ShantanuT01/DACTYL-Pretraining huggingface dataset:
A stripline-type near-field microwave probe is microfabricated for microwave impedance microscopy. Unlike the poorly shielded coplanar probe that senses the sample tens of microns away, the stripline structure removes the stray fields from the cantilever body and localizes the interaction only around the focused-ion beam deposited Pt tip. The approaching curve of an oscillating tip toward bulk dielectrics can be quantitatively simulated and fitted to the finite-element analysis result. The peak signal of the approaching curve is a measure of the sample dielectric constant and can be used to study unknown bulk materials.
The Navier--Stokes order hydrodynamic equations for a low-density driven granular mixture obtained previously [Khalil and Garz\'o, Phys. Rev. E \textbf{88}, 052201 (2013)] from the Chapman--Enskog solution to the Boltzmann equation are considered further. The four transport coefficients associated with the heat flux are obtained in terms of the mass ratio, the size ratio, composition, coefficients of restitution, and the driven parameters of the model. Their quantitative variation on the control parameters of the system is demonstrated by considering the leading terms in a Sonine polynomial expansion to solve the exact integral equations. As an application of these results, the stability of the homogeneous steady state is studied. In contrast to the results obtained in undriven granular mixtures, the stability analysis of the linearized Navier--Stokes hydrodynamic equations shows that the transversal and longitudinal modes are (linearly) stable with respect to long enough wavelength excitations. This conclusion agrees with a previous analysis made for single granular gases.
In this paper, a branching random walk $(V(x))$ in the boundary case is studied, where the associated one dimensional random walk is in the domain of attraction of an $\alpha-$stable law with $1<\alpha<2$. Let $M_n$ be the minimal position of $(V(x))$ at generation $n$. We established an integral test to describe the lower limit of $M_n-\frac{1}{\alpha}\log n$ and a law of iterated logarithm for the upper limit of $M_n-(1+\frac{1}{\alpha})\log n$.
Let $X \hookrightarrow \mathbb{P}^r$ be a smooth projective variety defined by homogeneous polynomials of degree $\leq d$ over an algebraically closed field. Let $\mathbf{Pic}\, X$ be the Picard scheme of $X$. Let $\mathbf{Pic}^0 X$ be the identity component of $\mathbf{Pic}\, X$. The N\'eron--Severi group scheme of $X$ is defined by $\mathbf{NS}\, X = (\mathbf{Pic}\, X)/(\mathbf{Pic}^0 X)_{\mathrm{red}}$. We give an explicit upper bound on the order of the finite group scheme $(\mathbf{NS}\, X)_{{\mathrm{tor}}}$ in terms of $d$ and $r$. As a corollary, we give an upper bound on the order of the finite group $\pi^1_{\mathrm{et}}(X,x_0)^{\mathrm{ab}}_{\mathrm{tor}}$. We also show that the torsion subgroup $(\mathrm{NS}\, X)_{\mathrm{tor}}$ of the N\'eron--Severi group of $X$ is generated by less than or equal to $(\mathrm{deg}\, X -1)(\mathrm{deg}\, X - 2)$ elements in various situations.
Structural phase transitions are governed by the underlying atomic transformation mechanism; martensitic transformations can be separated into strain and shuffle components. A systematic pathway generation and sorting algorithm is presented and applied to the problem of the titanium alpha to omega transformation under pressure. In this algorithm, all pathways are constructed within a few geometric limits, and efficiently sorted by their energy barriers. The geometry and symmetry details of the seven lowest energy barrier pathways are given. The lack of a single simple geometric criterion for determining the lowest energy pathway shows the necessity of atomistic studies for pathway determination.
