ShantanuT01/DACTYL-Pretraining huggingface dataset:
Long period variable stars arise in the final stages of the asymptotic giant branch phase of stellar evolution. They have periods of up to ~1000d and amplitudes that can exceed a factor of three in the I-band flux. These stars pulsate predominantly in their fundamental mode, which is a function of mass and radius, and so the pulsation periods are sensitive to the age of the underlying stellar population. The overall number of long period variables in a population is directly related to their lifetime, which is difficult to predict from first principles because of uncertainties associated with stellar mass-loss and convective mixing. The time variability of these stars has not been previously taken into account when modeling the spectral energy distributions of galaxies. Here we construct time-dependent stellar population models that include the effects of long period variable stars, and report the ubiquitous detection of this expected `pixel shimmer' in the massive metal-rich galaxy M87. The pixel light curves display a variety of behaviors, including linearly rising and falling curves, semi-periodic curves, and sudden increases or decreases in the flux level. The observed variation of 0.1-1% is very well matched to the predictions of our models. The data provide a strong and novel constraint on the properties of variable stars in an old and metal-rich stellar population, and we infer that the lifetime of long period variables in M87 is shorter by approximately 30% compared to predictions from the latest stellar evolution models.
The central building block of convolutional neural networks (CNNs) is the convolution operator, which enables networks to construct informative features by fusing both spatial and channel-wise information within local receptive fields at each layer. A broad range of prior research has investigated the spatial component of this relationship, seeking to strengthen the representational power of a CNN by enhancing the quality of spatial encodings throughout its feature hierarchy. In this work, we focus instead on the channel relationship and propose a novel architectural unit, which we term the "Squeeze-and-Excitation" (SE) block, that adaptively recalibrates channel-wise feature responses by explicitly modelling interdependencies between channels. We show that these blocks can be stacked together to form SENet architectures that generalise extremely effectively across different datasets. We further demonstrate that SE blocks bring significant improvements in performance for existing state-of-the-art CNNs at slight additional computational cost. Squeeze-and-Excitation Networks formed the foundation of our ILSVRC 2017 classification submission which won first place and reduced the top-5 error to 2.251%, surpassing the winning entry of 2016 by a relative improvement of ~25%. Models and code are available at https://github.com/hujie-frank/SENet.
We present a joint theoretical and experimental study of the oxygen $K$-edge spectra for LaFeO$_3$ and homovalent Ni-substituted LaFeO$_3$ (LaFe$_{0.75}$Ni$_{0.25}$O$_3$), using first-principles simulations based on density-functional theory with extended Hubbard functionals and x-ray absorption near edge structure (XANES) measurements. Ground-state and excited-state XANES calculations employ Hubbard on-site $U$ and inter-site $V$ parameters determined from first principles and the Lanczos recursive method to obtain absorption cross sections, which allows for a reliable description of XANES spectra in transition-metal compounds in a very broad energy range, with an accuracy comparable to that of hybrid functionals but at a substantially lower cost. We show that standard gradient-corrected exchange-correlation functionals fail in capturing accurately the electronic properties of both materials. In particular, for LaFe$_{0.75}$Ni$_{0.25}$O$_3$ they do not reproduce its semiconducting behaviour and provide a poor description of the pre-edge features at the O $K$ edge. The inclusion of Hubbard interactions leads to a drastic improvement, accounting for the semiconducting ground state of LaFe$_{0.75}$Ni$_{0.25}$O$_3$ and for a good agreement between calculated and measured XANES spectra. We show that the partial substitution of Fe for Ni affects the conduction-band bottom by generating a strongly hybridized O($2p$)-Ni($3d$) minority-spin empty electronic state. The present work, based on a consistent correction of self-interaction errors, outlines the crucial role of extended Hubbard functionals to describe the electronic structure of complex transition-metal oxides such as LaFeO$_3$ and LaFe$_{0.75}$Ni$_{0.25}$O$_3$ and paves the way to future studies on similar systems.
The transition from hadronic matter to quark matter in the core of neutron stars is likely to be associated with the appearance of a mixed phase, leading to a smooth variation of the star density profile. We discuss the results of a systematic study of the properties of the mixed pase upon Coulomb and surface effects. A state of the art nonrelativistic equation of state of nuclear matter has been used for the low density phase, while quark matter has been described within the MIT bag model, including the effect of perturbative one-gluon exchange interactions. The implications for neutron star structure are discussed.
