ShantanuT01/DACTYL-Pretraining huggingface dataset:
We studied the high temperature plasma in the direction of the Sculptor supercluster at z=0.108 with Suzaku. Suzaku carried out four observations in the supercluster: namely, A2811, A2811 offset, A2804, A2801 regions in 2005 Nov.--Dec., including the regions beyond the virial radii of these clusters. The study needed precise background estimation because the measured intensity of the redshifted lines, especially those from oxygen, were strongly affected by the the Galactic emission. The spectra taken in the regions outside of the virial radii of the member clusters were used as the background which included both the Galactic and Cosmic X-ray Background (CXB) components. We also used the background data which were taken near the Sculptor supercluster. Temperature and metal abundance profiles were determined to the virial radii of the member clusters, and then we searched for the oxygen line emission in the region outside of the virial radii of the clusters. As a result, the temperature of the clusters decreased toward the virial radii, and the spectral fits for the filament region did not require extra component other than the Galactic and CXB components. We constrained the intensities of O VII and O VIII lines to be less than 8.1 and 5.1 photons cm^-2 s^-1 arcmin^-2, respectively, as 2-sigma upper limits. The intensity of O VII indicates n_H < 1.6e-5 cm^-3 (Z/0.1 Z_solar)^-1/2 (L/25 Mpc)^-1/2, which corresponds to an over density, delta < 60 (Z/0.1 Z_solar)^-1/2 (L/25 Mpc)^-1/2.
We study the differences and similarities in the luminosities of bound, infalling and the so-called backsplash (Gill et al. 2005) galaxies of the Milky Way and M31 using a hydrodynamical simulation performed within the Constrained Local UniversE Simulation (CLUES) project. The simulation models the formation of the Local Group within a self-consistent cosmological framework. We find that even though backsplash galaxies passed through the virial radius of their host halo and hence may have lost a (significant) fraction of their mass, their stellar populations are hardly affected. This leaves us with comparable luminosity functions for infalling and backsplash galaxies and hence little hope to decipher their past (and different) formation and evolutionary histories by luminosity measurements alone. Nevertheless, due to the tidal stripping of dark matter we find that the mass-to-light ratios have changed when comparing the various populations against each other: they are highest for the infalling galaxies and lowest for the bound satellites with the backsplash galaxies in-between.
The chaotic hypothesis is proposed as a basis for a general theory of nonequilibrium stationary states.   Version 2: new comments added after presenting this talk at the Meeting mentioned in the Acknowledgement. One typo corrected.
Motivated by the recent discoveries that six Ultraluminous X-ray Sources (ULXs) are powered by highly super-Eddington X-ray pulsars, we searched for additional pulsating ULX (PULX) candidates by identifying sources that exhibit long-term flux variability of at least an order of magnitude (a common feature seen in the 6 known PULXs, which may potentially be related to transitions to the propeller regime). Expanding on previous studies, we used the available fluxes from XMM-Newton, Swift and Chandra, along with carefully computed upper limits in cases of a non-detection, to construct long-term lightcurves for a sample of 296 ULXs selected from the XMM-Newton archive. Among these 296, we find 25 sources showing flux variability larger than a factor of 10, of which 17 show some evidence for (or are at least consistent with) exhibiting bi-modal flux distributions, as would be expected for sources undergoing propeller transitions. These sources are excellent candidates for continued monitoring programs to further test for this behaviour. There are 3 sources in our final sample with fluxes similar to NGC 5907 ULX1, currently the faintest known PULX, which would also be good targets for deeper observations with current facilities to search for pulsations. For the rest of the PULX candidates identified here, the next generation of X-ray telescopes (such as Athena) may be required to determine their nature owing to their lower peak fluxes.
