ShantanuT01/DACTYL-Pretraining huggingface dataset:
We calculate the mass and width of the sigma meson in nuclear medium by considering that it couples to two virtual pions and to a pair of nucleon-antinucleon states and to particle-hole states. The mass is calculated by using the spectral function in the Walecka model, finding that it is about 380MeV. In addition, we obtain the value of 340MeV for the width of its spectral function. We find that there is a reduction in the mass value compared with that in vacuum. This result is consistent with those reported by other authors who have used different models predicting a decreasing of the mass as a function of the density.
The quantum anomalous Hall (QAH) effect is sometimes observed in twisted bilayer graphene (tBG) when it is nearly aligned with an encapsulating hexagonal boron nitride (hBN) layer. We propose that the appearance or absence of the QAH effect in individual devices could be related to commensurability between the graphene/graphene and graphene/hBN moir\'e patterns. We identify a series of points in the $(\theta_{\rm GG},\theta_{\rm GBN})$ twist-angle space at which the two moir\'e patterns are commensurate, allowing moir\'e band theory to be applied, and show that the band Chern numbers are in this case sensitive to a rigid in-plane hBN displacement. Given this property, we argue that the QAH effect is likely only when i) the $(\theta_{\rm GG},\theta_{\rm GBN})$ twist-angle-pair is close enough to a commensurate point that the two moir\'e patterns yield a supermoir\'e pattern with a sufficiently long length scale, and ii) the supermoir\'e has a percolating topologically non-trivial QAH phase. For twist angles far from commensurability, the hBN layer acts as a source of disorder that can destroy the QAH effect. Our proposal can explain a number of current experimental observations. Further experimental studies that can test this proposal more directly are suggested.
Motivated by a conjecture put forward by Abramowicz and Bajtlik we reconsider the twin paradox in static spacetimes. According to a well known theorem in Lorentzian geometry the longest timelike worldline between two given points is the unique geodesic line without points conjugate to the initial point on the segment joining the two points. We calculate the proper times for static twins, for twins moving on a circular orbit (if it is a geodesic) around a centre of symmetry and for twins travelling on outgoing and ingoing radial timelike geodesics. We show that the twins on the radial geodesic worldlines are always the oldest ones and we explicitly find the conjugate points (if they exist) outside the relevant segments. As it is of its own mathematical interest, we find general Jacobi vector fields on the geodesic lines under consideration. In the first part of the work we investigate Schwarzschild geometry.
We propose a scheme for symmetrization verification in two-particle systems, based on one-particle detection and state determination. In contrast to previous proposals, it does not follow a Hong-Ou-Mandel-type approach. Moreover, the technique can be used to generate superposition states of single particles.
For spectroscopically confirmed Type Ia supernovae we evaluate models of intrinsic brightness variations with detailed data/Monte Carlo comparisons of the dispersion in the following quantities: Hubble-diagram scatter, color difference (B-V-c) between the true B-V color and the fitted color (c) from the SALT-II light curve model, and photometric redshift residual. The data sample includes 251 ugriz light curves from the 3-season Sloan Digital Sky Survey-II, and 191 griz light curves from the Supernova Legacy Survey 3-year data release. We find that the simplest model of a wavelength-independent (coherent) scatter is not adequate, and that to describe the data the intrinsic scatter model must have wavelength-dependent variations. We use Monte Carlo simulations to examine the standard approach of adding a coherent scatter term in quadrature to the distance-modulus uncertainty in order to bring the reduced chi2 to unity when fitting a Hubble diagram. If the light curve fits include model uncertainties with the correct wavelength dependence of the scatter, we find that the bias on the dark energy equation of state parameter $w$ is negligible. However, incorrect model uncertainties can lead to a significant bias on the distance moduli, with up to ~0.05 mag redshift-dependent variation. For the recent SNLS3 cosmology results we estimate that this effect introduces an additional systematic uncertainty on $w$ of ~0.02, well below the total uncertainty. However, this uncertainty depends on the samples used, and thus this small $w$-uncertainty is not guaranteed in future cosmology results.
The rates at which the mass and angular momentum of a small black hole change as a result of a tidal interaction with a much larger black hole are calculated to leading order in the small mass ratio. The small black hole is either rotating or nonrotating, and it moves on a circular orbit in the equatorial plane of the large Kerr black hole. The orbits are fully relativistic, and the rates are computed to all orders in the orbital velocity V < V_{isco}, which is limited only by the size of the innermost stable circular orbit. We show that as V \to V_{isco}, the rates take on a limiting value that depends only on V_{isco} and not on the spin parameter of the large black hole.
We classify the enhanced helicity symmetry of the Ehlers group to extended supergravity theories in any dimension. The vanishing character of the pseudo-Riemannian cosets occurring in this analysis is explained in terms of Poincar\'e duality. The latter resides in the nature of regularly embedded quotient subgroups which are non-compact rank preserving.
