ShantanuT01/DACTYL-Pretraining huggingface dataset:
Aims.We study the photometric and structural properties of the star cluster system in the late type Sc spiral NGC 3370. Methods. BVI observations from the Advanced Camera for Surveys on board of HST are used to analyse in detail the colours, magnitudes and spatial properties of cluster candidates. The final catalogue of sources used for the study is composed by 277 objects. Results. The colour distributions of cluster candidates appear multi-modal. Although firm age constraints need the use of more age sensitive indicators, the comparison of cluster candidate colours with the colours of Galactic and Magellanic Clouds star clusters, suggests an age difference between the various sub-peaks, with a red old sub-system, a rich population of intermediate age (~1 Gyr), and a blue tail of very young (below ~100 Myr) clusters. The luminosity functions appear normal for this type of galaxy, as for the distribution of cluster effective radii (Reff). Our analysis suggests the presence of a peak in the Reff distribution at ~3.0 pc, with blue (likely young) cluster candidates showing smaller radii respect to red (likely old) objects. Finally, inspecting the properties of candidate globular clusters, we find a colour distribution matching with Galactic Globulars, with a median [Fe/H] -1.5 dex, though a non negligible tail towards lower metallicities is also present.
We present 2-9 GHz radio observations of GW170817 covering the period 125-200 days post-merger, taken with the Australia Telescope Compact Array and the Karl G. Jansky Very Large Array. Our observations demonstrate that the radio afterglow peaked at $149\pm2$ days post-merger and is now declining in flux density. We see no evidence for evolution in the radio-only spectral index, which remains consistent with optically-thin synchrotron emission connecting the radio, optical, and X-ray regimes. The peak implies a total energy in the synchrotron-emitting component of a ${\rm few}\times 10^{50}\,$erg. The temporal decay rate is most consistent with mildly- or non-relativistic material and we do not see evidence for a very energetic off-axis jet, but we cannot distinguish between a lower-energy jet and more isotropic emission.
We have constructed a broad-band spectrum for GRB 930131 (the ``Superbowl Burst''), ranging from 20 keV to 200 MeV, by combining spectral information from the Gamma Ray Observatory's BATSE, COMPTEL and EGRET instruments. We present general methods for combining spectra from different time intervals obtained by the same instrument as well as for combining spectra from the same time interval taken by different instruments. The resulting spectrum is remarkably flat (in nu F_nu-space) up to high energies. We find that the spectral shape can be successfully fitted by the shocked synchrotron emission model of Tavani. We present evidence that the flatness of the spectrum at high energies is not due to spectral time-variability.
We have conducted ALMA observations in the 1.3 mm continuum and 12CO (2-1), C18O (2-1) and SO (5_6-4_5) lines toward L1489 IRS, a Class I protostar surrounded by a Keplerian disk and an infalling envelope. The Keplerian disk is clearly identified in the 12CO and C18O emission, and its outer radius (~700 AU) and mass (~0.005 Msun) are comparable to those of disks around T Tauri stars. The protostellar mass is estimated to be 1.6 Msun with the inclination angle of 66 deg. In addition to the Keplerian disk, there are blueshifted and redshifted off-axis protrusions seen in the C18O emission pointing toward the north and the south, respectively, adjunct to the middle part of the Keplerian disk. The shape and kinematics of these protrusions can be interpreted as streams of infalling flows with a conserved angular momentum following parabolic trajectories toward the Keplerian disk, and the mass infalling rate is estimated to be ~5E-7 Msun/yr. The specific angular momentum of the infalling flows (~2.5E-3 km/s*pc) is comparable to that at the outer radius of the Keplerian disk (~4.8E-3 km/s*pc). The SO emission is elongated along the disk major axis and exhibits a linear velocity gradient along the axis, which is interpreted as that the SO emission primarily traces a ring region in the flared Keplerian disk at radii of ~250-390 AU. The local enhancement of the SO abundance in the ring region can be due to the accretion shocks at the centrifugal radius where the infalling flows fall onto the disk. Our ALMA observations unveiled both the Keplerian disk and the infalling gas onto the disk, and the disk can further grow by accreting material and angular momenta from the infalling gas.
