ShantanuT01/DACTYL-Pretraining huggingface dataset:
The F -GAMMA program is a coordinated effort of several observing facilities to understand the AGN/blazar phenomenon via a multi-frequency monitoring approach, especially in the era of Fermi-GST. Some 60 prominent sources are monitored monthly with the Effelsberg 100-m telescope, the IRAM 30-m telescope and more frequently but in a less uniform fashion at the APEX 12-m telescope, covering from 2.64 to 345 GHz. The program has been running since January 2007 and here some of its findings are summarized. (a) There are two major variability patterns that the spectra of sources follow, one spectral-evolution-dominated and one achromatic. (b) The FSRQs show higher brightness temperatures indicative of larger Doppler factors at play and (c) a statistically significant radio-gamma-ray correlation has been found with a method recently suggested by Pavlidou et al. (in prep.).
The discrete subgroup Delta(27) of SU(3) has the interesting multiplication rule 3 X 3 = bar{3} + bar{3} + bar{3}, which is used to obtain near tribimaximal neutrino mixing. Using present neutrino oscillation data as input, this model predicts that the effective mass m_{ee} measured in neutrinoless double beta decay will be 0.14 eV.
In this paper, we provide a general framework for the construction of the Einstein frame within non-linear extensions of the teleparallel equivalents of General Relativity. These include the metric teleparallel and the symmetric teleparallel, but also the general teleparallel theories. We write the actions in a form where we separate the Einstein--Hilbert term, the conformal mode due to the non-linear nature of the theories (which is analogous to the extra degree of freedom in $f(R)$ theories), and the sector that manifestly shows the dynamics arising from the breaking of local symmetries. This frame is then used to study the theories around the Minkowski background, and we show how all the non-linear extensions share the same quadratic action around Minkowski. As a matter of fact, we find that the gauge symmetries that are lost by going to the non-linear generalisations of the teleparallel General Relativity equivalents arise as accidental symmetries in the linear theory around Minkowski. Remarkably, we also find that the conformal mode can be absorbed into a Weyl rescaling of the metric at this order and, consequently, it disappears from the linear spectrum so only the usual massless spin 2 perturbation propagates. These findings unify in a common framework the known fact that no additional modes propagate on Minkowski backgrounds, and we can trace it back to the existence of accidental gauge symmetries of such a background.
Chromospheric activity has been thought to decay smoothly with time and, hence, to be a viable age indicator. Measurements in solar type stars in open clusters seem to point to a different conclusion: chromospheric activity undergoes a fast transition from Hyades level to that of the Sun after about 1 Gyr of main--sequence lifetime and any decaying trend before or after this transition must be much less significant than the short term variations.
The production of high-quality two-dimensional (2D) materials is essential for the ultimate performance of single layers and their hybrids. Hexagonal boron nitride (h-BN) is foreseen to become the key 2D hybrid and packaging material since it is insulating, tight, flat, transparent and chemically inert, though it is difficult to attain in ultimate quality. Here, a new scheme is reported for producing single layer h-BN that shows higher quality and much more uniformity than material from chemical vapor deposition (CVD). We delaminate CVD h-BN from Rh(111) and transfer it to a clean metal surface. The twisting angle between BN and the new substrate yields metastable moir\'e structures. Annealing above 1000 K leads to 2D distillation, i.e., catalyst-assisted BN sublimation from the edges of the transferred layer and subsequent condensation into superior quality h-BN. This provides a new and low-cost way of high-quality 2D material production remote from CVD instrumentation.
The precise measurement of neutrino oscillation parameters is one of the highest priorities in neutrino oscillation physics. To achieve the desired precision, it is necessary to reduce the systematic uncertainties related to neutrino energy reconstruction. An error in energy reconstruction is propagated to all the oscillation parameters, hence a careful estimation of neutrino energy is required. To increase the statistics, neutrino oscillation experiments use heavy nuclear targets like Argon(Z=18). The use of these nuclear targets introduces nuclear effects that severely impact the neutrino energy reconstruction which in turn poses influence in the determination of neutrino oscillation parameters. In this work, we have tried to quantify nuclear effects on the determination of CP phase at DUNE using final state interactions.
