Miracle-dz/UniFAR-FTUs huggingface dataset:
The Paucity of Supershear Earthquakes on Large Faults Governed by Rate and State Friction

Supershear earthquakes are rare compared to their subshear counterparts, but the cause for their paucity remains to be understood. We investigate for the first time the prevalence of supershear ruptures across multiple earthquake cycles on long faults using rate‐and‐state friction and a 2.5D approximation that accounts for the finite seismogenic width W. We find supershear events occur only in a narrow range of friction parameters that is not commonly observed in laboratory experiments, which may explain its rarity in nature. Particularly, the ratio between direct and evolution effects of rate‐and‐state friction needs to be low (a/b < 0.4) and the nucleation length has to be sufficiently large compared to W, but not too large that it causes a transition from seismic to aseismic slip. Our numerical and analytical developments contribute fundamentally to understanding the state of stress on long faults over multiple earthquake cycles and their potential for hosting supershear earthquakes.
The background Friedmannian Hubble constant in relativistic inhomogeneous cosmology and the age of the Universe

In relativistic inhomogeneous cosmology, structure formation couples to average cosmological expansion. A conservative approach to modelling this assumes an Einstein--de Sitter model (EdS) at early times and extrapolates this forward in cosmological time as a "background model" against which average properties of today's Universe can be measured. This requires adopting an early-epoch--normalised background Hubble constant $H_1^{bg}$. Here, we show that the $\Lambda$CDM model can be used as an observational proxy to estimate $H_1^{bg}$ rather than choose it arbitrarily. We assume (i) an EdS model at early times; (ii) a zero dark energy parameter; (iii) bi-domain scalar averaging---division of the spatial sections into over- and underdense regions; and (iv) virialisation (stable clustering) of collapsed regions. We find $H_1^{bg}= 37.7 \pm 0.4$ km/s/Mpc (random error only) based on a Planck $\Lambda$CDM observational proxy. Moreover, since the scalar-averaged expansion rate is expected to exceed the (extrapolated) background expansion rate, the expected age of the Universe should be much less than $2/(3 H_1^{bg}) = 17.3$ Gyr. The maximum stellar age of Galactic Bulge microlensed low-mass stars (most likely: 14.7 Gyr; 68\% confidence: 14.0--15.0 Gyr) suggests an age about a Gyr older than the (no-backreaction) $\Lambda$CDM estimate.
Nonspherically symmetric black string perturbations in the large dimension limit

We consider non-spherically symmetric perturbations of the uncharged black string/flat black brane in the large dimension (D) limit of general relativity. We express the perturbations in a simplified form using variables introduced by Ishibashi and Kodama. We apply the large D limit to the equations, and show that this leads to decoupling of the equations in the near-horizon and asymptotic regions. It also enables use of matched asymptotic expansions to obtain approximate analytical solutions and to analyze stability of the black string/brane. For a large class of non-spherically symmetric perturbations, we prove that there are no instabilities in the large D limit. For the rest, we provide additional matching arguments that indicate that the black string/brane is stable. In the \emph{static} limit, we show that for \emph{all} non-spherically symmetric perturbations, there is no instability. This is proof that the Gross-Perry-Yaffe mode for semiclassical black hole perturbations is the unique unstable mode even in the large D limit. This work is also a direct analytical indication that the only instability of the black string is the Gregory-Laflamme instability.
Tuning the ferroelectric-to-paraelectric transition temperature and dipole orientation of group-IV monochalcogenide monolayers

