ShantanuT01/DACTYL-Pretraining huggingface dataset:
We study how one-particle correlations transfer to manifest as two-particle correlations in the context of parametric down-conversion (PDC), a process in which a pump photon is annihilated to produce two entangled photons. We work in the polarization degree of freedom and show that for any two-qubit generation process that is both trace-preserving and entropy-nondecreasing, the concurrence $C(\rho)$ of the generated two-qubit state $\rho$ follows an intrinsic upper bound with $C(\rho)\leq (1+P)/2$, where $P$ is the degree of polarization of the pump photon. We also find that for the class of two qubit states that is restricted to have only two non-zero diagonal elements such that the effective dimensionality of the two-qubit state is same as the dimensionality of the pump polarization state, the upper bound on concurrence is the degree of polarization itself, that is, $C(\rho)\leq P$. Our work shows that the maximum manifestation of two-particle correlations as entanglement is dictated by one-particle correlations. The formalism developed in this work can be extended to include multi-particle systems and can thus have important implications towards deducing the upper bounds on multi-particle entanglement, for which no universally accepted measure exists.
We provide a canonical decomposition for a class of bipartite grafts known as combs. As every bipartite graft is a recursive combination of combs, our results provides a canonical decomposition for general bipartite grafts. Our new decomposition is by definition a generalization of the classical canonical decomposition in matching theory, that is, the Dulmage-Mendelsohn decomposition for bipartite graphs with perfect matchings. However, it exhibits much more complicated structure than its classical counterpart. It is revealed from our results that bipartite grafts has a canonical structure that is analogous to the cathedral decomposition for nonbipartite graphs with perfect matchings.
Free-standing carbon nanomembranes (CNM) with molecular thickness and macroscopic size are fascinating objects both for fundamental reasons and for applications in nanotechnology. Although being made from simple and identical precursors their internal structure is not fully known and hard to simulate due to the large system size that is necessary to draw definite conclusions. We performed large-scale classical molecular dynamics investigations of biphenyl-based carbon nanomembranes. We show that one-dimensional graphene-like stripes constitute a highly symmetric quasi one-dimensional ground state. This state does not crosslink. Instead crosslinked structures are formed from highly excited precursors with a sufficient amount of broken phenyls. The internal structure of CNM is very likely a disordered metastable state which is formed in the process of cooling.
In this paper the factorization method is used in order to obtain the eigenvalues and eigenfunctions of a quantum particle confined in a one-dimensional infinite well. The output results from the mentioned approach allows us to explore an appropriate new pair of raising and lowering operators corresponding to the physical system under consideration. From the symmetrical considerations, the connection between the obtained ladder operators with $su(1,1)$ Lie algebra is explicitly established. Next, after the construction of Barut-Girardello and Gilmore-Perelomov representations of coherent states associated with the considered system, some of their important properties like the resolution of the identity including a few nonclassical features are illustrated in detail. Finally, a theoretical scheme for generation of the Gilmore-Perelomov type of coherent state via a generalized Janes-Cummings model is proposed.
In a flat spacetime with one spatial dimension compactified, inertial reference frames are not all equivalent, but there are the preferred ones. This paper investigates the nonequivalence of inertial frames and also that of uniformly accelerated frames in connection with the response of the Unruh-DeWitt detector coupled to a massless scalar field. The detector's transition rates of both excitation and de-excitation are studied in depth for three different cases: (i) the detector moving at an arbitrary constant velocity, (ii) moving with a constant acceleration in the compact direction, and (iii) moving with a constant acceleration in noncompact directions. The instantaneous transition rate in relation to the switching function is also taken into account.
We investigate the long-time behavior of a majority rule opinion dynamics model in finite spatial dimensions. Each site of the system is endowed with a two-state spin variable that evolves by majority rule. In a single update event, a group of spins with a fixed (odd) size is specified and all members of the group adopt the local majority state. Repeated application of this update step leads to a coarsening mosaic of spin domains and ultimate consensus in a finite system. The approach to consensus is governed by two disparate time scales, with the longer time scale arising from realizations in which spins organize into coherent single-opinion bands. The consequences of this geometrical organization on the long-time kinetics are explored.
