ShantanuT01/DACTYL-Pretraining huggingface dataset:
Fast radio bursts (FRBs) are one of the most exciting new mysteries of astrophysics. Their origin is still unknown, but recent observations seems to link them to Soft Gamma Repeaters and, in particular, to magnetar giant flares (MGFs). The recent detection of a MGF at GeV energies by the \textit{Fermi} Large Area Telescope (LAT) motivated the search for GeV counterparts to the >100 currently known FRBs. Taking advantage of more than 12 years of \textit{Fermi}-LAT data, we perform a search for gamma-ray emission from all the reported repeating and non-repeating FRBs. We analyse on different-time scales the \textit{Fermi}-LAT data of each individual source separately, including a cumulative analysis on the repeating ones. In addition, we perform the first stacking analysis at GeV energies of this class of sources in order to constrain the gamma-ray properties of the FRBs that are undetected at high energies. The stacking analysis is a powerful method that allow a possible detection from below-threshold FRBs providing important information on these objects. In this talk we present the preliminary results of our study and we discuss their implications for the predictions of gamma-ray emission from this class of sources
Mesons are made of quark-antiquark pairs held together by the strong force. The one channel spectator, Dirac, and Salpeter equations can each be used to model this pairing. We look at cases where the relativistic kernel of these equations corresponds to a time-like vector exchange, a scalar exchange, or a linear combination of the two. Since the model used in this paper describes mesons which cannot decay physically, the equations must describe stable states. We find that this requirement is not always satisfied, and give a complete discussion of the conditions under which the various equations give unphysical, unstable solutions.
Background: Nuclear self-consistent mean-field approaches are rooted in the density functional theory and, through the spontaneous symmetry breaking mechanism, allow for including important correlations, while keeping the simplicity of the approach. Because real ground states should have all symmetries of the nuclear Hamiltonian, these methods require subsequent symmetry restoration.   Purpose: We implement and study Lipkin method of approximate variation after projection applied to the restoration of the translational or rotational symmetries.   Methods: We use Lipkin operators up to quadratic terms in momenta or angular momenta with self-consistently determined values of the Peierls-Yoccoz translational masses or moments of inertia, respectively. Calculations based on Skyrme energy-density functional are performed for heavy, deformed, and paired nuclei.   Results: In deformed nuclei, the Peierls-Yoccoz translational masses along three different principal-axes directions of the intrinsic system can be different, which illustrates different widths of the total-momentum distributions. Numerically, the differences are only of the order of a few per cent. For the rotational-symmetry restoration, the Lipkin method compares favorably with the exact angular-momentum projection, which requires much larger computational effort.   Conclusions: The Lipkin method of translational and rotational symmetry restoration is a practical low-cost method of determining the corresponding correlation energies. It allows for a simultaneous restoration of several symmetries and can be relatively easily implemented in the standard self-consistent mean-field calculations, including those required for the parameter adjustments.
An experiment is proposed in which the overall path taken by a photon is indicated by the timing of a twin herald photon, while a particular segment of that path is determined by interference. The experiment is to be carried out in two parts. In the first, coincident pairs of photons generated by type I spontaneous- parametric-down-conversion are diffracted by a large-width grating to increase the coherence length of their associated waves, and to produce two sources of coincident photons. Upon experimental confirmation that coincidences have been maintained, one of the sources is used to furnish timing heralds, and the other to send photons to an unequal path interferometer. A photon path through the interferometer via the short arm is indicated by count synchronization with the herald. The exit output port used and final detection location are determined by the phase in the long arm. If output port usage can thus be controlled by the phase in the photon free arm, the path of the photon as particle will have been controlled by interference with an accompanying photon-empty wave.
This paper provides a detailed description for the asymptotics of exponential functionals of random walks with light/heavy tails. We give the convergence rate based on the key observation that the asymptotics depends on the simple paths with either slowly decreasing local minimum or final value below a low level. Also, our careful analysis of the interrelationship between the local minimum and the final value provides the exact expression of the limiting coefficient in terms of some transformations of the random walk.
We propose a formalism for calculating the event cross-section of parton interactions. In this formalism, we use the light-front bound-state wave function to expand scattering initial state. This leads to an expression of the cross-section in terms of square of wave functions which can be used to define the parton distribution functions. The probability interpretation of the partonic interactions among hadron-hadron scattering is naturally achieved. We apply this formalism to calculate the 4-particle final state cross-section for single parton, double parton and gluon splitting interactions. We compare the behaviors of these cross sections and propose a method for experiments to differentiate these interactions.