Co-occurrent visual pattern makes context aggregation become an essential paradigm for semantic segmentation.The existing studies focus on modeling the contexts within image while neglecting the valuable semantics of the corresponding category beyond image. To this end, we propose a novel soft mining contextual information beyond image paradigm named MCIBI++ to further boost the pixel-level representations. Specifically, we first set up a dynamically updated memory module to store the dataset-level distribution information of various categories and then leverage the information to yield the dataset-level category representations during network forward. After that, we generate a class probability distribution for each pixel representation and conduct the dataset-level context aggregation with the class probability distribution as weights. Finally, the original pixel representations are augmented with the aggregated dataset-level and the conventional image-level contextual information. Moreover, in the inference phase, we additionally design a coarse-to-fine iterative inference strategy to further boost the segmentation results. MCIBI++ can be effortlessly incorporated into the existing segmentation frameworks and bring consistent performance improvements. Also, MCIBI++ can be extended into the video semantic segmentation framework with considerable improvements over the baseline. Equipped with MCIBI++, we achieved the state-of-the-art performance on seven challenging image or video semantic segmentation benchmarks.
It is a well-known fact that the optimal POVM for quantum state tomography is the symmetric, informationally complete, positive operator valued measure (SIC-POVM). We investigate the same problem only in the case when there are some a priori information about the state, specifically when some parameters are known. In this paper we mainly focus on solving a 3-dimensional optimization problem, which gives us a non-trivial example for the so-called conditional SIC- POVMs, a straightforward generalization of the concept of SIC-POVMs. We also present other special cases to show further applications of the proposed numerical methods and to illustrate the complexity of this topic.
Plane quartics containing the ten vertices of a complete pentalateral and limits of them are called L\"uroth quartics. The locus of singular L\"uroth quartics has two irreducible components, both of codimension two in $\P^{14}$. We compute the degree of them and we discuss the consequences of this computation on the explicit form of the L\"uroth invariant. One important tool are the Cremona hexahedral equations of the cubic surface. We also compute the class in $\overline{M}_3$ of the closure of the locus of nonsingular L\"uroth quartics.
The Angstrom Project is using a global network of 2m-class telescopes to conduct a high cadence pixel microlensing survey of the bulge of the Andromeda Galaxy (M31), with the primary aim of constraining its underlying bulge mass distribution and stellar mass function. Here we investigate the feasibility of using such a survey to detect planets in M31. We estimate the efficiency of detecting signals for events induced by planetary systems as a function of planet/star mass ratio and separation, source type and background M31 surface brightness. We find that for planets of a Jupiter-mass or above that are within the lensing zone (~1 -3 AU) detection is possible above 3 $\sigma$, with detection efficiencies ~3% for events associated with giant stars, which are the typical source stars of pixel-lensing surveys. A dramatic improvement in the efficiency of ~40 -- 60% is expected if follow-up observations on an 8m telescope are made possible by a real-time alert system.
In this paper we investigate expanding Bianchi type I models with two tilted fluids with the same linear equation of state, characterized by the equation of state parameter w. Individually the fluids have non-zero energy fluxes w.r.t. the symmetry surfaces, but these cancel each other because of the Codazzi constraint. We prove that when w=0 the model isotropizes to the future. Using numerical simulations and a linear analysis we also find the asymptotic states of models with w>0. We find that future isotropization occurs if and only if $w \leq 1/3$. The results are compared to similar models investigated previously where the two fluids have different equation of state parameters.
Let $X$ be a K3 surface with Picard group $\mathrm{Pic}(X)\cong\mathbb{Z} H$ such that $H^2=2n$. Let $M_{H}(\mathbf{v})$ be the moduli space of Gieseker semistable sheaves on $X$ with Mukai vector $\mathbf{v}$. We say that $\mathbf{v}$ satisfies weak Brill-Noether if the general sheaf in $M_{H}(\mathbf{v})$ has at most one nonzero cohomology group. We show that given any rank $r \geq 2$, there are only finitely many Mukai vectors of rank $r$ on K3 surfaces of Picard rank one where weak Brill-Noether fails. We give an algorithm for finding the potential counterexamples and classify all such counterexamples up to rank 20 explicitly. Moreover, in each of these cases we calculate the cohomology of the general sheaf. Given $r$, we give sharp bounds on $n$, $d$, and $a$ that guarantee that $\mathbf{v}=(r,dH,a)$ satisfies weak Brill-Noether. As a corollary, we obtain another proof of the classification of Ulrich bundles on K3 surfaces of Picard rank one. In addition, we discuss the question of when the general sheaf in $M_H(\mathbf{v})$ is globally generated. Our techniques make crucial use of Bridgeland stability conditions.
