ShantanuT01/DACTYL-Pretraining huggingface dataset:
Aims: In the present work we investigate the nature of the magnetic Rayleigh-Taylor instability at a density interface permeated by an oblique, homogeneous magnetic field in an incompressible limit. Methods: Using the system of linearised ideal incompressible magnetohydrodynamics (MHD) equations we derive the dispersion relation for perturbations of the contact discontinuity by imposing the necessary continuity conditions at the interface. The imaginary part of the frequency describes the growth rate of waves due to instability. The growth rate of waves is studied by solving numerically the dispersion relation. Results: The critical wavenumber at which waves become unstable, present for a parallel magnetic field, disappears, due to the inclination of the magnetic field and instead waves are shown to be unstable for all wavenumbers. Theoretical results are applied to diagnose the structure of the magnetic field in prominence threads. When applying our theoretical results to observed waves in prominence plumes, we obtain a wide range of field inclination angle; from 0.5 degrees up to 30 degrees. These results highlight the diagnostic possibility of our study.
Recently, we have witnessed the explosive growth of images with complex information and content. In order to effectively and precisely retrieve desired images from a large-scale image database with low time-consuming, we propose the multiple feature fusion image retrieval algorithm based on the texture feature and rough set theory in this paper. In contrast to the conventional approaches that only use the single feature or standard, we fuse the different features with operation of normalization. The rough set theory will assist us to enhance the robustness of retrieval system when facing with incomplete data warehouse. To enhance the texture extraction paradigm, we use the wavelet Gabor function that holds better robustness. In addition, from the perspectives of the internal and external normalization, we re-organize extracted feature with the better combination. The numerical experiment has verified general feasibility of our methodology. We enhance the overall accuracy compared with the other state-of-the-art algorithms.
We explore the `Moebius disjointness property' in the special context of rank-one transformations and verify this phenomenon for many of the `classical' models
An approximate treatment of exchange in finite-temperature path integral Monte Carlo simulations for fermions has been proposed. In this method, some of the fine details of density matrix due to permutations have been smoothed over or averaged out by using the coarse-grained approximation. The practical usefulness of the method is tested for interacting fermions in a three dimensional harmonic well. The results show that, the present method not only reduces the sign fluctuation of the density matrix, but also avoid the fermion system collapsing into boson system at low temperatures. The method is substantiated to be exact when applied to free particles.
We investigate the one-dimensional ferromagnetic Kondo lattice in the hole-rich region. Of interest to us is the intermediate situation where the ferromagnetic Kondo coupling (Hund's coupling) is comparable to the electron bandwidth. The forced alignment favors triplet states whereas singlet states enter in a quite low-density regime. The direct antiferromagnetic exchange between the core spins is assumed to still prevail over the double exchange. We discuss a solvable limit showing that short-range antiferromagnetism in the spin array will affect the coherent propagation of triplets, i.e., turns a light triplet onto a heavy singlet, resulting in a heavy electron ground state.
We present analytic results for the finite diagrams contributing to the two-loop eight-point MHV scattering amplitude of planar N=4 SYM. We use a recently proposed representation for the integrand of the amplitude in terms of (momentum) twistors and focus on a restricted kinematics in which the answer depends only on two independent cross-ratios. The theory of motives can be used to vastly simplify the results, which can be expressed as simple combinations of classical polylogarithms.
In the unknown territory of transfermium nuclei, the relativistic mean-field (RMF) theory has been applied to probe decay modes which include $\alpha$-decay, spontaneous fission (SF), and a less explored weak-decay. These decay modes are analyzed on equal footing for 101$\leq$Z$\leq$109 and as a consequence, the half-lives for weak-decay are indeed found comparable for several isotopes. Our prediction of decay modes and half-lives are found in excellent agreement with available experimental decay modes and half-lives along with the results of some other theories. Out of $\alpha$, $\beta^+$/EC, $\beta^-$, and SF, the most probable decay mode is anticipated along with its half-life over a wide range of odd and even nuclei to frame a novel sight into terra incognita.
This is a note on the classical Waring's problem for several homogeneous forms. For positive integers (n,d,r,s), fix a general r-dimensional subspace of degree d forms in n+1 variables. We describe the family of s-sided polar polyhedra of this subspace in many specific cases.
