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generalized parton distributions of the pion are evaluated in chiral quark models with the help of double distributions. as a result the polynomiality conditions are automatically satisfied. in addition, positivity constraints, proper normalization and support, sum rules, and soft pion theorems are fulfilled. we obtain explicit expressions holding at the low - energy quark - model scale, which exhibit no factorization in the t - dependence. the crucial qcd evolution of the quark - model distributions is carried out up to experimental or lattice scales. the obtained results for the parton distribution function and the parton distribution amplitude describe the available experimental and lattice data, confirming that the quark - model scale is low, around 320 mev.
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arxiv:0804.0718
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we study the effect of communication delays on distributed consensus algorithms. two ways to model delays on a network are presented. the first model assumes that each link delivers messages with a fixed ( constant ) amount of delay, and the second model is more realistic, allowing for i. i. d. time - varying bounded delays. in contrast to previous work studying the effects of delays on consensus algorithms, the models studied here allow for a node to receive multiple messages from the same neighbor in one iteration. the analysis of the fixed delay model shows that convergence to a consensus is guaranteed and the rate of convergence is reduced by no more than a factor o ( b ^ 2 ) where b is the maximum delay on any link. for the time - varying delay model we also give a convergence proof which, for row - stochastic consensus protocols, is not a trivial consequence of ergodic matrix products. in both delay models, the consensus value is no longer the average, even if the original protocol was an averaging protocol. for this reason, we propose the use of a different consensus algorithm called push - sum [ kempe et al. 2003 ]. we model delays in the push - sum framework and show that convergence to the average consensus is guaranteed. this suggests that push - sum might be a better choice from a practical standpoint.
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arxiv:1207.5839
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we derive simple - to - evaluate, closed - form solutions to the inhomogeneous helmholtz equation, $ \ delta u + k ^ 2 u = \ chi _ { b _ { x _ 0, r } } $, the schr \ " odinger equation, $ i \ hbar \ partial _ t u + \ frac { \ hbar ^ 2 } { 2m } \ delta u = 0 $ with initial data $ { u ( x, 0 ) = \ chi _ { b _ { x _ 0, r } } } $, and the cauchy problem for the linear wave equation, $ { \ partial _ t ^ 2 u - c ^ 2 \ delta u = 0 } $ with initial data $ \ left ( u ( x, 0 ), \ partial _ t u ( x, 0 ) \ right ) = \ left ( \ chi _ { b _ { x _ 0, r } }, \ chi _ { b _ { x _ 0, r } } \ right ). $ the function $ \ chi _ { b _ { x _ 0, r } } $ is the characteristic function on the ball $ b _ { x _ 0, r } = \ { x \ in \ mathbf { r } ^ 3 : | x _ 0 - x | \ leq r \ } $. furthermore, we use these solutions to construct explicit approximate solutions when the data are radial functions on $ b _ { x _ 0, r } $, and give various error estimates on these approximations.
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arxiv:2108.08108
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in the present work, we study the dynamics of a magnetic nanoparticle coupled through the magnetoelectric coupling to the ferroelectric crystal. the model of our interest is nonlinear, and we explore the problem under different limits of weak and strong linearity. by applying two electric fields with different frequencies, we control the form of the confinement potential of the ferroelectric subsystem and realize different types of dynamics. we proved that the system is more sensitive to magnetoelectric coupling in the case of double - well potential. in particular, in the case of strong nonlinearity, arbitrary small values of magnetoelectric coupling lead to chaotic dynamics. in essence, magnetoelectric coupling plays a role akin to the small perturbations destroying invariant tors according to the kam theorem. we showed that bifurcations in the system are of hopf ' s type. we observed the formation of magnetoelectric fractals in the system. in the limit of weak nonlinearity, we studied a problem of parametric nonlinear resonance and enhancement of magnetic oscillations through magnetoelectric coupling.
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arxiv:2306.13110
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\ chi _ r - \ chi _ l + \ pi $. in such a case, the current - phase relation is similar to that in a s / $ f _ l $ - f - $ f _ r $ / s junction.
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arxiv:2210.12718
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we examine the neutralino dark matter phenomenology in supersymmetric scenarios with nonuniversal higgs masses at the gauge coupling unification scale that can acommodate a light higgs boson, where the correct relic density is obtained mostly through the annihilation into a pseudoscalar a. our analysis shows that most part of the a pole region can produce detectable gamma - ray and antiproton signals. we further focus on uncertainties influencing the results in indirect and mainly direct detection.
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arxiv:1107.0792
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the magellanic stream ( ms ) has long been known to contain multiple h i strands and corresponding stellar populations are beginning to be discovered. combining a sample of 17 stars from the h3 ( " hectochelle in the halo at high resolution " ) survey with 891 stars drawn from the gaia dr3 catalog, we trace stars along a sub - dominant strand of the ms, as defined by gas content, across 30 $ ^ \ circ $ on the sky. we find that the corresponding dominant strand at the similar position along the ms is devoid of stars with galactocentric distance $ \ lesssim 55 $ kpc while the subdominant strand shows a close correspondence to such stars. we conclude that ( 1 ) these two stream strands have different origins, ( 2 ) they are likely only close in projection, ( 3 ) the subdominant strand is tidal in origin, and ( 4 ) the subdominant strand is composed of " disk " material, gas and stars, with a chemical composition that marginally favors it coming from the small magellanic cloud.
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arxiv:2411.15044
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the nature of mashhoon ' s spin - rotation coupling is the interaction between a particle spin ( gravitomagnetic moment ) and a gravitomagnetic field. here we will consider the coupling of graviton spin to the weak gravitomagnetic fields by analyzing the lagrangian density of weak gravitational field, and hence study the purely gravitational generalization of mashhoon ' s spin - rotation couplings.
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arxiv:gr-qc/0408005
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we consider the set w of double zeros in ( 0, 1 ) for power series with coefficients in { - 1, 0, 1 }. we prove that w is disconnected, and estimate the minimum of w with high accuracy. we also show that [ 2 ^ ( - 1 / 2 ) - e, 1 ) is contained in w for some small, but explicit e > 0 ( this was only known for e = 0 ). these results have applications in the study of infinite bernoulli convolutions and connectedness properties of self - affine fractals.
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arxiv:math/0504545
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the redshifted 21 cm line of neutral hydrogen is a promising probe of the epoch of reionization ( eor ). however, its detection requires a thorough understanding and control of the systematic errors. we study two systematic biases observed in the lofar eor residual data after calibration and subtraction of bright discrete foreground sources. the first effect is a suppression in the diffuse foregrounds, which could potentially mean a suppression of the 21 cm signal. the second effect is an excess of noise beyond the thermal noise. the excess noise shows fluctuations on small frequency scales, and hence it can not be easily removed by foreground removal or avoidance methods. our analysis suggests that sidelobes of residual sources due to the chromatic point spread function and ionospheric scintillation can not be the dominant causes of the excess noise. rather, both the suppression of diffuse foregrounds and the excess noise can occur due to calibration with an incomplete sky model containing predominantly bright discrete sources. we show that calibrating only on bright sources can cause suppression of other signals and introduce an excess noise in the data. the levels of the suppression and excess noise depend on the relative flux of sources which are not included in the model with respect to the flux of modeled sources. we discuss possible solutions such as using only long baselines to calibrate the interferometric gain solutions as well as simultaneous multi - frequency calibration along with their benefits and shortcomings.
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arxiv:1605.07619
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we give the first examples of smooth projective varieties $ x $ over a finite field $ \ mathbb { f } $ admitting a non - algebraic torsion $ \ ell $ - adic cohomology class of degree $ 4 $ which vanishes over $ \ overline { \ mathbb { f } } $. we use them to show that two versions of the integral tate conjecture over $ \ mathbb { f } $ are not equivalent to one another and that a fundamental exact sequence of colliot - th \ ' el \ ` ene and kahn does not necessarily split. some of our examples have dimension $ 4 $, and are the first known examples of fourfolds with non - vanishing $ h ^ { 3 } _ { \ text { nr } } ( x, \ mathbb { q } _ { 2 } / \ mathbb { z } _ { 2 } ( 2 ) ) $.
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arxiv:2206.12732
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samarium doped bifeo3 compounds having nano - size crystallites were prepared by the ethylene glycol assisted sol - gel synthesis method. x - ray diffraction and sem measurements as well as raman spectroscopy and ftir experiments were used to clarify the evolution of the crystal structure on microscopic and local scale levels in the compounds having formula bi1 - xsmxfeo3, where x equals from 0 to 1. magnetization measurements along with the structural data were used to determine a correlation between magnetic properties and crystal structure of the compounds. the compounds with from x 0. 1 - 0. 2 are characterized by the sequence of the structural transitions driven by the dopant increase, from the polar rhombohedral phase to the non - polar orthorhombic phase via two - phase regions characterized by the presence of the anti - polar orthorhombic phase. the concentration regions ascribed to a coexistence of the rhombohedral and the anti - polar orthorhombic phases as well as theanti - polar orthorhombic and the non - polar orthorhombic phases are observed in the ranges from 0. 12 to 0. 15 and from 0. 15 to 0. 18 respectively. the compounds having single - phase rhombohedral structure are characterized by a release of remnant magnetization as compared to ceramics with similar chemical compositions but synthesized by the solid - state reaction method and having microscopic size crystallites. a correlation between the type of structural distortion, morphology of crystallites and an onset of remnant magnetization is discussed highlighting a difference in the evolution of crystal structure and magnetization observed for the sm - doped ceramics prepared by modified sol - gel method and conventional solid - state reaction technique.
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arxiv:2010.15439
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a morse 2 - function is a generic smooth map from a smooth manifold to a surface. in the absence of definite folds ( in which case we say that the morse 2 - function is indefinite ), these are natural generalizations of broken ( lefschetz ) fibrations. we prove existence and uniqueness results for indefinite morse 2 - functions mapping to arbitrary compact, oriented surfaces. " uniqueness " means there is a set of moves which are sufficient to go between two homotopic indefinite morse 2 - functions while remaining indefinite throughout. we extend the existence and uniqueness results to indefinite, morse 2 - functions with connected fibers.
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arxiv:1102.0750
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despite the extreme simplicity in their definition, spin glasses disclose a wide variety of non - trivial behaviors that are not yet fully understood. in this thesis we try to shed light on some of them, focusing on one hand on the search of phase transitions under perturbations of the hamiltonian, and on the other hand on the zero - temperature properties and responses to external stimuli. after introducing spin glasses through a historiographical review, and useful concepts on phase transitions and numerics, the results of two massive monte carlo campaigns on three - dimensional systems are shown. in the first one the de almeida - thouless transition is studied, and a new finite - size scaling ansatz is proposed, that accelerates the convergence to the thermodynamic limit. in the second one the phase diagram of the heisenberg spin glass with random exchange anisotropy is reconstructed. in the following part of the manuscript, surprising features of zero - temperature statics and dynamics of several spin glass models are found. among them, correlations between soft spins that arise spontaneously during avalanches, and the discovery of localized states that involve the presence of two - level systems.
