ShantanuT01/DACTYL-Pretraining huggingface dataset:
We give improved estimates for the non-perturbative parameters appearing in the heavy quark expansion for inclusive decays. While the parameters appearing in low orders of this expansion can be extracted from data, the number of parameters in higher orders proliferates strongly, making a determination of these parameters from data impossible. Thus, one has to rely on theoretical estimates which may be obtained from an insertion of intermediate states. In this paper we refine this method and attempt to estimate the uncertainties of this approach.
In this paper, a theoretical journey from electronic to magneto-caloric effect has been shown through the magnetic properties of aluminium induced yttrium chromate. The ground state electronic band structure and density of states have been studied using first principle calculations under GGA+U schemes. From the energy minimization, the ferromagnetic structure is more stable than the antiferromagnetic one. The interaction constant as well as the magnetic moment, have been determined from mean-field theory and DFT, respectively. The Monte-Carlo simulation under Metropolis algorithm has been employed to determine the critical temperature ($T_C$), which is nearly same as the experimental value. The temperature-dependent magnetization shows that these materials exhibit a paramagnetic to ferromagnetic phase transition at ~136 K, 130 K, 110 K, and 75 K respectively. The two inherent properties named the isothermal entropy change ($\Delta S_M$) and the adiabatic temperature change ($\Delta T_{ad}$) as a function of temperature for different applied magnetic fields have been determined to measure the magnetocaloric efficiency of these materials. The relative cooling power (RCP), which is calculated around $T_C$, changes from 4.7 J/Kg to 2.5 J/Kg with the decreasing Cr-concentration.
We withdraw our paper for one doubt on one of equations .Due to this reason we will check again our calculation and replace the revised version of this paper.
We find a full strongly exceptional collection for the Cayley plane OP2, the simplest rational homogeneous space of the exceptional group E6. This collection, closely related to the one given by the second author in [J. Algebra, 330:177-187, 2011], consists of 27 vector bundles which are homogeneous for the group E6, and is a Lefschetz collection with respect to the minimal equivariant embedding of OP2.
VERITAS is an array of Imaging Atmospheric Cherenkov Telescopes designed for very high energy gamma ray (E>100,GeV) observations of astrophysical sources.   The experiment began its scientific observation program in the 2006/2007 observing season. We describe here the analysis chain for reducing the data, reconstructing the direction and energy of incident gamma rays and the rejection of background cosmic rays.
Proton-neutron, neutron-neutron and proton-proton momentum correlation functions ($C_{pn}$, $C_{nn}$, $C_{pp}$) are systematically investigated for $^{15}$C and other C isotopes induced collisions at different entrance channel conditions within the framework of the isospin-dependent quantum molecular dynamics (IDQMD) model complemented by the CRAB (correlation after burner) computation code. $^{15}$C is a prime exotic nucleus candidate due to the weakly bound valence neutron coupling with closed-neutron shell nucleus $^{14}$C. In order to study density dependence of correlation function by removing the isospin effect, the initialized $^{15}$C projectiles are sampled from two kinds of density distribution from RMF model, in which the valence neutron of $^{15}$C is populated on both 1$d$5/2 and 2$s$1/2 states, respectively. The results show that the density distributions of valence neutron significantly influence nucleon-nucleon momentum correlation function at large impact parameter and high incident energy. The extended density distribution of valence neutron largely weakens the strength of correlation function. The size of emission source is extracted by fitting correlation function using Gaussian source method. The emission source size as well as the size of final state phase space is larger for projectiles sampling from more extended density distribution of valence neutron corresponding 2$s$1/2 state in RMF model. Therefore momentum correlation function can be considered as a potential valuable tool to diagnose the exotic nuclear structure such as skin and halo.
