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we discuss spin - wave transport in anisotropic ferromagnets with an emphasis on the zeroes of the band edges as a function of a magnetic field. an associated divergence of the magnon spin should be observable by enhanced magnon conductivities in non - local experiments, especially in two - dimensional ferromagnets.
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arxiv:2304.10709
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we discuss the identification of attracting sets using combinatorial multivector fields ( cmvf ) from conley - morse - forman theory. a cmvf is a dynamical system induced by the action of a continuous dynamical system on a phase space discretization that can be represented as a lefschetz complex. there is a rich theory under development establishing the connections between the induced and underlying dynamics and emphasizing computability. we introduce the main ideas behind this theory and demonstrate how it can be used to identify regions of interest within the global dynamics via graph - based algorithms and the connection matrix.
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arxiv:2503.23079
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the problem of parameter estimation by the continuous time observations of a deterministic signal in white gaussian noise is considered. the asymptotic properties of the maximul likelihood estimator are described in the asymptotics of small noise ( large siglal - to - noise ratio ). we are interested by the situation when there is a misspecification in the regularity conditions. in particular it is supposed that the statistician uses a discontinuous ( change - point type ) model of signal, when the true signal is continuously differentiable function of the unknown parameter.
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arxiv:1509.02715
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we present a detailed analysis of spitzer - irac images obtained toward six herbig - haro objects ( hh 54 / 211 / 212, l 1157 / 1448, bhr 71 ). our analysis includes : ( 1 ) comparisons in morphology between the four irac bands ( 3. 6, 4. 5, 5. 8 and 8. 0 um ), and h2 1 - 0 s ( 1 ) at 2. 12 um for three out of six objects ; ( 2 ) measurements of spectral energy distributions ( seds ) at selected positions ; and ( 3 ) comparisons of these results with calculations of thermal h2 emission at lte ( 207 lines in four bands ) and non - lte ( 32 - 45 lines, depending on particle for collisions ). we show that the morphologies observed at 3. 6 and 4. 5 um are similar to each other, and to h2 1 - 0 s ( 1 ). this is well explained by thermal h2 emission at non - lte if the dissociation rate is significantly larger than 0. 002 - 0. 02, allowing thermal collisions to be dominated by atomic hydrogen. in contrast, the 5. 8 and 8. 0 um emission shows different morphologies from the others in some regions. this emission appears to be more enhanced at the wakes in bow shocks, or less enhanced in patchy structures in the jet. these tendencies are explained by the fact that thermal h2 emission in the 5. 8 and 8. 0 um band is enhanced in regions at lower densities and temperatures. throughout, the observed similarities and differences in morphology between four bands and 1 - 0 s ( 1 ) are well explained by thermal h2 emission. the observed seds are categorized into : - ( a ) those in which the flux monotonically increases with wavelength ; and ( b ) those with excess emission at 4. 5 - um. the type - a seds are explained by thermal h2 emission, in particular with simple shock models with a power - law cooling function. our calculations suggest that the type - b seds require extra contaminating emission in the 4. 5 - um band. the co vibrational emission is the most promising candidate, and the other contaminants discussed to date are not likely to explain the observed seds.
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arxiv:1008.1111
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we obtained a $ \ psi _ 1 $ estimate for the sum of rademacher random variables under condition that they are dependent.
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arxiv:1804.10709
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we report on quantum interference between a pair of counterpropagating quantum hall edge states that are separated by a high quality tunnel barrier. observed aharonov - bohm oscillations are analyzed in terms of resonant tunneling between coupled luttinger liquids that creates bound electronic states between pairs of tunnel centers that act like interference slits. we place a lower bound in the range of 20 - 40 $ \ mu $ m for the phase coherence length and directly confirm the extended phase coherence of quantum hall edge states.
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arxiv:cond-mat/0407641
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rubio de francia proved the one - sided littlewood - - paley inequality for arbitrary intervals in $ l ^ p $, $ 2 \ le p < \ infty $. in this article, his methods are developed and employed to prove an analogue of such an inequality " beyond the index $ p = \ infty $ ", i. e., for spaces of h \ " older functions and bmo.
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arxiv:1211.0696
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we discuss the extension of our recent work hep - th / 0410272, hep - th / 0410273 to general conifold transitions and type - iia string theory.
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arxiv:hep-th/0501164
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an important objective of the classical processing of stationary random sequences under nonparametric uncertainty is the problem of filtering in case when the distribution of the underlying signal is unknown. in this paper it is assumed that an unknown useful signal $ ( s _ n ) _ { n \ ge1 } $ is markov. this allows us to construct an estimate of the useful signal, expressed in terms of the distribution density function of an observable random sequence $ ( x _ n ) _ { n \ ge1 } $. the equation of the optimal bayesian estimation ( so called equation of optimal filtering ) of such signal has been received by a. v. dobrovidov. our main result is the following. it is proved that when the unobservable markov sequence is defined by a linear equation with the gaussian noise, the equation of optimal filtering coincides with the classical kalman ' s filter and the conditional expectation defined by the theorem on normal correlation.
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arxiv:1402.1823
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we investigate various relaxations of additivity for set maps into banach spaces in the context of representations of amenable groups. specifically, we establish conditions under which asymptotically additive and almost additive set maps are equivalent. for banach lattices, we further show that these notions are related to a third weak form of additivity adapted to the order structure of the space. by utilizing these equivalences and reducing non - additive settings to the additive one by finding suitable additive realizations, we derive new non - additive ergodic theorems for amenable group representations into banach spaces and streamline proofs of existing results in certain cases.
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arxiv:2501.14581
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the bc meson is composed of two heavy quarks of distinct flavor. measurements of its lifetime and production properties have been made based on semileptonic bc to j / psi + l + x decays using data collected with the cdf ii detector corresponding to an integrated luminosity of 1 fb - 1. the bc average lifetime ctau is measured to be 142. 5 + 15. 8 - 14. 8 ( stat ) 5. 5 ( syst ) mum. the measurements of the ratio of the production cross section times branching ratio of bc to j / psi + mu + nu relative to b + to j / psi + k were done for two pt ( b ) thresholds : for pt ( b ) greater 4 gev / c as 0. 295 + / - 0. 040 ( stat ) + 0. 033 - 0. 026 ( syst. ) 0. 036 ( pt spectrum ) and for pt ( b ) greater 6 gev / c as 0. 227 + / - 0. 033 ( stat ) + 0. 024 - 0. 017 ( syst. ) + / - 0. 014 ( pt spectrum ).
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arxiv:0910.3013
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it is known that self - adjoint hamiltonians with purely discrete eigenvalues can be written as ( infinite ) linear combination of mutually orthogonal projectors with eigenvalues as coefficients of the expansion. the projectors are defined by the eigenvectors of the hamiltonians. in some recent papers, this expansion has been extended to the case in which these eigenvectors form a riesz basis or, more recently, a $ \ d $ - quasi basis, \ cite { bell, bit }, rather than an orthonormal basis. here we discuss what can be done when these sets are replaced by parseval frames. this interest is motivated by physical reasons, and in particular by the fact that the { \ em mathematical } hilbert space where the physical system is originally defined, contains sometimes also states which cannot really be occupied by the { \ em physical } system itself. in particular, we show what changes in the spectrum of the observables, when going from orthonormal bases to parseval frames. in this perspective we propose the notion of $ e $ - connection for observables. several examples are discussed.
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arxiv:2010.05043
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the high chemical reactivity of strontium, which can opacify a viewport exposed to a strontium atomic source, is a concern for some atomic physics experiments where it is sometimes necessary to send a laser beam counter - propagating relative to the atomic beam. while a number of experiments use heated sapphire windows to reduce strontium deposition and increase the viewport lifetime, here we study another possibility, consisting of sending the laser beam into the atomic flux by reflecting it off a mirror at 45 $ ^ { \ circ } $ exposed to the strontium flux. we present our attempt to find a substrate that can be exposed to strontium and maintain high reflectivity. we first present the formation of a strontium metallic mirror under high flux ( $ > 10 ^ { 13 } $ at / s / cm $ ^ 2 $ ) on a sapphire substrate, and measure its reflectivity at 45 $ ^ \ circ $ to be 0. 65 ( s ) and 0. 51 ( p ). on two other substrates, initially reflective metallic mirrors, we show for slightly lower fluxes ( i. e., a factor of 3 ) that some reaction - most probably oxidation - is able to prevent the formation of the metallic layer even in high vacuum conditions. instead, we observe the growth of a dielectric transparent medium. despite the continuous deposition of strontium, the back surface reflectivity continues to dominate. we show the unusual evolution of reflectivity on these substrates, and emphasize two observations : i ) a sharp threshold in the strontium flux separating transparent material growth from lossy material growth ; ii ) strontium ' s highly efficient capture of oxygen, even from rarefied sources : here mostly the residual high vacuum pressure ( 10 $ ^ { - 7 } $ mbar full pressure ) and possibly a protective sio $ _ 2 $ surface on one of the substrates.
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arxiv:1802.08499
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linear preferential attachment ( nlpa ), existing nodes in the network gain new edges proportionally to the node degree raised to a constant positive power, α { \ displaystyle \ alpha }. formally, this means that the probability that node i { \ displaystyle i } gains a new edge is given by p i = k i α j k j α. { \ displaystyle p _ { i } = { \ frac { k _ { i } ^ { \ alpha } } { \ sum _ { j } k _ { j } ^ { \ alpha } } }. } if α = 1 { \ displaystyle \ alpha = 1 }, nlpa reduces to the ba model and is referred to as " linear ". if 0 < α < 1 { \ displaystyle 0 < \ alpha < 1 }, nlpa is referred to as " sub - linear " and the degree distribution of the network tends to a stretched exponential distribution. if α > 1 { \ displaystyle \ alpha > 1 }, nlpa is referred to as " super - linear " and a small number of nodes connect to almost all other nodes in the network. for both α < 1 { \ displaystyle \ alpha < 1 } and α > 1 { \ displaystyle \ alpha > 1 }, the scale - free property of the network is broken in the limit of infinite system size. however, if α { \ displaystyle \ alpha } is only slightly larger than 1 { \ displaystyle 1 }, nlpa may result in degree distributions which appear to be transiently scale free. = = = fitness model = = = another model where the key ingredient is the nature of the vertex has been introduced by caldarelli et al. here a link is created between two vertices i, j { \ displaystyle i, j } with a probability given by a linking function f ( η i, η j ) { \ displaystyle f ( \ eta _ { i }, \ eta _ { j } ) } of the fitnesses of the vertices involved. the degree of a vertex i is given by k ( η i ) = n 0 ∞ f ( η i, η j ) ρ ( η j ) d η j { \ displaystyle k ( \ eta _ { i } ) = n \ int _ { 0 } ^ { \ infty } f ( \ eta _ { i }, \ eta _ { j } ) \ rho ( \ eta _ { j } ) \, d \ eta _
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https://en.wikipedia.org/wiki/Network_science
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federated learning ( fl ) has gained increasing attention due to privacy - preserving collaborative training on decentralized clients, mitigating the need to upload sensitive data to a central server directly. nonetheless, recent research has underscored the risk of exposing private data to adversaries, even within fl frameworks. in general, existing methods sacrifice performance while ensuring resistance to privacy leakage in fl. we overcome these issues and generate diverse models at a global server through the proposed stochastic bidirectional parameter update mechanism. using diverse models, we improved the generalization and feature representation in the fl setup, which also helped to improve the robustness of the model against privacy leakage without hurting the model ' s utility. we use global models from past fl rounds to follow systematic perturbation in parameter space at the server to ensure model generalization and resistance against privacy attacks. we generate diverse models ( in close neighborhoods ) for each client by using systematic perturbations in model parameters at a fine - grained level ( i. e., altering each convolutional filter across the layers of the model ) to improve the generalization and security perspective. we evaluated our proposed approach on four benchmark datasets to validate its superiority. we surpassed the state - of - the - art methods in terms of model utility and robustness towards privacy leakage. we have proven the effectiveness of our method by evaluating performance using several quantitative and qualitative results.
