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within the framework of perturbation theory, we explore in detail the mixing of orbital angular momentum ( oam ) modes due to a fiber bend in a step - index multimode fiber. using scalar wave equation, we develop a complete set of analytic expressions for mode - mixing, including those for the $ 2 \ pi $ walk - off length, which is the distance traveled within the bent fiber before an oam mode transforms into its negative topological charge counterpart, and back into itself. the derived results provide insight into the nature of the bend effects, clearly revealing the mathematical dependence on the bend radius and the topological charge. we numerically simulate the theoretical results with applications to a few - mode fiber and a multimode fiber, and calculate bend - induced modal crosstalk with implications for mode - multiplexed systems. the presented perturbation technique is general enough to be applicable to other perturbations like ellipticity and easily extendable to other fibers with step - index - like profile as in the ring fiber. | arxiv:1907.04664 |
the labeled data required to learn pose estimation for articulated objects is difficult to provide in the desired quantity, realism, density, and accuracy. to address this issue, we develop a method to learn representations, which are very specific for articulated poses, without the need for labeled training data. we exploit the observation that the object pose of a known object is predictive for the appearance in any known view. that is, given only the pose and shape parameters of a hand, the hand ' s appearance from any viewpoint can be approximated. to exploit this observation, we train a model that - - given input from one view - - estimates a latent representation, which is trained to be predictive for the appearance of the object when captured from another viewpoint. thus, the only necessary supervision is the second view. the training process of this model reveals an implicit pose representation in the latent space. importantly, at test time the pose representation can be inferred using only a single view. in qualitative and quantitative experiments we show that the learned representations capture detailed pose information. moreover, when training the proposed method jointly with labeled and unlabeled data, it consistently surpasses the performance of its fully supervised counterpart, while reducing the amount of needed labeled samples by at least one order of magnitude. | arxiv:1804.03390 |
we report on electrical transport measurements in a carbon nanotube quantum dot coupled to a normal and a superconducting lead. depending on the ratio of kondo temperature $ t _ { k } $ and superconducting gap $ \ delta $ the zero bias conductance resonance either is split into two side - peaks or persists. we also compare our data with a simple model of a resonant level - superconductor interface. | arxiv:cond-mat/0403431 |
we present briefly the deformation philosophy and indicate, with references, how it was applied to the quantization of nambu mechanics and to particle physics in anti de sitter space. | arxiv:hep-th/9809073 |
an upper bound is obtained on the rank of a torus which can act smoothly and effectively on a smooth, closed, simply connected, rationally elliptic manifold. in the maximal - rank case, the manifolds admitting such actions are classified up to equivariant rational homotopy type. | arxiv:1511.08383 |
in this paper, we propose an architecture to solve a novel problem statement that has stemmed more so in recent times with an increase in demand for virtual content delivery due to the covid - 19 pandemic. all educational institutions, workplaces, research centers, etc. are trying to bridge the gap of communication during these socially distanced times with the use of online content delivery. the trend now is to create presentations, and then subsequently deliver the same using various virtual meeting platforms. the time being spent in such creation of presentations and delivering is what we try to reduce and eliminate through this paper which aims to use machine learning ( ml ) algorithms and natural language processing ( nlp ) modules to automate the process of creating a slides - based presentation from a document, and then use state - of - the - art voice cloning models to deliver the content in the desired author ' s voice. we consider a structured document such as a research paper to be the content that has to be presented. the research paper is first summarized using bert summarization techniques and condensed into bullet points that go into the slides. tacotron inspired architecture with encoder, synthesizer, and a generative adversarial network ( gan ) based vocoder, is used to convey the contents of the slides in the author ' s voice ( or any customized voice ). almost all learning has now been shifted to online mode, and professionals are now working from the comfort of their homes. due to the current situation, teachers and professionals have shifted to presentations to help them in imparting information. in this paper, we aim to reduce the considerable amount of time that is taken in creating a presentation by automating this process and subsequently delivering this presentation in a customized voice, using a content delivery mechanism that can clone any voice using a short audio clip. | arxiv:2106.14213 |
radars and cameras are mature, cost - effective, and robust sensors and have been widely used in the perception stack of mass - produced autonomous driving systems. due to their complementary properties, outputs from radar detection ( radar pins ) and camera perception ( 2d bounding boxes ) are usually fused to generate the best perception results. the key to successful radar - camera fusion is the accurate data association. the challenges in the radar - camera association can be attributed to the complexity of driving scenes, the noisy and sparse nature of radar measurements, and the depth ambiguity from 2d bounding boxes. traditional rule - based association methods are susceptible to performance degradation in challenging scenarios and failure in corner cases. in this study, we propose to address radar - camera association via deep representation learning, to explore feature - level interaction and global reasoning. additionally, we design a loss sampling mechanism and an innovative ordinal loss to overcome the difficulty of imperfect labeling and to enforce critical human - like reasoning. despite being trained with noisy labels generated by a rule - based algorithm, our proposed method achieves a performance of 92. 2 % f1 score, which is 11. 6 % higher than the rule - based teacher. moreover, this data - driven method also lends itself to continuous improvement via corner case mining. | arxiv:2103.07825 |
humans construct internal cognitive maps of their environment directly from sensory inputs without access to a system of explicit coordinates or distance measurements. while machine learning algorithms like slam utilize specialized visual inference procedures to identify visual features and construct spatial maps from visual and odometry data, the general nature of cognitive maps in the brain suggests a unified mapping algorithmic strategy that can generalize to auditory, tactile, and linguistic inputs. here, we demonstrate that predictive coding provides a natural and versatile neural network algorithm for constructing spatial maps using sensory data. we introduce a framework in which an agent navigates a virtual environment while engaging in visual predictive coding using a self - attention - equipped convolutional neural network. while learning a next image prediction task, the agent automatically constructs an internal representation of the environment that quantitatively reflects distances. the internal map enables the agent to pinpoint its location relative to landmarks using only visual information. the predictive coding network generates a vectorized encoding of the environment that supports vector navigation where individual latent space units delineate localized, overlapping neighborhoods in the environment. broadly, our work introduces predictive coding as a unified algorithmic framework for constructing cognitive maps that can naturally extend to the mapping of auditory, sensorimotor, and linguistic inputs. | arxiv:2308.10913 |
} $ - packing } for any fixed finite family $ \ mathcal { f } $ of connected graphs admit almost linear kernels on every nowhere dense class of graphs and linear kernels on every class of graphs with bounded expansion. our results extend the results for \ textsc { distance - $ r $ dominating set } by drange et al. ( stacs 2016 ) and eickmeyer et al. ( icalp 2017 ), and the result for \ textsc { distance - $ r $ independent set } by pilipczuk and siebertz ( ejc 2021 ). | arxiv:2207.06660 |
in this paper we study the relaxation process of peierls - nabarro dislocation model, which is a gradient flow with singular nonlocal energy and double well potential describing how the materials relax to its equilibrium with the presence of a dislocation. we prove the dynamic solution to peierls - nabarro model will converge exponentially to a shifted steady profile which is uniquely determined. | arxiv:1907.02002 |
the triangle - free process begins with an empty graph on n vertices and iteratively adds edges chosen uniformly at random subject to the constraint that no triangle is formed. we determine the asymptotic number of edges in the maximal triangle - free graph at which the triangle - free process terminates. we also bound the independence number of this graph, which gives an improved lower bound on the ramsey numbers r ( 3, t ) : we show r ( 3, t ) > ( 1 - o ( 1 ) ) t ^ 2 / ( 4 log t ), which is within a 4 + o ( 1 ) factor of the best known upper bound. our improvement on previous analyses of this process exploits the self - correcting nature of key statistics of the process. furthermore, we determine which bounded size subgraphs are likely to appear in the maximal triangle - free graph produced by the triangle - free process : they are precisely those triangle - free graphs with density at most 2. | arxiv:1302.5963 |
in this paper, we discuss several additional properties a power linear keller map may have. the structural conjecture by druzkowski in [ dru ] asserts that two such properties are equivalent, but we show that one of this properties is stronger than the other. we even show that the property of linear triangularizability is strictly in between. furthermore, we give some positive results for small dimensions and small jacobian ranks. | arxiv:1302.6930 |
magnetic resonance imaging ( mri ) is universally acknowledged as an excellent tool to extract detailed spatial information with minimally invasive measurements. efforts toward ultra - low - field ( ulf ) mri are made to simplify the scanners and to reduce artefacts and incompatibilities. optical atomic magnetometers ( oams ) are among the sensitive magnetic detectors eligible for ulf operation, however they are not compatible with the strong field gradients used in mri. we show that a magnetic - dressing technique restores the oams operability despite the gradient, and we demonstrate sub - millimetric resolution mri with a compact experimental setup based on an in situ detection. the proof - of - concept experiment produces unidimensional imaging of remotely magnetized samples with a dual sensor, but the approach is suited to be adapted for 3 - d imaging of samples magnetized in loco. an extension to multi - sensor architectures is also possible. | arxiv:1908.01283 |
recent achievements at the evn mkiv data processor at jive include decreasing the read - out time for the whole correlator to 0. 25 seconds ( or 0. 125 s for half the correlator ), improving the end quality of user data ( e. g., applying an improved 2 - bit van vleck correction ), developing new astronomical capabilities ( e. g., oversampling to x 4, wider - field mapping ), and strengthening liaison procedures with pis ( e. g., pipelining, the evn archive facility ). at the same time, the move to a disk - based evn and regular incorporation of ftp fringe - checks is well underway, resulting in more reliable data quality. we will review these developments, highlighting how they may broaden the kinds of astronomy you can do. we ' ll also go over some measures you can take to help you get the most out of these new / improved features. | arxiv:astro-ph/0412684 |