We briefly review the growing efforts to set up a unified framework for the description of neutrino interactions with atomic nuclei and nuclear matter, applicable in the broad kinematical region corresponding to neutrino energies ranging between few MeV and few GeV. The emerging picture suggests that the formalism of nuclear many-body theory can be exploited to obtain the neutrino-nucleus cross sections needed for both the interpretation of oscillation signals and simulation of neutrino transport in compact stars.
In characteristic zero, semistable principal bundles on a nonsingular projective curve with a semisimple structure group form a bounded family, as shown by Ramanathan in 1970's using the Narasimhan-Seshadri theorem. This was the first step in his construction of moduli for principal bundles. In this paper we prove boundedness in finite characteristics (other than characteristic 2), when the structure group is a semisimple, simply connected algebraic group of classical type. The main ingredient is an analogue of the Mukai-Sakai theorem (which says that any vector bundle admits a proper subbundle whose degree is `not too small') in the present situation.
Quasi-one-dimensional quantum antiferromagnets formed by a d-dimensional hypercubic lattice of weakly coupled spin-1/2 antiferromagnetic Heisenberg chains are studied by combining exact results in one-dimension and renormalization group analyses of the interchain correlations. It is shown that d-dimensional magnetic long-range order develops at zero-temperature for infinitesimal antiferromagnetic or ferromagnetic interchain couplings. In the presence of weak bond alternations, the order-disorder transition occurs at a finite interchain coupling. Relevances to the lightly doped quantum antiferromagnets and multi-layer quantum Hall systems are discussed.
In this paper we continue our study of a multidimensional random walk with zero mean and finite variance killed on leaving a cone. We suggest a new approach that allows one to construct a positive harmonic function in Lipschitz cones under minimal moment conditions. This approach allows one also to obtain more accurate information about the behaviour of the harmonic function not far from the boundary of the cone. We also prove limit theorems under new moment conditions.
It is shown that under a certain condition on a semimartingale and a time-change, any stochastic integral driven by the time-changed semimartingale is a time-changed stochastic integral driven by the original semimartingale. As a direct consequence, a specialized form of the Ito formula is derived. When a standard Brownian motion is the original semimartingale, classical Ito stochastic differential equations driven by the Brownian motion with drift extend to a larger class of stochastic differential equations involving a time-change with continuous paths. A form of the general solution of linear equations in this new class is established, followed by consideration of some examples analogous to the classical equations. Through these examples, each coefficient of the stochastic differential equations in the new class is given meaning. The new feature is the coexistence of a usual drift term along with a term related to the time-change.
We calculate the one-loop corrections to gauge couplings in N=1 supersymmetric brane world models, which are realized in an type IIA orbifold/orientifold background with several stacks of D6 branes wrapped on 3-cycles with non-vanishing intersections. Contributions arise from both N=1 and N=2 open string subsectors. In contrast to what is known from ordinary orbifold theories, N=1 subsectors give rise to moduli-dependent one-loop corrections.
We propose a new filter, a smooth-$k$ space filter, to use in the Press-Schechter approach to model the dark matter halo mass function which overcomes shortcomings of other filters. We test this against the mass function measured in N-body simulations. We find that the commonly used sharp-$k$ filter fails to reproduce the behaviour of the halo mass function at low masses measured from simulations of models with a sharp truncation in the linear power spectrum. We show that the predictions with our new filter agree with the simulation results over a wider range of halo masses for both damped and undamped power spectra than is the case with the sharp-$k$ and real-space top-hat filters.
