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we construct $ ( 2, 3 ) $ - generators for the finite $ 8 $ - dimensional orthogonal groups, proving the following results : the groups $ \ omega _ 8 ^ + ( q ) $ and $ p \ omega _ 8 ^ + ( q ) $ are $ ( 2, 3 ) $ - generated if and only if $ q \ geq 4 $ ; the groups $ \ omega _ 8 ^ - ( q ) $ and $ p \ omega _ 8 ^ - ( q ) $ are $ ( 2, 3 ) $ - generated for all $ q \ geq 2 $.
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arxiv:2201.00367
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a new conceptual approach for examining the origin of cosmic rays is developed by considering the characteristics of particle trajectory distributions in four - dimensional euclidean space - time. transformation of an isotropic distribution into a velocity distribution in ordinary three - dimensional space results in a spatially isotropic flux of highly relativistic particles. this particle flux exhibits a power - law energy spectrum that decreases with increasing energy approximately inversely as the square of the energy and peaks at much lower energies. this model also provides additional results resembling the observed characteristics of cosmic radiation.
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arxiv:physics/0108049
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we show that the computational model based on local fermionic modes in place of qubits does not satisfy local tomography and monogamy of entanglement, and has mixed states with maximal entanglement of formation. these features directly follow from the parity conservation corresponding to the parity superselection rule. we generalize quantum superselection rules to general probabilistic theories as sets of linear constraints on the convex set of states. we then provide a link between the cardinality of the superselection rule and the degree of holism of the resulting theory.
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arxiv:1307.7902
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we apply the statistical measure of complexity introduced by lopez - ruiz, mancini and calbet to neutron stars structure. neutron stars is a classical example where the gravitational field and quantum behavior are combined and produce a macroscopic dense object. actually, we continue the recent application of sanudo and pacheco to white dwarfs structure. we concentrate our study on the connection between complexity and neutron star properties, like maximum mass and the corresponding radius, applying a specific set of realistic equation of states. moreover, the effect of the strength of the gravitational field on the neutron star structure and consequently on the complexity measure is also investigated. it is seen that neutron stars, consistent with astronomical observations so far, are ordered systems ( low complexity ), which cannot grow in complexity as their mass increases. this is a result of the interplay of gravity, the short - range nuclear force and the very short - range weak interaction.
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arxiv:0905.4364
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we examine the majorization properties of general thermal - like mixed states depending on a set of parameters. sufficient conditions which ensure the increase in mixedness, and hence of any associated entropic form, when these parameters are varied, are identified. we then discuss those exhibiting a power law distribution, showing that they can be characterized by two distinct mixing parameters, one associated with temperature and the other with the non - extensivity index q. illustrative numerical results are also provided.
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arxiv:0906.1216
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cross - domain recommendation ( cdr ) extends conventional recommender systems by leveraging user - item interactions from dense domains to mitigate data sparsity and the cold start problem. while cdr offers substantial potential for enhancing recommendation performance, most existing cdr methods suffer from sensitivity to the ratio of overlapping users and intrinsic discrepancy between source and target domains. to overcome these limitations, in this work, we explore the application of graph signal processing ( gsp ) in cdr scenarios. we propose cgsp, a unified cdr framework based on gsp, which employs a cross - domain similarity graph constructed by flexibly combining target - only similarity and source - bridged similarity. by processing personalized graph signals computed for users from either the source or target domain, our framework effectively supports both inter - domain and intra - domain recommendations. our empirical evaluation demonstrates that cgsp consistently outperforms various encoder - based cdr approaches in both intra - domain and inter - domain recommendation scenarios, especially when the ratio of overlapping users is low, highlighting its significant practical implication in real - world applications.
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arxiv:2407.12374
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we describe a formalism, using groupoids, for the study of rewriting for presentations of inverse monoids, that is based on the squier complex construction for monoid presentations. we introduce the class of pseudoregular groupoids, an example of which now arises as the fundamental groupoid of our version of the squier complex. a further key ingredient is the factorisation of the presentation map from a free inverse monoid as the composition of an idempotent pure map and an idempotent separating map. the relation module of a presentation is then defined as the abelianised kernel of this idempotent separating map. we then use the properties of idempotent separating maps to derive a free presentation of the relation module. the construction of its kernel - the module of identities - uses further facts about pseudoregular groupoids.
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arxiv:1904.13135
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in conversational recommendation systems ( crs ), a user can provide feedback on recommended items at each interaction turn, leading the crs towards more desirable recommendations. currently, different types of crs offer various possibilities for feedback, i. e., natural language feedback, or answering clarifying questions. in most cases, a user simulator is employed for training as well as evaluating the crs. such user simulators typically critique the current retrieved items based on knowledge of a single target item. still, evaluating systems in offline settings with simulators suffers from problems, such as focusing entirely on a single target item ( not addressing the exploratory nature of a recommender system ), and exhibiting extreme patience ( consistent feedback over a large number of turns ). to overcome these limitations, we obtain extra judgements for a selection of alternative items in common crs datasets, namely shoes and fashion iq dresses. going further, we propose improved user simulators that allow simulated users not only to express their preferences about alternative items to their original target, but also to change their mind and level of patience. in our experiments using the relative image captioning crs setting and different crs models, we find that using the knowledge of alternatives by the simulator can have a considerable impact on the evaluation of existing crs models, specifically that the existing single - target evaluation underestimates their effectiveness, and when simulated users are allowed to instead consider alternatives, the system can rapidly respond to more quickly satisfy the user.
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arxiv:2401.05783
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we present and analyze a joint source - channel coding strategy for the transmission of a gaussian source across a gaussian channel in n channel uses per source symbol. among all such strategies, our scheme has the following properties : i ) the resulting mean - squared error scales optimally with the signal - to - noise ratio, and ii ) the scheme is easy to implement and the incurred delay is minimal, in the sense that a single source symbol is encoded at a time.
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arxiv:0904.1281
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photons, by nature, typically do not exhibit interactions with each other. creating photon - photon interactions holds immense importance in both fundamental physics and quantum technologies. currently, such interactions have only been achieved indirectly as mediated by atomic - like quantum emitters with resonant photon - atom interactions. however, the use of these indirect interactions presents substantial fundamental challenges that impede scaling and practical applications. here we demonstrate creation of non - classical photon correlations, including photon anti - bunching, via a passive ingap photonic integrated circuit. our approach employs the quantum interference between uncorrelated light and the two - photon bound state, the latter of which arises from the $ \ chi ^ { ( 2 ) } $ - mediated photon interaction. our work opens a new route in controlling quantum light by harnessing highly - engineerable bulk optical nonlinearities, which has significant implications for nonlinear optical quantum information processing and quantum networking.
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arxiv:2304.11676
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the ability to generate particles from the quantum vacuum is one of the most profound consequences of heisenberg ' s uncertainty principle. although the significance of vacuum fluctuations can be seen throughout physics, the experimental realization of vacuum amplification effects has until now been limited to a few cases. superconducting circuit devices, driven by the goal to achieve a viable quantum computer, have been used in the experimental demonstration of the dynamical casimir effect, and may soon be able to realize the elusive verification of analogue hawking radiation. this article describes several mechanisms for generating photons from the quantum vacuum and emphasizes their connection to the well - known parametric amplifier from quantum optics. discussed in detail is the possible realization of each mechanism, or its analogue, in superconducting circuit systems. the ability to selectively engineer these circuit devices highlights the relationship between the various amplification mechanisms.
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arxiv:1103.0835
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the corona factorization property of a c * - algebra, originally defined to study extensions of c * - algebras, has turned out to say something important about intrinsic structural properties of the c * - algebra. we show in this paper that a \ sigma - unital c * - algebra a of real rank zero has the corona factorization roperty if and only if its monoid v ( a ) of murray - von neumann equivalence classes of projections in matrix algebras over a has a certain ( rather weak ) comparability property that we call the corona factorization property ( for monoids ). we show that a projection in such a c * - algebra is properly infinite if ( and only if ) a multiple of it is properly infinite. the latter result is obtained from some more general result we establish about conical refinement monoids. we show that the set of order units ( together with the zero - element ) in a conical refinement monoid is again a refinement monoid under the assumption that the monoid satisfies weak divisibility ; and if u is an element in a refinement monoid such that nu is properly infinite, then u can be written as a sum u = s + t such that ns and nt are properly infinite.
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arxiv:0904.0541
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the weak $ ( 1, 1 ) $ boundedness of the littlewood - - paley - - stein square function for the dunkl heat flow is proved via estimates on the dunkl heat kernel of integral type and the caldr \ ' { o } n - - zygmund decomposition, which is the continuity of the recently work [ arxiv : 2003. 11843 ] where the dimension - free $ l ^ p $ boundedness of the same square function is studied.
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arxiv:2101.04056
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in this paper, we generalize the residual entanglement to the case of multipartite states in arbitrary dimensions by making use of a new method. through the introduction of a special entanglement measure, the residual entanglement of mixed states takes on a form that is more elegant than that in ref. [ 7 ] ( phys. rev. a 61 ( 2000 ) 052306 ). the result obtained in this paper is different from the previous one given in ref. [ 8 ] ( phys. rev. a 63 ( 2000 ) 044301 ). several examples demonstrate that our present result is a good measurement of the multipartite entanglement. furthermore, the original residual entanglement is a special case of our result.
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arxiv:quant-ph/0501079
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trade imbalances significantly alter the welfare implications of tariffs. using an illustrative model, we show that trade deficits enhance a country ' s ability to alter its terms of trade, and thereby benefit from tariffs. greater trade deficits imply higher optimal, or welfare maximizing, tariffs. we compute optimal unilateral and nash equilibrium tariffs between the united states and china $ \ unicode { x2014 } $ the countries with the largest bilateral trade imbalance $ \ unicode { x2014 } $ using a multi - region, multi - sector applied general equilibrium model with service sectors and input - output linkages, a computationally complex task. free trade benefits both countries compared to a trade war. relative to existing tariff rates, however, the united states gains from a trade war with china $ \ unicode { x2014 } $ a result that hinges on their bilateral trade imbalance.
