ShantanuT01/DACTYL-Pretraining huggingface dataset:
We present a probabilistic model built for the optical cross-match between the SRG/eROSITA X-ray sources and photometric data from the DESI Legacy Imaging Surveys. The model relies both on positional and photometric information on optical objects nearby X-ray sources and allows performing selection with precision and recall $\approx94$% (for $F_{\rm X,0.5-2}>10^{-14}$ erg/s/cm$^2$). With this model, we calibrated positional error of the SRG/eROSITA sources detected in the Lockman Hole: $\sigma_{\rm corr} = 0.87\sqrt{ \sigma_{\rm det}^{2.53} + 1.12^2}$. The model will become a part of the SRGz system for data analysis of the X-ray data obtained from the all-sky SRG/eROSITA survey.
The defect conformal field theory describing intersecting D3-branes at a C^2/Z_k orbifold is used to (de)construct the theory of intersecting M5-branes, as well as M5-branes wrapping the holomorphic curve xy=c. The possibility of a 't Hooft anomaly due to tensionless strings at the intersection is discussed. This note is based on a talk given by Zachary Guralnik at the 35th International Symposium Ahrenshoop on the Theory of Elementary Particles.
Galaxy formation models typically assume that the size and rotation speed of galaxy disks are largely dictated by the mass, concentration, and spin of their surrounding dark matter haloes. Equally important, however, are the fraction of baryons in the halo that collect into the central galaxy, as well as the net angular momentum that they are able to retain during its assembly process. We explore the latter using a set of four large cosmological N-body/gasdynamical simulations drawn from the OWLS (OverWhelmingly Large Simulations) project. These runs differ only in their implementation of feedback from supernovae. We find that, when expressed as fractions of their virial values, galaxy mass and net angular momentum are tightly correlated. Galaxy mass fractions, m_d=M_gal/M_vir, depend strongly on feedback, but only weakly on halo mass or spin over the halo mass range explored here (M_vir>1e11 h^{-1}M_sun). The angular momentum of a galaxy, j_d=J_gal/J_vir, correlates with m_d in a manner that is insensitive to feedback and that deviates strongly from the simple j_d = m_d assumption often adopted in semi-analytic models of galaxy formation. The m_d-j_d correlation implies that, in a given halo, galaxy disk size is maximal when the central galaxy makes up a substantial fraction (~20%-30%) of all baryons within the virial radius. At z=2, such systems may host gaseous disks with radial scale lengths as large as those reported for star-forming disks by the SINS survey, even in moderately massive haloes of average spin. Extended disks at z=2 may thus signal the presence of systems where galaxy formation has been particularly efficient, rather than the existence of haloes with unusually high spin parameter.
The Stieltjes classes play a significant role in the moment problem since they permit to expose an infinite family of probability distributions all having equal moments of all orders. Given a moment-indeterminate distribution, it may not be easy to indicate another distribution with the same moments. Mostly, the Stieltjes classes have been considered for absolutely continuous distributions. In this work, a new approach for constructing them in the discrete case is presented. Examples for some widely used discrete distributions are provided.
A temperature gradient applied to a ferromagnetic metal induces not only independent flows of electrons and magnons but also drag currents because of their mutual interaction. In this paper, we present a microscopic study of the electron flow induced by the drag due to magnons. The analysis is based on the $s$-$d$ model, which describes conduction electrons and magnons coupled via the $s$-$d$ exchange interaction. Magnetic impurities are introduced in the electron subsystem as a source of spin relaxation. The obtained magnon-drag electron current is proportional to the entropy of magnons and to $\alpha - \beta$ (more precisely, to $1 - \beta/\alpha$), where $\alpha$ is the Gilbert damping constant and $\beta$ is the dissipative spin-transfer torque parameter. This result almost coincides with the previous phenomenological result based on the magnonic spin-motive forces, and consists of spin-transfer and momentum-transfer contributions, but with a slight disagreement in the former. The result is interpreted in terms of the nonequilibrium spin chemical potential generated by nonequilibrium magnons.