in this paper, we characterize the sharp constant and maximizing functions for weighted poincar \ ' e inequalities. these results lead to refinements of hardy ' s inequality obtained by adding remainder terms involving \ ( l ^ p \ ) norms. we use techniques that avoid symmetric rearrangement argument, simplifying the analysis of these inequalities in both euclidean and non - euclidean contexts. specifically, this method applies to a variety of settings, such as the heisenberg group, various carnot groups and operators expressed as sums of squares of vector fields. significant examples include the heisenberg - greiner operator and the baouendi - grushin operator. | arxiv:2407.10840 |
we aim to study the set of color sets of continuous regions of an image given as a matrix of $ m $ rows over $ n \ geq m $ columns where each element in the matrix is an integer from $ [ 1, \ sigma ] $ named a { \ em color }. the set of distinct colors in a region is called fingerprint. we aim to compute, index and query the fingerprints of all rectangular regions named rectangles. the set of all such fingerprints is denoted by $ { \ cal f } $. a rectangle is { \ em maximal } if it is not contained in a greater rectangle with the same fingerprint. the set of all locations of maximal rectangles is denoted by $ \ mathcal { l }. $ we first explain how to determine all the $ | \ mathcal { l } | $ maximal locations with their fingerprints in expected time $ o ( nm ^ 2 \ sigma ) $ using a monte carlo algorithm ( with polynomially small probability of error ) or within deterministic $ o ( nm ^ 2 \ sigma \ log ( \ frac { | \ mathcal { l } | } { nm ^ 2 } + 2 ) ) $ time. we then show how to build a data structure which occupies $ o ( nm \ log n + \ mathcal { | l | } ) $ space such that a query which asks for all the maximal locations with a given fingerprint $ f $ can be answered in time $ o ( | f | + \ log \ log n + k ) $, where $ k $ is the number of maximal locations with fingerprint $ f $. if the query asks only for the presence of the fingerprint, then the space usage becomes $ o ( nm \ log n + | { \ cal f } | ) $ while the query time becomes $ o ( | f | + \ log \ log n ) $. we eventually consider the special case of squared regions ( squares ). | arxiv:1608.07847 |
chip - firing and rotor - routing are two well - studied examples of abelian networks. we study the complexity of their respective reachability problems. we show that the rotor - routing reachability problem is decidable in polynomial time, and we give a simple characterization of when a chip - and - rotor configuration is reachable from another one. for chip - firing, it has been known that the reachability problem is in p if we have a class of graphs whose period length is polynomial ( for example, eulerian digraphs ). here we show that in the general case, chip - firing reachability is hard in the sense that if the chip - firing reachability problem were in p for general digraphs, then the polynomial hierarchy would collapse to np. we encode graphs by their adjacency matrix, and we encode ribbon structures " succinctly ", only remembering the number of consecutive parallel edges. | arxiv:2102.11970 |
##scalar and vector $ t _ { cc \ bar { q } \ bar { q } ' } $ states, we observe that the interpolating currents lead to two classes : class h ( heavy ) states with masses around 6gev and class l ( light ) states around ( 3. 8 - 4. 4 ) gev where the pseudoscalar ( resp. all vector states ) are below the $ \ overline { d } d _ 0, ~ ~ overline { d } _ s d _ { s0 } $ ( resp. $ \ overline { d } d _ 1, ~ ~ \ overline { d } _ s d _ { s1 } $ ) open charm thresholds. finally, we extend the whole study to the bottom sector and confront our results with the ones from different lsr predictions and some other approaches in the literature. | arxiv:2309.13547 |
we study the shape of eight dynamically relaxed galaxy clusters observed with the hubble space telescope and chandra x - ray observatory. using strong and weak gravitational lensing, the shape of the brightest cluster galaxy and the x - ray isophote we study the ellipticity of the cluster halo at four different radii. we find that the proxies probing the inner regions of the cluster are strongly coupled with the bcg shape correlated with both the shape predicted by strong gravitational lensing and the x - ray isophote. conversely we find no such correlation between the shape as predicted by the weak lensing and the other three probes suggesting any coupling between the inner and outer regions is weak. we also present in this paper the public release of the hst weak lensing shape measurement code pyrrg, directly available from pypi ( https : / / pypi. org / project / pyrrg / ). this python3. 7 code, based on rhodes et al. ( 2000 ) adopts an automated star - galaxy classifier based on a random forest and outputs scientifically useful products such as weak lensing catalogues suitable for the mass mapping algorithm lenstool. | arxiv:1911.06333 |
the role of radiation pressure in dust migration and the opening of inner cavities in transitional disks is revisited in this paper. dust dynamics including radiation pressure is often studied in axisymmetric models, but in this work, we show that highly non - axisymmetric features can arise from an instability at the inner disk edge. dust grains clump into high density features there, allowing radiation to leak around them and penetrate deeper into the disk, changing the course of dust migration. our proof - of - concept, two - dimensional, vertically - averaged simulations show that the combination of radiation pressure, shadowing, and gas drag can produce a net outward migration, or recession, of the dust component of the disk. the recession speed of the inner disk edge is on the order of $ 10 ^ { - 5 } $ times keplerian speed in our parameter space, which is faster than the background viscous flow, assuming a shakura & sunyaev viscosity alpha $ \ lesssim 10 ^ { - 3 } $. this speed, if sustained over the lifetime of the disk, can result in a dust cavity as large as tens of au. | arxiv:2202.02328 |
chiroptical responses of helical superstructures are determined by collective behaviors of the individual building blocks. in this paper, we present a full theoretical description of the collective resonance in superstructures. we use the gold nanorods as individual building blocks and arrange them helically along an axis in an end - to - end fashion. numerical simulations on single - unit cells reveal that the plasmonic coupling between the nanorods produces hybridized resonances, whose intensity is strongly dependent on the excitation light with left - or right - handed circular polarizations ( lcp or rcp ). a node - mode criterion is proposed on the basis of the microscopic mechanism, which successfully explains the difference between lcp and rcp. we further demonstrate, by repeating the unit cell from 1 to infinity along the helical axis, the multiple hybridized resonances gradually evolve and merge into a single collective resonance, whose energy is also dependent on lcp and rcp. an analytical description is provided for the collective resonance of the helical superstructure on the basis of the coupled dipole approximation method. our theory shows that n collective resonance modes are present in the helical superstructure with the unit cell consisting of $ n $ nanorods. strikingly, only one resonance can be excited by the incident light with certain circular polarization. we propose a universal selection rule for such selective excitation of the collective resonances by analyzing the symmetry of the helical superstructures. the new insights provided in this work may shed light on future designs and fabrications of helical superstructures using plasmonic building blocks. | arxiv:1911.06098 |
copyright policies play a pivotal role in protecting the intellectual property of creators and companies in creative industries. the advent of cost - reducing technologies, such as generative ai, in these industries calls for renewed attention to the role of these policies. this paper studies product positioning and competition in a market of creatively differentiated products and the competitive and welfare effects of copyright protection. a common feature of products with creative elements is that their key attributes ( e. g., images and text ) are unstructured and thus high - dimensional. we focus on a stylized design product, fonts, and use data from the world ' s largest online marketplace for fonts. we use neural network embeddings to quantify unstructured attributes and measure the visual similarity. we show that this measure closely aligns with actual human perception. based on this measure, we empirically find that competitions occur locally in the visual characteristics space. we then develop a structural model for supply and demand that integrate the embeddings. through counterfactual analyses, we find that local copyright protection can enhance consumer welfare when products are relocated, and the interplay between copyright and cost - reducing technologies is essential in determining an optimal policy for social welfare. we believe that the embedding analysis and empirical models introduced in this paper can be applicable to a range of industries where unstructured data captures essential features of products and markets. | arxiv:2501.16120 |
we apply the semiclassical theory of transport to quantum dots with exact and approximate spatial symmetries ; left - right mirror symmetry, up - down mirror symmetry, inversion symmetry or four - fold symmetry. in this work - the first of a pair of articles - we consider ( a ) perfectly symmetric dots and ( b ) nearly symmetric dots in which the symmetry is broken by the dot ' s internal dynamics. the second article addresses symmetry - breaking by displacement of the leads. using semiclassics, we identify the origin of the symmetry - induced interference effects that contribute to weak - localization corrections and universal conductance fluctuations. for perfect spatial symmetry, we recover results previously found using the random - matrix theory conjecture. we then go on to show how the results are affected by asymmetries in the dot, magnetic fields and decoherence. in particular, the symmetry - asymmetry crossover is found to be described by a universal dependence on an asymmetry parameter $ \ gamma _ { asym } $. however, the form of this parameter is very different depending on how the dot is deformed away from spatial symmetry. symmetry - induced interference effects are completely destroyed when the dot ' s boundary is globally deformed by less than an electron wavelength. in contrast, these effects are only reduced by a finite amount when a part of the dot ' s boundary smaller than a lead - width is deformed an arbitrarily large distance. | arxiv:0906.0891 |
regular sturm - liouville problems with indefinite weight functions may possess finitely many non - real eigenvalues. in this note we prove explicit bounds on the real and imaginary parts of these eigenvalues in terms of the coefficients of the differential expression. | arxiv:1306.0323 |
federated learning ( fl ) has been gaining popularity as a collaborative learning framework to train deep learning - based object detection models over a distributed population of clients. despite its advantages, fl is vulnerable to model hijacking. the attacker can control how the object detection system should misbehave by implanting trojaned gradients using only a small number of compromised clients in the collaborative learning process. this paper introduces stdlens, a principled approach to safeguarding fl against such attacks. we first investigate existing mitigation mechanisms and analyze their failures caused by the inherent errors in spatial clustering analysis on gradients. based on the insights, we introduce a three - tier forensic framework to identify and expel trojaned gradients and reclaim the performance over the course of fl. we consider three types of adaptive attacks and demonstrate the robustness of stdlens against advanced adversaries. extensive experiments show that stdlens can protect fl against different model hijacking attacks and outperform existing methods in identifying and removing trojaned gradients with significantly higher precision and much lower false - positive rates. | arxiv:2303.11511 |
presented at the meeting of the division of particles and fields, august 1996, in minneapolis. the work presented here is based upon a recent paper ( hep - ph / 9608413 ) done in collaboration with oscar f. hernandez, ivan maksymyk, and helene nadeau. the nrqcd predictions for the polarization of the j / psi produced in b - > j / psi + x, as well as the helicity - summed production rate are presented. | arxiv:hep-ph/9608457 |