We carry out a time dependent numerical simulation where both the hydrodynamics and the radiative transfer are coupled together. We consider a two-component accretion flow in which the Keplerian disk is immersed inside an accreting low angular momentum flow (halo) around a black hole. The injected soft photons from the Keplerian disk are reprocessed by the electrons in the halo. We show that in presence of an axisymmetric soft-photon source, the spherically symmetric Bondi flow losses its symmetry and becomes axisymmetric. The low angular momentum flow was observed to slow down close to the axis and formed a centrifugal barrier which added new features into the spectrum. Using the Monte Carlo method, we generated the radiated spectra as functions of the accretion rates. We find that the transitions from a hard state to a soft state is determined by the mass accretion rates of the disk and the halo. We separate out the signature of the bulk motion Comptonization and discuss its significance. We study how the net spectrum is contributed by photons suffering different number of scatterings and spending different amounts of time inside the Compton cloud. We study the directional dependence of the emitted spectrum as well.
Recently, Ambainis gave an O(N^(2/3))-query quantum walk algorithm for element distinctness, and more generally, an O(N^(L/(L+1)))-query algorithm for finding L equal numbers. We point out that this algorithm actually solves a much more general problem, the problem of finding a subset of size L that satisfies any given property. We review the algorithm and give a considerably simplified analysis of its query complexity. We present several applications, including two algorithms for the problem of finding an L-clique in an N-vertex graph. One of these algorithms uses O(N^(2L/(L+1))) edge queries, and the other uses \tilde{O}(N^((5L-2)/(2L+4))), which is an improvement for L <= 5. The latter algorithm generalizes a recent result of Magniez, Santha, and Szegedy, who considered the case L=3 (finding a triangle). We also pose two open problems regarding continuous time quantum walk and lower bounds.
We forecast the potential of the forthcoming X-ray galaxy-cluster survey with eROSITA to constrain dark-energy models. We focus on spatially-flat cosmological scenarios with either constant or time-dependent dark-energy equation-of-state parameters. Fisher information is extracted from the number density and spatial clustering of a photon-count-limited sample of clusters of galaxies up to z~2. We consider different scenarios for the availability of (i) X-ray follow-up observations, (ii) photometric and spectroscopic redshifts, and (iii) accurate knowledge of the observable -- mass relation down to the scale of galaxy groups. With about 125,000 clusters (detected with more than 50 photons and with mass M500c > $10^{13} h^{-1}$ Msun) from an average all-sky exposure of 1.6 ks, eROSITA will give marginalized, one-dimensional, 1-$\sigma$ errors of $\Delta \sigma_8 = \pm~0.008$ ($\sim$1 per cent), $\Delta \Omega_{\rm M} = \pm~0.006$ (2.2 per cent), $\Delta w_0 = \pm~0.07$ (7 per cent), and $\Delta w_a = \pm~0.25$ (optimistic scenario) in combination with (and largely improving upon) current constraints from various cosmological probes (cosmic microwave background, BAOs, Type Ia SNe). Our findings correspond to a dark-energy figure of merit in the range of $116-162$ (after the four years of all-sky survey), making eROSITA one of the first Stage IV experiments to come on line according to the classification of the Dark Energy Task Force. To secure improved mass calibrations and to include high-redshift clusters (z > 0.5) as well as objects at the group-mass scale (M500c < 5 $\times~ 10^{13} h^{-1}$ Msun) will be vital to reach such accuracies.
The new method of investigation of strongly correlated electronic system is presented. Using this method we have derived thee superstring from 2D Hubbard model. The novel expression for generalized supercoherent state has been calculated.
We constructed a far ultraviolet (FUV) all sky map based on observations from the Far Ultraviolet Imaging Spectrograph (FIMS) aboard the Korean microsatellite STSAT-1. For the ~20% of the sky not covered by FIMS observations, predictions from a deep artificial neural network were used. Seven datasets were chosen for input parameters, including five all sky maps of H-alpha, E(B-V), N(HI), and two X-ray bands, with Galactic longitudes and latitudes. 70% of the pixels of the observed FIMS dataset were randomly selected for training as target parameters and the remaining 30% were used for validation. A simple four-layer neural network architecture, which consisted of three convolution layers and a dense layer at the end, was adopted, with an individual activation function for each convolution layer; each convolution layer was followed by a dropout layer. The predicted FUV intensities exhibited good agreement with Galaxy Evolution Explorer (GALEX) observations made in a similar FUV wavelength band for high Galactic latitudes. As a sample application of the constructed map, a dust scattering simulation was conducted with model optical parameters and a Galactic dust model for a region that included observed and predicted pixels. Overall, FUV intensities in the observed and predicted regions were reproduced well.