We use gauge theory/string theory correspondence to study finite temperature critical behaviour of mass deformed N=4 SU(N) supersymmetric Yang-Mills theory at strong coupling, also known as N=2* gauge theory. For certain range of the mass parameters, N=2* plasma undergoes a second-order phase transition. We compute all the static critical exponents of the model and demonstrate that the transition is of the mean-field theory type. We show that the dynamical critical exponent of the model is z=0, with multiple hydrodynamic relaxation rates at criticality. We point out that the dynamical critical phenomena in N=2* plasma is outside the dynamical universality classes established by Hohenberg and Halperin.
Optical spectroscopy of the blue star KIC 10449976 shows that it is an extremely helium-rich subdwarf with effective temperature T=40000+/-300 K and surface gravity log g=5.3+/-0.1. Radial-velocity measurements over a five-day timescale show an upper variability limit of ~50+/-20 km/s. Kepler photometry of KIC 10449976 in both long and short cadence modes shows evidence for a periodic modulation on a timescale of ~3.9 days. We have examined the possibility that this modulation is not astrophysical but conclude it is most likely real. We discuss whether the modulation could be caused by a low-mass companion, by stellar pulsations, or by spots. The identification of any one of these as cause has important consequences for understanding the origin of helium-rich subdwarfs.
We address the problem of the energy conditions in modified gravity taking into account the additional degrees of freedom related to scalar fields and curvature invariants. The latter are usually interpreted as generalized {\it geometrical fluids} that differ in meaning with respect to the matter fluids generally considered as sources of the field equations. In extended gravity theories the curvature terms are encapsulated in a tensor $H^{ab}$ and a coupling $g(\Psi^i)$ that can be recast as effective Einstein field equations, with corrections to the energy-momentum tensor of matter. The formal validity of standard energy inequalities does not assure basic requirements such as the attractive nature of gravity, so we argue that the energy conditions have to be considered in a wider sense.
The hole-doped kagome lattice of Cu2+ ions in LaCuO2.66 was investigated by nuclear quadrupole resonance (NQR), electron spin resonance (ESR), electrical resistivity, bulk magnetization and specific heat measurements. For temperatures above ~180 K, the spin and charge properties show an activated behavior suggestive of a narrow-gap semiconductor. At lower temperatures, the results indicate an insulating ground state which may or may not be charge ordered. While the frustrated spins in remaining patches of the original kagome lattice might not be directly detected here, the observation of coexisting non-magnetic sites, free spins and frozen moments reveals an intrinsically inhomogeneous magnetism. Numerical simulations of a 1/3-diluted kagome lattice rationalize this magnetic state in terms of a heterogeneous distribution of cluster sizes and morphologies near the site-percolation threshold.
We study certain classes of equations for $F_q$-linear functions, which are the natural function field counterparts of linear ordinary differential equations. It is shown that, in contrast to both classical and $p$-adic cases, formal power series solutions have positive radii of convergence near a singular point of an equation. Algebraic properties of the ring of $F_q$-linear differential operators are also studied.
We report on the recent results of the hypercentral Constituent Quark Model (hCQM). The model contains a spin independent three-quark interaction which is inspired by Lattice QCD calculations and reproduces the average energy values of the SU(6) multiplets. The splittings within each multiplet are obtained with a SU(6)-breaking interaction, which can include also an isospin dependent term. All the 3- and 4-stars resonances are well reproduced. Moreover, as all the Constituent Quark models, the hCQM predicts ``missing'' resonances ({\em e.g.} extra $S11$ and $P13$ states) which can be of some help for the experimental identification of new resonances. The model provides also a good description of the medium $Q^2$-behavior of the electromagnetic transition form factors. In particular the calculated helicity amplitude $A_{{1/2}}$ for the $S_{11}(1535)$ resonance agrees very well with the recent CLAS data. More recently, the elastic nucleon form factors have been calculated using a relativistic version of the hCQM and a relativistic quark current.
We study long-term thermal evolution of neutron stars in soft X-ray transients (SXTs), taking the deep crustal heating into account consistently with the changes of the composition of the crust. We collect observational estimates of average accretion rates and thermal luminosities of such neutron stars and compare the theory with observations. We perform simulations of thermal evolution of accreting neutron stars, considering the gradual replacement of the original nonaccreted crust by the reprocessed accreted matter, the neutrino and photon energy losses, and the deep crustal heating due to nuclear reactions in the accreted crust. We test and compare results for different modern theoretical models. We update a compilation of the observational estimates of the thermal luminosities in quiescence and average accretion rates in the SXTs and compare the observational estimates with the theoretical results. Long-term thermal evolution of transiently accreting neutron stars is nonmonotonic. The quasi-equilibrium temperature in quiescence reaches a minimum and then increases toward the final steady state. The quasi-equilibrium thermal luminosity of a neutron star in an SXT can be substantially lower at the minimum than in the final state. This enlarges the range of possibilities for theoretical interpretation of observations of such neutron stars. The updates of the theory and observations leave unchanged the previous conclusions that the direct Urca process operates in relatively cold neutron stars and that an accreted heat-blanketing envelope is likely present in relatively hot neutron stars in the SXTs in quiescence. The results of the comparison of theory with observations favor suppression of the triplet pairing type of nucleon superfluidity in the neutron-star matter.