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arxiv:2504.02213
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in this paper, we introduce an algorithm for performing spectral clustering efficiently. spectral clustering is a powerful clustering algorithm that suffers from high computational complexity, due to eigen decomposition. in this work, we first build the adjacency matrix of the corresponding graph of the dataset. to build this matrix, we only consider a limited number of points, called landmarks, and compute the similarity of all data points with the landmarks. then, we present a definition of the laplacian matrix of the graph that enable us to perform eigen decomposition efficiently, using a deep autoencoder. the overall complexity of the algorithm for eigen decomposition is $ o ( np ) $, where $ n $ is the number of data points and $ p $ is the number of landmarks. at last, we evaluate the performance of the algorithm in different experiments.
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arxiv:1704.02345
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we introduce a novel methodology that leverages the strength of physics - informed neural networks ( pinns ) to address the counterdiabatic ( cd ) protocol in the optimization of quantum circuits comprised of systems with $ n _ { q } $ qubits. the primary objective is to utilize physics - inspired deep learning techniques to accurately solve the time evolution of the different physical observables within the quantum system. to accomplish this objective, we embed the necessary physical information into an underlying neural network to effectively tackle the problem. in particular, we impose the hermiticity condition on all physical observables and make use of the principle of least action, guaranteeing the acquisition of the most appropriate counterdiabatic terms based on the underlying physics. the proposed approach offers a dependable alternative to address the cd driving problem, free from the constraints typically encountered in previous methodologies relying on classical numerical approximations. our method provides a general framework to obtain optimal results from the physical observables relevant to the problem, including the external parameterization in time known as scheduling function, the gauge potential or operator involving the non - adiabatic terms, as well as the temporal evolution of the energy levels of the system, among others. the main applications of this methodology have been the $ \ mathrm { h _ { 2 } } $ and $ \ mathrm { lih } $ molecules, represented by a 2 - qubit and 4 - qubit systems employing the sto - 3g basis. the presented results demonstrate the successful derivation of a desirable decomposition for the non - adiabatic terms, achieved through a linear combination utilizing pauli operators. this attribute confers significant advantages to its practical implementation within quantum computing algorithms.
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arxiv:2309.04434
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we propose a haptic system for virtual manipulation to provide feedback on the user ' s forearm instead of the fingertips. in addition to visual rendering of the manipulation with virtual fingertips, we employ a device to deliver normal or shear skin - stretch at multiple points near the wrist. to understand how design parameters influence the experience, we investigated the effect of the number and location of sensory feedback on stiffness perception. participants compared stiffness values of virtual objects, while the haptic bracelet provided interaction feedback on the dorsal, ventral, or both sides of the wrist. stiffness discrimination judgments and duration, as well as qualitative results collected verbally, indicate no significant difference in stiffness perception with stimulation at different and multiple locations.
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arxiv:2204.05830
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vibrational and elastic properties of the $ r $ fe $ _ { 4 } $ sb $ _ { 12 } $ skutterudites are investigated by, respectively, temperature $ ( t ) $ dependent extended x - ray absorption fine structure ( exafs ) and pressure $ ( p ) $ dependent x - ray diffraction ( xrd ) experiments. the fe $ k $ - edge exafs experiments of the $ r = $ k, ca and ba materials were performed in the $ t $ - interval $ 6 < t < 300 $ k and xrd experiments of the $ r = $ na, k, ca, sr and ba materials were performed in the $ p $ - interval $ 1 \ text { atm } < p < 16 $ gpa. from exafs, we obtained the correlated debye - waller parameters that were thus analyzed to extract effective spring constants connected with the fe - $ y $ ( where $ y = $ either $ r $, fe or sb ) scattering paths. our findings suggest that in the case of the light cations, $ r = $ k or ca, the $ r $ atoms are relatively weakly coupled to the cage, in a scenario reminiscent to the einstein oscillators. from the xrd experiments, we obtained the bulk modulus $ b _ { 0 } $ for all $ r = $ na, k, ca, sr and ba materials, with values ranging from $ 77 $ gpa ( $ r = $ k ) to $ r = 99 $ gpa ( $ r = $ ba ) as well as the compressibility $ \ beta $ as a function of $ p $. the trend in $ \ beta $ as a function of the $ r $ filler is discussed and it is shown that it does not correlate with simple geometrical considerations but rather with the filler - cage bonding properties.
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arxiv:2203.14821
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is it always necessary to compute tokens from shallow to deep layers in transformers? the continued success of vanilla transformers and their variants suggests an undoubted " yes ". in this work, however, we attempt to break the depth - ordered convention by proposing a novel architecture dubbed mixture - of - modules ( mom ), which is motivated by an intuition that any layer, regardless of its position, can be used to compute a token as long as it possesses the needed processing capabilities. the construction of mom starts from a finite set of modules defined by multi - head attention and feed - forward networks, each distinguished by its unique parameterization. two routers then iteratively select attention modules and feed - forward modules from the set to process a token. the selection dynamically expands the computation graph in the forward pass of the token, culminating in an assembly of modules. we show that mom provides not only a unified framework for transformers and their numerous variants but also a flexible and learnable approach for reducing redundancy in transformer parameterization. we pre - train various moms using openwebtext. empirical results demonstrate that moms, of different parameter counts, consistently outperform vanilla transformers on both glue and xsum benchmarks. more interestingly, with a fixed parameter budget, mom - large enables an over 38 % increase in depth for computation graphs compared to gpt - 2 - large, resulting in absolute gains of 1. 4 on glue and 1 on xsum. on the other hand, mom - large also enables an over 60 % reduction in depth while involving more modules per layer, yielding a 16 % reduction in tflops and a 43 % decrease in memory usage compared to gpt - 2 - large, while maintaining comparable performance.
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arxiv:2407.06677
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as premodern texts are passed down over centuries, errors inevitably accrue. these errors can be challenging to identify, as some have survived undetected for so long precisely because they are so elusive. while prior work has evaluated error detection methods on artificially - generated errors, we introduce the first dataset of real errors in premodern greek, enabling the evaluation of error detection methods on errors that genuinely accumulated at some stage in the centuries - long copying process. to create this dataset, we use metrics derived from bert conditionals to sample 1, 000 words more likely to contain errors, which are then annotated and labeled by a domain expert as errors or not. we then propose and evaluate new error detection methods and find that our discriminator - based detector outperforms all other methods, improving the true positive rate for classifying real errors by 5 %. we additionally observe that scribal errors are more difficult to detect than print or digitization errors. our dataset enables the evaluation of error detection methods on real errors in premodern texts for the first time, providing a benchmark for developing more effective error detection algorithms to assist scholars in restoring premodern works.
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arxiv:2410.11071
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we show that uncertainties in the values of the surface heavy element abundances of the sun are the largest source of the theoretical uncertainty in calculating the p - p, pep, 8b, 13n, 15o, and 17f solar neutrino fluxes. we evaluate for the first time the sensitivity ( partial derivative ) of each solar neutrino flux with respect to the surface abundance of each element. we then calculate the uncertainties in each neutrino flux using ` conservative ( preferred ) ' and ` optimistic ' estimates for the uncertainties in the element abundances. the total conservative ( optimistic ) composition uncertainty in the predicted 8b neutrino flux is 11. 6 % ( 5. 0 % ) when sensitivities to individual element abundances are used. the traditional method that lumps all abundances into a single quantity ( total heavy element to hydrogen ratio, z / x ) yields a larger uncertainty, 20 %. the uncertainties in the carbon, oxygen, neon, silicon, sulphur, and iron abundances all make significant contributions to the uncertainties in calculating solar neutrino fluxes ; the uncertainties of different elements are most important for different neutrino fluxes. the uncertainty in the iron abundance is the largest source of the estimated composition uncertainties of the important 7be and 8b solar neutrinos. carbon is the largest contributor to the uncertainty in the calculation of the p - p, 13n, and 15o neutrino fluxes. however, for all neutrino fluxes, several elements contribute comparable amounts to the total composition uncertainty.
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arxiv:astro-ph/0412096
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a global time - discretized scheme for the navier - stokes equation system in its leray projection form is defined. it is shown that the scheme converges to a bounded global classical solution for smooth data which have polynomial decay at infinity. furthermore, the algorithm proposed is extended to the situation of initial - boundary value problems. algorithms constructed in a different context ( cf. [ 4, 10, 5, 9 ] ) may be used within the proposed scheme in order to compute the solution of leray ' s form of the navier - stokes system. the main idea for global existence is to define a control function dynamically and show explicitly that the scheme which solves a controlled navier - stokes type equation can control the modulus of velocity and the first derivatives of velocity to be bounded. the method described here can be extended to navier - stokes equations on compact manifolds which is done in a subsequent paper.
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arxiv:1004.4589
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in comparison with derrida ' s rem, we investigate the influence of the so - called decoration processes arising in the limiting extremal processes of numerous log - correlated gaussian fields. in particular, we focus on the branching brownian motion and two specific quantities from statistical physics in the vicinity of the critical temperature. the first one is the two - temperature overlap, whose behavior at criticality is smoothened by the decoration process - unlike the one - temperature overlap which is identical - and the second one is the temperature susceptibility, as introduced by sales and bouchaud, which is strictly larger in the presence of decorations and diverges, close to the critical temperature, at the same speed as for the rem but with a different multiplicative constant. we also study some general decorated cases in order to highlight the fact that the bbm has a critical behavior in some sense to be made precise.
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arxiv:2404.02888
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a long - range fifth force coupled to dark matter can induce a coupling to ordinary matter if the dark matter interacts with standard model fields. we consider constraints on such a scenario from both astrophysical observations and laboratory experiments. we also examine the case where the dark matter is a weakly interacting massive particle, and derive relations between the coupling to dark matter and the coupling to ordinary matter for different models. currently, this scenario is most tightly constrained by galactic dynamics, but improvements in eotvos experiments can probe unconstrained regions of parameter space.