We study the continuous resonant (CR) equation which was derived by Faou-Germain-Hani as the large-box limit of the cubic nonlinear Schr\"odinger equation in the small nonlinearity (or small data) regime. We first show that the system arises in another natural way, as it also corresponds to the resonant cubic Hermite-Schr\"odinger equation (NLS with harmonic trapping). We then establish that the basis of special Hermite functions is well suited to its analysis, and uncover more of the striking structure of the equation. We study in particular the dynamics on a few invariant subspaces: eigenspaces of the harmonic oscillator, of the rotation operator, and the Bargmann-Fock space. We focus on stationary waves and their stability.
Seeking the convex hull of an object is a very fundamental problem arising from various tasks. In this work, we propose two variational convex hull models using level set representation for 2-dimensional data. The first one is an exact model, which can get the convex hull of one or multiple objects. In this model, the convex hull is characterized by the zero sublevel-set of a convex level set function, which is non-positive at every given point. By minimizing the area of the zero sublevel-set, we can find the desired convex hull. The second one is intended to get convex hull of objects with outliers. Instead of requiring all the given points are included, this model penalizes the distance from each given point to the zero sublevel-set. Literature methods are not able to handle outliers. For the solution of these models, we develop efficient numerical schemes using alternating direction method of multipliers. Numerical examples are given to demonstrate the advantages of the proposed methods.
We investigate the light variations of 15 Am stars using four years of high-precision photometry from the Kepler spacecraft and an additional 14 Am stars from the K2 Campaign 0 field. We find that most of the Am stars in the Kepler field have light curves characteristic of rotational modulation due to star spots. Of the 29 Am stars observed, 12 are {\delta} Scuti variables and one is a {\gamma} Doradus star. One star is an eclipsing binary and another was found to be a binary from time-delay measurements. Two Am stars show evidence for flares which are unlikely to be due to a cool companion. The fact that 10 out of 29 Am stars are rotational variables and that some may even flare strongly suggests that Am stars possess significant magnetic fields. This is contrary to the current understanding that the enhanced metallicity in these stars is due to diffusion in the absence of a magnetic field. The fact that so many stars are {\delta} Scuti variables is also at odds with the prediction of diffusion theory. We suggest that a viable alternative is that the metal enhancement could arise from accretion.
We analyze the hadronic and radiative decay modes of the recently observed $D_{sJ}(2317)$ meson, in the hypothesis that it can be identifield with the scalar $s_\ell^P={1\over 2}^+$ state of $c \bar s$ spectrum ($D_{s0}$). The method is based on heavy quark symmetries and Vector Meson Dominance ansatz. We find that the hadronic isospin violating mode $D_{s0} \to D_s \pi^0$ is enhanced with respect to the radiative mode $D_{s0} \to D_s^* \gamma$. The estimated width of the meson is   $\Gamma(D_{s0})\simeq 7$ KeV.
We theoretically study the scattering of spin waves from a sharp domain wall in an antiferromagnetic spin chain. While the continuum model for an antiferromagnetic material yields the well-known result that spin waves can pass through a wide domain wall with no reflection, here we show that, based on the discrete spin Hamiltonian, spin waves are generally reflected by a domain wall with a reflection coefficient that increases as the domain-wall width decreases. Remarkably, we find that, in the interesting case of an atomically sharp domain wall, the reflection of spin waves exhibits strong dependence on the state of circular polarization of the spin waves, leading to mainly reflection for one polarization while permitting partial transmission for the other, thus realizing an atomic-scale spin-wave polarizer. The polarization of the transmitted spin wave depends on the orientation of the spin in the sharp domain wall, which can be controlled by an external field or spin torque. Our utilization of a sharp antiferromagnetic domain wall as an atomic-scale spin-wave polarizer leads us to envision that ultra-small magnetic solitons such as domain walls and skyrmions may enable realizations of atomic-scale spin-wave scatterers with useful functionalities.
