ShantanuT01/DACTYL-Pretraining huggingface dataset:
Context. Scaling relations between cluster properties embody the formation and evolution of cosmic structure. Intrinsic scatters and correlations between X-ray properties are determined from merger history, baryonic processes, and dynamical state.   Aims. We look for an unbiased measurement of the scatter covariance matrix between the three main X-ray observable quantities attainable in large X-ray surveys -- temperature, luminosity, and gas mass. This also gives us the cluster property with the lowest conditional intrinsic scatter at fixed mass.   Methods. Intrinsic scatters and correlations can be measured under the assumption that the observable properties of the intra-cluster medium hosted in clusters are log-normally distributed around power-law scaling relations. The proposed method is self-consistent, based on minimal assumptions, and requires neither the external calibration by weak lensing, dynamical, or hydrostatic masses nor the knowledge of the mass completeness.   Results. We analyzed the 100 brightest clusters detected in the XXL Survey and their X-ray properties measured within a fixed radius of 300 kpc. The gas mass is the less scattered proxy (~8%). The temperature (~20%) is intrinsically less scattered than the luminosity (~30%) but it is measured with a larger observational uncertainty. We found some evidence that gas mass, temperature and luminosity are positively correlated. Time-evolutions are in agreement with the self-similar scenario, but the luminosity-temperature and the gas mass-temperature relations are steeper.   Conclusions. Positive correlations between X-ray properties can be determined by the dynamical state and the merger history of the halos. The slopes of the scaling relations are affected by radiative processes.
We calculate the radiation spectrum and its time variability of the black hole accretion disk-corona system based on the three-dimensional magnetohydrodynamic simulation. In explaining the spectral properties of active galactic nuclei (AGNs), it is often assumed that they consist of a geometrically thin, optically thick disk and hot, optically thin corona surrounding the thin disk. As for a model of the corona, we adopt the simulation data of three-dimensional, non-radiative MHD accretion flows calculated by Kato and coworkers, while for a thin disk we assume a standard type disk. We perform Monte Carlo radiative transfer simulations in the corona, taking into account the Compton scattering of soft photons from the thin disk by hot thermal electrons and coronal irradiation heating of the thin disk, which emits blackbody radiation. By adjusting the density parameter of the MHD coronal flow, we can produce the emergent spectra which are consistent with those of typical Seyfert galaxies. Moreover, we find rapid time variability in X-ray emission spectra, originating from the density fluctuation produced by the magnetorotational instability in the MHD corona. The features of reflection component including iron fluorescent line emission are also briefly discussed.
The concept of entanglement fraction is generalized to define coherence fraction of a quantum state. Precisely, it quantifies the proximity of a quantum state to maximally coherent state and it can be used as a measure of coherence. Coherence fraction has a connection with $l_1$-norm coherence and provides the criteria of coherence distillability. Optimal coherence fraction corresponding to a channel, defined from this new idea of coherence fraction, obeys a complementary relation with its decohering power. The connection between coherence fraction and $l_1$-norm coherence turns to hold for bipartite pure states and $X$ states too. The bipartite generalization shows that the local coherence fractions of a quantum state are not free and they are bounded by linear function of its global coherence fraction. Dynamics of optimal coherence fraction is also studied for single sided and both sided application of channels. Numerical results are provided in exploring properties of optimal coherence fraction.
I report the detection of two X-ray sources of luminosities $\sim 10^{36} {\rm~ergs~s^{-1}}$ in the central region of 30 Doradus. These two sources appear point-like in images taken with the {\sl ROSAT} HRI. One of the sources is most likely associated with a close spectroscopic binary R140a2 (WN6) with an orbital period of 2.76 days. The mass of the unknown binary component is likely in the range of $2.4 - 15{\rm~M}_\odot$. This suggests that the X-ray source could represent a long-sought class of binaries containing a Wolf-Rayet star and a black hole. The other source, which coincides spatially with Mk34 (WN4.5), may have a similar nature. Available X-ray spectral data support this Wolf-Rayet + black-hole binary explanation of the two sources. I have used a {\sl ROSAT} PSPC observation to show that the sources have ultrasoft spectra with possible intrinsic absorption. Modeled with multicolor blackbody disks, the spectra provide estimates of the disks' characteristic inner radii, which are in agreement with those obtained for the known black-hole candidates. An {\sl ASCA} observation has further revealed a hard X-ray spectral component from the central 30 Doradus region. This component, represented by a power law with a photon index of $\sim 2.4$, may belong to the two sources. The characteristics of both the power-law and ultrasoft components strongly indicates that the two sources are black-hole candidates in high-mass X-ray binaries.