In [arXiv:1512.02232 [hep-th]] it was argued, based on the construction of a holographic c-function, that the curvature singularity of a black brane can be thought of as a trivial IR fixed point. This is dual to the gapped nature of the thermal state in the IR. So one can say that by taking one kind of low energy limit in the thermal CFT we are probing the near-singularity region. But there is another more conventional low energy limit which corresponds to probing the near-horizon region. Now, instead of one, if we think in terms of these two low-energy limits and take into account the fact that in AdS-CFT the only observables are CFT correlators then we can get a completely different interpretation of the curvature singularity. In a nutshell, the very long wavelength degrees of freedom in the thermal CFT carry information of both the near-horizon and the near-singularity regions, but, the field theory observer cannot, in principle, disentangle the information of the near-horizon region from the information of the near-singularity region using the the thermal CFT correlators. This can be interpreted as a very specific form of holographic "non-locality" in a black hole background which relates the "inside and the outside". We argue in the paper that owing to this "non-locality", the space-like curvature singularity along with its problems, which are all local in nature, completely disappear from the theory or get dissolved. But, the same "non-locality" now tells us that some of the "$e^{-S}$-effects" that one finds, for example, in the late time thermal two-point function, can be thought of as carrying complete information about "Planck-scale effects near the singularity". From the local EFT point of view this may be called "UV-IR-mixing" which is caused by the "non-locality". We also comment on its close relation to black hole complementarity.
We consider first order variational MFG in the whole space, with aggregative interactions and density constraints, such that the stationary states of the game are contained in two isolated compact sets of mass distributions with finite quadratic moments. Under general assumptions on the interaction potential, we provide a method for the construction of periodic in time solutions for the MFG, which oscillate among the two sets of static equilibria. Moreover, as the period increases to infinity, we show that these periodic solutions converge, in a suitable sense, to heteroclinic connections. As a model example, we consider a MFG system where the interactions are modeled via a Riesz-type aggregative potential with spatial preferences.
The square-well fluid with hard-sphere diameters is studied within the framework of Thermodynamic Geometry (TG). Coexistence and spinodal curves, as well as the Widom line for ranges $\lambda^{*} = 1.25, 1.5, 2.0, 3.0$ for this fluid are carefully studied using geometric methods. We are able to show that, unlike coexistence curves, an exact result can be given along all the thermodynamic space and for all potential ranges for spinodal curves. Additionally, $R$-Widom line which is defined as the locus of extrema of the curvature scalar is calculated as a function of the potential range, satisfying near the critical point a kind of Clausius-Clapeyron equation. It is argued that this relation could be a signature of certain type of characteristic phase transition when crossing the boundary of the Widom line.
The present thesis is devoted towards the study of various aspects of the phase transition phenomena occurring in black holes defined in an Anti-de-Sitter (AdS) space. Based on the fundamental principles of thermodynamics and considering a grand canonical framework we examine various aspects of the phase transition phenomena occurring in AdS black holes. We analytically check that this phase transition between the smaller and larger mass black holes obey Ehrenfest relations defined at the critical point and hence confirm a second order phase transition. This include both the rotating and charged black holes in Einstein gravity. Apart from studying these issues, based on a canonical framework, we also investigate the critical behavior in charged AdS black holes. The scaling laws for these black holes are found to be compatible with the static scaling hypothesis. Finally, based on the usual framework of AdS/CFT duality, we investigate the phase transition phenomena occurring in charged hairy black holes defined in an asymptotically AdS space. Based on analytic calculations, and using the AdS/CFT dictionary, we explicitly compute the order-parameter for the dual CFT close to the critical point of the phase transition and found that the critical exponent associated with the condensation is $\frac{1}{2}$, which is the universal result of the mean field theory. Moreover, we also find that in the presence of an external magnetic field, the dual CFT exhibit a perfect diamagnetism at low temperatures, which may be regarded as the reminiscent of the so called Meissner effect.
We prove that for any real polynomial $f(x) \in\mathbb{R} [x]$ the set $$ \{\alpha \in \mathbb{R}: \liminf_{n\to \infty} n\log n ||\alpha f(n)|| >0\} $$ has positive Hausdorff dimension. Here $||\xi ||$ means the distance from $\xi $ to the nearest integer. Our result is based on an original method due to Y. Peres and W. Schlag.