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arxiv:1602.08239
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a quantum spin liquid ( qsl ) is an exotic state of matter in which electrons ' spins are quantum entangled over long distances, but do not show symmetry - breaking magnetic order in the zero - temperature limit. the observation of qsl states is a central aim of experimental physics, because they host collective excitations that transcend our knowledge of quantum matter ; however, examples in real materials are scarce. here, we report neutron - scattering measurements on ybmggao4, a qsl candidate in which yb3 + ions with effective spin - 1 / 2 occupy a triangular lattice. our measurements reveal a continuum of magnetic excitations - the essential experimental hallmark of a qsl - at very low temperature ( 0. 06 k ). the origin of this peculiar excitation spectrum is a crucial question, because isotropic nearest - neighbor interactions do not yield a qsl ground state on the triangular lattice. using measurements of the magnetic excitations close to the field - polarized state, we identify antiferromagnetic next - nearest - neighbor interactions in the presence of planar anisotropy as key ingredients for qsl formation in ybmggao4.
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arxiv:1607.03231
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universal fault - tolerant quantum computers, which promise to revolutionize computing, are currently limited by excessive noise in their constituent superconducting qubits. determining the dominant sources of this excess noise will lead to a clearer understanding of how to mitigate it in future superconducting systems. superconducting nanowire single - photon detectors ( snspds ) are devices that do not appear to suffer from such effects and have extremely low dark - count backgrounds. we propose to use snspds as low - background laboratories to study noise accumulation processes in superconducting systems with the purpose of explaining and mitigating noise in related quantum information systems. through these studies we also aim to increase the sensitive wavelengths of snspds above the current limits of 10 microns, which would open new regimes for dark matter detection, biology, space sciences, and quantum sensing.
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arxiv:2204.01919
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modern signal processing ( sp ) methods rely very heavily on probability and statistics to solve challenging sp problems. sp methods are now expected to deal with ever more complex models, requiring ever more sophisticated computational inference techniques. this has driven the development of statistical sp methods based on stochastic simulation and optimization. stochastic simulation and optimization algorithms are computationally intensive tools for performing statistical inference in models that are analytically intractable and beyond the scope of deterministic inference methods. they have been recently successfully applied to many difficult problems involving complex statistical models and sophisticated ( often bayesian ) statistical inference techniques. this survey paper offers an introduction to stochastic simulation and optimization methods in signal and image processing. the paper addresses a variety of high - dimensional markov chain monte carlo ( mcmc ) methods as well as deterministic surrogate methods, such as variational bayes, the bethe approach, belief and expectation propagation and approximate message passing algorithms. it also discusses a range of optimization methods that have been adopted to solve stochastic problems, as well as stochastic methods for deterministic optimization. subsequently, areas of overlap between simulation and optimization, in particular optimization - within - mcmc and mcmc - driven optimization are discussed.
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arxiv:1505.00273
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for a subshift over a finite alphabet, a measure of the complexity of the system is obtained by counting the number of nonempty cylinder sets of length $ n $. when this complexity grows exponentially, the automorphism group has been shown to be large for various classes of subshifts. in contrast, we show that subquadratic growth of the complexity implies that for a topologically transitive shift $ x $, the automorphism group $ \ aut ( x ) $ is small : if $ h $ is the subgroup of $ \ aut ( x ) $ generated by the shift, then $ \ aut ( x ) / h $ is periodic.
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arxiv:1403.0238
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we measure the excitation spectrum of a dipolar chromium bose einstein condensate with raman - bragg spectroscopy. the energy spectrum depends on the orientation of the dipoles with respect to the excitation momentum, demonstrating an anisotropy which originates from the dipole - dipole interactions between the atoms. we compare our results with the bogoliubov theory based on the local density approximation, and, at large excitation wavelengths, with numerical simulations of the time dependent gross - pitaevskii equation. our results show an anisotropy of the speed of sound
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arxiv:1205.6305
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the main contribution of this paper is an invariant extended kalman filter ( ekf ) for visual inertial navigation systems ( vins ). it is demonstrated that the conventional ekf based vins is not invariant under the stochastic unobservable transformation, associated with translations and a rotation about the gravitational direction. this can lead to inconsistent state estimates as the estimator does not obey a fundamental property of the physical system. to address this issue, we use a novel uncertainty representation to derive a right invariant error extended kalman filter ( riekf - vins ) that preserves this invariance property. riekf - vins is then adapted to the multistate constraint kalman filter framework to obtain a consistent state estimator. both monte carlo simulations and real - world experiments are used to validate the proposed method.
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arxiv:1702.07920
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in this paper, the notion of local algebraic fundamental groups of normal complex analytic singularities are generalized to certain profinite groups called $ d $ - local algebraic fundamental groups which turns out to be useful even for the study of usual local algebraic fundamental groups and the lefshetz type theorem for $ d $ - local algebraic fundamental groups is proved under certain conditions. the theorem yields, for example, the finiteness of the local algebraic fundamental groups of a certain class of four dimensional singularities and will be useful for the classification of three dimensional purely log terminal singularities.
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arxiv:1502.05766
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we present new theorems characterizing robust lyapunov functions and infinite horizon value functions in optimal control as unique viscosity solutions of partial differential equations. we use these results to further extend zubov ' s method for representing domains of attraction in terms of partial differential equation solutions.
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arxiv:math/0311267
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we show that systems driven by an external force and described by nose - hoover dynamics allow for a consistent nonequilibrium thermodynamics description when the thermostatted variable is initially assumed in a state of canonical equilibrium. by treating the " real " variables as the system and the thermostatted variable as the reservoir, we establish the first and second law of thermodynamics. as for hamiltonian systems, the entropy production can be expressed as a relative entropy measuring the system - reservoir correlations established during the dynamics.
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arxiv:1005.4631
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many recent delineation techniques owe much of their increased effectiveness to path classification algorithms that make it possible to distinguish promising paths from others. the downside of this development is that they require annotated training data, which is tedious to produce. in this paper, we propose an active learning approach that considerably speeds up the annotation process. unlike standard ones, it takes advantage of the specificities of the delineation problem. it operates on a graph and can reduce the training set size by up to 80 % without compromising the reconstruction quality. we will show that our approach outperforms conventional ones on various biomedical and natural image datasets, thus showing that it is broadly applicable.
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arxiv:1512.00747
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recently, text - to - image generation has exhibited remarkable advancements, with the ability to produce visually impressive results. in contrast, text - to - 3d generation has not yet reached a comparable level of quality. existing methods primarily rely on text - guided score distillation sampling ( sds ), and they encounter difficulties in transferring 2d attributes of the generated images to 3d content. in this work, we aim to develop an effective 3d generative model capable of synthesizing high - resolution textured meshes by leveraging both textual and image information. to this end, we introduce guide3d, a zero - shot text - and - image - guided generative model for 3d avatar generation based on diffusion models. our model involves ( 1 ) generating sparse - view images of a text - consistent character using diffusion models, and ( 2 ) jointly optimizing multi - resolution differentiable marching tetrahedral grids with pixel - aligned image features. we further propose a similarity - aware feature fusion strategy for efficiently integrating features from different views. moreover, we introduce two novel training objectives as an alternative to calculating sds, significantly enhancing the optimization process. we thoroughly evaluate the performance and components of our framework, which outperforms the current state - of - the - art in producing topologically and structurally correct geometry and high - resolution textures. guide3d enables the direct transfer of 2d - generated images to the 3d space. our code will be made publicly available.
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arxiv:2308.09705
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we study the propagation of singularities for semilinear schrodinger equations with quadratic hamiltonians, in particular for the semilinear harmonic oscillator. we show that the propagation still occurs along the flow the hamiltonian flow, but for sobolev regularities in a certain range and provided the notion of sobolev - wave front set is conveniently modified. the proof makes use of a weighted version of the paradifferential calculus, adapted to our situation. the results can be regarded as the schrodinger counterpart of those known for semilinear hyperbolic equations, which hold with the usual wave front set.
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arxiv:1407.8528
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we have given a summary on our theoretical predictions of three kinds of topological semimetals ( tsms ), namely, dirac semimetal ( dsm ), weyl semimetal ( wsm ) and node - line semimetal ( nlsm ). tsms are new states of quantum matters, which are different with topological insulators. they are characterized by the topological stability of fermi surface, whether it encloses band crossing point, i. e., dirac cone like energy node, or not. they are distinguished from each other by the degeneracy and momentum space distribution of the nodal points. to realize these intriguing topological quantum states is quite challenging and crucial to both fundamental science and future application. in 2012 and 2013, na $ _ 3 $ bi and cd $ _ 3 $ as $ _ 2 $ were theoretically predicted to be dsm, respectively. their experimental verifications in 2014 have ignited the hot and intensive studies on tsms. the following theoretical prediction of nonmagnetic wsm in taas family stimulated a second wave and many experimental works have come out in this year. in 2014, a kind of three dimensional crystal of carbon has been proposed to be nlsm due to negligible spin - orbit coupling and coexistence of time - reversal and inversion symmetry. though the final experimental confirmation of nlsm is still missing, there have been several theoretical proposals, including cu $ _ 3 $ pdn from us. in the final part, we have summarized the whole family of tsms and their relationship.
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arxiv:1603.04744
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the universality and scaling behaviour of hadronisation have been investigated in semi - inclusive neutral current deep inelastic ep scattering ; specifically the multiplicity and scaled momentum spectra of charged hadrons have been measured and analysed. the measurements are performed in the current region of the breit frame, as well as in the current fragmentation region of the hadronic centre - of - mass frame. the data collected at the hera ep collider by the h1 and zeus experiments are compared with similar measurements obtained in e + e - annihilation and with previous ep measurements as well as with leading - logarithm parton - shower predictions.
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arxiv:0810.3514
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hawking radiation is nowadays being understood as tunnelling through black hole horizons. here, the extension of the hamilton - jacobi approach to tunnelling for non - rotating and rotating black holes in different non - singular coordinate systems not only confirms this quantum emission from black holes but also reveals the new phenomenon of absorption into white holes by quantum mechanical tunnelling. the role of a boundary condition of total absorption or emission is also clarified.
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arxiv:0704.1746
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we present a measurement of the $ d ^ 0 $ - $ \ overline { d } ^ 0 $ mixing parameter $ y _ { cp } $ using a flavor - untagged sample of $ d ^ 0 \ to k _ s ^ 0k ^ + k ^ - $ decays. the measurement is based on a 673 fb $ ^ { - 1 } $ data sample recorded by the belle detector at the kekb asymmetric - energy $ e ^ + e ^ - $ collider. we find $ y _ { cp } = ( 0. 21 \ pm 0. 63 ( { \ rm stat. } ) \ pm 0. 78 ( \ rm syst. ) \ pm 0. 01 ( \ rm model ) ) % $.