There have been several ideas proposed to explain how the Sun's corona is heated and how the solar wind is accelerated. Some models assume that open magnetic field lines are heated by Alfven waves driven by photospheric motions and dissipated after undergoing a turbulent cascade. Other models posit that much of the solar wind's mass and energy is injected via magnetic reconnection from closed coronal loops. The latter idea is motivated by observations of reconnecting jets and also by similarities of ion composition between closed loops and the slow wind. Wave/turbulence models have also succeeded in reproducing observed trends in ion composition signatures versus wind speed. However, the absolute values of the charge-state ratios predicted by those models tended to be too low in comparison with observations. This letter refines these predictions by taking better account of weak Coulomb collisions for coronal electrons, whose thermodynamic properties determine the ion charge states in the low corona. A perturbative description of nonlocal electron transport is applied to an existing set of wave/turbulence models. The resulting electron velocity distributions in the low corona exhibit mild suprathermal tails characterized by "kappa" exponents between 10 and 25. These suprathermal electrons are found to be sufficiently energetic to enhance the charge states of oxygen ions, while maintaining the same relative trend with wind speed that was found when the distribution was assumed to be Maxwellian. The updated wave/turbulence models are in excellent agreement with solar wind ion composition measurements.
3D reconstruction has lately attracted increasing attention due to its wide application in many areas, such as autonomous driving, robotics and virtual reality. As a dominant technique in artificial intelligence, deep learning has been successfully adopted to solve various computer vision problems. However, deep learning for 3D reconstruction is still at its infancy due to its unique challenges and varying pipelines. To stimulate future research, this paper presents a review of recent progress in deep learning methods for Multi-view Stereo (MVS), which is considered as a crucial task of image-based 3D reconstruction. It also presents comparative results on several publicly available datasets, with insightful observations and inspiring future research directions.
Nonmesonic weak decays of s-shell hypernuclei are analyzed in microscopic models for the Lambda N to NN weak interaction. A scalar-isoscalar meson, sigma, is introduced and its importance in accounting the decay rates, n/p ratios and proton asymmetry is demonstrated. Possible violation of the Delta I=1/2 rule in the nonmesonic weak decay of Lambda is discussed in a phenomenological analysis and several useful constraints are presented. The microscopic calculation shows that the current experimental data indicate a large violation of the Delta I=1/2 rule, although no definite conclusion can be derived due to large ambiguity of the decay rate of {^4_Lambda H}.
We consider the Cauchy problem for incompressible Navier-Stokes equations $u_t+u\nabla_xu-\Delta u+\nabla p=0, div u=0 in R^d \times R^+$ with initial data $a\in L^d(R^d)$, and study in some detail the smoothing effect of the equation. We prove that for $T<\infty$ and for any positive integers $n$ and $m$ we have $t^{m+n/2}D^m_tD^{n}_x u\in L^{d+2}(R^d\times (0,T))$, as long as the $\|u\|_{L^{d+2}_{x,t}(R^d\times (0,T))}$ stays finite.
This paper generalises Mori's famous theorem about "Projective manifolds with ample tangent bundles" to normal projective varieties in the following way:   A normal projective variety over $\mathbb{C}$ with ample tangent sheaf is isomorphic to the complex projective space.
In 2+1 dimensions, for low momenta, using dimensional renormalization we study the effect of a Chern-Simons field on the perturbative expansion of fermions self interacting through a Gross Neveu coupling. For the case of just one fermion field, we verify that the dimension of operators of canonical dimension lower than three decreases as a function of the Chern-Simons coupling.