We present additional evidence that dust is really forming along the red giant branch (RGB) of 47 Tuc at luminosities ranging from above the horizontal branch to the RGB-tip (Origlia et al. 2007). The presence of dust had been inferred from an infrared excess in the (K-8) color, with K measured from high spatial resolution ground based near-IR photometry and "8" referring to Spitzer-IRAC 8 micron photometry. We show how (K-8) is a far more sensitive diagnostic for detecting tiny circumstellar envelopes around warm giants than colors using only the Spitzer-IRAC bands, for example the (3.6-8) color used by Boyer et al. (2010). In addition, we also show high resolution HST-ACS I band images of the giant stars which have (K-8) color excess. These images clearly demonstrate that Boyer et al (2010) statement that our detections of color excess associated with stars below the RGB-tip arise from blends and artefacts is simply not valid.
We consider rigidly-rotating thermal states of a massless Klein-Gordon field enclosed within a cylindrical boundary, where Robin boundary conditions (RBCs) are imposed. The connection between the parameter of the RBCs and the energy density and four-velocity expressed in the Landau frame is revealed.
General conditions for the occurrence of mesoscopic phase fluctuations in condensed matter are considered. The description of different thermodynamic phases, which coexist as a mixture of mesoscopically separated regions, is based on the {\it theory of heterophase fluctuations}. The spaces of states, typical of the related phases, are characterized by {\it weighted Hilbert spaces}. Several models illustrate the main features of heterophase condensed matter.
We study the possibility to extract the multipolar moments of an underlying distribution from a set of cosmic rays observed with non-uniform or even partial sky coverage. We show that if the degree is assumed to be upper bounded by $L$, each multipolar moment can be recovered whatever the coverage, but with a variance increasing exponentially with the bound $L$ if the coverage is zero somewhere. Despite this limitation, we show the possibility to test predictions of a model without any assumption on $L$ by building an estimate of the covariance matrix seen through the exposure function.
Image-based age estimation aims to predict a person's age from facial images. It is used in a variety of real-world applications. Although end-to-end deep models have achieved impressive results for age estimation on benchmark datasets, their performance in-the-wild still leaves much room for improvement due to the challenges caused by large variations in head pose, facial expressions, and occlusions. To address this issue, we propose a simple yet effective method to explicitly incorporate facial semantics into age estimation, so that the model would learn to correctly focus on the most informative facial components from unaligned facial images regardless of head pose and non-rigid deformation. To this end, we design a face parsing-based network to learn semantic information at different scales and a novel face parsing attention module to leverage these semantic features for age estimation. To evaluate our method on in-the-wild data, we also introduce a new challenging large-scale benchmark called IMDB-Clean. This dataset is created by semi-automatically cleaning the noisy IMDB-WIKI dataset using a constrained clustering method. Through comprehensive experiment on IMDB-Clean and other benchmark datasets, under both intra-dataset and cross-dataset evaluation protocols, we show that our method consistently outperforms all existing age estimation methods and achieves a new state-of-the-art performance. To the best of our knowledge, our work presents the first attempt of leveraging face parsing attention to achieve semantic-aware age estimation, which may be inspiring to other high level facial analysis tasks. Code and data are available on \url{https://github.com/ibug-group/fpage}.
Yurova \cite{Yu} and Anashin et al. \cite{AKY1, AKY2} characterize the ergodicity of a 1-Lipschitz function on $\Z_2$ in terms of the van der Put expansion. Motivated by their recent work, we provide the sufficient conditions for the ergodicity of such a function defined on a more general setting $\Z_p$.   In addition, we provide alternative proofs of two criteria (because of \cite{AKY1, AKY2} and \cite{Yu}) for an ergodic 1-Lipschitz function on $\Z_2,$ represented by both the Mahler basis and the van der Put basis.
The longstanding problem of characterization of the $0^+_2$ states in Gd isotopes is revisited by adopting the Nilsson$+$BCS mean field and the random-phase approximation. The interband electric quadrupole transition strengths varying almost two orders of magnitude are nicely reproduced at the same time as other observables. These results indicate that the $0^+_2$ states, in particular, those in lighter isotopes are well described as $\beta$ vibrations excited on top of deformed ground states without recourse to the shape-coexistence picture.