\ { | a _ n | r ^ n \ colon n \ geq 0 \ } $ \ for $ r \ in [ 0, 1 ). $ | arxiv:1206.3655 |
factorization, in the sense defined for inclusive hard scattering, is discussed for diffractive hard scattering. a factorization theorem similar to its inclusive counterpart is presented for diffractive dis. for hadron - hadron diffractive hard scattering, in contrast to its inclusive counterpart, the expected breakdown of factorization is discussed. cross section estimates are given from a simple field theory model for non - factorizing double - pomeron - exchange ( dpe ) dijet production with and without account for sudakov suppression. | arxiv:hep-ph/9707499 |
testing whether a variable of interest affects the outcome is one of the most fundamental problem in statistics and is often the main scientific question of interest. to tackle this problem, the conditional randomization test ( crt ) is widely used to test the independence of variable ( s ) of interest ( x ) with an outcome ( y ) holding other variable ( s ) ( z ) fixed. the crt uses randomization or design - based inference that relies solely on the iid sampling of ( x, z ) to produce exact finite - sample p - values that are constructed using any test statistic. we propose a new method, the adaptive randomization test ( art ), that tackles the independence problem while allowing the data to be adaptively sampled. we first showcase the art in a particular multi - arm bandit problem known as the normal - mean model. under this setting, we theoretically characterize the powers of both the iid sampling procedure and the adaptive sampling procedure and empirically find that the art can uniformly outperform the crt that pulls all arms independently with equal probability. we also surprisingly find that the art can be more powerful than even the crt that uses an oracle iid sampling procedure when the signal is relatively strong. we believe that the proposed adaptive procedure is successful because it takes arms that may initially look like " fake " signals due to random chance and stabilizes them closer to " null " signals. we additionally showcase the art to a popular factorial survey design setting known as conjoint analysis. we find similar results through simulations and a recent application concerning the role of gender discrimination in political candidate evaluation. | arxiv:2205.02430 |
the aggressive spatial spectrum reuse ( ssr ) by network densification using smaller cells has successfully driven the wireless communication industry onward in the past decades. in our future journey toward ultra - dense networks ( udns ), a fundamental question needs to be answered. is there a limit to ssr? in other words, when we deploy thousands or millions of small cell base stations ( bss ) per square kilometer, is activating all bss on the same time / frequency resource the best strategy? in this paper, we present theoretical analyses to answer such question. in particular, we find that both the signal and interference powers become bounded in practical udns with a non - zero bs - to - ue antenna height difference and a finite ue density, which leads to a constant capacity scaling law. as a result, there exists an optimal ssr density that can maximize the network capacity. hence, the limit to ssr should be considered in the operation of future udns. | arxiv:1704.00399 |
out - of - town recommendation is designed for those users who leave their home - town areas and visit the areas they have never been to before. it is challenging to recommend point - of - interests ( pois ) for out - of - town users since the out - of - town check - in behavior is determined by not only the user ' s home - town preference but also the user ' s travel intention. besides, the user ' s travel intentions are complex and dynamic, which leads to big difficulties in understanding such intentions precisely. in this paper, we propose a travel - intention - aware out - of - town recommendation framework, named trainor. the proposed trainor framework distinguishes itself from existing out - of - town recommenders in three aspects. first, graph neural networks are explored to represent users ' home - town check - in preference and geographical constraints in out - of - town check - in behaviors. second, a user - specific travel intention is formulated as an aggregation combining home - town preference and generic travel intention together, where the generic travel intention is regarded as a mixture of inherent intentions that can be learned by neural topic model ( ntm ). third, a non - linear mapping function, as well as a matrix factorization method, are employed to transfer users ' home - town preference and estimate out - of - town poi ' s representation, respectively. extensive experiments on real - world data sets validate the effectiveness of the trainor framework. moreover, the learned travel intention can deliver meaningful explanations for understanding a user ' s travel purposes. | arxiv:2101.12555 |
idiomatic expressions have always been a bottleneck for language comprehension and natural language understanding, specifically for tasks like machine translation ( mt ). mt systems predominantly produce literal translations of idiomatic expressions as they do not exhibit generic and linguistically deterministic patterns which can be exploited for comprehension of the non - compositional meaning of the expressions. these expressions occur in parallel corpora used for training, but due to the comparatively high occurrences of the constituent words of idiomatic expressions in literal context, the idiomatic meaning gets overpowered by the compositional meaning of the expression. state of the art metaphor detection systems are able to detect non - compositional usage at word level but miss out on idiosyncratic phrasal idiomatic expressions. this creates a dire need for a dataset with a wider coverage and higher occurrence of commonly occurring idiomatic expressions, the spans of which can be used for metaphor detection. with this in mind, we present our english possible idiomatic expressions ( epie ) corpus containing 25206 sentences labelled with lexical instances of 717 idiomatic expressions. these spans also cover literal usages for the given set of idiomatic expressions. we also present the utility of our dataset by using it to train a sequence labelling module and testing on three independent datasets with high accuracy, precision and recall scores. | arxiv:2006.09479 |
knowledge of electric fields in the photosphere is required to calculate the electromagnetic energy flux through the photosphere and set up boundary conditions for data - driven magnetohydrodynamic ( mhd ) simulations of solar eruptions. recently, the pdfi _ ss method for inversions of electric fields from a sequence of vector magnetograms and doppler velocity measurements was improved to incorporate spherical geometry and a staggered - grid description of variables. the method was previously validated using synthetic data from anelastic mhd ( anmhd ) simulations. in this paper, we further validate the pdfi _ ss method, using approximately one - hour long mhd simulation data of magnetic flux emergence from the upper convection zone into the solar atmosphere. we reconstruct photospheric electric fields and calculate the poynting flux, and compare those to the actual values from the simulations. we find that the accuracy of the pdfi _ ss reconstruction is quite good during the emergence phase of the simulated ephemeral active region evolution and decreases during the shearing phase. analysing our results, we conclude that the more complex nature of the evolution ( compared to the previously studied anmhd case ) that includes the shearing evolution phase is responsible for the obtained accuracy decrease. | arxiv:2106.10579 |
this paper is a sequel to a paper by the author and marvin d. tretkoff ( reference [ 49 ] ), in which we showed the validity of a special case of a conjecture of green, griffths and kerr for certain families of calabi - yau manifolds over hermitian symmetric domains. these results are analogues of a celebrated theorem of th. schneider on the transcendence of values of the elliptic modular function, and its generalization to the context of abelian varieties by the author, shiga and wolfart. in the present paper, we apply related techniques to many of the examples of families of calabi - yau varieties with dense sets of cm fibers in the work of rohde, and in particular to borcea - voisin towers. our results fit into a broader context of transcendence theory for variations of hodge structure of higher weight. | arxiv:1407.2611 |
scalar non - standard interactions ( snsi ) in neutrinos can arise when a scalar mediator couples to both neutrinos and standard model fermions. this beyond the standard model ( bsm ) scenario is particularly interesting as the snsi contribution appears as a density - dependent perturbation to the neutrino mass, rather than appearing as a matter - induced potential, and the neutrino oscillation probabilities uniquely depend on the absolute neutrino masses. in this work, we show the complex dependence of the snsi contributions on the neutrino masses and discuss how the mass of the lightest neutrino would regulate any possible snsi contribution in both mass ordering scenarios. we derive the analytic expressions for neutrino oscillation probabilities, employing the cayley - hamilton theorem, in the presence of diagonal elements of snsi. the expressions are compact and shows explicit dependence on matter effects and the absolute neutrino masses. the analytic expressions calculated here allow us to obtain the dependence of the snsi contribution on mass terms of the form $ m _ 1 + m _ 2 $, $ m _ 2 - m _ 1 $, $ m _ 1c _ { 12 } ^ 2 + m _ 2s _ { 12 } ^ 2, $ $ m _ 1s _ { 12 } ^ 2 + m _ 2c _ { 12 } ^ 2 $, and $ m _ 3 $. we then explore the non - trivial impact of neutrino mass ordering on the snsi contribution. the dependence of the snsi contribution on the 3 $ \ nu $ parameters is then thoroughly explored using our analytic expressions. | arxiv:2410.05250 |
we are focusing on bound constrained global optimization problems, whose objective functions are computationally expensive black - box functions and have multiple local minima. the recently popular metric stochastic response surface ( msrs ) algorithm proposed by \ cite { regis2007srbf } based on adaptive or sequential learning based on response surfaces is revisited and further extended for better performance in case of higher dimensional problems. specifically, we propose a new way to generate the candidate points which the next function evaluation point is picked from according to the metric criteria, based on a new definition of distance, and prove the global convergence of the corresponding. correspondingly, a more adaptive implementation of msrs, named " so - sa ", is presented. " so - sa " is is more likely to perturb those most sensitive coordinates when generating the candidate points, instead of perturbing all coordinates simultaneously. numerical experiments on both synthetic problems and real problems demonstrate the advantages of our new algorithm, compared with many state of the art alternatives. } | arxiv:1410.6271 |
multi - agent path - finding ( mapf ) focuses on the collaborative planning of paths for multiple agents within shared spaces, aiming for collision - free navigation. conventional planning methods often overlook the presence of other agents, which can result in conflicts. in response, this article introduces the a $ ^ * _ + $ t algorithm, a distributed approach that improves coordination among agents by anticipating their positions based on their movement speeds. the algorithm also considers dynamic obstacles, assessing potential collisions with respect to observed speeds and trajectories, thereby facilitating collision - free path planning in environments populated by other agents and moving objects. it incorporates a risk layer surrounding both dynamic and static entities, enhancing its utility in real - world applications. each agent functions autonomously while being mindful of the paths chosen by others, effectively addressing the complexities inherent in multi - agent situations. the performance of a $ ^ * _ + $ t has been rigorously tested in the gazebo simulation environment and benchmarked against established approaches such as cbs, ecbs, and sipp. furthermore, the algorithm has shown competence in single - agent experiments, with results demonstrating its effectiveness in managing dynamic obstacles and affirming its practical relevance across various scenarios. | arxiv:2504.19593 |