Let X be a minimal complex surface of general type such that its image via the canonical map is a surface; we denote by d the degree of the canonical map.   In this expository work, first of all we recall the known possibilities for the canonical image and for d when the canonical map is not birational, which are quite a few, and then we consider the question of producing concrete examples for all of them.   We present the two main methods of construction of such examples and we give several instances of their application. We end the paper outlining the state of the art on this topic and raising several questions.
We present a new N-body simulation from the MICE collaboration, the MICE Grand Challenge (MICE-GC), containing about 70 billion dark-matter particles in a (3 Gpc/h)^3 comoving volume. Given its large volume and fine spatial resolution, spanning over 5 orders of magnitude in dynamic range, it allows an accurate modeling of the growth of structure in the universe from the linear through the highly non-linear regime of gravitational clustering. We validate the dark-matter simulation outputs using 3D and 2D clustering statistics, and discuss mass-resolution effects in the non-linear regime by comparing to previous simulations and the latest numerical fits. We show that the MICE-GC run allows for a measurement of the BAO feature with percent level accuracy and compare it to state-of-the-art theoretical models. We also use sub-arcmin resolution pixelized 2D maps of the dark-matter counts in the lightcone to make tomographic analyses in real and redshift space. Our analysis shows the simulation reproduces the Kaiser effect on large scales, whereas we find a significant suppression of power on non-linear scales relative to the real space clustering. We complete our validation by presenting an analysis of the 3-point correlation function in this and previous MICE simulations, finding further evidence for mass-resolution effects. This is the first of a series of three papers in which we present the MICE-GC simulation, along with a wide and deep mock galaxy catalog built from it. This mock is made publicly available through a dedicated webportal, http://cosmohub.pic.es.
Condensation is characterized with a single macroscopic condensate whose mass is proportional to a system size $N$. We demonstrate how important particle interactions are in condensation phenomena. We study a modified version of the zero-range process by including a pair exclusion. Each particle is associated with its own partner, and particles of a pair are forbidden to stay at the same site. The pair exclusion is weak in that a particle interacts with only a single one among all others. It turns out that such a weak interaction changes the nature of condensation drastically. There appear a number of mesoscopic condensates: the mass of a condensate scales as $m_{\rm con}\sim N^{1/2}$ and the number of condensates scales as $N_{\rm con} \sim N^{1/2}$ with a logarithmic correction. These results are derived analytically through a mapping to a solvable model under a certain assumption, and confirmed numerically.
A new phase V of hydrogen was recently claimed in experiments above 325 GPa and 300 K. Due to the extremely small sample size at such record pressures the measurements were limited to Raman spectroscopy. The experimental data on increase of pressure shows decreasing Raman activity and darkening of the sample, which suggests band-gap closure and impending molecular dissociation, but no definite conclusions could be reached. Furthermore, the available data is insufficient to determine the structure of phase V, which remains unknown. Introducing saddle-point $ab$ $initio$ random structure searching (sp-AIRSS), we find several new structural candidates of hydrogen which could describe the observed properties of phase V. We investigate hydrogen metallisation in the proposed candidate structures, and demonstrate that smaller band gaps are associated with longer bond lengths. We conclude that phase V is a stepping stone towards metallisation.
