ShantanuT01/DACTYL-Pretraining huggingface dataset:
We propose an unsupervised method for 3D geometry-aware representation learning of articulated objects, in which no image-pose pairs or foreground masks are used for training. Though photorealistic images of articulated objects can be rendered with explicit pose control through existing 3D neural representations, these methods require ground truth 3D pose and foreground masks for training, which are expensive to obtain. We obviate this need by learning the representations with GAN training. The generator is trained to produce realistic images of articulated objects from random poses and latent vectors by adversarial training. To avoid a high computational cost for GAN training, we propose an efficient neural representation for articulated objects based on tri-planes and then present a GAN-based framework for its unsupervised training. Experiments demonstrate the efficiency of our method and show that GAN-based training enables the learning of controllable 3D representations without paired supervision.
We consider long-range percolation in dimension $d\geq 1$, where distinct sites $x$ and $y$ are connected with probability $p_{x,y}\in[0,1]$. Assuming that $p_{x,y}$ is translation invariant and that $p_{x,y}=\|x-y\|^{-s+o(1)}$ with $s>2d$, we show that the graph distance is at least linear with the Euclidean distance.
We compare ultraviolet (UV) and optical colors of a sample of 29 type Ia supernovae (SNe Ia) observed with the Swift satellite's UltraViolet Optical Telescope (UVOT) with theoretical models of an asymmetric explosion viewed from different angles from Kasen & Plewa. This includes mid-UV (1600-2700 Angstroms; uvw2 and uvm2) and near-UV (2700-4000 Angstroms; uvw1 and u) filters. We find the observed colors to be much redder than the model predictions, and that these offsets are unlikely to be caused by dust reddening. We confirm previous results that high-velocity SNe Ia have red UV-optical colors. When correcting the colors for dust reddening by assuming a constant b-v color we find no correlation between the uvw1-v or u-v colors and the ejecta velocities for 25 SNe Ia with published velocities and/or spectra. When assuming an optical color-velocity relation, a correlation of 2 and 3.6 sigma is found for uvw1-v and u-v. However, we find that the correlation is driven by the reddening correction and can be reproduced with random colors which are corrected for reddening. The significance of a correlation between the UV colors and the velocity is thus dependent on the assumed slope of the optical color-velocity relation. After such a correction, the uvw1-v versus velocity slope is shallower than that predicted by the models and offset to redder colors. A significant scatter still remains in the uvw1-v colors including a large spread at low velocities. This demonstrates that the NUV-blue/red spread is not caused solely by the photospheric velocity. The uvm2-uvw1 colors also show a large dispersion which is uncorrelated with the velocity.
The black-hole information paradox provides a stringent test of would-be theories of quantum gravity. String theory has made significant progress toward a resolution of this paradox, and has led to the fuzzball and microstate geometry programs. The central thesis of these programs is that only string theory has sufficiently many degrees of freedom to resolve black-hole microstructure, and that horizons and singularities are artifacts of attempting to describe gravity using a theory that has too few degrees of freedom to resolve the physics. Fuzzballs and microstate geometries recast black holes within string theory as horizonless and singularity-free objects that not only resolve the paradox but provide new insight into the underlying microstructure. We give an overview of this approach, summarize its current status and describe future prospects and insights that are now within reach.
We study by computer simulation distribution functions (DF) of mesoscopic hopping conductance. The DFs obtained for one-dimensional systems were found to be quite close to the predictions of the theory by Raikh and Ruzin. For D=2, the DFs both for narrow system and thin film look similar (and close to the 1D case).The distribution function for the conductance of the square sample is nearly Gaussian.
We study the dynamics of carriers in graphene subjected to an inhomogeneous magnetic field. For a magnetic field with an hyperbolic profile the corresponding Dirac equation can be analyzed within the formalism of supersymmetric quantum mechanics, and leads to an exactly solvable model. We study in detail the bound spectra. For a narrow barrier the spectra is characterized by a few bands, except for the zero energy level that remains degenerated. As, the width of the barrier increases we can track the bands evolution into the degenerated Landau levels. In the scattering regime a simple analytical formula is obtained for the transmission coefficient, this result allow us to identify the resonant conditions at which the barrier becomes transparent.