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arxiv:0808.0074
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we consider a self - similar force - free wind flowing out of an infinitely thin disk located in the equatorial plane. on the disk plane, we assume that the magnetic stream function $ p $ scales as $ p \ propto r ^ \ nu $, where $ r $ is the cylindrical radius. we also assume that the azimuthal velocity in the disk is constant : $ v _ \ phi = mc $, where $ m < 1 $ is a constant. for each choice of the parameters $ \ nu $ and $ m $, we find an infinite number of solutions that are physically well - behaved and have fluid velocity $ \ leq c $ throughout the domain of interest. among these solutions, we show via physical arguments and time - dependent numerical simulations that the minimum - torque solution, i. e., the solution with the smallest amount of toroidal field, is the one picked by a real system. for $ \ nu \ geq 1 $, the lorentz factor of the outflow increases along a field line as $ \ gamma \ approx m ( z / \ rfp ) ^ { ( 2 - \ nu ) / 2 } \ approx r / r _ { \ rm a } $, where $ \ rfp $ is the radius of the foot - point of the field line on the disk and $ r _ { \ rm a } = \ rfp / m $ is the cylindrical radius at which the field line crosses the alfven surface or the light cylinder. for $ \ nu < 1 $, the lorentz factor follows the same scaling for $ z / \ rfp < m ^ { - 1 / ( 1 - \ nu ) } $, but at larger distances it grows more slowly : $ \ gamma \ approx ( z / \ rfp ) ^ { \ nu / 2 } $. for either regime of $ \ nu $, the dependence of $ \ gamma $ on $ m $ shows that the rotation of the disk plays a strong role in jet acceleration. on the other hand, the poloidal shape of a field line is given by $ z / \ rfp \ approx ( r / \ rfp ) ^ { 2 / ( 2 - \ nu ) } $ and is independent of $ m $. thus rotation has neither a collimating nor a decollimating effect on field lines, suggesting that relativistic astrophysical jets are not collimated by the rotational winding up of the magnetic field.
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arxiv:astro-ph/0610817
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the deuteron form factors are calculated using two model wave functions obtained from the 2007 cst high precision fits to $ np $ scattering data. included in the calculation are a new class of isoscalar $ np $ interaction currents which are automatically generated by the nuclear force model used in these fits. if the nuclear model wjc2 is used, a precision fit ( $ \ chi ^ 2 $ / datum $ \ eqsim1 $ ) to the sick global analysis ( ga ) of all $ ed $ elastic scattering data can be obtained by adjusting the unknown off - shell nucleon form factors $ f _ 3 ( q ^ 2 ) $ ( discussed before ) and $ f _ 4 ( q ^ 2 ) $ ( introduced in this paper ), and predicting the high $ q ^ 2 $ behavior of the neutron charge form factor $ g _ { en } ( q ^ 2 ) $ well beyond the region where it has been measured directly. relativistic corrections, isoscalar interaction currents, and off - shell effects are defined, discussed, and their size displayed. a rationale for extending $ ed $ elastic scattering measurements to higher $ q ^ 2 $ is presented.
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arxiv:1908.09421
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this study presents a novel high - order numerical method designed for solving the two - dimensional time - fractional convection - diffusion ( tfcd ) equation. the caputo definition is employed to characterize the time - fractional derivative. a weak singularity at the initial time ( $ t = 0 $ ) is encountered in the considered problem, which is effectively managed by adopting a discretization approach for the time - fractional derivative, where alikhanov ' s high - order l2 - 1 $ _ \ sigma $ formula is applied on a non - uniform fitted mesh, resulting in successful tackling of the singularity. a high - order two - dimensional compact operator is implemented to approximate the spatial variables. the alternating direction implicit ( adi ) approach is then employed to solve the resulting system of equations by decomposing the two - dimensional problem into two separate one - dimensional problems. the theoretical analysis, encompassing both stability and convergence aspects, has been conducted comprehensively, and it has shown that method is convergent with an order $ \ mathcal o \ left ( n _ t ^ { - \ min \ { 3 - \ alpha, \ theta \ alpha, 1 + 2 \ alpha, 2 + \ alpha \ } } + h _ x ^ 4 + h _ y ^ 4 \ right ) $, where $ \ alpha \ in ( 0, 1 ) $ represents the order of the fractional derivative, $ n _ t $ is the temporal discretization parameter and $ h _ x $ and $ h _ y $ represent spatial mesh widths. moreover, the parameter $ \ theta $ is utilized in the construction of the fitted mesh.
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arxiv:2308.08971
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autonomous driving is a complex and challenging task that aims at safe motion planning through scene understanding and reasoning. while vision - only autonomous driving methods have recently achieved notable performance, through enhanced scene understanding, several key issues, including lack of reasoning, low generalization performance and long - tail scenarios, still need to be addressed. in this paper, we present vlp, a novel vision - language - planning framework that exploits language models to bridge the gap between linguistic understanding and autonomous driving. vlp enhances autonomous driving systems by strengthening both the source memory foundation and the self - driving car ' s contextual understanding. vlp achieves state - of - the - art end - to - end planning performance on the challenging nuscenes dataset by achieving 35. 9 \ % and 60. 5 \ % reduction in terms of average l2 error and collision rates, respectively, compared to the previous best method. moreover, vlp shows improved performance in challenging long - tail scenarios and strong generalization capabilities when faced with new urban environments.
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arxiv:2401.05577
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wireless telephone speech is usually limited to the 300 - 3400 hz band, which reduces its quality. there is thus a growing demand for wideband speech systems that transmit from 50 hz to 8000 hz. this paper presents an algorithm to generate wideband speech from narrowband speech using as low as 500 bits / s of side information. the 50 - 300 hz band is predicted from the narrowband signal. a source - excitation model is used for the 3400 - 8000 hz band, where the excitation is extrapolated at the receiver, and the spectral envelope is transmitted. though some artifacts are present, the resulting wideband speech has enhanced quality compared to narrowband speech.
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arxiv:1602.08215
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in this paper, we derive closed - form expressions for significant statistical properties of the link signal - to - noise ratio ( snr ) and the separation distance in mobile ad hoc networks subject to ornstein - uhlenbeck ( ou ) mobility and rayleigh fading. in these systems, the snr is a critical parameter as it directly influences link performance. in the absence of signal fading, the distribution of the link snr depends exclusively on the squared distance between nodes, which is governed by the mobility model. in our analysis, nodes move randomly according to an ornstein - uhlenbeck process, using one tuning parameter to control the temporal dependency in the mobility pattern. we derive a complete statistical description of the squared distance and show that it forms a stationary markov process. then, we compute closed - form expressions for the probability density function ( pdf ), the cumulative distribution function ( cdf ), the bivariate pdf, and the bivariate cdf of the link snr. next, we introduce small - scale fading, modelled by a rayleigh random variable, and evaluate the pdf of the link snr for rational path loss exponents. the validity of our theoretical analysis is verified by extensive simulation studies. the results presented in this work can be used to quantify link uncertainty and evaluate stability in mobile ad hoc wireless systems.
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arxiv:1912.09776
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a novel definition of holographic correlation functions on the celestial sphere of minkowski space was recently introduced in arxiv : 2301. 01810 as the extrapolation of bulk time - ordered correlation functions to the celestial sphere. in this work, focusing on theories of scalar fields in $ ( d + 2 ) $ - dimensional minkowski space, we show that in perturbation theory such celestial correlation functions admit a conformal partial wave expansion with meromorphic spectral density, and hence also an expansion into conformal blocks. this is achieved in the hyperbolic slicing of minkowski space by extending the harmonic function ( ` ` spectral " ) decomposition of ads bulk - to - bulk propagators to the minkowski feynman propagator. we study the conformal partial wave expansion of celestial correlators for four - point contact and tree - level exchange diagrams, and extract the contributions to their conformal block expansions in the direct channel. when all scalar fields are massless, the tree - level exchange diagram takes a remarkably simple form and is given by a finite sum of conformal blocks ( and, for $ d = 2 $, their derivatives as well ). we also discuss the conformal partial wave expansion at the non - perturbative level, where lorentz unitarity manifests as positivity of the spectral density.
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arxiv:2502.03087
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the quantisation of gauge theories usually procedes through the introduction of ghost fields and brst symmetry. in the case of quantum gravity in the presence of boundaries, the brst - invariant boundary value problem for the gauge field operators is non - elliptic, and consequently the definition of the effective action using heat - kernel techniques becomes problematic. this paper examines general classes of brst - invariant boundary conditions and presents new boundary conditions for quantum gravity which fix the extrinsic curvature on the boundary and lead to a well - defined effective action. this prompts a discussion of the wider issue of non - ellipticity in brst - invariant boundary value problems and when the use of gauge - fixing terms on the boundary can resolve the issue.
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arxiv:1301.0717
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this paper explores distributed nash equilibrium seeking problems for games in which the players have limited knowledge on other players ' actions. in particular, the involved players are considered to be high - order integrators with their control inputs constrained within a pre - specified region. a linear transformation for the players ' dynamics is firstly utilized to facilitate the design of bounded control inputs incorporating multiple saturation functions. by introducing consensus protocols with adaptive and time - varying gains, the unknown actions for players are distributively estimated. then, a fully distributed nash equilibrium seeking strategy is exploited, showcasing its remarkable properties : i ) ensuring the boundedness of control inputs ; ii ) avoiding any global information / parameters ; and iii ) allowing the graph to be directed. based on lyapunov stability analysis, it is theoretically proved that the proposed distributed control strategy can lead all the players ' actions to the nash equilibrium. finally, an illustrative example is given to validate effectiveness of the proposed method.
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arxiv:2108.06573
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using the replica method we calculate the mean spectral density of the hessian matrix at the global minimum of a random $ n \ gg 1 $ dimensional isotropic, translationally invariant gaussian random landscape confined by a parabolic potential with fixed curvature $ \ mu > 0 $. simple landscapes with generically a single minimum are typical for $ \ mu > \ mu _ { c } $, and we show that the hessian at the global minimum is always { \ it gapped }, with the low spectral edge being strictly positive. when approaching from above the transitional point $ \ mu = \ mu _ { c } $ separating simple landscapes from ' glassy ' ones, with exponentially abundant minima, the spectral gap vanishes as $ ( \ mu - \ mu _ c ) ^ 2 $. for $ \ mu < \ mu _ c $ the hessian spectrum is qualitatively different for ' moderately complex ' and ' genuinely complex ' landscapes. the former are typical for short - range correlated random potentials and correspond to 1 - step replica - symmetry breaking mechanism. their hessian spectra turn out to be again gapped, with the gap vanishing on approaching $ \ mu _ c $ from below with a larger critical exponent, as $ ( \ mu _ c - \ mu ) ^ 4 $. at the same time in the ' most complex ' landscapes with long - ranged power - law correlations the replica symmetry is completely broken. we show that in that case the hessian remains gapless for all values of $ \ mu < \ mu _ c $, indicating the presence of ' marginally stable ' spatial directions. finally, the potentials with { \ it logarithmic } correlations share both 1rsb nature and gapless spectrum. the spectral density of the hessian always takes the semi - circular form, up to a shift and an amplitude that we explicitly calculate.
