ShantanuT01/DACTYL-Pretraining huggingface dataset:
We present a study of two-nucleon scattering in chiral effective field theory with a finite cutoff to next-to-leading order in the chiral expansion. In the proposed scheme, the contributions of the lowest-order interaction to the scattering amplitude are summed up to an arbitrary order, while the corrections beyond leading order are iterated only once. We consider a general form of the regulator for the leading-order potential including local and non-local structures. The main objective of the paper is to address formal aspects of renormalizability within the considered scheme. In particular, we provide a rigorous proof, valid to all orders in the iterations of the leading-order potential, that power-counting breaking terms originating from the integration regions with momenta of the order of the cutoff can be absorbed into the renormalization of the low energy constants of the leading contact interactions. We also demonstrate that the cutoff dependence of the scattering amplitude can be reduced by perturbatively subtracting the regulator artifacts at next-to-leading order. The obtained numerical results for phase shifts in $P$- and higher partial waves confirm the applicability of our scheme for nucleon-nucleon scattering.
(Abridged) This paper introduces the formalism which connects between rotation measure ($\RM$) measurements for extragalactic sources and the cosmological magnetic field power spectrum. It is shown that the amplitude and shape of the cosmological magnetic field power spectrum can be constrained by using a few hundred radio sources, for which Faraday $\RM$s are available. This constraint is of the form $B_{rms} \simless 1 \times [2.6\times10^{-7} cm^{-3}/ \bar n_b] h $ nano-Gauss (nG) on $\sim 10-50 \hmpc$ scales. The constraint is superior to and supersedes any other constraint which come from either CMB fluctuations, Baryonic nucleosyn thesis, or the first two multipoles of the magnetic field expansion. Demonstration of the ability to detect such magnetic fields, using Bayesian statistics, is carried out by constructing simulations of the field and mimicking observations. This procedure also provides error estimates for the derived quantities.   The two main noise contributions due to the Galactic RM and the internal RM are treated in a statistical way. For power indices -1\leq n \leq 1 in a flat cosmology (Omega_m=1) we estimate the signal-to-noise ratio, Q, for limits on the magnetic field B_{rms} on ~50 h^{-1}Mpc scale. Employing one patch of a few square degrees on the sky with source number density n_{src}, an approximate estimate yields Q\simeq 3 \times (B_{rms}/1 {nG})(n_{src}/50 {deg}^{-2}) (2.6\times10^{-7} {cm}^{-3}/ \bar n_b) h $. An all sky coverage, with much sparser, but carefully tailored sample of ~500 sources, yields Q \simeq 1 with the same scaling. An ideal combination of small densely sampled patches and sparse all-sky coverage yields Q\simeq 3 with better constraints for the power index. All of these estimates are corroborated by the simulations.
We investigate the absolute calibration of the EUV Imaging Spectrometer (EIS) on Hinode by comparing EIS full-disk mosaics with irradiance observations from the EUV Variability Experiment (EVE) on the Solar Dynamics Observatory. We also use ultra-deep (>10^5s) exposures of the quiet corona above the limb combined with a simple differential emission measure model to establish new effective area curves that incorporate information from the most recent atomic physics calculations. We find that changes to the EIS instrument sensitivity are a complex function of both time and wavelength. We find that the sensitivity is decaying exponentially with time and that the decay constants vary with wavelength. The EIS short wavelength channel shows significantly longer decay times than the long wavelength channel.
In this paper, we address the task of semantics-guided image outpainting, which is to complete an image by generating semantically practical content. Different from most existing image outpainting works, we approach the above task by understanding and completing image semantics at the scene graph level. In particular, we propose a novel network of Scene Graph Transformer (SGT), which is designed to take node and edge features as inputs for modeling the associated structural information. To better understand and process graph-based inputs, our SGT uniquely performs feature attention at both node and edge levels. While the former views edges as relationship regularization, the latter observes the co-occurrence of nodes for guiding the attention process. We demonstrate that, given a partial input image with its layout and scene graph, our SGT can be applied for scene graph expansion and its conversion to a complete layout. Following state-of-the-art layout-to-image conversions works, the task of image outpainting can be completed with sufficient and practical semantics introduced. Extensive experiments are conducted on the datasets of MS-COCO and Visual Genome, which quantitatively and qualitatively confirm the effectiveness of our proposed SGT and outpainting frameworks.
