ShantanuT01/DACTYL-Pretraining huggingface dataset:
We present a static, model-independent, experimental determination of the spin-spin correlation length \xi in a quantum spin system. This is achieved in doped Haldane (i.e., S=1 Heisenberg antiferromagnetic) chain Y(2)BaNi(1-x)Mg(x)O(5) by Y NMR imaging of the staggered magnetization induced around the Mg-impurities (i.e., chain boundaries) by magnetic field. The magnitude of this magnetization is found to decay exponentially with \xi equal to the theoretical prediction for an infinite S=1 chain, and the staggered magnetic moment at the edge site showing the Curie behavior of an effective S=1/2 spin.
A young open cluster is a 2-phase system: an ensemble of stars move in a gaseous medium (the mother molecular cloud). The dynamics and thermodynamics of the system, and so its evolution and final fate (is it stable or unstable?), strongly depends on the mutual feedback between gas and stars. We present an approach which consists in a (simplified) model where stars (N-bodies) move within a gaseous spherical molecular cloud. The two components influence each other through gravity and mass loss. Among other results (role of IMF, SFE, stellar background, etc.), we find that a significant fraction of small clusters can be destroyed even before SN explosion. when a significant amount of massive stars are present.
We present a solution to the decompactification problem of gauge thresholds in chiral heterotic string theories with two large extra dimensions, where supersymmetry is spontaneously broken by the Scherk-Schwarz mechanism. Whenever the Kaluza-Klein scale is much lower than the string scale, the infinite towers of heavy states contribute non-trivially to the renormalisation of gauge couplings, which typically grow linearly with the large volume of the internal space and invalidate perturbation theory. We trace the origin of the decompactification problem to properties of the six dimensional theory obtained in the infinite volume limit and show that thresholds may instead exhibit logarithmic volume dependence and we provide the conditions for this to occur. We illustrate this mechanism with explicit string constructions where the decompactification problem does not occur.
This paper is devoted to the asymptotic analysis of a thin film equation which describes the evolution of a thin liquid droplet on a solid support driven by capillary forces. We propose an analytic framework to rigorously investigate the connection between this model and Tanner's law [22] which claims: the edge velocity of a spreading thin film on a pre-wetted solid is approximately proportional to the cube of the slope at the inflection. More precisely, we investigate the asymptotic limit of the thin film equation when the slippage coefficient is small and at an appropriate time scale (see Equation (8)). We show that the evolution of the droplet can be approximated by a moving free boundary model (the so-called quasi-static approximation) and we present some results pointing to the validity of Tanner's law in that regime. Several papers [5, 6, 10] have previously investigated a similar connection between the thin film equation and Tanner's law either formally or for particular solutions. Our main contribution is the introduction of a new approach to systematically study this problem by finding an equation for the evolution of the apparent support of the droplet (described mathematically by a nonlinear function of the solution).
We present cosmological constraints from a joint cosmic shear analysis of the Kilo-Degree Survey (KV450) and the Dark Energy Survey (DES-Y1), conducted using Complete Orthogonal Sets of E/B-Integrals (COSEBIs). With COSEBIs we isolate any B-modes which have a non-cosmic shear origin and demonstrate the robustness of our cosmological E-mode analysis as no significant B-modes are detected. We highlight how COSEBIs are fairly insensitive to the amplitude of the non-linear matter power spectrum at high $k$-scales, mitigating the uncertain impact of baryon feedback in our analysis. COSEBIs, therefore, allow us to utilise additional small-scale information, improving the DES-Y1 joint constraints on $S_8=\sigma_8(\Omega_{\rm m}/0.3)^{0.5}$ and $\Omega_{\rm m}$ by $20\%$. Adopting a flat $\Lambda$CDM model we find $S_8=0.755^{+0.019}_{-0.021}$, which is in $3.2\sigma$ tension with the Planck Legacy analysis of the cosmic microwave background.