We studied the behavior of nontrivial Dirac fermion states in an antiferromagnetic metal SmBi using angle-resolved photoemission spectroscopy (ARPES). The experimental results exhibit multiple Fermi pockets around $\overline{\Gamma}$ and $\overline{M}$ points along with a band inversion in the spectrum along the $\overline{\Gamma}$-$\overline{M}$ line consistent with the density functional theory results. In addition, ARPES data reveal Dirac cones at $\overline{\Gamma}$ and $\overline{M}$ points within the energy gap of the bulk bands. The Dirac cone at $\overline{M}$ exhibit a distinct Dirac point and is intense in the high photon energy data while the Dirac cone at $\overline{\Gamma}$ is intense at low photon energies. Employing ultra-high-resolution ARPES, we discover destruction of a Fermi surface constituted by the surface states across the Ne\'{e}l temperature of 9 K. Interestingly, the Dirac cone at $\overline{\Gamma}$ is found to be gapped at 15 K and the behavior remains similar across the magnetic transition. These results reveal complex momentum dependent gap formation and fermi surface destruction across magnetic transition in an exotic correlated topological material; the interplay between magnetism and topology in this system calls for ideas beyond existing theoretical models.
Face clustering is a promising method for annotating unlabeled face images. Recent supervised approaches have boosted the face clustering accuracy greatly, however their performance is still far from satisfactory. These methods can be roughly divided into global-based and local-based ones. Global-based methods suffer from the limitation of training data scale, while local-based ones are difficult to grasp the whole graph structure information and usually take a long time for inference. Previous approaches fail to tackle these two challenges simultaneously. To address the dilemma of large-scale training and efficient inference, we propose the STructure-AwaRe Face Clustering (STAR-FC) method. Specifically, we design a structure-preserved subgraph sampling strategy to explore the power of large-scale training data, which can increase the training data scale from ${10^{5}}$ to ${10^{7}}$. During inference, the STAR-FC performs efficient full-graph clustering with two steps: graph parsing and graph refinement. And the concept of node intimacy is introduced in the second step to mine the local structural information. The STAR-FC gets 91.97 pairwise F-score on partial MS1M within 310s which surpasses the state-of-the-arts. Furthermore, we are the first to train on very large-scale graph with 20M nodes, and achieve superior inference results on 12M testing data. Overall, as a simple and effective method, the proposed STAR-FC provides a strong baseline for large-scale face clustering. Code is available at \url{https://sstzal.github.io/STAR-FC/}.
In this note, we consider an l-isogeny descent on a pair of elliptic curves over Q. We assume that l > 3 is a prime. The main result expresses the relevant Selmer groups as kernels of simple explicit maps between finite- dimensional F_l-vector spaces defined in terms of the splitting fields of the kernels of the two isogenies. We give examples of proving the l-part of the Birch and Swinnerton-Dyer conjectural formula for certain curves of small conductor.
The maximal B_{p,q}^{s}-regularity properties of a nonlocal fractional elliptic equation is studied. Particularly, it is proven that the operator generated by this nonlocal ell{\i}p{\i}t{\i}c equation in B_{p,q}^{s} is sectorial and also is a generator of an analytic semigroup. Moreover, well-posedeness of nonlocal fractional parabolic equation in Besov spaces are established.
The MSSM predictions at the one-loop level for the weak-magnetic dipole moments of the $\tau$ lepton and the $b$ quark are analysed. The entire supersymmetric parameter space is scannedwith the usual GUT constraint and common squark and slepton mass parameters. The real part of $a^W_\tau$ is dominated by the chargino contribution, being the same order as the SM one or even larger in the high $\tan\beta$ region whereas the imaginary part, due to Higgs boson diagrams, is negligible comparedto the SM value. The real part of$a^W_b$ is controlled mainly by charginos andalso by gluinos, when the mixing in the bottom squark sector is large, to yield, for high $\tan\beta$, a contribution one order of magnitude largerthan the pure electroweak SM value but a factor five smaller than the standard QCD contribution. The imaginary part of $a^W_b$ is the same order as in the SM.
