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gpus rely on large register files to unlock thread - level parallelism for high throughput. unfortunately, large register files are power hungry, making it important to seek for new approaches to improve their utilization. this paper introduces a new register file organization for efficient register - packing of narrow integer and floating - point operands designed to leverage on advances in static analysis. we show that the hardware / software co - designed register file organization yields a performance improvement of up to 79 %, and 18. 6 %, on average, at a modest output - quality degradation.
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arxiv:2006.05693
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recently, non - autoregressive ( nat ) models predict outputs in parallel, achieving substantial improvements in generation speed compared to autoregressive ( at ) models. while performing worse on raw data, most nat models are trained as student models on distilled data generated by at teacher models, which is known as sequence - level knowledge distillation. an effective training strategy to improve the performance of at models is self - distillation mixup ( sdm ) training, which pre - trains a model on raw data, generates distilled data by the pre - trained model itself and finally re - trains a model on the combination of raw data and distilled data. in this work, we aim to view sdm for nat models, but find directly adopting sdm to nat models gains no improvements in terms of translation quality. through careful analysis, we observe the invalidation is correlated to modeling diversity and confirmation bias between the at teacher model and the nat student models. based on these findings, we propose an enhanced strategy named sdmrt by adding two stages to classic sdm : one is pre - rerank on self - distilled data, the other is fine - tune on filtered teacher - distilled data. our results outperform baselines by 0. 6 to 1. 2 bleu on multiple nat models. as another bonus, for iterative refinement nat models, our methods can outperform baselines within half iteration number, which means 2x acceleration.
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arxiv:2112.11640
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in this work, we construct commutative rings of two variable matrix differential operators that are isomorphic to a ring of meromorphic functions on a rational manifold obtained from the $ cp ^ 1 \ times cp ^ 1 $ by identification of two lines with the pole on a certain rational curve.
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arxiv:0804.0117
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generally ` ` exact ' ' quantum monte carlo computations for the ground state of many bosons make use of importance sampling. the importance sampling is based, either on a guiding function or on an initial variational wave function. here we investigate the need of importance sampling in the case of path integral ground state ( pigs ) monte carlo. pigs is based on a discrete imaginary time evolution of an initial wave function with a non zero overlap with the ground state, that gives rise to a discrete path which is sampled via a metropolis like algorithm. in principle the exact ground state is reached in the limit of an infinite imaginary time evolution, but actual computations are based on finite time evolutions and the question is whether such computations give unbiased exact results. we have studied bulk liquid and solid 4he with pigs by considering as initial wave function a constant, i. e. the ground state of an ideal bose gas. this implies that the evolution toward the ground state is driven only by the imaginary time propagator, i. e. there is no importance sampling. for both the phases we obtain results converging to those obtained by considering the best available variational wave function ( the shadow wave function ) as initial wave function. moreover we obtain the same results even by considering wave functions with the wrong correlations, for instance a wave function of a strongly localized einstein crystal for the liquid phase. this convergence is true not only for diagonal properties such as the energy, the radial distribution function and the static structure factor, but also for off - diagonal ones, such as the one - - body density matrix. from this analysis we conclude that zero temperature pigs calculations can be as unbiased as those of finite temperature path integral monte carlo.
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arxiv:0907.4430
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we establish a family of subspace - based learning method for multi - view learning using the least squares as the fundamental basis. specifically, we investigate orthonormalized partial least squares ( opls ) and study its important properties for both multivariate regression and classification. building on the least squares reformulation of opls, we propose a unified multi - view learning framework to learn a classifier over a common latent space shared by all views. the regularization technique is further leveraged to unleash the power of the proposed framework by providing three generic types of regularizers on its inherent ingredients including model parameters, decision values and latent projected points. we instantiate a set of regularizers in terms of various priors. the proposed framework with proper choices of regularizers not only can recast existing methods, but also inspire new models. to further improve the performance of the proposed framework on complex real problems, we propose to learn nonlinear transformations parameterized by deep networks. extensive experiments are conducted to compare various methods on nine data sets with different numbers of views in terms of both feature extraction and cross - modal retrieval.
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arxiv:2007.05028
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heavy neutral leptons ( $ n $ ) below the kaon mass are severely constrained by cosmology and lab - based searches for their decays in flight. if $ n $ interacts via an additional force, $ n \ to \ nu e ^ + e ^ - $ decays are enhanced and cosmological limits can be avoided. we show that the t2k and microboone neutrino experiments provide the best limits on the mixing of $ n $ with muon - neutrinos, outperforming past - generation experiments, previously thought to dominate. we constrain models with electromagnetically - decaying and long - lived $ n $, such as in a transition - magnetic - moment portal and in a leptophilic axion - like particle portal, invoked to explain the miniboone excess. by considering these models as representative examples, our results show that explanations of the miniboone excess that involve $ e ^ + e ^ - $ pairs from long - lived particles are in tension with t2k, ps191, and microboone data. similarly, these searches also constrain miniboone explanations based on single photons due to the associated $ e ^ + e ^ - $ decay mode via a virtual photon.
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arxiv:2109.03831
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efficient spatiotemporal modeling is an important yet challenging problem for video action recognition. existing state - of - the - art methods exploit neighboring feature differences to obtain motion clues for short - term temporal modeling with a simple convolution. however, only one local convolution is incapable of handling various kinds of actions because of the limited receptive field. besides, action - irrelated noises brought by camera movement will also harm the quality of extracted motion features. in this paper, we propose a temporal saliency integration ( tsi ) block, which mainly contains a salient motion excitation ( sme ) module and a cross - perception temporal integration ( cti ) module. specifically, sme aims to highlight the motion - sensitive area through spatial - level local - global motion modeling, where the saliency alignment and pyramidal motion modeling are conducted successively between adjacent frames to capture motion dynamics with fewer noises caused by misaligned background. cti is designed to perform multi - perception temporal modeling through a group of separate 1d convolutions respectively. meanwhile, temporal interactions across different perceptions are integrated with the attention mechanism. through these two modules, long short - term temporal relationships can be encoded efficiently by introducing limited additional parameters. extensive experiments are conducted on several popular benchmarks ( i. e., something - something v1 & v2, kinetics - 400, ucf - 101, and hmdb - 51 ), which demonstrate the effectiveness of our proposed method.
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arxiv:2106.01088
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in the year 1598 philipp uffenbach published a printed diptych sundial, which is a forerunner of franz ritters horizantal sundial. uffenbach ' s sundial contains apart from the usual information on a sundial ascending signs of the zodiac, several brigthest stars, an almucantar and most important the oldest gnomonic world map known so far. the sundial is constructed for the polar height of 50 1 / 6 degrees, the height of frankfurt / main the town of his citizenship.
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arxiv:1407.0206
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suppose a locally compact group g acts freely and properly on a locally compact hausdorff space x, and let gamma be the induced action on c _ 0 ( x ). we consider a category in which the objects are c * - dynamical systems ( a, g, alpha ) for which there is an equivariant homomorphism of ( c _ 0 ( x ), gamma ) into the multiplier algebra m ( a ). rieffel has shown that such systems are proper and saturated, and hence have a generalized fixed - point algebra a ^ alpha which is morita equivalent to a times _ { alpha, r } g. we show that the assignment ( a, alpha ) maps to a ^ alpha is functorial, and that rieffel ' s morita equivalence is natural in a suitable sense. we then use our results to prove a categorical version of landstad duality which characterizes crossed products by coactions, and to prove that mansfield imprimitivity for crossed products by homogeneous spaces is natural.
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arxiv:0801.0161
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we investigated implications of recently released ` joint light - curve analysis ' ( jla ) supernova ia ( sne ia ) data for dark energy models with time varying equation of state of dark energy, usually expressed as $ w ( z ) $ in terms of variation with corresponding redshift $ z $. from a comprehensive analysis of the jla data, we obtain the observational constraints on the different functional forms of $ w ( z ) $, corresponding to different varying dark energy models often considered in literature, \ textit { viz. } cpl, jbp, ba and logarithmic models. the constraints are expressed in terms of parameters ( $ w _ a, w _ b $ ) appearing in the chosen functional form for $ w ( z ) $, corresponding to each of the above mentioned models. realising dark energy with varying equation of state in terms of a homogeneous scalar field $ \ phi $, with its dynamics driven by a $ k - $ essence lagrangian $ l = vf ( x ) $ with a constant potential $ v $ and a dynamical term $ f ( x ) $ with $ x = ( 1 / 2 ) \ nabla ^ \ mu \ phi \ nabla _ \ mu \ phi $ we reconstructed form of the function $ f ( x ) $. this reconstruction has been performed for different varying dark energy models at best - fit values of parameters ( $ w _ a, w _ b $ ) obtained from analysis of jla data. in the context of $ k - $ essence model, we also investigate the variation of adiabatic sound speed squared, $ c _ s ^ 2 ( z ) $, and obtained the domains in ( $ w _ a, w _ b $ ) parameter space corresponding to the physical bound $ c _ s ^ 2 > 0 $ implying stability of density perturbations.
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arxiv:1902.04315
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the three - phase version of the hybrid chiral bag model, containing the phase of asymptotic freedom, the hadronization phase as well as the intermediate phase of constituent quarks, is proposed. for this model the self - consistent solution, which takes into account the fermion vacuum polarization effects, is found in ( 1 + 1 ) d. within this solution the total energy of the bag, including the one - loop contribution from the dirac ' s sea, is studied as the function of the bag geometry under condition of nonvanishing boson condensate density in the interior region. the existence and uniqueness of the ground state bag configuration, which minimizes the total energy and contains all the three phases, are shown.
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arxiv:hep-th/9912237
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this paper proposes a computationally efficient approach to detecting objects natively in 3d point clouds using convolutional neural networks ( cnns ). in particular, this is achieved by leveraging a feature - centric voting scheme to implement novel convolutional layers which explicitly exploit the sparsity encountered in the input. to this end, we examine the trade - off between accuracy and speed for different architectures and additionally propose to use an l1 penalty on the filter activations to further encourage sparsity in the intermediate representations. to the best of our knowledge, this is the first work to propose sparse convolutional layers and l1 regularisation for efficient large - scale processing of 3d data. we demonstrate the efficacy of our approach on the kitti object detection benchmark and show that vote3deep models with as few as three layers outperform the previous state of the art in both laser and laser - vision based approaches by margins of up to 40 % while remaining highly competitive in terms of processing time.
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arxiv:1609.06666
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using an rotation of yuan, we observe that the gradient graph of any semiconvex function is a liouville manifold, that is, does not admit bounded harmonic functions. as a corollary, we find that any entire solution of the fourth order hamiltonian stationary equation with lagrangian phase angle uniformly larger than the critical angle must be a quadratic.
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arxiv:1505.04152
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we propose a way of defining hamiltonians for quantum field theories without any renormalization procedure. the resulting hamiltonians, called ibc hamiltonians, are mathematically well - defined ( and in particular, ultraviolet finite ) without an ultraviolet cut - off such as smearing out the particles over a nonzero radius ; rather, the particles are assigned radius zero. these hamiltonians agree with those obtained through renormalization whenever both are known to exist. we describe explicit examples of ibc hamiltonians. their definition, which is best expressed in the particle - position representation of the wave function, involves a kind of boundary condition on the wave function, which we call an interior - boundary condition ( ibc ). the relevant configuration space is one of a variable number of particles, and the relevant boundary consists of the configurations with two or more particles at the same location. the ibc relates the value ( or derivative ) of the wave function at a boundary point to the value of the wave function at an interior point ( here, in a sector of configuration space corresponding to a lesser number of particles ).
