ShantanuT01/DACTYL-Pretraining huggingface dataset:
We present an axially symmetric formula to calculate the probability of finding gravitational arcs in galaxy clusters, being induced by their massive dark matter haloes, as a function of clusters redshifts and virial masses. The formula includes the ellipticity of the clusters dark matter potential by using a pseudo-elliptical approximation. The probabilities are calculated and compared for two dark-matter halo profiles, the Navarro, Frenk and White (NFW) and the Non-Singular-Isothermal-Sphere (NSIS). We demonstrate the power of our formulation through a Kolmogorov-Smirnov (KS) test on the strong lensing statistics of an X-ray bright sample of low redshift Abell clusters. This KS test allows to establish limits on the values of the concentration parameter for the NFW profile ($c_\Delta$) and the core radius for the NSIS profile (\rc), which are related to the lowest cluster redshift ($z_{\rm cut}$) where strong arcs can be observed. For NFW dark matter profiles, we infer cluster haloes with concentrations that are consistent to those predicted by $\Lambda$CDM simulations. As for NSIS dark matter profiles, we find only upper limits for the clusters core radii and thus do not rule out a purely SIS model. For alternative mass profiles, our formulation provides constraints through $z_{\rm cut}$ on the parameters that control the concentration of mass in the inner region of the clusters haloes. We find that $z_{\rm cut}$ is expected to lie in the 0.0--0.2 redshift, highlighting the need to include very low-$z$ clusters in samples to study the clusters mass profiles.
Using imaginary-time theory, it is shown that the triple-alpha reaction rate can be reliably calculated without the need to solve scattering problems involving three charged particles. The calculated reaction rate is found to agree well with the empirical NACRE rate, which is widely adopted in stellar evolution calculations. The reason for this is explained using $R$-matrix theory. Extremely slow convergence is found to occur when a coupled-channel expansion is introduced, which helps to explain the very different reaction rates obtained using different theoretical approaches.
Two complementary effects modify the GHz magnetization dynamics of nanoscale heterostructures of ferromagnetic and normal materials relative to those of the isolated magnetic constituents: On the one hand, a time-dependent ferromagnetic magnetization pumps a spin angular-momentum flow into adjacent materials and, on the other hand, spin angular momentum is transferred between ferromagnets by an applied bias, causing mutual torques on the magnetizations. These phenomena are manifestly nonlocal: they are governed by the entire spin-coherent region that is limited in size by spin-flip relaxation processes. We review recent progress in understanding the magnetization dynamics in ferromagnetic heterostructures from first principles, focusing on the role of spin pumping in layered structures. The main body of the theory is semiclassical and based on a mean-field Stoner or spin-density--functional picture, but quantum-size effects and the role of electron-electron correlations are also discussed. A growing number of experiments support the theoretical predictions. The formalism should be useful to understand the physics and to engineer the characteristics of small devices such as magnetic random-access memory elements.
Iron spectral features are thought to be the best tracer of a progenitor of gamma-ray bursts (GRBs). The detections of spectral features such as an iron line and/or a Radiative Recombination edge and Continuum (RRC) were reported in four X-ray afterglows of GRBs. However their properties were different each other burst by burst. For example, Chandra observation of GRB 991216 reported both the strong H-like iron line together with its RRC. On the contrary, Yoshida et al. (2001) report only a detection of the strong RRC in GRB 970828 with ASCA. Since it is difficult to produce the strong RRC, we have to consider special condition for the line and/or the RRC forming region. In this paper, we point out a possibility of a ``non-equilibrium ionization state'' for the line and the RRC forming region.