Context: Studying the motions on the solar surface is fundamental for understanding how turbulent convection transports energy and how magnetic fields are distributed across the solar surface.   Aims: From horizontal velocity measurements all over the visible disc of the Sun and using data from the Solar Dynamics Observatory/Helioseismic and Magnetic Imager (SDO/HMI), we investigate the structure and evolution of solar supergranulation.   Methods: Horizontal velocity fields were measured by following the proper motions of solar granules using a newly developed version of the coherent structure tracking (CST) code. With this tool, maps of horizontal divergence were computed. We then segmented and identified supergranular cells and followed their histories by using spatio-temporal labelling. With this dataset we derived the fundamental properties of supergranulation, including their motion.   Results: We find values of the fundamental parameters of supergranulation similar to previous studies: a mean lifetime of 1.5 days and a mean diameter of 25~Mm. The tracking of individual supergranular cells reveals the solar differential rotation and a poleward circulation trend of the meridional flow. The shape of the derived differential rotation and meridional flow does not depend on the cell size. If there is a background magnetic field, the diverging flows in supergranules are weaker.   Conclusions: This study confirms that supergranules are suitable tracers that may be used to investigate the large-scale flows of the solar convection as long as they are detectable enough on the surface.
Low-temperature magnetization (M) measurements down to 0.1 K have been performed in magnetic fields up to 14.5 T for a single piece of a tiny single-crystalline sample (0.2 mg weight) of the spin-gap system YbAl3C3. At the base temperature of 0.1 K, several metamagnetic transitions were clearly observed for H // c in the range 6 T < H < 9 T whereas only two transitions were observed, one at 4.8 T and the other at 6.6 T, for H // a. At fields above 9 T, the magnetization becomes almost saturated for both H // a and H // c. The present results indicate that a singlet-triplet crossover occurs in a relatively narrow field range, suggesting a rather weak interdimer interaction in spite of the nearly triangular lattice of Yb ions.
The solar photosphere is filled by a magnetic field which is tangled on scales much smaller than the resolution capability of solar telescopes. This hidden magnetic field can be investigated via the Hanle effect. In 2007 we started a synoptic program to explore if the magnetic flux of the quiet photosphere varies with the solar cycle. For this purpose we applied a differential Hanle effect technique based on observations of scattering polarization in C$_2$ molecular lines around 514.0 nm, taken generally every month. Our results now span almost one complete solar cycle.
Individual pulses from pulsars have intensity-phase profiles that differ widely from pulse to pulse, from the average profile, and from phase to phase within a pulse. Widely accepted explanations for pulsar radio emission and its time variability do not exist. Here, by analysing data near the peak of the Vela pulsar's average profile, we show that Vela's variability corresponds to lognormal field statistics, consistent with the prediction of stochastic growth theory (SGT) for a purely linear system close to marginal stability. Vela's variability is therefore a direct manifestation of an SGT state and the field statistics constrain the emission mechanism to be linear (either direct or indirect), ruling out nonlinear mechanisms like wave collapse. Field statistics are thus a powerful, potentially widely applicable tool for understanding variability and constraining mechanisms and source characteristics of coherent astrophysical and space emissions.
The latest results of the QUEST survey for RR Lyrae stars are described. This survey, which is designed to find and characterize sub-structures in the halo of our Galaxy, has covered about 700 square degrees of the sky and has detected 693 RR Lyrae stars, most of which are new discoveries. The spatial distribution of the RR Lyrae stars reveals several interesting groups in the halo. Some of them appear to be related to previous detections of the destruction of dwarf spheroidal galaxies (the Sagittarius tidal streams, the Virgo stellar stream, the Monoceros ring) or globular clusters (Palomar 5), while others still have an unknown origin.