optical coherence tomography ( oct ) is a non - invasive imaging modality which is widely used in clinical ophthalmology. oct images are capable of visualizing deep retinal layers which is crucial for early diagnosis of retinal diseases. in this paper, we describe a comprehensive open - access database containing more than 500 highresolution images categorized into different pathological conditions. the image classes include normal ( no ), macular hole ( mh ), age - related macular degeneration ( amd ), central serous retinopathy ( csr ), and diabetic retinopathy ( dr ). the images were obtained from a raster scan protocol with a 2mm scan length and 512x1024 pixel resolution. we have also included 25 normal oct images with their corresponding ground truth delineations which can be used for an accurate evaluation of oct image segmentation. in addition, we have provided a user - friendly gui which can be used by clinicians for manual ( and semi - automated ) segmentation. | arxiv:1812.07056 |
in this paper, we study on the one - plus - half monopole configuration in su ( 2 ) yang - mills - higgs theory when the $ \ phi $ - winding number, $ n $, runs from 2 to 4 and for a range of higgs coupling constant, $ \ lambda _ b \ leq \ lambda \ leq 40 $, where $ \ lambda _ b $ is the lower bound, below which no solution can be found. bifurcation and transition are observed for $ n > 2 $ when the higgs coupling constant is larger than some critical value $ \ lambda _ c $ and transitional value $ \ lambda _ t $, respectively. two different branches with energy higher than the fundamental solution are observed for both $ n = 3 $ and $ 4 $. we also observed a new branch with even higher energy for $ n = 4 $. unlike other branches which display transition behavior, the new branch corresponds to a full vortex - ring configuration. all the solutions possess finite energy. plots of magnetic charge density, higgs modulus and energy density are presented and analyzed. | arxiv:2107.04535 |
when estimating an effect of an action with a randomized or observational study, that study is often not a random sample of the desired target population. instead, estimates from that study can be transported to the target population. however, transportability methods generally rely on a positivity assumption, such that all relevant covariate patterns in the target population are also observed in the study sample. strict eligibility criteria, particularly in the context of randomized trials, may lead to violations of this assumption. two common approaches to address positivity violations are restricting the target population and restricting the relevant covariate set. as neither of these restrictions are ideal, we instead propose a synthesis of statistical and simulation models to address positivity violations. we propose corresponding g - computation and inverse probability weighting estimators. the restriction and synthesis approaches to addressing positivity violations are contrasted with a simulation experiment and an illustrative example in the context of sexually transmitted infection testing uptake. in both cases, the proposed synthesis approach accurately addressed the original research question when paired with a thoughtfully selected simulation model. neither of the restriction approaches were able to accurately address the motivating question. as public health decisions must often be made with imperfect target population information, model synthesis is a viable approach given a combination of empirical data and external information based on the best available knowledge. | arxiv:2303.01572 |
" michael jordans of math - u. s. student whizzes stun the cipher world ". u. s. news & world report. 131 ( 3 ) : 26. saul, mark ( 2003 ). " mathematics in a small place : notes on the mathematics of romania and bulgaria " ( pdf ). notices of the american mathematical society. 50 : 561 – 565. vakil, ravi ( 1997 ). a mathematical mosaic : patterns & problem solving. brendan kelly publishing. p. 288. isbn 978 - 1 - 895997 - 28 - 6. liu, andy ( 1998 ). chinese mathematics competitions and olympiads. amt publishing. isbn 1 - 876420 - 00 - 6. = = external links = = official imo web site archive to the imo 1959 – 2003 problems and solutions old central imo web site | https://en.wikipedia.org/wiki/International_Mathematical_Olympiad |
novel low dimensional quantum phenomena are expected at ( 110 ) laalo3 / srtio3 ( lao / sto ) interfaces after the quasi two dimensional electron gas similar to that of ( 001 ) lao / sto interfaces was found [ g. herranz et al., sci. rep. 2, 758 ( 2012 ) and a. annadi et al., nat. commun. 4, 1838 ( 2013 ) ]. here, two dimensional superconductivity of ( 110 ) lao / sto samples with a superconducting transition temperature of 184 mk is demonstrated based on systematical transport measurements. the two dimensional characteristic of the superconductivity is confirmed by analyzing the berezinskii - kosterlitz - thouless transition. the estimated superconductive thickness is about 18 nm. these features of superconductivity of ( 110 ) lao / sto interfaces are comparable to those of ( 001 ) lao / sto interfaces. this discovery may inspire a new round of upsurge on study of lao / sto interfaces. | arxiv:1409.5855 |
the piece of nestor vacuum chamber with the ceramic insertion for dc - monitor and rf - shields was simulated by using both transient and wake field solvers of cst studio suite. for a 6 mm gap between two rf - shields the contributions of the assembly considered to the longitudinal broadband ( bb ) impedance z / n and the loss factor kloss are 0. 71 ohm and 0. 21 v / pc, correspondingly. these estimates are the second largest after those of the rf - cavity that were obtained till now for the nestor ring components. contributions from a beam position monitor ( bpm ) are also obtained by simulation and compared with analytical estimates obtained earlier. we also present in the paper the frequency content of longitudinal impedance in the frequency range from 0 to 16 ghz for all ring components considered. | arxiv:1210.8274 |
though current cv models have been able to achieve high levels of accuracy on small - scale images classification dataset with hundreds or thousands of categories, many models become infeasible in computational or space consumption when it comes to large - scale dataset with more than 50, 000 categories. in this paper, we provide a viable solution for classifying large - scale species datasets using traditional cv techniques such as. features extraction and processing, bovw ( bag of visual words ) and some statistical learning technics like mini - batch k - means, svm which are used in our works. and then mixed with a neural network model. when applying these techniques, we have done some optimization in time and memory consumption, so that it can be feasible for large - scale dataset. and we also use some technics to reduce the impact of mislabeling data. we use a dataset with more than 50, 000 categories, and all operations are done on common computer with l 6gb ram and a cpu of 3. oghz. our contributions are : 1 ) analysis what problems may meet in the training processes, and presents several feasible ways to solve these problems. 2 ) make traditional cv models combined with neural network models provide some feasible scenarios for training large - scale classified datasets within the constraints of time and spatial resources. | arxiv:2007.13072 |
we formulate the next - to - leading order nuclear effective field theory without pions in the two - nucleon sector on a spatial lattice, and investigate nonperturbative renormalization group flows in the strong coupling region by diagonalizing the hamiltonian numerically. the cutoff ( proportional to the inverse of the lattice constant ) dependence of the coupling constants is obtained by changing the lattice constant with the binding energy and the asymptotic normalization constant for the groundstate being fixed. we argue that the critical line can be obtained by looking at the finite - size dependence of the groundstate energy. we determine the relevant operator and locate the nontrivial fixed point, as well as the physical flow line corresponding to the deuteron in the two - dimensional plane of dimensionless coupling constants. it turns out that the location of the nontrivial fixed point is very close to the one obtained by the corresponding analytic calculation, but the relevant operator is quite different. | arxiv:1604.02882 |
the paper reviews methods used to study the electronic and structural properties of silicon / insulator interfaces. methodological approaches to study the interface states and charge trapping in the oxide are considered. an overview of archetypical structural defects of the si / sio2 interface is given. | arxiv:1709.01917 |
dialogue state tracking ( dst ) is a process to estimate the distribution of the dialogue states as a dialogue progresses. recent studies on constrained markov bayesian polynomial ( cmbp ) framework take the first step towards bridging the gap between rule - based and statistical approaches for dst. in this paper, the gap is further bridged by a novel framework - - recurrent polynomial network ( rpn ). rpn ' s unique structure enables the framework to have all the advantages of cmbp including efficiency, portability and interpretability. additionally, rpn achieves more properties of statistical approaches than cmbp. rpn was evaluated on the data corpora of the second and the third dialog state tracking challenge ( dstc - 2 / 3 ). experiments showed that rpn can significantly outperform both traditional rule - based approaches and statistical approaches with similar feature set. compared with the state - of - the - art statistical dst approaches with a lot richer features, rpn is also competitive. | arxiv:1507.03934 |
we carry out a systematic search campaign for wide companions of exoplanet host stars to study their multiplicity and its influence on the long - term stability and the orbital parameters of the exoplanets. we have already found 6 wide companions, raising the number of confirmed binaries among the exoplanet host stars to 20 systems. we have also searched for wide companions of gl86, the first known exoplanet host star with a white dwarf companion. our sofi / ntt observations are sensitive to substellar companions with a minimum - mass of 35 mjup and clearly rule out further stellar companions with projected separations between 40 and 670au. | arxiv:astro-ph/0512105 |
we investigate the emergence of hyperons in black - hole - forming failed supernovae, which are caused by the dynamical collapse of nonrotating massive stars. we perform neutrino - radiation hydrodynamical simulations in general relativity adopting realistic hyperonic equation - of - state ( eos ). attractive and repulsive cases are examined for the potential of \ sigma \ hyperons. since hyperons soften the eos, they shorten the time interval from the bounce to black hole formation, which corresponds to the duration of neutrino emission. this effect is larger for the attractive case than the repulsive case because \ sigma \ hyperons appear more easily. in addition, we investigate the impacts of pions to find that they also promotes the recollapse towards the black hole formation. | arxiv:1111.2900 |
optically addressable solid - state spins have been proposed as robust radiofrequency ( rf ) - optical transducers sensitive to a specific rf frequency tuned by an external static magnetic field, but often require precise field alignment with the system ' s symmetry axis. here we introduce an isotropic solid - state spin system, namely weakly coupled spin pairs in hexagonal boron nitride ( hbn ), which acts as an rf - optical transducer independent of the direction of the tuning magnetic field, allowing greatly simplified experimental design. using this platform, we first demonstrate a single - frequency rf receiver with frequency tunability from 0. 1 to 19 ghz. we next demonstrate an instantaneous wideband rf spectrum analyser by applying a magnetic field gradient to encode rf frequency into spatial position. finally, we utilise the spectrum analyser to detect free - space - transmitted rf signals matching the strength and frequency of typical wi - fi signals. this work exemplifies the unique capabilities of isotropic spins in hbn to operate as rf sensors, while circumventing the challenging requirement of precisely aligned magnetic fields facing conventional solid - state spins. | arxiv:2410.00430 |