[Abridged] We test the reliability of a method to measure the mean halo mass of Damped Ly-alpha absorbers (DLAs). The method is based on measuring the ratio of the cross-correlation between DLAs and galaxies to the auto-correlation of the galaxies themselves ($w_{\rm dg}/w_{\rm gg}$), which is (in linear theory) the ratio of their bias factor. This is shown to be true irrespective of the galaxy redshift distribution, provided that one uses the same galaxies for the two correlation functions. The method is applicable to all redshifts. Here, we focus on z=3 DLAs and we demonstrate that the method robustly constrains the mean DLA halo mass using smoothed particle hydrodynamics (SPH) cosmological simulations. If we use the bias formalism of Mo & White with the DLA and galaxy mass distributions of these simulations, we predict a bias ratio of 0.771. Direct measurement from the simulations of $w_{\rm dg}/w_{\rm gg}$ st yields a ratio of 0.73+/-0.08, in excellent agreement with that prediction. Equivalently, inverting the measured correlation ratio to infer a mean DLA halo mass yields (log. averaging, in solar units) <log(M_DLA)> =11.13+/-013, in excellent agreement with the true value in the simulations: 11.16. The cross- correlation method thus appears to yield a robust estimate of the average host halo mass even though the DLAs and the galaxies occupy a broad mass spectrum of halos, and massive halos contain multiple galaxies with DLAs. We show that the inferred mean DLA halo mass is independent of the galaxy sub-sample used, i.e. the cross-correlation technique is also reliable. Our results imply that the cross-correlation length between DLAs and LBGs is predicted to be, at most, 2.85 Mpc. Future observations will soon distinguish models in which DLAs are in low mass halos from those in which DLAs are in massive halos.
After a short introduction on how we get information of the magnetic fields from radio observations I discuss the results concerning the magnetic field structure in galaxies: Large-scale regular magnetic field pattern of spiral structure exist in grand-design spirals, flocculent and even irregular galaxies. The regular field in spirals is aligned along the optical spiral arms but strongest in the interarm region, sometimes forming 'magnetic arms'. The strongest total field is found in the optical arms, but mainly irregular. The large-scale regular field is best explained by some kind of dynamo action. Only a few galaxies show a dominant axisymmetric field pattern, most field structures seem to be a superposition of different dynamo modes or rather reveal more local effects related to density waves, bars or shocks. Observations of edge-on galaxies show that the magnetic fields are mainly parallel to the disk except in some galaxies with strong star formation and strong galactic winds as e.g. NGC 4631.
We show that, within the Quasiparticle Random Phase Approximation (QRPA) and the renormalized QRPA (RQRPA) based on the Bonn CD nucleon-nucleon interaction, the competition between the pairing and the neutron-proton particle-particle and particle-hole interactions causes contributions to the neutrinoless double-beta decay matrix element to nearly vanish at internucleon distances of more than 2 or 3 fermis. As a result, the matrix element is more sensitive to short-range/high-momentum physics than one naively expects. We analyze various ways of treating that physics and quantify the uncertainty it produces in the matrix elements, with three different treatments of short-range correlations.
We consider the passage time problem for L\'evy processes, emphasising heavy tailed cases. Results are obtained under quite mild assumptions, namely, drift to $-\infty$ a.s. of the process, possibly at a linear rate (the finite mean case), but possibly much faster (the infinite mean case), together with subexponential growth on the positive side. Local and functional versions of limit distributions are derived for the passage time itself, as well as for the position of the process just prior to passage, and the overshoot of a high level. A significant connection is made with extreme value theory via regular variation or maximum domain of attraction conditions imposed on the positive tail of the canonical measure, which are shown to be necessary for the kind of convergence behaviour we are interested in.
We study the fluctuations of systems modeled by Markov jump processes with periodic generators. We focus on observables defined through time-periodic functions of the system's states or transitions. Using large deviation theory, canonical biasing and generalized Doob transform, we characterize the asymptotic fluctuations of such observables after a large number of periods by obtaining the Markov process that produces them. We show that this process, called driven process, is the minimum under constraint of the large deviation function for occupation and jumps.
{\it Ab initio} calculation of the total cross section for the reactions $^{4}\rm{He}(\gamma,p)^3\rm{H}$ and $^{4}\rm{He}(\gamma,n)^3\rm{He}$ is presented, using state-of-the-art nuclear forces. The Lorentz integral transform (LIT) method is applied, which allows exact treatment of the final state interaction (FSI). The dynamic equations are solved using the effective interaction hyperspherical harmonics (EIHH) method. In this calculation of the cross sections the three-nucleon force is fully taken into account, except in the source term of the LIT equation for the FSI transition matrix element.