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arxiv:1505.04847
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we present a simple extension of mssm which provides a unified picture of cosmological baryon asymmetry and dark matter. our model introduces a gauge singlet field $ n $ and a color triplet field $ x $ which couple to the right - - handed quark fields. the out - - of equilibrium decay of the majorana fermion $ n $ mediated by the exchange of the scalar field $ x $ generates adequate baryon asymmetry for $ m _ n \ sim 100 $ gev and $ m _ x \ sim $ tev. the scalar partner of $ n $ ( denoted $ \ tilde { n } _ 1 $ ) is naturally the lightest susy particle as it has no gauge interactions and plays the role of dark matter. $ \ tilde { n } _ 1 $ annihilates into quarks efficiently in the early universe via the exchange of the fermionic $ \ tilde { x } $ field. the model is experimentally testable in ( i ) neutron - - antineutron oscillations with a transition time estimated to be around $ 10 ^ { 10 } $ sec, ( ii ) discovery of colored particles $ x $ at lhc with mass of order tev, and ( iii ) direct dark matter detection with a predicted cross section in the observable range.
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arxiv:hep-ph/0612357
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quasi - periodic pedestal burst instabilities ( pbis ), featuring alternative turbulence suppression and bursts, have been clearly identified by various edge diagnostics during i - mode to h - mode transition in the east tokamak. the radial distribution of the phase perturbation caused by pbi shows that pbi is localized in the pedestal. prior to each pbi, a significant increase of density gradient close to the pedestal top can be clearly distinguished, then the turbulence burst is generated, accompanied by the relaxation of the density profile, and then induces an outward particle flux. the relative density perturbation caused by pbis is about $ 6 \ sim 8 \ % $. statistic analyses show that the pedestal normalized density gradient triggering the first pbi has a threshold value, mostly in the range of $ 22 \ sim 24 $, suggesting that a pbi triggering instability could be driven by the density gradient. and the pedestal normalized density gradient triggering the last pbi is about $ 30 \ sim 40 $ and seems to increase with the loss power and the chord - averaged density. in addition, the frequency of pbi is likely to be inversely proportional to the chord - averaged density and the loss power. these results suggest that pbis and the density gradient prompt increase prior to pbis can be considered as the precursor for controlling i - h transition.
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arxiv:2111.00753
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in this paper we present a novel simulation technique for generating high quality images of any predefined resolution. this method can be used to synthesize sonar scans of size equivalent to those collected during a full - length mission, with across track resolutions of any chosen magnitude. in essence, our model extends generative adversarial networks ( gans ) based architecture into a conditional recursive setting, that facilitates the continuity of the generated images. the data produced is continuous, realistically - looking, and can also be generated at least two times faster than the real speed of acquisition for the sonars with higher resolutions, such as edgetech. the seabed topography can be fully controlled by the user. the visual assessment tests demonstrate that humans cannot distinguish the simulated images from real. moreover, experimental results suggest that in the absence of real data the autonomous recognition systems can benefit greatly from training with the synthetic data, produced by the r2d2 - gans.
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arxiv:2003.01063
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we study the dynamics of an intriguing crossover from a chaotic to a power law state as a function of strain rate within the context of a recently introduced model which reproduces the crossover. while the chaotic regime has a small set of positive lyapunov exponents, interestingly, the scaling regime has a power law distribution of null exponents which also exhibits a power law. the slow manifold analysis of the model shows that while a large proportion of dislocations are pinned in the chaotic regime, most of them are pushed to the threshold of unpinning in the scaling regime, thus providing insight into the mechanism of crossover.
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arxiv:cond-mat/0306570
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hd 209458b was the first transiting planet discovered, and the first for which an atmosphere, in particular nai, was detected. with time, it has become one of the most frequently studied planets, with a large diversity of atmospheric studies using low - and high - resolution spectroscopy. here, we present transit spectroscopy observations of hd 209458b using the harps - n and carmenes spectrographs. we fit the rossiter - mclaughlin effect by combining radial velocity data from both instruments ( nine transits in total ), measuring a projected spin - orbit angle of $ - 1. 6 \ pm0. 3 ~ { \ rm deg } $. we also present the analysis of high - resolution transmission spectroscopy around the nai region at $ 590 ~ { \ rm nm } $, using a total of five transit observations. in contrast to previous studies where atmospheric nai absorption is detected, we find that for all of the nights, whether individually or combined, the transmission spectra can be explained by the combination of the centre - to - limb variation and the rossiter - mclaughlin effect. this is also observed in the time - evolution maps and transmission light curves, but at lower signal - to - noise ratio. other strong lines such as h $ \ alpha $, caii irt, the mgi triplet region, and ki d1 are analysed, and are also consistent with the modelled effects, without considering any contribution from the exoplanet atmosphere. thus, the transmission spectrum reveals no detectablenai absorption in hd 209458b. we discuss how previous pioneering studies of this benchmark object may have overlooked these effects. while for some star - planet systems these effects are small, for other planetary atmospheres the results reported in the literature may require revision.
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arxiv:2002.10595
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the unusual pre - main - sequence binary star named kh 15d undergoes remarkably deep and long - lasting periodic eclipses. some clues about the reason for these eclipses have come from the observed evolution of the system ' s light curve over the last century. here we present ubvri photometry of kh 15d based on photographic plates from various observatories, ranging in time from 1954 to 1997. the system has been variable at the ~ 1 mag level since at least 1965. there is no evidence for color variations, with a typical limit of delta ( b - v ) < 0. 2 mag. we confirm some previously published results that were based on a smaller sample of plates : from approximately 1965 to 1990, the total flux was modulated with the 48 - day orbital period of the binary, but the maximum flux was larger, the fractional variations were smaller, and the phase of minimum flux was shifted by almost a half - cycle relative to the modern light curve. all these results are consistent with the recently proposed theory that kh 15d is being occulted by an inclined, precessing, circumbinary ring.
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arxiv:astro-ph/0412498
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we study the symmetric stochastic $ p $ - stokes system, $ p \ in ( 1, \ infty ) $, in a bounded domain. the results are two - folded. first, we show that in the context of analytically weak solutions the stochastic pressure - - related to non - divergence free stochastic forces - - enjoys almost $ - 1 / 2 $ temporal derivatives on a besov scale. second, we verify that the velocity component ~ $ u $ of strong solutions obeys $ 1 / 2 $ temporal derivatives in an exponential nikolskii space. moreover, we prove that the non - linear symmetric gradient $ v ( \ varepsilon u ) = ( \ kappa + | \ varepsilon u | ) ^ { ( p - 2 ) / 2 } \ varepsilon u $, $ \ kappa \ geq 0 $, has $ 1 / 2 $ temporal derivatives in a nikolskii space.
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arxiv:2209.02796
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we report the experimental observation of a lensing effect on a bose - einstein condensate expanding in a moving 1d optical lattice. the effect of the periodic potential can be described by an effective mass dependent on the condensate quasi - momentum. by changing the velocity of the atoms in the frame of the optical lattice we induce a focusing of the condensate along the lattice direction. the experimental results are compared with the numerical predictions of an effective 1d theoretical model. besides, a precise band spectroscopy of the system is carried out by looking at the real - space propagation of the atomic wavepacket in the optical lattice.
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arxiv:cond-mat/0303626
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we study and implement a simple method, based on the perfectly matched layer approach, to treat non reflecting boundary conditions with the smoothed particles hydrodynamics numerical algorithm. the method is based on the concept of physical damping. we illustrate how it works in the case of 1d and 2d time dependent waves propagating in a finite domain.
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arxiv:1202.5893
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we propose a makefile for developing containerized $ \ latex $ technical documents. the makefile allows the author to execute the code that generates variables, tables and figures ( results ), which are then used during the $ \ latex $ compilation, to produce either the draft ( fast ) or full ( slow ) version of the document. we also present various utilities that aid in automating the results generation and improve the reproducibility of the document. we release an open source repository of a template that uses the makefile and demonstrate its use by developing this paper.
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arxiv:2005.12660
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on the basis of density functional theory calculations we predict weyl points in rhombohedral structure of ptnio $ _ 2 $ having symmorphic symmetry. from the formation energy and phonon calculations, ptnio $ _ 2 $ is found to be structurally stable. the magnetic ground state is ferromagnetic with an effective magnetic moment of 1. 01 $ \ mu _ b $ per unit cell. the electronic structure shows major contributions from pt - $ 5d $, ni - $ 3d $ and o - $ 2p $ orbitals with band crossing close to the fermi level. the orbital contribution around 8 ev above the fermi level are from the pt - $ s, p $ orbitals forming a kagome like electronic structure confirmed by surface fermi surface spectral function. we found 20 pairs of confirmed weyl nodes along the magnetic easy axis [ 100 ]. these results are expected to provide a useful and exciting platform for exploring and understanding the magnetic weyl physics in delafossites.
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arxiv:2212.00579
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we discuss absolute calibration strategies for phase i of the hydrogen epoch of reionization array ( hera ), which aims to measure the cosmological 21 cm signal from the epoch of reionization ( eor ). hera is a drift - scan array with a 10 degree wide field of view, meaning bright, well - characterized point source transits are scarce. this, combined with hera ' s redundant sampling of the uv plane and the modest angular resolution of the phase i instrument, make traditional sky - based and self - calibration techniques difficult to implement with high dynamic range. nonetheless, in this work we demonstrate calibration for hera using point source catalogues and electromagnetic simulations of its primary beam. we show that unmodeled diffuse flux and instrumental contaminants can corrupt the gain solutions, and present a gain smoothing approach for mitigating their impact on the 21 cm power spectrum. we also demonstrate a hybrid sky and redundant calibration scheme and compare it to pure sky - based calibration, showing only a marginal improvement to the gain solutions at intermediate delay scales. our work suggests that the hera phase i system can be well - calibrated for a foreground - avoidance power spectrum estimator by applying direction - independent gains with a small set of degrees of freedom across the frequency and time axes.
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arxiv:1910.12943
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$ s $ - wave bound - states composed of a nucleon ( $ n $ ) and a heavy meson ( $ d $, $ d ^ * $, $ \ bar { b } $ or $ \ bar { b } ^ * $ ) are investigated in both the chiral su ( 3 ) quark model and the extended chiral su ( 3 ) quark model by solving the resonating group method equation. the results reveal that the $ nd $ and $ nd ^ * $ interactions in the corresponding relative $ s $ - wave states are attractive, arising mainly from one boson exchange processes between light quarks. it is shown that these attractions are strong enough to form six $ nd $ and $ nd ^ * $ $ s $ - wave bound states in the extended chiral su ( 3 ) quark model with the binding energies in the range of $ 3 - 45 $ mev, and three $ s $ - wave bound states within the chiral su ( 3 ) quark model with binding energies of $ 2 - 8 $ mev. in particular, the experimentally observed $ \ sigma _ c ( 2800 ) $ is interpreted to be most likely an $ s - $ wave $ nd $ state with the total isopsin $ i = 0 $ and spin - parity $ j ^ p = 1 / 2 ^ - $, while $ \ lambda _ c ( 2940 ) ^ + $ as an $ s - $ wave $ nd ^ * $ state with $ i = 0 $ and $ j ^ p = 3 / 2 ^ - $. further information on the $ nd $ and $ nd ^ * $ interactions in the ( unbound ) scattering kinematics are obtained from the corresponding $ s $ - wave phase shifts. the $ n \ bar { b } $ and $ n \ bar { b } ^ * $ systems are also investigated within the present two models and some $ s - $ wave bound states with binding energies in the range of $ 1 - 60 $ mev are predicted in these systems : six ( in total ) within the extended chiral su ( 3 ) quark model and, four, within the chiral su ( 3 ) quark model.