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arxiv:2411.15092
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we present the theory of a density matrix renormalization group ( dmrg ) algorithm which can solve for both the ground and excited states of non - hermitian transcorrelated hamiltonians, and show applications in \ emph { ab initio } molecular systems. transcorrelation ( tc ) accelerates the basis set convergence rate by including known physics ( such as, but not limited to, the electron - electron cusp ) in the jastrow factor used for the similarity transformation. it also improves the accuracy of approximate methods such as coupled cluster singles and doubles ( ccsd ) as shown by some recent studies. however, the non - hermiticity of the tc hamiltonians poses challenges for variational methods like dmrg. imaginary - time evolution on the matrix product state ( mps ) in the dmrg framework has been proposed to circumvent this problem ; but this is currently limited to treating the ground state, and has lower efficiency than the time - independent dmrg ( ti - dmrg ), due to the need to eliminate trotter errors. in this work, we show that with minimal changes to the existing ti - dmrg algorithm, namely replacing the original davidson solver with the general davidson solver to solve the non - hermitian effective hamiltonians at each site for a few low - lying right eigenstates, and following the rest of the original dmrg recipe, one can find the ground and excited states with improved efficiency compared to the original dmrg when extrapolating to the infinite bond dimension limit in the same basis set. accelerated basis set convergence rate is also observed, as expected, within the tc framework.
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arxiv:2211.00173
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we show the skills of a data - driven low - dimensional linear model in predicting the spatio - temporal evolution of turbulent rayleigh - b \ ' enard convection. the model is based on dynamic mode decomposition with delay - embedding, which provides a data - driven finite - dimensional approximation to the system ' s koopman operator. the model is built using vector - valued observables from direct numerical simulations, and can provide accurate predictions. similar high prediction skills are found for the kuramoto - sivashinsky equation in the strongly - chaotic regimes.
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arxiv:1812.09438
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we determine the conditions for maximally supersymmetric ads _ 5 vacua of five - dimensional gauged n = 2 supergravity coupled to vector -, tensor - and hypermultiplets charged under an arbitrary gauge group. in particular, we show that the unbroken gauge group of the ads _ 5 vacua has to contain an u ( 1 ) _ r - factor. moreover we prove that the scalar deformations which preserve all supercharges form a kahler submanifold of the ambient quaternionic kahler manifold spanned by the scalars in the hypermultiplets.
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arxiv:1601.00482
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we study the existence of geometrically controlled branched covering maps from $ \ mathbb r ^ 3 $ to open $ 3 $ - manifolds or to decomposition spaces $ \ mathbb s ^ 3 / g $, and from $ \ mathbb s ^ 3 / g $ to $ \ mathbb s ^ 3 $.
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arxiv:1310.8595
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we show that a positive proportion of all gaps between consecutive primes are small gaps. we provide several quantitative results, some unconditional and some conditional, in this flavour.
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arxiv:1103.5886
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as the world ' s largest radio telescope, the square kilometer array ( ska ) will provide radio interferometric data with unprecedented detail. image reconstruction algorithms for radio interferometry are challenged to scale well with terabyte image sizes never seen before. in this work, we investigate one such 3d image reconstruction algorithm known as muffin ( multi - frequency image reconstruction for radio interferometry ). in particular, we focus on the challenging task of automatically finding the optimal regularization parameter values. in practice, finding the regularization parameters using classical grid search is computationally intensive and nontrivial due to the lack of ground - truth. we adopt a greedy strategy where, at each iteration, the optimal parameters are found by minimizing the predicted stein unbiased risk estimate ( psure ). the proposed self - tuned version of muffin involves parallel and computationally efficient steps, and scales well with large - scale data. finally, numerical results on a 3d image are presented to showcase the performance of the proposed approach.
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arxiv:1703.03608
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ieee 802. 15. 4 takes a center stage in iot as low - rate wireless personal area networks ( lr - wpans ). the standard specifies offset quadrature phase shift keying physical layer ( o - qpsk phy ) with half - sine pulse shaping which can be either analyzed under the class of m - ary psk signals ( qpsk signal with offset ) or as minimum shift keying ( msk ) signal. m - ary psk demodulation is requires perfect carrier and has minimal error. msk signals which falls under continuous phase frequency shift keying can be demodulated non - coherently but error performance is not as good. in our paper, this dual nature of ieee 802. 15. 4 phy is exploited to propose a dual mode receiver comprising of qpsk demodulator chain and msk demodulator chain as a single system on chip. the mode can be configured manually depending on the type of application or based on the feedback from a signal to noise ( snr ) indicator employed in the proposed receiver. m - ary psk chain is selected for lower snrs and msk for higher snrs. each of these properties are analyzed in detail for both demodulator chains and we go on to prove that msk detection can be used for low power, low complex and low latency while qpsk detection is employed for minimal error.
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arxiv:1611.03482
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collaborative filtering ( cf ) aims to build a model from users ' past behaviors and / or similar decisions made by other users, and use the model to recommend items for users. despite of the success of previous collaborative filtering approaches, they are all based on the assumption that there are sufficient rating scores available for building high - quality recommendation models. in real world applications, however, it is often difficult to collect sufficient rating scores, especially when new items are introduced into the system, which makes the recommendation task challenging. we find that there are often " short " texts describing features of items, based on which we can approximate the similarity of items and make recommendation together with rating scores. in this paper we " borrow " the idea of vector representation of words to capture the information of short texts and embed it into a matrix factorization framework. we empirically show that our approach is effective by comparing it with state - of - the - art approaches.
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arxiv:1703.04854
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the 20th - century engineering feat that most improved the quality of human life, the electric power system, now faces discipline - spanning challenges that threaten that distinction. so multilayered and complex that they resemble ecosystems, power grids face risks from their interdependent cyber, physical, social and economic layers. only with a holistic understanding of the dynamics of electricity infrastructure and human operators, automatic controls, electricity markets, weather, climate and policy can we fortify worldwide access to electricity.
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arxiv:1307.7305
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we present a theoretical and experimental analysis of the transverse monopole mode of a fast rotating bose - einstein condensate. the condensate ' s rotation frequency is similar to the trapping frequency and the effective confinement is only ensured by a weak quartic potential. we show that the non - harmonic character of the potential has a clear influence on the mode frequency, thus making the monopole mode a precise tool for the investigation of the fast rotation regime.
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arxiv:cond-mat/0311099
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compressive sensing ( cs ) exploits the surprising fact that the information contained in a sparse signal can be preserved in a small number of compressive, often random linear measurements of that signal. strong theoretical guarantees have been established concerning the embedding of a sparse signal family under a random measurement operator and on the accuracy to which sparse signals can be recovered from noisy compressive measurements. in this paper, we address similar questions in the context of a different modeling framework. instead of sparse models, we focus on the broad class of manifold models, which can arise in both parametric and non - parametric signal families. using tools from the theory of empirical processes, we improve upon previous results concerning the embedding of low - dimensional manifolds under random measurement operators. we also establish both deterministic and probabilistic instance - optimal bounds in $ \ ell _ 2 $ for manifold - based signal recovery and parameter estimation from noisy compressive measurements. in line with analogous results for sparsity - based cs, we conclude that much stronger bounds are possible in the probabilistic setting. our work supports the growing evidence that manifold - based models can be used with high accuracy in compressive signal processing.
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arxiv:1306.4748
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the superradiant phase transition ( spt ) has been widely studied in cavity quantum electrodynamics ( cqed ). however, this spt is still subject of ongoing debates due to the no - go theorem induced by the so - called $ { \ bf a } ^ 2 $ term ( at ). we propose a hybrid quantum system, consisting of a single - mode cavity simultaneously coupled to both a two - level system and yttrium - iron - garnet sphere supporting magnons with kerr nonlinearity, to restore the spt against the at. the kerr magnons here can effectively introduce an additional strong and tunable at to counteract the intrinsic at, via adiabatically eliminating the degrees of freedom of the magnons. we show that the kerr magnons induced spt can exist in both cases of ignoring and including the intrinsic at. without the intrinsic at, the critical coupling strength can be dramatically reduced by introducing the kerr magnons, which greatly relaxes the experimental conditions for observing the spt. with the intrinsic at, the forbidden spt can be recovered with the kerr magnons in a reversed way. our work paves a potential way to manipulate the spt against the at in hybrid systems combining cqed and nonlinear magnonics.
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arxiv:2302.07163
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in this paper we apply computer - aided theorem discovery technique to discover theorems about strongly equivalent logic programs under the answer set semantics. our discovered theorems capture new classes of strongly equivalent logic programs that can lead to new program simplification rules that preserve strong equivalence. specifically, with the help of computers, we discovered exact conditions that capture the strong equivalence between a rule and the empty set, between two rules, between two rules and one of the two rules, between two rules and another rule, and between three rules and two of the three rules.
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arxiv:1110.2738
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we classify 1 - dimensional connected dually flat manifolds $ m $ that are toric in the sense of [ molitor, arxiv : 2109. 04839 ], and show that the corresponding torifications are complex space forms. special emphasis is put on the case where m is an exponential family defined over a finite set.
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arxiv:2309.12123
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ferromagnetic - ferroelectric nanocomposites are of interest for realizing strong strain mediated coupling between electric and magnetic subsystems due to high surface area - to - volume ratio. this report is on the synthesis of nickel ferrite ( nfo ) - barium titanate ( bto ) core - shell nano - fibers, magnetic field assisted assembly into superstructures, and studies on magneto - electric ( me ) interactions. electrospinning techniques were used to prepare coaxial fibers of 0. 5 - 1. 5 micron in diameter. the core - shell structure of annealed fibers was confirmed by electron microscopy and scanning probe microscopy. the fibers were assembled into discs and films in a uniform magnetic field or a field gradient. studies on me coupling in the assembled films and discs were done by magnetic field h induced polarization, magneto - dielectric effects at low frequencies and at 16 - 24 ghz, and low frequency me voltage coefficients ( mevc ). we measured 2 ~ 2 - 7 % change in remnant polarization and in the permittivity for h = 7 koe, and a mevc of 0. 4 mv / cm oe at 30 hz. a model has been developed for low - frequency me effects in an assembly of fibers and takes into account dipole - dipole interactions between the fibers and fiber discontinuity. theoretical estimates for the low - frequency mevc have been compared with the data. these results indicate strong me coupling in superstructures of the core - shell fibers.