This paper explores a recent idea of Nambu to generate hierarchies among Yukawa couplings in the context of effective supergravity and superstrings models. The Yukawa couplings are homogeneous functions of the moduli and a geometrical constraint between them with a crucial role in the Nambu mechanism is found in a class of models of no-scale type. The Yukawas are dynamical variables at low energy to be determined by a minimization process. (Based on the talk given at ICHEP94, Glasgow, july 1994)
Using field-theoretic renormalization group methods we calculate the equation of state for non-equilibrium systems belonging to the universality class of directed percolation (Gribov process) to second order in epsilon = 4-d. By introducing a parametric representation the result can be written to this order in a very simple form. We use our result to obtain a universal amplitude ratio to second order in epsilon.
This work proposes the combination of multiscale transform with fractal descriptors employed in the classification of gray-level texture images. We apply the space-scale transform (derivative + Gaussian filter) over the Bouligand-Minkowski fractal descriptors, followed by a threshold over the filter response, aiming at attenuating noise effects caused by the final part of this response. The method is tested in the classification of a well-known data set (Brodatz) and compared with other classical texture descriptor techniques. The results demonstrate the advantage of the proposed approach, achieving a higher success rate with a reduced amount of descriptors.
In this paper, we consider the torsional completion of gravitation for an underlying background filled with Dirac fields, applying it to the problem of neutrino oscillations: we discuss the effects of the induced torsional interactions as corrections to the neutrino oscillation mechanism.
We reveal the highly structured nature of the Milky Way stellar halo within the footprint of the PAndAS photometric survey from blue main sequence and main sequence turn-off stars. We map no fewer than five stellar structures within a heliocentric range of ~5 to 30 kpc. Some of these are known (the Monoceros Ring, the Pisces/Triangulum globular cluster stream), but we also uncover three well-defined stellar structures that could be, at least partly, responsible for the so-called Triangulum/Andromeda and Triangulum/Andromeda 2 features. In particular, we trace a new faint stellar stream located at a heliocentric distance of ~17 kpc. With a surface brightness of \Sigma_V ~ 32-32.5 mag/arcsec^2, it follows an orbit that is almost parallel to the Galactic plane north of M31 and has so far eluded surveys of the Milky Way halo as these tend to steer away from regions dominated by the Galactic disk. Investigating our follow-up spectroscopic observations of PAndAS, we serendipitously uncover a radial velocity signature from stars that have colors and magnitudes compatible with the stream. From the velocity of eight likely member stars, we show that this stellar structure is dynamically cold, with an unresolved velocity dispersion that is lower than 7.1 km/s at the 90-percent confidence level. Along with the width of the stream (300-650 pc), its dynamics points to a dwarf-galaxy-accretion origin. The numerous stellar structures we can map in the Milky Way stellar halo between 5 and 30 kpc and their varying morphology is a testament to the complex nature of the stellar halo at these intermediate distances.
Trove of exotic topoloid structures has recently been predicted by searching for compounds whose calculated band structure crossing points fulfill specific symmetry requirements. Discovery of exciting physical phenomena by experimental studies of such predicted compounds is just around the corner. Yet, the examination of some of these assumed high-symmetry structures suggests that not always will assembly of atoms in a configuration that yields exotic topological properties be protected against energy-lowering symmetry breaking modes. Indeed, although bulk topological characteristics lead to protected surface/edge states, nothing protects bulk states from structural instability. The burden of proof for theoretical predictions of exciting physical phenomena should include some compelling hints that such phenomena can live in thermodynamically stable (or near stable) compounds. Herein, we illustrate how the use of the calculated total (electron + ion) energies of candidate structures can remove false-positive predicted topoloids from the list of likely realizable compounds, to the benefit of the much-cherished iterative process of theory-experiment materials discovery.