We investigate the anticanonical height zeta function of a (non necessarily split) toric variety defined over a global field of positive characteristic, drawing our inspiration from the method used by Batyrev and Tschinkel to deal with the analogous problem over a number field. By the way, we give a detailed account of their method.
The homogeneous Friedman-Lema\^\i tre-Robertson-Walker (FLRW) cosmology of a free scalar field with vanishing cosmological constant was recently shown to be invariant under the one-dimensional conformal group $\textrm{SL}(2,\mathbb{R})$ acting as M{\"o}bius transformations on the proper time. Here we generalize this analysis to arbitrary transformations of the proper time, $\tau\mapsto \tilde{\tau}=f(\tau)$, which are not to be confused with reparametrizations of the time coordinate. First, we show that the FLRW cosmology with a non-vanishing cosmological constant $\Lambda\ne 0$ is also invariant under a $\textrm{SL}(2,\mathbb{R})$ group of conformal transformations. The associated conformal Noether charges form a $\mathfrak{sl}(2,\mathbb{R})$ Lie algebra which encodes the cosmic evolution. Second, we show that a cosmological constant can be generated from the $\Lambda=0$ case through particular conformal transformations, realizing a compactification or de-compactification of the proper time depending on the sign of $\Lambda$. Finally, we propose an extended FLRW cosmological action invariant under the full group $\textrm{Diff}({\cal S}^1)$ of conformal transformations on the proper time, by promoting the cosmological constant to a gauge field for conformal transformations or by modifying the scalar field action to a Schwarzian action. Such a conformally-invariant cosmology leads to a renewed problem of time and to the necessity to re-think inflation in purely time-deparameterized terms.
Spectral analysis of ROSAT PSPC and ASCA archive data and a recent ROSAT HRI observation of the powerful FRII radio galaxy 3C 219 reveal an absorbed point-like source, coincident with the nucleus, and a non-thermal extended component aligned with the radio structure. The point-like source can be readily interpreted as a hidden quasar in the nucleus, giving further support to the unification scheme of FRII radio galaxies and radio loud quasars. The coincidence between the X-ray (0.1-10 keV) and radio spectral index suggest that most of the emission associated with the extended component is due to the inverse Compton process in the radio lobes. The extended circumnuclear emission can be understood as Compton scattering of the IR-optical radiation emitted by the hidden quasar and surrounding dusty/molecular torus. This is the first observational evidence supporting the existence of this effect, which also probes the relativistic electron spectrum at energies much lower than those involved in the synchrotron radio emission. The observed X-ray flux can be matched by assuming that the energy density of the relativistic particles exceed the equipartition value by about a factor of 10. At larger distances from the nucleus ($\geq 70$kpc) the inverse Compton scattering with the cosmic microwave background photons becomes more important and may explain the observed X-ray features if positive fluctuations in the column densities of relativistic electrons are present. Alternatively, one cannot exclude with the present data a thermal contribution by hot clumpy gas surrounding the radio lobes.
Clustering methods are an important tool to enumerate and describe the different coherent kinds of Gamma Ray Bursts (GRBs). But their performance can be affected by a number of factors such as the choice of clustering algorithm and inherent associated assumptions, the inclusion of variables in clustering, nature of initialization methods used or the iterative algorithm or the criterion used to judge the optimal number of groups supported by the data. We analyzed GRBs from the BATSE 4Br catalog using $k$-means and Gaussian Mixture Models-based clustering methods and found that after accounting for all the above factors, all six variables -- different subsets of which have been used in the literature -- and that are, namely, the flux duration variables ($T_{50}$, $T_{90}$), the peak flux ($P_{256}$) measured in 256-millisecond bins, the total fluence ($F_t$) and the spectral hardness ratios ($H_{32}$ and $H_{321}$) contain information on clustering. Further, our analysis found evidence of five different kinds of GRBs and that these groups have different kinds of dispersions in terms of shape, size and orientation. In terms of duration, fluence and spectrum, the five types of GRBs were characterized as intermediate/faint/intermediate, long/intermediate/soft, intermediate/intermediate/intermediate, short/faint/hard and long/bright/intermediate.
