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within the two antenna model, we develop a theory of the recently observed helicity - sensitive detection of terahertz radiation by fets. the effect arises because of the mixing of the ac signals produced in the channel by the two antennas. we calculate the helicity - dependent part of the photoresponse and its dependence on the antenna impedance, gate length, and gate voltage.
arxiv:1303.0144
half - metallic ferrimagnetism is crucial for spintronic applications with respect to ferromagnets due to the lower stray fields created by these materials. studying the effect of defects in cras and related transition - metal chalcogenides and pnictides crystallizing in the zinc - blende structure, we reveal that the excess of the transition - metal atoms leads to half - metallic ferrimagnetism. the surplus of these atoms are antiferromagnetically coupled to the transition - metal atoms sitting at the perfect lattice sites. the needed condition to achieve half - metallic ferrimagnetism is to prevent the migration of the $ sp $ atoms to other sites and the atomic swaps.
arxiv:cond-mat/0606286
this paper has been withdrawn
arxiv:quant-ph/0611120
income distribution. it rejected the classical economics ' labour theory of value in favour of a marginal utility theory of value on the demand side and a more comprehensive theory of costs on the supply side. in the 20th century, neoclassical theorists departed from an earlier idea that suggested measuring total utility for a society, opting instead for ordinal utility, which posits behaviour - based relations across individuals. in microeconomics, neoclassical economics represents incentives and costs as playing a pervasive role in shaping decision making. an immediate example of this is the consumer theory of individual demand, which isolates how prices ( as costs ) and income affect quantity demanded. in macroeconomics it is reflected in an early and lasting neoclassical synthesis with keynesian macroeconomics. neoclassical economics is occasionally referred as orthodox economics whether by its critics or sympathisers. modern mainstream economics builds on neoclassical economics but with many refinements that either supplement or generalise earlier analysis, such as econometrics, game theory, analysis of market failure and imperfect competition, and the neoclassical model of economic growth for analysing long - run variables affecting national income. neoclassical economics studies the behaviour of individuals, households, and organisations ( called economic actors, players, or agents ), when they manage or use scarce resources, which have alternative uses, to achieve desired ends. agents are assumed to act rationally, have multiple desirable ends in sight, limited resources to obtain these ends, a set of stable preferences, a definite overall guiding objective, and the capability of making a choice. there exists an economic problem, subject to study by economic science, when a decision ( choice ) is made by one or more players to attain the best possible outcome. = = = keynesian economics = = = keynesian economics derives from john maynard keynes, in particular his book the general theory of employment, interest and money ( 1936 ), which ushered in contemporary macroeconomics as a distinct field. the book focused on determinants of national income in the short run when prices are relatively inflexible. keynes attempted to explain in broad theoretical detail why high labour - market unemployment might not be self - correcting due to low " effective demand " and why even price flexibility and monetary policy might be unavailing. the term " revolutionary " has been applied to the book in its impact on economic analysis. during the following decades, many economists followed keynes ' ideas and expanded on his works. john hicks and alvin hansen developed the is – lm model which was a simple formalisation of some
https://en.wikipedia.org/wiki/Economics
in this paper, we extend the fractional sobolev spaces with variable exponents $ w ^ { s, p ( x, y ) } $ to include the general fractional case $ w ^ { k, p ( x, y ) } $, where $ p $ is a variable exponent, $ s \ in ( 0, 1 ) $ and $ k $ is a suitable kernel. we are concerned with some qualitative properties of the space $ w ^ { k, p ( x, y ) } $ ( completeness, reflexivity, separability, and density ). moreover, we prove a continuous and compact embedding theorem of these spaces into variable exponent lebesgue spaces. as applications, we discuss the existence of a nontrivial solution for a nonlocal $ p ( x,. ) $ - kirchhoff type problem. further, we establish the existence and uniqueness of a solution for a variational problem involving the integro - differential operator of elliptic type $ \ mathcal { l } ^ { p ( x,. ) } _ k $.