We use the so-called eikonal approximation, recently introduced in the context of cosmological perturbation theory, to compute power spectra for multi-component fluids. We demonstrate that, at any given order in standard perturbation theory, multipoint power spectra do not depend on the large-scale adiabatic modes. Moreover, we employ perturbation theories to decipher how nonadiabatic modes, such as a relative velocity between two different components, damp the small-scale matter power spectrum, a mechanism recently described in the literature. In particular, we do an explicit calculation at 1-loop order of this effect. While the 1-loop result eventually breaks down, we show how the damping effect can be fully captured by the help of the eikonal approximation. A relative velocity not only induces mode damping but also creates large-scale anisotropic modulations of the matter power spectrum amplitude. We illustrate this for the Local Group environment.
We are interested in the normal class of an algebraic hypersurface Z of the complex projective space P^n, that is the number of normal lines to Z passing through a generic point of P^n. Thanks to the notion of normal polar, we state a formula for the normal class valid for a general hypersurface Z of P^n. We give a generic result and we illustrate our formula with examples in P^n. We define the orthogonal indidence variety and compute the Schubert class of the variety of projective normal lines to a surface of P^3 in the Show ring of G(1,3). We complete our work with a generalization of Salmon's formula for the normal class of a Plucker curve to any planar curve with any kind of singularity.
We study the signature change in a perfect fluid Friedmann-Robertson-Walker quantum cosmological model. In this work the Schutz's variational formalism is applied to recover the notion of time. This gives rise to a Schrodinger-Wheeler-DeWitt equation with arbitrary ordering for the scale factor. We use the eigenfunctions in order to construct wave packets and evaluate the time-dependent expectation value of the scale factor which coincides with the ontological interpretation. We show that these solutions exhibit signature transitions from a finite Euclidean to a Lorentzian domain. Moreover, such models are equivalent to a classical system where, besides the perfect fluid, a repulsive fluid is present.
We examine the gravitational collapse of sphaleron type configurations in Einstein--Yang--Mills--Higgs theory. Working in spherical symmetry, we investigate the critical behavior in this model. We provide evidence that for various initial configurations, there can be three different critical transitions between possible endstates with different critical solutions sitting on the threshold between these outcomes. In addition, we show that within the dispersive and black hole regimes, there are new possible endstates, namely a stable, regular sphaleron and a stable, hairy black hole.
We show with some examples how to prove some Ramanujan-type series for $1/\pi$ in an elementary way by using terminating identities.
Recently the sparse representation based classification (SRC) has been proposed for robust face recognition (FR). In SRC, the testing image is coded as a sparse linear combination of the training samples, and the representation fidelity is measured by the l2-norm or l1-norm of the coding residual. Such a sparse coding model assumes that the coding residual follows Gaussian or Laplacian distribution, which may not be effective enough to describe the coding residual in practical FR systems. Meanwhile, the sparsity constraint on the coding coefficients makes SRC's computational cost very high. In this paper, we propose a new face coding model, namely regularized robust coding (RRC), which could robustly regress a given signal with regularized regression coefficients. By assuming that the coding residual and the coding coefficient are respectively independent and identically distributed, the RRC seeks for a maximum a posterior solution of the coding problem. An iteratively reweighted regularized robust coding (IR3C) algorithm is proposed to solve the RRC model efficiently. Extensive experiments on representative face databases demonstrate that the RRC is much more effective and efficient than state-of-the-art sparse representation based methods in dealing with face occlusion, corruption, lighting and expression changes, etc.
We study linearly dependent subsets with prescribed cardinality, $s$, of a multiprojective space. If the set $S$ is a circuit, we give an upper bound on the number of factors of the minimal multiprojective space containing $S$, while if $S$ has higher dependency this may be not true without strong assumptions. We describe the dependent subsets $S$ with $\#S=6$.
For arbitrary space dimension $d$ we investigate the quantum phase transitions of two paradigmatic spin models defined on a hypercubic lattice, the coupled-dimer Heisenberg model and the transverse-field Ising model. To this end high-order linked-cluster expansions for the ground-state energy and the one-particle gap are performed up to order 9 about the decoupled-dimer and high-field limits, respectively. Extrapolations of the high-order series yield the location of the quantum phase transition and the correlation-length exponent $\nu$ as a function of space dimension $d$. The results are complemented by $1/d$ expansions to next-to-leading order of observables across the phase diagrams. Remarkably, our analysis of the extrapolated linked-cluster expansion allows to extract the coefficients of the full $1/d$ expansion for the phase-boundary location in both models exactly in leading order and quantitatively for subleading corrections.