Context: Effective temperature, surface gravity, and metallicity are basic spectroscopic stellar parameters necessary to characterize a star or a planetary system. Reliable atmospheric parameters for FGK stars have been obtained mostly from methods that relay on high resolution and high signal-to-noise optical spectroscopy. The advent of a new generation of high resolution near-IR spectrographs opens the possibility of using classic spectroscopic methods with high resolution and high signal-to-noise in the NIR spectral window. Aims: We aim to compile a new iron line list in the NIR from a solar spectrum to derive precise stellar atmospheric parameters, comparable to the ones already obtained from high resolution optical spectra. The spectral range covers 10 000 {\AA} to 25 000 {\AA}, which is equivalent to the Y, J, H, and K bands. Methods: Our spectroscopic analysis is based on the iron excitation and ionization balance done in LTE. We use a high resolution and high signal-to-noise ratio spectrum of the Sun from the Kitt Peak telescope as a starting point to compile the iron line list. The oscillator strengths (log gf) of the iron lines were calibrated for the Sun. The abundance analysis was done using the MOOG code after measuring equivalent widths of 357 solar iron lines. Results: We successfully derived stellar atmospheric parameters for the Sun. Furthermore, we analysed HD20010, a F8IV star, from which we derived stellar atmospheric parameters using the same line list as for the Sun. The spectrum was obtained from the CRIRES- POP database. The results are compatible with the ones found in the literature, confirming the reliability of our line list. However, due to the quality of the data we obtain large errors.
We propose a hole-induced mechanism of spin-polarized current generation by circularly polarized synchrotron radiation and corresponding induced magnetization in magnetically-doped topological insulators Bi$_{1.37}$V$_{0.03}$Sb$_{0.6}$Te$_2$Se. Considered spin-polarized current is generated due to the spin-dependent depopulation of the Dirac cone topological surface states at the Fermi level and subsequent compensation of the generated holes. We have found experimentally and theoretically a relation between the generated spin-polarized current and the shift of the electrochemical potential. The out-of-plane magnetization induced by circularly polarized synchrotron radiation and its inversion with switching the direction of circular polarization were experimentally shown and theoretically confirmed.
We present predictions of centimeter and millimeter radio emission from reverse shocks in the early afterglows of gamma-ray bursts with the goal of determining their detectability with current and future radio facilities. Using a range of GRB properties, such as peak optical brightness and time, isotropic equivalent gamma-ray energy and redshift, we simulate radio light curves in a framework generalized for any circumburst medium structure and including a parametrization of the shell thickness regime that is more realistic than the simple assumption of thick- or thin-shell approximations. Building on earlier work by Mundell et al. (2007) and Melandri et al. (2010) in which the typical frequency of the reverse shock was suggested to lie at radio, rather than optical wavelengths at early times, we show that the brightest and most distinct reverse-shock radio signatures are detectable up to 0.1 -- 1 day after the burst, emphasizing the need for rapid radio follow-up. Detection is easier for bursts with later optical peaks, high isotropic energies, lower circumburst medium densities, and at observing frequencies that are less prone to synchrotron self-absorption effects - typically above a few GHz. Given recent detections of polarized prompt gamma-ray and optical reverse-shock emission, we suggest that detection of polarized radio/mm emission will unambiguously confirm the presence of low-frequency reverse shocks at early time.
The ALMA Spectroscopic Survey in the Hubble Ultra Deep Field (ASPECS) provides new constraints for galaxy formation models on the molecular gas properties of galaxies. We compare results from ASPECS to predictions from two cosmological galaxy formation models: the IllustrisTNG hydrodynamical simulations and the Santa Cruz semi-analytic model (SC SAM). We explore several recipes to model the H$_2$ content of galaxies, finding them to be consistent with one another, and take into account the sensitivity limits and survey area of ASPECS. For a canonical CO-to-H$_2$ conversion factor of $\alpha_{\rm CO} = 3.6\,\rm{M}_\odot/(\rm{K}\,\rm{km/s}\,\rm{pc}^{2})$ the results of our work include: (1) the H$_2$ mass of $z>1$ galaxies predicted by the models as a function of their stellar mass is a factor of 2-3 lower than observed; (2) the models do not reproduce the number of H$_2$-rich ($M_{\rm H2} > 3\times 10^{10}\,\rm{M}_\odot$) galaxies observed by ASPECS; (3) the H$_2$ cosmic density evolution predicted by IllustrisTNG (the SC SAM) is in tension (only just agrees) with the observed cosmic density, even after accounting for the ASPECS selection function and field-to-field variance effects. The tension between models and observations at $z>1$ can be alleviated by adopting a CO-to-H$_2$ conversion factor in the range $\alpha_{\rm CO} = 2.0 - 0.8\,\rm{M}_\odot/(\rm{K}\,\rm{km/s}\,\rm{pc}^{2})$. Additional work on constraining the CO-to-H$_2$ conversion factor and CO excitation conditions of galaxies through observations and theory will be necessary to more robustly test the success of galaxy formation models.