arxiv:1901.05687
the value of a highly oscillatory integral is typically determined asymptotically by the behaviour of the integrand near a small number of critical points. these include the endpoints of the integration domain and the so - called stationary points or saddle points - - roots of the derivative of the phase of the integrand - - where the integrand is locally non - oscillatory. modern methods for highly oscillatory quadrature exhibit numerical issues when two such saddle points coalesce. on the other hand, integrals with coalescing saddle points are a classical topic in asymptotic analysis, where they give rise to uniform asymptotic expansions in terms of the airy function. in this paper we construct gaussian quadrature rules that remain uniformly accurate when two saddle points coalesce. these rules are based on orthogonal polynomials in the complex plane. we analyze these polynomials, prove their existence for even degrees, and describe an accurate and efficient numerical scheme for the evaluation of oscillatory integrals with coalescing saddle points.
arxiv:1806.06549
we investigate the capacity of bosonic quantum channels for the transmission of quantum information. achievable rates are determined from measurable moments of the channel by showing that every channel can asymptotically simulate a gaussian channel which is characterized by second moments of the initial channel. we calculate the quantum capacity for a class of gaussian channels, including channels describing optical fibers with photon losses, by proving that gaussian encodings are optimal. along the way we provide a complete characterization of degradable gaussian channels and those arising from teleportation protocols.
arxiv:quant-ph/0606132
tidal perturbations play an important role in the study of the dynamics in the classical two - body system. understanding tidal effects in strong - field regions may allow one to use gravitational - wave or electromagnetic observations to locate or constraint the location of possible companions. here, we investigate how timelike and null geodesics of a schwarzschild black hole are affected in the presence of a companion. there is a panoply of new effects. in some limiting cases, we find analytical solutions for closed null or timelike geodesics. our results show that light ring period as measured by a far - away observer can be eiter shorter or longer, depending on the location of the companion. we also show that there are closed lightlike trajectories which are elliptic ( for equatorial companions ), and that timelike particles are affected in a similar manner. finally, we attempt at estimating the ringdown from tidally perturbed geometries. our results indicate that there are two stages in the relaxation of such geometries, one associated with a prompt decay of waves around the deformed photonsphere, and a later relaxation of the global geometry. these results are consistent with previous, full numerical studies.
arxiv:2106.06551
we describe a phase transition for long - range entanglement in a three - dimensional cluster state affected by noise. the partially decohered state is modeled by the thermal state of a suitable hamiltonian. we find that the temperature at which the entanglement length changes from infinite to finite is nonzero. we give an upper and lower bound to this transition temperature.
arxiv:quant-ph/0407255
we study the entanglement generated by a weak cross - kerr nonlinearity between two initial coherent states, one of which has an amplitude close to the single - photon level, while the other one is macroscopic. we show that strong micro - macro entanglement is possible for weak phase shifts by choosing the amplitude of the macroscopic beam sufficiently large. we analyze the effects of loss and discuss possible experimental demonstrations of the micro - macro entanglement based on homodyne tomography and on a new entanglement witness.
arxiv:1412.3090
, efficiently and with high quality ; in rooms, through public address systems and through mobile telephone systems are important areas of study. = = practitioner = = a variety of terms are used to describe audio engineers who install or operate sound recording, sound reinforcement, or sound broadcasting equipment, including large and small format consoles. terms such as audio technician, sound technician, audio engineer, audio technologist, recording engineer, sound mixer, mixing engineer and sound engineer can be ambiguous ; depending on the context they may be synonymous, or they may refer to different roles in audio production. such terms can refer to a person working in sound and music production ; for instance, a sound engineer or recording engineer is commonly listed in the credits of commercial music recordings ( as well as in other productions that include sound, such as movies ). these titles can also refer to technicians who maintain professional audio equipment. certain jurisdictions specifically prohibit the use of the title engineer to any individual not a registered member of a professional engineering licensing body. in the recording studio environment, a sound engineer records, edits, manipulates, mixes, or masters sound by technical means to realize the creative vision of the artist and record producer. while usually associated with music production, an audio engineer deals with sound for a wide range of applications, including post - production for video and film, live sound reinforcement, advertising, multimedia, and broadcasting. in larger productions, an audio engineer is responsible for the technical aspects of a sound recording or other audio production, and works together with a record producer or director, although the engineer ' s role may also be integrated with that of the producer. in smaller productions and studios the sound engineer and producer are often the same person. in typical sound reinforcement applications, audio engineers often assume the role of producer, making artistic and technical decisions, and sometimes even scheduling and budget decisions. = = = education and training = = = audio engineers come from backgrounds or postsecondary training in fields such as audio, fine arts, broadcasting, music, or electrical engineering. training in audio engineering and sound recording is offered by colleges and universities. some audio engineers are autodidacts with no formal training, but who have attained professional skills in audio through extensive on - the - job experience. audio engineers must have extensive knowledge of audio engineering principles and techniques. for instance, they must understand how audio signals travel, which equipment to use and when, how to mic different instruments and amplifiers, which microphones to use and how to position them to get the best quality recordings. in addition to technical knowledge,
https://en.wikipedia.org/wiki/Audio_engineer
monte carlo simulations with an effective hamiltonian parametrized from first principles are performed to study the dielectric response of batio3 as a function of temperature, with particular emphasis on the behavior of the dielectric constant near the transition from the ferroelectric tetragonal phase to the paraelectric cubic phase.