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arxiv:1903.01207
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a theory of combined interference and interaction effects on the diffusive transport properties of 3d topological insulator surface states is developed. we focus on a slab geometry ( characteristic for most experiments ) and show that interactions between the top and bottom surfaces are important at not too high temperatures. we treat the general case of different surfaces ( different carrier densities, uncorrelated disorder, arbitrary dielectric environment, etc. ). in order to access the low - energy behavior of the system we renormalize the interacting diffusive sigma model in the one loop approximation. it is shown that intersurface interaction is relevant in the renormalization group ( rg ) sense and the case of decoupled surfaces is therefore unstable. an analysis of the emerging rg flow yields a rather rich behavior. we discuss realistic experimental scenarios and predict a characteristic non - monotonic temperature dependence of the conductivity. in the infrared ( low - temperature ) limit, the systems flows into a metallic fixed point. at this point, even initially different surfaces have the same transport properties. investigating topological effects, we present a local expression of the $ \ mathbb z _ 2 $ theta term in the sigma model by first deriving the wess - zumino - witten theory for class diii by means of non - abelian bosonization and then breaking the symmetry down to aii. this allows us to study a response of the system to an external electromagnetic field. further, we discuss the difference between the system of dirac fermions on the top and bottom surfaces of a topological insulator slab and its non - topological counterpart in a double - well structure with strong spin - orbit interaction.
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arxiv:1305.2820
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in this paper, we generalize the results of s. oh ( physics letters a. 644 - 647 \ textbf { 373 } ) to dzyaloshinski - moriya model under nonuniform external magnetic field to investigate the relation between entanglement, geometric phase ( or berry phase ) and quantum phase transition. we use quaternionic representation to relate the geometric phase to the quantum phase transition. for small values of dm parameter, the berry phase is more appropriate than the concurrence measure, while for large values, the concurrence is a good indicator to show the phase transition. on the other hand, by increasing the dm interaction the phase transition occurs for large values of anisotropy parameter. in addition, for small values of magnetic field the concurrence measure is appropriate indicator for quantum phase transition, but for large values of magnetic field the berry phase shows a sharp changes in the phase transition points. the results show that the berry phase and concurrence form a complementary system from phase transition point of view.
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arxiv:1512.04029
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the doping dependence of the themopower, in - plane resistivity rho _ ab ( t ), out - of - plane resistivity rho _ c ( t ), and susceptibility has been systematically measured for high - quality single crystal bi2sr2ca2cu3o10 + delta. we found that the transition temperature tc and pseudogap formation temperature t _ rho _ c *, below which rho _ c shows a typical upturn, do not change from their optimum values in the " overdoped " region, even though doping actually proceeds. this suggests that, in overdoped region, the bulk $ t _ c $ is determined by the always underdoped inner plane, which have a large superconducting gap, while the carriers are mostly doped in the outer planes, which have a large phase stiffness.
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arxiv:cond-mat/0205121
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we introduce $ r $ - diagonal and even operators of second order. we give a formula for the second order free cumulants of the square $ x ^ 2 $ of a second order even element in terms of the second order free cumulants of $ x $. similar formulas are proved for the second order free cumulants of $ aa ^ * $, when $ a $ is a second order $ r $ - diagonal operator. we also show that if $ r $ is second order $ r $ - diagonal and $ b $ is second order free from $ r $, then $ rb $ is also second order $ r $ - diagonal. we present a large number of examples, in particular the limit distribution of products of ginibre matrices. we prove the conjectured formula of dartois and forrester for the fluctuations moments of the product of two independent complex wishart matrices and generalize it to any number of factors.
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arxiv:1912.09873
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consider an arbitrary large population at the present time, originated at an unspecified arbitrary large time in the past, where individuals in the same generation reproduce independently, forward in time, with the same offspring distribution but potentially changing among generations. in other words, the reproduction is driven by a galton - watson process in a varying environment. the genealogy of the current generation backwards in time is uniquely determined by the coalescent point process $ ( a _ i, i \ geq 1 ) $, where $ a _ i $ is the coalescent time between individuals $ i $ and $ i + 1 $. in general, this process is not markov. in constant environment, lambert and popovic ( 2013 ) proposed a markov process of point measures to reconstruct the coalescent point process. we present a counterexample where we show that their process does not have the markov property. the main contribution of this work is to propose a vector valued markov process $ ( b _ i, i \ geq 1 ) $, that reach the goal to reconstruct the genealogy, with finite information for every $ i $. additionally, when the offspring distributions are lineal fractional, we show that the variables $ ( a _ i, i \ geq 1 ) $ are independent and identically distributed.
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arxiv:2202.07084
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domain - wall ( dw ) motion in magnetic nanostrips is intensively studied, in particular because of the possible applications in data storage. in this work, we will investigate a novel method of dw motion using magnetic field pulses, with the precession torque as the driving mechanism. we use a one dimensional ( 1d ) model to show that it is possible to drive dws in out - of - plane materials using the precession torque, and we identify the key parameters that influence this motion. because the dw moves back to its initial position at the end of the field pulse, thereby severely complicating direct detection of the dw motion, depinning experiments are used to indirectly observe the effect of the precession torque. the 1d model is extended to include an energy landscape in order to predict the influence of the precession torque in the depinning experiments. although preliminary experiments did not yet show an effect of the precession torque, our calculations indicate that depinning experiments can be used to demonstrate this novel method of dw motion in out - of - plane materials, which even allows for coherent motion of multiple domains when the dzyaloshinskii - moriya interaction is taken into account.
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arxiv:1610.08852
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in the field of robotics research, a crucial applied problem is the hand - eye calibration issue, which involves solving the matrix equation $ ax = yb $. however, this matrix equation is merely a specific case of the more general dual quaternion matrix equation $ ax - yb = c $, which also holds significant applications in system and control theory. therefore, we in this paper establish the solvability conditions of this generalized hand - eye calibration dual quaternion matrix equation and provide a general expression for its solutions when it is solvable. as an example of applications, we design a scheme for color image encryption and decryption based on this dual quaternion matrix equation. from the experiment, it can be observed that the decrypted images are almost identical to the original images. therefore, the encryption and decryption scheme designed using this dual quaternion matrix equation is highly feasible.
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arxiv:2404.04553
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the discussions on the connection between gravity and thermodynamics attract much attention recently. we consider a static self - gravitating perfect fluid system in $ f ( r ) $ gravity, which is an important theory could explain the accelerated expansion of the universe. we first show that the tolman - oppenheimer - volkoff equation of $ f ( r ) $ theories can be obtained by thermodynamical method in spherical symmetric spacetime. then we prove that the maximum entropy principle is also valid for $ f ( r ) $ gravity in general static spacetimes beyond spherical symmetry. the result shows that if the constraint equation is satisfied and the temperature of fluid obeys tolmans law, the extrema of total entropy implies other components of gravitational equations. conversely, if $ f ( r ) $ gravitational equation hold, the total entropy of the fluid should be extremum. our work suggests a general and solid connection between $ f ( r ) $ gravity and thermodynamics.
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arxiv:1512.05454
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the flow transformation and the generation of vortex structures by a strong magnetic dipole field in a liquid metal duct flow is studied by means of three - dimensional direct numerical simulations. the dipole is considered as the paradigm for a magnetic obstacle which will deviate the streamlines due to lorentz forces acting on the fluid elements. the duct is of square cross - section. the dipole is located above the top wall and is centered in spanwise direction. our model uses the quasi - static approximation which is applicable in the limit of small magnetic reynolds numbers. the analysis covers the stationary flow regime at small hydrodynamic reynolds numbers re as well as the transitional time - dependent regime at higher values which may generate a turbulent flow in the wake of the magnetic obstacle. we present a systematic study of these two basic flow regimes and their dependence on re and on the hartmann number ha, a measure of the strength of the magnetic dipole field. furthermore, three orientations of the dipole are compared : streamwise, spanwise and wall - normal oriented dipole axes. the most efficient generation of turbulence at a fixed distance above the duct follows for the spanwise orientation, which is caused by a certain configuration of hartmann layers and reversed flow at the top plate. the enstrophy in the turbulent wake grows linearly with ha which is connected with a dominance of the wall - normal z - derivative of the streamwise velocity.
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arxiv:1309.3506
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social media platforms disseminate extensive volumes of online content, including true and, in particular, false rumors. previous literature has studied the diffusion of offline rumors, yet more research is needed to understand the diffusion of online rumors. in this paper, we examine the role of lifetime and crowd effects in social media sharing behavior for true vs. false rumors. based on 126, 301 twitter cascades, we find that the sharing behavior is characterized by lifetime and crowd effects that explain differences in the spread of true as opposed to false rumors. all else equal, we find that a longer lifetime is associated with less sharing activities, yet the reduction in sharing is larger for false than for true rumors. hence, lifetime is an important determinant explaining why false rumors die out. furthermore, we find that the spread of false rumors is characterized by herding tendencies ( rather than collective intelligence ), whereby the spread of false rumors becomes proliferated at a larger retweet depth. these findings explain differences in the diffusion dynamics of true and false rumors and further offer practical implications for social media platforms.
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arxiv:2207.03020
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we study the set of possible configurations for a general kinetically constrained model ( kcm ), a non monotone version of the $ \ mathcal { u } $ - bootstrap percolation cellular automata. we solve a combinatorial question that is a generalization of a problem addressed by chung, diaconis and graham in 2001 for a specific one - dimensional kcm, the east model. since the general models we consider are in any dimension and lack the oriented character of the east dynamics, we have to follow a completely different route than the one taken by chung, diaconis and graham. our combinatorial result is used by mar \ ^ ech \ ' e, martinelli and toninelli to complete the proof of a conjecture put forward by morris.
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arxiv:1707.06924
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we introduce quantitative reductions, a novel technique for structuring the space of quantitative games and solving them that does not rely on a reduction to qualitative games. we show that such reductions exhibit the same desirable properties as their qualitative counterparts and additionally retain the optimality of solutions. moreover, we introduce vertex - ranked games as a general - purpose target for quantitative reductions and show how to solve them. in such games, the value of a play is determined only by a qualitative winning condition and a ranking of the vertices. we provide quantitative reductions of quantitative request - response games to vertex - ranked games, thus showing exptime - completeness of solving the former games. furthermore, we exhibit the usefulness and flexibility of vertex - ranked games by showing how to use such games to compute fault - resilient strategies for safety specifications. this work lays the foundation for a general study of fault - resilient strategies for more complex winning conditions
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arxiv:1809.03887
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we have studied the wisps to the north - west of the crab pulsar as part of a multi - wavelength campaign in the visible and in x - rays. optical observations were obtained using the nordic optical telescope in la palma and x - ray observations were made with the chandra x - ray observatory. the observing campaign took place from 2010 october until 2012 september. about once per year we observe wisps forming and peeling off from ( or near ) the region commonly associated with the termination shock of the pulsar wind. we find that the exact locations of the northwestern wisps in the optical and in x - rays are similar but not coincident, with x - ray wisps preferentially located closer to the pulsar. this suggests that the optical and x - ray wisps are not produced by the same particle distribution. our measurements and their implications are interpreted in terms of a doppler - boosted ring model that has its origin in magne - tohydrodynamic ( mhd ) modelling. while the doppler boosting factors inferred from the x - ray wisps are consistent with current mhd simulations of pulsar wind nebulae ( pwn ), the optical boosting factors are not, and typically exceed values from mhd simulations by about a factor of 3.