We present a novel fundamental effect that for the matter waves the space-averaging free-fall point of quantum particles undergoes a spin-dependent transverse shift in the gravitational field of Earth. This effect is similar to the geometric spin Hall effect (GSHE) [Aiello et al., Phys. Rev. Lett. 103, 100401 (2009)] and can be called gravity-induced GSHE. This effect suggests that there might be violations of the universality of free fall (UFF) or weak equivalence principle (WEP) in the quantum domain.
Recent experiments point to a variety of intermetallic systems which exhibit exotic quadrupolar orders driven by the Kondo coupling between conduction electrons and localized quadrupolar degrees of freedom. Using a Luttinger k.p Hamiltonian for the conduction electrons, we study the impact of such quadrupolar order on their energies and wave functions. We discover that such quadrupolar orders can induce a nontrivial Berry curvature for the conduction electron bands, leading to a nonvanishing optical gyrotropic effect. We estimate the magnitude of the gyrotropic response in a candidate quadrupolar material, PrPb3, and discuss the resulting Faraday rotation in thin films.
In this work, the classical Nelson -- Hadwiger problem is studied which lies on the edge of combinatorial geometry and graph theory. It concerns colorings of distance graphs in $ {\mathbb R}^n $, i.e., graphs such that their vertices are vectors and their edges are pairs of vectors at a distance from a given set of postive numbers apart. A series of new lower bounds are obtained for the chromatic numbers of such graphs with different restrictions on the clique numbers and the girths.
Existing state-of-the-art saliency detection methods heavily rely on CNN-based architectures. Alternatively, we rethink this task from a convolution-free sequence-to-sequence perspective and predict saliency by modeling long-range dependencies, which can not be achieved by convolution. Specifically, we develop a novel unified model based on a pure transformer, namely, Visual Saliency Transformer (VST), for both RGB and RGB-D salient object detection (SOD). It takes image patches as inputs and leverages the transformer to propagate global contexts among image patches. Unlike conventional architectures used in Vision Transformer (ViT), we leverage multi-level token fusion and propose a new token upsampling method under the transformer framework to get high-resolution detection results. We also develop a token-based multi-task decoder to simultaneously perform saliency and boundary detection by introducing task-related tokens and a novel patch-task-attention mechanism. Experimental results show that our model outperforms existing methods on both RGB and RGB-D SOD benchmark datasets. Most importantly, our whole framework not only provides a new perspective for the SOD field but also shows a new paradigm for transformer-based dense prediction models. Code is available at https://github.com/nnizhang/VST.
Current CNN-based super-resolution (SR) methods process all locations equally with computational resources being uniformly assigned in space. However, since missing details in low-resolution (LR) images mainly exist in regions of edges and textures, less computational resources are required for those flat regions. Therefore, existing CNN-based methods involve redundant computation in flat regions, which increases their computational cost and limits their applications on mobile devices. In this paper, we explore the sparsity in image SR to improve inference efficiency of SR networks. Specifically, we develop a Sparse Mask SR (SMSR) network to learn sparse masks to prune redundant computation. Within our SMSR, spatial masks learn to identify "important" regions while channel masks learn to mark redundant channels in those "unimportant" regions. Consequently, redundant computation can be accurately localized and skipped while maintaining comparable performance. It is demonstrated that our SMSR achieves state-of-the-art performance with 41%/33%/27% FLOPs being reduced for x2/3/4 SR. Code is available at: https://github.com/LongguangWang/SMSR.
In this paper we detail the mechanisms that drive substitutional binary diffusion and derive appropriate governing equations. We focus on the one-dimensional case with insulated boundary conditions. Asymptotic expansions are used in order to simplify the problem. We are able to obtain approximate analytical solutions in two distinct cases: the two species diffuse at similar rates, and the two species have largely different diffusion rates. A numerical solution for the full problem is also described.