Coordination-related, two-dimensional (2D) structural phase transitions are a fascinating facet of two-dimensional materials with structural degeneracies. Nevertheless, a unified theoretical account of these transitions remains absent, and the following points are established through ab initio molecular dynamics and 2D discrete clock models here: Group-IV monochalcogenide (GeSe, SnSe, SnTe,.) monolayers have four degenerate structural ground states, and a phase transition from a threefold coordinated onto a fivefold coordinated structure takes place at finite temperature. On unstrained samples, this phase transition requires lattice parameters to evolve freely. A fundamental energy scale $J$ permits understanding this transition, and numerical results indicate a transition temperature ${T}_{c}$ of about $1.41J$. Numerical data provides a relation among the experimental (rhombic) parameter $\ensuremath{\langle}\mathrm{\ensuremath{\Delta}}\ensuremath{\alpha}\ensuremath{\rangle}$ [Chang et al., Science 353, 274 (2016)] and $T$ of the form $\ensuremath{\langle}\mathrm{\ensuremath{\Delta}}\ensuremath{\alpha}\ensuremath{\rangle}=\mathrm{\ensuremath{\Delta}}\ensuremath{\alpha}(T=0){\left(1\ensuremath{-}T/{T}_{c}\right)}^{\ensuremath{\beta}}$, with a critical exponent $\ensuremath{\beta}\ensuremath{\simeq}1/3$ that coincides with experiment. It is also shown that $\ensuremath{\langle}\mathrm{\ensuremath{\Delta}}\ensuremath{\alpha}\ensuremath{\rangle}$ is temperature independent in another theoretical work [Fei et al., Phys. Rev. Lett. 117, 097601 (2016)], and thus incompatible with experiment. ${T}_{c}$ and the orientation of the in-plane intrinsic electric dipole can be controlled by moderate uniaxial tensile strain, and a modified discrete clock model describes the transition on strained samples qualitatively. An analysis of out-of-plane fluctuations and a discussion of the need for van der Waals corrections to describe these materials are given too. These results provide an experimentally compatible framework to understand structural phase transitions in 2D materials and their effects on material properties.
PHOTOMETRIC ANALYSIS OF OVERCONTACT BINARIES AK HER, HI DRA, V1128 TAU, AND V2612 OPH

We analyze new, high quality multicolor light curves of four overcontact binaries: AK Her, HI Dra, V1128 Tau, and V2612 Oph, and determine their orbital and physical parameters using the modeling program of G. Djurasevic and recently published results of radial velocity studies. The achieved precision in absolute masses is between 10% and 20%, and the precision in absolute radii is between 5% and 10%. All four systems are W UMa-type binaries with bright or dark spots indicative of mass and energy transfer or surface activity. We estimate the distances and the ages of the systems using the luminosities computed through our analysis, and perform an O − C study for V1128 Tau, which reveals a complex period variation that can be interpreted in terms of mass loss/exchange and either the presence of the third body, or the magnetic activity on one of the components. We conclude that further observations of these systems are needed to deepen our understanding of their nature and variability.
PARSEC-SCALE ACCRETION AND WINDS IRRADIATED BY A QUASAR

We present numerical simulations of properties of a parsec-scale torus exposed to illumination by the central black hole in an active galactic nucleus (AGN). Our physical model allows to investigate the balance between the formation of winds and accretion simultaneously. Radiation-driven winds are allowed by taking into account radiation pressure due to UV and IR radiation along with X-ray heating and dust sublimation. Accretion is allowed through angular momentum transport and the solution of the equations of radiative, viscous radiation hydrodynamics. Our methods adopt flux-limited diffusion radiation hydrodynamics for the dusty, infrared pressure driven part of the flow, along with X-ray heating and cooling. Angular momentum transport in the accreting part of the flow is modeled using effective viscosity. Our results demonstrate that radiation pressure on dust can play an important role in shaping AGN obscuration. For example, when the luminosity illuminating the torus exceeds L > 0.01 L Edd ? > , where LEdd is the Eddington luminosity, we find no episodes of sustained disk accretion because radiation pressure does not allow a disk to form. Despite the absence of the disk accretion, the flow of gas to smaller radii still proceeds at a rate 10−4–10−1 M ⊙ yr − 1 ? > through the capturing of the gas from the hot evaporative flow, thus providing a mechanism to deliver gas from a radiation–pressure dominated torus to the inner accretion disk. As L / L edd ? > increases, larger radiation input leads to larger torus aspect ratios and increased obscuration of the central black hole. We also find the important role of the X-ray heated gas in shaping the obscuring torus.
Performance Improvement of Mechanically Beam-Steerable Transmitarray Antennas by Using Offset Unifocal Phase Symmetry

