ShantanuT01/DACTYL-Pretraining huggingface dataset:
Accuracy and processing speed are two important factors that affect the use of video object segmentation (VOS) in real applications. With the advanced techniques of deep neural networks, the accuracy has been significantly improved, however, the speed is still far below the real-time needs because of the complicated network design, such as the requirement of the first frame fine-tuning step. To overcome this limitation, we propose a novel mask transfer network (MTN), which can greatly boost the processing speed of VOS and also achieve a reasonable accuracy. The basic idea of MTN is to transfer the reference mask to the target frame via an efficient global pixel matching strategy. The global pixel matching between the reference frame and the target frame is to ensure good matching results. To enhance the matching speed, we perform the matching on a downsampled feature map with 1/32 of the original frame size. At the same time, to preserve the detailed mask information in such a small feature map, a mask network is designed to encode the annotated mask information with 512 channels. Finally, an efficient feature warping method is used to transfer the encoded reference mask to the target frame. Based on this design, our method avoids the fine-tuning step on the first frame and does not rely on the temporal cues and particular object categories. Therefore, it runs very fast and can be conveniently trained only with images, as well as being robust to unseen objects. Experiments on the DAVIS datasets demonstrate that MTN can achieve a speed of 37 fps, and also shows a competitive accuracy in comparison to the state-of-the-art methods.
Dans cette note, nous montrons que certaines formes modulaires de Siegel de caract\'eristique p et de genre 2 ou 3 se rel\`event en caract\'eristique 0. Ce r\'esultat g\'en\'eralise un th\'eor\`eme classique obtenu par Katz pour les formes de genre 1. Nous utilisons des r\'esultats de Shepherd-Barron et de Hulek et Sankaran, ainsi que des th\'eor\`emes d'annulation de la cohomologie coh\'erente d\^us \`a Deligne, Illusie et Raynaud et \`a Esnault et Viehweg.   -----   In this note, we show that cuspidal Siegel modular forms of characteristic p and genus 2 or 3 can be lifted to characteristic 0. This result extends a classical theorem proved by Katz for genus 1 modular forms. We use ampleness results due to Shepherd-Barron, Hulek and Sankaran, and vanishing theorems due to Deligne, Illusie, Raynaud, Esnault and Viehweg.
In this work, we try to use the apparent luminosity versus displacement (i.e., $L_{\rm X}$ vs. $R$) correlation of high mass X-ray binaries (HMXBs) to constrain the common envelope (CE) efficiency $\alpha_{\rm CE}$, which is a key parameter affecting the evolution of the binary orbit during the CE phase. The major updates that crucial for the CE evolution include a variable $\lambda$ parameter and a new CE criterion for Hertzsprung gap donor stars, both of which are recently developed. We find that, within the framework of the standard energy formula for CE and core definition at mass $X=10$\%, a high value of $\alpha_{\rm CE}$, i.e., around 0.8-1.0, is more preferable, while $\alpha_{\rm CE}< \sim 0.4$ likely can not reconstruct the observed $L_{\rm X}$ vs. $R$ distribution. However due to an ambiguous definition for the core boundary in the literature, the used $\lambda$ here still carries almost two order of magnitude uncertainty, which may translate directly to the expected value of $\alpha_{\rm CE}$. We present the detailed components of current HMXBs and their spatial offsets from star clusters, which may be further testified by future observations of HMXB populations in nearby star-forming galaxies.
N-body simulations predict that dark matter halos with different mass scales are described by a universal model, the Navarro-Frenk-White (NFW) density profiles. As a consequence of baryonic cooling effects, the halos will become more concentrated, and similar to an isothermal sphere over large range in radii ($\sim 300$ $h^{-1}$kpc). The singular isothermal sphere model however has to be truncated artificially at large radii since it extends to infinity. We model a massive galaxy halo as a combination of an isothermal sphere and an NFW density profile. We give an approximation for the mass concentration at different baryon fractions and present exact expressions for the weak lensing shear and flexion for such a halo. We compare the lensing properties with a Singular Isothermal Sphere and NFW profiles. We find that the combined profile can generate higher order lensing signals at small radii and is more efficient in generating strong lensing events. In order to distinguish such a halo profile from the SIS or NFW profiles, one needs to combine strong and weak lensing constraints on small and large radii.