This paper concerns the fractional $p$-Laplace operator $\Delta_p^s$ in non-divergence form, which has been introduced in [Bjorland, Caffarelli, Figalli (2012)]. For any $p\in [2,\infty)$ and $s\in (\frac{1}{2},1)$ we first define two families of non-local, non-linear averaging operators, parametrised by $\epsilon$ and defined for all bounded, Borel functions $u:\mathbb{R}^N\to \mathbb{R}$. We prove that $\Delta_p^s u(x)$ emerges as the $\epsilon^{2s}$-order coefficient in the expansion of the deviation of each $\epsilon$-average from the value $u(x)$, in the limit of the domain of averaging exhausting an appropriate cone in $\mathbb{R}^N$ at the rate $\epsilon\to 0$.   Second, we consider the $\epsilon$-dynamic programming principles modeled on the first average, and show that their solutions converge uniformly as $\epsilon\to 0$, to viscosity solutions of the homogeneous non-local Dirichlet problem for $\Delta_p^s$, when posed in a domain $\mathcal{D}$ that satisfies the external cone condition and subject to bounded, uniformly continuous data on $\mathbb{R}^N\setminus \mathcal{D}$.   Finally, we interpret such $\epsilon$-approximating solutions as values to the non-local Tug-of-War game with noise. In this game, players choose directions while the game position is updated randomly within the infinite cone that aligns with the specified direction, whose aperture angle depends on $p$ and $N$, and whose $\epsilon$-tip has been removed.
We propose a non-perturbative $ab$ $initio$ approach to calculate the electrical conductivity of a liquid metal. Our approach is based on the Kubo formula and the theory of electron-phonon coupling (EPC), and unlike the conventional empirical approach based on the Kubo-Greenwood formula, fully takes into account the effect of coupling between electrons and moving ions. We show that the electrical conductivity at high temperature is determined by an EPC parameter $\lambda_{\mathrm{tr}}$, which can be inferred, non-perturbatively, from the correlation of electron scattering matrices induced by ions. The latter can be evaluated in a molecular dynamics simulation. Based on the density-functional theory and pseudopotential methods, we implement the approach in an $ab$ $initio$ manner. We apply it to liquid sodium and obtain results in good agreement with experiments. This approach is efficient and based on a rigorous theory, suitable for applying to general metallic liquid systems.
We report the values of some thermal and electrical properties of Candelilla Wax (euphorbia cerifera). The open-cell photoacoustic technique and another photothermic technique - based on the measure of the temperature decay of a heated sample - were employed to obtain the thermal diffusivity ($\alpha_{s} = 0.026 \pm 0.00095 {cm}^{2}{/sec}$) as well as the thermal conductivity ($k=2.132 \pm 0.16 {W/mK}$) of this wax. The Kelvin null method was used to measure the dark decay of the surface potential of the sample after a Corona Discharge, obtaining a resistivity of $\rho_e=5.98 \pm 0.19 \times 10^{17} {ohm-cm}$.
In this document we discuss the long time behaviour for the homogeneous Landau-Fermi-Dirac equation in the hard potential case. Uniform in time estimates for statistical moments and Sobolev regularity are presented and used to prove exponential relaxation of non degenerate distributions to the Fermi-Dirac statistics. All these results are valid for rather general initial datum. An important feature of the estimates is the independence with respect to the quantum parameter. Consequently, in the classical limit the same estimates are recovered for the Landau equation.
We study a model of interacting vortices in a type II superconductor. In the weak coupling limit, we constructed a mean-field theory which allows us to accurately calculate the vortex density distribution inside a confining potential. In the strong coupling limit, the correlations between the particles become important and the mean-field theory fails. Contrary to recent suggestions, this does not imply failure of the Boltzmann-Gibbs statistical mechanics, as we clearly demonstrate by comparing the results of Molecular Dynamics and Monte Carlo simulations.