The data analysis carried out by the LIGO-Virgo collaboration on gravitational-wave events utilizes nested sampling to compute Bayesian evidences and posterior distributions for inferring the source properties of compact binaries. With poor sampling from the constrained prior, nested sampling algorithms may misbehave and fail to sample the posterior distribution faithfully. Fowlie et al. (2020) outlines a method of validating the performance of nested sampling, or identifying pathologies such as plateaus in the parameter space, using likelihood insertion order statistics. Here, this method is applied to nested sampling analyses of all events in the first and second gravitational wave transient catalogs (GWTC-1 and GWTC-2) of the LIGO-Virgo collaboration. The insertion order statistics are tested for uniformity across 45 events in the catalog and it is found that, with a few exceptions that have negligible effect on the final posteriors, the data from the analysis of events in the catalog is consistent with unbiased prior sampling. There is, however, weak evidence against uniformity at the catalog-level meta-test, yielding a Kolmogorov-Smirnov meta-p-value of 1.44 * 10-3.
In this paper we investigate a class of decoupled forward-backward SDEs, where the volatility of the FSDE is degenerate and the terminal value of the BSDE is a discontinuous function of the FSDE. Such an FBSDE is associated with a degenerate parabolic PDE with discontinuous terminal condition. We first establish a Feynman-Kac type representation formula for the spatial derivative of the solution to the PDE. As a consequence, we show that there exists a stopping time \tau such that the martingale integrand of the BSDE is continuous before \tau and vanishes after \tau. However, it may blow up at \tau, as illustrated by an example. Moreover, some estimates for the martingale integrand before \tau are obtained. These results are potentially useful for pricing and hedging discontinuous exotic options (e.g., digital options) when the underlying asset's volatility is small, and they are also useful for studying the rate of convergence of finite-difference approximations for degenerate parabolic PDEs.
(abridged) Steidel & Sargent (1991a) found that the spectra of the components of the close quasar pairs Q1634+267A,B and Q2345+007A,B were in each case remarkably similar but that individual broad emission lines due to Ly_alpha, Si IV, C IV, and C III] exhibited differences in profile or equivalent width between the A and B components. If the A and B components of these objects result from gravitational lensing of a single QSO, the difference in light travel time for the two images is roughly 1 year for both pairs. Accordingly, the authors suggested that observations of the spectra of single QSOs would reveal similar changes in emission line profiles and equivalent widths on a time scale of a year or less. In order to test Steidel & Sargent's hypothesis, we obtained in 1992 high quality spectra of 30 quasars with z(em) ~ 1 selected from the brighter QSOs in the sample of Steidel & Sargent (1991b), which those authors had observed in 1989-90. We find that the spectra from the two epochs are remarkably similar for all QSOs, except for overall changes in fluxes and minor differences in continuum shape which are probably artifacts introduced by the observing procedures. However, there are also changes in the equivalent widths or shapes of the stronger emission lines on rest-frame time scales of 1-1.5 years in about two thirds of the QSOs. These observations, therefore, support the notion that the spectra of the components in lensed QSOs need not be exactly identical. Moreover, it should be expected that any differences between the components in such systems should change with time.
Using the Ogata-Shiba wave function, the spectral functions of the one-dimensional infinite U Hubbard model are calculated for various concentrations. It is shown that the ``shadow band'' feature due to 2k_F fluctuations becomes more intense close to half-filling. Comparing these results with exact diagonalization data obtained on finite clusters for the finite U Hubbard model and for the t-J model, it is also shown that this feature remains well-defined for physically reasonable values of the parameters (U/t\simeq 10, J/t\simeq 0.4). The ``shadow'' structure in the spectral functions should thus be observable in angle-resolved photoemission experiments for a variety of quasi-one dimensional compounds.
We introduce the Northumberland Dolphin Dataset 2020 (NDD20), a challenging image dataset annotated for both coarse and fine-grained instance segmentation and categorisation. This dataset, the first release of the NDD, was created in response to the rapid expansion of computer vision into conservation research and the production of field-deployable systems suited to extreme environmental conditions -- an area with few open source datasets. NDD20 contains a large collection of above and below water images of two different dolphin species for traditional coarse and fine-grained segmentation. All data contained in NDD20 was obtained via manual collection in the North Sea around the Northumberland coastline, UK. We present experimentation using standard deep learning network architecture trained using NDD20 and report baselines results.