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arxiv:1301.1321
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it is well known that the existence of a braiding in a monoidal category v allows many structures to be built upon that foundation. these include a monoidal 2 - category v - cat of enriched categories and functors over v, a monoidal bicategory v - mod of enriched categories and modules, a category of operads in v and a 2 - fold monoidal category structure on v. we will begin by focusing our exposition on the first and last in this list due to their ability to shed light on a new question. we ask, given a braiding on v, what non - equal structures of a given kind in the list exist which are based upon the braiding. for instance, what non - equal monoidal structures are available on v - cat, or what non - equal operad structures are available which base their associative structure on the braiding in v. we demonstrate alternative underlying braids that result in an infinite family of associative structures. the external and internal associativity diagrams in the axioms of a 2 - fold monoidal category will provide us with several obstructions that can prevent a braid from underlying an associative structure.
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arxiv:math/0512165
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we give a bibliography of works relating to homogeneous structures in the sense of fra \ " iss \ ' e, and related topics, mainly through 2016, with some narrow updating through 2021. we first give a list arranged by topics, with references to the main bibliogrphay, which follows.
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arxiv:2111.15429
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addressing the origin of the astrophysical neutrino flux observed by icecube is of paramount importance. gamma - ray bursts ( grbs ) are among the few astrophysical sources capable of achieving the required energy to contribute to such neutrino flux through p $ \ gamma $ interactions. in this work, antares data have been used to search for upward going muon neutrinos in spatial and temporal coincidence with 784 grbs occurred from 2007 to 2017. for each grb, the expected neutrino flux has been calculated in the framework of the internal shock model and the impact of the lack of knowledge on the majority of source redshifts and on other intrinsic parameters of the emission mechanism has been quantified. it is found that the model parameters that set the radial distance where shock collisions occur have the largest impact on neutrino flux expectations. in particular, the bulk lorentz factor of the source ejecta and the minimum variability timescale are found to contribute significantly to the grb - neutrino flux uncertainty. for the selected sources, antares data have been analysed, by maximising the discovery probability of the stacking sample through an extended maximum - likelihood strategy. since no neutrino event passed the quality cuts set by the optimisation procedure, 90 \ % confidence level upper limits ( with their uncertainty ) on the total expected diffuse neutrino flux have been derived, according to the model. the grb contribution to the observed diffuse astrophysical neutrino flux around 100 tev is constrained to be less than 10 \ %.
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arxiv:2008.02127
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the ability to tailor laser light on a chip using integrated photonics has allowed for extensive control over fundamental light - matter interactions in manifold quantum systems including atoms, trapped ions, quantum dots, and defect centers. free electrons, enabling high - resolution microscopy for decades, are increasingly becoming the subject of laser - based quantum manipulation. using free - space optical excitation and intense laser pulses, this has led to the observation of free - electron quantum walks, attosecond electron pulses, and imaging of electromagnetic fields. enhancing the interaction with electron beams through chip - based photonics promises unique applications in nanoscale quantum control and sensing, but has yet to enter electron microscopy. here, we merge integrated photonics with electron microscopy, demonstrating coherent phase modulation of an electron beam using a silicon nitride microresonator driven by a continuous - wave laser. the high - q factor ( ~ $ 10 ^ 6 $ ) cavity enhancement and a waveguide designed for phase matching lead to efficient electron - light scattering at unprecedentedly low, few - microwatt optical powers. specifically, we fully deplete the initial electron state at a cavity - coupled power of 6 $ \ mu $ w and create > 500 photon sidebands for only 38 mw in the bus waveguide. moreover, we demonstrate $ \ mu $ ev electron energy gain spectroscopy ( eegs ). providing simultaneous optical and electronic spectroscopy of the resonant cavity, the fiber - coupled photonic structures feature single - mode electron - light interaction with full control over the input and output channels. this approach establishes a versatile framework for exploring free - electron quantum optics, with future developments in strong coupling, local quantum probing, and electron - photon entanglement. our results highlight the potential of integrated photonics to efficiently interface free electrons and light.
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arxiv:2105.03729
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filtering based on singular value decomposition ( svd ) provides substantial separation of clutter, flow and noise in high frame rate ultrasound flow imaging. the use of svd as a clutter filter has greatly improved techniques such as vector flow imaging, functional ultrasound and super - resolution ultrasound localization microscopy. the removal of clutter and noise relies on the assumption that tissue, flow and noise are each represented by different subsets of singular values, so that their signals are uncorrelated and lay on orthogonal sub - spaces. this assumption fails in the presence of tissue motion, for near - wall or microvascular flow, and can be influenced by an incorrect choice of singular value thresholds. consequently, separation of flow, clutter and noise is imperfect, which can lead to image artefacts not present in the original data. temporal and spatial fluctuation in intensity are the commonest artefacts, which vary in appearance and strengths. ghosting and splitting artefacts are observed in the microvasculature where the flow signal is sparsely distributed. singular value threshold selection, tissue motion, frame rate, flow signal amplitude and acquisition length affect the prevalence of these artefacts. understanding what causes artefacts due to svd clutter and noise removal is necessary for their interpretation.
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arxiv:2304.12783
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{ \ mathrm { d } } \ circ ( f _ { \ mathrm { v } } \ circ r _ { 2 } ) & = f _ { \ mathrm { d } } \ circ f _ { \ mathrm { h } } = r _ { 1 }. \ end { aligned } } } identity element : the identity element is i d { \ displaystyle \ mathrm { id } }, as it does not change any symmetry a { \ displaystyle a } when composed with it either on the left or on the right. inverse element : each symmetry has an inverse : i d { \ displaystyle \ mathrm { id } }, the reflections f h { \ displaystyle f _ { \ mathrm { h } } }, f v { \ displaystyle f _ { \ mathrm { v } } }, f d { \ displaystyle f _ { \ mathrm { d } } }, f c { \ displaystyle f _ { \ mathrm { c } } } and the 180° rotation r 2 { \ displaystyle r _ { 2 } } are their own inverse, because performing them twice brings the square back to its original orientation. the rotations r 3 { \ displaystyle r _ { 3 } } and r 1 { \ displaystyle r _ { 1 } } are each other ' s inverses, because rotating 90° and then rotation 270° ( or vice versa ) yields a rotation over 360° which leaves the square unchanged. this is easily verified on the table. in contrast to the group of integers above, where the order of the operation is immaterial, it does matter in d 4 { \ displaystyle \ mathrm { d } _ { 4 } }, as, for example, f h ∘ r 1 = f c { \ displaystyle f _ { \ mathrm { h } } \ circ r _ { 1 } = f _ { \ mathrm { c } } } but r 1 ∘ f h = f d { \ displaystyle r _ { 1 } \ circ f _ { \ mathrm { h } } = f _ { \ mathrm { d } } }. in other words, d 4 { \ displaystyle \ mathrm { d } _ { 4 } } is not abelian. = = history = = the modern concept of an abstract group developed out of several fields of mathematics. the original motivation for group theory was the quest for solutions of polynomial equations
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https://en.wikipedia.org/wiki/Group_(mathematics)
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a ring $ r $ satisfies the { \ it strong rank condition } ( src ) if, for every natural number $ n $, the free $ r $ - submodules of $ r ^ n $ all have rank $ \ leq n $. let $ g $ be a group and $ r $ a ring strongly graded by $ g $ such that the base ring $ r _ 1 $ is a domain. using an argument originated by laurent bartholdi for studying cellular automata, we prove that $ r $ satisfies src if and only if $ r _ 1 $ satisfies src and $ g $ is amenable. the special case of this result for group rings allows us to prove a characterization of amenability involving the group von neumann algebra that was conjectured by wolfgang l \ " uck. in addition, we include two applications to the study of group rings and their modules.
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arxiv:1901.10001
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we provide a rigorous treatment of the inverse scattering transform for the entire toda hierarchy for solutions which are asymptotically close to ( in general ) different finite - gap solutions as $ n \ to \ pm \ infty $.
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arxiv:0905.1800
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in this contribution we report on the perturbative determination of $ \ beta $ - functions and anomalous dimensions for the chiral ising, chiral xy and chiral heisenberg gross - neveu - yukawa model around $ d = 4 $ dimensions at four loops and the first pad \ ' e extrapolation of critical exponents at non - trivial, infrared stable fixed points to $ d = 3 $ to this order. this talk is based on ref. [ zerf : 2017zqi ].
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arxiv:1712.03701
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let $ \ phi $ be analytic and univalent ( { \ it i. e., } one - to - one ) in $ \ mathbb { d } : = \ { z \ in \ mathbb { c } : | z | < 1 \ } $ such that $ \ phi ( \ mathbb { d } ) $ has positive real part, is symmetric with respect to the real axis, starlike with respect to $ \ phi ( 0 ) = 1, $ and $ \ phi ' ( 0 ) > 0 $. a function $ f \ in \ mathcal { c } ( \ phi ) $ if $ 1 + zf ' ' ( z ) / f ' ( z ) \ prec \ phi ( z ), $ and $ f \ in \ mathcal { c } _ { c } ( \ phi ) $ if $ 2 ( zf ' ( z ) ) ' / ( f ( z ) + \ overline { f ( \ bar { z } ) } ) ' \ prec \ phi ( z ) $ for $ z \ in \ mathbb { d } $. in this article, we consider the classes $ \ mathcal { hc } ( \ phi ) $ and $ \ mathcal { hc } _ { c } ( \ phi ) $ consisting of harmonic mappings $ f = h + \ overline { g } $ of the form $ $ h ( z ) = z + \ sum \ limits _ { n = 2 } ^ { \ infty } a _ { n } z ^ { n } \ quad \ mbox { and } \ quad g ( z ) = \ sum \ limits _ { n = 2 } ^ { \ infty } b _ { n } z ^ { n } $ $ in the unit disk $ \ mathbb { d } $, where $ h $ belongs to $ \ mathcal { c } ( \ phi ) $ and $ \ mathcal { c } _ { c } ( \ phi ) $ respectively, with the dilation $ g ' ( z ) = \ alpha z h ' ( z ) $ and $ | \ alpha | < 1 $. using the bohr phenomenon for subordination classes \ cite [ lemma 1 ] { bhowmik - 2018 }, we find the radius $ r _ { f } < 1 $ such that bohr inequality $ $ | z | + \ sum _ { n = 2 } ^ { \ inft
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arxiv:2009.08683
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large thermal changes driven by a magnetic field have been proposed for environmentally friendly energy efficient refrigeration, but only a few materials which suffer hysteresis show these giant magnetocaloric effects. here we create giant and reversible extrinsic magnetocaloric effects in epitaxial films of the ferromagnetic manganite la0. 7ca0. 3mno3 using strain mediated feedback from batio3 substrates near a first - order structural phase transition. our findings should inspire the discovery of giant magnetocaloric effects in a wide range of magnetic materials, and the parallel development of nanostructured bulk samples for practical applications.