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arxiv:1806.05294
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as a first step toward realizing a dynamical system that evolves while spontaneously determining its own rule for time evolution, function dynamics ( fd ) is analyzed. fd consists of a functional equation with a self - referential term, given as a dynamical system of a 1 - dimensional map. through the time evolution of this system, a dynamical graph ( a network ) emerges. this graph has three interesting properties : i ) vertices appear as stable elements, ii ) the terminals of directed edges change in time, and iii ) some vertices determine the dynamics of edges, and edges determine the stability of the vertices, complementarily. two aspects of fd are studied, the generation of a graph ( network ) structure and the dynamics of this graph ( network ) in the system.
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arxiv:nlin/0202033
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ordinary differential equations appear in celestial mechanics ( planets, stars and galaxies ) ; numerical linear algebra is important for data analysis ; stochastic differential equations and markov chains are essential in simulating living cells for medicine and biology. = = = vector analysis = = = vector analysis, also called vector calculus, is a branch of mathematical analysis dealing with vector - valued functions. = = = scalar analysis = = = scalar analysis is a branch of mathematical analysis dealing with values related to scale as opposed to direction. values such as temperature are scalar because they describe the magnitude of a value without regard to direction, force, or displacement that value may or may not have. = = = tensor analysis = = = = = other topics = = calculus of variations deals with extremizing functionals, as opposed to ordinary calculus which deals with functions. harmonic analysis deals with the representation of functions or signals as the superposition of basic waves. geometric analysis involves the use of geometrical methods in the study of partial differential equations and the application of the theory of partial differential equations to geometry. clifford analysis, the study of clifford valued functions that are annihilated by dirac or dirac - like operators, termed in general as monogenic or clifford analytic functions. p - adic analysis, the study of analysis within the context of p - adic numbers, which differs in some interesting and surprising ways from its real and complex counterparts. non - standard analysis, which investigates the hyperreal numbers and their functions and gives a rigorous treatment of infinitesimals and infinitely large numbers. computable analysis, the study of which parts of analysis can be carried out in a computable manner. stochastic calculus – analytical notions developed for stochastic processes. set - valued analysis – applies ideas from analysis and topology to set - valued functions. convex analysis, the study of convex sets and functions. idempotent analysis – analysis in the context of an idempotent semiring, where the lack of an additive inverse is compensated somewhat by the idempotent rule a + a = a. tropical analysis – analysis of the idempotent semiring called the tropical semiring ( or max - plus algebra / min - plus algebra ). constructive analysis, which is built upon a foundation of constructive, rather than classical, logic and set theory. intuitionistic analysis, which is developed from constructive logic like constructive analysis but also incorporates choice sequences. paraconsistent analysis, which is built upon a foundation of paraconsis
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https://en.wikipedia.org/wiki/Mathematical_analysis
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this memoir is dedicated to the late francis hayin ree, a formative influence shaping my work in statistical mechanics. between 1963 and 1968 we collaborated on nine papers published in the journal of chemical physics. those dealt with the virial series, cell models, and computer simulation. all of them were directed toward understanding the statistical thermodynamics of simple model systems. our last joint work is also the most cited, with over 1000 citations, " melting transition and communal entropy for hard spheres ", submitted 3 may 1968 and published that october. here i summarize my own most recent work on compressible time - reversible two - dimensional maps. these simplest of model systems are amenable to computer simulation and are providing stimulating and surprising results.
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arxiv:2003.10220
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superatomic molecular orbitals ( samo ) in c60 are ideal building blocks for functional nanostructures. however, imaging them spatially in the gas phase has been unsuccessful. it is found experimentally that if c60 is excited by an 800 - nm laser, the photoelectron casts an anisotropic velocity image, but the image becomes isotropic if excited at a 400 - nm wavelength. this diffuse image difference has been attributed to electron thermal ionization, but more recent experiments ( 800 nm ) reveal a clear non - diffuse image superimposed on the diffuse image, whose origin remains a mystery. here we show that the non - diffuse anisotropic image is the precursor of the $ f $ samo. we predict that four 800 - nm photons can directly access the $ 1f $ samo, and with one more photon, can image the orbital, with the photoelectron angular distribution having two maxima at 0 $ ^ \ circ $ and 180 $ ^ \ circ $ and two humps separated by 56. 5 $ ^ \ circ $. since two 400 - nm photons only resonantly excite the spherical $ 1s $ samo and four 800 - nm photon excite the anisotropic $ 1f $ samo, our finding gives a natural explanation of the non - diffuse image difference, complementing the thermal scenario.
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arxiv:1504.06899
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while there has been substantial empirical work identifying factors that influence the contribution to, and use of open source software, we have as yet little theory that identifies the key constructs and relationships that would allow us to explain and predict how open source ecosystems function. what is needed is a clearly articulated and empirically validated theory of open source ecosystems. such a theory should : $ \ bullet $ explain why, how, and when key resources - - - primarily the work of developers - - - are attracted to or depart from a project or an ecosystem. $ \ bullet $ explain why, how, and when projects and ecosystems move through a life cycle, from initiation, growth, maturity, and decline and death. $ \ bullet $ explain how decisions about use are made, and how the cumulatively influence the socio - technical position of a project within an ecosystem, and the relations of ecosystems to each other. the remainder of this chapter provides a sketch of such a theory in the form of a set of propositions, which may form the foundation for future empirical work
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arxiv:1905.05985
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in this paper we obtain a new fully explicit constant for the p \ ' olya - vinogradov inequality for primitive characters. given a primitive character $ \ chi $ modulo $ q $, we prove the following upper bound \ begin { align * } \ left | \ sum _ { 1 \ le n \ le n } \ chi ( n ) \ right | \ le c \ sqrt { q } \ log q, \ end { align * } where $ c = 3 / ( 4 \ pi ^ 2 ) + o _ q ( 1 ) $ for even characters and $ c = 3 / ( 8 \ pi ) + o _ q ( 1 ) $ for odd characters, with explicit $ o _ q ( 1 ) $ terms. this improves a result of frolenkov and soundararajan for large $ q $. we proceed, following hildebrand, obtaining the explicit version of a result by montgomery - - vaughan on partial gaussian sums and an explicit burgess - like result on convoluted dirichlet characters.
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arxiv:2001.05114
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middleboxes in a computer network system inspect and analyse network traffic to detect malicious communications, monitor system performance and provide operational services. however, encrypted traffic hinders the ability of middleboxes to perform such services. a common practice in addressing this issue is by employing a " man - in - the - middle " ( mitm ) approach, wherein an encrypted traffic flow between two endpoints is interrupted, decrypted and analysed by the middleboxes. the mitm approach is straightforward and is used by many organisations, but there are both practical and privacy concerns. due to the cost of the mitm appliances and the latency incurred in the encrypt - decrypt processes, enterprises continue to seek solutions that are less costly. there were discussion on the many efforts required to configure mitm. besides, mitm violates end - to - end privacy guarantee, raising privacy concerns and issues on compliance especially with the rising awareness on user privacy. furthermore, some of the mitm implementations were found to be flawed. consequently, new practical and privacy - preserving techniques for inspection over encrypted traffic were proposed. we examine them to compare their advantages, limitations and challenges. we categorise them into four main categories by defining a framework that consist of system architectures, use cases, trust and threat models. these are searchable encryption, access control, machine learning and trusted hardware. we first discuss the man - in - the - middle approach as a baseline, then discuss in details each of them, and provide an in - depth comparisons of their advantages and limitations. by doing so we describe practical constraints, advantages and pitfalls towards adopting the techniques. we also give insights on the gaps between research work and industrial deployment, which leads us to the discussion on the challenges and research directions.
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arxiv:2101.04338
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progress has been achieved recently in object detection given advancements in deep learning. nevertheless, such tools typically require a large amount of training data and significant manual effort to label objects. this limits their applicability in robotics, where solutions must scale to a large number of objects and variety of conditions. this work proposes an autonomous process for training a convolutional neural network ( cnn ) for object detection and pose estimation in robotic setups. the focus is on detecting objects placed in cluttered, tight environments, such as a shelf with multiple objects. in particular, given access to 3d object models, several aspects of the environment are physically simulated. the models are placed in physically realistic poses with respect to their environment to generate a labeled synthetic dataset. to further improve object detection, the network self - trains over real images that are labeled using a robust multi - view pose estimation process. the proposed training process is evaluated on several existing datasets and on a dataset collected for this paper with a motoman robotic arm. results show that the proposed approach outperforms popular training processes relying on synthetic - but not physically realistic - data and manual annotation. the key contributions are the incorporation of physical reasoning in the synthetic data generation process and the automation of the annotation process over real images.
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arxiv:1703.03347
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we prove pointwise bounds for $ l ^ 2 $ eigenfunctions of the laplace - beltrami operator on locally symmetric spaces with $ \ mathbb { q } $ - rank one if the corresponding eigenvalues lie below the continuous part of the $ l ^ 2 $ spectrum. furthermore, we use these bounds in order to obtain some results concerning the $ l ^ p $ spectrum.
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arxiv:1005.2980
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we study the accuracy of the expected euler characteristic approximation to the distribution of the maximum of a smooth, centered, unit variance gaussian process f. using a point process representation of the error, valid for arbitrary smooth processes, we show that the error is in general exponentially smaller than any of the terms in the approximation. we also give a lower bound on this exponential rate of decay in terms of the maximal variance of a family of gaussian processes f ^ x, derived from the original process f.
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arxiv:math/0507442
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this study is the first known attempt to search for gamma - ray burst repeaters combining data from gamma - ray experiments flying on board different satellites and making use of information derived from the bursts detected simultaneously by all the experiments. the proposed method is suitable to correlate grb data provided by experiments that overlap partially or totally in time. as an application of this method we have correlated the positions of 57 gamma - ray bursts observed by watch / granat and watch / eureca with 1905 bursts detected by batse. comparing the so - called ` ` added correlation ' ' between the watch and batse bursts with that obtained with simulated watch catalogues, we conclude that there is no indication of recurrent activity of watch bursts in the batse sample. we derive an upper limit of 15. 8 %, with a confidence level of 94 %, for the number of watch gamma - ray bursts that could represent a population of repeaters in the batse sample.