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arxiv:1708.05231
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this paper presents results from the sesar er3 domino project. three mechanisms are assessed at the ecac - wide level : 4d trajectory adjustments ( a combination of actively waiting for connecting passengers and dynamic cost indexing ), flight prioritisation ( enabling atfm slot swapping at arrival regulations ), and flight arrival coordination ( where flights are sequenced in extended arrival managers based on an advanced cost - driven optimisation ). classical and new metrics, designed to capture network effects, are used to analyse the results of a micro - level agent - based model. a scenario with congestion at three hubs is used to assess the 4d trajectory adjustment and the flight prioritisation mechanisms. two different scopes for the extended arrival manager are modelled to analyse the impact of the flight arrival coordination mechanism. results show that the 4d trajectory adjustments mechanism succeeds in reducing costs and delays for connecting passengers. a trade - off between the interests of the airlines in reducing costs and those of non - connecting passengers emerges, although passengers benefit overall from the mechanism. flight prioritisation is found to have no significant effects at the network level, as it is applied to a small number of flights. advanced flight arrival coordination, as implemented, increases delays and costs in the system. the arrival manager optimises the arrival sequence of all flights within its scope but does not consider flight uncertainties, thus leading to sub - optimal actions.
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arxiv:2209.09541
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we propose a phenomenological qcd sum rule with an explicit diquark field to investigate the essential ingredients inside the hadrons. introducing the mass ( m _ \ phi ) and the condensate ( \ phi ^ 2 ) for the diquark field as parameters in the model, we find that the sum rule works well for lambda, lambda _ c and lambda _ b. this implies that these lambda baryons can be represented by a diquark and a quark configuration. we also find that there is a duality relation among the parameters ( m _ \ phi, \ phi ^ 2 ), for which the sum rule is equally good. in the limit when \ phi ^ 2 = 0 we find m _ \ phi = 0. 4 gev, which can be thought as the constituent diquark mass.
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arxiv:1103.0826
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we prove that the $ ( 2, 1 ) $ - cable of the figure - eight knot is not smoothly slice by showing that its branched double cover bounds no equivariant homology ball.
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arxiv:2207.14187
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strong reflection principles with the reflection cardinal $ \ leq \ aleph _ 1 $ or $ < 2 ^ { \ aleph _ 0 } $ imply that the size of the continuum is either $ \ aleph _ 1 $ or $ \ aleph _ 2 $ or very large. thus, the stipulation, that a strong reflection principle should hold, seems to support the trichotomy on the possible size of the continuum. in this article, we examine the situation with the reflection principles and related notions of generic large cardinals.
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arxiv:2009.01609
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in this paper, to remedy this deficiency, we propose a linear attention mechanism which is approximate to dot - product attention with much less memory and computational costs. the efficient design makes the incorporation between attention mechanisms and neural networks more flexible and versatile. experiments conducted on semantic segmentation demonstrated the effectiveness of linear attention mechanism. code is available at https : / / github. com / lironui / linear - attention - mechanism.
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arxiv:2007.14902
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we present a new numerical algorithm for the solution of coupled collisional and collisionless systems, based on the block structured adaptive mesh and time refinement strategy ( amr ). we describe the issues associated with the discretization of the system equations and the synchronization of the numerical solution on the hierarchy of grid levels. we implement a code based on a higher order, conservative and directionally unsplit godunov ' s method for hydrodynamics ; a symmetric, time centered modified symplectic scheme for collisionless component ; and a multilevel, multigrid relaxation algorithm for the elliptic equation coupling the two components. numerical results that illustrate the accuracy of the code and the relative merit of various implemented schemes are also presented.
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arxiv:astro-ph/0608156
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let $ g \ geq 3 $ be fixed and odd, and for large $ q $ let $ \ chi $ be a primitive dirichlet character modulo $ q $ of order $ g $. conditionally on grh we improve the existing upper bounds in the p \ ' { o } lya - vinogradov inequality for $ \ chi $, showing that $ $ m ( \ chi ) : = \ max _ { t \ geq 1 } \ left | \ sum _ { n \ leq t } \ chi ( n ) \ right | \ ll \ sqrt { q } \ frac { ( \ log \ log q ) ^ { 1 - \ delta _ g } ( \ log \ log \ log \ log \ log q ) ^ { \ delta _ g } } { ( \ log \ log \ log q ) ^ { 1 / 4 } }, $ $ where $ \ delta _ g : = 1 - \ tfrac { g } { \ pi } \ sin ( \ pi / g ) $. furthermore, we show unconditionally that there is an infinite sequence of order $ g $ primitive characters $ \ chi _ j $ modulo $ q _ j $ for which $ $ m ( \ chi _ j ) \ gg \ sqrt { q _ j } \ frac { ( \ log \ log q _ j ) ^ { 1 - \ delta _ g } ( \ log \ log \ log \ log \ log q _ j ) ^ { \ delta _ g } } { ( \ log \ log \ log q _ j ) ^ { 1 / 4 } }, $ $ so that our grh bound is sharp up to the implicit constant. this improves on previous work of granville and soundararajan, of goldmakher, and of lamzouri and the author.
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arxiv:2505.07651
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multivariate spatio - temporal data arise more and more frequently in a wide range of applications ; however, there are relatively few general statistical methods that can readily use that incorporate spatial, temporal and variable dependencies simultaneously. in this paper, we propose a new approach to represent non - parametrically the linear dependence structure of a multivariate spatio - temporal process in terms of latent common factors. the matrix structure of observations from the multivariate spatio - temporal process is well reserved through the matrix factor model configuration. the spatial loading functions are estimated non - parametrically by sieve approximation and the variable loading matrix is estimated via an eigen - analysis of a symmetric non - negative definite matrix. though factor decomposition along the space mode is similar to the low - rank approximation methods in spatial statistics, the fundamental difference is that the low - dimensional structure is completely unknown in our setting. additionally, our method accommodates non - stationarity over space. the estimated loading functions facilitate spatial prediction. for temporal forecasting, we preserve the matrix structure of observations at each time point by utilizing the matrix autoregressive model of order one mar ( 1 ). asymptotic properties of the proposed methods are established. performance of the proposed method is investigated on both synthetic and real datasets
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arxiv:1710.06351
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although integrable spin chains only host ballistically propagating particles they can still feature diffusive spin transport. this diffusive spin transport originates from quasiparticle charge fluctuations inherited from the initial state ' s magnetization gaussian fluctuations. we show that ensembles of initial states with quasi - long range correlations lead to superdiffusive spin transport with a tunable dynamical exponent. we substantiate our prediction with numerical simulations and explain how deviations arise from finite time and finite size effects.
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arxiv:2306.04682
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we present a review of the leading theoretical approaches in the field of cuprate high temperature superconductivity. we start out by defining the problem and ask the question : whether an overarching theory possible ( which is capable of explaining not only the mechanism of unconventional superconductivity but also a coherent understanding of the strange metal phase and the pseudogap phase )? if it is possible, what should we expect from the overarching theory? we list various experimental facts, and point out what can we learn from them and where do current theories stand in addressing them? next, we present a critique of the current leading approaches. we conclude that although progress in the field has been unprecedented, but we still lack a coherent understanding.
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arxiv:2006.06335
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with 741 kg of teo2 crystals and an excellent energy resolution of 5 kev ( 0. 2 % ) at the region of interest, the cuore ( cryogenic underground observatory for rare events ) experiment aims at searching for neutrinoless double beta decay of 130te with unprecedented sensitivity. expected to start data taking in 2015, cuore is currently in an advanced construction phase at lngs. cuore projected neutrinoless double beta decay half - life sensitivity is 1. 6e26 y at 1 sigma ( 9. 5e25 y at the 90 % confidence level ), in five years of live time, corresponding to an upper limit on the effective majorana mass in the range 40 - 100 mev ( 50 - 130 mev ). further background rejection with auxiliary bolometric detectors could improve cuore sensitivity and competitiveness of bolometric detectors towards a full analysis of the inverted neutrino mass hierarchy. cuore - 0 was built to test and demonstrate the performance of the upcoming cuore experiment. it consists of a single cuore tower ( 52 teo2 bolometers of 750 g each, arranged in a 13 floor structure ) constructed strictly following cuore recipes both for materials and assembly procedures. an experiment its own, cuore - 0 is expected to reach a sensitivity to the neutrinoless double beta decay half - life of 130te around 3e24 y in one year of live time. we present an update of the data, corresponding to an exposure of 18. 1 kg y. an analysis of the background indicates that the cuore performance goal is satisfied while the sensitivity goal is within reach.
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arxiv:1502.02576
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physics - informed neural networks ( pinns ) have gained significant attention for solving forward and inverse problems related to partial differential equations ( pdes ). while advancements in loss functions and network architectures have improved pinn accuracy, the impact of collocation point sampling on their performance remains underexplored. fixed sampling methods, such as uniform random sampling and equispaced grids, can fail to capture critical regions with high solution gradients, limiting their effectiveness for complex pdes. adaptive methods, inspired by adaptive mesh refinement from traditional numerical methods, address this by dynamically updating collocation points during training but may overlook residual dynamics between updates, potentially losing valuable information. to overcome this limitation, we propose an adaptive collocation point selection strategy utilizing the qr discrete empirical interpolation method ( qr - deim ), a reduced - order modeling technique for efficiently approximating nonlinear functions. our results on benchmark pdes, including the wave, allen - cahn, and burgers ' equations, demonstrate that our qr - deim - based approach improves pinn accuracy compared to existing methods, offering a promising direction for adaptive collocation point strategies.
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arxiv:2501.07700
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this paper is devoted to the numerical analysis of the hermite spectral method proposed in [ 14 ], which provides, in the semi - classical limit, an asymptotic preserving approximation of the von neumann equation. more precisely, it relies on the use of so - called weyl ' s variables to effectively address the stiffness associated to the equation. then by employing a truncated hermite expansion of the density operator, we successfully manage this stiffness and provide error estimates by leveraging the propagation of regularity in the exact solution.