Aims. We aim to develop a chemical model that contains a consistent description of spin-state chemistry in reactions involving chemical species with multiple deuterons. We apply the model to the specific case of deuterated ammonia, to derive values for the various spin-state ratios.   Methods. We apply symmetry rules in the complete scrambling assumption to calculate branching ratio tables for reactions between chemical species that include multiple protons and/or deuterons. Reaction sets for both gas-phase and grain-surface chemistry are generated using an automated routine that forms all possible spin-state variants of any given reaction with up to six H/D atoms. Single-point and modified Bonnor-Ebert models are used to study the density and temperature dependence of ammonia and its isotopologs, and the associated spin-state ratios.   Results. We find that the spin-state ratios of the ammonia isotopologs are, at late times, very different from their statistical values. The ratios are rather insensitive to variations in the density, but present strong temperature dependence. We derive high peak values ($\sim$ 0.1) for the deuterium fraction in ammonia, in agreement with previous (gas-phase) models. The deuterium fractionation is strongest at high density, corresponding to a high degree of depletion, and also presents temperature dependence. We find that in the temperature range 5 to 20 K, the deuterium fractionation peaks at $\sim$ 15 K while most of the ortho/para (and meta/para for $\rm ND_3$) ratios present a minimum at 10 K (ortho/para $\rm NH_2D$ has instead a maximum at this temperature).   Conclusions. Owing to the density and temperature dependence found in the abundances and spin-state ratios of ammonia and its isotopologs, it is evident that observations of ammonia and its deuterated forms can provide important constraints on the physical structure of molecular clouds.
We give the Green function, momentum distribution, two-particle correlation function, and structure factor for the bound state of N indistinguishable bosons with an attractive delta-function interaction in one dimension, and an argument showing that this boson "molecule" has no excited states other than dissociation into separated pieces.
We examine the production of a new $Z'$ gauge boson in association with photons or jets at future hadron supercolliders as a probe of its couplings to fermions. Associated jet production is found to be rather insensitive to these couplings and suffers from large uncertainties as well as substantial backgrounds. On the other hand, the ratio of rates for associated photon $Z'$ production to that of conventional $Z'$ production has a rather clean signature (once appropriate cuts are made), and is found to be quite sensitive to the choice of extended electroweak model, while being simultaneously insensitive to structure function uncertainties and QCD corrections. Rates at both the SSC and LHC are significant for $Z'$ masses in the 1 TeV range.
We calculate exactly the time-dependent reduced density matrix for the central spin in the central-spin model with homogeneous Heisenberg couplings. Therefrom, the dynamics and the entanglement entropy of the central spin are obtained. A rich variety of behaviors is found, depending on the initial state of the bath spins. For an initially unpolarized unentangled bath, the polarization of the central spin decays to zero in the thermodynamic limit, while its entanglement entropy becomes maximal. On the other hand, if the unpolarized environment is initially in an eigenstate of the total bath spin, the central spin and the entanglement entropy exhibit persistent monochromatic large-amplitude oscillations. This raises the question to what extent entanglement of the bath spins prevents decoherence of the central spin.
It is shown that the exponential is the only distribution which satisfies a certain regression equation. This characterization equation involves the conditional expectation (regression function) of a record value given a pair of record values, one previous and one future, as covariates. The underlying distribution is exponential if and only if the above regression equals the expected value of an appropriately defined Beta distributed random variable. In a particular case, the expected value of the Beta variable reduces to a weighted average of the covariates.
We prove convergence of suitable subsequences of weak solutions of a diffuse interface model for the two-phase flow of incompressible fluids with different densities with a nonlocal Cahn-Hilliard equation to weak solutions of the corresponding system with a standard "local" Cahn-Hilliard equation. The analysis is done in the case of a sufficiently smooth bounded domain with no-slip boundary condition for the velocity and Neumann boundary conditions for the Cahn-Hilliard equation. The proof is based on the corresponding result in the case of a single Cahn-Hilliard equation and compactness arguments used in the proof of existence of weak solutions for the diffuse interface model.