This is the part II of our series of two papers, "Clemens' conjecture: part I", "Clemens' conjecture: part II". Continuing from part I, in this paper we turn our attention to general quintic threefolds. In a universal quintic threefold X, we construct a family of quasi-regular deformation B_b such that the generic member in this family is non-deviated, but some special member is deviated. By the result from part I, this is impossible unless there is no one parameter family of smooth rational curves in a generic quintic threefold.
In a quantum gravity theory the entropy of entanglement $S$ between the fundamental degrees of freedom spatially divided by a surface is discussed. The classical gravity is considered as an emergent phenomenon and arguments are presented that: 1) $S$ is a macroscopical quantity which can be determined without knowing a real microscopical content of the fundamental theory; 2) $S$ is given by the Bekenstein-Hawking formula in terms of the area of a co-dimension 2 hypesurface $\cal B$; 3) in static space-times $\cal B$ can be defined as a minimal hypersurface of a least volume separating the system in a constant time slice. It is shown that properties of $S$ are in agreement with basic properties of the von Neumann entropy. Explicit variational formulae for $S$ in different physical examples are considered.
We present some dynamic and entropic considerations about the evolution of a continuous time quantum walk implementing the clock of an autonomous machine. On a simple model, we study in quite explicit terms the Lindblad evolution of the clocked subsystem, relating the evolution of its entropy to the spreading of the wave packet of the clock. We explore possible ways of reducing the generation of entropy in the clocked subsystem, as it amounts to a deficit in the probability of finding the target state of the computation. We are thus lead to examine the benefits of abandoning some classical prejudice about how a clocking mechanism should operate.
We discuss issues concerning the physical nature of intervening MgII quasar absorption systems in light of results from our recent surveys using SDSS EDR QSO spectra and data obtained at the MMT. These surveys indicate an excess of weak $W_0^{\lambda2796} \lesssim 0.3$\AA) systems relative to the exponential dN/dW distribution of stronger systems. The incidence of intermediate-strength lines shows remarkably little evolution with redshift, thereby constraining models for the nature of the clouds comprising these absorbers. The total distribution does evolve, with the incidence decreasing with decreasing redshift in a $W_0^{\lambda2796}$-dependent rate (the strongest systems evolve the fastest). This suggests that multiple populations that evolve at different rates contribute to the incidence in a $W_0^{\lambda2796}$-dependent manner. We also present two images of fields containing unprecedented ``ultra-strong'' ($W_0^{\lambda2796} \ge 4.0$\AA) MgII absorbers.
We study the eigenvalue problem of the squared Pauli-Lubanski vector, W^{2}, in the Spinor-Vector representation space and derive from it that the -s(s+1)m^{2} subspace with s=3/2, i.e. spin 3/2 in the rest frame, is pinned down by the one sole Klein-Gordon like equation, [ (p^{2}-m^{2})g_{\alpha\beta}-{2/3}p_{\beta}p_{\alpha}- {1/3}(p_{\alpha}\gamma_{\beta}+p_{\beta}\gamma_{\alpha})\not p +{1/3} \gamma_{\alpha}\not p \gamma_{\beta}\not p ] \psi^{\beta}=0. Upon gauging this W^{2} invariant subspace of \psi_{\mu} is shown to couple to the electromagnetic field in a fully covariant fashion already at zeroth order of 1/m and with the correct gyromagnetic factor of g_{s}=\frac{1}{s}. The gauged equation is hyperbolic and hence free from the Velo-Zwanziger problem of acausal propagation within an electromagnetic field at least to that order.
The attenuation of the intraband intensity of a superdeformed band, which results from mixing with normally deformed configurations, is calculated using reaction theory. It is found that the sharp increase of the attenuation is mostly due to the tunnelling through a spin dependent barrier and not to the chaotic nature of the normally deformed states.