arxiv:cond-mat/9802208
we re - analyze the leading twist light - cone distributions for transversely polarized \ rho -, \ rho ' - and b _ 1 - mesons in the framework of qcd sum rules with nonlocal condensates. using different kinds of sum rules to obtain reliable predictions, we estimate the 2 -, 4 -, 6 - and 8 - th moments for transversely polarized \ rho - and \ rho ' - meson distributions and re - estimate tensor couplings f ^ t _ { \ rho, \ rho ', b _ 1 }. we stress that the results of standard sum rules also support our estimation of the second moment of the transversely polarized \ rho - meson distribution. new models for light - cone distributions of these mesons are constructed. phenomenological consequences from these distributions are briefly discussed. our results are compared with those found by ball and braun ( 1996 ), and the latter is shown to be incomplete.
arxiv:hep-ph/0006206
in computational fluid dynamics ( cfd ), coarse mesh simulations offer computational efficiency but often lack precision. applying conventional super - resolution to these simulations poses a significant challenge due to the fundamental contrast between downsampling high - resolution images and authentically emulating low - resolution physics. the former method conserves more of the underlying physics, surpassing the usual constraints of real - world scenarios. we propose a novel definition of super - resolution tailored for pde - based problems. instead of simply downsampling from a high - resolution dataset, we use coarse - grid simulated data as our input and predict fine - grid simulated outcomes. employing a physics - infused unet upscaling method, we demonstrate its efficacy across various 2d - cfd problems such as discontinuity detection in burger ' s equation, methane combustion, and fouling in industrial heat exchangers. our method enables the generation of fine - mesh solutions bypassing traditional simulation, ensuring considerable computational saving and fidelity to the original ground truth outcomes. through diverse boundary conditions during training, we further establish the robustness of our method, paving the way for its broad applications in engineering and scientific cfd solvers.
arxiv:2311.09740
increasingly, with the data collected at the lhc we are confronted with the possible existence of flow in pp collisions. in this work we show that pythia 8 produces flow - like effects in events with multiple hard subcollisions due to color string formations between final partons from independent hard scatterings, the so called color reconnection. we present studies of different identified hadron observables in pp collisions at 7 tev with the tune 4c. studies have been done both for minimum bias and multiplicity intervals in events with and without color reconnection to isolate the flow - like effect.
arxiv:1303.6326
in this paper, we formulate acoustic howling suppression ( ahs ) as a supervised learning problem and propose a deep learning approach, called deep ahs, to address it. deep ahs is trained in a teacher forcing way which converts the recurrent howling suppression process into an instantaneous speech separation process to simplify the problem and accelerate the model training. the proposed method utilizes properly designed features and trains an attention based recurrent neural network ( rnn ) to extract the target signal from the microphone recording, thus attenuating the playback signal that may lead to howling. different training strategies are investigated and a streaming inference method implemented in a recurrent mode used to evaluate the performance of the proposed method for real - time howling suppression. deep ahs avoids howling detection and intrinsically prohibits howling from happening, allowing for more flexibility in the design of audio systems. experimental results show the effectiveness of the proposed method for howling suppression under different scenarios.