We present a formulation for the internal motion of equilibrium configurations with a rotational Killing vector in general relativity. As an approximation, this formulation is applicable to investigation of the internal motion of quasi-equilibrium configurations such as binary neutron stars. Based on this simple formulation, a condition for the general relativistic counter rotation has been obtained, though in the recent work by Bonazzola, Gourgoulhon and Marck, their condition for the counter rotation is not enough to specify the internal velocity field. Under the condition given in this paper, the internal velocity field can be determined completely. Indeed, in the counter-rotating case, we have also derived Poisson equations for the internal velocity, which take tractable forms in numerical implementation.
A method is presented here for investigating variations in the upper end of the stellar Initial Mass Function (IMF) by probing the production rate of ionizing photons in unresolved, compact star clusters with ages<10 Myr and covering a range of masses. We test this method on the young cluster population in the nearby galaxy M51a, for which multi-wavelength observations from the Hubble Space Telescope are available. Our results indicate that the proposed method can probe the upper end of the IMF in galaxies located out to at least 10 Mpc, i.e., a factor 200 further away than possible by counting individual stars in young compact clusters. Our results for this galaxy show no obvious dependence of the upper mass end of the IMF on the mass of the star cluster, down to ~1000 M_sun, although more extensive analyses involving lower mass clusters and other galaxies are needed to confirm this conclusion.
The global well-posedness for the incompressible Navier-Stokes-Vlasov equations in two spatial dimensions is established by a priori estimates, the characteristic method and the semigroup analysis.
We study structural properties of spectroscopically confirmed massive quiescent galaxies at $z\approx 3$ with one of the first sizeable samples of such sources, made of ten $10.8<\log(M_{\star}/M_{\odot})<11.3$ galaxies at $2.4 < z < 3.2$ in the COSMOS field whose redshifts and quiescence are confirmed by HST grism spectroscopy. Although affected by a weak bias toward younger stellar populations, this sample is deemed to be largely representative of the majority of the most massive and thus intrinsically rarest quiescent sources at this cosmic time. We rely on targeted HST/WFC3 observations and fit S\'ersic profiles to the galaxy surface brightness distributions at $\approx 4000$ angstrom restframe. We find typically high S\'ersic indices and axis ratios (medians $\approx 4.5$ and $0.73$, respectively) suggesting that, at odds with some previous results, the first massive quiescent galaxies may largely be already bulge-dominated systems. We measure compact galaxy sizes with an average of $\approx 1.4$kpc at $\log(M_{\star}/M_{\odot})\approx 11.2$, in good agreement with the extrapolation at the highest masses of previous determinations of the stellar mass - size relation of quiescent galaxies, and of its redshift evolution, from photometrically selected samples at lower and similar redshifts. This work confirms the existence of a population of compact, bulge dominated, massive, quiescent sources at $z\approx 3$, providing one of the first statistical estimates of their structural properties, and further constraining the early formation and evolution of the first quiescent galaxies.
Bursts of images exhibit significant self-similarity across both time and space. This motivates a representation of the kernels as linear combinations of a small set of basis elements. To this end, we introduce a novel basis prediction network that, given an input burst, predicts a set of global basis kernels -- shared within the image -- and the corresponding mixing coefficients -- which are specific to individual pixels. Compared to state-of-the-art techniques that output a large tensor of per-pixel spatiotemporal kernels, our formulation substantially reduces the dimensionality of the network output. This allows us to effectively exploit comparatively larger denoising kernels, achieving both significant quality improvements (over 1dB PSNR) and faster run-times over state-of-the-art methods.