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arxiv:astro-ph/9804239
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the efficient energy storage devices are crucial to meet the soaring global energy demand for sustainable future. recently, the sodium - ion batteries ( sibs ) have emerged as one of the excellent cost effective solution due to the uniform geographical distribution and abundance of sodium. here, we use hard carbon ( hc ) as an anode and na $ _ 3 $ v $ _ 2 $ ( po $ _ 4 $ ) $ _ 3 $ / c ( nvp / c ) as a cathode to fabricate a hc $ | | $ nvp / c full cell battery and understand its electrochemical performance and diffusion kinetics. these materials are characterized through the analysis of x - ray diffraction and raman spectroscopy to confirm their single phase and structure. the full cell demonstrates a high operating voltage of $ \ sim $ 3. 3 v, with minimal polarization of 0. 05 v, attributed to the lower working voltage of the hc. interestingly, for the full cell battery we find the specific capacity of around 70 mah / g at 0. 1 c and even around 35 mah / g at high current rate of 5 c along with high rate capability up to 55 cycles. the diffusion kinetics of the full cell battery is investigated through detailed analysis of cv curves at various scan rates, and the diffusion coefficient is found to be 5 - - 8 $ \ times $ 10 $ ^ { - 11 } $ cm $ ^ 2 $ / s for the anodic as well as cathodic peaks.
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arxiv:2401.15420
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exposure to large language model output is rapidly increasing. how will seeing ai - generated ideas affect human ideas? we conducted an experiment ( 800 + participants, 40 + countries ) where participants viewed creative ideas that were from chatgpt or prior experimental participants and then brainstormed their own idea. we varied the number of ai - generated examples ( none, low, or high exposure ) and if the examples were labeled as ' ai ' ( disclosure ). our dynamic experiment design - - ideas from prior participants in an experimental condition are used as stimuli for future participants in the same experimental condition - - speaks to the interdependent process of cultural creation : creative ideas are built upon prior ideas. hence, we capture the compounding effects of having llms ' in the culture loop '. we find that high ai exposure ( but not low ai exposure ) did not affect the creativity of individual ideas but did increase the average amount and rate of change of collective idea diversity. ai made ideas different, not better. there were no main effects of disclosure. we also found that self - reported creative people were less influenced by knowing an idea was from ai and that participants may knowingly adopt ai ideas when the task is difficult. our findings suggest that introducing ai ideas may increase collective diversity but not individual creativity.
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arxiv:2401.13481
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evidence - enhanced detectors present remarkable abilities in identifying malicious social text with related evidence. however, the rise of large language models ( llms ) brings potential risks of evidence pollution to confuse detectors. this paper explores how to manipulate evidence, simulating potential misuse scenarios including basic pollution, and rephrasing or generating evidence by llms. to mitigate its negative impact, we propose three defense strategies from both the data and model sides, including machine - generated text detection, a mixture of experts, and parameter updating. extensive experiments on four malicious social text detection tasks with ten datasets present that evidence pollution, especially the generate strategy, significantly compromises existing detectors. on the other hand, the defense strategies could mitigate evidence pollution, but they faced limitations for practical employment, such as the need for annotated data and huge inference costs. further analysis illustrates that polluted evidence is of high quality, would compromise the model calibration, and could ensemble to amplify the negative impact.
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arxiv:2410.12600
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we investigate the mass modifications of open strange mesons ( vector $ k ^ * $ and axial vector $ k _ 1 $ ) in ( magnetized ) isospin asymmetric nuclear matter using quantum chromodynamics sum rule ( qcdsr ) approach. the in - medium decay widths of $ k ^ * $ $ \ rightarrow $ $ k \ pi $ and $ k _ 1 $ $ \ rightarrow $ $ k ^ * \ pi $ are studied from the mass modifications of $ k _ 1 $, $ k ^ * $ and $ k $ mesons, using a light quark - antiquark pair creation model, namely the $ { } ^ 3 p _ 0 $ model. the in - medium decay width for $ k _ 1 $ $ \ rightarrow $ $ k ^ * \ pi $ is compared with the decay widths calculated using a phenomenological lagrangian. the effects of magnetic fields are also studied on the mass and the partial decay width of the vector $ k ^ * $ meson decaying to $ k \ pi $. within the qcd sum rule approach, the medium effects on the masses of the open strange mesons are calculated from the light quark condensates and the gluon condensates in the hadronic medium. the quark condensates are calculated from the medium modifications of the scalar fields ( $ \ sigma $, $ \ zeta $, and $ \ delta $ ) in the mean field approximation within a chiral $ su ( 3 ) $ model, while the scalar gluon condensate is obtained from the medium modification of a scalar dilaton field ( $ \ chi $ ), which is introduced within the model to imitate the scale invariance breaking of qcd.
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arxiv:2302.14493
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in this article, we combine casting experiments and quantitative simulations to present a novel multiscale modeling approach to predict local primary dendritic spacings in metallic alloys solidified in conditions relevant to industrial casting processes. to this end, primary dendritic spacings were measured in instrumented casting experiments in al - cu alloys containing 1 \, wt \ % and 4 \, wt \ % of cu, and they were compared to spacing stability ranges and average spacings in dendritic arrays simulated using phase - field ( pf ) and dendritic needle network ( dnn ) models. it is first shown that pf and dnn lead to similar results for the al - 1 \, wt \ % cu alloy, using a dendrite tip selection constant calculated with pf in the dnn simulations. pf simulations cannot achieve quantitative predictions for the al - 4 \, wt \ % cu alloy because they are too computationally demanding due to the large separation of scale between tip radius and diffusion length, a characteristic feature of non - dilute alloys. nevertheless, the results of dnn simulations for non - dilute al - cu alloys are in overall good agreement with our experimental results as well as with those of an extensive literature review. simulations consistently suggest a widening of the pdas stability range with a decrease of the temperature gradient as the microstructure goes from cellular - dendrites to well - developed hierarchical dendrites.
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arxiv:2101.07780
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we report a coherence - preserving photon frequency down - conversion experiment based on difference - frequency generation in a periodically poled lithium niobate waveguide, at the single - photon level. the coherence of the process has been demonstrated by measuring the phase coherence of pseudo single - photon time - bin qubits after frequency conversion with an interference visibility of > 96 %. this interface could be of interest for quantum repeater based hybrid networks.
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arxiv:1006.4585
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driven by the remarkable progress in diffusion models, text - to - image generation has made significant strides, creating a pressing demand for automatic quality evaluation of generated images. current state - of - the - art automatic evaluation methods heavily rely on multi - modal large language models ( mllms ), particularly powerful commercial models like gpt - 4o. while these models are highly effective, their substantial costs limit scalability in large - scale evaluations. adopting open - source mllms is an alternative ; however, their performance falls short due to significant limitations in processing multi - modal data compared to commercial mllms. to tackle these problems, we first propose a task decomposition evaluation framework based on gpt - 4o to automatically construct a new training dataset, where the complex evaluation task is decoupled into simpler sub - tasks, effectively reducing the learning complexity. based on this dataset, we design innovative training strategies to effectively distill gpt - 4o ' s evaluation capabilities into a 7b open - source mllm, minicpm - v - 2. 6. furthermore, to reliably and comprehensively assess prior works and our proposed model, we manually annotate a meta - evaluation benchmark that includes chain - of - thought explanations alongside quality scores for generated images. experimental results demonstrate that our distilled open - source mllm significantly outperforms the current state - of - the - art gpt - 4o - base baseline, viescore, with over 4. 6 \ % improvement in spearman and kendall correlations with human judgments.
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arxiv:2411.15488
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we explore an online reinforcement learning ( rl ) paradigm to dynamically optimize parallel particle tracing performance in distributed - memory systems. our method combines three novel components : ( 1 ) a work donation algorithm, ( 2 ) a high - order workload estimation model, and ( 3 ) a communication cost model. first, we design an rl - based work donation algorithm. our algorithm monitors workloads of processes and creates rl agents to donate data blocks and particles from high - workload processes to low - workload processes to minimize program execution time. the agents learn the donation strategy on the fly based on reward and cost functions designed to consider processes ' workload changes and data transfer costs of donation actions. second, we propose a workload estimation model, helping rl agents estimate the workload distribution of processes in future computations. third, we design a communication cost model that considers both block and particle data exchange costs, helping rl agents make effective decisions with minimized communication costs. we demonstrate that our algorithm adapts to different flow behaviors in large - scale fluid dynamics, ocean, and weather simulation data. our algorithm improves parallel particle tracing performance in terms of parallel efficiency, load balance, and costs of i / o and communication for evaluations with up to 16, 384 processors.
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arxiv:2109.05679
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the process e + e - - > mu + mu - has been studied by snd detector at vepp - 2m e + e - collider in the phi ( 1020 ) - resonance energy region. the measured effective phi meson leptonic branching ratio : b ( phi - > l + l - ) = sqrt { b ( phi - > e + e - ) * b ( phi - > mu + mu - ) } = ( 2. 89 + - 0. 10 + - 0. 06 ) * 10 ^ { - 4 } agrees well with the pdg value b ( phi - > e + e - ) = ( 2. 91 + - 0. 07 ) * 10 ^ { - 4 } confirming mu - e universality. without additional assumption of mu - e universality the branching ratio b ( phi - > mu + mu - ) = ( 2. 87 + - 0. 20 + - 0. 14 ) * 10 ^ { - 4 } was obtained.
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arxiv:hep-ex/0102029
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generating a collision - free robot motion is crucial for safe applications in real - world settings. this requires an accurate model of all obstacle shapes within the constrained robot cell, which is particularly challenging and time - consuming. the difficulty is heightened in flexible production lines, where the environment model must be updated each time the robot cell is modified. furthermore, sensor - based methods often necessitate costly hardware and calibration procedures, and can be influenced by environmental factors ( e. g., light conditions or reflections ). to address these challenges, we present a novel data - driven approach to modeling a cluttered workspace, leveraging solely the robot internal joint encoders to capture exploratory motions. by computing the corresponding swept volume, we generate a ( conservative ) mesh of the environment that is subsequently used for collision checking within established path planning and control methods. our method significantly reduces the complexity and cost of classical environment modeling by removing the need for cad files and external sensors. we validate the approach with the kuka lbr iisy collaborative robot in a pick - and - place scenario. in less than three minutes of exploratory robot motions and less than four additional minutes of computation time, we obtain an accurate model that enables collision - free motions. our approach is intuitive, easy - to - use, making it accessible to users without specialized technical knowledge. it is applicable to all types of industrial robots or cobots.