We study topological properties of phase transition points of one-dimensional topological quantum phase transitions by assigning winding numbers defined on closed circles around the gap closing points in the parameter space of momentum and a transition driving parameter, which overcomes the problem of ill definition of winding numbers on the transition points. By applying our scheme to the extended Kitaev model and extended Su-Schrieffer-Heeger model, we demonstrate that the topological phase transition can be well characterized by winding numbers of transition points, which reflect the change of the winding number of topologically different phases across the phase transition points.
Using holographic models where chiral symmetry is broken through IR b.c.'s, we determine a novel set of relations between QCD matrix elements. In particular, we find that the amplitudes of the three processes pi pi->pi pi, gamma gamma->pi pi and gamma->pi pi pi involve a single scalar function h(Q^2) given by a suitable 5D integral of the EoM Green's function. In a phenomenological analysis of gamma gamma->pi pi we find an overall agreement with the experimental cross section for a broad range of energy. Moreover, the polarizabilities at low energies show a fair agreement between the holographic approach, previous computations and experiment.
Recently, Jel\'{i}nek derived that the number of self-dual interval orders of reduced size $n$ is twice the number of row-Fishburn matrices of size $n$ by using generating functions. In this paper, we present a bijective proof of this relation by establishing a bijection between two variations of upper-triangular matrices of nonnegative integers. Using the bijection, we provide a combinatorial proof of the refined relations between self-dual Fishburn matrices and row-Fishburn matrices in answer to a problem proposed by Jel\'{i}nek.
A hot corona is suggested to be above the standard thin disk. The anisotropy of hard X-ray emission in radio-quiet active galactic nuclei implies that the corona is not static and probably moves outwards like winds. We perform two-dimensional magnetohydrodynamical simulations to study the outflowing corona driven by magnetic field and radiation force. In our simulations, as the initial state and the boundary condition at the disk surface, the corona temperature is set to $10^9$ K inside 10 Schwarzschild radius ($r_{\rm s}$) while the corona temperature is set to $10^7$ K a 10 $r_{\rm s}$. We employ a weak poloidal magnetic field as the initial magnetic field. A collimated outflow and a wide-angle ordered outflow are observed in our simulations. The collimated outflow is around the rotational axis and has a bulk velocity of $\sim$0.03--0.3 $c$ ( $c$ is speed of light) at 90 $r_{\rm s}$, while their mass outflow rate is very low. The collimated outflow is a weak jet. The wide-angle ordered outflow is distributed at the middle and high latitudes and moves outwards with a velocity of $10^2$--$10^4$ km s$^{-1}$. The outflow velocity depends on the disk luminosity. The gas around the disk surface is turbulent, especially outside of 10 $r_{\rm s}$. The other properties of outflows are discussed in detail.
This paper is concerned with a class of singular stable-like Dirichlet forms on $\R^d$, which are generated by $d$ independent copies of a one-dimensional symmetric $\alpha$-stable process, and whose L\'evy jump kernel measure is concentrated on the union of the coordinate axes. Explicit and sharp criteria for Poincar\'e inequality, super Poincar\'e inequality and weak Poincar\'e inequality of such singular Dirichlet forms are presented. When the reference measure is a product measure on $\R^d$, we also consider the entropy inequality for the associated Dirichlet forms, which is similar to the log-Sobolev inequality for local Dirichlet forms, and enjoys the tensorisation property.
We include the brane curvature scalar to study its cosmological implication in the brane world cosmology. This term is usually introduced to obtain the well-defined stress-energy tensor on the boundary of anti de Sitter-Schwarzschild space. Here we treat this as the perturbed term for cosmological purpose. We find corrections to the well-known equation of the brane cosmology. It contains new interesting terms which may play the important role in the brane cosmology.