a schroedinger picture analysis of time dependent quantum oscillators, in a manner of guth and pi, clearly identifies two physical mechanisms for possible decoherence of vacuum fluctuations in early universe : turning of quantum oscillators upside - down, and rapid squeezing of upside - right oscillators so that certain squeezing factor diverges. in inflationary cosmology the former mechanism explains the stochastic evolution of light inflatons and the classical nature of density perturbations in most of inflationary models, while the later one is responsible for the classical evolution of relatively heavy fields, with masses in a narrow range above the hubble parameter : 2 < ( m / h _ 0 ) ^ 2 < 9 / 4. the same method may be applied to study of the decoherence of quantum fluctuations in any robertson - walker cosmology. | arxiv:gr-qc/9706016 |
this manuscript concerns the dynamics of non - isentropic compressible euler equations in a physical vacuum. we establish the hadamard - style local well - posedness within low - regularity weighted sobolev spaces, demonstrating existence, uniqueness, and continuous dependence on initial data. additionally, we provide sharp a priori energy estimates and continuation criteria. the approach is based on the framework of eulerian coordinates. | arxiv:2411.17153 |
we construct a classifier which attains the rate of convergence $ \ log n / n $ under sparsity and margin assumptions. an approach close to the one met in approximation theory for the estimation of function is used to obtain this result. the idea is to develop the bayes rule in a fundamental system of $ l ^ 2 ( [ 0, 1 ] ^ d ) $ made of indicator of dyadic sets and to assume that coefficients, equal to $ - 1, 0 { or } 1 $, belong to a kind of $ l ^ 1 - $ ball. this assumption can be seen as a sparsity assumption, in the sense that the proportion of coefficients non equal to zero decreases as " frequency " grows. finally, rates of convergence are obtained by using an usual trade - off between a bias term and a variance term. | arxiv:math/0607439 |
while ngc 1514 is an elliptical, but complex, planetary nebula at optical wavelengths, it was discovered to have a pair of infrared - bright, axisymmetric rings contained within its faint outer shell during the course of the wise all - sky survey. we have obtained jwst mid - infrared imaging and spectroscopy of the nebula through the use of simultaneous observations with the miri imager and medium resolution spectrometer, selecting the f770w, f1280w, and f2550w filters to match each of the mrs ' s three grating positions. these observations show that the rings are clearly resolved and relatively distinct structures, with both filamentary and clumpy detail throughout. there is also cloud - like material that has a turbulent appearance in the interior of the rings, particularly at the longest wavelengths, and faint ejecta - like structures just outside the ring boundaries. despite their brightness, the emission from the rings within the three imager passbands is shown to be dominated by thermal emission from very small grains, not line emission from atomic hydrogen or forbidden atomic lines, shocked molecular hydrogen, or pahs. the doppler velocities derived from the two brightest emission lines in the rings, however, suggest that the material from which the rings were formed was ejected during an early period of very heavy mass loss from the pn progenitor, then shaped by asymmetrical fast winds from the central binary pair. | arxiv:2502.21281 |
we present a commonsense, qualitative model for the semantic grounding of embodied visuo - spatial and locomotive interactions. the key contribution is an integrative methodology combining low - level visual processing with high - level, human - centred representations of space and motion rooted in artificial intelligence. we demonstrate practical applicability with examples involving object interactions, and indoor movement. | arxiv:1709.05293 |
to effectively retrieve objects from large corpus with high accuracy is a challenge task. in this paper, we propose a method that propagates visual feature level similarities on a markov random field ( mrf ) to obtain a high level correspondence in image space for image pairs. the proposed correspondence between image pair reflects not only the similarity of low - level visual features but also the relations built through other images in the database and it can be easily integrated into the existing bag - of - visual - words ( bow ) based systems to reduce the missing rate. we evaluate our method on the standard oxford - 5k, oxford - 105k and paris - 6k dataset. the experiment results show that the proposed method significantly improves the retrieval accuracy on three datasets and exceeds the current state - of - the - art retrieval performance. | arxiv:1312.7085 |
this paper regards the problem of optimally placing unreliable sensors in a one - dimensional environment. we assume that sensors can fail with a certain probability and we minimize the expected maximum distance from any point in the environment to the closest active sensor. we provide a computational method to find the optimal placement and we estimate the relative quality of equispaced and random placements. we prove that the former is asymptotically equivalent to the optimal placement when the number of sensors goes to infinity, with a cost ratio converging to 1, while the cost of the latter remains strictly larger. | arxiv:1404.7711 |
we develop a scheme for the computation of the full - counting statistics of transport described by markovian master equations with an arbitrary time dependence. it is based on a hierarchy of generalized density operators, where the trace of each operator yields one cumulant. this direct relation offers a better numerical efficiency than the equivalent number - resolved master equation. the proposed method is particularly useful for conductors with an elaborate time - dependence stemming, e. g., from pulses or combinations of slow and fast parameter switching. as a test bench for the evaluation of the numerical stability, we consider time - independent problems for which the full - counting statistics can be computed by other means. as applications, we study cumulants of higher order for two time - dependent transport problems of recent interest, namely steady - state coherent transfer by adiabatic passage and landau - zener - st \ " uckelberg - majorana interference in an open double quantum dot. | arxiv:1608.07970 |
traditional evaluations of multimodal large language models ( llms ) have been limited by their focus on single - image reasoning, failing to assess crucial aspects like contextual understanding, reasoning stability, and uncertainty calibration. this study addresses these limitations by introducing a novel benchmark that integrates multi - image reasoning tasks with rejection - based evaluation and positional bias detection. to evaluate these dimensions, we further introduce entropy as a novel metric for quantifying reasoning consistency across reordered answer variants. we applied this benchmark to assess grok 3, chatgpt - 4o, chatgpt - o1, gemini 2. 0 flash experimental, deepseek janus models, qwen2. 5 - vl - 72b - instruct, qvq - 72b - preview, and pixtral 12b across eight visual reasoning tasks, including difference spotting and diagram interpretation. our findings reveal chatgpt - o1 leading in overall accuracy ( 82. 5 \ % ) and rejection accuracy ( 70. 0 \ % ), closely followed by gemini 2. 0 flash experimental ( 70. 8 \ % ). qvq - 72b - preview demonstrated superior rejection accuracy ( 85. 5 \ % ). notably, pixtral 12b ( 51. 7 \ % ) showed promise in specific domains, while janus models exhibited challenges in bias and uncertainty calibration, reflected in low rejection accuracies and high entropy scores. high entropy scores in janus models ( janus 7b : 0. 8392, janus 1b : 0. 787 ) underscore their susceptibility to positional bias and unstable reasoning, contrasting with the low entropy and robust reasoning of chatgpt models. the study further demonstrates that model size is not the sole determinant of performance, as evidenced by grok 3 underperformance despite its substantial parameter count. by employing multi - image contexts, rejection mechanisms, and entropy - based consistency metrics, this benchmark sets a new standard for evaluating multimodal llms, enabling a more robust and reliable assessment of next - generation ai systems. | arxiv:2502.16428 |
we study exclusive b decays to final states containing a charmed baryon within the pole model framework. since the strong coupling for $ \ lambda _ b \ bar b n $ is larger than that for $ \ sigma _ b \ bar bn $, the two - body charmful decay $ b ^ - \ to \ sigma _ c ^ 0 \ bar p $ has a rate larger than $ \ bar b ^ 0 \ to \ lambda _ c ^ + \ bar p $ as the former proceeds via the $ \ lambda _ b $ pole while the latter via the $ \ sigma _ b $ pole. by the same token, the three - body decay $ \ bar b ^ 0 \ to \ sigma _ c ^ { + + } \ bar p \ pi ^ - $ receives less baryon - pole contribution than $ b ^ - \ to \ lambda _ c ^ + \ bar p \ pi ^ - $. however, because the important charmed - meson pole diagrams contribute constructively to the former and destructively to the latter, $ \ sigma _ c ^ { + + } \ bar p \ pi ^ - $ has a rate slightly larger than $ \ lambda _ c ^ + \ bar p \ pi ^ - $. it is found that one quarter of the $ b ^ - \ to \ lambda _ c ^ + \ bar p \ pi ^ - $ rate comes from the resonant contributions. we discuss the decays $ \ bar b ^ 0 \ to \ sigma _ c ^ 0 \ bar p \ pi ^ + $ and $ b ^ - \ to \ sigma _ c ^ 0 \ bar p \ pi ^ 0 $ and stress that they are not color suppressed even though they can only proceed via an internal w emission. | arxiv:hep-ph/0210275 |
ground state properties of spinless, extended falicov - kimball model ( fkm ) on a finite size triangular lattice with orbital magnetic field normal to the lattice are studied using numerical diagonalization and monte - carlo simulation methods. we show that the ground state configurations of localized electrons strongly depend on the magnetic field. magnetic field induces a metal to insulator transition accompanied by segregated phase to an ordered regular phase except at density $ n _ f = 1 / 2 $ of localized electrons. it is proposed that magnetic field can be used as a new tool to produce segregated phase which was otherwise accessible only either with correlated hopping or with large on - site interactions. | arxiv:1607.05240 |
we investigate the quasiperiodic crystal ( las ) 1. 196 ( vs2 ) by angle and time resolved photoemission spectroscopy. the dispersion of electronic states is in qualitative agreement with band structure calculated for the vs2 slab without the incommensurate distortion. nonetheless, the spectra display a temperature dependent pseudogap instead of quasiparticles crossing. the sudden photoexcitation at 50 k induces a partial filling of the electronic pseudogap within less than 80 fs. the electronic energy flows into the lattice modes on a comparable timescale. we attribute this surprisingly short timescale to a very strong electron - phonon coupling to the incommensurate distortion. this result sheds light on the electronic localization arising in aperiodic structures and quasicrystals. | arxiv:1301.6888 |
by extending the classical analysis techniques due to samokish, faddeev and faddeeva, and longsine and mccormick among others, we prove the convergence of preconditioned steepest descent with implicit deflation ( psd - id ) method for solving hermitian - definite generalized eigenvalue problems. furthermore, we derive a nonasymptotic estimate of the rate of convergence of the \ psdid method. we show that with the proper choice of the shift, the indefinite shift - and - invert preconditioner is a locally accelerated preconditioner, and is asymptotically optimal that leads to superlinear convergence. numerical examples are presented to verify the theoretical results on the convergence behavior of the \ psdid method for solving ill - conditioned hermitian - definite generalized eigenvalue problems arising from electronic structure calculations. while rigorous and full - scale convergence proofs of preconditioned block steepest descent methods in practical use still largely eludes us, we believe the theoretical results presented in this paper sheds light on an improved understanding of the convergence behavior of these block methods. | arxiv:1605.09109 |