This article gives a comprehensive review on the recent studies of the double exchange systems using non-perturbative approaches; the dynamical mean-field theory and the Monte Carlo method. Investigations beyond mean-field type treatments are described. Taking into account strong spin fluctuations which create large changes in conduction electron structure, finite temperature properties as well as dynamics of the system are calculated. Comparisons with experimental data for colossal magnetoresistance manganites are made. We show that high Curie temperature (Tc) compounds, e.g. (La,Sr)MnO3, are canonical double-exchange systems. Properties of other compounds with lower Tc are discussed in relation to inhomogeneities of the system including the issue of phase separation.
We analyze the gravitational radiation emitted from a particle in circular motion around a Schwarzschild black hole using the framework of quantum field theory in curved spacetime at tree level. The gravitational perturbations are written in a gauge-invariant formalism for spherically symmetric spacetimes. We discuss the results, comparing them to the radiation emitted by a particle when it is assumed to be orbiting a massive object due to a Newtonian force in flat spacetime.
We analyze quantization of noncommutative chiral electrodynamics in the enveloping algebra formalism in linear order in noncommutativity parameter $\theta$. Calculations show that divergences exist and cannot be removed by ordinary renormalization, however they can be removed by the Seiberg-Witten redefinition of fields. Performing the redefinitions explicitly, we obtain renormalizable lagrangian and discuss the influence of noncommutativity on field propagation. Noncommutativity affects the propagation of chiral fermions only: half of the fermionic modes become massive and birefringent.
The question of how infalling matter in a pure state forms a Schwarzschild black hole that appears to be at non-zero temperature is discussed in the context of the AdS/CFT connection. It is argued that the phenomenon of self-thermalization in non-linear (chaotic) systems can be invoked to explain how the boundary theory, initially at zero temperature self thermalizes and acquires a finite temperature. Yang-Mills theory is known to be chaotic (classically) and the imaginary part of the gluon self-energy (damping rate of the gluon plasma) is expected to give the Lyapunov exponent. We explain how the imaginary part would arise in the corresponding supergravity calculation due to absorption at the horizon of the black hole.
Let f be a degeneration of Kahler manifolds. The local invariant cycle theorem states that for a smooth fiber of the degeneration, any cohomology class, invariant under the monodromy action, rises from a global cohomology class. Instead of the classical cohomology, one may consider the non-abelian cohomology. This note demonstrates that the analogous non-abelian version of the local invariant cycle theorem does not hold if the first non-abelian cohomology is the moduli space (universal categorical quotient) of the representations of the fundamental group.
Character of the low-energy $E1$ excitations is investigated by analyzing transition densities obtained from the RPA calculations in the doubly-magic nuclei. We propose a decomposition method of the $E1$ excitations into the $pn$ mode (i.e. oscillation between protons and neutrons) and the skin mode (oscillation of the neutron skin against the inner core) via the transition densities, by which their mixing is handled in a straightforward manner. Crossover behavior of the $E1$ excitations is found, from the skin mode at low energy to the $pn$ mode at higher energy. The ratio of the skin-mode strength to the full strength turns out to be insensitive to nuclide and to effective interactions in the energy region of the crossover. Depending on the excitation energy, the observed low-energy $E1$ excitations are not necessarily dominated by the skin mode, as exemplified for $^{90}$Zr. fied for $^{90}$Zr.
We report on the implementation of a new interferometric scheme that allows the generation of photon pairs entangled in the time-energy degree of freedom. This scheme does not require any kind of temporal post-selection on the generated pairs and can be used even with lasers with short coherence time.