The first-order correlation function, which is accessible experimentally, contains all essential information about the state of the system of non-interacting electrons. Here I discuss how this function can be used to answer the question whether the state of a periodic stream of single-electron wave-packets is a multi-particle state or it is the product of single-particle states. In the latter case the correlation function is expected to be factorizable while in the former case it is not. As an example I consider a train of Lorentzian in shape single-electron excitations, levitons. I demonstrate that the correlation function in time domain is factorizable or not depending on whether the wave-packets are separated or overlapping. In contrast, the correlation function in energy domain is always factorizable and thus cannot be used to distinguish single- and multi-particle states.
We compute the number of circuits and of loops with multiple crossings in random regular graphs. We discuss the importance of this issue for the validity of the cavity approach. On the one side we obtain analytic results for the infinite volume limit in agreement with existing exact results. On the other side we implement a counting algorithm, enumerate circuits at finite N and draw some general conclusions about the finite N behavior of the circuits.
The temperature dependences of the total, crystal lattice and electronic thermal conductivities were investigated in films of topological insulators p-Bi$_{0.5}$Sb$_{1.5}$Te$_{3}$ and p-Bi$_{2}$Te$_{3}$ formed by discrete and thermal evaporation methods. The largest decrease in the lattice thermal conductivity owing to the scattering of long-wavelength phonons on the grain interfaces was observed in the films of solid solutions p-Bi$_{0.5}$Sb$_{1.5}$Te$_{3}$ deposited by discrete evaporation on the amorphous substrates of polyimide without thermal treatment. It is shown that in the p-Bi$_{0.5}$Sb$_{1.5}$Te$_{3}$ films with low thermal conductivity the energy dependence of the relaxation time is enhanced, which is specific for the topological insulators. The electronic thermal conductivity was determined taking into account the effective scattering parameter in the relaxation time approximation versus energy in the Lorentz number calculations. The observed increase of the electronic thermal conductivity within the temperature range of 40 - 80 K is related to the weakening of the electrical conductivity temperature dependence and is determined by the increase in the effective scattering parameter at low temperatures due to the effect of scattering on the point antisite and impurity defects. A correlation was established between the thermal conductivity and features of the morphology of the interlayer surface (0001) in the studied films.
We examine the maximum possible strength of the global 21-cm absorption dip on the Cosmic Background Radiation at high-redshift caused by the atomic intergalactic medium, when the Lyman-$\alpha$ coupling is maximum, assuming no exotic cooling mechanisms from interactions with dark matter. This maximum absorption is limited by three inevitable factors that need to be accounted for: $(a)$ heating by energy transferred from the Cosmic Background Radiation to the hydrogen atoms via 21-cm transitions, dubbed as 21-cm heating; $(b)$ Ly$\alpha$ heating by scatterings of Ly$\alpha$ photons from the first stars; $(c)$ the impact of the expected density fluctuations in the intergalactic gas in standard Cold Dark Matter theory, which reduces the mean 21-cm absorption signal. Inclusion of this third novel effect reduces the maximum global 21-cm absorption by $\sim 10\%$. Overall, the three effects studied here reduce the 21-cm global absorption by $\sim 20\%$ at $z \simeq 17$.
The Open Cluster Chemical Abundances and Mapping (OCCAM) survey aims to constrain key Galactic dynamical and chemical evolution parameters by the construction of a large, comprehensive, uniform, infrared-based spectroscopic data set of hundreds of open clusters. This fourth contribution from the OCCAM survey presents analysis using SDSS/APOGEE DR16 of a sample of 128 open clusters, 71 of which we designate to be "high quality" based on the appearance of their color-magnitude diagram. We find the APOGEE DR16 derived [Fe/H] abundances to be in good agreement with previous high resolution spectroscopic open cluster abundance studies. Using the high quality sample, we measure Galactic abundance gradients in 16 elements, and find evolution of some of the [X/Fe] gradients as a function of age. We find an overall Galactic [Fe/H] vs R_GC gradient of $-0.068 \pm 0.001$ dex kpc$^{-1}$ over the range of $6 <$ R_GC $< 13.9$ kpc; however, we note that this result is sensitive to the distance catalog used, varying as much as 15%. We formally derive the location a break in the [Fe/H] abundance gradient as a free parameter in the gradient fit for the first time. We also measure significant Galactic gradients in O, Mg, S, Ca, Mn, Cr, Cu, Na, Al, and K, some of which are measured for the first time. Our large sample allows us to explore four well-populated age bins to explore the time evolution of gradients for a large number of elements and comment on possible implications for Galactic chemical evolution and radial migration.