In [BS] Babson and Steingrimsson introduced generalized permutation patterns that allow the requirement that two adjacent letters in a pattern must be adjacent in the permutation.   Let $f_{\tau;r}(n)$ be the number of $1\mn3\mn2$-avoiding permutations on $n$ letters that contain exactly $r$ occurrences of $\tau$, where $\tau$ a generalized pattern on $k$ letters. Let $F_{\tau;r}(x)$ and $F_\tau(x,y)$ be the generating functions defined by $F_{\tau;r}(x)=\sum_{n\geq0} f_{\tau;r}(n)x^n$ and $F_\tau(x,y)=\sum_{r\geq0}F_{\tau;r}(x)y^r$. We find an explicit expression for $F_\tau(x,y)$ in the form of a continued fraction for where $\tau$ given as a generalized pattern; $\tau=12\mn3\mn...\mn k$, $\tau=21\mn3\mn...\mn k$, $\tau=123... k$, or $\tau=k... 321$. In particularly, we find $F_\tau(x,y)$ for any $\tau$ generalized pattern of length 3. This allows us to express $F_{\tau;r}(x)$ via Chebyshev polynomials of the second kind, and continued fractions.
There are mainly two different approaches to measure the cosmic star formation history: direct star formation rate density (SFRD) and stellar mass density rhostar as functions of redshift. Compilations of current observations seem to show a disparity in the two quantities, in the sense that the integral of SFRD is higher than the observed rhostar (after considering gas recycling). Using cosmological smoothed particle hydrodynamics simulations based on the concordance Lambda cold dark matter model, we show that the two quantities become more consistent with each other when we consider the observed galaxy mass limit. The comparison between simulations and (dust corrected) observed cosmic SFRD shows a good agreement, while the observed rhostar is significantly lower than the simulation results. This can be reconciled if the current high-$z$ galaxy surveys are missing faint low-mass galaxies due to their flux limit. Our simulated GSMFs have steep low-mass end slopes of alpha < -2 at z>3, and when these numerous low-mass galaxies are included, the total rhostar matches with the integral of SFRD.
Given a combinatorial optimization problem $\Pi$ and an increasing finite sequence $c$ of natural numbers, we obtain a cardinality constrained version $\Pi_c$ of $\Pi$ by permitting only those feasible solutions of $\Pi$ whose cardinalities are members of $c$. We are interested in polyhedra associated with those problems, in particular in inequalities that cut off solutions of forbidden cardinality. Maurras (1977) and Camion and Maurras (1982) introduced a family of inequalities, that we call forbidden set inequalities, which can be used to cut off those solutions. However, these inequalities are in general not facet defining for the polyhedron associated with $\Pi_c$. Kaibel and Stephan (2007) showed how one can combine integer characterizations for cycle and path polytopes and a modified form of forbidden set inequalities to give facet defining integer representations for the cardinality restricted versions of these polytopes. Motivated by this work, we apply the same approach on the matroid polytope. It is well known that the so-called rank inequalities together with the nonnegativity constraints provide a complete linear description of the matroid polytope (see Edmonds (1971). By essentially adding the forbidden set inequalities in an appropriate form, we obtain a complete linear description of the cardinality constrained matroid polytope which is the convex hull of the incidence vectors of those independent sets that have a feasible cardinality. Moreover, we show how the separation problem for the forbidden set inequalities can be reduced to that for the rank inequalities. We also give necessary and sufficient conditions for a forbidden set inequality to be facet defining.