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arxiv:0807.4363
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the problem of extinction is the most important issue to be dealt with in the process of obtaining true absolute magnitudes of core - collapse ( including stripped - envelope ) supernovae ( sne ). the plane - parallel model, widely used in the past, was shown not to describe extinction adequately. we try to apply an alternative model which introduces radial dependance of extinction in parent galaxies of supernovae. for calculating extinction in our galaxy we use two different methods and compare the results obtained. our analysis is primarily focused on a chosen sample of stripped - envelope sne ( ib / c ) for which we find intrinsic peak absolute magnitude $ \ mathrm { m } _ { \ mathrm { b } } ^ { 0 } = - 17. 80 \ pm 0. 43 $.
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arxiv:0711.4241
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deep neural networks ( dnns ) have been widely used to solve partial differential equations ( pdes ) in recent years. in this work, a novel deep learning - based framework named particle weak - form based neural networks ( particlewnn ) is developed for solving pdes in the weak form. in this framework, the trial space is defined as the space of dnns, while the test space consists of functions compactly supported in extremely small regions, centered around particles. to facilitate the training of neural networks, an r - adaptive strategy is designed to adaptively modify the radius of regions during training. the particlewnn inherits the benefits of weak / variational formulation, requiring less regularity of the solution and a small number of quadrature points for computing integrals. additionally, due to the special construction of the test functions, particlewnn enables parallel implementation and integral calculations only in extremely small regions. this framework is particularly desirable for solving problems with high - dimensional and complex domains. the efficiency and accuracy of particlewnn are demonstrated through several numerical examples, showcasing its superiority over state - of - the - art methods. the source code for the numerical examples presented in this paper is available at https : / / github. com / yaohua32 / particlewnn.
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arxiv:2305.12433
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we study a generic family of two - player continuous - time nonzero - sum stopping games modeling a war of attrition with symmetric information and stochastic payoffs that depend on an homogeneous linear diffusion. we first show that any markovian mixed strategy for player $ i $ can be represented by a pair $ ( \ mu ^ i, s ^ i ) $, where $ \ mu ^ i $ is a measure over the state space representing player $ i $ ' s stopping intensity, and $ s ^ i $ is a subset of the state space over which player $ i $ stops with probability $ 1 $. we then prove that, if players are asymmetric, then, in all mixed - strategy markov - perfect equilibria, the measures $ \ mu ^ i $ have to be essentially discrete, and we characterize any such equilibrium through a variational system satisfied by the players ' equilibrium value functions. this result contrasts with the literature, which focuses on pure - strategy equilibria, or, in the case of symmetric players, on mixed - strategy equilibria with absolutely continuous stopping intensities. we illustrate this result by revisiting the model of exit in a duopoly under uncertainty, and exhibit a mixed - strategy equilibrium in which attrition takes place on the equilibrium path though firms have different liquidation values.
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arxiv:2210.08848
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the latency reduction between the discovery of vulnerabilities, the build - up and dissemination of cyber - attacks has put significant pressure on cybersecurity professionals. for that, security researchers have increasingly resorted to collective action in order to reduce the time needed to characterize and tame outstanding threats. here, we investigate how joining and contributions dynamics on misp, an open source threat intelligence sharing platform, influence the time needed to collectively complete threat descriptions. we find that performance, defined as the capacity to characterize quickly a threat event, is influenced by ( i ) its own complexity ( negatively ), by ( ii ) collective action ( positively ), and by ( iii ) learning, information integration and modularity ( positively ). our results inform on how collective action can be organized at scale and in a modular way to overcome a large number of time - critical tasks, such as cybersecurity threats.
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arxiv:2206.15055
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using a compilation of measurements of the stellar mass density as a function of redshift we can infer the cosmic star formation history. for z < 0. 7 there is good agreement between the two star formation histories. at higher redshifts the instantaneous indicators suggest star formation rates larger than that implied by the evolution of the stellar mass density. this discrepancy peaks at z = 3 where instantaneous indicators suggest a star formation rate around 0. 6 dex higher than those of the best fit to the stellar mass history. we discuss a variety of explanations for this inconsistency, such as inaccurate dust extinction corrections, incorrect measurements of stellar masses and a possible evolution of the stellar initial mass function.
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arxiv:0803.4024
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let $ g $ be a locally compact amenable group, $ tlim ( g ) $ the topological left - invariant means on $ g $, and $ tlim _ 0 ( g ) $ the limit points of folner - nets. i show that $ tlim _ 0 ( g ) = tlim ( g ) $ unless $ g $ is $ \ sigma $ - compact non - unimodular, in which case $ tlim _ 0 ( g ) \ neq tlim ( g ) $. this improves a 1970 result of chou and a 2009 result of hindman and strauss. i consider the analogous problem for the non - topological left - invariant means, and give a short construction of a net converging to invariance " weakly but not strongly, " simplifying the proof of a 2001 result of rosenblatt and willis.
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arxiv:2003.00251
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we perform a numerical simulation of the dynamics of quantized vortices produced by coflow in a square channel using the vortex filament model. unlike the situation in thermal counterflow, where the superfluid velocity $ v _ { \ rm s } $ and normal - fluid velocity $ v _ { \ rm n } $ flow in opposite directions, in coflow, $ v _ { \ rm s } $ and $ v _ { \ rm n } $ flow in the same direction. quantum turbulence in thermal counterflow has been long studied theoretically and experimentally, and its various features have been revealed. in recent years, an experiment on quantum turbulence in coflow has been performed to observe different features of thermal counterflow. by supposing that $ v _ { \ rm s } $ is uniform and $ v _ { \ rm n } $ takes the hagen - poiseuille profile, which is different from the experiment where $ v _ { \ rm n } $ is thought to be turbulent, we calculate the coflow turbulence. vortices preferentially accumulate on the surface of a cylinder for $ v _ { \ rm s } \ simeq v _ { \ rm n } $ by mutual friction ; namely, the coflow turbulence has an attractor. how strongly the vortices are attracted depends on the temperature and velocity. the length of the vortices increases as the vortices protruding from the cylindrical attractor continue to wrap around it. as the vortices become dense on the attractor, they spread toward its interior by their repulsive interaction. then, the superfluid velocity profile induced by the vortices gradually mimics the normal - fluid velocity profile. this is an indication of velocity matching, which is an important feature of coflow turbulence.
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arxiv:1602.08252
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the heavy - fermion system $ \ mathrm { ute _ 2 } $ is a candidate for spin - triplet superconductivity, which is of considerable interest to quantum engineering. among the outstanding issues is the nature of the pairing state. a recent surprising discovery is the observation of a resonance in the spin excitation spectrum at an antiferromagnetic wavevector [ c. duan { \ it et al. }, nature \ textbf { 600 }, 636 ( 2021 ) ], which stands in apparent contrast to the ferromagnetic nature of the interactions expected in this system. we show how the puzzle can be resolved by a multiorbital spin - triplet pairing constructed from local degrees of freedom. because it does not commute with the kinetic part of the hamiltonian, the pairing contains both intra - and inter - band terms in the band basis. we demonstrate that the intraband pairing component naturally yields a spin resonance at the antiferromagnetic wavevector. our work illustrates how orbital degrees of freedom can enrich the nature and properties of spin - triplet superconductivity of strongly - correlated quantum materials.
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arxiv:2112.14750
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the optical trapping of polymeric nanofibers and the characterization of the rotational dynamics are reported. a strategy to apply a torque to a polymer nanofiber, by tilting the trapped fibers using a symmetrical linear polarized gaussian beam is demonstrated. rotation frequencies up to 10 hz are measured, depending on the trapping power, the fiber length and the tilt angle. a comparison of the experimental rotation frequencies in the different trapping configurations with calculations based on optical trapping and rotation of linear nanostructures through a t - matrix formalism, accurately reproduce the measured data, providing a comprehensive description of the trapping and rotation dynamics.
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arxiv:0907.2111
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depth completion using lightweight time - of - flight ( tof ) depth sensors is attractive due to their low cost. however, lightweight tof sensors usually have a limited field of view ( fov ) compared with cameras. thus, only pixels in the zone area of the image can be associated with depth signals. previous methods fail to propagate depth features from the zone area to the outside - zone area effectively, thus suffering from degraded depth completion performance outside the zone. to this end, this paper proposes the cfpnet to achieve cross - zone feature propagation from the zone area to the outside - zone area with two novel modules. the first is a direct - attention - based propagation module ( dapm ), which enforces direct cross - zone feature acquisition. the second is a large - kernel - based propagation module ( lkpm ), which realizes cross - zone feature propagation by utilizing convolution layers with kernel sizes up to 31. cfpnet achieves state - of - the - art ( sota ) depth completion performance by combining these two modules properly, as verified by extensive experimental results on the zju - l5 dataset. the code is available at https : / / github. com / denyingmxd / cfpnet.
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arxiv:2411.04480
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quantum localization of classical mechanics within the brst - bfv and bv ( or field - antifield ) quantization methods are studied. it is shown that a special choice of gauge fixing functions ( or brst - bfv charge ) together with the unitary limit leads to hamiltonian localization in the path integral of the brst - bfv formalism. in turn, we find that a special choice of gauge fixing functions being proportional to extremals of an initial non - degenerate classical action together with a very special solution of the classical master equation result in lagrangian localization in the partition function of the bv formalism.
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arxiv:1603.03990
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we discuss a correlated two - photon imaging apparatus that is capable of producing images that are free of the effects of odd - order aberration introduced by the optical system. we show that both quantum - entangled and classically correlated light sources are capable of producing the desired spatial - aberration cancelation.
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arxiv:1008.0801
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the problem of maximizing precision at the top of a ranked list, often dubbed precision @ k ( prec @ k ), finds relevance in myriad learning applications such as ranking, multi - label classification, and learning with severe label imbalance. however, despite its popularity, there exist significant gaps in our understanding of this problem and its associated performance measure. the most notable of these is the lack of a convex upper bounding surrogate for prec @ k. we also lack scalable perceptron and stochastic gradient descent algorithms for optimizing this performance measure. in this paper we make key contributions in these directions. at the heart of our results is a family of truly upper bounding surrogates for prec @ k. these surrogates are motivated in a principled manner and enjoy attractive properties such as consistency to prec @ k under various natural margin / noise conditions. these surrogates are then used to design a class of novel perceptron algorithms for optimizing prec @ k with provable mistake bounds. we also devise scalable stochastic gradient descent style methods for this problem with provable convergence bounds. our proofs rely on novel uniform convergence bounds which require an in - depth analysis of the structural properties of prec @ k and its surrogates. we conclude with experimental results comparing our algorithms with state - of - the - art cutting plane and stochastic gradient algorithms for maximizing prec @ k.
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arxiv:1505.06813
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we introduce the concept of numerical gaussian processes, which we define as gaussian processes with covariance functions resulting from temporal discretization of time - dependent partial differential equations. numerical gaussian processes, by construction, are designed to deal with cases where : ( 1 ) all we observe are noisy data on black - box initial conditions, and ( 2 ) we are interested in quantifying the uncertainty associated with such noisy data in our solutions to time - dependent partial differential equations. our method circumvents the need for spatial discretization of the differential operators by proper placement of gaussian process priors. this is an attempt to construct structured and data - efficient learning machines, which are explicitly informed by the underlying physics that possibly generated the observed data. the effectiveness of the proposed approach is demonstrated through several benchmark problems involving linear and nonlinear time - dependent operators. in all examples, we are able to recover accurate approximations of the latent solutions, and consistently propagate uncertainty, even in cases involving very long time integration.