As one of the basic components of phononics, thermal diodes transmit heat current asymmetrically similar to electronic rectifiers and diodes in microelectronics. Heat can be conducted through them easily in one direction while being blocked in the other direction. In this work, we report an easily-fabricated mesoscale chemical vapor deposited (CVD) diamond thermal diode without sharp temperature change driven by the gradient grain structure of CVD diamond membranes. We build a spectral model of diamond thermal conductivity with complete phonon dispersion relation to show significant thermal rectification in CVD diamond membranes. To explain the observed thermal rectification, the temperature and thermal conductivity distribution in the CVD diamond membrane are studied. Additionally, the effects of temperature bias and diamond membrane thickness are discussed, which shed light on tuning the thermal rectification in CVD diamond membranes. The conical grain structure makes CVD diamond membranes, and potentially other CVD film structures with gradient grain structure, excellent candidates for easily-fabricated mesoscale thermal diodes without a sharp temperature change.
Throughout the paper, an analytic field means a non-archimedean complete real-valued one, and our main objective is to extend to these fields the basic theory of transcendental extensions. One easily introduces a topological analogue of the transcendence degree, but, surprisingly, it turns out that it may behave very badly. For example, a particular case of a theorem of Matignon-Reversat asserts that if $\mathrm{char}(k)>0$ then $\widehat{k((t))^a}$ possesses non-invertible continuous $k$-endomorphisms, and this implies that the topological transcendence degree is not additive in towers. Nevertheless, we prove that in some aspects the topological transcendence degree behaves reasonably, and we show by explicit counter-examples that our positive results are pretty sharp. Applications to types of points in Berkovich spaces and untilts of $\widehat{\mathbf{F}_p((t))^a}$ are discussed.
Soft biometric modalities have shown their utility in different applications including reducing the search space significantly. This leads to improved recognition performance, reduced computation time, and faster processing of test samples. Some common soft biometric modalities are ethnicity, gender, age, hair color, iris color, presence of facial hair or moles, and markers. This research focuses on performing ethnicity and gender classification on iris images. We present a novel supervised autoencoder based approach, Deep Class-Encoder, which uses class labels to learn discriminative representation for the given sample by mapping the learned feature vector to its label. The proposed model is evaluated on two datasets each for ethnicity and gender classification. The results obtained using the proposed Deep Class-Encoder demonstrate its effectiveness in comparison to existing approaches and state-of-the-art methods.
It is shown that the large $N$ limit of SU(N) YM in $curved$ $m$-dim backgrounds can be subsumed by a higher $m+n$ dimensional gravitational theory which can be identified to an $m$-dim generally invariant gauge theory of diffs $N$, where $N$ is an $n$-dim internal space (Cho, Sho, Park, Yoon). Based on these findings, a very plausible geometrical interpretation of the $AdS/CFT$ correspondence could be given. Conformally invariant sigma models in $D=2n$ dimensions with target non-compact SO(2n,1) groups are reviewed. Despite the non-compact nature of the SO(2n,1), the classical action and Hamiltonian are positive definite. Instanton field configurations are found to correspond geometrically to conformal ``stereographic'' mappings of $R^{2n}$ into the Euclidean signature $AdS_{2n}$ spaces. The relation between Self Dual branes and Chern-Simons branes, High Dimensional Knots, follows. A detailed discussion on $W_\infty $ symmetry is given and we outline the Vasiliev procedure to construct an action involving higher spin massless fields in $AdS_4$. This $AdS_4$ spacetime higher spin theory should have a one-to-one correspondence to noncritical $W_\infty$ strings propagating on $AdS_4 \times S^7$.