Gas expulsion or gas retention is a central issue in most of the models for multiple stellar populations and light element anti-correlations in globular clusters. The success of the residual matter expulsion or its retention within young stellar clusters has also a fundamental importance in order to understand how star formation proceeds in present-day and ancient star-forming galaxies and if proto-globular clusters with multiple stellar populations are formed in the present epoch. It is usually suggested that either the residual gas is rapidly ejected from star-forming clouds by stellar winds and supernova explosions, or that the enrichment of the residual gas and the formation of the second stellar generation occur so rapidly, that the negative stellar feedback is not significant. Here we continue our study of the early development of star clusters in the extreme environments and discuss the restrictions that strong radiative cooling and stellar mass segregation provide on the gas expulsion from dense star-forming clouds. A large range of physical initial conditions in star-forming clouds which include the star-forming cloud mass, compactness, gas metallicity, star formation efficiency and effects of massive stars segregation are discussed. It is shown that in sufficiently massive and compact clusters hot shocked winds around individual massive stars may cool before merging with their neighbors. This dramatically reduces the negative stellar feedback, prevents the development of the global star cluster wind and expulsion of the residual and the processed matter into the ambient interstellar medium. The critical lines which separate the gas expulsion and the gas retention regimes are obtained.
The de Bruijn-Tengbergen-Kruyswijk (BTK) construction is a simple algorithm that produces an explicit symmetric chain decomposition of a product of chains. We linearize the BTK algorithm and show that it produces an explicit symmetric Jordan basis (SJB). In the special case of a Boolean algebra the resulting SJB is orthogonal with respect to the standard inner product and, moreover, we can write down an explicit formula for the ratio of the lengths of the successive vectors in these chains (i.e., the singular values). This yields a new, constructive proof of the explicit block diagonalization of the Terwilliger algebra of the binary Hamming scheme. We also give a representation theoretic characterization of this basis that explains its orthogonality, namely, that it is the canonically defined (upto scalars) symmetric Gelfand-Tsetlin basis.
The statistics of gravitational arcs in galaxy clusters is a powerful probe of cluster structure and may provide complementary cosmological constraints. Despite recent progresses, discrepancies still remain among modelling and observations of arc abundance, specially regarding the redshift distribution of strong lensing clusters. Besides, fast "semi-analytic" methods still have to incorporate the success obtained with simulations. In this paper we discuss the contribution of the magnification in gravitational arc statistics. Although lensing conserves surface brightness, the magnification increases the signal-to-noise ratio of the arcs, enhancing their detectability. We present an approach to include this and other observational effects in semi-analytic calculations for arc statistics. The cross section for arc formation ({\sigma}) is computed through a semi-analytic method based on the ratio of the eigenvalues of the magnification tensor. Using this approach we obtained the scaling of {\sigma} with respect to the magnification, and other parameters, allowing for a fast computation of the cross section. We apply this method to evaluate the expected number of arcs per cluster using an elliptical Navarro--Frenk--White matter distribution. Our results show that the magnification has a strong effect on the arc abundance, enhancing the fraction of arcs, moving the peak of the arc fraction to higher redshifts, and softening its decrease at high redshifts. We argue that the effect of magnification should be included in arc statistics modelling and that it could help to reconcile arcs statistics predictions with the observational data.
We report small-scale clustering measurements from the PRIMUS spectroscopic redshift survey as a function of color and luminosity. We measure the real-space cross-correlations between 62,106 primary galaxies with PRIMUS redshifts and a tracer population of 545,000 photometric galaxies over redshifts from z=0.2 to z=1. We separately fit a power-law model in redshift and luminosity to each of three independent color-selected samples of galaxies. We report clustering amplitudes at fiducial values of z=0.5 and L=1.5 L*. The clustering of the red galaxies is ~3 times as strong as that of the blue galaxies and ~1.5 as strong as that of the green galaxies. We also find that the luminosity dependence of the clustering is strongly dependent on physical scale, with greater luminosity dependence being found between r=0.0625 Mpc/h and r=0.25 Mpc/h, compared to the r=0.5 Mpc/h to r=2 Mpc/h range. Moreover, over a range of two orders of magnitude in luminosity, a single power-law fit to the luminosity dependence is not sufficient to explain the increase in clustering at both the bright and faint ends at the smaller scales. We argue that luminosity-dependent clustering at small scales is a necessary component of galaxy-halo occupation models for blue, star-forming galaxies as well as for red, quenched galaxies.