The non-repeating fast radio bursts (FRBs) could arise from catastrophic stellar explosions or magnetar giant flares, so relativistic blast waves might be produced in these events. Motivated by this, we here search for GeV counterparts to all non-repeating FRBs with Fermi Large Area Telescope (LAT), including FRB 131104 that is claimed to be possibly associated with a gamma-ray transient candidate detected by Swift Burst Alert Telescope (BAT). FRB 131104 enters the field of view (FoV) of LAT ~5000s after the burst time, so we are only able to search for the GeV afterglow emission during this period, but no significant GeV emission is detected. We also perform a search for GeV emissions from other FRBs, but no significant GeV emissions are detected either. Upper limit fluences in the range of (4.7-29.2)x10^(-7) erg/cm2 are obtained, and then the upper limits of the isotropic blast wave kinetic energy of about (1-200)x10^(53) erg are inferred under certain assumptions. Although the current limits on the isotropic blast wave energy are not sufficiently stringent to rule out the connection between FRBs and GRB-like transients, future more sensitive observations with Fermi or Imaging Atmospheric Cherenkov Telescopes might be able to constrain the connection.
We develop a relativistic multifluid dynamics appropriate for describing neutron star cores at finite temperatures based on Carter's convective variational procedure. The model includes seven fluids, accounting for both normal and superfluid/superconducting neutrons and protons, leptons (electrons and muons) and entropy. The formulation is compared to the non-variational relativistic multifluid hydrodynamics of Gusakov and collaborators and shown to be equivalent. Vortex lines and flux tubes, mutual friction, vortex pinning, heat conduction and viscosity are incorporated into the model in steps after the basic hydrodynamics is described. The multifluid system is then considered at the mesoscopic scale where the currents around individual vortex lines and flux tubes are important, and this mesoscopic theory is averaged to determine the detailed vortex line/flux tube contributions to the macroscopic "effective" theory. This matching procedure is partially successful, though obtaining full agreement between the averaged mesoscopic and macroscopic effective theory requires discarding subdominant terms. The matching procedure allow us to interpret the magnetic $H$-field inside a neutron star in a way that is consistent with condensed matter physics literature, and to clarify the difference between this interpretation and that in previous astrophysical works.
A brief review of key recent developments and ongoing projects in perturbative QCD theory, with emphasis on conceptual advances that have the potential for impact on LHC studies. Topics covered include: twistors and new recursive calculational techniques; automation of one-loop predictions; developments concerning NNLO calculations; the status of Monte Carlo event generators and progress in matching to fixed order; analytical resummation including the push to NNLL, automation and gap between jets processes; and progress in the understanding of saturation at small x.
The discovery of extremely zirconium- and lead-rich surfaces amongst a small subgroup of hot subdwarfs has provoked questions pertaining to chemical peculiarity in hot star atmospheres and about their evolutionary origin. With only three known in 2014, a limited search for additional `heavy-metal' subdwarfs was initiated with the Subaru telescope. Five hot subdwarfs having intermediate to high surface enrichment of helium were observed at high-resolution and analyzed for surface properties and abundances. This paper reports the analyses of four of these stars. PG1559+048 and FBS 1749+373, having only intermediate helium enrichment, show strong lines of triply ionized lead. PG1559+048 also shows a strong overabundance of germanium and yttrium. With more helium-rich surfaces, Ton 414 and J17554+5012, do not show evidence of heavy-metal enrichment. This limited survey suggests that extreme enrichment of `heavy metals' by selective radiative levitation in hot subdwarf atmospheres is suppressed if the star is too helium-rich.
We add a random bulk term, modelling the interaction with the impurities of the medium, to a standard functional in the gradient theory of phase transitions consisting of a gradient term with a double well potential. We show that in $d\le2$ there exists, for almost all the realizations of the random bulk term, a unique random macroscopic minimizer. This result is in sharp contrast to the case when the random bulk term is absent. In the latter case there are two minimizers which are (in law) invariant under translations in space.