In order to understand environmental effects on star formation in high-redshift galaxies, we investigate the physical relationships between the star formation activity, stellar mass, and environment for z ~1.2 galaxies in the 2 deg^2 COSMOS field. We estimate star formation using the [OII] emission line and environment from the local galaxy density. Our analysis shows that for massive galaxies M_*>10^10 M_sun, the fraction of [OII] emitters in high-density environments is 1.7 times higher than in low-density environments, while the [OII] emitter fraction does not depend on environment for low-mass M_* < 10^10 M_sun galaxies. In order to understand what drives these trends, we investigate the role of companion galaxies in our sample. We find that the fraction of [OII] emitters in galaxies with companions is 2.4 times as high as that in galaxies without companions at M_* > 10^10 M_sun. In addition, massive galaxies are more likely to have companions in high-density environments. However, although the "number" of star forming galaxies increases for massive galaxies with close companions and in dense environments, the "average" star formation rate of star forming galaxies at a given mass is independent of environment and the presence/absence of a close companion. These results suggest that interactions and/or mergers in high-density environment could induce star formation in massive galaxies at z~1.2, increasing the fraction of star-forming galaxies with M_* > 10^10 M_sun.
A special case of a combinatorial theorem of De Bruijn and Erdos asserts that every noncollinear set of n points in the plane determines at least n distinct lines. Chen and Chvatal suggested a possible generalization of this assertion in metric spaces with appropriately defined lines. We prove this generalization in all metric spaces where each nonzero distance equals 1 or 2.
We obtain the H\"older regularity of time derivative of solutions to the dual semigeostrophic equations in two dimensions when the initial potential density is bounded away from zero and infinity. Our main tool is an interior H\"older estimate in two dimensions for an inhomogeneous linearized Monge-Amp\`ere equation with right hand side being the divergence of a bounded vector field. As a further application of our H\"older estimate, we prove the H\"older regularity of the polar factorization for time-dependent maps in two dimensions with densities bounded away from zero and infinity. Our applications improve previous work by G. Loeper who considered the cases of densities sufficiently close to a positive constant.
We construct a distinguished set of positive and negative energy modes of the Klein-Gordon equation for any Born frame of reference in Minkowski's space-time. Unlike the case of a galilean frame of reference it is unclear whether this set of modes may be an appropriate basis to define the vacuum of a quantized scalar field in an accelerated cavity.
We study a spin-orbital model for 4$d^{1}$ or 5$d^{1}$ Mott insulators in ordered double perovskites with strong spin-orbit coupling. This model is conveniently written in terms of pseudospin and pseudo-orbital operators representing multipoles of the effective $j=3/2$ angular momentum. Similarities between this model and the effective theories of Kitaev materials motivate the proposal of a chiral spin-orbital liquid with Majorana fermion excitations. The thermodynamic and spectroscopic properties of this quantum spin liquid are characterized using parton mean-field theory. The heat capacity, spin-lattice relaxation rate, and dynamic structure factor for inelastic neutron scattering are calculated and compared with the experimental data for the spin liquid candidate Ba$_{2}$YMoO$_{6}$. Moreover, based on a symmetry analysis, we discuss the operators involved in resonant inelastic X-ray scattering (RIXS) amplitudes for double perovskite compounds. In general, the RIXS cross sections allow one to selectively probe pseudospin and pseudo-orbital degrees of freedom. For the chiral spin-orbital liquid in particular, these cross sections provide information about the spectrum for different flavors of Majorana fermions.
We propose a modular and scalable framework for dense coregistration and cosegmentation with two key characteristics: first, we substitute ground truth data with the semantic map output of a classifier; second, we combine this output with population deformable registration to improve both alignment and segmentation. Our approach deforms all volumes towards consensus, taking into account image similarities and label consistency. Our pipeline can incorporate any classifier and similarity metric. Results on two datasets, containing annotations of challenging brain structures, demonstrate the potential of our method.