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arxiv:2504.18177
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measure space, $ \ tau : x \ to x $ an invertible measure - preserving transformation, and suppose that $ f \ in l ^ 1 ( x ) $ such that for any sequence $ ( t _ n ) $ of integers there exists a constant $ c _ 1 > 0 $ such that $ $ \ mu \ left \ { x : \ sup _ { n \ geq 1 } \ left | \ sum _ { i \ in \ mathcal { b } _ n - t _ n } \! \! \! \ raise { 1. 9ex } \ hbox { $ \ scriptsize \ prime $ } \ ; \ frac { f ( \ tau ^ ix ) } { i } \ right | > \ lambda \ right \ } \ leq c _ 1 \ mu \ left \ { x : \ sup _ { n \ geq 1 } \ left | \ sum _ { i \ in \ mathcal { b } _ n } \! \! \ raise { 1. 9ex } \ hbox { $ \ scriptsize \ prime $ } \ ; \ frac { f ( \ tau ^ i x ) } { i } \ right | > \ lambda \ right \ } $ $ for all $ \ lambda > 0 $, where $ \ mathcal { b } _ n = \ { - n, - ( n - 1 ), - ( n - 2 ), \ dots, n - 2, n - 1, n \ } $. then there exists a constant $ c _ 2 > 0 $ which does not depend on $ f $ such that $ $ \ sum _ { n = 1 } ^ \ infty \ mu \ left \ { x : \ left | \ sum _ { i = - n } ^ { n } \! \! \ raise { 1. 9ex } \ hbox { $ \ scriptsize \ prime $ } \ ; \ frac { f ( \ tau ^ ix ) } { i } \ right | > \ lambda \ right \ } \ leq \ frac { c _ 2 } { \ lambda } \ | f \ | _ 1 $ $ for all $ \ lambda > 0 $.
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arxiv:2009.05822
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we prove that a prime knot k is not determined by its p - fold cyclic branched cover for at most two odd primes p. moreover, we show that for a given odd prime p, the p - fold cyclic branched cover of a prime knot k is the p - fold cyclic branched cover of at most one more knot k ' non equivalent to k. to prove the main theorem, a result concerning the symmetries of knots is also obtained. this latter result can be interpreted as a characterisation of the trivial knot.
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arxiv:math/0702783
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abstract contextuality is a property of systems of random variables. the identity of a random variable in a system is determined by its joint distribution with all other random variables in the same context. when context changes, a variable measuring some property is instantly replaced by another random variable measuring the same property, or instantly disappears if this property is not measured in the new context. this replacement / disappearance requires no action, signaling, or disturbance, although it does not exclude them. the difference between two random variables measuring the same property in different contexts is measured by their maximal coupling, and the system is noncontextual if one of its overall couplings has these maximal couplings as its marginals.
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arxiv:2104.12495
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the kepler mission revealed a plethora of stellar variability in the light curves of many stars, some associated with magnetic activity or stellar oscillations. in this work, we analyse the periodic signal in 162 intermediate - mass stars, interpreted as rossby modes and rotational modulation - the so - called \ textit { hump \ & spike } feature. we investigate whether the rotational modulation ( \ textit { spike } ) is due to stellar spots caused by magnetic fields or due to overstable convective ( osc ) modes resonantly exciting g ~ modes, with frequencies corresponding to the convective core rotation rate. assuming that the spikes are created by magnetic spots at the stellar surface, we recover the amplitudes of the magnetic fields, which are in good agreement with theoretical predictions. our data show a clear anti - correlation between the spike amplitudes and stellar mass and possibly a correlation with stellar age, consistent with the dynamo - generated magnetic fields theory in ( sub ) - surface convective layers. investigating the harmonic behaviour, we find that for 125 stars neither of the two possible explanations can be excluded. while our results suggest that the dynamo - generated magnetic field scenario is more likely to explain the \ textit { spike } feature, we assess further work is needed to distinguish between the two scenarios. one method for ruling out one of the two explanations is to directly observe magnetic fields in \ textit { hump \ & spike } stars. another would be to impose additional constraints through detailed modelling of our stars, regarding the rotation requirement in the osc mode scenario or the presence of a convective - core ( stellar age ).
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arxiv:2301.04974
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one of the most intriguing open questions of today ' s astrophysics is the one concerning the location and the mechanisms for the production of mev, gev, and tev gamma - rays in agn jets. m87 is a privileged laboratory for a detailed study of the properties of jets, owing to its proximity, its massive black hole, and its conspicuous emission at radio wavelengths and above. we started on november 2009 a monitoring program with the e - evn at 5 ghz, during which two episodes of activity at energy e > 100 gev have occured. we present here results of these multi - epoch observations. the inner jet and hst - 1 are both detected and resolved in our datasets. one of these observations was obtained at the same day of the first high energy flare. a clear change in the proper motion velocity of hst - 1 is present at the epoch ~ 2005. 5. in the time range 2003 - - 2005. 5 the apparent velocity is subluminal, and superluminal ( ~ 2. 7c ) after 2005. 5.
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arxiv:1006.3243
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the persistent current in three - dimensional mesoscopic rings is investigated numerically. the model is tight - binding one with random site - energies and interaction between electrons. the self - consistent hartree - fock approximation is adopted for the interaction between electrons, and models with up to $ 6 \ times 6 \ times 20 $ sites are investigated. it is shown that the long - range coulomb interaction enhances the persistent current for rings with finite width. the origin of the enhancement is discussed.
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arxiv:cond-mat/9501105
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the minerva collaboration operated a scaled - down replica of the solid scintillator tracking and sampling calorimeter regions of the minerva detector in a hadron test beam at the fermilab test beam facility. this article reports measurements with samples of protons, pions, and electrons from 0. 35 to 2. 0 gev / c momentum. the calorimetric response to protons, pions, and electrons are obtained from these data. a measurement of the parameter in birks ' law and an estimate of the tracking efficiency are extracted from the proton sample. overall the data are well described by a geant4 - based monte carlo simulation of the detector and particle interactions with agreements better than 4 %, though some features of the data are not precisely modeled. these measurements are used to tune the minerva detector simulation and evaluate systematic uncertainties in support of the minerva neutrino cross section measurement program.
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arxiv:1501.06431
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we establish, for the first time, a connection between stochastic games and multiparameter eigenvalue problems, using the theory developed by shapley and snow ( 1950 ). this connection provides new results, new proofs, and new tools for studying stochastic games.
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arxiv:1810.08798
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an augmented design in a square array can be derived from a smaller row - column design ( the contraction ). such a contraction has also previously been used to generate a two - replicate resolvable incomplete block design. we demonstrate a parallel between these two uses of the contraction and thereby establish a recently proposed conjecture by linking the average efficiency factor of the augmented design with that of its contraction.
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arxiv:2501.08448
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this review outlines concepts of mathematical statistics, elements of probability theory, hypothesis tests and point estimation for use in the analysis of modern astronomical data. least squares, maximum likelihood, and bayesian approaches to statistical inference are treated. resampling methods, particularly the bootstrap, provide valuable procedures when distributions functions of statistics are not known. several approaches to model selection and good - ness of fit are considered. applied statistics relevant to astronomical research are briefly discussed : nonparametric methods for use when little is known about the behavior of the astronomical populations or processes ; data smoothing with kernel density estimation and nonparametric regression ; unsupervised clustering and supervised classification procedures for multivariate problems ; survival analysis for astronomical datasets with nondetections ; time - and frequency - domain times series analysis for light curves ; and spatial statistics to interpret the spatial distributions of points in low dimensions. two types of resources are presented : about 40 recommended texts and monographs in various fields of statistics, and the public domain r software system for statistical analysis. together with its \ sim 3500 ( and growing ) add - on cran packages, r implements a vast range of statistical procedures in a coherent high - level language with advanced graphics.
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arxiv:1205.2064
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digital image forensics plays a crucial role in image authentication and manipulation localization. despite the progress powered by deep neural networks, existing forgery localization methodologies exhibit limitations when deployed to unseen datasets and perturbed images ( i. e., lack of generalization and robustness to real - world applications ). to circumvent these problems and aid image integrity, this paper presents a generalized and robust manipulation localization model through the analysis of pixel inconsistency artifacts. the rationale is grounded on the observation that most image signal processors ( isp ) involve the demosaicing process, which introduces pixel correlations in pristine images. moreover, manipulating operations, including splicing, copy - move, and inpainting, directly affect such pixel regularity. we, therefore, first split the input image into several blocks and design masked self - attention mechanisms to model the global pixel dependency in input images. simultaneously, we optimize another local pixel dependency stream to mine local manipulation clues within input forgery images. in addition, we design novel learning - to - weight modules ( lwm ) to combine features from the two streams, thereby enhancing the final forgery localization performance. to improve the training process, we propose a novel pixel - inconsistency data augmentation ( pida ) strategy, driving the model to focus on capturing inherent pixel - level artifacts instead of mining semantic forgery traces. this work establishes a comprehensive benchmark integrating 15 representative detection models across 12 datasets. extensive experiments show that our method successfully extracts inherent pixel - inconsistency forgery fingerprints and achieve state - of - the - art generalization and robustness performances in image manipulation localization.
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arxiv:2310.00234
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a growing issue in the modern cyberspace world is the direct identification of malicious activity over network connections. the boom of the machine learning industry in the past few years has led to the increasing usage of machine learning technologies, which are especially prevalent in the network intrusion detection research community. when utilizing these fairly contemporary techniques, the community has realized that datasets are pivotal for identifying malicious packets and connections, particularly ones associated with information concerning labeling in order to construct learning models. however, there exists a shortage of publicly available, relevant datasets to researchers in the network intrusion detection community. thus, in this paper, we introduce a method to construct labeled flow data by combining the packet meta - information with ids logs to infer labels for intrusion detection research. specifically, we designed a netflow - compatible format due to the capability of a a large body of network devices, such as routers and switches, to export netflow records from raw traffic. in doing so, the introduced method at hand would aid researchers to access relevant network flow datasets along with label information.
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arxiv:1810.01945
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we study experimentally and numerically the dynamics of colloidal beads confined by a harmonic potential in a bath of swimming e. coli bacteria. the resulting dynamics is well approximated by a langevin equation for an overdamped oscillator driven by the combination of a white thermal noise and an exponentially correlated active noise. this scenario leads to a simple generalization of the equipartition theorem resulting in the coexistence of two different effective temperatures that govern dynamics along the flat and the curved directions in the potential landscape.