In a recent work we demonstrated that a novel X-ray scaling method, originally introduced for Galactic black holes (GBHs), can be reliably extended to estimate the mass of supermassive black holes accreting at a moderate to high level. Here we investigate the limits of applicability of this method to low-accreting active galactic nuclei, using a control sample with good-quality X-ray data and dynamically measured mass. For low-accreting AGNs, because the basic assumption that the photon index positively correlates with the accretion rate no longer holds the X-ray scaling method cannot be used. Nevertheless, the inverse correlation in the Gamma-Lx/LEdd diagram, found in several low-accreting black holes and confirmed by this sample, can be used to constrain black hole mass within a factor of ~10 from the dynamically determined values. We provide a simple recipe to determine black hole mass using solely X-ray spectral data, which can be used as a sanity check for black hole mass determination based on indirect optical methods.
The coupled equations for the scalar modes of the linearized Einstein equations around Schwarzschild's spacetime were reduced by Zerilli to a 1+1 wave equation with a potential $V$, on a field $\Psi_z$. For smooth metric perturbations $\Psi_z$ is singular at $r_s=-6M/(\ell-1)(\ell+2)$, $\ell$ the mode harmonic number, and $V$ has a second order pole at $r_s$. This is irrelevant to the black hole exterior stability problem, where $r>2M>0$, and $r_s <0$, but it introduces a non trivial problem in the naked singular case where $M<0$, then $r_s>0$, and the singularity appears in the relevant range of $r$. We solve this problem by developing a new approach to the evolution of the even mode, based on a {\em new gauge invariant function}, $\hat \Psi$ -related to $\Psi_z$ by an intertwiner operator- that is a regular function of the metric perturbation {\em for any value of $M$}. This allows to address the issue of evolution of gravitational perturbations in this non globally hyperbolic background, and to complete the proof of the linear instability of the Schwarzschild naked singularity, by showing that a previously found unstable mode is excitable by generic initial data. This is further illustrated by numerically solving the linearized equations for suitably chosen initial data.
The existence of "radio weak BL Lac objects" (RWBLs) has been an open question, still unsolved, since the discovery that quasars could be radio-quiet or radio-loud. Recently several groups identified RWBL candidates, mostly found while searching for low energy counterparts of the unidentified/unassociated gamma-ray sources listed in the Fermi catalogs. Confirming RWBLs is a challenging task since they could be confused with white dwarfs (WDs) or weak emission line quasars (WELQs) when there are not sufficient data to precisely draw their broad band spectral energy distribution and their classification is mainly based on a featureless optical spectra. Motivated by the recent discovery that Fermi BL Lacs appear to have very peculiar mid-IR emission, we show that it is possible to distinguish between WDs, WELQs and BL Lacs using the [3.4]-[4.6]-[12]$\mu$m color-color plot built using the WISE magnitudes when the optical spectrum is available. On the basis of this analysis, we identify WISE J064459.38+603131 and WISE J141046.00+740511.2 as the first two genuine RWBLs, both potentially associated with Fermi sources. Finally, to strengthen our identification of these objects as true RWBLs, we present multifrequency observations for these two candidates to show that their spectral behavior is indeed consistent with those of the BL Lac population.
We prove local $C^{1,\alpha}$ estimates of solutions for the parallel refractor and reflector problems under local assumptions on the target set $\Sigma$, and no assumptions are made on the smoothness of the densities.
In this paper we construct and study the actions of certain deformations of the Lie algebra of Hamiltonians on the plane on the Chow groups (resp., cohomology) of the relative symmetric powers ${\cal C}^{[\bullet]}$ and the relative Jacobian ${\cal J}$ of a family of curves ${\cal C}/S$. As one of the applications, we show that in the case of a single curve $C$ this action induces a integral form of a Lefschetz $\operatorname{sl}_2$-action on the Chow groups of $C^{[N]}$. Another application gives a new grading on the ring of 0-cycles on the Jacobian $J$ of $C$ (with respect to the Pontryagin product) and equips it with an action of the Lie algebra of vector fields on the line. We also define the groups of tautological classes in $CH^*({\cal C}^{[\bullet]})$ and in $CH^*({\cal J})$ and prove for them analogs of the properties established in the case of the Jacobian of a single curve by Beauville in math.AG/0204188. We also show that the our algebras of operators preserve the subrings of tautological cycles and act on them via some explicit differential operators.