We present a detailed analysis of spin squeezing of the one-axis twisting model with a many-body phase dephasing, which is induced by external field fluctuation in a two-mode Bose-Einstein condensates. Even in the presence of the dephasing, our analytical results show that the optimal initial state corresponds to a coherent spin state $|\theta_{0}, \phi_0\rangle$ with the polar angle $\theta_0=\pi/2$. If the dephasing rate $\gamma\ll S^{-1/3}$, where $S$ is total atomic spin, we find that the smallest value of squeezing parameter (i.e., the strongest squeezing) obeys the same scaling with the ideal one-axis twisting case, namely $\xi^2\propto S^{-2/3}$. While for a moderate dephasing, the achievable squeezing obeys the power rule $S^{-2/5}$, which is slightly worse than the ideal case. When the dephasing rate $\gamma>S^{1/2}$, we show that the squeezing is weak and neglectable.
The universe might experience many cycles with different vacua. The slow-roll inflation may be preceded by kinetic-dominated contraction occurring in "adjacent" vacua during some cycles. In this report we briefly show this phenomenon may lead to a cutoff of primordial power spectrum. Thus in some sense the CMB at large angular scale might encode the information of other vacua.
In the recent past, the computer vision community has developed centralized benchmarks for the performance evaluation of a variety of tasks, including generic object and pedestrian detection, 3D reconstruction, optical flow, single-object short-term tracking, and stereo estimation. Despite potential pitfalls of such benchmarks, they have proved to be extremely helpful to advance the state of the art in the respective area. Interestingly, there has been rather limited work on the standardization of quantitative benchmarks for multiple target tracking. One of the few exceptions is the well-known PETS dataset, targeted primarily at surveillance applications. Despite being widely used, it is often applied inconsistently, for example involving using different subsets of the available data, different ways of training the models, or differing evaluation scripts. This paper describes our work toward a novel multiple object tracking benchmark aimed to address such issues. We discuss the challenges of creating such a framework, collecting existing and new data, gathering state-of-the-art methods to be tested on the datasets, and finally creating a unified evaluation system. With MOTChallenge we aim to pave the way toward a unified evaluation framework for a more meaningful quantification of multi-target tracking.
We present BAX, Base de Donn\'ees amas de galaxies X (http://webast.ast.obs-mip.fr/bax), a project aiming at building a comprehensive database dedicated to X-rays clusters of galaxies allowing detailed information retrieval. BAX provides the user with {\it basic data} published in the literature on X-rays clusters of galaxies as well as with information concerning the physical properties in the X-rays domain or at other wavelengths. BAX allows individual studies on selected clusters as well as building up homogenous samples, from known X-rays clusters for which selection criteria are chosen through web interfaces. We expect BAX to become a useful tool for astronomy community in order to optimize the cluster science return using data from both ground based facilities like MEGACAM (CFHT), VIRMOS (VLT) and space missions like XMM, Chandra and Planck.
Mechanical couplings such as axial-shear and axial-bending have great potential in the design of active mechanical metamaterials with directional control of input and output loads in sensors and actuators. However, the current ad hoc design of mechanical coupling without theoretical support of elasticity cannot provide design guidelines for mechanical coupling with lattice geometries. Moreover, the correlation between mechanical coupling effects and geometric symmetry is not yet clearly understood. In this work, we systematically search for all possible mechanical couplings in 2D lattice structures by determining the non-zero diagonal terms in the decomposed micropolar elasticity tensor. We also correlate the mechanical couplings with the point-group symmetry of 2D lattices by applying the symmetry operation to the decomposed micropolar elasticity tensor. The decoupled micropolar constitutive equation uncovers eight coupling effects for 2D lattice structures. The symmetry operation of the decoupled micropolar elasticity tensor reveals the correlation of the mechanical coupling with the point groups. Our findings can strengthen the design of mechanical metamaterials with potential applications in areas including sensors, actuators, soft robots, and active metamaterials for elastic/acoustic wave guidance and thermal management.