We present a detailed magnetic study of the triangular antiferromagnet ErMgGaO$_4$. A point charge calculation under the single ion approximation reveals a crystal field ground state doublet with a strong Ising-like behavior of the Er$^{3+}$ moment along the c axis. Magnetic susceptibility and specific heat measurements indicate no presence of magnetic transitions above 0.5~K and no evidence of residual entropy as temperature approaching zero. Zero field (ZF) $\mu$SR measurements shows no sign of static uniform or random field and longitudinal field (LF) $\mu$SR measurements exhibit persistent spin fluctuations down to our lowest temperature of 25~mK. Our results provide evidence of a quantum spin liquid state in the triangular antiferromagnet ErMgGaO$_4$.
The Euler-Poisson-Alignment (EPA) system appears in mathematical biology and is used to model, in a hydrodynamic limit, a set agents interacting through mutual attraction/repulsion as well as alignment forces. We consider one-dimensional EPA system with a class of singular alignment terms as well as natural attraction/repulsion terms. The singularity of the alignment kernel produces an interesting effect regularizing the solutions of the equation and leading to global regularity for wide range of initial data. This was recently observed in the paper by Do, Kiselev, Ryzhik and Tan. Our goal in this paper is to generalize the result and to incorporate the attractive/repulsive potential. We prove that global regularity persists for these more general models.
The goal of this article is to review the progress of three-electron spin qubits from their inception to the state of the art. We direct the main focus towards the resonant exchange (RX) qubit and the exchange-only qubit, but we also discuss other qubit implementations using three electron spins. For each three-spin qubit we describe the qubit model, the physical realization, the implementations of single-qubit operations, as well as the read-out and initialization schemes. Two-qubit gates and decoherence properties are discussed for the RX qubit and the exchange-only qubit, thereby, completing the list of requirements for a viable candidate qubit implementation for quantum computation. We start with describing the full system of three electrons in a triple quantum dot, then discuss the charge-stability diagram and restrict ourselves to the relevant subsystem, introduce the qubit states, and discuss important transitions to other charge states. Introducing the various qubit implementations, we begin with the exchange-only qubit, followed by the spin-charge qubit, the hybrid qubit, and the RX qubit, discussing for each the single-qubit operations, read-out, and initialization methods, whereas the main focus will be on the RX qubit, whose single-qubit operations are realized by driving the qubit at its resonant frequency in the microwave range similar to electron spin resonance. Two different types of two-qubit operations are presented for the exchange-only and the RX qubit which can be divided into short-ranged and long-ranged interactions. Both of these interaction types can be expected to be necessary in a large-scale quantum computer. We also take into account the decoherence of the qubit through the influence of magnetic noise as well as dephasing due to charge noise.
We calculate the oblique electroweak corrections and confront with the experiments in an extension of the Standard Model. The new fields added are a vector-like weak doublet and a singlet fermion. After electroweak symmetry breaking there is a mixing between the components of the new fields, but no mixing allowed with the standard fermions. Four electroweak parameters, $\hat{S}$, $\hat{T}$, W, Y are presented in the formalism of Barbieri et al., these are the generalization of the Peskin-Takeuchi S, T, U's. The vector-like extension is slightly constrained, $\hat{T}$ requires the new neutral fermion masses not to be very far from each other, allowing higher mass difference for higher masses and smaller mixing. $\hat{S}, W, Y$ gives practically no constraints on the masses. This extension can give a positive contribution to $\hat{T} $, allowing a heavy Higgs boson in electroweak precision tests of the Standard Model.