Weak Gravitational Lensing is a powerful probe of the dark sector of the Universe. One of the main challenges for this technique is the treatment of systematics in the measurement of cosmic shear from galaxy shapes. In an earlier work, Refregier & Amara (2014) have proposed the Monte Carlo Control Loops (MCCL) to overcome these effects using a forward modeling approach. We focus here on one of the control loops in this method, the task of which is the calibration of the shear measurement. For this purpose, we first consider the requirements on the shear systematics for a given survey and propagate them to different systematics terms. We use two one-point statistics to calibrate the shear measurement and six further one-point statistics as diagnostics. We also propagate the systematics levels that we estimate from the one-point functions to the two-point functions for the different systematic error sources. This allows us to assess the consistency between the systematics levels measured in different ways. To test the method, we construct synthetic sky surveys with an area of 1,700 deg$^2$. With some simplifying assumptions, we are able to meet the requirements on the shear calibration for this survey configuration. Furthermore, we account for the total residual shear systematics in terms of the contributing sources. We discuss how this MCCL framework can be applied to current and future weak lensing surveys.
In a recent paper, Andrews, Dixit, and Yee introduced a new spt-type function $\operatorname{spt}_\omega(n)$, which is closely related to Ramanujan's third order mock theta function $\omega(q)$. Garvan and Jennings-Shaffer introduce a crank function which explains congruences for $\operatorname{spt}_\omega(n)$. In this note, we study asymptotic behavior of this crank function and confirm a positivity conjecture of the crank asymptotically. We also study a sign pattern of the crank and congruences for $\operatorname{spt}_\omega(n)$.
We consider multiphoton dynamics of a quantum system composed of a three-state atom (a qutrit) and a single-mode photonic field in the ultrastrong and deep strong coupling regimes, when the coupling strength is comparable to or larger than the oscillator energy scale. We assume a qutrit to be in a polar-$\Lambda $ configuration in which two lower levels have mean dipole moments. Direct multiphoton resonant transitions revealing generalized Rabi oscillations, collapse, and revivals in atomic excitation probabilities for the ultrastrong couplings are studied. In the deep strong coupling regime particular emphasis is placed on the ground state of considering system which exhibits strictly nonclassical properties.
Globular clusters are considerably more complex structures than previously thought, harbouring at least two stellar generations which present clearly distinct chemical abundances. Scenarios explaining the abundance patterns in globular clusters mostly assume that originally the clusters had to be much more massive than today, and that the second generation of stars originates from the gas shed by stars of the first generation (FG). The lack of metallicity spread in most globular clusters further requires that the supernova-enriched gas ejected by the FG is completely lost within ~30 Myr, a hypothesis never tested by means of three-dimensional hydrodynamic simulations. In this paper, we use 3D hydrodynamic simulations including stellar feedback from winds and supernovae, radiative cooling and self-gravity to study whether a realistic distribution of OB associations in a massive proto-GC of initial mass M_tot ~ 10^7 M_sun is sufficient to expel its entire gas content. Our numerical experiment shows that the coherence of different associations plays a fundamental role: as the bubbles interact, distort and merge, they carve narrow tunnels which reach deeper and deeper towards the innermost cluster regions, and through which the gas is able to escape. Our results indicate that after 3 Myr, the feedback from stellar winds is responsible for the removal of ~40% of the pristine gas, and that after 14 Myr, ~ 99% of the initial gas mass has been removed.