We study a reversible continuous-time Markov dynamics of a discrete $(2+1)$-dimensional interface. This can be alternatively viewed as a dynamics of lozenge tilings of the $L\times L$ torus, or as a conservative dynamics for a two-dimensional system of interlaced particles. The particle interlacement constraints imply that the equilibrium measures are far from being product Bernoulli: particle correlations decay like the inverse distance squared and interface height fluctuations behave on large scales like a massless Gaussian field. We consider a particular choice of the transition rates, originally proposed in [Luby-Randall-Sinclair]: in terms of interlaced particles, a particle jump of length $n$ that preserves the interlacement constraints has rate $1/(2n)$. This dynamics presents special features: the average mutual volume between two interface configurations decreases with time and a certain one-dimensional projection of the dynamics is described by the heat equation.   In this work we prove a hydrodynamic limit: after a diffusive rescaling of time and space, the height function evolution tends as $L\to\infty$ to the solution of a non-linear parabolic PDE. The initial profile is assumed to be $C^2$ differentiable and to contain no "frozen region". The explicit form of the PDE was recently conjectured on the basis of local equilibrium considerations. In contrast with the hydrodynamic equation for the Langevin dynamics of the Ginzburg-Landau model [Funaki-Spohn,Nishikawa], here the mobility coefficient turns out to be a non-trivial function of the interface slope.
Advanced self-supervised visual representation learning methods rely on the instance discrimination (ID) pretext task. We point out that the ID task has an implicit semantic consistency (SC) assumption, which may not hold in unconstrained datasets. In this paper, we propose a novel contrastive mask prediction (CMP) task for visual representation learning and design a mask contrast (MaskCo) framework to implement the idea. MaskCo contrasts region-level features instead of view-level features, which makes it possible to identify the positive sample without any assumptions. To solve the domain gap between masked and unmasked features, we design a dedicated mask prediction head in MaskCo. This module is shown to be the key to the success of the CMP. We evaluated MaskCo on training datasets beyond ImageNet and compare its performance with MoCo V2. Results show that MaskCo achieves comparable performance with MoCo V2 using ImageNet training dataset, but demonstrates a stronger performance across a range of downstream tasks when COCO or Conceptual Captions are used for training. MaskCo provides a promising alternative to the ID-based methods for self-supervised learning in the wild.
Well-sampled optical lightcurves of 146 gamma-ray bursts (GRBs) are compiled from the literature. By empirical fitting we identify eight possible emission components and summarize the results in a "synthetic" lightcurve. Both optical flare and early shallow-decay components are likely related to long-term central engine activities. We focus on their statistical properties in this paper. Twenty-four optical flares are obtained from 19 GRBs. The isotropic R-band energy is smaller than 1% of $E_{\gamma, \rm iso}$. The relation between isotropic luminosities of the flares and gamma-rays follows $L^{\rm F}_{\rm R, iso}\propto L_{{\gamma}, \rm iso}^{1.11\pm 0.27}$. Later flares tend to be wider and dimmer, i.e., $w^{\rm F}\sim t^{\rm F}_{\rm p}/2$ and $L^{\rm F}_{\rm R, iso}\propto [t^{\rm F}_{\rm p}/(1+z)]^{-1.15\pm0.15}$. The detection probability of the optical flares is much smaller than that of X-ray flares. An optical shallow decay segment is observed in 39 GRBs. The relation between the break time and break luminosity is a power-law, with an index of $-0.78\pm 0.08$, similar to that derived from X-ray flares. The X-ray and optical breaks are usually chromatic, but a tentative correlation is found. We suggest that similar to the prompt optical emission that tracks $\gamma$-rays, the optical flares are also related to the erratic behavior of the central engine. The shallow decay component is likely related to a long-lasting spinning-down central engine or piling up of flare materials onto the blastwave. Mixing of different emission components may be the reason of the diverse chromatic afterglow behaviors.
We study a three-terminal setup consisting of a single-level quantum dot capacitively coupled to a quantum point contact. The point contact connects to a source and drain reservoirs while the quantum dot is coupled to a single base reservoir. This setup has been used to implement a noninvasive, nanoscale thermometer for the bath reservoir by detecting the current in the quantum point contact. Here, we demonstrate that the device can also be operated as a thermal transistor where the average (charge and heat) current through the quantum point contact is controlled via the temperature of the base reservoir. We characterize the performances of this device both as a transistor and a thermometer, and derive the operating condition maximizing their respective sensitivities. The present analysis is useful for the control of charge and heat flow and high precision thermometry at the nanoscale.