Pulsars are known to emit non-thermal radio emission that is generally a power-law function of frequency. In some cases, a turnover is seen at frequencies around 100~MHz. Kijak et al. have reported the presence of a new class of ''Gigahertz Peaked Spectrum'' (GPS) pulsars that show spectral turnovers at frequencies around 1 GHz. We apply a model based on free-free thermal absorption to explain these turnovers in terms of surrounding material such as the dense environments found in HII regions, Pulsar Wind Nebulae (PWNe), or in cold, partially ionized molecular clouds. We show that the turnover frequency depends on the electron temperature of the environment close to the pulsar, as well as the emission measure along the line of sight. We fitted this model to the radio fluxes of known GPS pulsars and show that it can replicate the GHz turnover. From the thermal absorption model, we demonstrate that normal pulsars would exhibit a GPS-like behaviour if they were in a dense environment. We discuss the application of this model in the context of determining the population of neutron stars within the central parsec of the Galaxy. We show that a non-negligible fraction of this population might exhibit high-frequency spectral turnovers, which has implications on the detectability of these sources in the Galactic centre.
The heat kernel expansion for field theory at finite temperature is constructed. It is based on the imaginary time formalism and applies to generic Klein-Gordon operators in flat space-time. Full gauge invariance is manifest at each order of the expansion and the Polyakov loop plays an important role at any temperature. The expansion is explicitly worked out up to operators of dimension six included. The method is then applied to compute the one loop effective action of QCD at finite temperature with massless quarks. The calculation is carried out within the background field method in the $\bar{\text{MS}}$ scheme up to dimension six operators. Further, the action of the dimensionally reduced effective theory at high temperature is also computed to the same order. Existing calculations are reproduced and new results are obtained in the quark sector for which only partial results existed up to dimension six.
Some combinatorial properties of fixed boundary rhombus random tilings with octagonal symmetry are studied. A geometrical analysis of their configuration space is given as well as a description in terms of discrete dynamical systems, thus generalizing previous results on the more restricted class of codimension-one tilings. In particular this method gives access to counting formulas, which are directly related to questions of entropy in these statistical systems. Methods and tools from the field of enumerative combinatorics are used.
We present all Petrov type D pure radiation space-times, with or without cosmological constant, with a shear-free, non-diverging geodesic principal null congruence.
We have used Monte Carlo simulation techniques to obtain the magnetic phase diagram of the double exchange Hamiltonian. We have found that the Berry's phase of the hopping amplitude has a negligible effect in the value of the magnetic critical temperature. To avoid finite size problems in our simulations we have also developed an approximated expression for the double exchange energy. This allows us to obtain the critical temperature for the ferromagnetic to paramagnetic transition more accurately. In our calculations we do not observe any strange behavior in the kinetic energy, chemical potential or electron density of states near the magnetic critical temperature. Therefore, we conclude that other effects, not included in the double exchange Hamiltonian, are needed to understand the metal-insulator transition which occurs in the manganites.
We have investigated the structure, kinematics, and emission spectrum of the ionized gas in the synchrotron superbubble in the irregular galaxy IC 10 based on observations with the 6-m Special Astrophysical Observatory telescope with the SCORPIO focal reducer in three modes: direct imaging in the [SII](6717+6731)A lines, long-slit spectroscopy, and spectroscopy with a scanning Fabry--Perot interferometer. We have identified a bright (in the [SII] lines) filamentary optical shell and determined its expansion velocity, mass, and kinetic energy. The nature of the object is discussed.
In a recent study by Dittmar and Dreiner it was shown that with appropriate selection cuts the signature of events containing two charged leptons and missing energy represents the best chance of detecting the Standard Model Higgs scalar in the mass range between 155 and 180 GeV, the primary decay of the Higgs being into pairs of charged gauge bosons. The largest background to this channel is due to irreducible $W^+W^-X$ production. In the present paper we calculate the contribution of events of the type $bg\to tW^\pm\to b W^+W^-\to b \ell^{+}\ell^{'-}\nu_\ell\bar\nu_{\ell'}$, which have not been considered yet within the new selection strategy. We show that the yield of this background is rather large, at the level of that produced by $W^+W^-$, $t\bar t$ or $tb W^\pm$ events and thus needs to be incorporated in future experimental analyses. However, we find that its inclusion will not spoil the possibilities of Higgs detection in the above mentioned channel at the Large Hadron Collider.