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arxiv:1209.6516
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the exponential server timing channel is known to be the simplest, and in some sense canonical, queuing timing channel. the capacity of this infinite - memory channel is known. here, we discuss practical finite - length restrictions on the codewords and attempt to understand the maximal rate that can be achieved for a target error probability. by using markov chain analysis, we prove a lower bound on the maximal channel coding rate achievable at blocklength $ n $ and error probability $ \ epsilon $. the bound is approximated by $ c - n ^ { - 1 / 2 } \ sigma q ^ { - 1 } ( \ epsilon ) $ where $ q $ denotes the q - function and $ \ sigma ^ 2 $ is the asymptotic variance of the underlying markov chain. a closed form expression for $ \ sigma ^ 2 $ is given.
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arxiv:1605.07905
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we investigate the effects of flavor su ( 3 ) - symmetry breaking on the qcd condensates, based on the nonlocal effective chiral action from the instanton vacuum, focusing on the quark - gluon mixed one. we employ two different parameterizations for the dependence of the momentum - dependent dynamical quark mass on the strange current quark mass. we obtain the ratios of the mixed condensates : $ [ < \ bar { s } \ sigma _ { \ mu \ nu } g ^ { \ mu \ nu } s > < \ bar { u } \ sig ma _ { \ mu \ nu } g ^ { \ mu \ nu } u > ] ^ { 1 / 5 } = 0. 87 $. it turns out that the dimensional parameter $ m ^ 2 _ 0 = < \ bar { q } \ sigma _ { \ mu \ nu } g ^ { \ mu \ nu } q > / < \ bar { q } q > = 1. 60 \ sim 1. 92 { \ rm gev } ^ 2 $.
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arxiv:hep-ph/0605093
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in contrast to the well - established technique of rasterization, vectorization of images poses a significant challenge in the field of computer graphics. recent learning - based methods for converting raster images to vector formats frequently suffer from incomplete shapes, redundant path prediction, and a lack of accuracy in preserving the semantics of the original content. these shortcomings severely hinder the utility of these methods for further editing and manipulation of images. to address these challenges, we present deepicon, a novel hierarchical image vectorization network specifically tailored for generating variable - length icon vector graphics based on the raster image input. our experimental results indicate that deepicon can efficiently produce scalable vector graphics ( svgs ) directly from raster images, bypassing the need for a differentiable rasterizer while also demonstrating a profound understanding of the image contents.
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arxiv:2410.15760
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the type iib matrix model is conjectured to describe superstring theory nonperturbatively in terms of ten $ n \ times n $ bosonic traceless hermitian matrices $ a _ \ mu $ ( $ \ mu = 0, \ ldots, 9 $ ), whose eigenvalues correspond to $ ( 9 + 1 ) $ - dimensional space - time. quite often, this model has been investigated in its euclidean version, which is well defined although the $ { \ rm so } ( 9, 1 ) $ lorentz symmetry of the original model is replaced by the $ { \ rm so } ( 10 ) $ rotational symmetry. recently, a well - defined model respecting the lorentz symmetry has been proposed by gauge - fixing the lorentz symmetry nonperturbatively using the faddeev - popov procedure. here we investigate the two models by monte carlo simulations, overcoming the severe sign problem by the lefschetz thimble method, in the case of matrix size $ n = 2 $ omitting fermionic contributions. we add a quadratic term $ \ gamma \, \ mathrm { tr } ( a _ \ mu a ^ \ mu ) $ in the action and calculate the expectation values of rotationally symmetric ( or lorentz symmetric ) observables as a function of the coefficient $ \ gamma $. our results exhibit striking differences between the two models around $ \ gamma = 0 $ and in the $ \ gamma > 0 $ region, associated with the appearance of different saddle points, clearly demonstrating their inequivalence against naive expectations from quantum field theory.
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arxiv:2501.17798
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a rapidly rotating and highly magnetized remnant neutron star ( ns ; magnetar ) could survive from a merger of double nss and drive a powerful relativistic wind. the early interaction of this wind with the previous merger ejecta can lead to shock breakout ( sbo ) emission mainly in ultraviolet and soft x - ray bands, which provides an observational signature for the existence of the remnant magnetar. here we investigate the effect of an anisotropic structure of the merger ejecta on the sbo emission. it is found that bolometric light curve of the sbo emission can be broadened, since the sbo can occur at different times for different directions. in more detail, the profile of the sbo light curve can be highly dependent on the ejecta structure and, thus, we can in principle use the sbo light curves to probe the structure of the merger ejecta in future.
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arxiv:2211.06825
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the recent mathematical literature introduces generalised geometries which are defined by a reduction from the structure group $ so ( d, d ) $ of the vector bundle $ t ^ d \ oplus t ^ { d * } $ to a special subgroup. in this article we show that compactification of iib superstring vacua on 7 - manifolds with two covariantly constant spinors leads to a generalised $ g _ 2 $ - structure associated with a reduction from so ( 7, 7 ) to $ g _ 2 \ times g _ 2 $. we also consider compactifications on 6 - manifolds where analogously we obtain a generalised su ( 3 ) - structure associated with $ su ( 3 ) \ times su ( 3 ) $, and show how these relate to generalised $ g _ 2 $ - structures.
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arxiv:hep-th/0412280
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transfer learning has gained attention in medical image analysis due to limited annotated 3d medical datasets for training data - driven deep learning models in the real world. existing 3d - based methods have transferred the pre - trained models to downstream tasks, which achieved promising results with only a small number of training samples. however, they demand a massive amount of parameters to train the model for 3d medical imaging. in this work, we propose a novel transfer learning framework, called medical transformer, that effectively models 3d volumetric images in the form of a sequence of 2d image slices. to make a high - level representation in 3d - form empowering spatial relations better, we take a multi - view approach that leverages plenty of information from the three planes of 3d volume, while providing parameter - efficient training. for building a source model generally applicable to various tasks, we pre - train the model in a self - supervised learning manner for masked encoding vector prediction as a proxy task, using a large - scale normal, healthy brain magnetic resonance imaging ( mri ) dataset. our pre - trained model is evaluated on three downstream tasks : ( i ) brain disease diagnosis, ( ii ) brain age prediction, and ( iii ) brain tumor segmentation, which are actively studied in brain mri research. the experimental results show that our medical transformer outperforms the state - of - the - art transfer learning methods, efficiently reducing the number of parameters up to about 92 % for classification and
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arxiv:2104.13633
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we consider unambiguous identification of coherent states of electromagnetic field. in particular, we study possible generalizations of an optical setup proposed in m. sedl \ ' { a } k { \ it et al. }, phys. rev. a { \ bf 76 }, 022326 ( 2007 ). we show how the unambiguous identification of coherent states can be performed in a general case when multiple copies of unknown and the reference states are available. we also investigate whether reference states after the measurement can be " recovered " and further used for subsequent unambiguous identification tasks. we show that in spite of the fact that the recovered reference states are disturbed by measurements they can be repeatedly used for unambiguous identifications. we analyze the role of various imperfections in preparation of the unknown and the reference coherent states on the performance of our unambiguous identification setup.
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arxiv:0901.3206
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the systematic study of large - scale networks has unveiled the ubiquitous presence of connectivity patterns characterized by large scale heterogeneities and unbounded statistical fluctuations. these features affect dramatically the behavior of the diffusion processes occurring on networks, determining the ensuing statistical properties of their evolution pattern and dynamics. in this paper, we investigate the role of the large scale properties of the airline transportation network in determining the global evolution of emerging disease. we present a stochastic computational framework for the forecast of global epidemics that considers the complete world - wide air travel infrastructure complemented with census population data. we address two basic issues in global epidemic modeling : i ) we study the role of the large scale properties of the airline transportation network in determining the global diffusion pattern of emerging diseases ; ii ) we evaluate the reliability of forecasts and outbreak scenarios with respect to the intrinsic stochasticity of disease transmission and traffic flows. in order to address these issues we define a set of novel quantitative measures able to characterize the level of heterogeneity and predictability of the epidemic pattern. these measures may be used for the analysis of containment policies and epidemic risk assessment.
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arxiv:q-bio/0507029
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existing methods for simulating individual identities often oversimplify human complexity, which may lead to incomplete or flattened representations. to address this, we introduce spectrum, a grounded framework for constructing authentic llm agent personas by incorporating an individual ' s multidimensional self - concept. spectrum integrates three core components : social identity ( s ), personal identity ( p ), and personal life context ( c ), each contributing distinct yet interconnected aspects of identity. to evaluate spectrum ' s effectiveness in identity representation, we conducted automated and human evaluations. automated evaluations using popular drama characters showed that personal life context ( c ) - derived from short essays on preferences and daily routines - modeled characters ' identities more effectively than social identity ( s ) and personal identity ( p ) alone and performed comparably to the full spc combination. in contrast, human evaluations involving real - world individuals found that the full spc combination provided a more comprehensive self - concept representation than c alone. our findings suggest that while c alone may suffice for basic identity simulation, integrating s, p, and c enhances the authenticity and accuracy of real - world identity representation. overall, spectrum offers a structured approach for simulating individuals in llm agents, enabling more personalized human - ai interactions and improving the realism of simulation - based behavioral studies.
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arxiv:2502.08599
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we propose a spin foam model of four - dimensional quantum gravity which is based on the integration of the tetrads in the path integral for the palatini action of general relativity. in the euclidian gravity case we show that the model can be understood as a modification of the barrett - crane spin foam model. fermionic matter can be coupled by using the path integral with sources for the tetrads and the spin connection, and the corresponding state sum is based on a spin foam where both the edges and the faces are colored independently with the irreducible representations of the spacetime rotations group.
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arxiv:gr-qc/0504131
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the task of aesthetic quality assessment is complicated due to its subjectivity. in recent years, the target representation of image aesthetic quality has changed from a one - dimensional binary classification label or numerical score to a multi - dimensional score distribution. according to current methods, the ground truth score distributions are straightforwardly regressed. however, the subjectivity of aesthetics is not taken into account, that is to say, the psychological processes of human beings are not taken into consideration, which limits the performance of the task. in this paper, we propose a deep drift - diffusion ( ddd ) model inspired by psychologists to predict aesthetic score distribution from images. the ddd model can describe the psychological process of aesthetic perception instead of traditional modeling of the results of assessment. we use deep convolution neural networks to regress the parameters of the drift - diffusion model. the experimental results in large scale aesthetic image datasets reveal that our novel ddd model is simple but efficient, which outperforms the state - of - the - art methods in aesthetic score distribution prediction. besides, different psychological processes can also be predicted by our model.
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arxiv:2010.07661
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the traditional method for detecting extra - solar planets relies on measuring a small stellar wobble which is assumed to be caused by a planet orbiting the star. recently, it was suggested that a similar stellar wobble could be caused by a close binary system ( schneider and cabrera, 2006 ). here we show that, although the effect of a close binary system can at first sight be mistaken as a planetary companion to the star, more careful analysis of the observational data should allow us to distinguish between the two effects.