In this work, we propose a new solution to 3D human pose estimation in videos. Instead of directly regressing the 3D joint locations, we draw inspiration from the human skeleton anatomy and decompose the task into bone direction prediction and bone length prediction, from which the 3D joint locations can be completely derived. Our motivation is the fact that the bone lengths of a human skeleton remain consistent across time. This promotes us to develop effective techniques to utilize global information across all the frames in a video for high-accuracy bone length prediction. Moreover, for the bone direction prediction network, we propose a fully-convolutional propagating architecture with long skip connections. Essentially, it predicts the directions of different bones hierarchically without using any time-consuming memory units e.g. LSTM). A novel joint shift loss is further introduced to bridge the training of the bone length and bone direction prediction networks. Finally, we employ an implicit attention mechanism to feed the 2D keypoint visibility scores into the model as extra guidance, which significantly mitigates the depth ambiguity in many challenging poses. Our full model outperforms the previous best results on Human3.6M and MPI-INF-3DHP datasets, where comprehensive evaluation validates the effectiveness of our model.
The secular evolution process which slowly transforms the morphology of a given galaxy over its lifetime through mostly internal dynamical mechanisms could naturally account for most of the observed properties of physical galaxies (Zhang 2003a). As an emerging paradigm for galaxy evolution, its dynamical foundations had been established in the past few years (Zhang 1996, 1998, 1999). In this paper, we explore further implications of the secular morphological evolution process in reproducing the well-known scaling relations of galaxies.
Let $\chi_n(t) = (\sum_{i=1}^n X_i^2(t))^{1/2},t\ge0$ be a chi-process with $n$ degrees of freedom where $X_i$'s are independent copies of some generic centered Gaussian process $X$. This paper derives the exact asymptotic behavior of P{\sup_{t\in[0,T]} \chi_n(t)>u} as u \to \infty, where $T$ is a given positive constant, and $g(\cdot)$ is some non-negative bounded measurable function. The case $g(t)\equiv0$ is investigated in numerous contributions by V.I. Piterbarg. Our novel asymptotic results for both stationary and non-stationary $X$are referred to as Piterbarg theorems for chi-processes with trend.
In this work we investigate a generalized tunneling barrier for planar emitters at zero-temperature. We present the evidence of the emergence of a non-Fowler-Nordheim-type general behavior for the field emission current density in the case that the Fermi energy ($\mu$) is comparable with or smaller that the decay width ($d_F$). Therefore, for some non-metals or materials that have very small Fermi energy the standard Fowler-Nordheim-type theory may require a correction. In the opposite regime, i.e., for $\mu$ much larger that $d_F$, we confirm that the conventional theory is suitable for metals.
Spectroscopic techniques, including photoelectron spectroscopy, diffuse reflectance, and x-ray absorption, are used to investigate the electronic structure and the local structure of LaOBiS$_{2-x}$Se$_x$ thermoelectric material. It is found that Se substitution effectively suppresses local distortion, that can be responsible for the increased carrier mobility together with a change in the electronic structure. The results suggest a possible way to control thermoelectric properties by tuning of the local crystal structure of these materials.
We present a theory describing spiral magnets with Dzyaloshinskii-Moriya interaction (DMI) subject to bond disorder at small concentration $c$ of defects. It is assumed that both DMI and exchange coupling are changed on imperfect bonds. Qualitatively the same physical picture is obtained in two models which are considered in detail: B20 cubic helimagnets and layered magnets in which DMI leads to a long-period spiral ordering perpendicular to layers. We find that the distortion of the spiral magnetic ordering around a single imperfect bond is long-range: values of additional turns of spins decay with the distance $r$ to the defect as $1/r^2$ being governed by the Poisson's equation for electric dipole. At finite concentration of randomly distributed imperfect bonds, we calculate correction to the spiral vector. We show that this correction can change the sign of spin chirality even at $c\ll1$ if defects are strong enough. It is demonstrated that impurities lead to a diffuse elastic neutron scattering which has power-law singularities at magnetic Bragg peaks positions. Then, each Bragg peak acquires power-law decaying tails. Corrections are calculated to the magnon energy and to its damping caused by scattering on impurities.