Recent XMM-Newton observations of the cooling flow gas in M87 indicate sharply decreasing oxygen, iron and silicon abundances within $\sim 5$ kpc of the galactic center. This result is unexpected since stellar mass loss and Type Ia supernovae are expected to produce pronounced central abundance maxima for all three elements. However, it has been suggested that many of the strong X-ray lines are optically thick and diffuse to larger radii in the cooling flow before escaping, falsifying the central abundances. We verify with radiation transfer calculations that this effect does indeed occur in the M87 cooling flow, but that it is insufficient to account for the M87 observations. We suggest that some source of continuous opacity is required to reduce the central X-ray line emission, perhaps by warm gas at $T \sim 10^5 - 10^6$ K. The radial surface brightness profiles of X-ray resonance lines are also sensitive to turbulence in cooling flows which reduces the line center optical depths considerably. Turbulence may provide sufficient energy to continuously heat the warm absorbing gas.
It is proved that the only additive and isotropic information measure that can depend on the probability distribution and also on its first derivative is a linear combination of the Boltzmann-Gibbs-Shannon and Fisher information measures. Power law equilibrium distributions are found as a result of the interaction of the two terms. The case of second order derivative dependence is investigated and a corresponding additive information measure is given.
We investigate energetic stability of vortices near the surface of a Bose-Einstein condensate. From an energy functional of a rotating Bose-Einstein condensate, written in terms of variables local to the surface, and a suitable trial wavefunction we calculate the energy of a moving vortex. The energetic stability of the vortex is investigated in terms of the rotation frequency of the confining potential. The critical frequency at which the vortices enter the condensate is calculated and compared with the experiment where a reasonable agreement is obtained.
Many-body correlations developed in the constrained molecular dynamics approach in the frame-work of the CoMD model are analyzed in the case of a finite range effective interaction. The study is performed in the case of infinite nuclear matter at zero temperature. A comparison with the predictions in the mean - field limit, which is taken as a reference case, highlights non-negligible differences concerning the produced Equation of State (EoS)for symmetric and asymmetric NM. A procedure is illustrated able to determine the necessary corrections of the effective interaction parameters in the CoMD model in such a way to reproduce the chosen reference EoS saturation properties. Even if the obtained numerical results are strictly valid for the CoMD model, the rather general feature of the discussed correlations gives a wider meaning to the obtained differences which are strongly related to the nucleon wave function space localization characterizing every semi-classical quantum molecular dynamics approach. Finally, the relevance of the constraint on the primary light cluster production is shortly illustrated in an appendix section.
The Kida's formula in classical Iwasawa theory relates the Iwasawa $\lambda$-invariants of $p$-extensions of number fields. Analogue of this formula was subsequently established for the Iwasawa $\lambda$-invariants of Selmer groups under an appropriate $\mu=0$ assumption. In this paper, we give a conceptual (but conjectural) explanation that such a formula should also hold when $\mu\neq 0$. The conjectural component comes from the so-called $\mathfrak{M}_H(G)$-conjecture in noncommutative Iwasawa theory.
The effects of spin-orbit coupling on the two-electron spectra in lateral coupled quantum dots are investigated analytically and numerically. It is demonstrated that in the absence of magnetic field the exchange interaction is practically unaffected by spin-orbit coupling, for any interdot coupling, boosting prospects for spin-based quantum computing. The anisotropic exchange appears at finite magnetic fields. A numerically accurate effective spin Hamiltonian for modeling spin-orbit-induced two-electron spin dynamics in the presence of magnetic field is proposed.