Compact stars made of quark matter rather than confined hadronic matter, are expected to form a color superconductor. This superconductor ought to be threaded with rotational vortex lines within which the star's interior magnetic field is confined. The vortices (and thus magnetic flux) would be expelled from the star during stellar spin-down, leading to magnetic reconnection at the surface of the star and the prolific production of thermal energy. In this Letter, we show that this energy release can re-heat quark stars to exceptionally high temperatures, such as observed for Soft Gamma Repeaters (SGRs), Anomalous X-Ray pulsars (AXPs), and X-ray dim isolated neutron stars (XDINs). Moreover, our numerical investigations of the temperature evolution, spin-down rate, and magnetic field behavior of such superconducting quark stars suggest that SGRs, AXPs, and XDINs may be linked ancestrally. Finally, we discuss the possibility of a time delay before the star enters the color superconducting phase, which can be used to estimate the density at which quarks deconfine. We find this density to be five times that of nuclear saturation.
In the first part of this work the classical and statistical aspects of the dynamics of an inextensible chain in three dimensions are investigated. In the second part the special case of a chain admitting only fixed angles with respect to the $z-$axis is studied using a path integral approach. It is shown that it is possible to reduce this problem to a two-dimensional case, in a way which is similar to the reduction of the statistical mechanics of a directed polymer to the random walk of a two-dimensional particle.
The electronic band structure of iron pnictides exhibits four Dirac cones, which are due to crystal symmetry and orbital bonding orientation. This hallmark signature presents the pnictide family as an ideal candidate in the search for quasi-two-dimensional topological crystalline insulators. In this report, we explore interaction-induced topological phases which cannot be described by conventional local order parameters. Based on a model Hamiltonian our symmetry analysis shows that sponta- neous novel topological phases may be realized in compounds with tetragonal crystal field symmetry, where the electrons occupy the two degenerate t2g energy levels at low temperature. We identify two stable topological phases in the ground state, which emerge from spontaneous orbital current order. These currents are driven by electronic correlations caused by inter-orbital Coulomb interactions. The first topological phase is an anomalous orbital Hall phase, characterized by a nonzero Chern number, while the second topological phase has a vanishing Chern number, though with an extra Z2-like invariant that preserves parity. More specifically, the interaction-induced novel phase of the quasi-two-dimensional topological crystalline insulator is protected by mirror reflection symmetries and therefore may be realized in pnictides.
We investigate the properties of standing waves to a nonlinear Schr\"odinger equation with inverse-square potential on the half-line. We first establish the existence of standing waves. Then, by a variational characterization of the ground states, we establish the orbital stability of standing waves for mass sub-critical nonlinearity. Owing to the non-compactness and the absence of translational invariance of the problem, we apply a profile decomposition argument. We obtain convergent minimizing sequences by comparing the problem to the problem at "infinity" (i.e., the equation without inverse square potential). Finally, we establish orbital instability by a blow-up argument for mass super-critical nonlinearity.
We developed a parametrization of transmission probability that reliably captures essential elements of the tunneling process in magnetic tunnel junctions. The electronic structure of Fe/MgO system is calculated within the quasiparticle self-consistent GW approximation and used to evaluate transmission probability across (001) Fe/MgO interface. The transmission has a peak at +0.12 V, in excellent agreement with recent differential conductance measurements for electrodes with antiparallel spin. These findings confirm that the observed current-voltage characteristics are intrinsic to well defined (001) Fe/MgO interfaces, in contrast to previous predictions based on the local spin-density approximation, and also that many-body effects are important to realistically describe electron transport across well defined metal-insulator interfaces.
The annihilation of dark matter (DM) particles in the Milky Way can contribute to the diffuse gamma-ray background (DGRB). Due to the presence of substructures, this emission will appear anisotropic in a predictable way. We generate full-sky maps of the gamma-ray emission in galactic substructures from results of the high-resolution Via Lactea II N-body simulation of the Milky Way DM halo. We calculate the anisotropy pattern, taking into account different radial profiles of the DM distribution in substructures, cosmic variance, and the detection threshold, and compare it to the anisotropy in the DGRB observed by the Fermi Large Area Telescope (LAT). By comparing the upper limits on the DM self-annihilation cross-section, <$\sigma v$>, implied by the anisotropy to the intensity of the DGRB and detected sources in the LAT 2-yr Point Source Catalog, we find that galactic substructure cannot contribute to the anisotropies in the DGRB without strongly violating these observations. Our results challenge the perception that small-scale anisotropies in the DGRB can be used as a probe of DM annihilation in galactic subhaloes.