This communication presents the concept of offset unifocal phase symmetry to improve the performance (gain, gain roll-off, sidelobe level, etc.,) of mechanically beam-steerable transmitarray (TA) antennas. The phase shifts are initially determined from an offset feed source to make the corresponding TA antenna radiate a tilted beam with high gain. The phase shifts are asymmetric and can be broadly divided into dominant and ordinary phase shifts with respect to the offset feed source. By mirroring the dominant phase shifts to make the phase shifts symmetric, it can enable symmetric radiation beams for symmetric offset feed sources and improve phase error. When the offset feed source is moving inward to steer the main beam, the phase error of the phase-shifting surface with respect to the feed source starts to occur, while the electric-field spillover/illumination from the feed source is improved, which can maintain the gains of scanning beams. To verify the validity of the concept, the performance of a beam-steerable TA antenna enabled by the offset unifocal phase symmetry has been simulated and compared with the counterparts of unifocal and bifocal beam-steerable TA antennas. The measured results agree well with the simulated ones, revealing that the beam-steerable TA antenna enabled by the offset unifocal phase symmetry can maintain realized gains of scanning beams, suppress sidelobe levels, and reduce gain roll-off within the beam-scanning coverage. The offset unifocal phase symmetry, in principle, is a generalized approach and applicable to reflectarray antennas to improve the beam-steerable performance as well.
Millimeter and submillimeter excess emission in M 33 revealed by Planck and LABOCA

Previous studies have shown the existence of an excess of emission at submillimeter (submm) and millimeter (mm) wavelengths in the spectral energy distribution (SED) of many low-metallicity galaxies. The goal of the present study is to model separately the emission from the star forming (SF) component and the emission from the diffuse interstellar medium (ISM) in the nearby spiral galaxy M33. We decomposed the observed SED of M33 into its SF and diffuse components. Mid-infrared (MIR) and far-infrared (FIR) fluxes were extracted from Spitzer and Herschel data. At submm and mm wavelengths, we used ground-based observations from APEX to measure the emission from the SF component and data from the Planck space telescope to estimate the diffuse emission. Both components were separately fitted using radiation transfer models based on standard dust properties and a realistic geometry. Both modeled SEDs were combined to build the global SED of M33. In addition, the radiation field necessary to power the dust emission in our modeling was compared with observations from GALEX, Sloan, and Spitzer. Our modeling is able to reproduce the observations at MIR and FIR wavelengths, but we found a strong excess of emission at submm and mm wavelengths, where the model expectations severely underestimate the LABOCA and Planck fluxes. We also found that the ultraviolet (UV) radiation escaping the galaxy is 70% higher than the model predictions. We determined a gas-to-dust mass ratio Gdust~100, significantly lower than the value expected from the sub-solar metallicity of M33. We discussed different hypotheses to explain the discrepancies found in our study (i.e., excess of emission at submm and mm wavelengths, deficit of UV attenuation, and abnormally low value of Gdust), concluding that different dust properties in M33 is the most plausible explanation.
Spatial Variations of Turbulent Properties of Neutral Hydrogen Gas in the Small Magellanic Cloud Using Structure-function Analysis

We investigate spatial variations of turbulent properties in the Small Magellanic Cloud (SMC) by using neutral hydrogen (H i) observations. With the goal of testing the importance of stellar feedback on H i turbulence, we define central and outer SMC regions based on the star formation rate (SFR) surface density, as well as the H i integrated intensity. We use the structure function and the velocity channel analysis to calculate the power-law index (γ) for both underlying density and velocity fields in these regions. In all cases, our results show essentially no difference in γ between the central and outer regions. This suggests that H i turbulent properties are surprisingly homogeneous across the SMC when probed at a resolution of 30 pc. Contrary to recent suggestions from numerical simulations, we do not find a significant change in γ due to stellar feedback as traced by the SFR surface density. This could be due to the stellar feedback being widespread over the whole of the SMC, but more likely due to a large-scale gravitational driving of turbulence. We show that the lack of difference between central and outer SMC regions cannot be explained by the high optical depth H I.
Ultracold atom-molecule collisions with fermionic atoms

