ShantanuT01/DACTYL-Pretraining huggingface dataset:
We present the results of spectroscopy and CCD photometry of the intermediate-luminosity red transient PSN J13100734+3410514 in the galaxy UGC 8246 performed in February and June 2014 with the Russian 6-meter telescope and SCORPIO spectral camera. Our CCD photometry was continued with the Special Astrophysical Observatory's 1-m telescope till November 2014. The star was discovered in late December 2013 at visual brightness 17.6 mag, which corresponded to the absolute magnitude Mv ~ -12.7, and was identified as a supernova impostor. Spectra taken at the visual brightness level of 19.5 mag show composite triple profiles in the H-alpha and H-beta emission lines. We explain the main component of the profiles as radiation from a photoionized extensive gaseous envelope formed by the stellar wind of the progenitor before the outburst. The other two components are treated as radiation from bipolar ejecta. In Balmer line profiles, there is an evidence for a light echo propagating in the surrounding medium after the outburst. Our spectra contain emissions of He I, Na I, Mg I, numerous Fe II emissions, the strongest of which have P Cyg profiles. There are also [O II], [O III], and [S II] emissions of an H II region associated with the transient. The emissions of the region are superimposed on the star spectrum. The light curves show rapid decline and color reddening. Our observations confirm that the UGC 8246 transient was an explosion of a high-mass LBV star.
Spin filter tunnel junctions are based on selective tunneling of up and down spin electrons controlled through exchange splitting of the band structure of a ferromagnetic insulator. Therefore, spin filter efficiency can be tuned by adjusting exchange strength of the tunnel barrier. We have observed that magnetic field and bias voltage (current) can be used to regulate exchange strength and consequently spin-filter efficiency in tunnel junctions with ferromagnetic DyN and GdN tunnel barrier. In tunnel junctions with DyN barrier we obtained $\sim$37$\%$ spin polarization of tunneling electrons at 11 K due to a small exchange splitting ($ E_{ex}$) $\approx$5.6 meV of the barrier height ($\Phi _0$) $\approx$60 meV. Huge spin-filter efficiency $\sim$97$\%$ was found for tunnel junctions with GdN barrier due to larger $E_{ex}$ $\approx$47 meV. In the presence of an applied magnetic field, barrier height can further split due to magnetic field dependent exchange splitting $ E_{ex}(H)$. The spin filter efficiency in DyN tunnel junctions can be increased up to $\sim$87$\%$ with magnetic field. Electric and magnetic field tuned spin-filter efficiency of these tunnel junctions gives opportunity for practical application of these devices with additional functionality.
The modularity of the partition generating function has many important consequences, for example asymptotics and congruences for $p(n)$. In a series of papers the author and Ono \cite{BO1,BO2} connected the rank, a partition statistic introduced by Dyson, to weak Maass forms, a new class of functions which are related to modular forms and which were first considered in \cite{BF}. Here we do a further step towards understanding how weak Maass forms arise from interesting partition statistics by placing certain 2-marked Durfee symbols introduced by Andrews \cite{An1} into the framework of weak Maass forms. To do this we construct a new class of functions which we call quasiweak Maass forms because they have quasimodular forms as components. As an application we prove two conjectures of Andrews. It seems that this new class of functions will play an important role in better understanding weak Maass forms of higher weight themselves, and also their derivatives. As a side product we introduce a new method which enables us to prove transformation laws for generating functions over incomplete lattices.
Let $p$ be a prime, $K$ a finite extension of $\mathbb Q_p$, and let $G_K$ be the absolute Galois group of $K$. The category of \'etale $(\varphi, \tau)$-modules is equivalent to the category of $p$-adic Galois representations of $G_K$. In this paper, we show that all \'etale $(\varphi, \tau)$-modules are overconvergent; this answers a question of Caruso. Our result is an analogy of the classical overconvergence result of Cherbonnier and Colmez in the setting of \'etale $(\varphi, \Gamma)$-modules. However, our method is completely different from theirs. Indeed, we first show that all $p$-power-torsion representations admit loose crystalline lifts; this allows us to construct certain Kisin models in these torsion representations. We study the structure of these Kisin models, and use them to build an overconvergence basis.