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arxiv:0810.0506
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superconducting qubits in today ' s quantum processing units are typically fabricated with angle - evaporated aluminum - - aluminum - oxide - - aluminum josephson junctions. however, there is an urgent need to overcome the limited reproducibility of this approach when scaling up the number of qubits and junctions. fabrication methods based on subtractive patterning of superconductor - - insulator - - superconductor trilayers, used for more classical large - scale josephson junction circuits, could provide the solution but they in turn often suffer from lossy dielectrics incompatible with high qubit coherence. in this work, we utilize native aluminum oxide as a sidewall passivation layer for junctions based on aluminum - - aluminum - oxide - - niobium trilayers, and use such junctions in qubits. we design the fabrication process such that the few - nanometer - thin native oxide is not exposed to oxide removal steps that could increase its defect density or hinder its ability to prevent shorting between the leads of the junction. with these junctions, we design and fabricate transmon - like qubits and measure time - averaged coherence times up to 30 $ \ mu $ s at a qubit frequency of 5 ghz, corresponding to a qubit quality factor of one million. our process uses subtractive patterning and optical lithography on wafer scale, enabling high throughput in patterning. this approach provides a scalable path toward fabrication of superconducting qubits on industry - standard platforms.
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arxiv:2504.03481
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existing technologies for distributed light - field mapping and light pollution monitoring ( lpm ) rely on either remote satellite imagery or manual light surveying with single - point sensors such as sqms ( sky quality meters ). these modalities offer low - resolution data that are not informative for dense light - field mapping, pollutant factor identification, or sustainable policy implementation. in this work, we propose lightviz - - an interactive software interface to survey, simulate, and visualize light pollution maps in real - time. as opposed to manual error - prone methods, lightviz ( i ) automates the light - field data collection and mapping processes ; ( ii ) provides a platform to simulate various light sources and intensity attenuation models ; and ( iii ) facilitates effective policy identification for conservation. to validate the end - to - end computational pipeline, we design a distributed light - field sensor suit, collect data on florida coasts, and visualize the distributed light - field maps. in particular, we perform a case study at st. johns county in florida, which has a two - decade conservation program for lighting ordinances. the experimental results demonstrate that lightviz can offer high - resolution light - field mapping and provide interactive features to simulate and formulate community policies for light pollution mitigation. we also propose a mathematical formulation for light footprint evaluation, which we integrated into lightviz for targeted lpm in vulnerable communities. a test - case of the lightviz software release is available at : https : / / github. com / uf - robopi / lightviz.
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arxiv:2408.00808
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measured foliations at infinity of quasi - fuchsian manifolds are a natural analog at infinity to the measured bending laminations on the boundary of its convex core. we show that given a pair of arational measured foliations $ ( \ mathsf { f } _ { + }, \ mathsf { f } _ { - } ) $ which fill a closed hyperbolic surface $ s $, for $ t > 0 $ sufficiently small, $ t \ mathsf { f } _ { + } $ and $ t \ mathsf { f } _ { - } $ can be uniquely realised as the measured foliations at infinity of a quasi - fuchsian manifold homeomorphic to $ s \ times \ mathbb { r } $, which is sufficiently close to the fuchsian locus. here arationality means that the corresponding measured laminations are maximal. the proof is inspired by bonahon ' s in \ cite { bonahon05 } which shows that a quasi - fuchsian manifold close to the fuchsian locus can be uniquely determined by the data of filling measured bending laminations on the boundary of its convex core. we also interpret the result in half - pipe geometry
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arxiv:2111.01614
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the trojan - horse method is an indirect approach to determine the energy dependence of s factors of astrophysically relevant two - body reactions. this is accomplished by studying closely related three - body reactions under quasi - free scattering conditions. the basic theory of the trojan - horse method is developed starting from a post - form distorted wave born approximation of the t - matrix element. in the surface approximation the cross section of the three - body reaction can be related to the s - matrix elements of the two - body reaction. the essential feature of the trojan - horse method is the effective suppression of the coulomb barrier at low energies for the astrophysical reaction leading to finite cross sections at the threshold of the two - body reaction. in a modified plane wave approximation the relation between the two - body and three - body cross sections becomes very transparent. applications of the trojan horse method are discussed. it is of special interest that electron screening corrections are negligible due to the high projectile energy.
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arxiv:nucl-th/0401054
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we report the result of our { \ it ab initio } calculation of the $ 6s ^ 2s _ { 1 / 2 } \ to 5d ^ 2d _ { 3 / 2 } $ parity nonconserving electric dipole transition amplitude in $ ^ { 137 } \ text { ba } ^ + $ based on relativistic coupled - cluster theory. considering single, double and partial triple excitations, we have achieved an accuracy of less than one percent. if the accuracy of our calculation can be matched by the proposed parity nonconservation experiment in ba $ ^ + $ for the above transition, then the combination of the two results would provide an independent non accelerator test of the standard model of particle physics.
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arxiv:physics/0509130
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we construct five dimensional black rings in global anti - de sitter space using numerical methods. these rings satisfy the bps bound $ | j | < m \ ell $, but the angular velocity always violates the hawking - reall bound $ | \ omega _ h \ ell | \ leq 1 $, indicating that they should be unstable under superradiance. at high temperatures, the limit $ | \ omega _ h \ ell | \ searrow 1 $ is attained by thin rings with an arbitrarily large radius. however, at sufficiently low temperatures, this limit is saturated by a new kind of rings, whose outer circle can still be arbitrarily long while the hole in the middle does not grow proportionally. this gives rise to a membrane - like horizon geometry, which does not have an asymptotically flat counterpart. we find no evidence for thin ads black rings whose transverse $ s ^ 2 $ is much larger than the radius of ads, $ \ ell $, and thus these solutions never fall into the hydrodynamic regime of the dual cft. thermodynamically, we find that ads black rings never dominate the grand canonical ensemble. the behaviour of our solutions in the microcanonical ensemble approaches known perturbative results in the thin - ring limit.
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arxiv:1412.5680
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' bare ' active galactic nuclei ( agn ) are a subclass of type 1 agn that show little or no intrinsic absorption. they offer an unobscured view of the central regions of the agn and therefore serve as ideal targets to study the relativistic reflection features originating from the innermost regions of the accretion disc. we present a detailed broadband spectral analysis ( $ 0. 3 - 70 $ kev ) of one of the most luminous bare agn in the local universe, rbs 1124 ( $ z = 0. 208 $ ) using a new, co - ordinated high signal - to - noise observation obtained by $ \ textit { xmm - newton } $ and $ \ textit { nustar } $. the source exhibits a power - law continuum with $ \ gamma \ sim $ 1. 8 along with a soft excess below 2 kev, a weak neutral iron line and curvature at high energies ( $ \ sim 30 $ kev ). the broadband spectrum, including the soft excess and the high - energy continuum, is well fit by the relativistic reflection model when the accretion disc is allowed to have densities of log $ ( n _ { \ rm e } $ / cm $ ^ { - 3 } $ ) $ \ gtrsim 19. 2 $. our analysis therefore suggests that when high - density effects are considered, relativistic reflection remains a viable explanation for the soft excess.
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arxiv:2409.01395
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the integration of tabular data from diverse sources is often hindered by inconsistencies in formatting and representation, posing significant challenges for data analysts and personal digital assistants. existing methods for automating tabular data transformations are limited in scope, often focusing on specific types of transformations or lacking interpretability. in this paper, we introduce tabulax, a novel framework that leverages large language models ( llms ) for multi - class tabular transformations. tabulax first classifies input tables into four transformation classes ( string - based, numerical, algorithmic, and general ) and then applies tailored methods to generate human - interpretable transformation functions, such as numeric formulas or programming code. this approach enhances transparency and allows users to understand and modify the mappings. through extensive experiments on real - world datasets from various domains, we demonstrate that tabulax outperforms existing state - of - the - art approaches in terms of accuracy, supports a broader class of transformations, and generates interpretable transformations that can be efficiently applied.
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arxiv:2411.17110
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the mond modified gravity paradigm, best known for its agreement with galactic rotation curve data, is difficult to devise laboratory tests for. mond ' s predictions differ substantially from newtonian gravity only in the case of very small accelerations ( $ a < a _ 0 = 1. 2 \ times10 ^ { - 10 } ~ \ mathrm { m / s } ^ 2 = 3. 8 ~ \ mathrm { mm / s / y } $ ). in the solar system, radio and laser measurements of test bodies do permit acceleration measurements this precise ; however, in at least some viable realizations, mond has an " external field effect " ( efe ) which essentially disables the mond effects in the presence of the inner milky way ' s background gravitational field, invalidating solar system limits. can we do any measurement with solar - system - like acceleration precision, but on a system many kiloparsecs away that avoids the efe? in this paper, we show that mond ' s non - $ 1 / r ^ 2 $ gravitational acceleration has a unique and hard - to - fake effect : in contrast to the non - precessing elliptical orbits predicted by two - body newtonian gravity, in the presence of mond we expect apsidal precession in two - body systems. an extreme precision apsidal precession detection opportunity is available for eclipsing binaries, where, for some viewing geometries, apsidal precession causes transit time variations ( ttvs ) and transit duration variations ( tdvs ). if appropriate binaries can be found and measured, the presence or absence of timing variations may provide a definitive " solar - system - like " test of many efe - bearing mond theories like qumond.
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arxiv:2410.01513
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) $ are integral, in the sense that the actions have coefficients in the ring of cyclotomic integers $ \ mathbb { z } [ \ zeta ] $, when expressed in these bases.
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arxiv:2212.10940
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low - dimensional periodic arrays of scatterers with a moving point particle are ideal models for studying deterministic diffusion. for such systems the diffusion coefficient is typically an irregular function under variation of a control parameter. here we propose a systematic scheme of how to approximate deterministic diffusion coefficients of this kind in terms of correlated random walks. we apply this approach to two simple examples which are a one - dimensional map on the line and the periodic lorentz gas. starting from suitable green - kubo formulas we evaluate hierarchies of approximations for their parameter - dependent diffusion coefficients. these approximations converge exactly yielding a straightforward interpretation of the structure of these irregular diffusion coeficients in terms of dynamical correlations.
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arxiv:nlin/0202040
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we propose a new conditional bekk matrix - f ( cbf ) model for the time - varying realized covariance ( rcov ) matrices. this cbf model is capable of capturing heavy - tailed rcov, which is an important stylized fact but could not be handled adequately by the wishart - based models. to further mimic the long memory feature of the rcov, a special cbf model with the conditional heterogeneous autoregressive ( har ) structure is introduced. moreover, we give a systematical study on the probabilistic properties and statistical inferences of the cbf model, including exploring its stationarity, establishing the asymptotics of its maximum likelihood estimator, and giving some new inner - product - based tests for its model checking. in order to handle a large dimensional rcov matrix, we construct two reduced cbf models - - the variance - target cbf model ( for moderate but fixed dimensional rcov matrix ) and the factor cbf model ( for high dimensional rcov matrix ). for both reduced models, the asymptotic theory of the estimated parameters is derived. the importance of our entire methodology is illustrated by simulation results and two real examples.