We propose an object detection method that improves the accuracy of the conventional SSD (Single Shot Multibox Detector), which is one of the top object detection algorithms in both aspects of accuracy and speed. The performance of a deep network is known to be improved as the number of feature maps increases. However, it is difficult to improve the performance by simply raising the number of feature maps. In this paper, we propose and analyze how to use feature maps effectively to improve the performance of the conventional SSD. The enhanced performance was obtained by changing the structure close to the classifier network, rather than growing layers close to the input data, e.g., by replacing VGGNet with ResNet. The proposed network is suitable for sharing the weights in the classifier networks, by which property, the training can be faster with better generalization power. For the Pascal VOC 2007 test set trained with VOC 2007 and VOC 2012 training sets, the proposed network with the input size of 300 x 300 achieved 78.5% mAP (mean average precision) at the speed of 35.0 FPS (frame per second), while the network with a 512 x 512 sized input achieved 80.8% mAP at 16.6 FPS using Nvidia Titan X GPU. The proposed network shows state-of-the-art mAP, which is better than those of the conventional SSD, YOLO, Faster-RCNN and RFCN. Also, it is faster than Faster-RCNN and RFCN.
We prove a general duality theorem for tangle-like dense objects in combinatorial structures such as graphs and matroids. This paper continues, and assumes familiarity with, the theory developed in [6]
We prove some regularity estimates for a class of convex functions in Carnot-Carath\'eodory spaces, generated by H\"ormander vector fields. Our approach relies on both the structure of metric balls induced by H\"ormander vector fields and local upper estimates for the corresponding subharmonic functions.
Here we examine the quantum-mechanical decay of a Schwarzschild-like black hole, formed by gravitational collapse, into almost-flat space-time and weak radiation at a very late time, in order to evaluate quantum amplitudes (not just probabilities) for final states. No information is lost in collapse to a black hole. Boundary data are specified on initial and final hypersurfaces $\Sigma_{I, F}$, separated by a Lorentzian proper-time interval $T$, as measured at spatial infinity. For simplicity, consider Einstein gravity coupled minimally to a massless scalar field $\phi$. In Lorentzian signature, the classical Dirichlet boundary-value problem, corresponding to specification of the intrinsic spatial metric $h_{ij} (i,j =1,2,3)$ and $\phi$ on the bounding surfaces, is badly posed, being a boundary-value problem for a wave-like (hyperbolic) set of equations. Following Feynman's $+i\epsilon$ prescription, the problem is made well-posed by rotating the asymptotic time interval $T$ into the complex: $T\to{\mid} T{\mid}\exp(-i\theta)$, with $0<\theta\leq\pi/2$. After calculating the amplitude for $\theta>0$, one takes the 'Lorentzian limit' $\theta\to 0_+$ to obtain the Lorentzian quantum amplitude.
The Gaia-ESO Survey is obtaining high-quality spectroscopic data for about 10^5 stars using FLAMES at the VLT. UVES high-resolution spectra are being collected for about 5000 FGK-type stars. These UVES spectra are analyzed in parallel by several state-of-the-art methodologies. Our aim is to present how these analyses were implemented, to discuss their results, and to describe how a final recommended parameter scale is defined. We also discuss the precision (method-to-method dispersion) and accuracy (biases with respect to the reference values) of the final parameters. These results are part of the Gaia-ESO 2nd internal release and will be part of its 1st public release of advanced data products. The final parameter scale is tied to the one defined by the Gaia benchmark stars, a set of stars with fundamental atmospheric parameters. A set of open and globular clusters is used to evaluate the physical soundness of the results. Each methodology is judged against the benchmark stars to define weights in three different regions of the parameter space. The final recommended results are the weighted-medians of those from the individual methods. The recommended results successfully reproduce the benchmark stars atmospheric parameters and the expected Teff-log g relation of the calibrating clusters. Atmospheric parameters and abundances have been determined for 1301 FGK-type stars observed with UVES. The median of the method-to-method dispersion of the atmospheric parameters is 55 K for Teff, 0.13 dex for log g, and 0.07 dex for [Fe/H]. Systematic biases are estimated to be between 50-100 K for Teff, 0.10-0.25 dex for log g, and 0.05-0.10 dex for [Fe/H]. Abundances for 24 elements were derived: C, N, O, Na, Mg, Al, Si, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Mo, Ba, Nd, and Eu. The typical method-to-method dispersion of the abundances varies between 0.10 and 0.20 dex.