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arxiv:1703.10230
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semantic role theory is a widely used approach for event representation. yet, there are multiple indications that semantic role paradigm is necessary but not sufficient to cover all elements of event structure. we conducted an analysis of semantic role representation for events to provide an empirical evidence of insufficiency. the consequence of that is a hybrid role - scalar approach. the results are considered as preliminary in investigation of semantic roles coverage for event representation.
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arxiv:1810.03879
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we tackle the problem of building adaptive estimation procedures for ill - posed inverse problems. for general regularization methods depending on tuning parameters, we construct a penalized method that selects the optimal smoothing sequence without prior knowledge of the regularity of the function to be estimated. we provide for such estimators oracle inequalities and optimal rates of convergence. this penalized approach is applied to tikhonov regularization and to regularization by projection.
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arxiv:0807.4859
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we present spectroscopic observations with the 3. 6m eso telescope of two emission - line galaxies, j2104 - 0035 and j0113 + 0052, selected from the data release 4 ( dr4 ) of the sloan digital sky survey ( sdss ). from our data we determine the oxygen abundance of these systems to be respectively 12 + logo / h = 7. 26 + / - 0. 03 and 7. 17 + / - 0. 09, making them the two most metal - deficient galaxies found thus far in the sdss and placing them among the five most metal - deficient emission - line galaxies ever discovered. their oxygen abundances are close to those of the two most metal - deficient emission - line galaxies known, sbs0335 - 052w with 12 + logo / h = 7. 12 + / - 0. 03 and i zw 18 with 12 + logo / h = 7. 17 + / - 0. 01.
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arxiv:astro-ph/0604234
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a light beam carrying orbital angular momentum ( oam ) is characterized by a helical phase - front that winds around the center of the beam. these beams have unique properties that have found numerous applications. in the field of data transmission, they represent a degree of freedom that could potentially increase capacity by a factor of several distinct oam modes. while an efficient method for ( de ) composing beams based on their oam exists for free - space optics, a device capable of performing this ( de ) composition in an integrated, compact fiber application without the use of external active optical elements and for multiple oam modes simultaneously has not been reported. in this study, a waveguide structure is presented that can serve as a broadband oam ( de ) multiplexer. the structure design is based on the adiabatic principle used in photonic lanterns for highly efficient conversion of spatially separated single modes into eigenmodes of a few - mode fiber. in addition, an artificial magnetic field is introduced by twisting the structure during the adiabatic evolution, which removes the degeneracy between modes having the same absolute oam. this structure can simplify, stabilize, and miniaturize the creation or decomposition of oam beams, making them useful for various applications.
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arxiv:2310.08489
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we study the problem of exponential mixing and large deviations for discrete - time markov processes associated with a class of random dynamical systems. under some dissipativity and regularisation hypotheses for the underlying deterministic dynamics and a non - degeneracy condition for the driving random force, we discuss the existence and uniqueness of a stationary measure and its exponential stability in the kantorovich - wasserstein metric. we next turn to the large deviation principle and establish its validity for the occupation measures of the markov processes in question. the obtained results extend those established earlier for the case of the bounded noise and can be applied to the 2d navier - stokes system in a bounded domain and to the complex ginzburg - landau equation.
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arxiv:1410.6188
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the su ( 4 ) polyakov linear sigma model ( plsm ) is extended towards characterizing the chiral condensates, $ \ sigma _ l $, $ \ sigma _ s $ and $ \ sigma _ c $ of light, strange and charm quarks, respectively and the deconfinement order - parameters $ \ phi $ and $ \ bar { \ phi } $ at finite temperatures and densities ( chemical potentials ). the plsm is considered to study the qcd equation of state in the presence of the chiral condensate of charm for different finite chemical potentials. the plsm results are in a good agreement with the recent lattice qcd simulations. we conclude that, the charm condensate is likely not affected by the qcd phase - transition, where the corresponding critical temperature is greater than that of the light and strange quark condensates.
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arxiv:1801.10234
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the detection of olivine on vesta is interesting because it may provide critical insights into planetary differentiation early in our solar system ' s history. ground - based and hubble space telescope ( hst ) observations of asteroid ( 4 ) vesta have suggested the presence of olivine on the surface. these observations were reinforced by the discovery of olivine - rich hed meteorites from vesta in recent years. however, analysis of data from nasa ' s dawn spacecraft has shown that this olivine - bearing unit is actually impact melt in the ejecta of oppia crater. the lack of widespread mantle olivine, exposed during the formation of the 19 km deep rheasilvia basin on vesta ' s south pole, further complicated this picture. ammannito et al., ( 2013a ) reported the discovery of local scale olivine - rich units in the form of excavated material from the mantle using the visible and infrared spectrometer ( vir ) on dawn. here we explore alternative sources for the olivine in the northern hemisphere of vesta by reanalyzing the data from the vir instrument using laboratory spectral measurements of meteorites. we suggest that these olivine exposures could be explained by the delivery of olivine - rich exogenic material. based on our spectral band parameters analysis, the lack of correlation between the location of these olivine - rich terrains and possible mantle - excavating events, and supported by observations of hed meteorites, we propose that a probable source for olivine seen in the northern hemisphere are remnants of impactors made of olivine - rich meteorites. best match suggests these units are hed material mixed with either ordinary chondrites, or with some olivine - dominated meteorites such as r - chondrites.
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arxiv:1502.03189
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we report a search for fluctuations of the sky brightness toward the north ecliptic pole ( nep ) with the japanese infrared astronomical satellite akari, at 2. 4, 3. 2, and 4. 1 \ mum. we obtained circular maps with 100 diameter field of view which clearly show a spatial structure on scale of a few hundred arcsec. a power spectrum analysis shows that there is a significant excess fluctuation at angular scales larger than 10000 that can ' t be explained by zodiacal light, diffuse galactic light, shot noise of faint galaxies or clustering of low redshift galaxies. these results are consistent with observations at 3. 6 and 4. 5 \ mum by nasa ' s spitzer space telescope. the fluctuating component observed at large angular scales has a blue stellar spectrum which is similar to that of the spectrum of the excess isotropic emission observed with irts. a significant spatial correlation between wavelength bands was found, and the slopes of the linear correlations is consistent with the spectrum of the excess fluctuation. these findings indicate that the detected fluctuation could be attributed to the first stars of the universe, i. e. pop. iii stars. the observed fluctuation provides an important constraints on the era of the first stars.
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arxiv:1010.0491
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electronic quantum effects in disordered conductors are controlled by the dephasing rate of conduction electrons. this rate is expected to vanish with the temperature. we consider the very intriguing recently reported apparent saturation of this dephasing rate in several systems at very low temperatures. we show that the ` ` standard model ' ' of a conductor with static defects can { \ em not } have such an effect. however, allowing some dynamics of the defects may produce it.
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arxiv:cond-mat/9903017
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recent lattice computations showed how the approach dubbed " refined gribov - zwanziger scenario " is in very good agreement with data and the gluon propagator fits them very well. this propagator can be described as a finite sum of yukawa propagators and can be obtained introducing some condensates representing the contribution of the vacuum of yang - mills theory. the values of the condensates are arbitrary and are obtained through lattice data. this kind of structure of the propagator is in agreement with the one we obtained using a different analytical approach but with the substantial difference that here all the physical parameters are properly fixed. we show that our approach can properly fix all the values of the condensates in the refined gribov - zwanziger scenario giving a complete validation to both techniques. this will provide an interesting view to the gluon propagator and a set of values to be experimentally determined.
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arxiv:1202.4105
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the lucas & kanade ( lk ) algorithm is the method of choice for efficient dense image and object alignment. the approach is efficient as it attempts to model the connection between appearance and geometric displacement through a linear relationship that assumes independence across pixel coordinates. a drawback of the approach, however, is its generative nature. specifically, its performance is tightly coupled with how well the linear model can synthesize appearance from geometric displacement, even though the alignment task itself is associated with the inverse problem. in this paper, we present a new approach, referred to as the conditional lk algorithm, which : ( i ) directly learns linear models that predict geometric displacement as a function of appearance, and ( ii ) employs a novel strategy for ensuring that the generative pixel independence assumption can still be taken advantage of. we demonstrate that our approach exhibits superior performance to classical generative forms of the lk algorithm. furthermore, we demonstrate its comparable performance to state - of - the - art methods such as the supervised descent method with substantially less training examples, as well as the unique ability to " swap " geometric warp functions without having to retrain from scratch. finally, from a theoretical perspective, our approach hints at possible redundancies that exist in current state - of - the - art methods for alignment that could be leveraged in vision systems of the future.
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arxiv:1603.08597
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it has been shown that many of the phenomena related to the formation of " tails " in the low - concentration region of ion - implanted impurity distribution are due to the anomalous diffusion of nonequilibrium impurity interstitials. these phenomena include boron implantation in preamorphized silicon, a " hot " implantation of indium ions, annealing of ion - implanted layers et cetera. in particular, to verify this microscopic mechanism, a simulation of boron redistribution during low - temperature annealing of ion - implanted layers has been carried out under different conditions of transient enhanced diffusion suppression. due to the good agreement with the experimental data, the values of the average migration length of nonequilibrium impurity interstitials have been obtained. it has been shown that for boron implanted into a silicon layer preamorphized by germanium ions the average migration length of impurity interstitials at the annealing temperature of 800 celsius degrees be reduced from 11 nm to approximately 6 nm due to additional implantation of nitrogen. the further shortening of the average migration length is observed if the processing temperature is reduced to 750 celsius degrees. it is also found that for implantation of bf2 ions into silicon crystal, the value of the average migration length of boron interstitials is equal to 7. 2 nm for thermal treatment at a temperature of 800 celsius degrees.
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arxiv:1108.4154
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static self - consistent methods usually allow to determine the most probable fission fragments mass asymmetry. we have applied random neck rupture mechanism to the nuclei in the configuration at the end of fission paths. fission fragment mass distributions have been deduced from the pre - scission nuclear density distribution obtained from the self - consistent calculations. potential energy surfaces as well as nuclear shapes have been calculated in the fully microscopic theory, namely the constrained hartree - fock - bogolubov model with the effective gogny d1s density - dependent interaction. the method has been applied for analysis of fission of fm - 256, 258, cf - 252 and hg - 180 and compared with the experimental data.
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arxiv:1502.05564
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this paper aims at enlarging the problem of neural architecture search ( nas ) from single - path and multi - path search to automated mixed - path search. in particular, we model the nas problem as a sparse supernet using a new continuous architecture representation with a mixture of sparsity constraints. the sparse supernet enables us to automatically achieve sparsely - mixed paths upon a compact set of nodes. to optimize the proposed sparse supernet, we exploit a hierarchical accelerated proximal gradient algorithm within a bi - level optimization framework. extensive experiments on convolutional neural network and recurrent neural network search demonstrate that the proposed method is capable of searching for compact, general and powerful neural architectures.