In this paper, a discriminative two-phase dictionary learning framework is proposed for classifying human action by sparse shape representations, in which the first-phase dictionary is learned on the selected discriminative frames and the second-phase dictionary is built for recognition using reconstruction errors of the first-phase dictionary as input features. We propose a "zeroth class" trick for detecting undiscriminating frames of the test video and eliminating them before voting on the action categories. Experimental results on benchmarks demonstrate the effectiveness of our method.
We discuss effects of the different chemical bondings on the island morphology and on the island density scaling in two-component submonolayer growth. Different regimes depending on the strength of the mutual interactions and on the relative mobility of species are described and studied by kinetic Monte Carlo simulations using a two-component solid-on-solid growth model. Results for the temperature and flux dependence of the island density as well as examples of the surface morphologies are presented.
The purpose of this work is to study the global wellposedness and large time behavior results of strong solutions for the compressible Oldroyd-B model derived by Barrett, Lu, S\"uli (Commun. Math. Sci., 15, 1265--1323, 2017). Exploiting the Harmonic analysis tools (especially Littlewood-Paley theory), we first study the global well-posedness of the model with small initial data in spaces with low regularity. Then, under a suitable condition involving only the low frequency of the initial data, we also obtain the optimal decay rates of the solutions. Compared with the result by Wang and Wen (Math. Models Methods Appl. Sci., 30, 139--179, 2020), the polymer number density is allowed to vanish and the stress tensor isnear zero equilibrium.
LAMOST DR5 released more than 200,000 low resolution spectra of early-type stars with S/N>50. Searching for metallic-line (Am) stars in such a large database and study of their statistical properties are presented in this paper. Six machine learning algorithms were experimented with using known Am spectra, and both the empirical criteria method(Hou et al. 2015) and the MKCLASS package(Gray et al. 2016) were also investigated. Comparing their performance, the random forest (RF) algorithm won, not only because RF has high successful rate but also it can derives and ranks features. Then the RF was applied to the early type stars of DR5, and 15,269 Am candidates were picked out. Manual identification was conducted based on the spectral features derived from the RF algorithm and verified by experts. After manual identification, 9,372 Am stars and 1,131 Ap candidates were compiled into a catalog. Statistical studies were conducted including temperature distribution, space distribution, and infrared photometry. The spectral types of Am stars are mainly between F0 and A4 with a peak around A7, which is similar to previous works. With the Gaia distances, we calculated the vertical height Z from the Galactic plane for each Am star. The distribution of Z suggests that the incidence rate of Am stars shows a descending gradient with increasing jZj. On the other hand, Am stars do not show a noteworthy pattern in the infrared band. As wavelength gets longer, the infrared excess of Am stars decreases, until little or no excess in W1 and W2 bands.
The remarkable gapless and linear band structure of graphene opens up new carrier relaxation channels bridging the valence and the conduction band. These Auger scattering processes change the number of charge carriers and can give rise to a significant multiplication of optically excited carriers in graphene. This is an ultrafast many-particle phenomenon that is of great interest both for fundamental many-particle physics as well as technological applications. Here, we review the research on carrier multiplication in graphene and Landau-quantized graphene including theoretical modelling and experimental demonstration.
We present deep $UBVI_C$ photometric data of the young open cluster Westerlund 2. An abnormal reddening law of $R_{V,cl}=4.14\pm0.08$ was found for the highly reddened early-type members ($E(B-V)\geq 1.45$), whereas a fairly normal reddening law of $R_{V,fg}=3.33\pm0.03$ was confirmed for the foreground early-type stars ($E(B-V)_{fg}<1.05$). The distance modulus was determined from zero-age main-sequence (ZAMS) fitting to the reddening-corrected colour-magnitude diagram of the early-type members to be $V_0-M_V=13.9\pm0.14$ (random error) $_{-0.1}^{+0.4}$ (the upper limit of systematic error) mag ($d = 6.0 \pm 0.4 _{-0.3}^{+1.2}$ kpc). To obtain the initial mass function, pre-main-sequence (PMS) stars were selected by identifying the optical counterparts of Chandra X-ray sources and mid-infrared emission stars from the Spitzer GLIMPSE source catalog. The initial mass function shows a shallow slope of $\Gamma=-1.1 \pm 0.1$ down to $\log m = 0.7$. The total mass of Westerlund 2 is estimated to be at least 7,400 $M_{\odot}$. The age of Westerlund 2 from the main-sequence turn-on and PMS stars is estimated to be $\lesssim$ 1.5 Myr. We confirmed the existence of a clump of PMS stars located $\sim1$ arcmin north of the core of Westerlund 2, but we could not find any clear evidence for an age difference between the core and the northern clump.