First, I show explicitly a scheme to {\it faithfully} and {\it deterministically} teleport an arbitrary 2-qubit state from Alice to Bob. In this scheme two same Bell states are sufficient for use. Bob can recover the 2-qubit state by performing at most 4 single-qubit unitary operations conditioned on Alice's 4-bit classical public message corresponding to her two Bell-state measurement outcomes. Then I generalize the 2-qubit teleportation scheme to an aribitrary $N(N\ge 3)$-qubit state teleportation case by using $N$ same Bell states. In the generalized scheme, Alice only needs to identify $N$ Bell states after quantum swapping and then publish her measurement outcomes ($2N$-bit classical message). Conditioned on Alice's $2N$-bit classical message, Bob only needs to perform at most $2N$ single-qubit unitary operations to {\it fully} recover the arbitrary state. By comparing with the newest relevant work [Phys. Rev. A{\bf 71}, 032303(2005)], the advantages of the present schemes are revealed, respectively.
We investigate the separability properties of quantum two-party Gaussian states in the framework of the operator formalism for the density operator. Such states arise as natural generalizations of the entangled state originally introduced by Einstein, Podolsky, and Rosen. We present explicit forms of separable and nonseparable Gaussian states.
We consider particle trajectories in the gravitational field of an impulsive pp-wave. Due to the distributional character of the wave profile one inevitably encounters an ambiguous point value $\theta(0)$. We show that this ambiguity may be resolved by imposing covariant constancy of the square of the tangent. Our result is consistent with Colombeau's multiplication of distributions.
In this paper, we investigate the energy of a weighted random graph $G_p(f)$ in $G_{n,p}(f)$, in which each edge $ij$ takes the weight $f(d_i,d_j)$, where $d_v$ is a random variable, the degree of vertex $v$ in the random graph $G_p$ of the Erd\"{o}s--R\'{e}nyi random graph model $G_{n,p}$, and $f$ is a symmetric real function on two variables. Suppose $|f(d_i,d_j)|\leq C n^m$ for some constants $C, m>0$, and $f((1+o(1))np,(1+o(1))np)=(1+o(1))f(np,np)$. Then, for almost all graphs $G_p(f)$ in $G_{n,p}(f)$, the energy of $G_p(f)$ is $(1+o(1))f(np,np)\frac{8}{3\pi}\sqrt{p(1-p)}\cdot n^{3/2},$ where $p\in(0,1)$ is any fixed and independent of $n$. Consequently, with this one basket we can get the asymptotic values of various kinds of graph energies of chemical use, such as Randi\'c energy, ABC energy, and energies of random matrices obtained from various kinds of degree-based chemical indices.
Now that the mass limits for gluinos have been pushed to the few-TeV range, they might only be visible at the LHC in associated production with lighter gauginos. We compute the corresponding cross section at next-to-leading logarithmic (NLL) and next-to-leading order (NLO) precision in the QCD coupling constant. The resulting expressions are implemented in the public code RESUMMINO and can be directly used in the corresponding experimental searches.
Topological interactions are an essential ingredient for building consistent low-energy theories of fermions, gauge fields and Nambu-Goldstone bosons in the absence of explicit UV completions, such as in Little Higgs models. These interactions are also a probe of UV completion physics that may be out of direct experimental reach. The technology of topological, or Wess-Zumino-Witten interactions is described, using explicit examples in the standard model and in Little Higgs models. The construction of a simple topological action on SU(3)/SU(2) is described. Inconsistencies in some popular Little Higgs models are pointed out.
We review recent advances in the shell model Monte Carlo approach for the microscopic calculation of statistical and collective properties of nuclei. We discuss applications to the calculation of (i) level densities in nickel isotopes, implementing a recent method to circumvent the odd-particle sign problem; (ii) state densities in heavy nuclei; (iii) spin distributions of nuclear levels; and (iv) finite-temperature quadrupole distributions.
The set $GU_f$ of possible effective elastic tensors of composites built from two materials with positive definite elasticity tensors $\BC_1$ and $\BC_2=\Gd\BC_0$ comprising the set $U=\{\BC_1,\Gd\BC_0\}$ and mixed in proportions $f$ and $1-f$ is partly characterized in the limit $\Gd\to\infty$. The material with tensor $\BC_2$ corresponds to a material which (for technical reasons) is almost rigid in the limit $\Gd\to \infty$. The paper, and the underlying microgeometries, have many aspects in common with the companion paper "On the possible effective elasticity tensors of 2-dimensional printed materials". The chief difference is that one has a different algebraic problem to solve: determining the subspaces of stress fields for which the thin walled structures can be rigid, rather than determining, as in the companion paper, the subspaces of strain fields for which the thin walled structure is compliant. Recalling that $GU_f$ is completely characterized through minimums of sums of energies, involving a set of applied strains, and complementary energies, involving a set of applied stresses, we provide descriptions of microgeometries that in appropriate limits achieve the minimums in many cases. In these cases the calculation of the minimum is reduced to a finite dimensional minimization problem that can be done numerically. Each microgeometry consists of a union of walls in appropriate directions, where the material in the wall is an appropriate $p$-mode material, that is almost rigid to $6-p\leq 5$ independent applied stresses, yet is compliant to any strain in the orthogonal space. Thus the walls, by themselves, can support stress with almost no deformation. The region outside the walls contains "Avellaneda material" that is a hierarchical laminate which minimizes an appropriate sum of elastic energies.