Early shallow-decaying X-ray afterglows of gamma-ray bursts (GRBs) may be attributed to the dipole radiations of newly-born magnetars. Assuming that the GRB jets powered by magnetars are quasi-universal, we find that the jet structure can be parameterized as a uniform jet with a luminosity of $\log L_{\rm j}/{\rm erg\ s^{-1}}=52.68^{+0.76}_{-0.33}$ (1$\sigma$) and an opening angle $\theta_{\rm j}=2.10_{-1.28}^{+1.90}$ (50\% confidence level), surrounding by a power-law decay component with an index of ${-4.00^{+0.27}_{-0.37}}$ (1$\sigma$). The inferred local GRB rate is $\rho=9.6$ Gpc$^{-3}$ yr$^{-1}$ by including both the typical GRBs and LL-GRBs as the same population. The typical viewing angle is $3.3^{o}$, and may be $20^{o}\sim30^{o}$ for LL-GRBs. The X-ray luminosity function of the dipole radiation wind can be empirically described by a broken power-law function with indices $\beta_1=0.78^{+0.16}_{-0.15}$ and $\beta_2>1.6$ broken at $\log L_{b, w}/{\rm erg\ s^{-1}}=48.51^{+0.53}_{-0.65}$. In case of that the wind outflow is collimated and co-axial with the GRB jet, we find that the wind structure is similar to the GRB jet, i.e., $\log L_{\rm c, w}/{\rm erg\ s^{-1}}=48.38^{+0.30}_{-0.48}$, $\theta_{\rm c, w}={2.65^{o}}_{-1.19^{o}}^{+0.1.73^{o}}$, and $k_{\rm w}=4.57^{+1.21}_{-0.75}$. The observed correlation between the prompt gamma-ray luminosity and X-ray luminosity of the wind may be resulted from the viewing angle effect in such a jet-wind system. Discussion on survey with the X-ray instruments on board the {\em Einstein\ Probe} mission in the soft X-ray band for the jet and wind emission is also presented.
Despite recent improvement of supervised monocular depth estimation, the lack of high quality pixel-wise ground truth annotations has become a major hurdle for further progress. In this work, we propose a new unsupervised depth estimation method based on pseudo supervision mechanism by training a teacher-student network with knowledge distillation. It strategically integrates the advantages of supervised and unsupervised monocular depth estimation, as well as unsupervised binocular depth estimation. Specifically, the teacher network takes advantage of the effectiveness of binocular depth estimation to produce accurate disparity maps, which are then used as the pseudo ground truth to train the student network for monocular depth estimation. This effectively converts the problem of unsupervised learning to supervised learning. Our extensive experimental results demonstrate that the proposed method outperforms the state-of-the-art on the KITTI benchmark.
The S-stars have been suggested to be a brief transitional phase as stars evolve from oxygen-rich M-type stars into carbon stars, through the dredge up of carbon from He-shell burning. As possible transition objects, S-stars might help achieve a deeper understanding of the chemical evolution as a star ascends the AGB, as well as shed more light on the mass-loss mechanism. We have initiated a large survey of 40 S-stars to observe line emission in common molecules such as CO, SiO, HCN, CS and SiS. Detailed radiative transfer modelling of multi-transition CO radio line observations towards a sample of 40 S-stars shows that the mass-loss rate distribution of S-stars is consistent with those found for M-type AGB stars and carbon stars. Initial results from modelling of the circumstellar SiO emission are also presented.
We demonstrate a graphene-based Salisbury screen consisting of a single layer of graphene placed in close proximity to a gold back reflector. The light absorption in the screen can be actively tuned by electrically gating the carrier density in the graphene layer with an ionic liquid/gel. The screen was designed to achieve maximum absorption at a target wavelength of 3.2 micrometer by using a 600 nm-thick, non-absorbing silica spacer layer. Spectroscopic reflectance measurements were performed in-situ as a function of gate bias. The changes in the reflectance spectra were analyzed using a Fresnel based transfer matrix model in which graphene was treated as an infinitesimally thin sheet with conductivity given by the Kubo formula. Temporal coupled mode theory was employed to analyze and intuitively understand the observed absorption changes in the Salisbury screen. We achieved ~ 6 % change in the optical absorption of graphene by tuning the applied gate bias from 0.8 V to 2.6 V, where 0.8 V corresponds to graphene's charge neutrality point.
Let D be the circulant digraph with n vertices and connection set {2,3,c}. (Assume D is loopless and has outdegree 3.) Work of S.C.Locke and D.Witte implies that if n is a multiple of 6, c is either (n/2) + 2 or (n/2) + 3, and c is even, then D does not have a hamiltonian cycle. For all other cases, we construct a hamiltonian cycle in D.
We obtain a new coding and decoding method using the generalized Pell $(p,i)$ -numbers. The relations among the code matrix elements, error detection and correction have been established for this coding theory. We give two new blocking algorithms using Pell numbers and generalized Pell $(p,i)$-numbers.