We investigate the deformation and failure mechanisms of phosphorene sheet and nanoribbons under uniaxial tensile strain along the zigzag direction using the density functional tight-binding method. Surprisingly, twin-like deformation occurs homogenously across the phosphorene sheet, which significantly increases its failure strain. Vacancies within the sheet lead to the heterogeneous nucleation of twins at a lower critical strain which, subsequently, propagate across the entire sheet. Twin-like deformation always occurs heterogeneously in phosphorene nanoribbons (with or without vacancies). Propagation of the twins is interrupted by fracture which initiates along the ribbon edge. The underlying mechanism is bond breaking between the atoms within phosphorene puckers and simultaneous bond formation between the atoms in neighboring puckers. This unusual deformation behavior in phosphorene may be exploited in novel nano-electronic-mechanical applications.
We apply the compressive sensing lattice dynamics (CSLD) method to calculate phonon dispersion for crystalline solids. While existing methods such as frozen phonon, small displacement, and linear response are routinely applied for phonon calculations, they are considerable more expensive or cumbersome to apply to certain solids, including structures with large unit cells or low symmetry, systems that require more expensive electronic structure treatment, and polar semiconductors/insulators. In the latter case, we propose an approach based on a corrected long-range force constant model with proper treatment of the acoustic sum rule and the symmetric on-site force constant matrix. Our approach is demonstrated to be accurate and efficient for these systems through case studies of NaCl, CeO$_2$, Y$_3$Al$_5$O$_{12}$ and La$_2$Fe$_{14}$B.
We discuss Kondo effect for a general model, describing a quantum impurity with degenerate energy levels, interacting with a gas of itinerant electrons, and derive scaling equation to the second order for such a model. We show how the scaling equation for the spin-anisotropic Kondo model with the power law density of states (DOS) for itinerant electrons follows from the general scaling equation. We introduce the anisotropic Coqblin--Schrieffer model, apply the general method to derive scaling equation for that model for the power law DOS, and integrate the derived equation analytically.
We give an upper bound on the smallest eigenvalue of the adjacency matrix of graphs with no p-cliques.
The Milky Way underwent its last significant merger ten billion years ago, when the Gaia-Enceladus-Sausage (GES) was accreted. Accreted GES stars and progenitor stars born prior to the merger make up the bulk of the inner halo. Even though these two main populations of halo stars have similar $durations$ of star formation prior to their merger, they differ in [$\alpha$/Fe]-[Fe/H] space, with the GES population bending to lower [$\alpha$/Fe] at a relatively low value of [Fe/H]. We use cosmological simulations of a 'Milky Way' to argue that the different tracks of the halo stars through the [$\alpha$/Fe]-[Fe/H] plane are due to a difference in their star formation history and efficiency, with the lower mass GES having its low and constant star formation regulated by feedback whilst the higher mass main progenitor has a higher star formation rate prior to the merger. The lower star formation efficiency of GES leads to lower gas pollution levels, pushing [$\alpha$/Fe]-[Fe/H] tracks to the left. In addition, the increasing star formation rate maintains a higher relative contribution of Type~II SNe to Type~Ia SNe for the main progenitor population that formed during the same time period, thus maintaining a relatively high [$\alpha$/Fe]. Thus the different positions of the downturns in the [$\alpha$/Fe]-[Fe/H] plane for the GES stars are not reflective of different star formation durations, but instead reflect different star formation efficiencies. We argue that cosmological simulations match a wide range of independent observations, breaking degeneracies that exist in simpler models.
In this paper, we consider the nonlinear Schr\"odinger equation with the super critical power of nonlinearity in the attractive case. We give a sufficient condition and a necessary condition to obtain global or blowing up solutions. These conditions coincide in the critical case, thereby extending the results of Weinstein. Furthermore, we improve a blow-up condition.