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arxiv:2007.16112
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the nontrivial band topology can influence the hofstadter spectrum. we investigate the hofstadter spectrum for various models of chern insulators under a rational flux $ \ frac { \ phi _ { 0 } } { q } $, here $ \ phi _ { 0 } = \ frac { h } { e } $ and $ q $ being an integer. we find two major features. first, the number of splitting subbands is $ | q - c | $ with chern number $ c $. second, the anomalous open - orbit subbands with chern numbers $ q - 1 $ and $ - q - 1 $ emerge, which are beyond the parameter window $ ( - q / 2, q / 2 ) $ of the diophantine equation studied by thouless - kohmoto - nightingale - den nijs [ phys. rev. lett. \ textbf { 49 }, 405 ( 1982 ) ]. these two findings are explained by semiclassical dynamics. we propose that the number of splitting subbands can be utilized to determine chern number in cold atom systems, and the open - orbit subbands can provide routes to study exotic features beyond the landau level physics.
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arxiv:2303.14794
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in this paper, we first propose the concept of strong idempotent codec based on idempotent codec. the idempotence of codec refers to the stability of codec to re - compression. similarly, we define the strong idempotence of codec as the stability of codec to multiple quality re - compression, which is an important feature of codec in the context of cloud transcoding. we provide a detailed example of strong idempotent codec with known source distribution. further, we formalize a testing protocol to evaluate the strong idempotence of image codec. and finally, we evaluate the strong idempotence of current image codecs, including traditional codec and recent neural codec. experimental results show that current image codecs are not stable to multi - round re - compression with different qualities, even if they are close to idempotent.
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arxiv:2304.08269
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skew - orthogonal polynomials ( sops ) arise in the study of the n - point distribution function for orthogonal and symplectic random matrix ensembles. motivated by the average of characteristic polynomials of the bures random matrix ensemble studied in [ 22 ], we propose the concept of partial - skew - orthogonal polynomials ( psops ) as a modification of the sops, and then the psops with a variety of special skew - symmetric kernels and weight functions are addressed. by considering appropriate deformations of the weight functions, we derive nine integrable lattices in different dimensions. as a consequence, the tau - functions for these systems are shown to be expressed in terms of pfaffians and the wave vectors psops. in fact, the tau - functions also admit the representations of multiple integrals. among these integrable lattices, some of them are known, while the others are novel to the best of our knowledge. in particular, one integrable lattice is related to the partition function of the bures random matrix ensemble. besides, we derive a discrete integrable lattice, which can be used to compute certain vector pad \ ' e approximants. this yields the first example regarding the connection between integrable lattices and vector pad \ ' e approximants, for which hietarinta, joshi and nijhoff pointed out that " this field remains largely to be explored. " in the recent monograph [ 27, section 4. 4 ].
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arxiv:1712.06382
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we study a multi - player one - round game termed stackelberg network pricing game, in which a leader can set prices for a subset of $ m $ priceable edges in a graph. the other edges have a fixed cost. based on the leader ' s decision one or more followers optimize a polynomial - time solvable combinatorial minimization problem and choose a minimum cost solution satisfying their requirements based on the fixed costs and the leader ' s prices. the leader receives as revenue the total amount of prices paid by the followers for priceable edges in their solutions, and the problem is to find revenue maximizing prices. our model extends several known pricing problems, including single - minded and unit - demand pricing, as well as stackelberg pricing for certain follower problems like shortest path or minimum spanning tree. our first main result is a tight analysis of a single - price algorithm for the single follower game, which provides a $ ( 1 + \ epsilon ) \ log m $ - approximation for any $ \ epsilon > 0 $. this can be extended to provide a $ ( 1 + \ epsilon ) ( \ log k + \ log m ) $ - approximation for the general problem and $ k $ followers. the latter result is essentially best possible, as the problem is shown to be hard to approximate within $ \ mathcal { o ( \ log ^ \ epsilon k + \ log ^ \ epsilon m ) $. if followers have demands, the single - price algorithm provides a $ ( 1 + \ epsilon ) m ^ 2 $ - approximation, and the problem is hard to approximate within $ \ mathcal { o ( m ^ \ epsilon ) $ for some $ \ epsilon > 0 $. our second main result is a polynomial time algorithm for revenue maximization in the special case of stackelberg bipartite vertex cover, which is based on non - trivial max - flow and lp - duality techniques. our results can be extended to provide constant - factor approximations for any constant number of followers.
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arxiv:0802.2841
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we consider a counting problem in the setting of hyperbolic dynamics. let $ \ phi _ t : \ lambda \ to \ lambda $ be a weak mixing hyperbolic flow. we count the proportion of prime periodic orbits of $ \ phi _ t $, with length less than $ t $, that satisfy an averaging condition related to a h \ " older continuous function $ f : \ lambda \ to \ mathbb { r } $. we show, assuming an approximability condition on $ \ phi $, that as $ t \ to \ infty $, we obtain a central limit theorem.
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arxiv:1805.05692
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we demonstrate the batyrev - manin conjecture for the number of points of bounded height on hypersurfaces of some toric varieties whose rank of the picard group is 2. the method used is inspired by the one developed by schindler for the study the case of hypersurfaces of biprojective spaces. this method is based on the hardy - littlewood circle method. the constant obtained in the final asymptotic formula is the one conjectured by peyre. - - - - - nous d \ ' emontrons la conjecture de batyrev - manin pour le nombre de points de hauteur born \ ' ee sur les hypersurfaces de certaines vari \ ' et \ ' es toriques dont le rang du groupe de picard est 2. la m \ ' ethode utilis \ ' ee est inspir \ ' ee de celle d \ ' evelopp \ ' ee par schindler pour l ' \ ' etude du cas des hypersurfaces des espaces biprojectifs. cette m \ ' ethode est bas \ ' ee sur la m \ ' ethode du cercle de hardy - littlewood. la constante obtenue dans la formule asymptotique finale est celle conjectur \ ' ee par peyre.
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arxiv:1411.7249
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theoretically, stars have been formed from the collapse of cores in the molecular clouds. historically, the core had been assumed as an singular isothermal sphere ( sis ), and the collapse had been investigated by a self - similar manner. this is while the rotation and magnetic field lead to non - symmetric collapse so that a spheroid shape may be occurred. here, the resultant of the centrifugal force and magnetic field gradient is assumed to be in the normal direction of the rotational axis, and its components are supposed to be a fraction $ \ beta $ of the local gravitational force. in this research, a collapsing sis core is considered to find the importance of the parameter $ \ beta $ for oblateness of the mass shells which are above the head of the expansion wave. we apply the adomian decomposition method to solve the system of nonlinear partial differential equations because the collapse does not occur in a spherical symmetry with self - similar behavior. in this way, we obtain a semi - analytical relation for the mass infall rate $ \ dot { m } $ of the shells at the envelope. near the rotational axis, the $ \ dot { m } $ decreases with increasing of the non - dimensional radius $ \ xi $, while a direct relation is observed between $ \ dot { m } $ and $ \ xi $ in the equatorial regions. also, the values of $ \ dot { m } $ in the polar regions are greater than the equatorial values, and this difference is more often at smaller values of $ \ xi $. overall, the results show that before reaching the head of expansion wave, the visible shape of the molecular cloud cores can evolve to oblate spheroids. the ratio of major to minor axes of oblate cores increases with increasing the parameter $ \ beta $, and its value can approach to the apparently observed elongated shapes of cores in the maps of molecular clouds such as taurus and perseus.
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arxiv:1007.0625
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we propose a direct numerical method for the solution of an optimal control problem governed by a two - side space - fractional diffusion equation. the presented method contains two main steps. in the first step, the space variable is discretized by using the jacobi - gauss pseudospectral discretization and, in this way, the original problem is transformed into a classical integer - order optimal control problem. the main challenge, which we faced in this step, is to derive the left and right fractional differentiation matrices. in this respect, novel techniques for derivation of these matrices are presented. in the second step, the legendre - gauss - radau pseudospectral method is employed. with these two steps, the original problem is converted into a convex quadratic optimization problem, which can be solved efficiently by available methods. our approach can be easily implemented and extended to cover fractional optimal control problems with state constraints. five test examples are provided to demonstrate the efficiency and validity of the presented method. the results show that our method reaches the solutions with good accuracy and a low cpu time.
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arxiv:1810.05876
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we discuss the production of 26al and 60fe in two massive star models, namely a 25 and a 80 msun, of initial solar metallicity.
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arxiv:astro-ph/0411441
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we study the root of unity degeneration of cluster algebras and quantum dilogarithm identities. we prove identities for the cyclic dilogarithm associated with a mutation sequence of a quiver, and as a consequence new identities for the non - compact quantum dilogarithm at $ b = 1 $.
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arxiv:1412.5777
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in this paper, we propose a novel model for time series prediction in which difference - attention lstm model and error - correction lstm model are respectively employed and combined in a cascade way. while difference - attention lstm model introduces a difference feature to perform attention in traditional lstm to focus on the obvious changes in time series. error - correction lstm model refines the prediction error of difference - attention lstm model to further improve the prediction accuracy. finally, we design a training strategy to jointly train the both models simultaneously. with additional difference features and new principle learning framework, our model can improve the prediction accuracy in time series. experiments on various time series are conducted to demonstrate the effectiveness of our method.
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arxiv:2003.13616
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7th century ce. the birth and expansion of islam during the 7th century was quickly followed by its hellenization. knowledge of greek conceptions of the world was preserved and absorbed into islamic theology, law, culture, and commerce, which were aided by the translations of traditional greek texts and some syriac intermediary sources into arabic during the 8th – 9th century. = = = = education and scholarly pursuits = = = = madrasas were centers for many different religious and scientific studies and were the culmination of different institutions such as mosques based around religious studies, housing for out - of - town visitors, and finally educational institutions focused on the natural sciences. unlike western universities, students at a madrasa would learn from one specific teacher, who would issue a certificate at the completion of their studies called an ijazah. an ijazah differs from a western university degree in many ways one being that it is issued by a single person rather than an institution, and another being that it is not an individual degree declaring adequate knowledge over broad subjects, but rather a license to teach and pass on a very specific set of texts. women were also allowed to attend madrasas, as both students and teachers, something not seen in high western education until the 1800s. madrasas were more than just academic centers. the suleymaniye mosque, for example, was one of the earliest and most well - known madrasas, which was built by suleiman the magnificent in the 16th century. the suleymaniye mosque was home to a hospital and medical college, a kitchen, and children ' s school, as well as serving as a temporary home for travelers. higher education at a madrasa ( or college ) was focused on islamic law and religious science and students had to engage in self - study for everything else. and despite the occasional theological backlash, many islamic scholars of science were able to conduct their work in relatively tolerant urban centers ( e. g., baghdad and cairo ) and were protected by powerful patrons. they could also travel freely and exchange ideas as there were no political barriers within the unified islamic state. islamic science during this time was primarily focused on the correction, extension, articulation, and application of greek ideas to new problems. = = = = advancements in mathematics = = = = most of the achievements by islamic scholars during this period were in mathematics. arabic mathematics was a direct descendant of greek and indian mathematics. for instance, what is now known as arabic numerals originally came from india, but muslim mathematicians made several
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https://en.wikipedia.org/wiki/History_of_science
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quantum many - body systems ( qmbs ) are some of the most challenging physical systems to simulate numerically. methods involving approximations for tensor network ( tn ) contractions have proven to be viable alternatives to algorithms such as quantum monte carlo or simulated annealing. however, these methods are cumbersome, difficult to implement, and often have significant limitations in their accuracy and efficiency when considering systems in more than one dimension. in this paper, we explore the exact computation of tn contractions on two - dimensional geometries and present a heuristic improvement of tn contraction that reduces the computing time, the amount of memory, and the communication time. we run our algorithm for the ising model using memory optimized x1. 32x large instances on amazon web services ( aws ) elastic compute cloud ( ec2 ). our results show that cloud computing is a viable alternative to supercomputers for this class of scientific applications.