The deceptive simplicity of the radius enclosing an arbitrary 50 percent of a galaxy's light has hamstrung the understanding of early-type galaxies (ETGs). Half a century ago, using the "effective half-light radii" $R_e$ from de Vaucouleurs' $R^{1/4}$ model, S\'ersic reported that bright ETGs follow the relation $\mathfrak{M}_B\propto2.5\log R_e$; and consequently one has that $\langle\mu\rangle_e\propto2.5\log R_e$ and $\mu_e\propto2.5\log R_e$, where $\mu_e$ and $\langle\mu\rangle_e$ are the effective surface brightness at $R_e$ and the mean effective surface brightness within $R_e$, respectively. S\'ersic additionally observed an apparent transition which led him to advocate for a division between what he called dwarf and giant ETGs; a belief frequently restated to occur at $\mathfrak{M}_B\approx-18$ mag or S\'ersic $n\approx 2.5$. Here, the location of this false dichotomy is shown to change by more than 3 mag simply depending on the arbitrary percentage of light used to quantify a galaxy's size, voiding claims for different formation physics operating on ETGs brighter and fainter than $\mathfrak{M}_B\approx-18$ mag. This is of further importance because quantities such as dynamical mass $\sigma^2R/G$, gravitational binding energy $GM^2/R$, acceleration $GM/R^2$, and the "Fundamental Plane" depend systematically on the arbitrary percentage of light used to define $R$, with implications for dark matter estimates, galaxy formation theories, compact massive galaxies, studies of peculiar velocity flows, and more. Finally, some of the vast literature which has advocated for segregating the ETG population at $\mathfrak{M}_B\approx-18$ mag ($M\approx1$-$2\times10^{10}\,M_{\odot}$) is addressed, and it is revealed how this pervasive mindset has spilled-over to influence both the classical bulge versus pseudobulge debate and recently also correlations involving supermassive black hole masses.
The classical criterion of Jensen for the Riemann hypothesis is that all of the associated Jensen polynomials have only real zeros. We find a new version of this criterion, using linear combinations of Hermite polynomials, and show that this condition holds in many cases. Detailed asymptotic expansions are given for the required Taylor coefficients of the xi function at $1/2$ as well as related quantities. These results build on those in the recent paper of Griffin, Ono, Rolen and Zagier.
Charged pion photoproduction is proposed as a new method to study halo nuclei. In particular, it is demonstrated that the reaction 17O(gamma,pi^-)17F(1/2+, 0.495 MeV) is well-suited to investigate the well-known proton halo in 17F which is not amenable to radioactive beam experiments. The cross sections are shown to be very sensitive to the halo structure of the loosely bound proton.
We show how the Majorana representation can be used to express the pure states of an N-qubit system as points on the Bloch sphere. We compare this geometrical representation of N-qubit states with an alternative one, proposed recently by the present authors.
Numerous non-standard dynamics are described by contact-like effective interactions that can manifest themselves through deviations of the cross sections from the Standard Model predictions. If one such deviation were observed, one should try to identify to a given confidence level the actual source among the possible non-standard interactions that in principle can explain it. We here estimate the potential identification reach on different New Physics effective interactions, obtainable from the angular distributions of lepton pair production processes at the planned International Linear Collider with polarized beams. The models discussed are the interactions based on gravity in large and in TeV^{-1} extra dimensions and the compositeness-inspired four-fermion contact interactions. The availability of both beams polarized in many cases plays an essential role in enhancing the identification sensitivity.
We consider the Gelfand problem in a bounded smooth domain $\Omega\subset \mathbb{R}^N$ with the Dirichlet boundary condition. We are interested in the boundedness of the extremal solution $u^*$. When the dimension $N\ge10$, it is known that a singular extremal solution can be constructed for the nonlinearity $f(u)=e^u$ and $\Omega=B_1$. When $3\le N\le 9$, Cabr\'e, Figalli, Ros-Oton, and Serra (2020) proved the following surprising result: the extremal solution $u^*$ is bounded if the nonlinearity $f$ is positive, nondecreasing, and convex.   In this paper, we succeed in generalizing their result to general $m$-convex nonlinearities. Moreover, we give a unified viewpoint on the results of previous studies by considering $m$-convexity. We provide a closedness result for stable solutions with $m$-convex nonlinearities. As a consequence, we provide a Liouville-type result and by using a blow-up argument, we prove the boundedness of extremal solutions.