Multivariate tempered stable random measures (ISRMs) are constructed and their corresponding space of integrable functions is characterized in terms of a quasi-norm utilizing the so-called Rosinski measure of a tempered stable law. In the special case of exponential tempered ISRMs operator-fractional tempered stable random fields are presented by a moving-average and a harmonizable representation, respectively.
In this paper, we consider $m$ independent random rectangular matrices whose entries are independent and identically distributed standard complex Gaussian random variables and assume the product of the $m$ rectangular matrices is an $n$ by $n$ square matrix. We study the limiting empirical spectral distributions of the product where the dimension of the product matrix goes to infinity, and $m$ may change with the dimension of the product matrix and diverge. We give a complete description for the limiting distribution of the empirical spectral distributions for the product matrix and illustrate some examples.
A \emph{gerechte framework} is a partition of an $n \times n$ array into $n$ regions of $n$ cells each. A \emph{realization} of a gerechte framework is a latin square of order $n$ with the property that when its cells are partitioned by the framework, each region contains exactly one copy of each symbol. A \emph{gerechte design} is a gerechte framework together with a realization.   We investigate gerechte frameworks where each region is a rectangle. It seems plausible that all such frameworks have realizations, and we present some progress towards answering this question. In particular, we show that for all positive integers $s$ and $t$, any gerechte framework where each region is either an $s \times t$ rectangle or a $t\times s$ rectangle is realizable.
Using a spectral stacking technique we searched for the average \lya emission from high-z Damped \lya (DLA) galaxies detected in the Sloan Digital Sky Survey QSO spectra. We used a sample of 341 DLAs of mean redshift <z>= 2.86 and log N(HI) > 20.62 to place a 3$\sigma$ upper limit of 3.0 \times 10^{-18} erg s^{-1} cm^{-2} on the \lya flux emitted within $\sim$1.5 arcsec (or 12 kpc) from the QSO line of sight. This corresponds to an average \lya luminosity of < 2 \times 10^{41} erg s^{-1} or 0.03 $L_\star$(\lya). This limit is deeper than the limit of most surveys for faint \lya emitters. The lack of \lya emission in DLAs is consistent with the in situ star formation, for a given N(HI), being less efficient than what is seen in local galaxies. Thus, the overall DLA population seems to originate from the low luminosity end of the high redshift \lya emitting galaxies and/or to be located far away from the star forming regions. The latter may well be true since we detect strong OVI absorption in the stacked spectrum, indicating that DLAs are associated with a highly ionized phase possibly the relics of galactic winds and/or originating from cold accretion flows. We find the contribution of DLA galaxies to the global star formation rate density to be comparatively lower than that of Lyman Break Galaxies.
This paper relates both to the metaphysics of probability and to the physics of time asymmetry. Using the formalism of decoherent histories, it investigates whether intuitions about intrinsic time directedness that are often associated with probability can be justified in the context of no-collapse approaches to quantum mechanics. The standard (two-vector) approach to time symmetry in the decoherent histories literature is criticised, and an alternative approach is proposed, based on two decoherence conditions ('forwards' and 'backwards') within the one-vector formalism. In turn, considerations of forwards and backwards decoherence and of decoherence and recoherence suggest that a time-directed interpretation of probabilities, if adopted, should be both contingent and perspectival.
It was recently shown that a finite imbalance between electron densities in the $\mathbf{K}$ and $\mathbf{K}'$ valleys of bilayer graphene induces a magnetoelectric coupling. Here we explore ramifications of this electronically tunable magnetoelectric effect for the optical conductivity and dielectric permittivity of this material. Our results augment current understanding of longitudinal magnetoresistance and magnetocapacitance in unconventional materials.