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arxiv:1908.08553
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- identify as hackers. many advocate using the more recent and nuanced alternate terms when describing criminals and others who negatively take advantage of security flaws in software and hardware. others prefer to follow common popular usage, arguing that the positive form is confusing and unlikely to become widespread in the general public. a minority still use the term in both senses despite the controversy, leaving context to clarify ( or leave ambiguous ) which meaning is intended. however, because the positive definition of hacker was widely used as the predominant form for many years before the negative definition was popularized, " hacker " can therefore be seen as a shibboleth, identifying those who use the technically oriented sense ( as opposed to the exclusively intrusion - oriented sense ) as members of the computing community. on the other hand, due to the variety of industries software designers may find themselves in, many prefer not to be referred to as hackers because the word holds a negative denotation in many of those industries. a possible middle ground position has been suggested, based on the observation that " hacking " describes a collection of skills and tools which are used by hackers of both descriptions for differing reasons. the analogy is made to locksmithing, specifically picking locks, which is a skill which can be used for good or evil. the primary weakness of this analogy is the inclusion of script kiddies in the popular usage of " hacker ", despite their lack of an underlying skill and knowledge base. = = see also = = script kiddie, an unskilled computer security attacker hacktivism, conducting cyber attacks on a business or organisation in order to bring social change = = references = = = = further reading = = = = = computer security = = = = = = free software / open source = = = = = external links = = hacking at wikibooks the dictionary definition of hacker at wiktionary media related to hackers at wikimedia commons
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https://en.wikipedia.org/wiki/Hacker
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we propose a novel personalized concept for the optimal treatment selection for a situation where the response is a multivariate vector, that could contain right - censored variables such as survival time. the proposed method can be applied with any number of treatments and outcome variables, under a broad set of models. following a working semiparametric single index model that relates covariates and responses, we first define a patient - specific composite score, constructed from individual covariates. we then estimate conditional means of each response, given the patient score, correspond to each treatment, using a nonparametric smooth estimator. next, a rank aggregation technique is applied to estimate an ordering of treatments based on ranked lists of treatment performance measures given by conditional means. we handle the right - censored data by incorporating the inverse probability of censoring weighting to the corresponding estimators. an empirical study illustrates the performance of the proposed method in finite sample problems. to show the applicability of the proposed procedure for real data, we also present a data analysis using hiv clinical trial data, that contained a right - censored survival event as one of the endpoints.
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arxiv:2209.15068
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we report on the multi - wavelength observations of pks 1510 - 089 ( a flat spectrum radio quasar at z = 0. 361 ) during its high activity period between 2008 september and 2009 june. during this 11 months period, the source was characterized by a complex variability at optical, uv and gamma - ray bands, on time scales down to 6 - 12 hours. the brightest gamma - ray isotropic luminosity, recorded on 2009 march 26, was ~ 2x10 ^ 48erg s ^ - 1. the spectrum in the fermi - lat energy range shows a mild curvature well described by a log - parabolic law, and can be understood as due to the klein - nishina effect. the gamma - ray flux has a complex correlation with the other wavelengths. there is no correlation at all with the x - ray band, a weak correlation with the uv, and a significant correlation with the optical flux. the gamma - ray flux seems to lead the optical one by about 13 days. from the uv photometry we estimated a black hole mass of ~ 5. 4x10 ^ 8 solar masses, and an accretion rate of ~ 0. 5 solar masses / year. although the power in the thermal and non - thermal outputs is smaller compared to the very luminous and distant flat spectrum radio quasars, pks 1510 - 089 exhibits a quite large compton dominance and a prominent big blue bump ( bbb ) as observed in the most powerful gamma - ray quasars. the bbb was still prominent during the historical maximum optical state in 2009 may, but the optical / uv spectral index was softer than in the quiescent state. this seems to indicate that the bbb was not completely dominated by the synchrotron emission during the highest optical state. we model the broadband spectrum assuming a leptonic scenario in which the inverse compton emission is dominated by the scattering of soft photons produced externally to the jet. the resulting model - dependent jet energetic content is compatible with the accretion disk powering the jet, with a total efficiency within the kerr black hole limit.
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arxiv:1007.1237
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mana is a measure of the amount of non - clifford resources required to create a state ; the mana of a mixed state on $ \ ell $ qudits bounded by $ \ le \ frac 1 2 ( \ ell \ ln d - s _ 2 ) $ ; $ s _ 2 $ the state ' s second renyi entropy. we compute the mana of haar - random pure and mixed states and find that the mana is nearly logarithmic in hilbert space dimension : that is, extensive in number of qudits and logarithmic in qudit dimension. in particular, the average mana of states with less - than - maximal entropy falls short of that maximum by $ \ ln \ pi / 2 $. we then connect this result to recent work on near - clifford approximate $ t $ - designs ; in doing so we point out that mana is a useful measure of non - clifford resources precisely because it is not differentiable.
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arxiv:2011.13937
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video colorization task has recently attracted wide attention. recent methods mainly work on the temporal consistency in adjacent frames or frames with small interval. however, it still faces severe challenge of the inconsistency between frames with large interval. to address this issue, we propose a novel video colorization framework, which combines semantic correspondence into automatic video colorization to keep long - range consistency. firstly, a reference colorization network is designed to automatically colorize the first frame of each video, obtaining a reference image to supervise the following whole colorization process. such automatically colorized reference image can not only avoid labor - intensive and time - consuming manual selection, but also enhance the similarity between reference and grayscale images. afterwards, a semantic correspondence network and an image colorization network are introduced to colorize a series of the remaining frames with the help of the reference. each frame is supervised by both the reference image and the immediately colorized preceding frame to improve both short - range and long - range temporal consistency. extensive experiments demonstrate that our method outperforms other methods in maintaining temporal consistency both qualitatively and quantitatively. in the ntire 2023 video colorization challenge, our method ranks at the 3rd place in color distribution consistency ( cdc ) optimization track.
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arxiv:2305.07904
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motivated by recent work of deruelle - schulze - simon, we study complete weakly pic1 ricci flows with euclidean volume growth coming out of metric cones. we show that such a ricci flow must be an expanding gradient ricci soliton, and as a consequence, any metric cone at infinity of a complete weakly pic1 k \ " ahler manifold with euclidean volume growth is biholomorphic to complex euclidean space in a canonical way.
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arxiv:2404.12755
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we report the results of an observational study aimed at searching for magnetic pulsating hot stars suitable for magneto - asteroseismology. a sample of sixteen chemically peculiar stars was selected and analysed using both high - resolution spectropolarimetry with espadons and k2 high - precision space photometry. for all stars, we derive the effective temperature, surface gravity, rotational and non - rotational line broadening from our spectropolarimetric data. high - quality k2 light curves were obtained for thirteen of the sixteen stars and revealed rotational modulation, providing accurate rotation periods. two stars show evidence for roap pulsations, and one star shows signatures of internal gravity waves or unresolved g - mode pulsations. we confirm the presence of a large - scale magnetic field for eleven of the studied stars, of which nine are first detections. further, we report one marginal detection and four non - detections. two of the stars with a non - detected magnetic field show rotational modulation due to surface abundance inhomogeneities in the k2 light curve, and we confirm that the other two are chemically peculiar. thus, these five stars likely host a weak ( undetected ) large - scale magnetic field.
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arxiv:1805.00781
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one of the deepest questions in condensed matter physics concerns what other phases compete with superconductivity in high - transition - temperature ( high - tc ) superconductors. one candidate is the " stripe " phase, in which the carriers ( holes ) condense into rivers of charge separating regions of antiferromagnetism. a related but lesser known system is the " spin ladder ", which consists of two coupled chains of magnetic ions forming an array of rungs. a doped ladder can be thought of as a high - tc material with lower dimensionality, and has been predicted to exhibit both superconductivity and an insulating " hole crystal " phase in which the carriers are localised through many - body interactions. the competition between the two resembles that between static stripes and superconductivity in high - tc materials. here we report evidence, from resonant x - ray scattering, for the existence of a hole crystal in the doped spin ladder of sr14cu24o41. this phase exists without a detectable distortion in the structural lattice, indicating it arises from many - body effects. our measurements confirm theoretical predictions and support the picture that proximity to charge ordered states is a general property of superconductivity in copper - oxides.
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arxiv:cond-mat/0501087
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let $ \ ff $ be an arbitrary field and $ ( \ bm { g } _ { n, d / n } ) _ n $ be a sequence of sparse weighted erd \ h { o } s - r \ ' enyi random graphs on $ n $ vertices with edge probability $ d / n $, where weights from $ \ ff \ setminus \ { 0 \ } $ are assigned to the edges according to a fixed matrix $ j _ n $. we show that the normalised rank of the adjacency matrix of $ ( \ bm { g } _ { n, d / n } ) _ n $ converges in probability to a constant, and derive the limiting expression. our result shows that for the general class of sparse symmetric matrices under consideration, the asymptotics of the normalised rank are independent of the edge weights and even the field, in the sense that the limiting constant for the general case coincides with the one previously established for adjacency matrices of sparse ( non - weighted ) erd \ h { o } s - r \ ' enyi matrices over $ \ rr $ from \ cite { bordenave2011rank }. our proof, which is purely combinatorial in its nature, is based on an intricate extension of the novel perturbation approach from \ cite { coja2022rank } to the symmetric setting.
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arxiv:2301.12978
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the prevalence of suicide has been on the rise since the 20th century, causing severe emotional damage to individuals, families, and communities alike. despite the severity of this suicide epidemic, there is so far no reliable and systematic way to assess suicide intent of a given individual. through efforts to automate and systematize diagnosis of mental illnesses over the past few years, verbal and acoustic behaviors have received increasing attention as biomarkers, but little has been done to study eyelids, gaze, and head pose in evaluating suicide risk. this study explores statistical analysis, feature selection, and machine learning classification as means of suicide risk evaluation and nonverbal behavioral interpretation. applying these methods to the eye and head signals extracted from our unique dataset, this study finds that high - risk suicidal individuals experience psycho - motor retardation and symptoms of anxiety and depression, characterized by eye contact avoidance, slower blinks and a downward eye gaze. by comparing results from different methods of classification, we determined that these features are highly capable of automatically classifying different levels of suicide risk consistently and with high accuracy, above 98 %. our conclusion corroborates psychological studies, and shows great potential of a systematic approach in suicide risk evaluation that is adoptable by both healthcare providers and naive observers.