fast radio bursts ( frbs ) are millisecond transient astrophysical phenomena and bright at radio frequencies. the emission mechanism, however, remains unsolved yet. one scenario is a coherent emission associated with the magnetar flares and resulting relativistic shock waves. here, we report unprecedentedly large - scale simulations of relativistic magnetized ion - electron shocks, showing that strongly linear - polarized electromagnetic waves are excited. the kinetic energy conversion to the emission is so efficient that the wave amplitude is responsible for the brightness. we also find a polarization angle swing reflecting shock front modulation, implicating the polarization property of some repeating frbs. the results support the shock scenario as an origin of the frbs. | arxiv:2311.18487 |
the glitch signatures in $ r _ { 010 } $ for f - type stars ( higher amplitude and period of the oscillatory component ) are very different from those of g - type stars. the aim of this work is to analyse the signatures of these glitches and understand the origin of the differences in these signatures between g - type and f - type stars. we fit the glitch signatures in the frequencies, second differences, and $ r _ { 010 } $ ratios while assuming either a sinusoidal variation or a more complex expression. the fit provides the acoustic depth, and hence the position, of the bottom of the convective envelope for nine \ textit { kepler } stars and the sun. we find that for f - type stars, the most commonly used fitting expressions for the glitch of the bottom of the convective envelope provide different measurements of the position of the bottom of the convective envelope for the three seismic indicators, while it is not the case for g - type stars. when adding an additional term in the fitting expression with twice the acoustic depth of the standard term ( a contribution that accounts for the highly non - sinusoidal shape of the signature in the $ r _ { 010 } $ ratios ), we find better agreement between the three seismic indicators and with the prediction of stellar evolution models. while the origin of this additional term is not yet understood, this may be an indication that the transition between the convective envelope and the underlying radiative zone is different for g - and f - type stars. this outcome brings new insight into the physics in these regions. | arxiv:2412.15099 |
abstraction is one of the most important strategies for dealing with the state space explosion problem in model checking. in the abstract model, the state space is largely reduced, however, a counterexample found in such a model may not be a real counterexample in the concrete model. accordingly, the abstract model needs to be further refined. how to check whether or not a reported counterexample is spurious is a key problem in the abstraction - refinement loop. in this paper, a formal definition for spurious path is given. based on it, efficient algorithms for detecting spurious counterexamples are proposed. | arxiv:1109.5506 |
we develop precise formulation for the effects of vacuum polarization near a pointlike source with a zero - range ( $ \ delta $ - like ) potential in three spatial dimensions. there are different ways of introducing $ \ delta $ - interaction in the framework of quantum theory. we discuss the approach based on the concept of self - adjoint extensions of densely defined symmetric operators. within this approach we consider the real massive scalar field in three - dimensional euclidean space with a single extracted point. appropriate boundary conditions imposed at this point enable one to consider all self - adjoint extensions of $ - \ delta $ as operators which can describe a pointlike source with a zero - range potential. in this framework we compute the renormalized vacuum expectation value of the field square $ \ langle \ phi ^ { 2 } ( x ) \ rangle _ { \ rm ren } $ and the renormalized vacuum average of the scalar - field ' s energy - momentum tensor $ \ langle t _ { \ mu \ nu } ( x ) \ rangle _ { \ rm ren } $. asymptotic cases are discussed in detail. | arxiv:2405.19502 |
autonomous agents that operate in the real world must often deal with partial observability, which is commonly modeled as partially observable markov decision processes ( pomdps ). however, traditional pomdp models rely on the assumption of complete knowledge of the observation source, known as fully observable data association. to address this limitation, we propose a planning algorithm that maintains multiple data association hypotheses, represented as a belief mixture, where each component corresponds to a different data association hypothesis. however, this method can lead to an exponential growth in the number of hypotheses, resulting in significant computational overhead. to overcome this challenge, we introduce a pruning - based approach for planning with ambiguous data associations. our key contribution is to derive bounds between the value function based on the complete set of hypotheses and the value function based on a pruned - subset of the hypotheses, enabling us to establish a trade - off between computational efficiency and performance. we demonstrate how these bounds can both be used to certify any pruning heuristic in retrospect and propose a novel approach to determine which hypotheses to prune in order to ensure a predefined limit on the loss. we evaluate our approach in simulated environments and demonstrate its efficacy in handling multi - modal belief hypotheses with ambiguous data associations. | arxiv:2303.02139 |
we report on the superconductivity in ternary transition metal tellurides ta2pd3te5 and nb2pd3te5, which have a one - dimensional crystal structure. single - crystalline and polycrystalline samples of ta2pd3te5 show nonmetallic electron conduction, while ti or w doping results in metallic behavior with a bulk superconducting transition at 2 - 4 k. in contrast, the polycrystalline samples of nb2pd3te5, which are found to be isostructural to ta2pd3te5, show a bulk superconducting transition at 3. 3 k. the crystal structure and physical properties of ta2pd3te5 and nb2pd3te5 are also discussed in comparison with a candidate excitonic insulator ta2nise5. | arxiv:2105.01886 |
this paper proposes a subspace decomposition method based on an over - complete dictionary in sparse representation, called " sparse signal subspace decomposition " ( or 3sd ) method. this method makes use of a novel criterion based on the occurrence frequency of atoms of the dictionary over the data set. this criterion, well adapted to subspace - decomposition over a dependent basis set, adequately re ects the intrinsic characteristic of regularity of the signal. the 3sd method combines variance, sparsity and component frequency criteria into an unified framework. it takes benefits from using an over - complete dictionary which preserves details and from subspace decomposition which rejects strong noise. the 3sd method is very simple with a linear retrieval operation. it does not require any prior knowledge on distributions or parameters. when applied to image denoising, it demonstrates high performances both at preserving fine details and suppressing strong noise. | arxiv:1610.08813 |
we study incoherently coupled two - frequency pulse compounds in waveguides with single zero - dispersion and zero - nonlinearity points. in such waveguides, supported by a negative nonlinearity, soliton dynamics can be obtained even in domains of normal dispersion. we demonstrate trapping of weak pulses by solitary - wave wells, forming nonlinear - photonics meta - atoms, and molecule - like bound - states of pulses. we study the impact of raman effect on these pulse compounds, finding that, depending on the precise subpulse configuration, they decelerate, accelerate, or are completely unaffected. our results extend the range of systems in which two - frequency pulse compounds can be expected to exist and demonstrate further unique and unexpected behavior. | arxiv:2211.00530 |
in this paper the running average of a subordinator with a tempered stable distribution is considered. we investigate a family of previously unexplored infinite - activity subordinators induced by the probability distribution of the running average process and determine their jump intensity measures. special cases including gamma processes and inverse gaussian processes are discussed. then we derive easily implementable formulas for the distribution functions, cumulants, and moments, as well as provide explicit estimates for their asymptotic behaviors. numerical experiments are conducted for illustrating the applicability and efficiency of the proposed formulas. two important extensions of the running average process and its equi - distributed subordinator are examined with concrete applications to structural degradation modeling and financial derivatives pricing, where their advantages relative to several existing models are highlighted together with the mention of euler discretization and compound poisson approximation techniques. | arxiv:2009.02583 |
the need for analytic continuation arises frequently in the context of inverse problems. notwithstanding the uniqueness theorems, such problems are notoriously ill - posed without additional regularizing constraints. we consider several analytic continuation problems with typical global boundedness constraints that restore well - posedness. we show that all such problems exhibit a power law precision deterioration as one moves away from the source of data. in this paper we demonstrate the effectiveness of our general hilbert space - based approach for determining these exponents. the method identifies the " worst case " function as a solution of a linear integral equation of fredholm type. in special geometries, such as the circular annulus or upper half - plane this equation can be solved explicitly. the obtained solution in the annulus is then used to determine the exact power law exponent for the analytic continuation from an interval between the foci of an ellipse to an arbitrary point inside the ellipse. our formulas are consistent with results obtained in prior work in those special cases when such exponents have been determined. | arxiv:1907.13325 |
most diffuse baryons, including the circumgalactic medium ( cgm ) surrounding galaxies and the intergalactic medium ( igm ) in the cosmic web, remain unmeasured and unconstrained. fast radio bursts ( frbs ) offer an unparalleled method to measure the electron dispersion measures ( dms ) of ionized baryons. their distribution can resolve the missing baryon problem, and constrain the history of feedback theorized to impart significant energy to the cgm and igm. we analyze the cosmology and astrophysics in machine learning ( camel ) simulations, using three suites : illustristng, simba, and astrid, each varying 6 parameters ( 2 cosmological & 4 astrophysical feedback ), for a total of 183 distinct simulation models. we find significantly different predictions between the fiducial models of the suites, owing to their different implementations of feedback. simba exhibits the strongest feedback, leading to the smoothest distribution of baryons, reducing the sightline - to - sightline variance in dms between z = 0 - 1. astrid has the weakest feedback and the largest variance. we calculate frb cgm measurements as a function of galaxy impact parameter, with simba showing the weakest dms due to aggressive agn feedback and astrid the strongest. within each suite, the largest differences are due to varying agn feedback. illustristng shows the most sensitivity to supernova feedback, but this is due to the change in the agn feedback strengths, demonstrating that black holes, not stars, are most capable of redistributing baryons in the igm and cgm. we compare our statistics directly to recent observations, paving the way for the use of frbs to constrain the physics of galaxy formation and evolution. | arxiv:2403.02313 |
we show that the nonequilibrium dynamics of systems with many interacting elements located on a small - world network can be much slower than on regular networks. as an example, we study the phase ordering dynamics of the ising model on a watts - strogatz network, after a quench in the ferromagnetic phase at zero temperature. in one and two dimensions, small - world features produce dynamically frozen configurations, disordered at large length scales, analogous of random field models. this picture differs from the common knowledge ( supported by equilibrium results ) that ferromagnetic short - cuts connections favor order and uniformity. we briefly discuss some implications of these results regarding the dynamics of social changes. | arxiv:cond-mat/0210352 |
