of super rotations. That fact has an major impact on the definition of the Spin group in this setting. The set of elements defined through the multiplication of an even number of unit vectors in superspace does not suffice for describing Spin(m|2n)(ΛN). A suitable alternative, in this case, is to define the (super) spin elements as products of exponentials of extended superbivectors. Such an extension of the Lie algebra of superbivectors contains, through the corresponding identifications, harmonic oscillators. This way, we obtain the Spin group as a cover of the set of superrotations SO0 through the usual representation h. In addition, every fractional Fourier transform can be identified with a spin element. In forthcoming work, we will prove the invariance of the (super) Dirac operator ∂x under the corresponding actions of this (super) Spin group. We will also study the invariance of the Hermitian system under the action of the corresponding Spin subgroup in superspace.
a. pseudospace b. superspace c. representation d. setting.
Q61. arXiv:1804.00548 [quant-ph]: Relativistic probability amplitudes I. Massive particles of any spin: Scott E. Hoffmann: (Submitted on 30 Mar 2018): ABSTRACT: We consider a massive particle of arbitrary spin and the basis vectors that carry the unitary, irreducible representations of the Poincar\'e group. From the complex coefficients in normalizable superpositions of these basis vectors, we identify momentum/spin-component probability amplitudes with the same interpretation as in the nonrelativistic theory. We find the relativistic transformations of these amplitudes, which are unitary in that they preserve the modulus-squared of scalar products from frame to frame. Space inversion and time reversal are also treated. We reconsider the Newton- Wigner construction of eigenvectors of position and the position operator. Position/spin-component probability amplitudes are also identified and their relativistic, unitary, transformations derived. Again, space inversion and time reversal are considered. For reference, we show how to construct positive energy solutions of the Klein-Gordon and Dirac equations in terms of probability amplitudes. We find the boost transformation of the position operator in the spinless case and present some results on the relativity of position measurements. We consider issues surrounding the classical concept of causality as it applies in quantum mechanics. We briefly examine the relevance of the results presented here for theories of interaction. CONCLUSIONS: We have defined momentum/spin-component probability amplitudes and position/spin-component probability amplitudes for a massive particle of general spin. We have found their transformation properties under space-time translations, general Lorentz transformations, space inversion and time reversal. We have defined the position operator and derived its relativistic transformation properties. The results are all very close to what is done in nonrelativistic quantum mechanics. This should come as no surprise, since any relativistic theory must reduce to the nonrelativistic form for small velocities. We discussed the limitations on the concept of causality imposed by the uncertainty principle. We discussed how relativistic probability amplitudes must be a part of any theory of interaction, including quantum field
a. expression b. theory c. probability d. transformation.
Answers
Q1d. Q2b. Q3a. Q4c. Q5b. Q6a. Q7b. Q8d. Q9b. Q10c. Q11b. Q12b. Q13b. Q14d. Q15a. Q16d. Q17d. Q18a. Q19d. Q20b. Q21a. Q22c. Q23d. Q24b. Q25a. Q26d. Q27d. Q28c. Q29a. Q30c. Q31c. Q32b. Q33d. Q34a. Q35b. Q36d. Q37c. Q38a. Q39c. Q40b. Q41d. Q42b. Q43c. Q44a. Q45d. Q46b. Q47a. Q48c. Q49b. Q50d. Q51b. Q52c. Q53a. Q54d. Q55b. Q56c. Q57a. Q58c. Q59a. Q60b. Q61b.
Continued truwiz 119b.
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