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arxiv:1903.12077
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despite being responsible for state - of - the - art results in several computer vision and natural language processing tasks, neural networks have faced harsh criticism due to some of their current shortcomings. one of them is that neural networks are correlation machines prone to model biases within the data instead of focusing on actual useful causal relationships. this problem is particularly serious in application domains affected by aspects such as race, gender, and age. to prevent models from incurring on unfair decision - making, the ai community has concentrated efforts in correcting algorithmic biases, giving rise to the research area now widely known as fairness in ai. in this survey paper, we provide an in - depth overview of the main debiasing methods for fairness - aware neural networks in the context of vision and language research. we propose a novel taxonomy to better organize the literature on debiasing methods for fairness, and we discuss the current challenges, trends, and important future work directions for the interested researcher and practitioner.
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arxiv:2211.05617
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score - based models, trained with denoising score matching, are remarkably effective in generating high dimensional data. however, the high variance of their training objective hinders optimisation. we attempt to reduce it with a control variate, derived via a $ k $ - th order taylor expansion on the training objective and its gradient. we prove an equivalence between the two and demonstrate empirically the effectiveness of our approach on a low dimensional problem setting ; and study its effect on larger problems.
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arxiv:2408.12270
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speaker modeling is essential for many related tasks, such as speaker recognition and speaker diarization. the dominant modeling approach is fixed - dimensional vector representation, i. e., speaker embedding. this paper introduces a research and production oriented speaker embedding learning toolkit, wespeaker. wespeaker contains the implementation of scalable data management, state - of - the - art speaker embedding models, loss functions, and scoring back - ends, with highly competitive results achieved by structured recipes which were adopted in the winning systems in several speaker verification challenges. the application to other downstream tasks such as speaker diarization is also exhibited in the related recipe. moreover, cpu - and gpu - compatible deployment codes are integrated for production - oriented development. the toolkit is publicly available at https : / / github. com / wenet - e2e / wespeaker.
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arxiv:2210.17016
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detachment, an important mechanism for reducing target heat deposition, is achieved through reductions in power, particle and momentum ; which are induced through plasma - atom and plasma - molecule interactions. experimental research in how those reactions precisely contribute to detachment is limited. in this work, we investigate a new spectroscopic technique to utilise hydrogen balmer line measurements to 1 ) disentangle the balmer line emission from the various plasma - atom and plasma - molecule interactions ; and 2 ) quantify their contributions to ionisation, recombination and radiative power losses. during detachment, the observed $ h \ alpha $ emission often strongly increases, which could be an indicator for plasma - molecule interactions involving $ h _ 2 ^ + $ and / or $ h ^ - $. our analysis technique quantifies the $ h \ alpha $ emission due to plasma - molecule interactions and uses this to 1 ) quantify the balmer line emission contribution due to $ h _ 2 ^ + $ and / or $ h ^ - $ ; 2 ) subsequently estimate its resulting particle sinks / sources and radiative power losses. its performance is verified using synthetic diagnostic techniques of both detached tcv and mast - u solps - iter simulations. experimental results of this technique on tcv data show a bifurcation occurs between the measured total $ h \ alpha $ and the atomic estimate of $ h \ alpha $ emission, indicative of the presence of additional $ h \ alpha $ due to plasma - molecule interactions with $ h _ 2 ^ + $ ( and / or $ h ^ - $ ). an example analysis shows that the hydrogenic line series, even $ ly \ alpha $ as well as the medium - n balmer lines can be significantly influenced by plasma - molecule interactions by tens of percent during which significant molecular activated recombination ( mar ) is expected.
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arxiv:2008.00288
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the determination of the stiffness center of a machine tool is a major element for knowing the dynamic behavior of this one. this stiffness center can be obtained from a static characterization of the machine tool. for an operation of turning, we present an experimental protocol to determine the stiffness matrix, then by inversion, the associated flexibility matrix. this step makes it possible to establish the privileged directions of the movement associated with the maximum and minimal stiffness as well as the stiffness center. through this step, it is observed that, at the time of an operation of turning, the movement of the point of the tool is carried out according to an ellipse located in a tilted average plan compared to the machine spindle. this movement is linked with the self - excited vibrations. this analysis could be exploited and transposed in the case of the high speed machining. it will make it possible to predict various aspects of machining related to the behavior of the tool in the process of cut.
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arxiv:0908.1373
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the habitable zone ( hz ) is commonly defined as the range of distances from a host star within which liquid water, a key requirement for life, may exist on a planet ' s surface. substantially more co2 than present in earth ' s modern atmosphere is required to maintain clement temperatures for most of the hz, with several bars required at the outer edge. however, most complex aerobic life on earth is limited by co2 concentrations of just fractions of a bar. at the same time, most exoplanets in the traditional hz reside in proximity to m dwarfs, which are more numerous than sun - like g dwarfs but are predicted to promote greater abundances of gases that can be toxic in the atmospheres of orbiting planets, such as carbon monoxide ( co ). here we show that the hz for complex aerobic life is likely limited relative to that for microbial life. we use a 1d radiative - convective climate and photochemical models to circumscribe a habitable zone for complex life ( hzcl ) based on known toxicity limits for a range of organisms as a proof of concept. we find that for co2 tolerances of 0. 01, 0. 1, and 1 bar, the hzcl is only 21 %, 32 %, and 50 % as wide as the conventional hz for a sun - like star, and that co concentrations may limit some complex life throughout the entire hz of the coolest m dwarfs. these results cast new light on the likely distribution of complex life in the universe and have important ramifications for the search for exoplanet biosignatures and technosignatures.
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arxiv:1902.04720
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there had been well known claims of ` ` provably unbreakable ' ' quantum protocols for bit commitment and coin tossing. however, we, and independently mayers, showed that all proposed quantum bit commitment ( and therefore coin tossing ) schemes are, in principle, insecure because the sender, alice, can always cheat successfully by using an epr - type of attack and delaying her measurements. one might wonder if secure quantum bit commitment and coin tossing protocols exist at all. here we prove that an epr - type of attack by alice will, in principle, break { \ em any } realistic quantum bit commitment and { \ em ideal } coin tossing scheme. therefore, provided that alice has a quantum computer and is capable of storing quantum signals for an arbitrary length of time, all those schemes are insecure. since bit commitment and coin tossing are useful primitives for building up more sophisticated protocols such as zero - knowledge proofs, our results cast very serious doubt on the security of quantum cryptography in the so - called ` ` post - cold - war ' ' applications.
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arxiv:quant-ph/9605026
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in this paper we formulate the least action principle for an organized system as the minimum of the total sum of the actions of all of the elements. this allows us to see how this most basic law of physics determines the development of the system towards states with less action - organized states. also we state that the metric tensor can describe the specific state of the constraints of the system, which is its actual organization. with this the organization is defined in two ways : 1. a quantitative : the action i. 2. a qualitative : the metric tensor. these two measures can describe the level of development and the specifics of the organization of a system. we consider closed and open systems.
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arxiv:1004.3518
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we consider the geodesic flow of a compact connected rank 1 surface. we prove a formula for the topological pressure as the exponential growth rate of rank 1 periodic geodesics generalizing a previous result of k. gelfert and b. schapira [ 12 ].
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arxiv:1606.07771
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phase stability and properties of two - dimensional phosphorus carbide, p $ _ x $ c $ _ { 1 - x } $, are investigated using the first - principles method in combination with cluster expansion and monte carlo simulation. monolayer p $ _ x $ c $ _ { 1 - x } $ is found to be a phase separating system which indicates difficulty in fabricating monolayer p $ _ x $ c $ _ { 1 - x } $ or crystalline p $ _ x $ c $ _ { 1 - x } $ thin films. nevertheless, a bottom - up design approach is used to determine the stable structures of p $ _ x $ c $ _ { 1 - x } $ of various compositions which turn out to be superlattices consisting of alternating carbon and phosphorus nanoribbons along the armchair direction. results of first - principles calculations indicate that once these structures are produced, they are mechanically and thermodynamically stable. all the ordered structures are predicted to be semiconductors, with band gap ranging from 0. 2 to 1. 2 ev. in addition, the monolayer p $ _ x $ c $ _ { 1 - x } $ are predicted to have high carrier mobility, and high optical absorption in the ultraviolet region which shows a red - shift as the p : c ratio increases. these properties make 2d p $ _ x $ c $ _ { 1 - x } $ promising materials for applications in electronics and optoelectronics.
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arxiv:2010.08700
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high - order implicit shock tracking ( fitting ) is a class of high - order, optimization - based numerical methods to approximate solutions of conservation laws with non - smooth features by aligning elements of the computational mesh with non - smooth features. this ensures the non - smooth features are perfectly represented by inter - element jumps and high - order basis functions approximate smooth regions of the solution without nonlinear stabilization, which leads to accurate approximations on traditionally coarse meshes. in this work, we extend implicit shock tracking to time - dependent problems using a slab - based space - time approach. this is achieved by reformulating a time - dependent conservation law as a steady conservation law in one higher dimension and applying existing implicit shock tracking techniques. to avoid computations over the entire time domain and unstructured mesh generation in higher dimensions, we introduce a general procedure to generate conforming, simplex - only meshes of space - time slabs in such a way that preserves features ( e. g., curved elements, refinement regions ) from previous time slabs. the use of space - time slabs also simplifies the shock tracking problem by reducing temporal complexity. several practical adaptations of the implicit shock tracking solvers are developed for the space - time setting including 1 ) a self - adjusting temporal boundary, 2 ) nondimensionalization of a space - time slab, 3 ) adaptive mesh refinement, and 4 ) shock boundary conditions, which lead to accurate solutions on coarse space - time grids, even for problem with complex flow features such as curved shocks, shock formation, shock - shock and shock - boundary interaction, and triple points.
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arxiv:2308.04065
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configuration knobs of database systems are essential to achieve high throughput and low latency. recently, automatic tuning systems using machine learning methods ( ml ) have shown to find better configurations compared to experienced database administrators ( dbas ). however, there are still gaps to apply the existing systems in production environments, especially in the cloud. first, they conduct tuning for a given workload within a limited time window and ignore the dynamicity of workloads and data. second, they rely on a copied instance and do not consider the availability of the database when sampling configurations, making the tuning expensive, delayed, and unsafe. to fill these gaps, we propose onlinetune, which tunes the online databases safely in changing cloud environments. to accommodate the dynamicity, onlinetune embeds the environmental factors as context feature and adopts contextual bayesian optimization with context space partition to optimize the database adaptively and scalably. to pursue safety during tuning, we leverage the black - box and the white - box knowledge to evaluate the safety of configurations and propose a safe exploration strategy via subspace adaptation. %, greatly decreasing the risks of applying bad configurations. we conduct evaluations on dynamic workloads from benchmarks and real - world workloads. compared with the state - of - the - art methods, onlinetune achieves 14. 4 % ~ 165. 3 % improvement on cumulative performance while reducing 91. 0 % ~ 99. 5 % unsafe configuration recommendations.