We use the latest multi-redshift ($z=6.5-8.7$) upper limits on the 21-cm signal from the Murchison Widefield Array (MWA) to explore astrophysical models which are inconsistent with the data. These upper limits are achieved using 298 h of carefully excised data over four observing seasons. To explore these upper limits in the context of reionisation astrophysics, we use 21CMMC. We then connect the disfavoured regions of parameter space to existing observational constraints on reionisation such as high-$z$ galaxy ultra-violet (UV) luminosity functions, background UV photoionisation rate, intergalactic medium (IGM) neutral fraction, the electron scattering optical depth and the soft-band X-ray emissivity. We find the vast majority of models disfavoured by the MWA limits are already inconsistent with existing observational constraints. These inconsistent models arise from two classes of models: (i) `cold' reionisation and (ii) pure matter density fluctuations (i.e. no reionisation). However, a small subsample of models are consistent implying the existing MWA limits provide unique information in disfavouring models of reionisation, albeit extremely weakly. We also provide the first limits on the soft-band X-ray emissivity from galaxies at high redshifts, finding $1\sigma$ lower limits of $\epsilon_{{\rm X},0.5-2~{\rm keV}}\gtrsim10^{34.5}$ erg s$^{-1}$ Mpc$^{-3}$. Finally, we recover 95 per cent disfavoured limits on the IGM spin temperature of $\bar{T}_{\rm S}\lesssim$ 1.3, 1.4, 1.5, 1.8, 2.1, 2.4 K at $z=6.5, 6.8, 7.1, 7.8, 8.2, 8.7$. With this we infer the IGM must have undergone, at the very least, a small amount of X-ray heating. Note, the limits on $\epsilon_{{\rm X},0.5-2~{\rm keV}}$ and $\bar{T}_{\rm S}$ are conditional on the IGM neutral fraction.
Let $\mu_1,... \mu_k$ be $d$-dimensional probability measures in $\R^d$ with mean 0. At each step we choose one of the measures based on the history of the process and take a step according to that measure. We give conditions for transience of such processes and also construct examples of recurrent processes of this type. In particular, in dimension 3 we give the complete picture: every walk generated by two measures is transient and there exists a recurrent walk generated by three measures.
When did galaxies start forming stars? What is the role of distant galaxies in galaxy formation models and the epoch of reionization? What are the conditions in typical star-forming galaxies at redshifts >~4? Why is galaxy evolution dependent on environment? The Spitzer Space Telescope has been a crucial tool for addressing these questions. Accurate knowledge of stellar masses, ages and star formation rates requires measuring rest-frame optical (and ultraviolet) light, which only Spitzer can probe at high redshifts for a sufficiently large sample of typical galaxies. Many of these science goals are the main science drivers for the James Webb Space Telescope, and Spitzer afforded us their first exploration.
This paper seeks to prove the bijectivity of the "Nash mapping" from the set of irreducible components of the scheme parametrizing analytic arcs on an algebraic surface $X$ whose origin is a singular point, into the set of irreducible components of the exceptional locus of a minimal desingularization $X'$ of $X$ when the base field has positive characteristic. The idea is to view the surface as a specialization of another defined over a field of characteristic zero. A number of related results are proved. Among them, the construction of a scheme of arcs for a suitable one parameter family of surfaces which, by using a theorem of M. Artin on lifting of normal surface singularities to characteristic zero, seems a reasonable candidate to be the desired tool. But there are some points, necessary for a complete proof, which are not verified yet.
We present HST and UKIRT spectra and images of the 2 kpc binary quasar LBQS 0103-2753 (z=0.858). The HST images (V- and I-band) show tidal features demonstrating that this system is a major galaxy merger in progress. A two-color composite image brings out knots of star formation along the tidal arc and elsewhere. The infrared spectrum shows that both objects are at the same redshift, and that the discrepant redshift of C IV in component A is a consequence of the BAL absorption in the spectrum of this component. LBQS 0103-2753 is one of the most closely spaced binary QSOs known, and is one of relatively few dual AGN showing confirmed broad emission lines from both components. While statistical studies of binary QSOs suggest that simultaneous fueling of both black holes during a merger may be relatively rare, LBQS 0103-2753 demonstrates that such fueling can occur at high luminosity at a late stage in the merger at nuclear spacing of only a few kpc, without severe obscuration of the nuclei.
The interior near the horizon of an extremal Reissner-Nordstr\"om black hole is taken as an initial state for quantum mechanical tunneling. An instanton is presented that connects this state with a final state describing the presence of several horizons. This is interpreted as a WKB description of fluctuations due to the throat splitting into several components.
We prove an estimate for the large sieve with square moduli which improves a recent result of L. Zhao. Our method uses an idea of D. Wolke and some results from Fourier analysis.