arxiv:2302.09252
the book graph $ b _ n ^ { ( k ) } $ consists of $ n $ copies of $ k _ { k + 1 } $ joined along a common $ k _ k $. the ramsey numbers of $ b _ n ^ { ( k ) } $ are known to have strong connections to the classical ramsey numbers of cliques. recently, the first author determined the asymptotic order of these ramsey numbers for fixed $ k $, thus answering an old question of erd \ h { o } s, faudree, rousseau, and schelp. in this paper, we first provide a simpler proof of this theorem. next, answering a question of the first author, we present a different proof that avoids the use of szemer \ ' edi ' s regularity lemma, thus providing much tighter control on the error term. finally, we prove a conjecture of nikiforov, rousseau, and schelp by showing that all extremal colorings for this ramsey problem are quasirandom.
arxiv:2001.00407
in this paper we propose a method to study a general vector - hosts mathematical model in order to explain how the changes in biodiversity could influence the dynamics of vector - borne diseases. we find that under the assumption of frequency - dependent transmission, i. e. the assumption that the number of contacts are diluted by the total population of hosts, the presence of a competent host is a necessary condition for the existence of an endemic state. in addition, we obtain that in the case of an endemic disease with a unique competent and resilient host, an increase in its density amplifies the disease.
arxiv:1705.09426
the amount of information exchanged per unit of time between two nodes in a dynamical network or between two data sets is a powerful concept for analysing complex systems. this quantity, known as the mutual information rate ( mir ), is calculated from the mutual information, which is rigorously defined only for random systems. moreover, the definition of mutual information is based on probabilities of significant events. this work offers a simple alternative way to calculate the mir in dynamical ( deterministic ) networks or between two data sets ( not fully deterministic ), and to calculate its upper and lower bounds without having to calculate probabilities, but rather in terms of well known and well defined quantities in dynamical systems. as possible applications of our bounds, we study the relationship between synchronisation and the exchange of information in a system of two coupled maps and in experimental networks of coupled oscillators.
arxiv:1104.3498
motivated by the controllability / reachability problems for switched linear control systems and some classes of nonlinear ( mechanical ) control systems we address a related problem of existence of a cyclic vector for an associative ( matrix ) algebra. we provide a sufficient criterion for existence of cyclic vector and draw conclusions for controllability.
arxiv:1503.08044
automatic speech recognition involves mainly two steps ; feature extraction and classification. mel frequency cepstral coefficient is used as one of the prominent feature extraction techniques in asr. usually, the set of all 12 mfcc coefficients is used as the feature vector in the classification step. but the question is whether the same or improved classification accuracy can be achieved by using a subset of 12 mfcc as feature vector. in this paper, fisher ' s ratio technique is used for selecting a subset of 12 mfcc coefficients that contribute more in discriminating a pattern. the selected coefficients are used in classification with hidden markov model algorithm. the classification accuracies that we get by using 12 coefficients and by using the selected coefficients are compared.
arxiv:1505.03239
we review angle resolved photoemission spectroscopy ( arpes ) results on the high tc superconductors, focusing primarily on results obtained on the quasi - two dimensional cuprate bi2sr2cacu2o8 and its single layer counterpart bi2sr2cuo6. the topics treated include the basics of photoemission and methodologies for analyzing spectra, normal state electronic structure including the fermi surface, the superconducting energy gap, the normal state pseudogap, and the electron self - energy as determined from photoemission lineshapes.
arxiv:cond-mat/0209476
} $ - harmonic maps, $ p $ - harmonic maps, $ \ phi _ { s } $ - harmonic maps, $ \ phi _ { s, p } $ - harmonic maps, $ \ phi _ { ( 2 ) } $ - harmonic maps, etc., ( cf. [ 21, 40, 42, 41, 12, 13 ] ).
arxiv:2305.19503
we develop a statistical estimator to infer the redshift probability distribution of a photometric sample of galaxies from its angular cross - correlation in redshift bins with an overlapping spectroscopic sample. this estimator is a minimum variance weighted quadratic function of the data : a quadratic estimator. this extends and modifies the methodology presented by mcquinn & white ( 2013 ). the derived source redshift distribution is degenerate with the source galaxy bias, which must be constrained via additional assumptions. we apply this estimator to constrain source galaxy redshift distributions in the kilo - degree imaging survey through cross - correlation with the spectroscopic 2 - degree field lensing survey, presenting results first as a binned step - wise distribution in the range z < 0. 8, and then building a continuous distribution using a gaussian process model. we demonstrate the robustness of our methodology using mock catalogues constructed from n - body simulations, and comparisons with other techniques for inferring the redshift distribution.