The quasar 1156+295 (4C +29.45) is one of the targets in the Urumqi monitoring program which aimed to search for evidence of annual modulation in the timescales of intra-day variable (IDV) sources. The IDV observations of 1156+295 were carried out nearly monthly from October 2007 to October 2009, with the Urumqi 25m radio telescope at 4.8 GHz. The source has shown prominent IDV of total flux density in most observing sessions with variability timescales of <= 1 day at 4.8 GHz. The estimated IDV timescales seem to follow an annual cycle that can be fitted with an anisotropic interstellar scintillation (ISS) model suggesting that a significant part of the flux density variations is due to ISS. The source underwent a dramatic flare in 2008. We studied the possible consequences of the flare on the IDV of 1156+295 by comparing the changes in its IDV characteristics with the evolution of the 43 GHz Very Long Baseline Array (VLBA) core size of the source. Conclusions: The quasar 1156+295 shows evidence for an annual modulation of its IDV timescales at 4.8 GHz, the ISS-induced IDV timescales and variability strength might be affected by the overall activity state of the source core. More frequent IDV and VLBI measurements are required to confirm the relation between the IDV appearance and the core-size evolution of the source.
Let $P_{n}$ be a path graph on $n$ vertices. We say that a graph $G$ is $P_{n}$-induced-saturated if $G$ contains no induced copy of $P_{n}$, but deleting any edge of $G$ as well as adding to $G$ any edge of $G^{c}$ creates such a copy. Martin and Smith (2012) showed that there is no $P_{4}$-induced-saturated graph. On the other hand, there trivially exist $P_{n}$-induced-saturated graphs for $n=2,3$. Axenovich and Csik\'{o}s (2019) ask for which integers $n \geq 5$ do there exist $P_{n}$-induced-saturated graphs. R\"{a}ty (2019) constructed such a graph for $n=6$, and Cho, Choi and Park (2019) later constructed such graphs for all $n=3k$ for $k \geq 2$. We show by a different construction that $P_{n}$-induced-saturated graphs exist for all $n \geq 6$, leaving only the case $n=5$ open.
The hadronic model of Active Galactic Nuclei and other compact high energy astrophysical sources assumes that ultra-relativistic protons, electron-positron pairs and photons interact via various hadronic and electromagnetic processes inside a magnetized volume, producing the multiwavelength spectra observed from these sources. A less studied property of such systems is that they can exhibit a variety of temporal behaviours due to the operation of different feedback mechanisms. We investigate the effects of one possible feedback loop, where \gamma-rays produced by photopion processes are being quenched whenever their compactness increases above a critical level. This causes a spontaneous creation of soft photons in the system that result in further proton cooling and more production of \gamma-rays, thus making the loop operate. We perform an analytical study of a simplified set of equations describing the system, in order to investigate the connection of its temporal behaviour with key physical parameters. We also perform numerical integration of the full set of kinetic equations verifying not only our analytical results but also those of previous numerical studies. We find that once the system becomes `supercritical', it can exhibit either a periodic behaviour or a damped oscillatory one leading to a steady state. We briefly point out possible implications of such a supercriticality on the parameter values used in Active Galactic Nuclei spectral modelling, through an indicative fitting of the VHE emission of blazar 3C 279.