Ultrarelativistic heavy ion collisions are expected to generate a huge electromagnetic field, $eB \approx 10^{18}\, Gauss$, that induces a splitting of the directed flow, $v_1=\left\langle p_x/p_T \right\rangle $, of charged particles and anti-particles. Such a splitting for charmed meson manifests even for neutral particle/anti-particles pairs ($D^0, \overline{D}^0$), hence being also a unique probe of the formation of the quark-gluon plasma phase. For the first time here we show that electromagnetic field may generate a $v_1(D^0) - v_1( \overline{D}^0)$ as huge as the one recently observed at LHC against early expectations.   Within this new research topic we point out a novel measurement: $v_1$ of leptons from $Z^0$ decay and its correlation to that of $D$ and $B$ mesons. The correlation for $\Delta v_1$ of $l^{+} - l^{-}$, $D^0-\overline{D}^0$ and $B^0-\overline{B}^0$ would provide a strong probe of the electromagnetic origin of the splitting and hence of the formation of a quark-gluon plasma phase with heavy quarks as degrees of freedom. The case of the $v_1({l^{\pm}})$ presents features due to the peculiar form of the $p_T$ spectrum never appreciated before in the study of heavy ion collisions. We specifically predict a sudden change of the $\Delta v_1(p_T)$ of leptons at $p_T=45$ GeV$/c$, that can be traced back to a universal relation of $\Delta v_1$ with the slope of the $p_T$ particle distribution and the integrated effect of the Lorentz force.
Monocular depth estimation is a challenging task that aims to predict a corresponding depth map from a given single RGB image. Recent deep learning models have been proposed to predict the depth from the image by learning the alignment of deep features between the RGB image and the depth domains. In this paper, we present a novel approach, named Structure-Attentioned Memory Network, to more effectively transfer domain features for monocular depth estimation by taking into account the common structure regularities (e.g., repetitive structure patterns, planar surfaces, symmetries) in domain adaptation. To this end, we introduce a new Structure-Oriented Memory (SOM) module to learn and memorize the structure-specific information between RGB image domain and the depth domain. More specifically, in the SOM module, we develop a Memorable Bank of Filters (MBF) unit to learn a set of filters that memorize the structure-aware image-depth residual pattern, and also an Attention Guided Controller (AGC) unit to control the filter selection in the MBF given image features queries. Given the query image feature, the trained SOM module is able to adaptively select the best customized filters for cross-domain feature transferring with an optimal structural disparity between image and depth. In summary, we focus on addressing this structure-specific domain adaption challenge by proposing a novel end-to-end multi-scale memorable network for monocular depth estimation. The experiments show that our proposed model demonstrates the superior performance compared to the existing supervised monocular depth estimation approaches on the challenging KITTI and NYU Depth V2 benchmarks.
The velocity distribution of stars is a sensitive probe of the gravitational potential of the Galaxy, and hence of its dark matter distribution. In particular, the shape of the dark halo (e.g. spherical, oblate, or prolate) determines velocity correlations, and different halo geometries are expected to result in measurable differences. Here we explore and interpret the correlations in the $(v_R, v_z)$-velocity distribution as a function of position in the Milky Way. We selected a high-quality sample of stars from the Gaia DR2 catalogue and characterised the orientation of the velocity distribution or tilt angle over a radial distance range of $[4-13]~$kpc and up to $3.5~$kpc away from the Galactic plane while taking into account the effects of the measurement errors. We find that the tilt angles change from spherical alignment in the inner Galaxy ($R\sim4~$kpc) towards more cylindrical alignments in the outer Galaxy ($R\sim11~$kpc) when using distances that take a global zero-point offset in the parallax of $-29~\mu$as. However, if the amplitude of this offset is underestimated, then the inferred tilt angles in the outer Galaxy only appear shallower and are intrinsically more consistent with spherical alignment for an offset as large as $-54~\mu$as. We further find that the tilt angles do not seem to strongly vary with Galactic azimuth and that different stellar populations depict similar tilt angles. Therefore we introduce a simple analytic function that describes the trends found over the full radial range. Since the systematic parallax errors in Gaia DR2 depend on celestial position, magnitude, and colour in complex ways, it is not possible to fully correct for them. Therefore it will be particularly important for dynamical modelling of the Milky Way to thoroughly characterise the systematics in astrometry in future Gaia data releases.
We prove a convergence property for some families of finely harmonic functions on a fine domain $U$ of $\RR^n$ ($n\ge 2$), and we apply it to prove some regularity of the fine Green kernel of $U$.