The attenuation of fringe contrast in a Ramsey interferometer induced by the atom-field interaction is analyzed. We show that short-time power series expansion is not the proper tool to find the relevant time scale for such process. Analytical expressions to quantify the relevant time scale for the fringe contrast decay and to characterize the long-term effectiveness of this process are proposed. For Pegg-Barnett phase state initial conditions, these expressions suggest that: the increase of the energy of the field leads to slower vanishing of fringe contrast; the increase of the field photon number variance leads to more effective attenuation in the final regime. Numerical simulations with coherent and thermal initial states are in qualitative agreement with such results.
The local environment is ideal for searching out compact dark structures via the microlensing and multi-frequency emissions as these objects are expected to be faint and microlensing experiments have already hinted at their possibility. In the case that these objects are composed of Dark Matter (DM) then there are both few limits on their abundance but many consequences of their existence or non-existence on both local and cosmic scales. In this work we examine the possibility of Ultra-Compact Mini-Halos (UCMHs) formed in the early universe. These objects can persist to the present epoch due to their large central density inuring them to the worst effects of later tidal stripping. As such, these objects could constitute probes of many details of early universe physics, such as primordial phase-transitions, inflation, small scale exploration of the primordial density perturbation field and non-Gaussianity of these density perturbations. The fact that they are also highly dark matter-dominated objects means that they are attractive objects of study in the continuing hunt for the nature of Dark Matter (DM) through indirect detection. Another reason to study such objects in the local environment is found in the conjecture that encounters with UCMHs could induce catastrophic events on planets within our solar system, e.g. mass-extinction events on Earth. We will outline a strategy for multi-frequency UCMH searches within the region of the Milky-Way in which Gaia can accurately reconstruct microlens masses. This methodology ensures that any candidate UCMH DM emission should correlate to some unidentified microlensing object with determinable mass and demonstrate that large-scale volcanic extinctions on Earth due to UCMHs are unlikely but that it is possible for loss of the Martian geodynamo to be driven encounters with such compact objects.
We introduce a differential equation for star formation in galaxies that incorporates negative feedback with a delay. When the feedback is instantaneous, solutions approach a self-limiting equilibrium state. When there is a delay, even though the feedback is negative, the solutions can exhibit cyclic and episodic solutions. We find that periodic or episodic star formation only occurs when two conditions are satisfied. Firstly the delay timescale must exceed a cloud consumption timescale. Secondly the feedback must be strong. This statement is quantitatively equivalent to requiring that the timescale to approach equilibrium be greater than approximately twice the cloud consumption timescale. The period of oscillations predicted is approximately 4 times the delay timescale. The amplitude of the oscillations increases with both feedback strength and delay time.   We discuss applications of the delay differential equation (DDE) model to star formation in galaxies using the cloud density as a variable. The DDE model is most applicable to systems that recycle gas and only slowly remove gas from the system. We propose likely delay mechanisms based on the requirement that the delay time is related to the observationally estimated time between episodic events. The proposed delay timescale accounting for episodic star formation in galaxy centers on periods similar to P 10 Myrs, irregular galaxies with P 100 Myrs, and the Milky Way disk with P~ 2Gyr, could be that for exciting turbulence following creation of massive stars, that for gas pushed into the halo to return and interact with the disk and that for spiral density wave evolution, respectively.
We report high-resolution optical absorption spectra for NdFe3(BO3)4 trigonal single crystal which is known to exhibit a giant magnetoelectric effect below the temperature of magnetic ordering TN = 33 K. The analysis of the temperature-dependent polarized spectra reveals the energies and, in some cases, symmetries and exchange splittings of Nd3+ 84 Kramers doublets. We perform crystal-field calculations starting from the exchange-charge model, obtain a set of six real crystal-field parameters, and calculate wave functions and magnetic g-factors. In particular, the values g(perpendicular) = 2.385, g(parallel) = 1.376 were found for the Nd3+ ground-state doublet. We obtain Bloc=7.88 T and |JFN|= 0.48 K for the values of the local effective magnetic field at liquid helium temperatures at the Nd3+ site and the Nd - Fe exchange integral, respectively, using the experimentally measured Nd3+ ground-state splitting of 8.8 cm-1. To check reliability of our set of crystal field parameters we model the magnetic susceptibility data from literature. A dimer containing two nearest-neighbor iron ions in the spiral chain is considered to partly account for quasi-one-dimensional properties of iron borates, and then the mean-field approximation is used. The results of calculations with the exchange parameters for Fe3+ ions Jnn = -6.25 K (intra-chain interactions) and Jnnn = -1.92 K (inter-chain interactions) obtained from fitting agree well with the experimental data.