A broadband study of the high redshift blazar S5 0836+71 (z = 2.172) is presented. Multi-frequency light curves show multiple episodes of X-ray and $\gamma$-ray flares, while optical-UV fluxes show little variations. During the GeV outburst, the highest $\gamma$-ray flux measured is (5.22 $\pm$ 1.10) $\times$ 10$^{-6}$ ph cm$^{-2}$ s$^{-1}$ in the range of 0.1-300 GeV, which corresponds to an isotropic $\gamma$-ray luminosity of (1.62 $\pm$ 0.44) $\times$ 10$^{50}$ erg s$^{-1}$, thereby making this as one of the most luminous $\gamma$-ray flare ever observed from any blazar. A fast $\gamma$-ray flux rising time of $\sim$3 hours is also noticed which is probably the first measurement of hour scale variability detected from a high redshift (z > 2) blazar. The various activity states of S5 0836+71 are reproduced under the assumption of single zone leptonic emission model. In all the states, the emission region is located inside the broad line region, and the optical-UV radiation is dominated by the accretion disk emission. The modeling parameters suggests the enhancement in bulk Lorentz factor as a primary cause of the $\gamma$-ray flare. The high X-ray activity with less variable $\gamma$-ray counterpart can be due to emission region to be located relatively closer to the black hole where the dominating energy density of the disk emission results in higher X-ray flux due to inverse-Compton scattering of disk photons.
The distinguishing number (index) $D(G)$ ($D'(G)$) of a graph $G$ is the least integer $d$ such that $G$ has an vertex labeling (edge labeling) with $d$ labels that is preserved only by a trivial automorphism. In this paper we compute these two parameters for some specific graphs. Also we study the distinguishing number and the distinguishing index of corona product of two graphs.
The 3D structure of an active region (AR) filament is studied using nonlinear force-free field (NLFFF) extrapolations based on simultaneous observations at a photospheric and a chromospheric height. To that end, we used the Si I 10827 \AA\ line and the He I 10830 \AA\ triplet obtained with the Tenerife Infrared Polarimeter (TIP) at the VTT (Tenerife). The two extrapolations have been carried out independently from each other and their respective spatial domains overlap in a considerable height range. This opens up new possibilities for diagnostics in addition to the usual ones obtained through a single extrapolation from, typically, a photospheric layer. Among those possibilities, this method allows the determination of an average formation height of the He I 10830 \AA\ signal of \approx 2 Mm above the surface of the sun. It allows, as well, to cross-check the obtained 3D magnetic structures in view of verifying a possible deviation from the force- free condition especially at the photosphere. The extrapolations yield a filament formed by a twisted flux rope whose axis is located at about 1.4 Mm above the solar surface. The twisted field lines make slightly more than one turn along the filament within our box, which results in 0.055 turns/Mm. The convex part of the field lines (as seen from the solar surface) constitute dips where the plasma can naturally be supported. The obtained 3D magnetic structure of the filament depends on the choice of the observed horizontal magnetic field as determined from the 180\circ solution of the azimuth. We derive a method to check for the correctness of the selected 180\circ ambiguity solution.
We study the structure of $r$-uniform hypergraphs containing no Berge cycles of length at least $k$ for $k \leq r$, and determine that such hypergraphs have some special substructure. In particular we determine the extremal number of such hypergraphs, giving an affirmative answer to the conjectured value when $k=r$ and giving a a simple solution to a recent result of Kostochka-Luo when $k < r$.
There are several real spherical models associated with a root arrangement, depending on the choice of a building set. The connected components of these models are manifolds with corners which can be glued together to obtain the corresponding real De Concini-Procesi models. In this paper, starting from any root system Phi with finite Coxeter group W and any W-invariant building set, we describe an explicit realization of the real spherical model as a union of polytopes (nestohedra) which lie inside the chambers of the arrangement. The main point of this realization is that the convex hull of these nestohedra is a larger polytope, a permutonestohedron, equipped with an action of W or also, depending on the building set, of Aut(Phi). The permutonestohedra are natural generalizations of Kapranov's permutoassociahedra.