Competing styles in Statistical Mechanics have been introduced to investigate physico-chemical systems displaying complex structures, when one faces difficulties to handle the standard formalism in the well established Boltzmann-Gibbs statistics. After a brief description of the question, we consider the particular case of Renyi statistics whose use is illustrated in a study of the question of the ''anomalous'' (non-Fickian) diffusion that it is involved in experiments of cyclic voltammetry in electro-physical chemistry. In them one is dealing with the fractal-like structure of the thin film morphology present in eletrodes in microbatteries which leads to fractional-power laws for describing voltammetry measurements and in the determination of the interphase width derived using atomic force microscopy. The fractional-powers associated to these quantities are related to each other and to the statistical fractal dimension, and can be expressed in terms of a power index, on which depends Renyi's statistical mechanics. It is clarified the important fact that this index, which is limited to a given interval, provides a measure of the microroughness of the electrode surface, and is related to the dynamics involved, the non-equilibrium thermodynamic state of the system, and to the experimental protocol. \\
A sequence of rational points on an algebraic planar curve is said to form an $r$-geometric progression sequence if either the abscissae or the ordinates of these points form a geometric progression sequence with ratio $r$. In this work, we prove the existence of infinitely many rational numbers $r$ such that for each $r$ there exist infinitely many $r$-geometric progression sequences on the unit circle $x^2 + y^2 = 1$ of length at least $3$.
Starting from the potential theoretic definition of the local times of a Markov process - when these exist - we obtain a Tanaka formula for the local times of symmetric L\'{e}vy processes. The most interesting case is that of the symmetric $\al$-stable L\'{e}vy process (for $\al\in[1,2]$) which is studied in detail. In particular, we determine which powers of such a process are semimartingales. These results complete, in a sense, the works by K. Yamada \cite{yamada02} and Fitzsimmons and Getoor \cite{fitzsimmonsgetoor92a}.
It is pointed out that the beaming correction commonly inferred from the achromatic breaks in the afterglow light curve is biased in situations where the isotropic equivalent energy is affected by factors other than the spread in opening angles. In particular, it underestimates the beaming factor of sources observed off-axis. Here we show that both the slopes and scatters in the Amati and Ghirlanda relations, and the difference between them, are quantitatively consistent with a model proposed recently, in which the $E_{iso}-\nu_{peak}$ relation, as originally derived by Amati et al., is due to viewing angle effects. The quantitative difference between them confirms the relations between opening angle and break time suggested by Frail et al.
Let $G$ be a simple graph with $n$ vertices and $\pm 1$-weights on edges. Suppose that for every edge $e$ the sum of edges adjacent to $e$ (including $e$ itself) is positive. Then the sum of weights over edges of $G$ is at least $-\frac{n^2}{25}$. Also we provide an example of a weighted graph with described properties and the sum of weights $-(1+o(1))\frac{n^2}{8(1 + \sqrt{2})^2}$.   The previous best known bounds were $-\frac{n^2}{16}$ and $-(1+o(1))\frac{n^2}{54}$ respectively. We show that the constant $-1/54$ is optimal under some additional conditions.
We examine a model in which a nonequilibrium phase transition from an active to an extinct state is observed. The order of this phase transition has been shown to be either continuous or first-order, depending on the parameter values and the dimension of the system. Using increasingly large clusters, we use the cluster approximation method to obtain estimates for the critical points in 1+1 dimensions. For the continuous phase transitions only, extrapolations of these approximations show excellent agreement with simulation results. Further, the approximations suggest that, consistent with simulation results, in 1+1 dimensions no first-order phase transitions are observed.
This paper considers a work-conserving FIFO single-server queue with multiple batch Markovian arrival streams governed by a continuous-time finite-state Markov chain. A particular feature of this queue is that service time distributions of customers may be different for different arrival streams. After briefly discussing the actual waiting time distributions of customers from respective arrival streams, we derive a formula for the vector generating function of the time-average joint queue length distribution in terms of the virtual waiting time distribution. Further assuming the discrete phase-type batch size distributions, we develop a numerically feasible procedure to compute the joint queue length distribution. Some numerical examples are provided also.