Let $D$ be a strongly connected balanced bipartite directed graph of order $2a\geq 10$. Let $x,y$ be distinct vertices in $D$. $\{x,y\}$ dominates a vertex $z$ if $x\rightarrow z$ and $y\rightarrow z$; in this case, we call the pair $\{x,y\}$ dominating. In this paper we prove:   {\it If the underlying undirected graph of $D$ is not 2-connected and $max\{d(x), d(y)\}\geq 2a-2$ for every dominating pair of vertices $\{x,y\}$, then   $D$ contains a cycle of length $2a-2$ unless $D$ is isomorphic to a certain digraph of order ten which we specify.
This work is dedicated to the quantization of the light-front Yukawa model in D=1+3 dimensions with higher order derivatives of the scalar field. The problem of the computing Dirac brackets and the (anti-) commutator algebra of interacting fields in the presence of the constraints is discussed. The Dirac method and the Ostrogradski formalism of the higher order derivatives are exploited. The systematic method of obtaining the inverse of the functional Dirac-Bergmann matrix with interactions and higher order derivatives is introduced in two variants. The discussion of applications and details of these two variants are conducted. The results of the quantization in the form of the (anti-) commutator algebra are presented and analyzed with special regard to the structure of the interactions for the light-front Yukawa model, which includes the higher order derivatives.
The Galactic transient X-ray binary MAXI~J1836-194 was discovered on 29th August 2011. Here we make a detailed study of the spectral and timing properties of its 2011 outburst using archival data of RXTE Proportional Counter Array instrument. The evolution of accretion flow dynamics of the source during the outburst through spectral analysis with Chakrabarti-Titarchuk's two-component advective flow (TCAF) solution as a local table model in XSPEC. We also fitted spectra with combined disk blackbody and power-law models and compared it with the TCAF model fitted results. The source is found to be in hard and hard-intermediate spectral states only during entire phase of this outburst. No soft or soft-intermediate spectral states are observed. This could be due to the fact that this object belongs to a special class of sources (e.g., MAXI~J1659-152, Swift~J1753.5-0127, etc.) that have very short orbital periods and that companion is profusely mass-losing or the disk is immersed inside an excretion disk. In these cases, flows in the accretion disk is primarily dominated by low viscous sub-Keplerian flow and the Keplerian rate is not high enough to initiate softer states. Low-frequency quasi-periodic oscillations (QPOs) are observed sporadically although as in normal outbursts of transient black holes, monotonic evolutions of QPO frequency during both rising and declining phases are observed. From the TCAF fits, we find mass of the black hole in the range of $7.5-11~M_\odot$ and from time differences between peaks of the Keplerian and sub-Keplerian accretion rates we obtain viscous timescale for this particular outburst $\sim 10$~days.
We present our statistical analysis of the connection between active galactic nuclei (AGN) variability and physical properties of the central supermassive black hole (SMBH). We constructed optical light curves using data from the QUEST-La Silla AGN variability survey. To model the variability, we used the structure function, among the excess variance and the amplitude from Damp Random Walk (DRW) modeling. For the measurement of SMBH physical properties, we used public spectra from the Sloan Digital Sky Survey (SDSS). Our analysis is based on an original sample of 2345 sources detected in both SDSS and QUEST-La Silla. For 1473 of these sources we could perform a proper measurement of the spectral and variability properties, and 1348 of these sources were classified as variable ($91.5\%$). We found that the amplitude of the variability ($A$) depends solely on the rest frame emission wavelength and the Eddington ratio, where $A$ anti-correlates with both $\lambda_{rest}$ and $L/L_{\text{Edd}}$. This suggests that AGN variability does not evolve over cosmic time, and its amplitude is inversely related to the accretion rate. We found that the logarithmic gradient of the variability ($\gamma$) does not correlate significantly with any SMBH physical parameter, since there is no statistically significant linear regression model with an absolute value of the slope higher than 0.1. Finally, we found that the general distribution of $\gamma$ measured for our sample differs from the distribution of $\gamma$ obtained for light curves simulated from a DRW process. For 20.6\% of the variable sources in our sample, a DRW model is not appropriate to describe the variability, since $\gamma$ differs considerably from the expected value of 0.5.