arxiv:1611.07578
in this paper, we present an analysis of a chiral cosmological scenario from the perspective of k - essence formalism. in this setup, several scalar fields interact within the kinetic and potential sectors. however, we only consider a flat friedmann - - robertson - - lama \ ^ { \ i } tre - - walker universe coupled minimally to two quintom fields : one quintessence and one phantom. we examine a classical cosmological framework, where analytical solutions are obtained. indeed, we present an explanation of the ` ` big - bang ' ' singularity by means of a ` ` big - bounce ' '. moreover, having a barotropic fluid description and for a particular set of parameters, the phantom line is in fact crossed. additionally, for the quantum counterpart, the wheeler - - dewitt equation is analytically solved for various instances, where the factor - ordering problem has been taken into account ( measured by the factor q ). hence, this approach allows us to compute the probability density of the previous two classical subcases. it turns out that its behavior is in effect damped as the scale factor and the scalar fields evolve. it also tends towards the phantom sector when the factor ordering constant $ \ rm q \ ll 0 $.
arxiv:2204.12083
neutrinoless double - beta decay experiments can potentially determine the majorana or dirac nature of the neutrino, and aid in understanding the neutrino absolute mass scale and hierarchy. future 76ge - based searches target a half - life sensitivity of > 10 ^ 27 y to explore the inverted neutrino mass hierarchy. reaching this sensitivity will require a background rate of < 1 count tonne ^ - 1 y ^ - 1 in a 4 - kev - wide spectral region of interest surrounding the q value of the decay. we investigate the overburden required to reach this background goal in a tonne - scale experiment with a compact ( copper and lead ) shield based on monte carlo calculations of cosmic - ray background rates. we find that, in light of the presently large uncertainties in these types of calculations, a site with an underground depth > ~ 5200 mwe is required for a tonne - scale experiment with a compact shield similar to the planned 40 - kg majorana demonstrator. the required overburden is highly dependent on the chosen shielding configuration and could be relaxed significantly if, for example, a liquid cryogen and water shield, or an active neutron shield were employed. operation of the majorana demonstrator and gerda detectors will serve to reduce the uncertainties on cosmic - ray background rates and will impact the choice of shielding style and location for a future tonne - scale experiment. 4 / 2013 : the peer review process revealed that one of the veto rejection factors ( the factor - of - 4 described on p12 ) needs to be better established. our reevaluation of this parameter to date has not yielded strong support for the value stated in the manuscript, and we require further study to develop a solid estimate. this further study will supersede the work described in this manuscript, and may or may not lead to the same conclusion regarding the ~ > 5200 mwe requirement for future tonne - scale 76ge neutrinoless double beta decay experiments.
arxiv:1109.4154
in a previous work we proved that each $ n $ - dimensional convex polyhedron $ { \ mathcal k } subset { \ mathbb r } ^ n $ and its relative interior are regular images of $ { \ mathbb r } ^ n $. as the image of a non - constant polynomial map is an unbounded semialgebraic set, it is not possible to substitute regular maps by polynomial maps in the previous statement. in this work we determine constructively all unbounded $ n $ - dimensional convex polyhedra $ { \ mathcal k } \ subset { \ mathbb r } ^ n $ that are polynomial images of $ { \ mathbb r } ^ n $. we also analyze for which of them the interior $ { \ rm int } ( { \ mathcal k } ) $ is a polynomial image of $ { \ mathbb r } ^ n $. a discriminating object is the recession cone $ \ vec { \ mathcal c } ( { \ mathcal k } ) $ of $ { \ mathcal k } $. namely, \ em $ { \ mathcal k } $ is a polynomial image of $ { \ mathbb r } ^ n $ if and only if $ \ vec { { \ mathcal c } } ( { \ mathcal k } ) $ has dimension $ n $ \ em. in addition, \ em $ { \ rm int } ( { \ mathcal k } ) $ is a polynomial image of $ { \ mathbb r } ^ n $ if and only if $ \ vec { { \ mathcal c } } ( { \ mathcal k } ) $ has dimension $ n $ and $ { \ mathcal k } $ has no bounded faces of dimension $ n - 1 $ \ em. a key result is an improvement of pecker ' s elimination of inequalities to represent semialgebraic sets as projections of algebraic sets. empirical approaches suggest us that there are ` few ' polynomial maps that have a concrete convex polyhedron as a polynomial image and that there are even fewer for which it is affordable to show that their images actually correspond to our given convex polyhedron. this search of a ` needle in the haystack ' justifies somehow the technicalities involved in our constructive proofs.