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arxiv:1409.3929
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in this paper, we study two challenging and less - touched problems in single image dehazing, namely, how to make deep learning achieve image dehazing without training on the ground - truth clean image ( unsupervised ) and a image collection ( untrained ). an unsupervised neural network will avoid the intensive labor collection of hazy - clean image pairs, and an untrained model is a ` ` real ' ' single image dehazing approach which could remove haze based on only the observed hazy image itself and no extra images is used. motivated by the layer disentanglement idea, we propose a novel method, called you only look yourself ( \ textbf { yoly } ) which could be one of the first unsupervised and untrained neural networks for image dehazing. in brief, yoly employs three jointly subnetworks to separate the observed hazy image into several latent layers, \ textit { i. e. }, scene radiance layer, transmission map layer, and atmospheric light layer. after that, these three layers are further composed to the hazy image in a self - supervised manner. thanks to the unsupervised and untrained characteristics of yoly, our method bypasses the conventional training paradigm of deep models on hazy - clean pairs or a large scale dataset, thus avoids the labor - intensive data collection and the domain shift issue. besides, our method also provides an effective learning - based haze transfer solution thanks to its layer disentanglement mechanism. extensive experiments show the promising performance of our method in image dehazing compared with 14 methods on four databases.
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arxiv:2006.16829
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we show, that for a morphism of schemes from x to y, that is a finite modification in finitely many closed points, a cohomological brauer class on y is represented by an azumaya algebra if its pullback to x is represented by an azumaya algebra. part of the proof uses an extension of a result by ferrand, on pinching of finite locally free sheaves, to azumaya algebras.
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arxiv:2207.06344
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exploratory analysis of a text corpus is essential for assessing data quality and developing meaningful hypotheses. text analysis relies on understanding documents through structured attributes spanning various granularities of the documents such as words, phrases, sentences, topics, or clusters. however, current text visualization tools typically adopt a fixed representation tailored to specific tasks or domains, requiring users to switch tools as their analytical goals change. to address this limitation, we present texture, a general - purpose interactive text exploration tool. texture introduces a configurable data schema for representing text documents enriched with descriptive attributes. these attributes can appear at arbitrary levels of granularity in the text and possibly have multiple values, including document - level attributes, multi - valued attributes ( e. g., topics ), fine - grained span - level attributes ( e. g., words ), and vector embeddings. the system then combines existing interactive methods for text exploration into a single interface that provides attribute overview visualizations, supports cross - filtering attribute charts to explore subsets, uses embeddings for a dataset overview and similar instance search, and contextualizes filters in the actual documents. we evaluated texture through a two - part user study with 10 participants from varied domains who each analyzed their own dataset in a baseline session and then with texture. texture was able to represent all of the previously derived dataset attributes, enabled participants to more quickly iterate during their exploratory analysis, and discover new insights about their data. our findings contribute to the design of scalable, interactive, and flexible exploration systems that improve users ' ability to make sense of text data.
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arxiv:2504.16898
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we critically reexamine the precision tests of the standard model by coupling the current world average value of $ m _ w $ with the recent lep electroweak data with the aid of a modified zfitter program to include the dominant two - loop and qcd - ew mixed terms. the results show a clear evidence of nonvanishing electroweak radiative corrections. the recent cdf $ m _ t $ is a solution of the minimal $ \ chi ^ 2 $ - fits to the recent lep data set and $ m _ w = 80. 23 ( 18 ) ~ $ gev but with a heavy higgs scalar, i. e., $ m _ t = 179 ~ $ gev and $ m _ h = 300 ~ $ gev. we discuss how sensitive $ m _ t $ and $ m _ h $ are depending on the exact value of $ m _ w $ even within the present uncertainty, as well as on $ \ alpha _ s $ and $ \ alpha ( m _ z ) $. we show how the future improvements on $ m _ w $ can discriminate different values of $ m _ t $ and $ m _ h $ from the electroweak data and provide a crucial and decisive test for the standard model.
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arxiv:hep-ph/9503478
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actively q - switched lasers are widely used tools which are required to produce stable output pulse energies for many applications. in this paper, a model - based control concept for actively q - switched lasers is presented which stabilises their nonlinear pulse - to - pulse dynamics and rejects stochastic disturbances arising from amplified spontaneous emission. the feasibility of the control task is demonstrated to strongly depend on the design of the semi - active prelasing approach. in contrast to state - of - the - art hardware - based controllers, the proposed concept is flexible and cost - effective as it is not tailored to specific operation parameters.
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arxiv:2304.07075
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directed by naoko yamada and focuses on both the politics and devastation of the genpei war, a cataclysmic civil war in the 12th century that divided japan, and the personal lives and tragedies of the women of both warring clans who are caught up in the conflict. the series premiered on september 15, 2021 in north america on the funimation streaming service, with premieres the following day on the japanese streaming service fod ( operated by fuji tv ) and the chinese streaming service bilibili ; a japanese television broadcast on fuji tv ' s + ultra programming block followed in january 2022. following the conclusion of its streaming release, the heike story was named one of the best series of 2021, and was nominated in 3 categories for the 2022 anime trending awards. additionally, in september 2021, science saru produced two short films for the animated anthology project star wars : visions ( 2021 ). the shorts, entitled akakiri and t0 - b1, were part of a nine - film anthology of shorts, all of which premiered on september 22 worldwide on disney +. akakiri was directed by eunyoung choi and centers on the story of a princess and a jedi, while t0 - b1 was directed by abel gongora and follows the adventures of a droid who dreams of becoming a jedi and exploring the galaxy. the anthology as a whole received stellar reviews, with science saru ' s films highlighted as particular standouts. star wars : visions was heralded as one of the best animated projects of the year, as well as one of the best star wars titles in a decade or more. episodes of the anthology project were also nominated for multiple awards. in 2022, science saru released the original television animation series yurei deco. directed by tomohisa shimoyama, written by dai sato, and based on a concept by masaaki yuasa, the series drew inspiration from mark twain ' s the adventures of huckleberry finn and premiered to excellent reviews. science saru ' s following project was an animated adaptation of the novel tatami time machine blues. based on the novel of the same name written by tomihiko morimi and derived from a concept by makoto ueda, tatami time machine blues serves as a sequel to the tatami galaxy, which yuasa adapted as a television series in april 2010, prior to the establishment of science saru. the project was directed by shingo natsume, while screenwriter makoto ueda, character designer
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https://en.wikipedia.org/wiki/Science_Saru
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we introduce the notion of a symmetric basis of a vector space equipped with a quadratic form, and provide a sufficient and necessary condition for the existence to such a basis. symmetric bases are then used to study cayley graphs of certain extraspecial 2 - groups of order 2 ^ { 2r + 1 } ( r \ geq 1 ), which are further shown to be normal cayley graphs and 2 - arc - transitive covers of 2r - dimensional hypercubes.
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arxiv:1805.06371
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the precise determination of global properties of galaxy clusters, and their scaling relations, is a task of prime importance for the use of clusters as cosmological probes. we performed a detailed xmm - newton study of 14 x - ray luminous reflex survey clusters at z ~ 0. 3. we found that the properties of the galaxy clusters show a self - similar behavior at r > 0. 1r _ { vir }. this helps to establish tighter scaling relations. peculiarities in the individual clusters are important to understand the scatter from the self - similar frame in the cluster central parts.
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arxiv:astro-ph/0502197
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let $ g $ be a simple graph of order $ n $ and $ \ mu _ { 1 }, \ mu _ { 2 }, \ ldots, \ mu _ { n } $ be the roots of its matching polynomial. the matching energy is defined as the sum $ \ sum ^ { n } _ { i = 1 } | \ mu _ { i } | $, which was introduced by gutman and wagner in 2012. in this paper, the graphs with the first five smallest matching energies among all bicyclic graphs for order $ n > 5 $ are determined.
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arxiv:1704.02068
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tuning - free diffusion - based models have demonstrated significant potential in the realm of image personalization and customization. however, despite this notable progress, current models continue to grapple with several complex challenges in producing style - consistent image generation. firstly, the concept of style is inherently underdetermined, encompassing a multitude of elements such as color, material, atmosphere, design, and structure, among others. secondly, inversion - based methods are prone to style degradation, often resulting in the loss of fine - grained details. lastly, adapter - based approaches frequently require meticulous weight tuning for each reference image to achieve a balance between style intensity and text controllability. in this paper, we commence by examining several compelling yet frequently overlooked observations. we then proceed to introduce instantstyle, a framework designed to address these issues through the implementation of two key strategies : 1 ) a straightforward mechanism that decouples style and content from reference images within the feature space, predicated on the assumption that features within the same space can be either added to or subtracted from one another. 2 ) the injection of reference image features exclusively into style - specific blocks, thereby preventing style leaks and eschewing the need for cumbersome weight tuning, which often characterizes more parameter - heavy designs. our work demonstrates superior visual stylization outcomes, striking an optimal balance between the intensity of style and the controllability of textual elements. our codes will be available at https : / / github. com / instantstyle / instantstyle.
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arxiv:2404.02733
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a proposal is made for reducing the solution of the n - particle lippmann - schwinger equation to that of smaller sets of particles. this consists of first writing the n - particle equation in terms of all possible $ n / 2 $ - particle lippmann - schwinger equations. ( if n is odd this needs a minor modification. ) the second step requires a decoupling of the resolvents for the fewer particle systems so that each can be solved separately. this generalization of the faddeev approach deals only with connected kernels and the homogeneous solution reproduces the n - particle schr \ " odinger equation. for four particles the proposed method involves only a $ 3 \ times3 $ matrix whereas other approaches typically require the solution of at least a $ 7 \ times7 $ matrix equation.
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arxiv:nucl-th/0005053
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several high energy, > 100 gev, neutrino telescopes are currently operating or under construction. their main motivation is the extension of the horizon of neutrino astronomy to cosmological scales. we show that general, model independent, arguments imply that ~ 1 gton detectors are required to detect cosmic high energy neutrino sources. predictions of models of some of the leading candidate sources, gamma - ray bursts and micro - quasars, are discussed, and the question of what can be learned from neutrino observations is addressed.
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arxiv:astro-ph/0211358
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using the quantum covariant poisson bracket ( qcpb ) theory, we can accomplish much more compatible explanations of the quantum mechanics supported by the g - dynamics. we further study the generalized quantum harmonic oscillator equipped with the g - dynamics of type i, such as geometric creation and annihilation operators, and the geometric number operator as an extension of the number operator is well given for the deep discussions, the geometric hamiltonian operator is expressed as another form. especially, the geometric quantization rules based on the qcpb theory is then calculated.