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arxiv:2206.07522
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item nonresponse is frequently encountered in practice. ignoring missing data can lose efficiency and lead to misleading inference. fractional imputation is a frequentist approach of imputation for handling missing data. however, the parametric fractional imputation of \ cite { kim2011parametric } may be subject to bias under model misspecification. in this paper, we propose a novel semiparametric fractional imputation method using gaussian mixture models. the proposed method is computationally efficient and leads to robust estimation. the proposed method is further extended to incorporate the categorical auxiliary information. the asymptotic model consistency and $ \ sqrt { n } $ - consistency of the semiparametric fractional imputation estimator are also established. some simulation studies are presented to check the finite sample performance of the proposed method.
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arxiv:1809.05976
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we find that the local galactic extinction towards the field of gamma - ray burst grb970228 is $ a _ v = 1. 09 ^ { + 0. 10 } _ { - 0. 20 } $, which implies a substantial dimming and change in the spectral slope of the intrinsic grb970228 afterglow. we measure a color $ ( v _ { 606 } - i _ { 814 } ) _ { st } = - 0. 18 ^ { + 0. 51 } _ { - 0. 61 } $ for the extended source coincident with the afterglow. taking into account our measurement of the extinction toward this field, this color implies that the extended source is most likely a galaxy undergoing star formation, in agreement with our earlier conclusion ( \ cite { cl98 } ). in a separate analysis, we find that the inferred intrinsic spectrum of the grb 980329 afterglow is consistent with the predictions of the simplest relativistic fireball model. we also find that the intrinsic spectrum of the afterglow is extincted both by dust ( source frame $ a _ v \ ga 1 $ mag ), and that the shape of the extinction curve is typical of young star - forming regions like the orion nebula but is not typical of older star - forming or starburst regions. the $ \ approx $ 2 mag drop between the $ r $ and the $ i $ bands can be explained by the far - ultraviolet non - linear component of the extinction curve if $ 3 \ la z \ la 4 $, and by the 2175 \ aa \ bump if $ z \ approx 2 $ ; other redshifts are not consistent with the observational data, given our general model.
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arxiv:astro-ph/9909027
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this paper presents our work on development of owl - driven systems for formal representation and reasoning about terminological knowledge and facts in petrology. the long - term aim of our project is to provide solid foundations for a large - scale integration of various kinds of knowledge, including basic terms, rock classification algorithms, findings and reports. we describe three steps we have taken towards that goal here. first, we develop a semi - automated procedure for transforming a database of igneous rock samples to texts in a controlled natural language ( cnl ), and then a collection of owl ontologies. second, we create an owl ontology of important petrology terms currently described in natural language thesauri. we describe a prototype of a tool for collecting definitions from domain experts. third, we present an approach to formalization of current industrial standards for classification of rock samples, which requires linear equations in owl 2. in conclusion, we discuss a range of opportunities arising from the use of semantic technologies in petrology and outline the future work in this area.
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arxiv:1106.1510
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in multi - agent environments, agents often struggle to learn optimal policies due to sparse or delayed global rewards, particularly in long - horizon tasks where it is challenging to evaluate actions at intermediate time steps. we introduce temporal - agent reward redistribution ( tar $ ^ 2 $ ), a novel approach designed to address the agent - temporal credit assignment problem by redistributing sparse rewards both temporally and across agents. tar $ ^ 2 $ decomposes sparse global rewards into time - step - specific rewards and calculates agent - specific contributions to these rewards. we theoretically prove that tar $ ^ 2 $ is equivalent to potential - based reward shaping, ensuring that the optimal policy remains unchanged. empirical results demonstrate that tar $ ^ 2 $ stabilizes and accelerates the learning process. additionally, we show that when tar $ ^ 2 $ is integrated with single - agent reinforcement learning algorithms, it performs as well as or better than traditional multi - agent reinforcement learning methods.
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arxiv:2412.14779
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systems of two ordinary and partial differential equations ( odes and pdes ) had been obtained from a scalar complex ode by splitting it into its real and imaginary parts. the procedure was also carried out to obtain a four dimensional system by splitting a complex system of two odes into its real and imaginary parts. systems of three odes had not been accessible by these methods. in this paper the complex splitting is used iteratively to obtain three and four dimensional systems of odes and four dimensional systems of pdes for four functions of two and four variables. the new systems of four odes are distinct from the class obtained by the single split of a two dimensional system. illustrative examples are provided.
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arxiv:1108.5251
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we give a uniform approximation of the characteristic function of the boundary of a centrally symmetric n - dimensional compact and convex set by homogeneous polynomials of even degree $ d $ fulfilling $ | g _ d - 1 | \ leq e / d ^ { 1 / 2 - \ beta } $, for every $ \ beta > 0 $, large enough $ d $, and some constant $ e $ only depending on $ n $ and $ k $. in particular, this proves a conjecture posed by kroo in 2004, also known as the stone - weierstrass theorem for homogeneous polynomials. moreover, we introduce the d - volume ratio for a convex body $ k $ in $ \ mathbb r ^ n $, by means of its d - lasserre - l \ " owner polynomial. we also prove an upper bound of the d - volume ratio of the form $ 1 + f / d ^ { 3 / 2 - \ beta } $, for every $ \ beta > 0 $, large enough $ d $, and $ f $ some constant only depending on $ n $.
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arxiv:2012.04999
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stein discrepancies have emerged as a powerful statistical tool, being applied to fundamental statistical problems including parameter inference, goodness - of - fit testing, and sampling. the canonical stein discrepancies require the derivatives of a statistical model to be computed, and in return provide theoretical guarantees of convergence detection and control. however, for complex statistical models, the stable numerical computation of derivatives can require bespoke algorithmic development and render stein discrepancies impractical. this paper focuses on posterior approximation using stein discrepancies, and introduces a collection of non - canonical stein discrepancies that are gradient free, meaning that derivatives of the statistical model are not required. sufficient conditions for convergence detection and control are established, and applications to sampling and variational inference are presented.
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arxiv:2207.02636
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the advent of multiple readers in magnetic recording opens the possibility of replacing the current industry ' s single - track detection with the more promising multitrack detection architectures. we have proposed a first solution, a generalized partial - response maximum - likelihood ( gprml ) architecture, that extends the conventional prml paradigm to jointly detect multiple asynchronous tracks. in this paper, we propose to replace the conventional communication - theoretic multiple - input multiple - output equalizer in the gprml architecture with a neural network equalizer for better adaption to the nonlinearity of the underlying channel. we evaluate the proposed equalization strategy on a realistic two - dimensional magnetic - recording channel, and find that the proposed equalizer outperforms the conventional linear equalizer, by a 35 % reduction in the bit - error rate.
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arxiv:2207.02432
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mariana trench is the deepest place on the earth. it crosses four tectonic plates of the pacific ocean : mariana, caroline, pacific and philippine. the formation of the trench is caused by the complex interconnection of various environmental factors. the aim of this study was to describe and characterize various impact factors affecting formation of the mariana trench geomorphology and continental margin environments using r programming language and mathematical algorithms of correlation methods written on r code. to record the system of geological, tectonic, geographic, oceanological and bathymetric features affecting mariana trench, a combination of statistical methods, gis and r programming codes were applied. the questions answered are as follows : which factors are the most influencing for the mariana trench morphology, and to what extend do they affect its development? is sedimental thickness of the ocean trench basement more important factors for the trench formation comparing to the steepness slope angle and aspect degree? three methods of computing were tested : pearson correlation, spearman correlation, kendall correlation, numerical correlogram, correlation matrix and cross - correlatios to analyze environmental impact factors. the correlogram matrices are computed and visualized by r scripting libraries. complex usage of programming tools, mathematical statistics and geospatial analysis enabled to get a differentiated understandings of the hadal environments of the mariana trench. the results revealed following three types of factors having the highest score : geometric ( tg { \ deg } slope angle ), geologic ( sedimental thickness ) and tectonic structure. the results furthermore indicated that tectonic plates, sedimental thickness of the trench basement and igneous volcanic areas causing earthquakes play the most essential role in the geomorphology of the trench.
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arxiv:1812.01099
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in this paper some concepts of convex analysis on hyperbolic space are studied. we first study properties of the intrinsic distance, for instance, we present the spectral decomposition of its hessian. next, we study the concept of convex sets and the intrinsic projection onto these sets. we also study the concept of convex functions and present first and second order characterizations of these functions, as well as some optimization concepts related to them. an extensive study of the hyperbolically convex quadratic functions is also presented.
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arxiv:2110.06514
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in radio frequency applications, electric circuits generate signals, which are amplitude modulated and / or frequency modulated. a mathematical modelling yields typically systems of differential algebraic equations ( daes ). a multivariate signal model transforms the daes into multirate partial differential algebraic equations ( mpdaes ). in the case of frequency modulation, an additional condition is required to identify an appropriate solution. we consider a necessary condition for an optimal solution and a phase condition. a method of lines, which discretises the mpdaes as well as the additional condition, generates a larger system of daes. we analyse the differential index of this approximative dae system, where the original daes are assumed to be semi - explicit systems. the index depends on the inclusion of either differential variables or algebraic variables in the additional condition. we present results of numerical simulations for an illustrative example, where the index is also verified by a numerical method.
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arxiv:1707.08201
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given the broad application of infrared technology across diverse fields, there is an increasing emphasis on investigating super - resolution techniques for infrared images within the realm of deep learning. despite the impressive results of current transformer - based methods in image super - resolution tasks, their reliance on the self - attentive mechanism intrinsic to the transformer architecture results in images being treated as one - dimensional sequences, thereby neglecting their inherent two - dimensional structure. moreover, infrared images exhibit a uniform pixel distribution and a limited gradient range, posing challenges for the model to capture effective feature information. consequently, we suggest a potent transformer model, termed large kernel transformer ( lkformer ), to address this issue. specifically, we have designed a large kernel residual attention ( lkra ) module with linear complexity. this mainly employs depth - wise convolution with large kernels to execute non - local feature modeling, thereby substituting the standard self - attentive layer. additionally, we have devised a novel feed - forward network structure called gated - pixel feed - forward network ( gpfn ) to augment the lkformer ' s capacity to manage the information flow within the network. comprehensive experimental results reveal that our method surpasses the most advanced techniques available, using fewer parameters and yielding considerably superior performance. the source code will be available at https : / / github. com / sad192 / large - kernel - transformer.