arxiv:2401.12558
we report on the evolution with magnetic field and temperature of the vortex lattice ( vl ) in fully - oxygenated yba2cu3o7 as studied by time - of - flight small angle neutron scattering. using the hfm / exed beamline, we have obtained data up to 25. 9 t - much higher than that available previously. our vl structure results indicate the progressive suppression by field of the superconductivity along the crystallographic b ( cuo chain ) direction. the intensity of the diffracted signal reveals the spatial variation of magnetization caused by the vl ( the " form factor " ). instead of a rapid fall - off with field, as seen in superconductors with smaller upper critical fields, we find that the form factor is almost constant with field above about 12 t. we speculate that this is due to pauli paramagnetic moments, which increase at high fields due to alignment of the spins of quasiparticles in the vortex cores.
arxiv:2203.01705
high - definition maps ( hd maps ) play a crucial role in the development, safety validation, and operation of highly automated vehicles. efficiently collecting up - to - date sensor data from road segments and obtaining accurate maps from these are key challenges in hd map creation. commonly used methods, such as dedicated measurement vehicles and crowd - sourced data from series vehicles, often face limitations in commercial viability. although high - resolution aerial imagery offers a cost - effective or even free alternative, it requires significant manual effort and time to transform it into maps. in this paper, we introduce a semi - automatic method for creating hd maps from high - resolution aerial imagery. our method involves training neural networks to semantically segment aerial images into classes relevant to hd maps. the resulting segmentation is then hierarchically post - processed to generate a prototypical hd map of visible road elements. exporting the map to the lanelet2 format allows easy extension for different use cases using standard tools. to train and evaluate our method, we created a dataset using public aerial imagery of urban road segments in germany. in our evaluation, we achieved an automatic mapping of lane markings and road borders with a recall and precision exceeding 96 %. the source code for our method is publicly available at https : / / github. com / robertkrajewski / deepaerialmapper.
arxiv:2410.00769
recent advances in tracking sensors and pose estimation software enable smart systems to use trajectories of skeleton joint locations for supervised learning. we study the problem of accurately recognizing sign language words, which is key to narrowing the communication gap between hard and non - hard of hearing people. our method explores a geometric feature space that we call ` sub - skeleton ' aspects of movement. we assess similarity of feature space trajectories using natural, speed invariant distance measures, which enables clear and insightful nearest neighbor classification. the simplicity and scalability of our basic method allows for immediate application in different data domains with little to no parameter tuning. we demonstrate the effectiveness of our basic method, and a boosted variation, with experiments on data from different application domains and tracking technologies. surprisingly, our simple methods improve sign recognition over recent, state - of - the - art approaches.
arxiv:2202.01390
a purely relational account of the true xquery semantics can turn any relational database system into an xquery processor. compiling nested expressions of the fully compositional xquery language, however, yields odd algebraic plan shapes featuring scattered distributions of join operators that currently overwhelm commercial sql query optimizers. this work rewrites such plans before submission to the relational database back - end. once cast into the shape of join graphs, we have found off - the - shelf relational query optimizers - - the b - tree indexing subsystem and join tree planner, in particular - - to cope and even be autonomously capable of " reinventing " advanced processing strategies that have originally been devised specifically for the xquery domain, e. g., xpath step reordering, axis reversal, and path stitching. performance assessments provide evidence that relational query engines are among the most versatile and efficient xquery processors readily available today.
arxiv:0810.4809
in this paper we deal with linear systems of p ^ 3 through fat points. we consider the behavior of these systems under a cubo - cubic cremona transformation that allows us to produce a class of special systems which we conjecture to be the only ones.