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arxiv:2005.11141
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let $ \ m $ be a hyperfinite finite von nemann algebra and $ ( \ m _ k ) _ { k \ geq 1 } $ be an increasing filtration of finite dimensional von neumann subalgebras of $ \ m $. we investigate abstract fractional integrals associated to the filtration $ ( \ m _ k ) _ { k \ geq 1 } $. for a finite noncommutative martingale $ x = ( x _ k ) _ { 1 \ leq k \ leq n } \ subseteq l _ 1 ( \ m ) $ adapted to $ ( \ m _ k ) _ { k \ geq 1 } $ and $ 0 < \ alpha < 1 $, the fractional integral of $ x $ of order $ \ alpha $ is defined by setting : $ $ i ^ \ alpha x = \ sum _ { k = 1 } ^ n \ zeta _ k ^ { \ alpha } dx _ k $ $ for an appropriate sequence of scalars $ ( \ zeta _ k ) _ { k \ geq 1 } $. for the case of noncommutative dyadic martingale in $ l _ 1 ( \ r ) $ where $ \ r $ is the type $ { \ rm ii } _ 1 $ hyperfinite factor equipped with its natural increasing filtration, $ \ zeta _ k = 2 ^ { - k } $ for $ k \ geq 1 $. we prove that $ i ^ \ alpha $ is of weak - type $ ( 1, 1 / ( 1 - \ alpha ) ) $. more precisely, there is a constant $ { \ mathrm c } $ depending only on $ \ alpha $ such that if $ x = ( x _ k ) _ { k \ geq 1 } $ is a finite noncommutative martingale in $ l _ 1 ( \ m ) $ then \ [ \ | i ^ \ alpha x \ | _ { l _ { 1 / ( 1 - \ alpha ), \ infty } ( \ mathcal { \ m } ) } \ leq { \ mathrm c } \ | x \ | _ { l _ 1 ( \ m ) }. \ ] we also obtain that $ i ^ \ alpha $ is bounded from $ l _ { p } ( \ m ) $ into $ l _ { q } ( \ m ) $ where $ 1 < p < q < \ inft
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arxiv:1501.06016
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2 ^ k - 1 } \ log e + r $.
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arxiv:2201.02514
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this paper proposes an approach for improving performance of unimodal models with multimodal training. our approach involves a multi - branch architecture that incorporates unimodal models with a multimodal transformer - based branch. by co - training these branches, the stronger multimodal branch can transfer its knowledge to the weaker unimodal branches through a multi - task objective, thereby improving the performance of the resulting unimodal models. we evaluate our approach on tasks of dynamic hand gesture recognition based on rgb and depth, audiovisual emotion recognition based on speech and facial video, and audio - video - text based sentiment analysis. our approach outperforms the conventionally trained unimodal counterparts. interestingly, we also observe that optimization of the unimodal branches improves the multimodal branch, compared to a similar multimodal model trained from scratch.
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arxiv:2311.10170
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this paper attempts to undertake the study of segmentation image techniques by using five threshold methods as mean method, p - tile method, histogram dependent technique ( hdt ), edge maximization technique ( emt ) and visual technique and they are compared with one another so as to choose the best technique for threshold segmentation techniques image. these techniques applied on three satellite images to choose base guesses for threshold segmentation image.
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arxiv:1005.4020
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navigation in cluttered underwater environments is challenging, especially when there are constraints on communication and self - localisation. part of the fully distributed underwater navigation problem has been resolved by introducing multi - agent robot teams [ 1 ], however when the environment becomes cluttered, the problem remains unresolved. in this paper, we first studied the connection between everyday activity of dog walking and the cooperative underwater obstacle avoidance problem. inspired by this analogy, we propose a novel dog walking paradigm and implement it in a multi - agent underwater system. simulations were conducted across various scenarios, with performance benchmarked against traditional methods utilising image - based visual servoing in a multi - agent setup. results indicate that our dog walking - inspired paradigm significantly enhances cooperative behavior among agents and outperforms the existing approach in navigating through obstacles.
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arxiv:2403.10759
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equilibrated fluid - solid - growth ( fsge ) is a fast, open source, three - dimensional ( 3d ) computational platform for simulating interactions between instantaneous hemodynamics and long - term vessel wall adaptation through mechanobiologically equilibrated growth and remodeling ( g & r ). such models can capture evolving geometry, composition, and material properties in health and disease and following clinical interventions. in traditional g & r models, this feedback is modeled through highly simplified fluid solutions, neglecting local variations in blood pressure and wall shear stress ( wss ). fsge overcomes these inherent limitations by strongly coupling the 3d navier - stokes equations for blood flow with a 3d equilibrated constrained mixture model ( cmme ) for vascular tissue g & r. cmme allows one to predict long - term evolved mechanobiological equilibria from an original homeostatic state at a computational cost equivalent to that of a standard hyperelastic material model. in illustrative computational examples, we focus on the development of a stable aortic aneurysm in a mouse model to highlight key differences in growth patterns between fsge and solid - only g & r models. we show that fsge is especially important in blood vessels with asymmetric stimuli. simulation results reveal greater local variation in fluid - derived wss than in intramural stress ( ims ). thus, differences between fsge and g & r models became more pronounced with the growing influence of wss relative to pressure. future applications in highly localized disease processes, such as for lesion formation in atherosclerosis, can now include spatial and temporal variations of wss.
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arxiv:2404.13523
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high - power femtosecond laser radiation during the propagation in air ( and other transparent media ) experiences multiple filamentation. filamentation is a unique nonlinear optical phenomenon, which is accompanied by a wealth of nonlinear optical effects such as formation of extended plasma channels in the beam wake, generation of higher harmonics and supercontinuum, generation of thz radiation. the manifestations of laser filamentation can be useful for solving atmospheric optics problems related to remote sensing of the environment as well as directed transmission of laser power. the classical numerical methods used for simulating the nonlinear long - range atmospheric propagation of high - power radiation with a sufficiently large laser beam aperture have almost reached their limit regarding the acceleration of calculations. to solve this problem and speed - up the numerical simulations of laser filamentation, we propose an improved numerical technique based on a modified method of phase screens constructed on a sparse spatial grid. within the framework of this technique, we seek for optimal ansatz ( substitution function ) to the governing equations using the machine learning technology, which provides for the best correspondence to the numerical solution of the test problem using a denser spatial grid
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arxiv:2306.15678
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we found a broad absorption line ( bal ) outflow in the vlt / uves spectrum of the quasar sdss j235702. 54 - 004824. 0, in which we identified four subcomponents. we measured the column densities of the ions in one of the subcomponents ( $ v $ = - 1600 km s $ ^ { - 1 } $ ), which include o i and fe ii. we found the kinetic luminosity of this component to be at most ~ 2. 4 % of the quasar ' s eddington luminosity. this is near the amount required to contribute to agn feedback. we also examined the time - variability of a c iv mini - bal found at $ v $ = - 8700 km s $ ^ { - 1 } $, which shows a shallower and narrower absorption feature attached to it in previous sdss observations from 2000 and 2001, but not in the spectra from 2005 and onwards.
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arxiv:2209.06924
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we apply malliavin calculus to the $ \ phi ^ 4 _ 3 $ equation on the torus and prove existence of densities for the solution of the equation evaluated at regular enough test functions. we work in the framework of regularity structures and rely on besov - type spaces of modelled distributions in order to prove malliavin differentiability of the solution. our result applies to a large family of gaussian space - time noises including white noise, in particular the noise may be degenerate as long as it is sufficiently rough on small scales.
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arxiv:1711.08332
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determining the low - energy eigenspectra of quantum many - body systems is a long - standing challenge in physics. in this work, we solve this problem by introducing two novel algorithms to determine low - energy eigenstates based on a compact matrix product state ( mps ) representation of the multiple targeted eigenstates. the first algorithm utilizes a canonicalization approach that takes advantage of the imaginary - time evolution of multi - target mps, offering faster convergence and ease of implementation. the second algorithm employs a variational approach that optimizes local tensors on the grassmann manifold, capable of achieving higher accuracy. these algorithms can be used independently or combined to enhance convergence speed and accuracy. we apply them to the transverse - field ising model and demonstrate that the calculated low - energy eigenspectra agree remarkably well with the exact solution. moreover, the eigenenergies exhibit uniform convergence in gapped phases, suggesting that the low - energy excited eigenstates have nearly the same level of accuracy as the ground state. our results highlight the accuracy and versatility of multi - target mps - based algorithms for determining low - energy eigenspectra and their potential applications in quantum many - body physics.
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arxiv:2305.15868
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lennard - jones clusters, while an easy system, have a significant number of non equivalent configurations that increases rapidly with the number of atoms in the cluster. here, we aim at determining the cluster partition function ; we use the nested sampling algorithm, which transforms the multidimensional integral into a one - dimensional one, to perform this task. in particular, we use the nested _ fit program, which implements slice sampling as search algorithm. we study here the 7 - atoms and 36 - atoms clusters and then look at the computational cost of nested _ fit with and without parallelisation. we find that nested _ fit is able to recover phase transitions and find different stable configurations of the cluster. furthermore, the implementation of the slice sampling algorithm has a clear impact on the computational cost.
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arxiv:2501.11370
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air - ground robots ( agrs ) are widely used in surveillance and disaster response due to their exceptional mobility and versatility ( i. e., flying and driving ). current agr navigation systems perform well in static occlusion - prone environments ( e. g., indoors ) by using 3d semantic occupancy networks to predict occlusions for complete local mapping and then computing euclidean signed distance field ( esdf ) for path planning. however, these systems face challenges in dynamic, severe occlusion scenes ( e. g., crowds ) due to limitations in perception networks ' low prediction accuracy and path planners ' high computation overhead. in this paper, we propose omega, which contains occmamba with an efficient agr - planner to address the above - mentioned problems. occmamba adopts a novel architecture that separates semantic and occupancy prediction into independent branches, incorporating two mamba blocks within these branches. these blocks efficiently extract semantic and geometric features in 3d environments with linear complexity, ensuring that the network can learn long - distance dependencies to improve prediction accuracy. semantic and geometric features are combined within the bird ' s eye view ( bev ) space to minimise computational overhead during feature fusion. the resulting semantic occupancy map is then seamlessly integrated into the local map, providing occlusion awareness of the dynamic environment. our agr - planner utilizes this local map and employs kinodynamic a * search and gradient - based trajectory optimization to guarantee planning is esdf - free and energy - efficient. extensive experiments demonstrate that occmamba outperforms the state - of - the - art 3d semantic occupancy network with 25. 0 % miou. end - to - end navigation experiments in dynamic scenes verify omega ' s efficiency, achieving a 96 % average planning success rate. code and video are available at https : / / jmwang0117. github. io / omega /.