Structured pruning techniques have achieved great compression performance on convolutional neural networks for image classification task. However, the majority of existing methods are weight-oriented, and their pruning results may be unsatisfactory when the original model is trained poorly. That is, a fully-trained model is required to provide useful weight information. This may be time-consuming, and the pruning results are sensitive to the updating process of model parameters. In this paper, we propose a metric named Average Filter Information Entropy (AFIE) to measure the importance of each filter. It is calculated by three major steps, i.e., low-rank decomposition of the "input-output" matrix of each convolutional layer, normalization of the obtained eigenvalues, and calculation of filter importance based on information entropy. By leveraging the proposed AFIE, the proposed framework is able to yield a stable importance evaluation of each filter no matter whether the original model is trained fully. We implement our AFIE based on AlexNet, VGG-16, and ResNet-50, and test them on MNIST, CIFAR-10, and ImageNet, respectively. The experimental results are encouraging. We surprisingly observe that for our methods, even when the original model is only trained with one epoch, the importance evaluation of each filter keeps identical to the results when the model is fully-trained. This indicates that the proposed pruning strategy can perform effectively at the beginning stage of the training process for the original model.
A neutrino with energy of $\sim$290 TeV, IceCube-170922A, was detected in coincidence with the BL Lac object TXS~0506+056 during enhanced gamma-ray activity, with chance coincidence being rejected at $\sim 3\sigma$ level. We monitored the object in the very-high-energy (VHE) band with the MAGIC telescopes for $\sim$41 hours from 1.3 to 40.4 days after the neutrino detection. Day-timescale variability is clearly resolved. We interpret the quasi-simultaneous neutrino and broadband electromagnetic observations with a novel one-zone lepto-hadronic model, based on interactions of electrons and protons co-accelerated in the jet with external photons originating from a slow-moving plasma sheath surrounding the faster jet spine. We can reproduce the multiwavelength spectra of TXS 0506+056 with neutrino rate and energy compatible with IceCube-170922A, and with plausible values for the jet power of $\sim 10^{45} - 4 \times 10^{46} {\rm erg \ s^{-1}}$. The steep spectrum observed by MAGIC is concordant with internal $\gamma\gamma$ absorption above a few tens of GeV entailed by photohadronic production of a $\sim$290 TeV neutrino, corroborating a genuine connection between the multi-messenger signals. In contrast to previous predictions of predominantly hadronic emission from neutrino sources, the gamma-rays can be mostly ascribed to inverse Compton up-scattering of external photons by accelerated electrons. The X-ray and VHE bands provide crucial constraints on the emission from both accelerated electrons and protons. We infer that the maximum energy of protons in the jet co-moving frame can be in the range $\sim 10^{14}$ to $10^{18}$ eV.
We prove the existence of higher-order topological insulators in: {\it i}) fourfold rotoinversion invariant bulk crystals, and {\it ii}) inversion-symmetric systems with or without an additional three-fold rotation symmetry. These states of matter are characterized by a non-trivial $\mathbb{Z}_2$ topological invariant, which we define in terms of symmetric hybrid Wannier functions of the filled bands, and can be readily calculated from the knowledge of the crystalline symmetry labels of the bulk band structure. The topological invariant determines the generic presence or absence of protected chiral gapless one-dimensional modes localized at the hinges between conventional gapped surfaces.
In this paper we deal with the problem of recovering functions from their spherical mean transform $\mathcal{R}$, which integrates functions on circles in the plane, in case where the centers of the circles of integration are located on a parabola $\mathcal{P}$ while their radii can be chosen arbitrarily. Using our data, on the values of $\mathcal{R}$ on $\mathcal{P}$, we show how to extract its values in the exterior of $\mathcal{P}$ in case where the functions in question have compact support inside $\mathcal{P}$. Hence, one can use known inversion formulas for $\mathcal{R}$ in the exterior of $\mathcal{P}$ in order to obtain a reconstruction formula.
Recent advances in VLBI have led to astrometric accuracy exceeding that of the Gaia mission goals. This chapter describes some important astrophysical problems that can be addressed with sub-milliarcsecond imaging and micro-arcsecond astrometry using the ngVLA with long baselines.