arxiv:math/0311445
we introduce noisy feature mixup ( nfm ), an inexpensive yet effective method for data augmentation that combines the best of interpolation based training and noise injection schemes. rather than training with convex combinations of pairs of examples and their labels, we use noise - perturbed convex combinations of pairs of data points in both input and feature space. this method includes mixup and manifold mixup as special cases, but it has additional advantages, including better smoothing of decision boundaries and enabling improved model robustness. we provide theory to understand this as well as the implicit regularization effects of nfm. our theory is supported by empirical results, demonstrating the advantage of nfm, as compared to mixup and manifold mixup. we show that residual networks and vision transformers trained with nfm have favorable trade - offs between predictive accuracy on clean data and robustness with respect to various types of data perturbation across a range of computer vision benchmark datasets.
arxiv:2110.02180
ferromagnetic ( fm ) semimetals fe $ _ n $ gete $ _ 2 $ ( n = 3, 4, 5 ), exhibit several symmetry - protected band - crossing points or lines near the fermi energy ( e $ _ f $ ) and these topological properties of energy bands lead to interesting transport properties. we study these materials employing the first - principle calculations and the tight - binding hamiltonian constructed by fitting the parameters of the first principles calculation. in the presence of spin - orbit coupling ( soc ) for n = 3, 5 a large berry curvature ( bc ) concentrated on the nodal lines is observed. the consequence of the correlation of the topological nodal line and magnetic moments on anomalous hall conductivity ( ahc ) $ \ sigma _ { xy } $ and anomalous nernst conductivity ( anc ) $ \ alpha _ { xy } $ have been investigated. we find $ \ sigma _ { xy } = 150 $ s / cm for n = 3, 295 s / cm for n = 4, and 90 s / cm for n = 5 at 0 k, while the anc is observed as $ \ alpha _ { xy } = 0. 55 $ a / km for n = 3, 0. 10 a / km for n = 5, and 0. 80 a / km for n = 4, at the e $ _ f $ at room temperature. our calculated ahc values at 0 k, i. e., 150 s / cm for fe $ _ 3 $ gete $ _ 2 $ and 90 s / cm fe $ _ 5 $ gete $ _ 2 $, are consistent with the experimentally reported values. also the experimentally reported value of anc for fe $ _ 5 $ gete $ _ 2 $ is close to our calculated value at room temperature, i. e., 0. 10 a / km.
arxiv:2207.03547
in this paper, a self - triggered scheme is proposed to optimally control the traffic flow of connected and automated vehicles ( cavs ) at conflict areas of a traffic network with the main aim of reducing the data exchange among cavs in the control zone and at the same to minimize the travel time and energy consumption. the safety constraints and the vehicle limitations are considered using the control barrier function ( cbf ) framework and a self - triggered scheme is proposed using the cbf constraints. moreover, modified cbf constraints are developed to ensure a minimum inter - event interval for the proposed self - triggered schemes. finally, it is shown through a simulation study that the number of data exchanges among cavs is significantly reduced using the proposed self - triggered schemes in comparison with the standard time - triggered framework.
arxiv:2203.13147
fetal motion is unpredictable and rapid on the scale of conventional mr scan times. therefore, dynamic fetal mri, which aims at capturing fetal motion and dynamics of fetal function, is limited to fast imaging techniques with compromises in image quality and resolution. super - resolution for dynamic fetal mri is still a challenge, especially when multi - oriented stacks of image slices for oversampling are not available and high temporal resolution for recording the dynamics of the fetus or placenta is desired. further, fetal motion makes it difficult to acquire high - resolution images for supervised learning methods. to address this problem, in this work, we propose stress ( spatio - temporal resolution enhancement with simulated scans ), a self - supervised super - resolution framework for dynamic fetal mri with interleaved slice acquisitions. our proposed method simulates an interleaved slice acquisition along the high - resolution axis on the originally acquired data to generate pairs of low - and high - resolution images. then, it trains a super - resolution network by exploiting both spatial and temporal correlations in the mr time series, which is used to enhance the resolution of the original data. evaluations on both simulated and in utero data show that our proposed method outperforms other self - supervised super - resolution methods and improves image quality, which is beneficial to other downstream tasks and evaluations.