ranking is one of the most fundamental problems in machine learning with applications in many branches of computer science such as : information retrieval systems, recommendation systems, machine translation and computational biology. ranking objects based on possibly conflicting preferences is a central problem in voting research and social choice theory. in this paper we present a new simple combinatorial ranking algorithm adapted to the preference - based setting. we apply this new algorithm to the well - known scenario where the edges of the preference tournament are determined by the majority - voting model. it outperforms existing methods when it cannot be assumed that there exists global ranking of good enough quality and applies combinatorial techniques that havent been used in the ranking context before. performed experiments show the superiority of the new algorithm over existing methods, also over these that were designed to handle heavily perturbed statistics. by combining our techniques with those presented in \ cite { mohri }, we obtain a purely combinatorial algorithm that answers correctly most of the queries in the heterogeneous scenario, where the preference tournament is only locally of good quality but is not necessarily pseudotransitive. as a byproduct of our methods, we obtain the algorithm solving clustering problem for the directed planted partition model. to the best of our knowledge, it is the first purely combinatorial algorithm tackling this problem. | arxiv:1504.01118 |
model extraction emerges as a critical security threat with attack vectors exploiting both algorithmic and implementation - based approaches. the main goal of an attacker is to steal as much information as possible about a protected victim model, so that he can mimic it with a substitute model, even with a limited access to similar training data. recently, physical attacks such as fault injection have shown worrying efficiency against the integrity and confidentiality of embedded models. we focus on embedded deep neural network models on 32 - bit microcontrollers, a widespread family of hardware platforms in iot, and the use of a standard fault injection strategy - safe error attack ( sea ) - to perform a model extraction attack with an adversary having a limited access to training data. since the attack strongly depends on the input queries, we propose a black - box approach to craft a successful attack set. for a classical convolutional neural network, we successfully recover at least 90 % of the most significant bits with about 1500 crafted inputs. these information enable to efficiently train a substitute model, with only 8 % of the training dataset, that reaches high fidelity and near identical accuracy level than the victim model. | arxiv:2308.16703 |
the cangaroo - ii telescope observed sub - tev gamma - ray emission from the nearby starburst galaxy ngc 253. the emission region was extended with a radial size of 0. 3 - 0. 6 degree. on the contrary, h. e. s. s could not confirm this emission and gave upper limits at the level of the cangaroo - ii flux. in order to resolve this discrepancy, we analyzed new observational results for ngc 253 by cangaroo - iii and also assessed the results by cangaroo - ii. observation was made with three telescopes of the cangaroo - iii in october 2004. we analyzed three - fold coincidence data by the robust fisher discriminant method to discriminate gamma ray events from hadron events. the result by the cangaroo - iii was negative. the upper limit of gamma ray flux was 5. 8 % crab at 0. 58 tev for point - source assumption. in addition, the significance of the excess flux of gamma - rays by the cangaroo - ii was lowered to less than 4 sigma after assessing treatment of malfunction of photomultiplier tubes. | arxiv:astro-ph/0610268 |
is subsequently freeze - dried to remove the dispersed water and the solvent, thus leaving a solidified, porous polymeric structure. while emulsification and freeze - drying allow for a faster preparation when compared to scpl ( since it does not require a time - consuming leaching step ), it still requires the use of solvents. moreover, pore size is relatively small and porosity is often irregular. freeze - drying by itself is also a commonly employed technique for the fabrication of scaffolds. in particular, it is used to prepare collagen sponges : collagen is dissolved into acidic solutions of acetic acid or hydrochloric acid that are cast into a mold, frozen with liquid nitrogen and then lyophilized. = = = = thermally induced phase separation = = = = similar to the previous technique, the tips phase separation procedure requires the use of a solvent with a low melting point that is easy to sublime. for example, dioxane could be used to dissolve polylactic acid, then phase separation is induced through the addition of a small quantity of water : a polymer - rich and a polymer - poor phase are formed. following cooling below the solvent melting point and some days of vacuum - drying to sublime the solvent, a porous scaffold is obtained. liquid - liquid phase separation presents the same drawbacks of emulsification / freeze - drying. = = = = electrospinning = = = = electrospinning is a highly versatile technique that can be used to produce continuous fibers ranging in diameter from a few microns to a few nanometers. in a typical electrospinning set - up, the desired scaffold material is dissolved within a solvent and placed within a syringe. this solution is fed through a needle and a high voltage is applied to the tip and to a conductive collection surface. the buildup of electrostatic forces within the solution causes it to eject a thin fibrous stream towards the oppositely charged or grounded collection surface. during this process the solvent evaporates, leaving solid fibers leaving a highly porous network. this technique is highly tunable, with variation to solvent, voltage, working distance ( distance from the needle to collection surface ), flow rate of solution, solute concentration, and collection surface. this allows for precise control of fiber morphology. on a commercial level however, due to scalability reasons, there are 40 or sometimes 96 needles involved operating at once. the bottle - necks in such set | https://en.wikipedia.org/wiki/Tissue_engineering |
in data analysis, latent variables play a central role because they help provide powerful insights into a wide variety of phenomena, ranging from biological to human sciences. the latent tree model, a particular type of probabilistic graphical models, deserves attention. its simple structure - a tree - allows simple and efficient inference, while its latent variables capture complex relationships. in the past decade, the latent tree model has been subject to significant theoretical and methodological developments. in this review, we propose a comprehensive study of this model. first we summarize key ideas underlying the model. second we explain how it can be efficiently learned from data. third we illustrate its use within three types of applications : latent structure discovery, multidimensional clustering, and probabilistic inference. finally, we conclude and give promising directions for future researches in this field. | arxiv:1402.0577 |
let \ sigma be a minimal submanifold of \ r ^ { n + m } that can be represented as the graph of a smooth map f : \ r ^ n - - > \ r ^ m. we apply a formula we derived in the study of mean curvature flow to obtain conditions under which \ sigma must be an affine subspace. our result covers all known ones in the general case. the conditions are stated in terms of the singular values of $ df $. | arxiv:math/0202011 |
we present the fundamental equation for a system and for a process, and by considering irreversibility within the system, we show that the lost work concept emerges naturally from the formalism. we then argue that if irreversibility is considered within the surroundings the lost work becomes what is known as exergy. therefore, lost work and exergy are two views of the same concept, which in turn integrates a broader and more fundamental concept : entropy generation. it is our opinion that the clarification of the meanings of lost work and exergy, as well as the discussion that leads to an understanding of their differences and similarities, has not received the attention in the literature that it deserves. this paper fills that gap, and it is hoped that the discussion of these two concepts here will be useful for both students and teachers. | arxiv:2306.04060 |
in this thesis, we investigated some properties of ( left ) near fields and derived some results. we are focusing on $ d ( \ alpha, \ beta ) $ which is the generalized set of distributive elements of a nearfield. in particular, we investigated some conditions on $ \ alpha, \ beta, \ alpha + \ beta $ for $ d ( \ alpha, \ beta ) $ to be a subfield of $ \ mathbb { f } _ { q ^ { n } } $. in nearfield theory the two distributive laws can not hold at the same time. so in term of left nearfield and near - ring, the right distributivity does not hold and to solve the problem, we defined a set of all distributive elements called $ d ( r ) $. | arxiv:2305.13319 |
when a vehicle drives on the road, its behaviors will be affected by surrounding vehicles. prediction and decision should not be considered as two separate stages because all vehicles make decisions interactively. this paper constructs the multi - vehicle driving scenario as a non - zero - sum game and proposes a novel game control framework, which consider prediction, decision and control as a whole. the mutual influence of interactions between vehicles is considered in this framework because decisions are made by nash equilibrium strategy. to efficiently obtain the strategy, adp, a model - based reinforcement learning method, is used to solve coupled hamilton - jacobi - bellman equations. driving performance is evaluated by tracking, efficiency, safety and comfort indices. experiments show that our algorithm could drive perfectly by directly controlling acceleration and steering angle. vehicles could learn interactive behaviors such as overtaking and pass. in summary, we propose a non - zero - sum game framework for modeling multi - vehicle driving, provide an effective way to solve the nash equilibrium driving strategy, and validate at non - signalized intersections. | arxiv:2302.03958 |
boyer, gordon, and watson have conjectured that an irreducible rational homology 3 - sphere is an l - space if and only if its fundamental group is not left - orderable. since dehn surgeries on knots in $ s ^ 3 $ can produce large families of l - spaces, it is natural to examine the conjecture on these 3 - manifolds. greene, lewallen, and vafaee have proved that all 1 - bridge braids are l - space knots. in this paper, we consider three families of 1 - bridge braids. first we calculate the knot groups and peripheral subgroups. we then verify the conjecture on the three cases by applying the criterion developed by christianson, goluboff, hamann, and varadaraj, when they verified the same conjecture for certain twisted torus knots and generalized the criteria of clay and watson and of ichihara and temma. | arxiv:1711.11389 |
we perform a minisuperspace analysis of an information - theoretic nonlinear wheeler - dewitt ( wdw ) equation for de sitter universes. the nonlinear wdw equation, which is in the form of a difference - differential equation, is transformed into a pure difference equation for the probability density by using the current conservation constraint. in the present study we observe some new features not seen in our previous approximate investigation, such as a nonzero minimum and maximum allowable size to the quantum universe : an examination of the effective classical dynamics supports the interpretation of a bouncing universe. the studied model suggests implications for the early universe, and plausibly also for the future of an ongoing accelerating phase of the universe. | arxiv:1107.3347 |
we consider some problems concerning the maximum number of ( strong ) dominating sets in a regular graph, and their weighted analogues. our primary tool is shearer ' s entropy lemma. these techniques extend to a reasonably broad class of graph parameters enumerating vertex colorings satisfying conditions on the multiset of colors appearing in ( closed ) neighborhoods. we also generalize further to enumeration problems for what we call existence homomorphisms. here our results are substantially less complete, though we do solve some natural problems. | arxiv:1503.00998 |