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arxiv:2502.01484
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continuing advances in neural interfaces have enabled simultaneous monitoring of spiking activity from hundreds to thousands of neurons. to interpret these large - scale data, several methods have been proposed to infer latent dynamic structure from high - dimensional datasets. one recent line of work uses recurrent neural networks in a sequential autoencoder ( sae ) framework to uncover dynamics. saes are an appealing option for modeling nonlinear dynamical systems, and enable a precise link between neural activity and behavior on a single - trial basis. however, the very large parameter count and complexity of saes relative to other models has caused concern that saes may only perform well on very large training sets. we hypothesized that with a method to systematically optimize hyperparameters ( hps ), saes might perform well even in cases of limited training data. such a breakthrough would greatly extend their applicability. however, we find that saes applied to spiking neural data are prone to a particular form of overfitting that cannot be detected using standard validation metrics, which prevents standard hp searches. we develop and test two potential solutions : an alternate validation method ( " sample validation " ) and a novel regularization method ( " coordinated dropout " ). these innovations prevent overfitting quite effectively, and allow us to test whether saes can achieve good performance on limited data through large - scale hp optimization. when applied to data from motor cortex recorded while monkeys made reaches in various directions, large - scale hp optimization allowed saes to better maintain performance for small dataset sizes. our results should greatly extend the applicability of saes in extracting latent dynamics from sparse, multidimensional data, such as neural population spiking activity.
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arxiv:1908.07896
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a new record - high room temperature electron hall mobility ( $ { \ mu } _ { rt } = 194 \ space cm ^ { 2 } / v \ space s $ at $ n \ sim 8 \ times 10 ^ { 15 } \ space cm ^ { - 3 } $ ) for $ { \ beta } $ - ga2o3 is demonstrated in the unintentionally doped thin film grown on ( 010 ) semi - insulating substrate via metalorganic chemical vapor deposition ( mocvd ). a peak electron mobility of $ \ sim 9500 \ space cm ^ { 2 } / v \ space s $ is achieved at 45 k. further investigation on the transport properties indicate the existence of sheet charges near the epi - layer / substrate interface. si is identified as the primary contributor to the background carrier in both the epi - layer and the interface, originated from both surface contamination as well as growth environment. pre - growth hydrofluoric acid cleaning of the substrate lead to an obvious decrease of si impurity both at interface and in epi - layer. in addition, the effect of mocvd growth condition, particularly the chamber pressure, on the si impurity incorporation is studied. a positive correlation between the background charge concentration and the mocvd growth pressure is confirmed. it is noteworthy that in a $ { \ beta } $ - ga2o3 film with very low bulk charge concentration, even a reduced sheet charge density can play an important role in the charge transport properties.
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arxiv:2004.13089
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we show that the factor ordering ambiguities associated with the loop quantisation of the gravitational part of the cosmological hamiltonian constraint, disappear at the level of wheeler - dewitt equation only for a particular choice of lattice refinement model, which coincides with constraints imposed from phenomenological and consistency arguments.
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arxiv:0806.0595
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various versions of club are shown to be different. a question of soukup, fuchino and juhasz, is it consistent to have a stick without club, is answered as a consequence. the more detailed version of the paper, which is coming up, also answers a question of galvin.
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arxiv:math/9710215
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the rich star clusters in the large magellanic cloud ( lmc ) are ideal for studying the process of star formation. here we focus on the determination of age spreads amongst the massive stars in two young clusters, ngc1818 and ngc1805. we present colour magnitude diagrams ( derived from hst data ) for these clusters, and discuss the difficulties in age spread determination.
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arxiv:astro-ph/9907246
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it is commonly maintained that entanglement is necessary to beat the shot noise limit in the sensitivity with which certain parameters can be measured in interferometric experiments. here we show that, with a fluctuating number of two - mode bosons, the shot - noise limit can be beaten by non - entangled bosonic states with all bosons in one mode. for a given finite maximum number of bosons, we calculate the optimal one - and two - mode bosonic states, and show that in the absence of losses, noon states are the optimal two - mode bosonic states.
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arxiv:1109.0206
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we make two tiny corrections to our previous paper with the same title, and also obtain, as a bonus, something new.
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arxiv:0711.0224
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recent modeling of the warm absorber in active galactic nuclei has proved the usefulness of constant total ( gas plus radiation ) pressure models, which are highly stratified in temperature and density. we explore the consistency of those models when the typical variation of the flux from the central source is taken into account. we perform a variability study of the warm absorber response, based on timescales and our photoionization code titan. we show that the ionization and recombination timescales are much shorter than the dynamical timescale. clouds very close to the central black hole will maintain their equilibrium since the characteristic variability timescales of the nuclear source are longer than cloud timescales. for more distant clouds, the density structure has no time to vary, in response to the variations of the temperature or ionization structure, and such clouds will show the departure from the constant pressure equilibrium. we explore the impact of this departure on the observed properties of the transmitted spectrum and soft x - ray variability : ( i ) non uniform velocities, of the order of sound speed, appear due to pressure gradients, up to typical values of 100 km / s. these velocities lead to the broadening of lines. this broadening is usually observed and very difficult to explain otherwise. ( ii ) energy - dependent fractional variability amplitude in soft x - ray range has a broader hump around ~ 1 - 2 kev, and ( iv ) the plot of the equivalent hydrogen column density vs. ionization parameter is steeper than for equilibrium clouds. the results have the character of a preliminary study and should be supplemented in the future with full time - dependent radiation transfer and dynamical computations.
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arxiv:astro-ph/0701112
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android applications collecting data from users must protect it according to the current legal frameworks. such data protection has become even more important since in 2018 the european union rolled out the general data protection regulation ( gdpr ). since app developers are not legal experts, they find it difficult to integrate privacy - aware practices into source code development. despite these legal obligations, developers have limited tool support to reason about data protection throughout their app development process. this paper explores the use of static program slicing and software visualization to analyze privacy - relevant data flows in android apps. we introduce sliceviz, a web tool that analyzes an android app by slicing all privacy - relevant data sources detected in the source code on the back - end. it then helps developers by visualizing these privacy - relevant program slices. we conducted a user study with 12 participants demonstrating that sliceviz effectively aids developers in identifying privacy - relevant properties in android apps. our findings indicate that program slicing can be employed to identify and reason about privacy - relevant data flows in android applications. with further usability improvements, developers can be better equipped to handle privacy - sensitive information.
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arxiv:2503.16640
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facial expression manipulation aims at editing facial expression with a given condition. previous methods edit an input image under the guidance of a discrete emotion label or absolute condition ( e. g., facial action units ) to possess the desired expression. however, these methods either suffer from changing condition - irrelevant regions or are inefficient for fine - grained editing. in this study, we take these two objectives into consideration and propose a novel method. first, we replace continuous absolute condition with relative condition, specifically, relative action units. with relative action units, the generator learns to only transform regions of interest which are specified by non - zero - valued relative aus. second, our generator is built on u - net but strengthened by multi - scale feature fusion ( msf ) mechanism for high - quality expression editing purposes. extensive experiments on both quantitative and qualitative evaluation demonstrate the improvements of our proposed approach compared to the state - of - the - art expression editing methods. code is available at \ url { https : / / github. com / junleen / expression - manipulator }.
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arxiv:2004.03132
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many real world problems exhibit patterns that have periodic behavior. for example, in astrophysics, periodic variable stars play a pivotal role in understanding our universe. an important step when analyzing data from such processes is the problem of identifying the period : estimating the period of a periodic function based on noisy observations made at irregularly spaced time points. this problem is still a difficult challenge despite extensive study in different disciplines. the paper makes several contributions toward solving this problem. first, we present a nonparametric bayesian model for period finding, based on gaussian processes ( gp ), that does not make strong assumptions on the shape of the periodic function. as our experiments demonstrate, the new model leads to significantly better results in period estimation when the target function is non - sinusoidal. second, we develop a new algorithm for parameter optimization for gp which is useful when the likelihood function is very sensitive to the setting of the hyper - parameters with numerous local minima, as in the case of period estimation. the algorithm combines gradient optimization with grid search and incorporates several mechanisms to overcome the high complexity of inference with gp. third, we develop a novel approach for using domain knowledge, in the form of a probabilistic generative model, and incorporate it into the period estimation algorithm. experimental results on astrophysics data validate our approach showing significant improvement over the state of the art in this domain.
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arxiv:1111.1315
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in this work we study the mutual benefits of two common computer vision tasks, self - supervised depth estimation and semantic segmentation from images. for example, to help unsupervised monocular depth estimation, constraints from semantic segmentation has been explored implicitly such as sharing and transforming features. in contrast, we propose to explicitly measure the border consistency between segmentation and depth and minimize it in a greedy manner by iteratively supervising the network towards a locally optimal solution. partially this is motivated by our observation that semantic segmentation even trained with limited ground truth ( 200 images of kitti ) can offer more accurate border than that of any ( monocular or stereo ) image - based depth estimation. through extensive experiments, our proposed approach advances the state of the art on unsupervised monocular depth estimation in the kitti.
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arxiv:2004.00171
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the geometric properties of quantum states are crucial for understanding many physical phenomena in quantum mechanics, condensed matter physics, and optics. the central object describing these properties is the quantum geometric tensor, which unifies the berry curvature and the quantum metric. in this work, we use the differential - geometric framework of vector bundles to analyze the properties of parameter - dependent quantum states and generalize the quantum geometric tensor to this setting. this construction is based on an arbitrary connection on a hermitian vector bundle, which defines a notion of quantum state transport in parameter space, and a sub - bundle projector, which constrains the set of accessible quantum states. we show that the sub - bundle geometry is similar to that of submanifolds in riemannian geometry and is described by a generalization of the gauss - codazzi - mainardi equations. this leads to a novel definition of the quantum geometric tensor, which contains an additional curvature contribution. to illustrate our results, we describe the sub - bundle geometry arising in the semiclassical treatment of dirac fields propagating in curved spacetime and show how the quantum geometric tensor, with its additional curvature contributions, is obtained in this case. as a concrete example, we consider dirac fermions confined to a hyperbolic plane and demonstrate how spatial curvature influences the quantum geometry. this work sets the stage for further exploration of quantum systems in curved geometries, with applications in both high - energy physics and condensed matter systems.
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arxiv:2503.17163
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we propose a new zero - shot event detection method by multi - modal distributional semantic embedding of videos. our model embeds object and action concepts as well as other available modalities from videos into a distributional semantic space. to our knowledge, this is the first zero - shot event detection model that is built on top of distributional semantics and extends it in the following directions : ( a ) semantic embedding of multimodal information in videos ( with focus on the visual modalities ), ( b ) automatically determining relevance of concepts / attributes to a free text query, which could be useful for other applications, and ( c ) retrieving videos by free text event query ( e. g., " changing a vehicle tire " ) based on their content. we embed videos into a distributional semantic space and then measure the similarity between videos and the event query in a free text form. we validated our method on the large trecvid med ( multimedia event detection ) challenge. using only the event title as a query, our method outperformed the state - of - the - art that uses big descriptions from 12. 6 % to 13. 5 % with map metric and 0. 73 to 0. 83 with roc - auc metric. it is also an order of magnitude faster.