We introduce the PRISM interstellar medium (ISM) model for thermochemistry and its implementation in the RAMSES-RTZ code. The model includes a non-equilibrium primordial, metal, and molecular chemistry network for 115 species coupled to on-the-fly multifrequency radiation transport. PRISM accurately accounts for the dominant ISM cooling and heating processes in the low-density regime (i.e. $\rho<10^5\ {\rm cm^{-3}}$), including photoheating, photoelectric heating, H$_2$ heating/cooling, cosmic-ray heating, H/He cooling, metal-line cooling, CO cooling, and dust cooling (recombination and gas-grain collisions). We validate the model by comparing 1D equilibrium simulations across six dex in metallicity to existing 1D ISM models in the literature. We apply PRISM to high-resolution (4.5 pc) isolated dwarf galaxy simulations that include state-of-the-art models for star formation and stellar feedback to take an inventory of which cooling and heating processes dominate each different gas phase of a galaxy and to understand the importance of non-equilibrium effects. We show that most of the ISM gas is either close to thermal equilibrium or exhibits a slight cooling instability, while from a chemical perspective, the non-equilibrium electron fraction is often more than three times higher or lower than the equilibrium value, which impacts cooling, heating, and observable emission lines. Electron enhancements are attributed to recombination lags while deficits are shown to be due to rapid cosmic-ray heating. The PRISM model and its coupling to RAMSES-RTZ is applicable to a wide variety of astrophysical scenarios, from cosmological simulations to isolated giant molecular clouds, and is particularly useful for understanding how changes to ISM physics impact observable quantities such as metallic emission lines.
Recent experimental results obtained using $\beta$ decay and isomer spectroscopy indicate an unusual behaviour of the energies of the first excited 2$^{+}$ states in neutron-rich Cd isotopes approaching the N=82 shell closure. To explain the unexpected trend, changes of the nuclear structure far-off stability have been suggested, namely a quenching of the N=82 shell gap already in $^{130}$Cd, only two proton holes away from doubly magic $^{132}$Sn. We study the behaviour of the 2$^+$ energies in the Cd isotopes from N=50 to N=82, i.e. across the entire span of a major neutron shell using modern beyond mean field techniques and the Gogny force. We demonstrate that the observed low 2$^+$ excitation energy in $^{128}$Cd close to the N=82 shell closure is a consequence of the doubly magic character of this nucleus for oblate deformation favoring thereby prolate configurations rather than spherical ones.
Classical lumped components delay lines are built with inductances and capacitors arranged as to match the standard telegraphist line model to obtain slow group velocity lines. In this paper we demonstrate that a practical way to obtain significant group velocity reduction consist in taking advantage of the forbidden bands that present a 1D meta-material. The feasibility of this kind of line, as well as its ability to transmit data are discussed and practically verified.
It is well known that spin nematic phases can appear in either frustrated magnets or in those described by Hamiltonians with large exotic non-Heisenberg terms like biquadratic exchange. We show in the present study that non-frustrated spin-1 1D, 2D and 3D antiferromagnets with single-ion easy-axis anisotropy can show nematic phases in strong magnetic field. For 1D case we support our analytical results by numerical ones.
This small note presents in any dimension a family of cubics that have finite-dimensional motive (in the sense of Kimura). As an illustration, we verify a conjecture of Voevodsky for these cubics, and a conjecture of Murre for the Fano variety of lines of these cubics.
A system of conduction electrons can mediate an indirect magnetic exchange between magnetic impurites. The nonlocal exchange typically competes with the local Kondo screening of the impurity magnetic moments. In case of magnetic adatoms on non-magnetic surfaces this competition is expected to be affected by different confinement effects. Here we study this situation in the regime of intermediate hybridization strengths by means of real-space dynamical mean-field theory for a one-dimensional two-impurity Anderson model. Depending on the presence of a boundary and depending on the system size, a crossover between nonlocal and local singlet formation is observed in corresponding magnetic susceptibilities. The crossover is driven by the strong sensitivity of the Kondo temperature on the local density of states.
Observations made using TESS revealed a sample of low mass stars which show a periodic modulation on a period $<0.2$~d. Surprisingly many of these Ultra Fast Rotating (UFR) stars showed no evidence of flare activity which would be expected from such rapidly rotating stars. We present results from a spectroscopic survey of UFRs using the Nordic Optical Telescope to search for radial velocity variations which could reveal evidence for binarity. Our sample of 29 sources have a photometric period between 0.1-0.2d, cover spectral classes of M0-4V, and show no evidence for flares. We detect only one source with clear radial velocity shifts, with another two having Gaia RUWE values which suggests they are binaries. Further observations reveal the former star possibly contains a brown dwarf companion with a mass of M$_2$>58 M$_{\rm Jup}$ and probability P(M$_2$<90 M$_{\rm Jup}$) = 50\%. There is no evidence for the companion in our spectra, strengthening the case for a brown dwarf companion. We also examine the folded TESS light curves of all our targets, finding at least two are eclipsing binaries and one which has been contaminated by a spatially nearby $\delta$ Sct star. We estimate that around 1/4 of our targets may have been contaminated by short period variable stars. However, the majority of our targets are consistent with being single, low mass stars whose variability is due to starspots. We outline the possible reasons why they are not flare active despite being such rapid rotators.