the radiative correction to the lamb shift of order $ \ alpha ^ { 2 } ( z \ alpha ) ^ 5m $ induced by the light by light scattering insertion in external photons is obtained. the new contribution turns out to be equal to $ - 0. 122 ( 2 ) \ alpha ^ 2 ( z \ alpha ) ^ 5 / ( \ pi n ^ 3 ) ( m _ r / m ) ^ 3m $. combining this contribution with our previous results we obtain the complete correction of order $ \ alpha ^ { 2 } ( z \ alpha ) ^ 5m $ induced by all diagrams with closed electron loops. this correction is $ 37. 3 ( 1 ) $ khz and $ 4. 67 ( 1 ) $ khz for the $ 1s $ - and $ 2s $ - states in hydrogen, respectively. | arxiv:hep-ph/9402304 |
a search for the resonant production of high mass photon pairs associated with a leptonic or hadronic system has been performed using a total data sample of 25. 7 pb ^ - 1 taken at centre - of - mass energies between 130 gev and 172 gev with the opal detector at lep. the observed number of events is consistent with the expected number from standard model processes. the observed candidates are combined with search results from sqrt { s } ~ m _ z to place limits on br ( h ^ 0 - > gamma gamma ) within the standard model for higgs boson masses up to 77 gev, and on the production cross section of any scalar resonance decaying into di - photons. upper limits on br ( h ^ 0 - > gamma gamma ) x sigma ( e ^ + e ^ - - > h ^ 0 z ^ 0 ) of 290 - 830 fb are obtained over 40 < m _ h < 160 gev. type - i two - higgs - doublet scalars which couple only to gauge bosons are ruled out up to a mass of 76. 5 gev at the 95 % confidence level. | arxiv:hep-ex/9709022 |
recently, substantial progress has been made in text ranking based on pretrained language models such as bert. however, there are limited studies on how to leverage more powerful sequence - to - sequence models such as t5. existing attempts usually formulate text ranking as classification and rely on postprocessing to obtain a ranked list. in this paper, we propose rankt5 and study two t5 - based ranking model structures, an encoder - decoder and an encoder - only one, so that they not only can directly output ranking scores for each query - document pair, but also can be fine - tuned with " pairwise " or " listwise " ranking losses to optimize ranking performances. our experiments show that the proposed models with ranking losses can achieve substantial ranking performance gains on different public text ranking data sets. moreover, when fine - tuned with listwise ranking losses, the ranking model appears to have better zero - shot ranking performance on out - of - domain data sets compared to the model fine - tuned with classification losses. | arxiv:2210.10634 |
recently, a monte carlo approach was proposed for processing highly redundant continuous frames. in this paper we present and analyze applications of this new theory. the computational complexity of the monte carlo method relies on the continuous frame being so called linear volume discretizable ( lvd ). the lvd property means that the number of samples in the coefficient space required by the monte carlo method is proportional to the resolution of the discrete signal. we show in this paper that the continuous wavelet transform ( cwt ) and the localizing time - frequency transform ( ltft ) are lvd. the ltft is a time - frequency representation based on a 3d time - frequency space with a richer class of time - frequency atoms than classical time - frequency transforms like the short time fourier transform ( stft ) and the cwt. our analysis proves that performing signal processing with the ltft has the same asymptotic complexity as signal processing with the stft and cwt ( based on fft ), even though the coefficient space of the ltft is higher dimensional. | arxiv:2009.10525 |
we investigate the effect of quantum interferences and coulomb interaction on the counting statistics of electrons crossing a double quantum dot in a parallel geometry using a generating function technique based on a quantum master equation approach. the skewness and the average residence time of electrons in the dots are shown to be the quantities most sensitive to interferences and coulomb coupling. the joint probabilities of consecutive electron transfer processes show characteristic temporal oscillations due to interference. the steady - state fluctuation theorem which predicts a universal connection between the number of forward and backward transfer events is shown to hold even in the presence of coulomb coupling and interference. | arxiv:0709.3551 |
we have identified a major global enhancement of star formation in the inner m31 disk that occurred between 2 - 4 gyr ago, producing $ \ sim $ 60 % of the stellar mass formed in the past 5 gyr. the presence of this episode in the inner disk was discovered by modeling the optical resolved star color - magnitude diagrams of low extinction regions in the main disk of m31 ( 3 $ < $ r $ < $ 20 kpc ) as part of the panchromatic hubble andromeda treasury. this measurement confirms and extends recent measurements of a widespread star formation enhancement of similar age in the outer disk, suggesting that this burst was both massive and global. following the galaxy - wide burst, the star formation rate of m31 has significantly declined. we briefly discuss possible causes for these features of the m31 evolutionary history, including interactions with m32, m33 and / or a merger. | arxiv:1504.02120 |
we investigate dynamics of the homogeneous time - dependent su ( 2 ) yang - mills fields governed by the non - abelian born - infeld lagrangian which arises in superstring theory as a result of summation of all orders in the string slope parameter $ \ alpha ' $. it is shown that generically the born - infeld dynamics is less chaotic than that in the ordinary yang - mills theory, and at high enough field strength the yang - mills chaos is stabilized. more generally, a smothering effect of the string non - locality on behavior of classical fields is conjectured. | arxiv:hep-th/0301069 |
governments are increasingly employing funding for open source software ( oss ) development as a policy lever to support the security of software supply chains, digital sovereignty, economic growth, and national competitiveness in science and innovation, among others. however, the impacts of public funding on oss development remain poorly understood, with a lack of consensus on how to meaningfully measure them. this gap hampers assessments of the return on public investment and impedes the optimisation of public - interest funding strategies. we address this gap with a toolkit of methodological considerations that may inform such measurements, drawing on prior work on oss valuations and community health metrics by the community health analytics open source software ( chaoss ) project as well as our first - hand learnings as practitioners tasked with evaluating funding programmes by the next generation internet initiative and the sovereign tech agency. we discuss salient considerations, including the importance of accounting for funding objectives, project life stage and social structure, and regional and organisational cost factors. next, we present a taxonomy of potential social, economic, and technological impacts that can be both positive and negative, direct and indirect, internal ( i. e. within a project ) and external ( i. e. among a project ' s ecosystem of dependents and users ), and manifest over various time horizons. furthermore, we discuss the merits and limitations of qualitative, quantitative, and mixed - methods approaches, as well as options for and hazards of estimating multiplier effects. with this toolkit, we contribute to the multi - stakeholder conversation about the value and impacts of funding on oss developers and society at large. | arxiv:2411.06027 |
sequence decoding is one of the core components of most visual - lingual models. however, typical neural decoders when faced with decoding multiple, possibly correlated, sequences of tokens resort to simple independent decoding schemes. in this paper, we introduce a consistent multiple sequence decoding architecture, which is while relatively simple, is general and allows for consistent and simultaneous decoding of an arbitrary number of sequences. our formulation utilizes a consistency fusion mechanism, implemented using message passing in a graph neural network ( gnn ), to aggregate context from related decoders. this context is then utilized as a secondary input, in addition to previously generated output, to make a prediction at a given step of decoding. self - attention, in the gnn, is used to modulate the fusion mechanism locally at each node and each step in the decoding process. we show the efficacy of our consistent multiple sequence decoder on the task of dense relational image captioning and illustrate state - of - the - art performance ( + 5. 2 % in map ) on the task. more importantly, we illustrate that the decoded sentences, for the same regions, are more consistent ( improvement of 9. 5 % ), while across images and regions maintain diversity. | arxiv:2004.00760 |
we consider the problem of nonparametric estimation of a convex regression function $ \ phi _ 0 $. we study the risk of the least squares estimator ( lse ) under the natural squared error loss. we show that the risk is always bounded from above by $ n ^ { - 4 / 5 } $ modulo logarithmic factors while being much smaller when $ \ phi _ 0 $ is well - approximable by a piecewise affine convex function with not too many affine pieces ( in which case, the risk is at most $ 1 / n $ up to logarithmic factors ). on the other hand, when $ \ phi _ 0 $ has curvature, we show that no estimator can have risk smaller than a constant multiple of $ n ^ { - 4 / 5 } $ in a very strong sense by proving a " local " minimax lower bound. we also study the case of model misspecification where we show that the lse exhibits the same global behavior provided the loss is measured from the closest convex projection of the true regression function. in the process of deriving our risk bounds, we prove new results for the metric entropy of local neighborhoods of the space of univariate convex functions. these results, which may be of independent interest, demonstrate the non - uniform nature of the space of univariate convex functions in sharp contrast to classical function spaces based on smoothness constraints. | arxiv:1305.1648 |
we consider time evolution of order parameters and entanglement asymmetries in the ferromagnetic phase of the transverse - field ising chain. one side of the system is prepared in a ferromagnetic ground state and the other side either in equilibrium at higher temperature or out of equilibrium. we focus on the disorder - order interface in which the order parameter attains a nonzero value, different from the ground state one. in that region, correlations follow a universal behaviour. we analytically compute the asymptotic scaling functions of the one - and two - point equal time correlations of the order parameter and provide numerical evidence that also the non - equal time correlations are universal. we analyze the r \ ' enyi entanglement asymmetries of subsystems and obtain a prediction that is expected to hold also in the von neumann limit. finally, we show that the wigner - yanase skew information of the order paramerter in subsystems within the interfacial region scales as their length squared. we propose a semiclassical approximation that is particularly effective close to the edge of the lightcone. | arxiv:2411.04089 |
the chromatic number of a latin square is the least number of partial transversals which cover its cells. this is just the chromatic number of its associated latin square graph. although latin square graphs have been widely studied as strongly regular graphs, their chromatic numbers appear to be unexplored. we determine the chromatic number of a circulant latin square, and find bounds for some other classes of latin squares. with a computer, we find the chromatic number for all main classes of latin squares of order at most eight. | arxiv:1510.02521 |
we take advantage of the correspondence between pseudogroups and inverse quantal frames, and of the recent description of morita equivalence for inverse quantal frames in terms of biprincipal bisheaves, to define morita equivalence for pseudogroups and to investigate its applications. in particular, two pseudogroups are morita equivalent if and only if their corresponding localic \ ' etale groupoids are. we explore the clear analogies between our definition of morita equivalence for pseudogroups and the usual notion of strong morita equivalence for $ c ^ { \ ast } $ - algebras and these lead to a number of concrete results. | arxiv:2011.14335 |
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