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arxiv:2203.14473
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in this article, we consider the problem of determining formulas for the number of representations of a natural number $ n $ by a sum of figurate numbers with certain positive integer coefficients. to achieve this, we prove that the associated generating function gives rise to a modular form of integral weight under certain condition on the coefficients when even number of higher figurate numbers are considered. in particular, we obtain modular property of the generating function corresponding to a sum of even number of triangular numbers with coefficients. we also obtain modularity property of the generating function of mixed forms involving figurate numbers ( including the squares and triangular numbers ) with coefficients and forms of the type $ m ^ 2 + mn + n ^ 2 $ with coefficients. in particular, we show the modularity of the generating function of odd number of squares and odd number of triangular numbers ( with coefficients ). as a consequence, explicit formulas for the number of representations of these mixed forms are obtained using a basis of the corresponding space of modular forms of integral weight. we also obtain several applications concerning the triangular numbers with coefficients similar to the ones obtained in \ cite { ono }. in \ cite { xia }, xia - ma - tian considered some special cases of mixed forms and obtained the number of representations of these 21 mixed forms using the $ ( p, k ) $ parametrisation method. we also derive these 21 formulas using our method and further obtain as a consequence, the $ ( p, k ) $ parametrisation of the eisenstein series $ e _ 4 ( \ tau ) $ and its duplications. it is to be noted that the $ ( p, k ) $ parametrisation of $ e _ 4 $ and its duplications were derived by a different method in \ cite { { aw }, { aaw } }. we illustrate our method with several examples.
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arxiv:2302.00964
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thomas has recently derived scaling laws for x - ray radiation from electrons accelerated in plasma bubbles, as well as a threshold for the self - injection of background electrons into the bubble [ a. g. r. thomas, phys. plasmas 17, 056708 ( 2010 ) ]. to obtain this threshold, the equations of motion for a test electron are studied within the frame of the bubble model, where the bubble is described by prescribed electromagnetic fields and has a perfectly spherical shape. the author affirms that any elliptical trajectory of the form x ' ^ 2 / { \ gamma } _ p ^ 2 + y ' ^ 2 = r ^ 2 is solution of the equations of motion ( in the bubble frame ), within the approximation p ' _ y ^ 2 / p ' _ x ^ 2 \ ll 1. in addition, he highlights that his result is different from the work of kostyukov et al. [ phys. rev. lett. 103, 175003 ( 2009 ) ], and explains the error committed by kostyukov - nerush - pukhov - seredov ( knps ). in this comment, we show that numerically integrated trajectories, based on the same equations than the analytical work of thomas, lead to a completely different result for the self - injection threshold, the result published by knps [ phys. rev. lett. 103, 175003 ( 2009 ) ]. we explain why the analytical analysis of thomas fails and we provide a discussion based on numerical simulations which show exactly where the difference arises. we also show that the arguments of thomas concerning the error of knps do not hold, and that their analysis is mathematically correct. finally, we emphasize that if the knps threshold is found not to be verified in pic ( particle in cell ) simulations or experiments, it is due to a deficiency of the model itself, and not to an error in the mathematical derivation.
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arxiv:1104.2449
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in this paper we consider the problem of finding a vector that can be written as a nonnegative integer linear combination of given 0 - 1 vectors, the generators, such that the l _ 1 - distance between this vector and a given target vector is minimized. we prove that this closest vector problem is np - hard to approximate within a o ( d ) additive error, where d is the dimension of the ambient vector space. we show that the problem can be approximated within a o ( d ^ { 3 / 2 } ) additive error in polynomial time, by rounding an optimal solution of a natural lp relaxation for the problem. we also observe that in the particular case where the target vector is integer and the generators form a totally unimodular matrix, the problem can be solved in polynomial time. the closest vector problem arises in the elaboration of radiation therapy plans. in this context, the target is a nonnegative integer matrix and the generators are certain 0 - 1 matrices whose rows satisfy the consecutive ones property. here we mainly consider the version of the problem in which the set of generators comprises all those matrices that have on each nonzero row a number of ones that is at least a certain constant. this set of generators encodes the so - called minimum separation constraint.
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arxiv:0907.0138
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we present a new observable, position - dependent power spectrum, to measure the large - scale structure bispectrum in the squeezed configuration, where one wavenumber is much smaller than the other two. the squeezed - limit bispectrum measures how the small - scale power spectrum is modulated by a long - wavelength overdensity, which is due to gravitational evolution and possibly inflationary physics. we divide a survey into small subvolumes, compute the local power spectrum and the mean overdensity in each subvolume, and measure the correlation between them. the correlation measures the integral of the bispectrum, which is dominated by squeezed configurations if the scale of the local power spectrum is much smaller than the subvolume size. we use the separate universe approach to model how the small - scale power spectrum is affected by a long - wavelength overdensity gravitationally. this models the nonlinearity of the bispectrum better than the perturbation theory approach. not only the new observable is easy to interpret, but it sidesteps the complexity of the full bispectrum estimation as both power spectrum and mean overdensity are easier to estimate than the full bispectrum. we report on the first measurement of the position - dependent correlation function from the sdss - iii boss dr10 cmass sample. we detect the bispectrum of the cmass sample, and constrain their nonlinear bias combining with anisotropic clustering and weak lensing. we finally study the response of the small - scale power spectrum to 1 - 3 long - wavelength overdensities. we compare the separate universe approach to separate universe simulations to unprecedented accuracy. we test the standard perturbation theory ( spt ) hypothesis that the nonlinear n - point function is fully predicted by the linear power spectrum at the same time. we find discrepancies on small scales, which suggest that spt fails even if it is calculated to all orders.
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arxiv:1508.03256
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this is a reply to w. zawadzki ' s paper ( arxiv : cond - mat / 0701378 ) on non - exietence of spin transverse force for a relativistic electron. the force was first proposed by the present author that the spin current will experience a transverse force in an electric field as a relativistic quantum mechanical effect, and in semiconductor with rahsba spin - orbit coupling. zawadzki ' s approach is based on an incorrect relation between the velocity and canonical momentum, and his conclusion is not true.
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arxiv:cond-mat/0701700
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we present multiplicity results for mass constrained allen - cahn equations on a riemannian manifold with boundary, considering both neumann and dirichlet conditions. these results hold under the assumptions of small mass constraint and small diffusion parameter. we obtain lower bounds on the number of solutions according to the lusternik - - schnirelmann category of the manifold in case of dirichlet boundary conditions and of its boundary in the case of neumann boundary conditions. under generic non - degeneracy assumptions on the solutions, we obtain stronger results based on morse inequalities. our approach combines topological and variational methods with tools from geometric measure theory.
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arxiv:2401.17847
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the accurate prediction of patient prognosis is a critical challenge in clinical practice. with the availability of various patient information, physicians can optimize medical care by closely monitoring disease progression and therapy responses. to enable better individualized treatment, dynamic prediction models are required to continuously update survival probability predictions as new information becomes available. this article aims to offer a comprehensive survey of current methods in dynamic survival analysis, encompassing both classical statistical approaches and deep learning techniques. additionally, it will also discuss the limitations of existing methods and the prospects for future advancements in this field.
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arxiv:2311.15743
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not get new human spaceflight ability, the us risked become a second or third - rate space power. as early as the reagan administration, there had been calls for nasa to expand private sector involvement in space exploration rather than do it all in - house. in the 1990s, nasa and lockheed martin entered into an agreement to develop the lockheed martin x - 33 demonstrator of the venturestar spaceplane, which was intended to replace the space shuttle. due to technical challenges, the spacecraft was cancelled in 2001. despite this, it was the first time a commercial space company directly expended a significant amount of its resources into spacecraft development. the advent of space tourism also forced nasa to challenge its assumption that only governments would have people in space. the first space tourist was dennis tito, an american investment manager and former aerospace engineer who contracted with the russians to fly to the international space station for four days, despite the opposition of nasa to the idea. advocates of this new commercial approach for nasa included former astronaut buzz aldrin, who remarked that it would return nasa to its roots as a research and development agency, with commercial entities actually operating the space systems. having corporations take over orbital operations would also allow nasa to focus all its efforts on deep space exploration and returning humans to the moon and going to mars. embracing this approach, nasa ' s commercial crew program started by contracting cargo delivery to the international space station and flew its first operational contracted mission on spacex crew - 1. this marked the first time since the retirement of the space shuttle that nasa was able to launch its own astronauts on an american spacecraft from the united states, ending a decade of reliance on the russians. in 2019, nasa announced the artemis program, intending to return to the moon and establish a permanent human presence. this was paired with the artemis accords with partner nations to establish rules of behavior and norms of space commercialization on the moon. in 2023, nasa established the moon to mars program office. the office is designed to oversee the various projects, mission architectures and associated timelines relevant to lunar and mars exploration and science. = = active programs = = = = = human spaceflight = = = = = = = international space station ( 1993 – present ) = = = = the international space station ( iss ) combines nasa ' s space station freedom project with the russian mir - 2 station, the european columbus station, and the japanese kibo laboratory module. nasa originally planned in the 1980s to develop freedom alone, but us budget constraints led to the merger of these projects into
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https://en.wikipedia.org/wiki/NASA
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we construct conservative analytic flows of zero metric entropy which satisfy the classical central limit theorem.
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arxiv:2210.10121
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location of non - stationary forced oscillation ( fo ) sources can be a challenging task, especially in cases under resonance condition with natural system modes, where the magnitudes of the oscillations could be greater in places far from the source. therefore, it is of interest to construct a global time - frequency ( tf ) representation ( tfr ) of the system, which can capture the oscillatory components present in the system. in this paper we develop a systematic methodology for frequency identification and component filtering of non - stationary power system forced oscillations ( fo ) based on multi - channel tfr. the frequencies of the oscillatory components are identified on the tf plane by applying a modified ridge estimation algorithm. then, filtering of the components is carried out on the tf plane applying the anti - transform functions over the individual tfrs around the identified ridges. this step constitutes an initial stage for the application of the dissipating energy flow ( def ) method used to locate fo sources. besides, we compare three tf approaches : short - time fourier transform ( stft ), stft - based synchrosqueezing transform ( fsst ) and second order fsst ( fsst2 ). simulated signals and signals from real operation are used to show that the proposed method provides a systematic framework for identification and filtering of power systems non - stationary forced oscillations.
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arxiv:2108.08736
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due to the recent advances of natural language processing, several works have applied the pre - trained masked language model ( mlm ) of bert to the post - correction of speech recognition. however, existing pre - trained models only consider the semantic correction while the phonetic features of words is neglected. the semantic - only post - correction will consequently decrease the performance since homophonic errors are fairly common in chinese asr. in this paper, we proposed a novel approach to collectively exploit the contextualized representation and the phonetic information between the error and its replacing candidates to alleviate the error rate of chinese asr. our experiment results on real world speech recognition datasets showed that our proposed method has evidently lower cer than the baseline model, which utilized a pre - trained bert mlm as the corrector.
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arxiv:2111.08400
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hybrid quantum systems made of cold atoms near nanostructured surfaces are expected to open up new opportunities for the construction of quantum sensors and for quantum information. for the design of such tailored quantum systems the interaction of alkali atoms with dielectric and metallic surfaces is crucial and required to be understood in detail. here, we present real - time measurements of the adsorption and desorption of rubidium atoms on gold nanofilms. surface plasmon polaritons ( spp ) are excited at the gold surface and detected in a phase sensitive way. from the temporal change of the spp phase the rubidium coverage of the gold film is deduced with a sensitivity of better than 0. 3 % of a monolayer. by comparing the experimental data with a langmuir type adsorption model we obtain the thermal desorption rate and the sticking probability. in addition, also laser - induced desorption is observed and quantified.
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arxiv:1006.2946
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