We study the effect of brane polarization on the supersymmetry transformations of probe anti-D3-branes at the tip of a Klebanov-Strassler throat geometry. As is well known, the probe branes can polarize into NS5-branes and decay to a supersymmetric state by brane-flux annihilation. The effective potential has a metastable minimum as long as the number of anti-D3-branes is small compared to the number of flux quanta. We study the reduced four-dimensional effective NS5-brane theory and show that in the metastable minimum supersymmetry is non-linearly realized to leading order, as expected for spontaneously broken supersymmetry. However, a strict decoupling limit of the higher order corrections in terms of a standard nilpotent superfield does not seem to exist. We comment on the possible implications of these results for more general low-energy effective descriptions of inflation or de Sitter vacua.
In the current series of two papers, we study the long time behavior of the following random Fisher-KPP equation $$ u_t =u_{xx}+a(\theta_t\omega)u(1-u),\quad x\in\mathbb{R} $$ where $\omega\in\Omega$, $(\Omega, \mathcal{F},\mathbb{P})$ is a given probability space, $\theta_t$ is an ergodic metric dynamical system on $\Omega$, and $a(\omega)>0$ for every $\omega\in\Omega$. We also study the long time behavior of the following nonautonomous Fisher-KPP equation, $$ u_t=u_{xx}+a_0(t)u(1-u),\quad x\in\mathbb{R}$$ where $a_0(t)$ is a positive locally H\"older continuous function. In this first part of the series, we investigate the stability of positive equilibria and the spreading speeds. Under some proper assumption on $a(\omega)$, we show that the constant solution $u=1$ of (1) is asymptotically stable with respect to strictly positive perturbations and show that (1) has a deterministic spreading speed interval $[2\sqrt{\underline a}, 2\sqrt{\bar a}]$, where $\underline{a}$ and $\bar a$ are the least and the greatest means of $a(\cdot)$, respectively, and hence the spreading speed interval is linearly determinant. It is shown that the solution of (1) with the initial function which is bounded away from $0$ for $x\ll -1$ and is $0$ for $x\gg 1$ propagates at the speed $2\sqrt {\hat a}$, where $\hat a$ is the average of $a(\cdot)$. Under some assumption on $a_0(\cdot)$, we also show that the constant solution $u=1$ of (2) is asymptotically stably and (2) admits a bounded spreading speed interval.   It is not assumed that $a(\omega)$ and $a_0(t)$ are bounded above and below by some positive constants. The results obtained in this part are new and extend the existing results in literature on spreading speeds of Fisher-KPP equations. In the second part of the series, we will study the existence and stability of transition fronts of (1) and (2).
We report the most important results on the parsec-scale properties of a complete sample of radio galaxies carried out at radio frequencies with the Global VLBI array and with the VLBA. Relativistic parsec-scale jets are common both in FRI and FRII radio galaxies, and their orientation to the line of sight is in agreement with the expectations from the unified schemes for radio loud AGNs. Proper motion has been detected in a few FRI galaxies in the sample. FRI and FRII radio galaxies exhibit very similar properties on the parsec-scale. Finally a few radio sources in the sample show evidence of velocity structure in the parsec-scale jet, i.e. a central spine with high Lorentz factor $\gamma$ and slower layers.
The physics of peripheral collisions with relativistic heavy ions (PCRHI) is reviewed. One- and two-photon processes are discussed.
In this paper we present a framework for the design and implementation of offset equivariant networks, that is, neural networks that preserve in their output uniform increments in the input. In a suitable color space this kind of networks achieves equivariance with respect to the photometric transformations that characterize changes in the lighting conditions. We verified the framework on three different problems: image recognition, illuminant estimation, and image inpainting. Our experiments show that the performance of offset equivariant networks are comparable to those in the state of the art on regular data. Differently from conventional networks, however, equivariant networks do behave consistently well when the color of the illuminant changes.
An exactly-solvable model for the decay of a metastable state coupled to a semi-infinite tight-binding lattice, showing large deviations from exponential decay in the strong coupling regime, is presented. An optical realization of the lattice model, based on discrete diffraction in a semi-infinite array of tunneling-coupled optical waveguides, is proposed to test non-exponential decay and for the observation of an optical analog of the quantum Zeno effect.