We use direct N-body simulations of gas embedded star clusters to study the importance of stellar collisions for the formation and mass accretion history of high-mass stars. Our clusters start in virial equilibrium as a mix of gas and proto-stars. Proto-stars then accrete matter using different mass accretion rates and the amount of gas is reduced in the same way as the mass of stars increases. During the simulations we check for stellar collisions and we investigate the role of these collisions for the build-up of high-mass stars and the formation of runaway stars. We find that a significant number of collisions only occur in clusters with initial half-mass radii r_h < 0.1 pc. After emerging from their parental gas clouds, such clusters end up too compact compared to observed young, massive open clusters. In addition, collisions lead mainly to the formation of a single runaway star instead of the formation of many high mass stars with a broad mass spectrum. We therefore conclude that massive stars form mainly by gas accretion, with stellar collisions only playing a minor role if any at all. Collisions of stars in the pre-main sequence phase might however contribute to the formation of the most massive stars in the densest star clusters and possibly to the formation of intermediate-mass black holes with masses up to a few 100 Msun.
We consider continuous time random walks (CTRW) and discuss situations pertinent to aging. These correspond to the case when the initial state of the system is known not at preparation (at $t=0$) but at the later instant of time $t_1>0$ (intermediate-time initial condition). We derive the generalized aging diffusion equation for this case and express it through a single memory kernel. The results obtained are applied to the practically relevant case of the equilibrated random walks. We moreover discuss some subtleties in the setup of the aging subdiffusion problem and show that the behavior of the system depends on what was taken as the intermediate-time initial condition: whether it was coordinate of one particle given by measurement or the whole probability distribution. The two setups lead to different predictions for the evolution of a system. This fact stresses the necessity of a precise definition of aging statistical ensembles.
The geoeffective magnetic cloud (MC) of 20 November 2003, has been associated to the 18 November 2003, solar active events in previous studies. In some of these, it was estimated that the magnetic helicity carried by the MC had a positive sign, as well as its solar source, active region (AR) NOAA 10501. In this paper we show that the large-scale magnetic field of AR 10501 had a negative helicity sign. Since coronal mass ejections (CMEs) are one of the means by which the Sun ejects magnetic helicity excess into the interplanetary space, the signs of magnetic helicity in the AR and MC should agree. Therefore, this finding contradicts what is expected from magnetic helicity conservation. However, using for the first time correct helicity density maps to determine the spatial distribution of magnetic helicity injection, we show the existence of a localized flux of positive helicity in the southern part of AR 10501. We conclude that positive helicity was ejected from this portion of the AR leading to the observed positive helicity MC.
Active Region (AR) 12192 is the biggest AR observed in solar cycle 24 so far. This was a long-lived AR which survived for four Carrington rotations (CR) and exhibited several unusual phenomena. We measure the horizontal subsurface flows in this active region in multiple rotation using the ring-diagram technique of local helioseismology and the Global Oscillation Network Group (GONG+) Dopplergrams, and investigate how different was the plasma flow in AR 12192 from that in AR 10486. Both regions produced several high M- and X-class flares but had different CME productivity. Our analysis suggests that these ARs had unusually large horizontal flow amplitude with distinctly different directions. While meridional flow in AR 12192 was poleward that supports the flux transport to poles, it was equatorward in AR 10486. Furthermore, there was a sudden increase in the magnitude of estimated zonal flow in shallow layers in AR 12192 during the X3.1 flare, however, it reversed direction in AR 10486 with X17.2 flare. These flow patterns produced strong twists in horizontal velocity with depth in AR 10486 that persisted throughout the disk passage as opposed to AR 12192, which produced a twist only after the eruption of the X3.1 flare that disappeared soon after. Our study indicates that the sunspot rotation combined with the re-organization of magnetic field in AR 10486 was not sufficient to decrease the flow energy even after several large flares that might have triggered CMEs. Furthermore, in the absence of sunspot rotation in AR 12192, this re-organization of magnetic field contributed significantly to the substantial release of flow energy after the X3.1 flare.
In this report, future performance demands of batteries for various vehicular applications are modeled. Vehicles ranging in size from electric bikes to heavy trucks are assessed using driving cycle data which allows key performance parameters such as desired range (km), specific energy of the battery (Wh/Kg), cycle life requirement and expected price per unit capacity (Euro/kWh) to be calculated. These projected performance requirements are compared with the outputs for three existing Li-ion batteries (namely (a) Kokam based high specific energy source (b) A123 based high power energy source and (c) Winston low cost system). The theoretical, current state of the art and projected performance parameters for 'beyond Li-ion' technologies (Li-S and Li-O2) are also compared to the modeled battery performance demands. The analysis indicates that current battery technologies are unlikely to meet future requirements in terms of required specific energies and will likely be too costly. In comparison, fully realized beyond Li-ion alternatives may deliver the required specific energy for the full range of vehicles examined. However, scale-up of these systems is a daunting challenge and their successful implementation will depend on improvements in terms of cycle life, electrode and electrolyte stability, rate performance and development of practical battery architectures.