In this paper we apply Shokurov's inductive method to study terminal and canonical singularities. As an easy consequence of the Minimal Model Program we show that for any three-dimensional log terminal singularity there exists some special, so called, plt blow-up. We discuss properties of them and construct some examples.
We study the process of cosmic reionization and estimate the ionizing background in the IGM using the Lyman series absorption in the spectra of the four quasars at 5.7<z<6.3 discovered by the SDSS. We derive the evolution of the ionizing background at high redshifts, using both semi-analytic techniques and cosmological simulations to model the density fluctuations in the IGM. The existence of the complete Ly alpha Gunn-Peterson trough in the spectrum of the z=6.28 quasar SDSS 1030+0524 indicates a photoionization rate Gamma_{-12} at z~6 lower than 0.08, at least a factor of 6 smaller than the value at z~3. The Ly beta and Ly gamma Gunn-Peterson troughs give an even stronger limit Gamma_{-12}<0.02 due to their smaller oscillator strengths, indicating that the ionizing background in the IGM at z~6 is more than 20 times lower than that at z~3. Meanwhile, the volume-averaged neutral hydrogen fraction increases from 10^{-5} at z~3 to >10^{-3} at z~6. At this redshift, the mass-averaged neutral hydrogen fraction is larger than 1%; the mildly overdense regions (delta > 3) are still mostly neutral and the comoving mean free path of ionizing photons is shorter than 8 Mpc. Comparison with simulations of cosmological reionization shows that the observed properties of the IGM at z~6 are typical of those in the era at the end of the overlap stage of reionization when the individual HII regions merge. Thus, z~6 marks the end of the reionization epoch. The redshift of reionization constrains the small scale power of the mass density fluctuations and the star forming efficiency of the first generation of objects.
Usually, in mechanics, we obtain the trajectory of a particle in a given force field by solving Newton's second law with chosen initial conditions. In contrast, through our work here, we first demonstrate how one may analyse the behaviour of a suitably defined family of trajectories of a given mechanical system. Such an approach leads us to develop a mechanics analog following the well-known Raychaudhuri equation largely studied in Riemannian geometry and general relativity. The idea of geodesic focusing, which is more familiar to a relativist, appears to be analogous to the meeting of trajectories of a mechanical system within a finite time. Applying our general results to the case of simple pendula, we obtain relevant quantitative consequences. Thereafter, we set up and perform a straightforward experiment based on a system with two pendula. The experimental results on this system are found to tally well with our proposed theoretical model. In summary, the simple theory, as well as the related experiment, provides us with a way to understand the essence of a fairly involved concept in advanced physics from an elementary standpoint.
We study the one loop effective action for a class of higher spin fields by using a first-quantized description. The latter is obtained by considering spinning particles, characterized by an extended local supersymmetry on the worldline, that can propagate consistently on conformally flat spaces. The gauge fixing procedure for calculating the worldline path integral on a loop is delicate, as the gauge algebra contains nontrivial structure functions. Restricting the analysis on (A)dS backgrounds simplifies the gauge fixing procedure, and allows us to produce a useful representation of the one loop effective action. In particular, we extract the first few heat kernel coefficients for arbitrary even spacetime dimension D and for spin S identified by a curvature tensor with the symmetries of a rectangular Young tableau of D/2 rows and [S] columns.
Self-organizing system is studied whose behavior is governed by field of an order parameter, a fluctuation amplitude of conjugate field and a couple of Grassmannian conjugated fields that define the entropy as a control parameter. Within the framework of self-consistent approach the dependencies of macro- and microscopic susceptibilities as well as memory and nonergodicity parameters are determined as a functions of the intensities of thermal and quenched disorders. Making use of the sandpile model shows that proposed scheme determines the conditions of avalanches formation in self-organized criticality phenomena.