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arxiv:2408.10618
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we theoretically investigate a supersymmetric collective mode called goldstino in a bose - fermi mixture. the explicit supersymmetry breaking, which is unavoidable in cold atom experiments, is considered. we derive the gell - mann - - oakes - renner ( gor ) relation for the goldstino, which gives the relation between the energy gap at the zero momentum and the explicit breaking term. we also numerically evaluate the gap of goldstino above the bose - einstein condensation temperature within the random phase approximation ( rpa ). while the gap obtained from the gor relation coincides with that in the rpa for the mass - balanced system, there is a deviation from the gor relation in the mass - imbalanced system. we point out the deviation becomes large when the goldstino pole is close to the branch point, although it is parametrically a higher order with respect to the mass - imbalanced parameter. to examine the existence of the goldstino pole in realistic cold atomic systems, we show how the mass - imbalance effect appears in $ ^ 6 $ li - $ ^ 7 $ li, $ ^ { 40 } $ k - $ ^ { 41 } $ k, and $ ^ { 173 } $ yb - $ ^ { 174 } $ yb mixtures. furthermore, we analyze the goldstino spectral weight in a $ ^ { 173 } $ yb - $ ^ { 174 } $ yb mixture with realistic interactions and show a clear peak due to the goldstino pole. as a possibility to observe the goldstino spectrum in cold atom experiments, we discuss the effects of the goldstino pole on the fermionic single - particle excitation as well as the relationship between the gor relation and tan ' s contact.
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arxiv:2001.08507
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inferring 3d structures from sparse, unposed observations is challenging due to its unconstrained nature. recent methods propose to predict implicit representations directly from unposed inputs in a data - driven manner, achieving promising results. however, these methods do not utilize geometric priors and cannot hallucinate the appearance of unseen regions, thus making it challenging to reconstruct fine geometric and textural details. to tackle this challenge, our key idea is to reformulate this ill - posed problem as conditional novel view synthesis, aiming to generate complete observations from limited input views to facilitate reconstruction. with complete observations, the poses of the input views can be easily recovered and further used to optimize the reconstructed object. to this end, we propose a novel pipeline pragmatist. first, we generate a complete observation of the object via a multiview conditional diffusion model. then, we use a feed - forward large reconstruction model to obtain the reconstructed mesh. to further improve the reconstruction quality, we recover the poses of input views by inverting the obtained 3d representations and further optimize the texture using detailed input views. unlike previous approaches, our pipeline improves reconstruction by efficiently leveraging unposed inputs and generative priors, circumventing the direct resolution of highly ill - posed problems. extensive experiments show that our approach achieves promising performance in several benchmarks.
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arxiv:2412.08412
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the main goal of this paper is to design a market operator ( mo ) and a distribution network operator ( dno ) for a network of microgrids in consideration of multiple objectives. this is a high - level design and only those microgrids with nondispatchable renewable energy sources are considered. for a power grid in the network, the net value derived from providing power to the network must be maximized. for a microgrid, it is desirable to maximize the net gain derived from consuming the received power. finally, for an independent system operator, stored energy levels at microgrids must be maintained as close as possible to storage capacity to secure network emergency operation. to achieve these objectives, a multiobjective approach is proposed. the price signal generated by the mo and power distributed by the dno are assigned based on a pareto optimal solution of a multiobjective optimization problem. by using the proposed approach, a fair scheme that does not advantage one particular objective can be attained. simulations are provided to validate the proposed methodology.
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arxiv:1705.02123
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image quality assessment is critical to control and maintain the perceived quality of visual content. both subjective and objective evaluations can be utilised, however, subjective image quality assessment is currently considered the most reliable approach. databases containing distorted images and mean opinion scores are needed in the field of atmospheric research with a view to improve the current state - of - the - art methodologies. in this paper, we focus on using ground - based sky camera images to understand the atmospheric events. we present a new image quality assessment dataset containing original and distorted nighttime images of sky / cloud from swinseg database. subjective quality assessment was carried out in controlled conditions, as recommended by the itu. statistical analyses of the subjective scores showed the impact of noise type and distortion level on the perceived quality.
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arxiv:1912.07192
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this article is concerned with random holomorphic polynomials and their generalizations to algebraic and symplectic geometry. a natural algebro - geometric generalization studied in our prior work involves random holomorphic sections $ h ^ 0 ( m, l ^ n ) $ of the powers of any positive line bundle $ l \ to m $ over any complex manifold. our main interest is in the statistics of zeros of $ k $ independent sections ( generalized polynomials ) of degree $ n $ as $ n \ to \ infty $. we fix a point $ p $ and focus on the ball of radius $ 1 / \ sqrt { n } $ about $ p $. under a microscope magnifying the ball by the factor $ \ sqrt { n } $, the statistics of the configurations of simultaneous zeros of random $ k $ - tuples of sections tends to a universal limit independent of $ p, m, l $. we review this result and generalize it further to the case of pre - quantum line bundles over almost - complex symplectic manifolds $ ( m, j, \ omega ) $. following [ sz2 ], we replace $ h ^ 0 ( m, l ^ n ) $ in the complex case with the ` asymptotically holomorphic ' sections defined by boutet de monvel - guillemin and ( from another point of view ) by donaldson and auroux. using a generalization to an $ m $ - dimensional setting of the kac - rice formula for zero correlations together with the results of [ sz2 ], we prove that the scaling limits of the correlation functions for zeros of random $ k $ - tuples of asymptotically holomorphic sections belong to the same universality class as in the complex case.
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arxiv:math-ph/0002039
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achieving self - consistent simultaneous interpretations of pions and kaons as bound states of quark and antiquark and as the ( almost ) massless boson states related, according to goldstone ' s theorem, to the dynamical ( and explicit ) breakdown of the chiral symmetries of qcd still represents a major challenge. applying inversion techniques to conveniently simplified versions of the homogeneous bethe - salpeter equation, governing bound states in quantum field theory, enables us to get along a straightforward route a qualitative idea of how the underlying effective interaction might look like.
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arxiv:1709.02130
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hamiltonian monte carlo ( hmc ) is an efficient and effective means of sampling posterior distributions on euclidean space, which has been extended to manifolds with boundary. however, some applications require an extension to more general spaces. for example, phylogenetic ( evolutionary ) trees are defined in terms of both a discrete graph and associated continuous parameters ; although one can represent these aspects using a single connected space, this rather complex space is not suitable for existing hmc algorithms. in this paper, we develop probabilistic path hmc ( pphmc ) as a first step to sampling distributions on spaces with intricate combinatorial structure. we define pphmc on orthant complexes, show that the resulting markov chain is ergodic, and provide a promising implementation for the case of phylogenetic trees in open - source software. we also show that a surrogate function to ease the transition across a boundary on which the log - posterior has discontinuous derivatives can greatly improve efficiency.
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arxiv:1702.07814
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the detection of telecom fraud faces significant challenges due to the lack of high - quality multimodal training data that integrates audio signals with reasoning - oriented textual analysis. to address this gap, we present teleantifraud - 28k, the first open - source audio - text slow - thinking dataset specifically designed for automated telecom fraud analysis. our dataset is constructed through three strategies : ( 1 ) privacy - preserved text - truth sample generation using automatically speech recognition ( asr ) - transcribed call recordings ( with anonymized original audio ), ensuring real - world consistency through text - to - speech ( tts ) model regeneration ; ( 2 ) semantic enhancement via large language model ( llm ) - based self - instruction sampling on authentic asr outputs to expand scenario coverage ; ( 3 ) multi - agent adversarial synthesis that simulates emerging fraud tactics through predefined communication scenarios and fraud typologies. the generated dataset contains 28, 511 rigorously processed speech - text pairs, complete with detailed annotations for fraud reasoning. the dataset is divided into three tasks : scenario classification, fraud detection, fraud type classification. furthermore, we construct teleantifraud - bench, a standardized evaluation benchmark comprising proportionally sampled instances from the dataset, to facilitate systematic testing of model performance on telecom fraud detection tasks. we also contribute a production - optimized supervised fine - tuning ( sft ) model trained on hybrid real / synthetic data, while open - sourcing the data processing framework to enable community - driven dataset expansion. this work establishes a foundational framework for multimodal anti - fraud research while addressing critical challenges in data privacy and scenario diversity. the project will be released at https : / / github. com / jimmyma99 / teleantifraud.
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arxiv:2503.24115
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we formulate and study a general time - varying multi - agent system where players repeatedly compete under incomplete information. our work is motivated by scenarios commonly observed in online advertising and retail marketplaces, where agents and platform designers optimize algorithmic decision - making in dynamic competitive settings. in these systems, no - regret algorithms that provide guarantees relative to \ emph { static } benchmarks can perform poorly and the distributions of play that emerge from their interaction do not correspond anymore to static solution concepts such as coarse correlated equilibria. instead, we analyze the interaction of \ textit { dynamic benchmark } consistent policies that have performance guarantees relative to \ emph { dynamic } sequences of actions, and through a novel \ textit { tracking error } notion we delineate when their empirical joint distribution of play can approximate an evolving sequence of static equilibria. in systems that change sufficiently slowly ( sub - linearly in the horizon length ), we show that the resulting distributions of play approximate the sequence of coarse correlated equilibria, and apply this result to establish improved welfare bounds for smooth games. on a similar vein, we formulate internal dynamic benchmark consistent policies and establish that they approximate sequences of correlated equilibria. our findings therefore suggest that, in a broad range of multi - agent systems where non - stationarity is prevalent, algorithms designed to compete with dynamic benchmarks can improve both individual and welfare guarantees, and their emerging dynamics approximate a sequence of static equilibrium outcomes.