Elastic and inelastic properties of weakly bound s- and p-wave molecules of fermionic atoms that collide with a third atom are investigated. Analysis of calculated collisional properties of s-wave dimers of fermions in different spin states permit us to compare and highlight the physical mechanisms that determine the stability of s-wave and p-wave molecules. In contrast to s-wave molecules, the collisional properties of p-wave molecules are found to be largely insensitive to variations of the p-wave scattering length and that these collisions will usually result in short molecular lifetimes. We also discuss the importance of this result for both theories and experiments involving degenerate Fermi gases.
Finite width induced modification to the electromagnetic form factors of spin-1 particles

The inclusion of the unstable features of a spin-1 particle, without breaking the electromagnetic gauge invariance, can be properly accomplished by including higher order contributions as done in the so-called fermion loop scheme (for the $W$ gauge boson) and the boson loop scheme (for vector mesons). This induces a nontrivial modification to the electromagnetic vertex of the particle, which must be considered in addition to any other contribution computed as stable particles. Considering the modified electromagnetic vertex, we obtain general expressions for the corresponding corrections to the multipoles as a function of the mass of the particles in the loop. For the $W$ gauge boson no substantial deviations from the stable case are observed. For the $\ensuremath{\rho}$ and ${K}^{*}$ mesons the mass of the particles in the loop has a significant effect, and can be comparable with corrections of a different nature.
Correlation dimension of inertial particles in random flows

We obtain an implicit equation for the correlation dimension D2 of dynamical systems in terms of an integral over a propagator. We illustrate the utility of this approach by evaluating D2 for inertial particles suspended in a random flow. In the limit where the correlation time of the flow field approaches zero, taking the short-time limit of the propagator enables D2 to be determined from the solution of a partial differential equation. We develop the solution as a power series in a dimensionless parameter which represents the strength of inertial effects.
Features in single field slow-roll inflation

We compare the effects of local features (LF) and branch features (BF) of the inflaton potential on the spectrum of primordial perturbations. We show that LF affect the spectrum in a narrow range of scales while BF produce a step between large and small scales with respect to the featureless spectrum. We comment on the possibility of distinguishing between these two types of feature models from the analysis of the Cosmic Microwave Background (CMB) radiation data. We also show that there exists a quantitative similarity between the primordial spectra predicted by two of the BF potentials considered. This could lead to a degeneracy of their predicted CMB temperature spectra which could make difficult to discriminate between the models from a CMB analysis. We comment on the possibility that the degeneracy can be broken when higher order terms in the perturbations are considered. In this sense non-Gaussianity may play an important role in discerning between different inflationary models which predict similar spectra.
Preliminary Design of ARIES-Devasthal Faint Object Spectrograph and Camera

We present here the preliminary design of ARIES-Devasthal Faint Object Spectrograph and Camera (ADFOSC), which is a multi-mode instrument for both imaging and spectroscopy. ADFOSC is the first-generation instrument to be mounted at the axial port of the Cassegrain focus on our new 3.6m optical telescope to be installed at Devasthal, Nainital. The main design goals of the instrument are : the instrument will have capability of broad- and narrow-band imaging, low-medium resolution spectroscopy, and imaging polarimetry. The operating wavelength range will be from 360 to 1000 nm and the instrument will have remote-control capability.
The Occurrence of Non-Pulsating Stars in the gamma Dor and delta Set Pulsation Instability Regions: Results from Kepler Quarter 14-17 Data