The cosmological constant (lambda) of general relativity is a natural consequence of embedding Einstein's theory in a five-dimensional theory of the type needed for unification. The exact 5D solution for lambda less than 0 shows waves in ordinary 3D space with properties similar to those of de Broglie or matter waves. Here the dispersion relation is derived for matter waves in a toy two-phase model, where regions with lambda less than 0 and lambda greater than 0 average on the large scale to lambda = 0, thus providing in principle a resolution of the cosmological-constant problem. A striking result of the analysis is that the dispersion relation is bimodal, with a well-defined window of high-frequency transmission which effectively defines the speed of light.
In this paper, we study the well-posedness of Poisson-Nernst-Planck system with no-flux boundary condition and singular permanent charges in two dimension. The main difficulty comes from the lack of integrability of singular permanent charges. In order to overcome the difficulty, the main idea is to transform the system into another weighted parabolic system. By choosing suitable weighted spaces, local existence of solutions can be obtained based on a fixed-point argument. Moreover, we also proved global existence by energy estimates under the smallness assumption on initial data.
We develop a method for computing exact one-loop quantum corrections to the energies of static classical backgrounds in renormalizable quantum field theories. We use a continuum density of states formalism to construct a regularized Casimir energy in terms of phase shifts and their Born approximations. This method unambiguously incorporates definite counterterms fixed in the standard way by physical renormalization conditions. The result is a robust computation that can be efficiently implemented both numerically and analytically. We carry out such calculations in models of bosons and fermions in one and three dimensions.
The paper presents a concept/technique to compress and synthesize complex material morphologies that is based on Wang tilings. Specifically, a microstructure is stored in a set of Wang tiles and its reconstruction is performed by means of a stochastic tiling algorithm. A substantial part of the study is devoted to the setup of optimal parameters of the automatic tile design by means of parametric studies with statistical descriptors at heart. The performance of the method is demonstrated on four two-dimensional two-phase target systems, monodisperse media with hard and soft discs, sandstone, and high porosity metallic foam.
The coming decade will be an exciting period for dark energy research, during which astronomers will address the question of what drives the accelerated cosmic expansion as first revealed by type Ia supernova (SN) distances, and confirmed by later observations.   The mystery of dark energy poses a challenge of such magnitude that, as stated by the Dark Energy Task Force (DETF), "nothing short of a revolution in our understanding of fundamental physics will be required to achieve a full understanding of the cosmic acceleration." The lack of multiple complementary precision observations is a major obstacle in developing lines of attack for dark energy theory. This lack is precisely what next-generation surveys will address via the powerful techniques of weak lensing (WL) and baryon acoustic oscillations (BAO) -- galaxy correlations more generally -- in addition to SNe, cluster counts, and other probes of geometry and growth of structure. Because of their unprecedented statistical power, these surveys demand an accurate understanding of the observables and tight control of systematics.   This white paper highlights the opportunities, approaches, prospects, and challenges relevant to dark energy studies with wide-deep multiwavelength photometric redshift surveys. Quantitative predictions are presented for a 20000 sq. deg. ground-based 6-band (ugrizy) survey with 5-sigma depth of r~27.5, i.e., a Stage 4 survey as defined by the DETF.
We systematically investigate the electronic structure, magnetic order, and valence states of $\alpha$-Pu$_{2}$O$_{3}$ (\emph{C}-type) by using first-principles calculations. $\alpha$-Pu$_{2}$O$_{3}$ can be constructed from PuO$_{2}$ by removing 25% oxygen atoms. Our results show that the Pu 5\emph{f} orbitals are further localized after removing ordered oxygen atoms. This phenomenon is demonstrated by the combined fact that (i) the volume per unit cell expands 7% and (ii) the corresponding magnetic moments and valence states for Pu ions increase and decrease, respectively. According to the density of states and charge density distribution analysis, PuO$_{2}$ is found to be more covalent than $\alpha$-Pu$_{2}$O$_{3}$, which is also because of the more localization of 5\emph{f} orbitals in the latter. The calculated lattice constants, bulk modulus, and electronic structures for PuO$_{2}$ and $\alpha$-Pu$_{2}$O$_{3}$ are consistent well with experimental observations.