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arxiv:1512.00818
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the eclipsing hard x - ray source igr j16479 - 4514 is the supergiant fast x - ray transient ( sfxt ) with the shortest orbital period ( 3. 32 days ). this allowed us to perform a 250 ks long x - ray observation with suzaku in 2012 february, covering most of its orbit, including the eclipse egress. outside the eclipse, the source luminosity is around a few 1e34erg / s. the x - ray spectrum can be fit with an absorbed power law together with a neutral iron emission line at 6. 4 kev. the column density is constant at 1e23 cm - 2 outside the x - ray eclipse. during the eclipse it is lower, consistent with a scattering origin for the low x - ray emission during the eclipse by the supergiant companion wind. the scattered x - ray emission during the x - ray eclipse is used to directly probe the density of the companion wind at the orbital separation, resulting in 7e - 14 g / cm3, which translates into a ratio mdot _ w / v _ terminal = 7e - 17 solar masses / km of the wind mass loss rate to the wind terminal velocity. this ratio, assuming reasonable terminal velocities in the range 500 - 3000 km / s, translates into an accretion luminosity two orders of magnitude higher than that observed. we conclude that a mechanism reducing the accretion rate onto the compact object is at work, likely due to the neutron star magnetosphere.
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arxiv:1302.1702
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one way to study the kronecker coefficients is to focus on the kronecker cone, which is generated by the triples of partitions corresponding to non - zero kronecker coefficients. in this article we are interested in producing particular faces of this cone, formed of stable triples ( a notion defined by j. stembridge in 2014 ), using many geometric notions - - principally those of dominant and well - covering pairs - - and results of n. ressayre. this extends a result obtained independently by l. manivel and e. vallejo in 2014 or 2015, expressed in terms of additive matrix. to illustrate the fact that it allows to produce quite a few new faces of the kronecker cone, we give at the end of the article details about what our results yield for " small dimensions ".
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arxiv:1805.10218
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vulnerable individuals have a limited ability to make reasonable financial decisions and choices and, thus, the level of care that is appropriate to be provided to them by financial institutions may be different from that required for other consumers. therefore, identifying vulnerability is of central importance for the design and effective provision of financial services and products. however, validating the information that customers share and respecting their privacy are both particularly important in finance and this poses a challenge for identifying and caring for vulnerable populations. this position paper examines the potential of the combination of two emerging technologies, decentralized identifiers ( dids ) and verifiable credentials ( vcs ), for the identification of vulnerable consumers in finance in an efficient and privacy - preserving manner.
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arxiv:2106.06053
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this research focuses on the algorithms and approaches for learning hidden markov models ( hmms ) and compares hmm learning methods and algorithms. hmm is a statistical markov model in which the system being modeled is assumed to be a markov process. one of the essential characteristics of hmms is their learning capabilities. learning algorithms are introduced to overcome this inconvenience. one of the main problems of the newly proposed algorithms is their validation. this research aims by using the theoretical and experimental analysis to 1 ) compare hmms learning algorithms proposed in the literature, 2 ) provide a validation tool for new hmm learning algorithms, and 3 ) present a new algorithm called asexual reproduction optimization ( aro ) with one of its extensions - modified aro ( maro ) - as a novel hmm learning algorithm to use the validation tool proposed. according to the literature findings, it seems that populationbased algorithms perform better among hmms learning approaches than other algorithms. also, the testing was done in nine benchmark datasets. the results show that maro outperforms different algorithms in objective functions in terms of accuracy and robustness.
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arxiv:2102.07112
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computer simulations have long been key to understanding and designing phase - change materials ( pcms ) for memory technologies. machine learning is now increasingly being used to accelerate the modelling of pcms, and yet it remains challenging to simultaneously reach the length and time scales required to simulate the operation of real - world pcm devices. here, we show how ultra - fast machine - learned interatomic potentials, based on the atomic cluster expansion ( ace ) framework, enable simulations of pcms reflecting applications in devices with excellent scalability on high - performance computing platforms. we report full - cycle simulations - - including the time - consuming crystallisation process ( from digital " zeroes " to " ones " ) - - thus representing the entire programming cycle for cross - point memory devices. we also showcase a simulation of full - cycle operations, relevant to neuromorphic computing, in a mushroom - type device geometry. our work provides a springboard for the atomistic modelling of pcm - based memory and neuromorphic computing devices - - and, more widely, it illustrates the power of highly efficient ace ml models for materials science and engineering.
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arxiv:2502.08393
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in this paper we investigate a power law coupling higgs inflationary model in which the background geometry is determined by the palatini ' s variational principle. the geometrical symmetries of the background geometry determine the invariant form of the action of the model and the background geometry resulted is of the weyl - integrable type. the invariant action results also invariant under the $ u ( 1 ) $ group, which in general is not compatible with the weyl group of invariance of the background geometry. however, we found compatibility conditions between the geometrical and physical symmetries of the action in the strong coupling limit. we found that if we start with a non - minimally coupled to gravity action, when we impose the congruence between the both groups of symmetries we end with an invariant action of the scalar - tensor type. we obtain a nearly scale invariant power spectrum for the inflaton fluctuations for certain values of some parameters of the model. also we obtain va \ - lues for the tensor to scalar ratio in agreement with planck and bicep observational data : $ r < 0. 032 $.
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arxiv:2404.09107
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force is a 1. 2 tonnes small mission dedicated for wide - band fine - imaging x - ray observation. it covers from 1 to 80 kev with a good angular resolution of $ 15 " $ half - power - diameter. it is proposed to be launched around mid - 2020s and designed to reach a limiting sensitivity as good as $ f _ x ( 10 - 40 ~ { \ rm kev } ) = 3 \ times 10 ^ { - 15 } $ ~ erg cm $ ^ { - 2 } $ s $ ^ { - 1 } $ kev $ ^ { - 1 } $ within 1 ~ ms. this number is one order of magnitude better than current best one. with its high - sensitivity wide - band coverage, force will probe the new science field of " missing bhs ", searching for families of black holes of which populations and evolutions are not well known. other point - source and diffuse - source sciences are also considered. force will also provide the " hard x - ray coverage " to forthcoming large soft x - ray observatories.
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arxiv:1807.11175
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the main information of a webpage is usually mixed between menus, advertisements, panels, and other not necessarily related information ; and it is often difficult to automatically isolate this information. this is precisely the objective of content extraction, a research area of widely interest due to its many applications. content extraction is useful not only for the final human user, but it is also frequently used as a preprocessing stage of different systems that need to extract the main content in a web document to avoid the treatment and processing of other useless information. other interesting application where content extraction is particularly used is displaying webpages in small screens such as mobile phones or pdas. in this work we present a new technique for content extraction that uses the dom tree of the webpage to analyze the hierarchical relations of the elements in the webpage. thanks to this information, the technique achieves a considerable recall and precision. using the dom structure for content extraction gives us the benefits of other approaches based on the syntax of the webpage ( such as characters, words and tags ), but it also gives us a very precise information regarding the related components in a block, thus, producing very cohesive blocks.
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arxiv:1210.6113
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the objects of study in this paper are hopf algebras $ h $ which are finitely generated algebras over an algebraically closed field and are extensions of a commutative hopf algebra by a finite dimensional hopf algebra. basic structural and homological properties are recalled and classes of examples are listed. bounds are obtained on the dimensions of simple $ h $ - modules, and the structure of $ h $ is shown to be severely constrained when the finite dimensional extension is semisimple and cosemisimple.
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arxiv:1907.10527
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combining loss and gain components in one photonic heterostructure opens a new route to efficient manipulation by radiation, transmission, absorption, and scattering of electromagnetic waves. therefore, loss / gain structures enabling $ { \ cal pt } $ - symmetric and $ { \ cal pt } $ - broken phases for eigenvalues have extensively been studied in the last decade. in particular, translation from one phase to another, which occurs at the critical point in the two - channel structures with one - dimensional loss / gain components, is often associated with one - way transmission. in this report, broadband mixing of the $ { \ cal pt } $ - symmetric and $ { \ cal pt } $ - broken phases for eigenvalues is theoretically demonstrated in heterostructures with four channels obtained by combining a one - dimensional loss / gain bilayer and one or two thin polarization - converting components ( pccs ). the broadband phase mixing in the four - channel case is expected to yield advanced transmission and absorption regimes. various configurations are analyzed, which are distinguished in symmetry properties and polarization conversion regime of pccs. the conditions necessary for phase mixing are discussed. the simplest two - component configurations with broadband mixing are found, as well as the more complex three - component configurations wherein symmetric and broken sets are not yet mixed and appear in the neighbouring frequency ranges. peculiarities of eigenvalue behaviour are considered for different permittivity ranges of loss / gain medium, i. e., from epsilon - near - zero to high - epsilon regime.
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arxiv:1802.08840
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\ mathcal { k } _ { n + 1 } : = \ left \ { f \ in \ mathcal { c } ^ { n + 1 } \ left [ - 1, 1 \ right ] : \ \ sup \ limits _ { x \ in [ - 1, 1 ] } { \ left \ lvert f ^ { ( n + 1 ) } ( x ) \ right \ rvert \ leq1 } \ right \ } $.
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arxiv:1905.00461
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real - time semantic segmentation plays a significant role in industry applications, such as autonomous driving, robotics and so on. it is a challenging task as both efficiency and performance need to be considered simultaneously. to address such a complex task, this paper proposes an efficient cnn called multiply spatial fusion network ( msfnet ) to achieve fast and accurate perception. the proposed msfnet uses class boundary supervision to process the relevant boundary information based on our proposed multi - features fusion module which can obtain spatial information and enlarge receptive field. therefore, the final upsampling of the feature maps of 1 / 8 original image size can achieve impressive results while maintaining a high speed. experiments on cityscapes and camvid datasets show an obvious advantage of the proposed approach compared with the existing approaches. specifically, it achieves 77. 1 % mean iou on the cityscapes test dataset with the speed of 41 fps for a 1024 * 2048 input, and 75. 4 % mean iou with the speed of 91 fps on the camvid test dataset.
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arxiv:1911.07217
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we study the gravitational wave phenomenology in models of solitosynthesis. in such models, a first order phase transition is precipitated by a period in which non - topological solitons with a conserved global charge ( q - balls ) accumulate charge. as such, the nucleation rate of critical bubbles differs significantly from thermal phase transitions. in general we find that the peak amplitude of the gravitational wave spectrum resulting from solitosynthesis is stronger than that of a thermal phase transition and the timescale of the onset of nonlinear plasma dynamics is comparable to hubble. we demonstrate this explicitly in an asymmetric dark matter model, and discuss current and future constraints in this scenario.