The two dimensional analog of the Hadamard state condition is used to specify the local Hadamard states associated with a linear quantum field coupled to a two dimensional gravitational background. To characterize a local Hadamard state corresponding to a physical vacuum state, we apply a superselection rule in which the state dependent part of the two-point function is determined in terms of a dynamical scalar field. It implies a basic connection between the vacuum state and a scalar field coupled to gravity. We study the characteristics of the Hadamard vacuum state through this superselection rule using two different background metrics, the two dimensional analog of the schwarzschild and FRW metric.
In this paper we calculate charge fluctuations of a Schwarzschild black-hole of mass $M$ confined within a perfectly reflecting cavity of radius R in thermal equilibrium with various species of radiation and fermions . Charge conservation is constrained by a Lagrange multiplier (the chemical potential). Black hole charge fluctuations are expected owing to continuous absorption and emission of particles by the black hole. For black holes much more massive than $10^{16} g$ , these fluctuations are exponentially suppressed. For black holes lighter than this, the Schwarzschild black hole is unstable under charge fluctuations for almost every possible size of the confining vessel. The stability regime and the fluctuations are calculated through the second derivative of the entropy with respect to the charge. The expression obtained contains many puzzling terms besides the expected thermodynamical fluctuations: terms corresponding to instabilities that do not depend on the specific value of charge of the charge carriers and one of them depends on Newton's constant instead. One of the contributions to the charge fluctuations $\hbar/4\pi$ does not depend neither on number of species, nor on the the specific charge or even the size of the confining vessel. As a matter of fact, this term emerges from the second derivative of the black hole entropy alone, which means that it corresponds to a genuine quantum mechanical property of the black hole itself. Such a contribution would cause the event horizon to recede from $2M$ to $2M-T_{BH}$ or equivalently, by $(4\pi)^{-1}$ of the black hole' s Compton wave length. Similarly, a Cauchy horizon emerges at the same distance the event horizon receded.
Massive spectroscopic redshift surveys open a promising window to accurately measure peculiar velocity at cosmological distances through redshift space distortion (RSD). In paper I of this series of work we proposed to decompose peculiar velocity into three eigen-modes (v_\delta, v_S and v_B) in order to facilitate the RSD modeling and peculiar velocity reconstruction. In the current paper we measure the dark matter RSD related statistics of the velocity eigen-modes through a set of N-body simulations, including the velocity power spectra, correlation functions, one-point probability distribution functions, cumulants and the damping functions describing the Finger of God effect. (1) The power spectrum measurement shows that these velocity components have distinctly different spatial distribution and redshift evolution. In particular, we measure the window function \tilde{W}(k,z), which describes the impact of nonlinear evolution on the v_\delta-density relation. We confirm that it can induce a significant systematic error of O(10%) in RSD cosmology. We demonstrate that \tilde{W} can be accurately described by a simple fitting formula with one or two free parameters. (2) The correlation function measurement shows that the correlation length is O(100), O(10) and O(1) Mpc for v_\delta, v_S and v_B respectively. These correlation lengths determine where we can treat the velocity fields as spatially uncorrelated. (3) The velocity PDFs and cumulants quantify non-Gaussianities of the velocity fields. We confirm speculation in paper I that v_\delta is largely Gaussian, nevertheless with non-negligible non-Gaussianity, v_B is significantly non-Gaussian. We also measure the damping functions. Despite the observed non-Gaussianities, the damping functions and hence the FOG effect are all well approximated as Gaussian ones at scales of interest.
Aggregation and fragmentation of single molecules in the cell environment lead to a spectrum of diffusivities and to statistical laws of movement very different from typical Brownian motion. Current models of intracellular transport do not explain at a microscopical level the emergence of theses deviations. Employing a many body approach, which we call the Hitchhiker model, we elucidate how the widely observed exponential tails in the particle spreading, i.e. the Laplace distribution and the modulations of the diffusivities, are controlled by size fluctuations of single molecules. By means of numerical simulations Laplace distributions are obtained whether we track one molecule or many molecules in parallel. However, we show that the diffusivity varies significantly depending on which tracking protocol is applied. Using a renewal process in the space of sizes, we quantify to what extent the average diffusivity in the single molecule technique is decreased compared with the ensemble average.