In the absence of complex astrophysical processes that characterize the reionization era, the 21-cm emission from neutral hydrogen (HI) in the post-reionization epoch is believed to be an excellent tracer of the underlying dark matter distribution. Assuming a background cosmology, it is modelled through (i) a bias function b(k,z), which relates HI to the dark matter distribution and (ii) a mean neutral fraction (x_{HI}) which sets its amplitude. In this paper, we investigate the nature of large scale HI bias. The post-reionization HI is modelled using gravity only N-Body simulations and a suitable prescription for assigning gas to the dark matter halos. Using the simulated bias as the fiducial model for HI distribution at z\leq 4, we have generated a hypothetical data set for the 21-cm angular power spectrum (C_{l}) using a noise model based on parameters of an extended version of the GMRT. The binned C_{l} is assumed to be measured with SNR \gtrsim 4 in the range 400 \leq l \leq 8000 at a fiducial redshift z=2.5. We explore the possibility of constraining b(k) using the Principal Component Analysis (PCA) on this simulated data. Our analysis shows that in the range 0.2 < k < 2 Mpc^{-1}, the simulated data set cannot distinguish between models exhibiting different k dependences, provided 1 \lesssim b(k) \lesssim 2 which sets the 2-sigma limits. This justifies the use of linear bias model on large scales. The largely uncertain x_{HI} is treated as a free parameter resulting in degradation of the bias reconstruction. The given simulated data is found to constrain the fiducial x_{HI} with an accuracy of \sim 4% (2-sigma error). The method outlined here, could be successfully implemented on future observational data sets to constrain b(k,z) and x_{HI} and thereby enhance our understanding of the low redshift Universe.
If a quantum channel or process cannot be described by any measure-and-prepare scheme, we may say the channel is in \textit{quantum domain} (QD) since it can transmit quantum correlations. The concept of QD clarifies the role of quantum channel in quantum information theory based on the local-operation-and-classical-communication (LOCC) paradigm: The quantum channel is only useful if it cannot be simulated by LOCC. We construct a simple scheme to verify that a given physical process or channel is in QD by using two non-orthogonal states. We also consider the application for the experiments such as the transmission or storage of quantum optical coherent states, single-photon polarization states, and squeezed vacuum states.
Shot noise processes have been extensively studied due to their mathematical properties and their relevance in several applications. Here, we consider nonnegative shot noise processes and prove their weak convergence to L\'evy-driven Ornstein-Uhlenbeck (OU), whose features depend on the underlying jump distributions. Among others, we obtain the OU-Gamma and OU-Inverse Gaussian processes, having gamma and inverse gaussian processes as background L\'evy processes, respectively. Then, we derive the necessary conditions guaranteeing the diffusion limit to a Gaussian OU process, show that they are not met unless allowing for negative jumps happening with probability going to zero, and quantify the error occurred when replacing the shot noise with the OU process and the non-Gaussian OU processes. The results offer a new class of models to be used instead of the commonly applied Gaussian OU processes to approximate synaptic input currents, membrane voltages or conductances modelled by shot noise in single neuron modelling.
The origin of magnetic fields in isolated and binary white dwarfs has been investigated in a series of recent papers. One proposal is that magnetic fields are generated through an alpha-omega dynamo during common envelope evolution. Here we present population synthesis calculations showing that this hypothesis is supported by observations of magnetic binaries.
Despite recent progress of automatic medical image segmentation techniques, fully automatic results usually fail to meet the clinical use and typically require further refinement. In this work, we propose a quality-aware memory network for interactive segmentation of 3D medical images. Provided by user guidance on an arbitrary slice, an interaction network is firstly employed to obtain an initial 2D segmentation. The quality-aware memory network subsequently propagates the initial segmentation estimation bidirectionally over the entire volume. Subsequent refinement based on additional user guidance on other slices can be incorporated in the same manner. To further facilitate interactive segmentation, a quality assessment module is introduced to suggest the next slice to segment based on the current segmentation quality of each slice. The proposed network has two appealing characteristics: 1) The memory-augmented network offers the ability to quickly encode past segmentation information, which will be retrieved for the segmentation of other slices; 2) The quality assessment module enables the model to directly estimate the qualities of segmentation predictions, which allows an active learning paradigm where users preferentially label the lowest-quality slice for multi-round refinement. The proposed network leads to a robust interactive segmentation engine, which can generalize well to various types of user annotations (e.g., scribbles, boxes). Experimental results on various medical datasets demonstrate the superiority of our approach in comparison with existing techniques.