The neutral hydrogen 21 cm line is an excellent tracer of the atomic interstellar medium in the cold and the warm phases. Combined 21 cm emission and absorption observations are very useful to study the properties of the gas over a wide range of density and temperature. In this work, we have used 21 cm absorption spectra from recent interferometric surveys, along with the corresponding emission spectra from earlier single dish surveys to study the properties of the atomic gas in the Milky Way. In particular, we focus on a comparison of properties between lines of sight through the gas disk in the Galactic plane and high Galactic latitude lines of sight through more diffuse gas. As expected, the analysis shows a lower average temperature for the gas in the Galactic plane compared to that along the high latitude lines of sight. The gas in the plane also has a higher molecular fraction, showing a sharp transition and flattening in the dust - gas correlation. On the other hand, the observed correlation between 21 cm brightness temperature and optical depth indicates some intrinsic difference in spin temperature distribution and a fraction of gas in the Galactic plane having intermediate optical depth (for 0.02 < $\tau$ < 0.2) but higher spin temperature, compared to that of the diffuse gas at high latitude with the same optical depth. This may be due to a small fraction of cold gas with slightly higher temperature and lower density present on the Galactic plane.
We made a time-resolved photometric campaign of the bright cataclysmic variable ASAS J071404+7004.3 in 2020. Inight et al. (2022, arXiv/2109.14514) recently published time-resolved optical spectroscopy, X-ray observations and long- and short-term optical variations. Although their results were correct in many parts, they classified ASAS J071404+7004.3 as a VY Scl-type novalike object. By comparing the ASAS-SN data of this object and the IW And-type object HO Pup, we showed that their type classification was incorrect. ASAS J071404+7004.3 showed outbursts from a standstill followed by shallow dips, which is the defining characteristic of an IW And star. This object predominantly showed states with low-amplitude dwarf nova-type oscillations, some of which could be identified as the "heartbeat"-type state as a variety of the IW And-type phenomenon. The low state described by Inight et al. (2022) was not a true low state of a VY Scl star, but a dwarf nova-type state with increased outburst amplitudes. Both ground-based (our campaign) and TESS observations detected orbital variations whose periods [0.136589(5) d by the ground-based campaign and 0.1366476(3) d by the TESS data] are in very good agreement with the one obtained by radial-velocity studies by Inight et al. (2022). The standstill in 2019-2020 in ASAS J071404+7004.3 was not brighter than its dwarf nova-type states. The brightest moment of this object occurred when the amplitudes of dwarf nova-type variations were large, which challenges the widely accepted interpretation that standstills in Z Cam stars occur when the mass-transfer rates are high.
By mechanically distorting a crystal lattice it is possible to engineer the electronic and optical properties of a material. In graphene, one of the major effects of such a distortion is an energy shift of the Dirac point, often described as a scalar potential. We demonstrate how such a scalar potential can be generated systematically over an entire electronic device and how the resulting changes in the graphene work function can be detected in transport experiments. Combined with Raman spectroscopy, we obtain a characteristic scalar potential consistent with recent theoretical estimates. This direct evidence for a scalar potential on a macroscopic scale due to deterministically generated strain in graphene paves the way for engineering the optical and electronic properties of graphene and similar materials by using external strain.
The six-dimensional effective action of F-theory compactified on a singular elliptically fibred Calabi-Yau threefold is determined by using an M-theory lift. The low-energy data are derived by comparing a circle reduction of a general six-dimensional (1,0) gauged supergravity theory with the effective action of M-theory on the resolved Calabi-Yau threefold. The derivation includes six-dimensional tensor multiplets for which the (anti-) self-duality constraints are imposed on the level of the five-dimensional action. The vector sector of the reduced theory is encoded by a non-standard potential due to the Green-Schwarz term in six dimensions. This Green-Schwarz term also contains higher curvature couplings which are considered to establish the full map between anomaly coefficients and geometry. F-/M-theory duality is exploited by moving to the five-dimensional Coulomb branch after circle reduction and integrating out massive vector multiplets and matter hypermultiplets. The associated fermions then generate additional Chern-Simons couplings at one-loop. Further couplings involving the graviphoton are induced by quantum corrections due to excited Kaluza-Klein modes. On the M-theory side integrating out massive fields corresponds to resolving the singularities of the Calabi-Yau threefold, and yields intriguing relations between six-dimensional anomalies and classical topology.