Extra-galactic X-ray absorption and optical extinction are often found in gamma-ray burst (GRB) afterglows and they could be tracers of both circumburst and host galaxy environments. By performing spectral analyses for spectral energy distribution of 9 short GRB (SGRB) afterglows with known redshift, we investigated a ratio of the equivalent hydrogen column density to the dust extinction, N^{rest}_{H}/A^{rest}_{V}, in the rest frame of each SGRB. We found that the distribution of N^{rest}_{H}/A^{rest}_{V} is systematically smaller than the one for long GRBs, and is roughly consistent with the gas-to-dust ratio in the Milky Way. This result means that the measured gas-to-dust ratio of SGRBs would originate from the interstellar medium in each host galaxy. This scenario supports the prediction that SGRBs occur in non star-forming regions in the host galaxies.
We give a classification theorem for certain four-dimensional families of geometric $\lambda$-adic Galois representations attached to a pure motive. More precisely, we consider families attached to the cohomology of a smooth projective variety defined over $\Q$ with coefficients in a quadratic imaginary field, non-selfdual and with four different Hodge-Tate weights. We prove that the image is as large as possible for almost every $\lambda$ provided that the family is irreducible and not induced from a family of smaller dimension. If we restrict to semistable families an even simpler classification is given. A version of the main result is given for the case where the family is attached to an automorphic form.
Accurately predicting the shape of the HI velocity function of galaxies is regarded widely as a fundamental test of any viable dark matter model. Straightforward analyses of cosmological $N$-body simulations imply that the $\Lambda$CDM model predicts an overabundance of low circular velocity galaxies when compared to observed HI velocity functions. More nuanced analyses that account for the relationship between galaxies and their host haloes suggest that how we model the influence of baryonic processes has a significant impact on HI velocity function predictions. We explore this in detail by modelling HI emission lines of galaxies in the SHARK semi-analytic galaxy formation model, built on the SURFS suite of $\Lambda$CDM $N$-body simulations. We create a simulated ALFALFA survey, in which we apply the survey selection function and account for effects such as beam confusion, and compare simulated and observed HI velocity width distributions, finding differences of $\lesssim 50$%, orders of magnitude smaller than the discrepancies reported in the past. This is a direct consequence of our careful treatment of survey selection effects and, importantly, how we model the relationship between galaxy and halo circular velocity - the HI mass-maximum circular velocity relation of galaxies is characterised by a large scatter. These biases are complex enough that building a velocity function from the observed HI line widths cannot be done reliably.
High resolution spectro-polarimetric observations of a sunspot light bridge by Hinode, reveal small-scale inhomogeneities in the magnetic field and velocity. These inhomogeneities arise as a consequence of a weak, secondary lobe in the Stokes V profile which have a polarity opposite that of the sunspot and very large (>5 km/s) Doppler velocities of both signs, suggesting two distinct types of magnetic anomalies. These two sets of inhomogeneities are highly time-dependent and appear exclusively in the upper half of the light bridge and only after the light bridge is completely formed. Both sets of inhomogeneities appear as patches and can be present independent of the other, next to one another, or spatially separated in a single scan. A two-component inversion of the corresponding spectral profiles indicate that the inhomogeneities occupy a very small fraction, amounting to less than 10 %, of the resolution element. These structures are likely driven by small-scale magneto-convection where they could further interact with the overlying sunspot magnetic field to produce reconnection jets in the chromosphere.
We provide explicit formulae for the noncyclic geometric phases or Pancharatnam phases of neutrino oscillations. Since Pancharatnam phase is a generalization of the Berry phase, our results generalize the previous findings for Berry phase in a recent paper [Phys. Lett. B, 466 (1999) 262]. Unlike the Berry phase, the noncyclic geometric phase offers distinctive advantage in terms of measurement and prediction. In particular, for three-flavor mixing, our explicit formula offers an alternative means of determining the CP-violating phase. Our results can also be extended easily to explore geometric phase associated with neutron-antineutron oscillations.