Correlated electron states are at the root of many important phenomena including unconventional superconductivity (USC), where electron-pairing arises from repulsive interactions. Computing the properties of correlated electrons, such as the critical temperature $T_c$ for the onset of USC, efficiently and reliably from the microscopic physics with quantitative methods remains a major challenge for almost all models and materials. In this theoretical work we combine matrix product states (MPS) with static mean field (MF) to provide a solution to this challenge for quasi-one-dimensional (Q1D) systems: Two- and three-dimensional (2D/3D) materials comprised of weakly coupled correlated 1D fermions. This MPS+MF framework for the ground state and thermal equilibrium properties of Q1D fermions is developed and validated for attractive Hubbard systems first, and further enhanced via analytical field theory. We then deploy it to compute $T_c$ for superconductivity in 3D arrays of weakly coupled, doped and repulsive Hubbard ladders. The MPS+MF framework thus enables the reliable, quantitative and unbiased study of USC and high-$T_c$ superconductivity - and potentially many more correlated phases - in fermionic Q1D systems from microscopic parameters, in ways inaccessible to previous methods. It opens the possibility of designing deliberately optimized Q1D superconductors, from experiments in ultracold gases to synthesizing new materials.
Our principal aim in the present article is to establish a uniform hybrid bound for individual values on the critical line of Hecke $L$-functions associated with cusp forms over the full modular group. This is rendered in the statement that for $t\ge0$ $$ \eqalignno{H_j(\txt{1\over2}+it)&\ll(\kappa_j+t)^{1/3+\epsilon},& (1.1)\cr H_{j,k}(\txt{1\over2}+it)&\ll (k+t)^{1/3+\epsilon},&(1.2)\cr} $$ with the common notation to be made precise in the course of discussion. Talks on this and relevant results were delivered by the authors at MF Oberwolfach on September 20, 2004, and at General Assembry of Math. Soc. Japan on March 30, 2005.
Blazars, a class of highly variable active galactic nuclei, sometimes exhibit Orphan $\gamma$-ray flares. These flares having high flux only in $\gamma$-ray energies do not show significant variations in flux at lower energies. We study the temporal and spectral profile of these Orphan $\gamma$-ray flares in detail from three $\gamma-ray$ bright blazars, 3C 273, PKS 1510-089 and 3C 279 and also their simultaneous broadband emissions. We find that the variability timescales of the Orphan $\gamma$-ray flares were $(0.96\pm0.28)$ days, $(3.12\pm2.40)$ hr and $(2.16\pm0.72)$ hr, for 3C 273, PKS 1510-089 and 3C 279, respectively. The broadband spectral energy distributions (SEDs) during these flares have been modelled with a leptonic model from two emission regions. This model suggests that Orphan $\gamma$-ray flares might have originated from inverse Compton scattering of relativistic electrons by the seed photons from the broad-line region or dusty torus, which is the first region. While the second broader region, lying further down the jet, could be responsible for X-ray and radio emissions. The possible locations of these emission regions in the jets of the three sources have been estimated from SED modelling.
Topological states of matter were first introduced for non-interacting fermions on an infinite uniform lattice. Since then, substantial effort has been made to generalize these concepts to more complex settings. Recently, local markers have been developed that can describe the topological state of systems without translational symmetry and well-defined gap. However, no local marker for interacting matter has been proposed yet that is capable of directly addressing an interacting system. Here we suggest such a many-body local marker based on the single-particle Green's function. Using this marker we identify topological transitions in finite lattices of a Chern insulator with Anderson disorder and Hubbard interactions. Importantly, our proposal can be straightforwardly generalised to non-equilibrium systems.