For an odd prime $p$ and a number field $F$ containing a $p$th root of unity, we study generalised Tate kernels, $D_F^{[i,n]}$, for $i\in \mathbb{Z}$ and $n\geq 1$, having the properties that if $i\geq 2$ and if either $p$ does not divide $i$ or $\mu_{p^n}\subset F$ then there are natural isomorphisms $D_F^{[i,n]}\cong K^{\mbox{\tiny \'et}}_{2i-1}(O_F^S)/p^n$, and that they are periodic modulo a power of $p$ which depends on $F$ and $n$. Our main result is that if the Gross-Jaulent conjecture holds for $(F,p)$ then there is a natural isomorphism $D_F^{[i,n]}\cong\mathcal{E}_F/p^n$ where $\mathcal{E}_F$ is the Gross kernel. We apply this result to compute lower bounds for capitulation kernels in even \'etale $K$-theory.
This work analyzes the Hall magnetohydrodynamics (HMHD) and magnetohydrodynamics (MHD) numerical simulations of a flaring solar active region as a testbed while idealizing the coronal Alfv\'en speed to be of two orders of magnitude lesser. HMHD supports faster magnetic reconnection and shows richer complexity in magnetic field line evolution compared to the MHD. The magnetic reconnections triggering the flare are explored by numerical simulations augmented with relevant multi-wavelength observations. The initial coronal magnetic field is constructed by non-force-free extrapolation of photospheric vector magnetic field. Magnetic structure involved in the flare is identified to be a flux rope, with its overlying magnetic field lines constituting the quasi-separatrix layers (QSLs) along with a three-dimensional null point and a null line. Compared to the MHD simulation, the HMHD simulation shows a higher and faster ascend of the rope together with the overlying field lines, which further reconnect at the QSL located higher up in the corona. The foot points of the field lines match better with the observations for the HMHD case with the central part of the flare ribbon located at the chromosphere. Additionally, field lines are found to rotate in a circular pattern in the HMHD, whereas no such rotation is seen in the MHD results. Interestingly, plasma is also observed to be rotating in a co-spatial chromospheric region, which makes the HMHD simulation more credible. Based on the aforementioned agreements, HMHD simulation is found to agree better with observations and, thus, opens up a novel avenue to explore.
First steps are taken in a project to construct a general class of conformal and perhaps, eventually, non-conformal quantum field theories of (n-1)-dimensional extended objects in a d=2n dimensional conformal space-time manifold M. The fields live on the spaces E of relative integral (n-1)-cycles in M -- the integral (n-1)-currents of given boundary. Each E is a complete metric space geometrically analogous to a Riemann surface $\Sigma$. For example, if $M=S^d$, $\Sigma = S^2$. The quantum fields on E are to be mapped to observables in a 2d CFT on $\Sigma$. The correlation functions on E are to be given by the 2d correlation functions on $\Sigma$. The goal is to construct a CFT of extended objects in d=2n dimensions for every 2d CFT, and eventually a non-conformal QFT of extended objects for every non-conformal 2d QFT, so that all the technology of 2d QFT can be applied to the construction and analysis of quantum field theories of extended objects. The project depends crucially on settling some mathematical questions about analysis in the spaces E. The project also depends on extending the observables of 2d CFT from the finite sets of points in a Riemann surface to the integral 0-currents.