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arxiv:2401.11859
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accurate and explainable artificial - intelligence ( ai ) models are promising tools for the acceleration of the discovery of new materials, ore new applications for existing materials. recently, symbolic regression has become an increasingly popular tool for explainable ai because it yields models that are relatively simple analytical descriptions of target properties. due to its deterministic nature, the sure - independence screening and sparsifying operator ( sisso ) method is a particularly promising approach for this application. here we describe the new advancements of the sisso algorithm, as implemented into sisso + +, a c + + code with python bindings. we introduce a new representation of the mathematical expressions found by sisso. this is a first step towards introducing ` ` grammar ' ' rules into the feature creation step. importantly, by introducing a controlled non - linear optimization to the feature creation step we expand the range of possible descriptors found by the methodology. finally, we introduce refinements to the solver algorithms for both regression and classification, that drastically increase the reliability and efficiency of sisso. for all of these improvements to the basic sisso algorithm, we not only illustrate their potential impact, but also fully detail how they operate both mathematically and computationally.
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arxiv:2305.01242
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in this paper we consider estimation of unobserved components in state space models using a dynamic factor approach to incorporate auxiliary information from high - dimensional data sources. we apply the methodology to unemployment estimation as done by statistics netherlands, who uses a multivariate state space model to produce monthly figures for the unemployment using series observed with the labour force survey ( lfs ). we extend the model by including auxiliary series of google trends about job - search and economic uncertainty, and claimant counts, partially observed at higher frequencies. our factor model allows for nowcasting the variable of interest, providing reliable unemployment estimates in real - time before lfs data become available.
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arxiv:1901.11355
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we show that if a countable structure $ m $ in a finite relational language is not cellular, then there is an age - preserving $ n \ supseteq m $ such that $ 2 ^ { \ aleph _ 0 } $ many structures are bi - embeddable with $ n $. the proof proceeds by a case division based on mutual algebraicity.
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arxiv:1910.11230
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modern large - scale data analysis increasingly faces the challenge of achieving computational efficiency as well as statistical accuracy, as classical statistically efficient methods often fall short in the first regard. in the context of testing monotonicity of a regression function, we propose fomt ( fast and optimal monotonicity test ), a novel methodology tailored to meet these dual demands. fomt employs a sparse collection of local tests, strategically generated at random, to detect violations of monotonicity scattered throughout the domain of the regression function. this sparsity enables significant computational efficiency, achieving sublinear runtime in most cases, and quasilinear runtime ( i. e., linear up to a log factor ) in the worst case. in contrast, existing statistically optimal tests typically require at least quadratic runtime. fomt ' s statistical accuracy is achieved through the precise calibration of these local tests and their effective combination, ensuring both sensitivity to violations and control over false positives. more precisely, we show that fomt separates the null and alternative hypotheses at minimax optimal rates over h \ " older function classes of smoothness order in $ ( 0, 2 ] $. further, when the smoothness is unknown, we introduce an adaptive version of fomt, based on a modified lepskii principle, which attains statistical optimality and meanwhile maintains the same computational complexity as if the intrinsic smoothness were known. extensive simulations confirm the competitiveness and effectiveness of both fomt and its adaptive variant.
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arxiv:2503.03020
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this is the second part of a series of three strongly related papers in which three equivalent structures are studied : - internal categories in categories of monoids ; defined in terms of pullbacks relative to a chosen class of spans - crossed modules of monoids relative to this class of spans - simplicial monoids of so - called moore length 1 relative to this class of spans. the most important examples of monoids that are covered are small categories ( treated as monoids in categories of spans ) and bimonoids in symmetric monoidal categories ( regarded as monoids in categories of comonoids ). in this second part we define relative crossed modules of monoids and prove their equivalence with the relative categories of part i.
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arxiv:1803.04124
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his student democritus. later, epicurus would develop a full natural cosmology based on atomism, and would adopt a " canon " ( ruler, standard ) which established physical criteria or standards of scientific truth. the greek doctor hippocrates established the tradition of systematic medical science and is known as " the father of medicine ". a turning point in the history of early philosophical science was socrates ' example of applying philosophy to the study of human matters, including human nature, the nature of political communities, and human knowledge itself. the socratic method as documented by plato ' s dialogues is a dialectic method of hypothesis elimination : better hypotheses are found by steadily identifying and eliminating those that lead to contradictions. the socratic method searches for general commonly - held truths that shape beliefs and scrutinises them for consistency. socrates criticised the older type of study of physics as too purely speculative and lacking in self - criticism. in the 4th century bce, aristotle created a systematic programme of teleological philosophy. in the 3rd century bce, greek astronomer aristarchus of samos was the first to propose a heliocentric model of the universe, with the sun at the centre and all the planets orbiting it. aristarchus ' s model was widely rejected because it was believed to violate the laws of physics, while ptolemy ' s almagest, which contains a geocentric description of the solar system, was accepted through the early renaissance instead. the inventor and mathematician archimedes of syracuse made major contributions to the beginnings of calculus. pliny the elder was a roman writer and polymath, who wrote the seminal encyclopaedia natural history. positional notation for representing numbers likely emerged between the 3rd and 5th centuries ce along indian trade routes. this numeral system made efficient arithmetic operations more accessible and would eventually become standard for mathematics worldwide. = = = middle ages = = = due to the collapse of the western roman empire, the 5th century saw an intellectual decline, with knowledge of classical greek conceptions of the world deteriorating in western europe. : 194 latin encyclopaedists of the period such as isidore of seville preserved the majority of general ancient knowledge. in contrast, because the byzantine empire resisted attacks from invaders, they were able to preserve and improve prior learning. : 159 john philoponus, a byzantine scholar in the 6th century, started to question aristotle ' s teaching of physics, introducing the theory of impetus. : 307, 311, 363, 402 his criticism
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https://en.wikipedia.org/wiki/Science
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we derive data of 4615 star - forming early - type galaxies ( etgs ), which come from cross - match of the $ galaxy ~ zoo ~ 1 $ and the catalogue of the mpa - jhu emission - line measurements for the sloan digital sky survey data release 7. our sample distributes mainly at $ \ rm - 0. 7 < log ( sfr [ m _ { \ sun } yr ^ { - 1 } ] ) < 1. 2 $, and the median value of our sfrs is slightly higher than that shown in davis \ & young. we display a significant trend of lower / higher stellar mass etgs to have lower / higher sfr, and obtain our sample best fit of log ( sfr ) = $ ( 0. 74 \ pm0. 01 ) $ log $ ( m _ { * } / m _ { \ sun } ) - ( 7. 64 \ pm0. 10 ) $, finding the same slope as that found in cano - d \ ' { i } az et al. in our star - forming etg sample, we demonstrate clearly the correlation of the stellar mass and metallicity ( mz ) relation. we find that higher metallicity measurements may be introduced by the diffuse ionized gas, when the d16, sanch18, and sander18 indicators are used to calibrate the metallicity of etgs. we show the relations between sfr and 12 + log ( o / h ) with different metallicity estimators, and suggest that their correlations may be a consequence of the sfr - stellar mass and mz relations in etgs.
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arxiv:2112.09308
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cosmic strings in the brane universe have recently gained a great interest. i think the most interesting story is that future cosmological observations distinguish them from the conventional cosmic strings. if the strings are the higher - dimensional objects that can ( at least initially ) move along the compactified space, and finally settle down to ( quasi - ) degenerated vacua in the compactified space, then kinks should appear on the strings, which interpolate between the degenerated vacua. these kinks look like ` ` beads ' ' on the strings, which means that the strings turn into necklaces. moreover, in the case that the compact manifold is not simply connected, the string loop that winds around a non - trivial circle is stable due to the topological reason. since the existence of degenerated vacua and a non - trivial circle is the common feature of the brane models, it is important to study cosmological constraints on the cosmic necklaces and their stable winding states in the brane universe.
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arxiv:hep-ph/0601014
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we propose a very simple preprocessing algorithm for semidefinite programming. our algorithm inspects the constraints of the problem, deletes redundant rows and columns in the constraints, and reduces the size of the variable matrix. it often detects infeasibility. our algorithm does not rely on any optimization solver : the only subroutine it needs is cholesky factorization, hence it can be implemented with a few lines of code in machine precision. we present computational results on a set of problems arising mostly from polynomial optimization.
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arxiv:1608.02300
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biodiversity is declining at an unprecedented rate, impacting ecosystem services necessary to ensure food, water, and human health and well - being. understanding the distribution of species and their habitats is crucial for conservation policy planning. however, traditional methods in ecology for species distribution models ( sdms ) generally focus either on narrow sets of species or narrow geographical areas and there remain significant knowledge gaps about the distribution of species. a major reason for this is the limited availability of data traditionally used, due to the prohibitive amount of effort and expertise required for traditional field monitoring. the wide availability of remote sensing data and the growing adoption of citizen science tools to collect species observations data at low cost offer an opportunity for improving biodiversity monitoring and enabling the modelling of complex ecosystems. we introduce a novel task for mapping bird species to their habitats by predicting species encounter rates from satellite images, and present satbird, a satellite dataset of locations in the usa with labels derived from presence - absence observation data from the citizen science database ebird, considering summer ( breeding ) and winter seasons. we also provide a dataset in kenya representing low - data regimes. we additionally provide environmental data and species range maps for each location. we benchmark a set of baselines on our dataset, including sota models for remote sensing tasks. satbird opens up possibilities for scalably modelling properties of ecosystems worldwide.
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arxiv:2311.00936
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nsv 1907, formerly listed as an irregular variable in variability catalogues, was classified as an algol - type eclipsing binary in the catalina surveys periodic variable star catalogue. we have identified nsv 1907 as an ultraviolet ( uv ) bright source using measurements from the galex space telescope and detected obvious out - of - eclipse variability in archival photometric data from the catalina sky survey, which instigated a closer examination of the object. a spectrum and extensive multicolour photometric observations were acquired, from which we deduce that nsv 1907 is a deeply eclipsing, nova - like cataclysmic variable. apart from the orbital variations ( deep eclipses with a period of p ~ 6. 63 hours ), changes in mean brightness and irregular short - term variability ( flickering ) were observed. the presence of a secondary minimum at phase phi ~ 0. 5 was established, which indicates a significant contribution of the companion star to the optical flux of the system. we find possible evidence for sinusoidal variations with a period of p ~ 4. 2 d, which we interpret as the nodal precession period of the accretion disc. no outbursts or vy scl - like drops in brightness were detected either by the css or during our photometric monitoring. because of its spectral characteristics and the observed variability pattern, we propose nsv 1907 as a new moderately bright long - period sw sextantis star. further photometric and spectroscopic observations are encouraged.
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arxiv:1608.07610
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recent experiments suggest that polarized photons may couple significantly to pseudoscalar particles such as axions. we study the possible observational signatures of axion - photon coupling for radiation from magnetic stars, with particular focus on neutron stars. we present general methods for calculating the axion - photon conversion probability during propagation through a varying magnetized vacuum as well as across an inhomogeneous atmosphere. partial axion - photon conversion may take place in the vacuum region outside the neutron star. strong axion - photon mixing occurs due to a resonance in the atmosphere, and depending on the axion coupling strength and other parameters, significant axion - photon conversion can take place at the resonance. such conversions may produce observable effects on the radiation spectra and polarization signals from the star. we also apply our results to axion - photon propagation in the sun and in magnetic white dwarfs. we find that there is no appreciable conversion of solar axions to photons during the propagation.
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arxiv:astro-ph/0609775
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