We consider the question of loop corrections (i.e. 1/N) in the vector model/higher spin duality following the recent work of Giombi and Klebanov. The purpose of this paper is to gain further more precise comparison between the two sides of the duality. For CFTs given by 3d O(N) or U(N) vector models we evaluate the leading and one loop partition functions in a variety of geometries. Our calculations are performed in the scheme of collective field theory which was seen in earlier studies to represent a bulk description of Vasiliev higher spin theory. The calculations presented provide data for comparison of small fluctuation determinants giving further evidence for the one-to-one bulk identification between the bi-local and the AdS picture. They also offer insight into the identification of coupling constants G and 1/N of the two descriptions for models based on O(N) symmetry.
The Tomonaga--Luttinger parameter $K_{\rho}$ determines the critical behavior in quasi one-dimensional correlated electron systems, e.g., the exponent $\alpha$ for the density of states near the Fermi energy. We use the numerical density-matrix renormalization group method to calculate $K_{\rho}$ from the slope of the density-density correlation function in momentum space at zero wave vector. We check the accuracy of our new approach against exact results for the Hubbard and XXZ Heisenberg models. We determine $K_{\rho}$ in the phase diagram of the extended Hubbard model at quarter filling, $n_{\rm c}=1/2$, and confirm the bosonization results $K_{\rho}=n_{\rm c}^2=1/4$ on the critical line and $K_{\rho}^{\rm CDW}=n_{\rm c}^2/2=1/8$ at infinitesimal doping of the charge-density-wave (CDW) insulator for all interaction strengths. The doped CDW insulator exhibits exponents $\alpha>1$ only for small doping and strong correlations.
In the Constrained-degree percolation model on a graph $(\mathbb{V},\mathbb{E})$ there are a sequence, $(U_e)_{e\in\mathbb{E}}$, of i.i.d. random variables with distribution $U[0,1]$ and a positive integer $k$. Each bond $e$ tries to open at time $U_e$, it succeeds if both its end-vertices would have degrees at most $k-1$. We prove a phase transition theorem for this model on the square lattice $\mathbb{L}^2$, as well as on the d-ary regular tree. We also prove that on the square lattice the infinite cluster is unique in the supercritical phase.
The Sun is located inside an extremely low density and quite irregular volume of the interstellar medium, known as the Local Cavity (LC). It has been widely believed that some kind of interaction could be occurring between the LC and Loop I, a nearby superbubble seen in the direction of the Galactic Center. As a result of such interaction, a wall of neutral and dense material, surrounded by a ring shaped feature, would be formed at the interaction zone. Evidence of this structure was previously observed by analyzing the soft X-ray emission in the direction of Loop I. Our goal is to investigate the distance of the proposed annular region and map the geometry of the Galactic magnetic field in these directions. On that account, we have conducted an optical polarization survey to 878 stars from the Hipparcos catalogue. Our results suggest that the structure is highly twisted and fragmented, showing very discrepant distances along the annular region: approximately 100 pc to the left side and 250 pc to the right side, independently confirming the indication from a previous photometric analysis. In addition, the polarization vectors' orientation pattern along the ring also shows a widely different behavior toward both sides of the studied feature, running parallel to the ring contour in the left side and showing no relation to its direction in the right side. Altogether, these evidence suggest a highly irregular nature, casting some doubt on the existence of a unique large-scale ring-like structure.
In this paper we extend the properties of ordinary points of curves [10] to ordinary closed points of one-dimensional affine reduced schemes and then to ordinary subvarieties of codimension one.
We consider the Einstein-Maxwell-Klein-Gordon equations for a spherically symmetric scalar field scattering off a Reissner-Nordstr\"om black hole in asymptotically flat spacetime. The equations are solved numerically using a hyperboloidal evolution scheme. For suitable frequencies of the initial data, superradiance is observed, leading to a substantial decrease of mass and charge of the black hole. We also derive a Bondi mass loss formula using the Kodama vector field and investigate the late-time decay of the scalar field.