It is shown that the known method to solve the Dirac equation by means of the squaring method, when relying on the scalar function of the form \Phi = e^{-i\epsilon t} e^{ik_{1} x} e^{ik_{2} y} \sin (kz + \alpha) leads to a 4-dimensional space of the Dirac solutions. It is shown that so constructed basis is equivalent to the space of the Dirac states relied on the use of quantum numbers k_{1}, k_{2}, \pm k and helicity operator; linear transformations relating these two spaces are found. Application of the squaring method substantially depends on the choice of representation for the Dirac matrices, some features of this are considered. Peculiarities of applying the squaring method in Majorana representation are investigated as well. The constructed bases are relevant to describe the Casimir effect for Dirac and Weyl fields in the domain restricted by two planes.
In this paper we describe the FIT\textit{spec} code, a data mining tool for the automatic fitting of synthetic stellar spectra. The program uses a database of 27\,000 {\sc cmfgen} models of stellar atmospheres arranged in a six-dimensional (6D) space, where each dimension corresponds to one model parameter. From these models a library of 2\,835\,000 synthetic spectra were generated covering the ultraviolet, optical, and infrared region of the electromagnetic spectrum. Using FIT\textit{spec} we adjust the effective temperature and the surface gravity. From the 6D array we also get the luminosity, the metallicity, and three parameters for the stellar wind: the terminal velocity ($v_\infty$), the $\beta$ exponent of the velocity law, and the clumping filling factor ($F_{\rm cl}$). Finally, the projected rotational velocity ($v\cdot\sin i$) can be obtained from the library of stellar spectra. Validation of the algorithm was performed by analyzing the spectra of a sample of eight O-type stars taken from the {\sc iacob} spectroscopic survey of Northern Galactic OB stars. The spectral lines used for the adjustment of the analyzed stars are reproduced with good accuracy. In particular, the effective temperatures calculated with the FIT\textit{spec} are in good agreement with those derived from spectral type and other calibrations for the same stars. The stellar luminosities and projected rotational velocities are also in good agreement with previous quantitative spectroscopic analyses in the literature. An important advantage of FIT\textit{spec} over traditional codes is that the time required for spectral analyses is reduced from months to a few hours.
We have surveyed the metal-rich spiral galaxy M83 (NGC5236) for its Wolf-Rayet population using VLT-FORS2 narrow-band imaging and follow-up spectroscopy. From a total of 280 candidates identified using HeII 4686 imaging, Multi Object Spectroscopy of 198 sources was carried out, revealing 132 objects containing bona-fide Wolf-Rayet features. From this sample, an exceptional W-R content of 1030 is inferred, with N(WC)/N(WN)=1.3, continuing the trend to larger values at higher metallicity amongst Local Group galaxies. More dramatic is the dominance of late-type WC stars in M83 with N(WC8-9)/N(WC4-7)=9 which we attribute to the sensitivity of the classification line CIII 5696 to mass-loss, providing the strength of WC winds scale with metallicity. One young massive compact cluster, #74 in our catalogue, hosts 20% of the entire galactic population, namely 180 late WC stars and 50 late WN stars.
In the background dynamics of a spatially flat FLRW model of the universe, we investigate an interacting dark energy model in the context of Lyra's geometry. Pressure-less dust is considered as dark matter, mass of which varies with time via scalar field in the sense that decaying of dark matter particles reproduces the scalar field. Here, quintessence scalar field is adopted as dark energy candidate which evolves in exponential potential. Mass of the dark matter particles is also considered to be evolved in exponential function of the scalar field. Cosmological evolution equations are studied in the framework of dynamical systems analysis. Dimension-less variables are chosen properly so that the cosmological evolution equations are converted into an autonomous system of ordinary differential equations. Linear stability is performed to find the nature of critical points by perturbing the system around the critical points in the phase space. Classical stability is also executed by finding out the speed of sound. Dynamical systems explore several viable results which are physically interested in some parameter regions. Late-time scalar field dominated attractors are found by critical points, corresponding to the accelerating universe. Scalar field-displacement vector field scaling solutions are realized that represent late time decelerated universe. Dark energy -dark matter scaling solutions are also exhibited by critical points which correspond to accelerated attractors possessing similar order of energy densities of dark energy and dark matter, that provides the possible solutions of coincidence problem.