We perform a kinetic Monte Carlo simulation study of a model of thin film deposition of a two-component mixture in which the activation energy for diffusion of an adatom is additive over its nearest neighbors and in which the interactions between adatoms of the same species are stronger than those between adatoms of different species. The film morphology is investigated for broad ranges of values of the ratios between terrace diffusivity and atomic flux, of the probabilities of detachment from lateral neighbors, and of probabilities of crossing terrace edges. First, we consider a symmetric case in which the interactions of adatoms of the same species are the same for the two components. For low and intermediate temperatures, we show the formation of narrow domains, whose widths are $3$-$30$ lattice constants, which meander in the layers parallel to the substrate, and are connected through very long distances. The domain width depends on the diffusivity-flux ratio of the same species, but it is weakly affected by interactions of different species, so rough estimates of that width can be obtained by using tabulated properties of films with a single component. At high temperatures, the separation of domains is enhanced, but their long distance connectivity is lost, which shows that the formation of the long meandering domains is restricted to a certain range of temperature and flux. Similar morphological features are obtained when the intra-species interactions are different and the adatom diffusion coefficients on terraces of the same species differ up to two orders of magnitude. An approximate scaling relation for the domain width is obtained, but the species with the largest mobility constrains the temperature range in which the long connected domains are found.
The origin of this study is based on not only explicit formulas of finite sums involving higher powers of binomial coefficients, but also explicit evaluations of generating functions for this sums. It should be emphasized that this study contains both new results and literature surveys about some of the related results that have existed so far. With the aid of hypergeometric function, generating functions for a new family of the combinatorial numbers, related to finite sums of powers of binomial coefficients, are constructed. By using these generating functions, a number of new identities have been obtained and at the same time previously well-known formulas and identities have been generalized. Moreover, on this occasion, we identify new families of polynomials including some families of well-known numbers such as Bernoulli numbers, Euler numbers, Stirling numbers, Franel numbers, Catalan numbers, Changhee numbers, Daehee numbers and the others, and also for the polynomials such as the Legendre polynomials, Michael Vowe polynomial, the Mirimanoff polynomial, Golombek type polynomials, and the others. We also give both Riemann and $p$-adic integral representations of these polynomials. Finally, we give combinatorial interpretations of these new families of numbers, polynomials and finite sums of the powers of binomial coefficients. We also give open questions for ordinary generating functions for these numbers.
We present Laneformer, a conceptually simple yet powerful transformer-based architecture tailored for lane detection that is a long-standing research topic for visual perception in autonomous driving. The dominant paradigms rely on purely CNN-based architectures which often fail in incorporating relations of long-range lane points and global contexts induced by surrounding objects (e.g., pedestrians, vehicles). Inspired by recent advances of the transformer encoder-decoder architecture in various vision tasks, we move forwards to design a new end-to-end Laneformer architecture that revolutionizes the conventional transformers into better capturing the shape and semantic characteristics of lanes, with minimal overhead in latency. First, coupling with deformable pixel-wise self-attention in the encoder, Laneformer presents two new row and column self-attention operations to efficiently mine point context along with the lane shapes. Second, motivated by the appearing objects would affect the decision of predicting lane segments, Laneformer further includes the detected object instances as extra inputs of multi-head attention blocks in the encoder and decoder to facilitate the lane point detection by sensing semantic contexts. Specifically, the bounding box locations of objects are added into Key module to provide interaction with each pixel and query while the ROI-aligned features are inserted into Value module. Extensive experiments demonstrate our Laneformer achieves state-of-the-art performances on CULane benchmark, in terms of 77.1% F1 score. We hope our simple and effective Laneformer will serve as a strong baseline for future research in self-attention models for lane detection.
The property of zeta-functions on mixed joint universality in the Voronin's sense states that any two holomorphic functions can be approximated simultaneously with accuracy $\epsilon>0$ by suitable vertical shifts of the pair consisting from the Riemann zeta- and Hurwitz zeta-functions. In [1], it was shown rather general result, i.e., an approximating pair was composed of the Matsumoto zeta-functions' class and the periodic Hurwitz zeta-function. In this paper, we prove that this set of shifts has a strict positive density for all but at most countably many $\epsilon>0$. Also, we give the concluding remarks on certain more general mixed tuple of zeta-functions.