Abstract In our October 2013 Astronomical Review article, we discussed the statistics of variability for 633 relatively faint (Kepler magnitude 14-16) spectral type A-F stars observed by the Kepler spacecraft as part of the Guest Observer program during Quarters 6-13 (June 2010-June 2012). We found six stars that showed no variability with with amplitude 20 ppm level or greater in the range 0.2 to 24.4 cycles/day, but whose positions in the log g – Teff plane put them in the delta Set or gamma Dor pulsation instability regions established from pre-Kepler groundbased observations. Here we present results for an additional 2100+ stars observed during Quarters 14-17 (June 2012-December 2013), until the second of Kepler’s four reaction-wheels failed, ending Kepler’s planet-search mission in the Cygnus-Lyra region. This sample is not unbiased, as we limited our target list to stars showing variability in Quarter 0 full-frame images to enhance our variable star discovery rate. We find that 46% of these stars show no frequencies in the Fourier transform of their light curves down to the 20-ppm level. We find 35 additional stars that lie within the ground-based gamma Dor /delta Set pulsation instability regions; their lack of pulsations requires explanation. In the analysis for our first paper, we included a +229 K offset to the Kepler Input Catalog Teff to take into account an average systematic difference between the KIC values and the Teff derived from SDSS color photometry for main-sequence F stars (Pinsonneault et al. 2012). Here we compare the KIC catalog Teff value and the Teff derived from spectroscopy taken by the LAMOST instrument (Molenda-Zakowicz et al. 2013) for 51 stars in common to determine whether the 229 K offset should be applied to our target stars, and the implications for the location of the constant stars relative to the instability region boundaries. Finally, we also review possible explanations for the constant stars that lie within the pulsation instability regions, and consider whether super-Nyquist frequencies (>24.4 cycles/day), if they existed, would have been detected in the long-cadence data via their reflections at low frequencies, as discussed by Murphy et al. (2013).
Nonperturbative stochastic method for driven spin-boson model

Department of Physics, Yale University, New Haven, Connecticut 06520, USAWe introduce and apply a numerically exact method for investigating the real-time dissipativedynamics of quantum impurities embedded in a macroscopic environment beyond the weak-couplinglimit. We focus on the spin-boson Hamiltonian that describes a two-level system interacting witha bosonic bath of harmonic oscillators. This model is archetypal for investigating dissipation inquantum systems and tunable experimental realizations exist in mesoscopic and cold-atom systems.It nds abundant applications in physics ranging from the study of decoherence in quantum com-puting and quantum optics to extended dynamical mean- eld theory. Starting from the real-timeFeynman-Vernon path integral, we derive an exact stochastic Schrodinger equation that allows usto compute the full spin density matrix and spin-spin correlation functions beyond weak coupling.We greatly extend our earlier work (P. P. Orth, A. Imambekov, and K. Le Hur, Phys. Rev. A82, 032118 (2010)) by eshing out the core concepts of the method and by presenting a number ofinteresting applications. Methodologically, we present an analogy between the dissipative dynamicsof a quantum spin and that of a classical spin in a random magnetic eld. This analogy is used torecover the well-known non-interacting-blip-approximation in the weak-coupling limit. We explainin detail how to compute spin-spin autocorrelation functions. As interesting applications of ourmethod, we explore the non-Markovian e ects of the initial spin-bath preparation on the dynamicsof the coherence ˙
ASPECTS OF THE HOLOGRAPHIC STUDY OF FLAVOR DYNAMICS

This thesis is dedicated to the holographic study of flavor dynamics. The technique employed is a D7-brane probing of various D3-brane backgrounds. The first topic covered studies the influence of an external magnetic field on a flavored large N Yang-Mills theory. The theory exhibits spontaneous chiral symmetry breaking. The meson spectrum exhibits Zeeman splitting and characteristic GMOR relation. The second topic examines thermal properties of the dual gauge theory. The third topic studies the phase structure of the finite temperature dual gauge theory in the presence of magnetic field. A phase diagram of the theory is obtained and the meson spectrum is explored. The fourth topic studies the addition of an external electric field. The observed effect is dissociation of the bound quarks, favoring the meson melting, the dissociation of mesons corresponds to an insulator/conductor phase transition. The fifth topic studies the addition of an R-charge chemical potential via brane probing of the spinning D3-brane geometry. The corresponding phase diagram is obtained. The chemical potential favors the dissociation of mesons. The last topic explores universal properties of gauge theories dual to the Dp/Dq system. A universal discrete self-similar behavior associated to the insulator/conductor phase transition is observed and the corresponding scaling exponents are computed.