Most of the chemical evolution models are not very reliable for the last 5~Gyr of galactic evolution; this is mainly because abundance gradients found in the literature show a big dispersion for young objects; a big culprit of this is the dispersion found in HII region gradients. Part of this dispersion arises from two different methods used to determine O/H in HII regions: the direct method (DM), based on forbidden lines; and the temperature independent method (TIM), based on permitted lines; the differences between these two methods are about 0.25~dex. We present two chemical evolution models of our galaxy to fit the O/H gradients of HII regions, one obtained from the DM and the other obtained from the TIM. We find that the model based on the TIM produces an excellent fit to the observational stellar constraints (B-stars, Cepheids, and the Sun), while the model based on the DM fails to reproduce them. Moreover the TIM model reproduces the flattening observed in the 3-6 kpc galactocentric range; this flattening is attained with an inside-out star formation quenching in the inner disk starting ~ 9 Gyr ago.
The angular power spectrum is a powerful statistic for analysing cosmological signals imprinted in the clustering of matter. However, current galaxy and quasar surveys cover limited portions of the sky, and are contaminated by systematics that can mimic cosmological signatures and jeopardise the interpretation of the measured power spectra. We provide a framework for obtaining unbiased estimates of the angular power spectra of large-scale structure surveys at the largest scales using quadratic estimators. The method is tested by analysing the 600 CMASS mock catalogues constructed by Manera et al. (2013) for the Baryon Oscillation Spectroscopic Survey (BOSS). We then consider the Richards et al. (2009) catalogue of photometric quasars from the Sixth Data Release (DR6) of the Sloan Digital Sky Survey (SDSS), which is known to include significant stellar contamination and systematic uncertainties. Focusing on the sample of ultraviolet-excess (UVX) sources, we show that the excess clustering power present on the largest-scales can be largely mitigated by making use of improved sky masks and projecting out the modes corresponding to the principal systematics. In particular, we find that the sample of objects with photometric redshift $1.3 < z_p < 2.2$ exhibits no evidence of contamination when using our most conservative mask and mode projection. This indicates that any residual systematics are well within the statistical uncertainties. We conclude that, using our approach, this sample can be used for cosmological studies.
We perform the point-splitting regularization on the vacuum stress tensor of a coupling scalar field in de Sitter space under the guidance from the adiabatically regularized Green's function. For the massive scalar field with the minimal coupling $\xi=0$, the 2nd order point-splitting regularization yields a finite vacuum stress tensor with a positive, constant energy density, which can be identified as the cosmological constant that drives de Sitter inflation. For the coupling $\xi\ne 0$, we find that, even if the regularized Green's function is continuous, UV and IR convergent, the point-splitting regularization does not automatically lead to an appropriate stress tensor. The coupling $\xi R$ causes log divergent terms, as well as higher-order finite terms which depend upon the path of the coincidence limit. After removing these unwanted terms by extra treatments, the 2nd-order regularization for small couplings $\xi \in(0,\frac{1}{7.04})$, and respectively the 0th-order regularization for the conformal coupling $\xi=\frac16$, yield a finite, constant vacuum stress tensor, in analogy to the case $\xi=0$. For the massless field with $\xi=0$ or $\xi=\frac16$, the point-splitting regularization yields a vanishing vacuum stress tensor, and there is no conformal trace anomaly for $\xi=\frac16$. If the 4th-order regularization were taken, the regularized energy density for general $\xi$ would be negative, which is inconsistent with the de Sitter inflation, and the regularized Green's function would be singular at the zero mass, which is unphysical. In all these cases, the stress tensor from the point-splitting regularization is equal to that from the adiabatic one.
HM Cancri is a candidate ultracompact binary white dwarf with an apparent orbital period of only 5.4 minutes, as suggested by X-ray and optical light-curve modulations on that period, and by the absence of longer-period variability. In this Letter we present Keck-I spectroscopy which shows clear modulation of the helium emission lines in both radial velocity and amplitude on the 5.4-minute period and no other. The data strongly suggest that the binary is emitting He I 4471 from the irradiated face of the cooler, less massive star, and He II 4686 from a ring around the more massive star. From their relative radial velocities, we measure a mass ratio q=0.50+/-0.13. We conclude that the observed 5.4-minute period almost certainly represents the orbital period of an interacting binary white dwarf. We thus confirm that HM Cnc is the shortest-period binary star known: a unique test for stellar evolution theory, and one of the strongest known sources of gravitational waves for the Laser Interferometer Space Antenna (LISA).