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arxiv:1910.09562
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factor analysis, often regarded as a bayesian variant of matrix factorization, offers superior capabilities in capturing uncertainty, modeling complex dependencies, and ensuring robustness. as the deep learning era arrives, factor analysis is receiving less and less attention due to their limited expressive ability. on the contrary, contrastive learning has emerged as a potent technique with demonstrated efficacy in unsupervised representational learning. while the two methods are different paradigms, recent theoretical analysis has revealed the mathematical equivalence between contrastive learning and matrix factorization, providing a potential possibility for factor analysis combined with contrastive learning. motivated by the interconnectedness of contrastive learning, matrix factorization, and factor analysis, this paper introduces a novel contrastive factor analysis framework, aiming to leverage factor analysis ' s advantageous properties within the realm of contrastive learning. to further leverage the interpretability properties of non - negative factor analysis, which can learn disentangled representations, contrastive factor analysis is extended to a non - negative version. finally, extensive experimental validation showcases the efficacy of the proposed contrastive ( non - negative ) factor analysis methodology across multiple key properties, including expressiveness, robustness, interpretability, and accurate uncertainty estimation.
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arxiv:2407.21740
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as a natural consequence of cosmological hierarchical structure formation, sub - parsec supermassive black hole binaries ( smbhbs ) should be common in galaxies but thus far have eluded spectroscopic identification. based on four decades of optical spectroscopic monitoring, we report that the nucleus of ngc 5548, a nearby seyfert galaxy long suspected to have experienced a major merger about one billion years ago, exhibits long - term variability with a period of 14 years in the optical continuum and broad hbeta emission line. remarkably, the double - peaked profile of hbeta shows systematic velocity changes with a similar period. these pieces of observations plausibly indicate that a smbhb resides in the center of ngc 5548. the complex, secular variations in the line profiles can be explained by orbital motion of a binary with equal mass and a semi - major axis of 22 light - days ( corresponding to 18 milli - parsec ). at a distance of 75 mpc, ngc 5548 is one of the nearest sub - parsec smbhb candidates that offers an ideal laboratory for gravitational wave detection.
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arxiv:1602.05005
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hierarchical probabilistic models, such as gaussian mixture models, are widely used for unsupervised learning tasks. these models consist of observable and latent variables, which represent the observable data and the underlying data - generation process, respectively. unsupervised learning tasks, such as cluster analysis, are regarded as estimations of latent variables based on the observable ones. the estimation of latent variables in semi - supervised learning, where some labels are observed, will be more precise than that in unsupervised, and one of the concerns is to clarify the effect of the labeled data. however, there has not been sufficient theoretical analysis of the accuracy of the estimation of latent variables. in a previous study, a distribution - based error function was formulated, and its asymptotic form was calculated for unsupervised learning with generative models. it has been shown that, for the estimation of latent variables, the bayes method is more accurate than the maximum - likelihood method. the present paper reveals the asymptotic forms of the error function in bayesian semi - supervised learning for both discriminative and generative models. the results show that the generative model, which uses all of the given data, performs better when the model is well specified.
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arxiv:1308.2029
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we present new spectroscopic observations of the early type, double - lined eclipsing binary v446 \, cep. the radial velocities and the photometric data obtained by $ hipparcos $ were analysed for deriving the astrophysical parameters of the components. masses and radii were determined as m $ _ p $ = 17. 94 $ \ pm $ 1. 16 m $ _ { \ odot } $ and r $ _ p $ = 8. 33 $ \ pm $ 0. 29 r $ _ { \ odot } $, m $ _ s $ = 2. 64 $ \ pm $ 0. 30 m $ _ { \ odot } $ and r $ _ s $ = 2. 13 $ \ pm $ 0. 10 r $ _ { \ odot } $ for the components of v446 \, cep. our analyses show that v446 \, cep is a detached algol - type system. based on the position of the components plotted on the theoretical hertzsprung - russell diagram, we estimate that the age of v446 \, cep is about 10 myr, neglecting the effects of mass - loss and mass exchange between the components. using the ubvjhk magnitudes and interstellar absorption we estimated the mean distance to the system v446 \, cep as 1100 $ \ pm $ 62 \, pc.
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arxiv:1406.0499
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we investigate the long - time dynamics of a sir epidemic model in the case of a population of pathogens infecting a homogeneous host population. the pathogen population is structured by a genotypic variable. when the initial mass of the maximal fitness set is positive, we give a precise description of the convergence of the orbit, including a formula for the asymptotic distribution. when this initial mass is zero, we show the persistence of the population of infected and the concentration of the population of pathogens on the set of genotypic traits that maximize the fitness. we also investigate precisely the case of a finite number of regular global maxima and show that the initial distribution may have an influence on the support of the eventual distribution. in particular, the natural process of competition is not always selecting a unique species, but several species may coexist as long as they maximize the fitness function. in some configurations, species that maximize the fitness may still get extinct depending on the shape of the initial distribution and some other parameter of the model, and we provide a way to characterize when this unexpected extinction happens. finally, we provide an example of a pathological situation in which the distribution never reaches a stationary distribution but oscillates forever around the set of fitness maxima.
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arxiv:2107.06418
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cued speech ( cs ) is an advanced visual phonetic encoding system that integrates lip reading with hand codings, enabling people with hearing impairments to communicate efficiently. cs video generation aims to produce specific lip and gesture movements of cs from audio or text inputs. the main challenge is that given limited cs data, we strive to simultaneously generate fine - grained hand and finger movements, as well as lip movements, meanwhile the two kinds of movements need to be asynchronously aligned. existing cs generation methods are fragile and prone to poor performance due to template - based statistical models and careful hand - crafted pre - processing to fit the models. therefore, we propose a novel gloss - prompted diffusion - based cs gesture generation framework ( called glossdiff ). specifically, to integrate additional linguistic rules knowledge into the model. we first introduce a bridging instruction called \ textbf { gloss }, which is an automatically generated descriptive text to establish a direct and more delicate semantic connection between spoken language and cs gestures. moreover, we first suggest rhythm is an important paralinguistic feature for cs to improve the communication efficacy. therefore, we propose a novel audio - driven rhythmic module ( arm ) to learn rhythm that matches audio speech. moreover, in this work, we design, record, and publish the first chinese cs dataset with four cs cuers. extensive experiments demonstrate that our method quantitatively and qualitatively outperforms current state - of - the - art ( sota ) methods. we release the code and data at https : / / glossdiff. github. io /.
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arxiv:2404.19277
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we present time - dependent models of the accretion disks created during compact object mergers, focusing on the energy available from accretion at late times and the composition of the disk and its outflows. we calculate the dynamics near the outer edge of the disk, which contains the majority of the mass and sets the accretion rate onto the central black hole. this allows us to follow the evolution over much longer timescales than current hydrodynamic simulations. at late times the disk becomes advective and its properties asymptote to self - similar solutions with accretion rate dm / dt ~ t ^ ( - 4 / 3 ) ( neglecting outflows ). this late - time accretion can in principle provide sufficient energy to power the late - time activity observed from some short - duration gamma - ray bursts ( grbs ). however, because outflows during the advective phase unbind the majority of the remaining mass, it is difficult for the remnant disk alone to produce significant accretion power well beyond the onset of the advective phase. unless the viscosity is quite low ( alpha ~ 1e - 3 ), this occurs before the start of observed flaring at ~ 30 s ; continued mass inflow thus appears required to explain the late - time activity from short grbs. we show that the composition of the disk freezes - out relatively neutron - rich ( electron fraction ye ~ 0. 3 ). roughly 1e - 2 msun of this neutron - rich material is ejected by winds at late times. during earlier, neutrino - cooled phases of accretion, neutrino irradiation of the disk produces a wind with ye ~ 0. 5, which synthesizes at most ~ 1e - 3 msun of ni56. we highlight what conditions are favorable for ni56 production and predict, in the best cases, optical and infrared transients peaking ~ 0. 5 - 2 days after the burst, with fluxes a factor of ~ 10 below the current observational limits.
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arxiv:0805.4415
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the l \ ' evy, jumping process, defined in terms of the jumping size distribution and the waiting time distribution, is considered. the jumping rate depends on the process value. the fractional diffusion equation, which contains the variable diffusion coefficient, is solved in the diffusion limit. that solution resolves itself to the stretched gaussian when the order parameter $ \ mu \ to2 $. the truncation of the l \ ' evy flights, in the exponential and power - law form, is introduced and the corresponding random walk process is simulated by the monte carlo method. the stretched gaussian tails are found in both cases. the time which is needed to reach the limiting distribution strongly depends on the jumping rate parameter. when the cutoff function falls slowly, the tail of the distribution appears to be algebraic.
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arxiv:0906.1706
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gas electron multipliers have undergone a very consistent development since their invention in 1997. their production procedures have been tuned in such a way that nowadays it is possible to produce foils with areas of the order of the square meter that can operate at a reasonable gain, uniform over large areas and with a good stability in what concerns electrical discharges. for the third run of lhc, they will be included in the cms and alice experiments after significant upgrades of the detectors, confirming that these structures are suitable for very large experiments. in the special case of time projection chambers, the ion backflow and the energy resolution are sensitive issues that must be addressed and the gem has shown to be able to deal with both of them. in this work, a stack of three gems with different pitches has been studied as a possible future approach for ion - backflow suppression to be used in tpcs and other detection concepts. with this approach, an ion backflow of 1 % with an energy resolution of 12 % at 5. 9 kev has been achieved with the detector operating in an ar / co2 ( 90 / 10 ) mixture at a gain of ~ 2000.
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arxiv:1803.09382
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simulation - based verification is beneficial for assessing otherwise dangerous or costly on - road testing of autonomous vehicles ( av ). this paper addresses the challenge of efficiently generating effective tests for simulation - based av verification using software testing agents. the multi - agent system ( mas ) programming paradigm offers rational agency, causality and strategic planning between multiple agents. we exploit these aspects for test generation, focusing in particular on the generation of tests that trigger the precondition of an assertion. on the example of a key assertion we show that, by encoding a variety of different behaviours respondent to the agent ' s perceptions of the test environment, the agency - directed approach generates twice as many effective tests than pseudo - random test generation, while being both efficient and robust. moreover, agents can be encoded to behave naturally without compromising the effectiveness of test generation. our results suggest that generating tests using agency - directed testing significantly improves upon random and simultaneously provides more realistic driving scenarios.
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arxiv:1912.05434
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course material for mathematical methods of theoretical physics intended for an undergraduate audience.
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arxiv:1203.4558
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the realization of optoelectronic devices on paper has been an outstanding challenge due to the large surface roughness and incompatible nature of paper with optical materials. here, we demonstrate a new class of optoelectronic devices on a piece of printing paper using graphene as an electrically reconfigurable optical medium. our approach relies on electro - modulation of optical properties of multilayer graphene on paper via blocking the interband electronic transitions. the paper based devices yield high optical contrast in the visible spectrum with fast response speed. pattering graphene into multiple pixels, folding paper into 3 - dimensional shapes or printing coloured ink on paper substrates enable us to demonstrate novel optoelectronic devices which cannot be realized with wafer - based techniques.
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arxiv:1801.04616
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