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arxiv:2501.11897
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particles trapped at a fluid - fluid interface by capillary forces can form a monolayer that jams and buckles when subject to uni - axial compression. here we investigate experimentally the buckling mechanics of monolayers of millimeter - sized rigid plates trapped at a planar fluid - fluid interface subject to uni - axial compression in a langmuir trough. we quantified the buckling wavelength and the associated force on the trough barriers as a function of the degree of compression. to explain the observed buckling wavelength and forces in the two - dimensional monolayer, we consider a simplified system composed of a linear chain of plate - like particles. the chain system enables us to build a theoretical model which is then compared to the two - dimensional monolayer data. both the experiments and analytical model show that the wavelength of buckling of a monolayer of plate - like particles is of the order of the particle size, a different scaling from the one reported for monolayers of spheres. a simple model of buckling surface pressure is also proposed, and an analysis of the effect of the bending rigidity resulting from a small overlap between nanosheet particles is presented. these results can be applied to the modeling of the interfacial rheology and buckling dynamics of interfacial layers of 2d nanomaterials.
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arxiv:2307.01087
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this paper is concerned with the form and dynamics of shock - acoustic waves ( saw ) generated during rocket launchings. we have developed a method for determining saw parameters ( including angular characteristics of the wave vector, and the saw phase velocity, as well as the direction towards the source ) using gps - arrays whose elements can be chosen out of a large set of gps - stations of the global gps network. the application of the method is illustrated by a case study of ionospheric effects from launchings of launch vehicles ( lv ) proton and space shuttle from space - launch complexes baikonur and kennedy space center ( ksc ) in 1998 and 1999 ( a total of five launchings ). the study revealed that, in spite of a difference of lv characteristics, the ionospheric response for all launchings had the character of an n - wave corresponding to the form of a shock wave, regardless of the disturbance source ( rocket launchings, industrial explosions ). the saw period t is 270 - - 360 s, and the amplitude exceeds the standard deviation of tec background fluctuations in this range of periods under quiet and moderate geomagnetic conditions by factors of 2 to 5 as a minimum. the angle of elevation of the saw wave vector varies from 30 degree to 60 degree, and the saw phase velocity ( 900 - 1200 m / s ) approaches the sound velocity at heights of the ionospheric f - region maximum.
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arxiv:physics/0007043
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we have fabricated a spin - polarized tunneling device based on half metallic manganites incorporating $ ba _ { 2 } lanbo _ { 6 } $ as insulating barrier. an anomalous bias dependence of tunnel magnetoresistance ( tmr ) has been observed, the first of its kind in a symmetric electrode tunnel junction with single insulating barrier. the bias dependence of tmr shows an extremely sharp zero bias anomaly, which can be considered as a demonstration of the drastic density of states variation around the fermi level of the half metal. this serves as a strong evidence for the existence of minority spin tunneling states at the half - metal insulator interface.
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arxiv:cond-mat/0407295
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about 20 percent of all nearby early - type galaxies ( $ m _ { \ star } \ gtrsim 6 \ times 10 ^ { 9 } $ m $ _ { \ odot } $ ) outside the virgo cluster are surrounded by a disc or ring of low - column - density neutral hydrogen ( hi ) gas with typical radii of tens of kpc, much larger than the stellar body. in order to understand the impact of these gas reservoirs on the host galaxies, we analyse the distribution of star formation out to large radii as a function of hi properties using galex uv and sdss optical images. our sample consists of 18 hi - rich galaxies as well as 55 control galaxies where no hi has been detected. in half of the hi - rich galaxies the radial uv profile changes slope at the position of the hi radial profile peak. to study the stellar populations, we calculate the fuv - nuv and uv - optical colours in two apertures, 1 - 3 and 3 - 10 r $ _ { eff } $. we find that hi - rich galaxies are on average 0. 5 and 0. 8 mag bluer than the hi - poor ones, respectively. this indicates that a significant fraction of the uv emission traces recent star formation and is associated with the hi gas. using fuv emission as a proxy for star formation, we estimate the integrated star formation rate in the outer regions ( r > 1r $ _ { eff } $ ) to be on average $ 6 \ times 10 ^ { - 3 } $ m $ _ { \ odot } $ yr $ ^ { - 1 } $ for the hi - rich galaxies. this rate is too low to build a substantial stellar disc and, therefore, change the morphology of the host. we find that the star formation efficiency and the gas depletion time are similar to those at the outskirts of spirals.
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arxiv:1609.03179
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we show that short - range resonating - valence - bond correlations and long - range order can coexist in the ground state ( gs ) of a frustrated spin system. our study comprises a comprehensive investigation of the quantum magnetism on the structurally disorder - free single crystal of cu $ _ 2 $ ( oh ) $ _ 3 $ no $ _ 3 $, which realizes the $ s $ = 1 / 2 heisenberg model on a spatially anisotropic triangular lattice. competing exchange interactions determined by fitting the magnetization measured up to 55 t give rise to an exotic gs wavefunction with coexistence of the dominant short - range resonating - valence - bond correlations and weak long - range stripe order ( ordered moment $ m _ 0 $ = $ | \ langle s _ i ^ z \ rangle | $ $ \ sim $ 0. 02 ). at low temperatures, a first - order spin - flop transition is visible at $ \ sim $ 1 - 3 t. as the applied field further increases, another two magnetic - field - induced quantum phase transitions are observed at $ \ sim $ 14 - 19 and $ \ sim $ 46 - 52 t, respectively. simulations of the heisenberg exchange model show semi - quantitative agreement with the magnetic - field modulation of these unconventional phases, as well as the absence of visible magnetic reflections in neutron diffraction, thus supporting the gs of the spin system of cu $ _ 2 $ ( oh ) $ _ 3 $ no $ _ 3 $ may be approximate to a quantum spin liquid. our study establishes structurally disorder - free magnetic materials with spatially anisotropic exchange interactions as a possible arena for spin liquids.
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arxiv:2208.00382
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person re - identification ( re - id ) aims to match identities across non - overlapping camera views. researchers have proposed many supervised re - id models which require quantities of cross - view pairwise labelled data. this limits their scalabilities to many applications where a large amount of data from multiple disjoint camera views is available but unlabelled. although some unsupervised re - id models have been proposed to address the scalability problem, they often suffer from the view - specific bias problem which is caused by dramatic variances across different camera views, e. g., different illumination, viewpoints and occlusion. the dramatic variances induce specific feature distortions in different camera views, which can be very disturbing in finding cross - view discriminative information for re - id in the unsupervised scenarios, since no label information is available to help alleviate the bias. we propose to explicitly address this problem by learning an unsupervised asymmetric distance metric based on cross - view clustering. the asymmetric distance metric allows specific feature transformations for each camera view to tackle the specific feature distortions. we then design a novel unsupervised loss function to embed the asymmetric metric into a deep neural network, and therefore develop a novel unsupervised deep framework named the deep clustering - based asymmetric metric learning ( decamel ). in such a way, decamel jointly learns the feature representation and the unsupervised asymmetric metric. decamel learns a compact cross - view cluster structure of re - id data, and thus help alleviate the view - specific bias and facilitate mining the potential cross - view discriminative information for unsupervised re - id. extensive experiments on seven benchmark datasets whose sizes span several orders show the effectiveness of our framework.
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arxiv:1901.10177
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delay - and - sum ( das ) algorithms are widely used for beamforming in linear array photoacoustic imaging systems and are characterized by fast execution. however, these algorithms suffer from various drawbacks like low resolution, low contrast, high sidelobe artifacts and lack of visual coherence. more recently, adaptive weighting was introduced to improve the reconstruction image quality. unfortunately, the existing state - of - the - art adaptive beamforming algorithms are computationally expensive and do not consider the specific noise characteristics of the acquired ultrasonic signal. in this article, we present a new adaptive weighting factor named the variational coherence factor ( vcf ), which takes into account the noise level variations of radio - frequency data. the proposed technique provides superior results in terms of image resolution, sidelobe reduction, signal - to - noise and contrast level improvement. the quantitative results of the numerical simulations and phantom imaging show that the proposed vcf assisted das method leads to 55 % and 25 % improvement in fwhm, 57 % and 32 % improvement in snr, respectively, compared to the state - of - the - art das - based methods. the results demonstrate that the proposed method can effectively improve the reconstructed image quality and deliver satisfactory imaging performance even with a limited number of sensor elements. the proposed method can potentially reduce the instrumentation cost of the photoacoustic imaging system and contribute toward the clinical translation of the modality.
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arxiv:2011.08414
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we study fractional laplace motion ( flm ) obtained from subordination of fractional brownian motion to a gamma process, in the presence of an external drift that acts on the composite process or of an internal drift acting solely on the parental process. we derive the statistical properties of this flm process and find that the external drift does not influence the mean - squared displacement ( msd ), whereas the internal drift leads to normal diffusion, dominating at long times in the subdiffusive hurst exponent regime. we also investigate the intricate properties of the probability density function ( pdf ), demonstrating that it possesses a central gaussian region, whose expansion in time is influenced by fbm ' s hurst exponent. outside of this region the pdf follows a non - gaussian pattern. the kurtosis of this flm process converges toward the gaussian limit at long times insensitive to the extreme non - gaussian tails. additionally, in the presence of the external drift, the pdf remains symmetric and centered at $ x = vt $. in contrast, for the internal drift this symmetry is broken. the results of our computer simulations are fully consistent with the theoretical predictions. the flm model is suitable for describing stochastic processes with a non - gaussian pdf and long - ranged correlations of the motion.
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arxiv:2412.14674
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quantum key distribution ( qkd ) allows two parties to establish a shared secret key that is secure against all - powerful adversaries. one such protocol named b92 is quite appealing due to its simplicity but is highly sensitive to channel noise. in this work, we investigate a high - dimensional variant of an extended version of the b92 protocol and show that it can distill a key over high noise channels. the protocol we consider requires that alice send only three high - dimensional states and bob only perform partial measurements. we perform an information - theoretic security analysis of our protocol and compare its key rate to that of a high - dimensional bb84 protocol over depolarization and amplitude damping channels.
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arxiv:2106.11460
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we present the experimental and numerical studies of a 2d sheared amorphous material constituted of bidisperse photo - elastic disks. we analyze the statistics of avalanches during shear including the local and global fluctuations in energy and changes in particle positions and orientations. we find scale free distributions for these global and local avalanches denoted by power - laws whose cut - offs vary with inter - particle friction and packing fraction. different exponents are found for these power - laws depending on the quantity from which variations are extracted. an asymmetry in time of the avalanche shapes is evidenced along with the fact that avalanches are mainly triggered from the shear bands. a simple relation independent from the intensity, is found between the number of local avalanches and the global avalanches they form. we also compare these experimental and numerical results for both local and global fluctuations to predictions from meanfield and depinning theories.
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arxiv:1709.01012
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