arxiv:2106.12407
we present a statistical analysis of the kepler m dwarf planet hosts, with a particular focus on the fractional number of systems hosting multiple transiting planets. we manufacture synthetic planetary systems within a range of planet multiplicity and mutual inclination for comparison to the kepler yield. we recover the observed number of systems containing between 2 and 5 transiting planets if every m dwarf hosts 6. 1 + / - 1. 9 planets with typical mutual inclinations of 2. 0 + 4. 0 - 2. 0 degrees. this range includes the solar system in its coplanarity and multiplicity. however, similar to studies of kepler exoplanetary systems around more massive stars, we report that the number of singly - transiting planets found by kepler is too high to be consistent with a single population of multi - planet systems : a finding that cannot be attributed to selection biases. to account for the excess singleton planetary systems we adopt a mixture model and find that 55 + 23 - 12 % of planetary systems are either single or contain multiple planets with large mutual inclinations. thus, we find that the so - called " kepler dichotomy " holds for planets orbiting m dwarfs as well as sun - like stars. additionally, we compare stellar properties of the hosts to single and multiple transiting planets. for the brightest subset of stars in our sample we find intriguing, yet marginally significant evidence that stars hosting multiply - transiting systems are rotating more quickly, are closer to the midplane of the milky way, and are comparatively metal poor. this preliminary finding warrants further investigation.
arxiv:1410.4192
we examine the holographic entanglement entropy of spherical regions in de sitter space in the presence of massive flavour fields which are modelled by probe d7 branes in ads _ 5xs ^ 5. we focus on the finite part of the massive correction to the entropy in the limits of small mass and large mass that are separated by a phase transition between two topologically distinct brane embeddings. for small masses, it approaches the flat space result for small spheres, whereas for large spheres there is a term that goes as the log of the sphere radius. for large masses, we find evidence for a universal contribution logarithmic in the mass. in all cases the entanglement entropy is smooth as the sphere radius crosses the horizon.
arxiv:1512.07902
only in 1994 by andrew wiles, who used tools including scheme theory from algebraic geometry, category theory, and homological algebra. another example is goldbach ' s conjecture, which asserts that every even integer greater than 2 is the sum of two prime numbers. stated in 1742 by christian goldbach, it remains unproven despite considerable effort. number theory includes several subareas, including analytic number theory, algebraic number theory, geometry of numbers ( method oriented ), diophantine equations, and transcendence theory ( problem oriented ). = = = geometry = = = geometry is one of the oldest branches of mathematics. it started with empirical recipes concerning shapes, such as lines, angles and circles, which were developed mainly for the needs of surveying and architecture, but has since blossomed out into many other subfields. a fundamental innovation was the ancient greeks ' introduction of the concept of proofs, which require that every assertion must be proved. for example, it is not sufficient to verify by measurement that, say, two lengths are equal ; their equality must be proven via reasoning from previously accepted results ( theorems ) and a few basic statements. the basic statements are not subject to proof because they are self - evident ( postulates ), or are part of the definition of the subject of study ( axioms ). this principle, foundational for all mathematics, was first elaborated for geometry, and was systematized by euclid around 300 bc in his book elements. the resulting euclidean geometry is the study of shapes and their arrangements constructed from lines, planes and circles in the euclidean plane ( plane geometry ) and the three - dimensional euclidean space. euclidean geometry was developed without change of methods or scope until the 17th century, when rene descartes introduced what is now called cartesian coordinates. this constituted a major change of paradigm : instead of defining real numbers as lengths of line segments ( see number line ), it allowed the representation of points using their coordinates, which are numbers. algebra ( and later, calculus ) can thus be used to solve geometrical problems. geometry was split into two new subfields : synthetic geometry, which uses purely geometrical methods, and analytic geometry, which uses coordinates systemically. analytic geometry allows the study of curves unrelated to circles and lines. such curves can be defined as the graph of functions, the study of which led to differential geometry. they can also be defined as implicit equations, often polynomial equations ( which spawned algebraic geometry ). analytic geometry also makes it possible to consider euclidean spaces of higher
https://en.wikipedia.org/wiki/Mathematics
many problems in science and engineering involve, as part of their solution process, the consideration of a separable function which is the sum of two convex functions, one of them possibly non - smooth. recently a few works have discussed inexact versions of several accelerated proximal methods aiming at solving this minimization problem. this paper shows that inexact versions of a method of beck and teboulle ( fista ) preserve, in a hilbert space setting, the same ( non - asymptotic ) rate of convergence under some assumptions on the decay rate of the error terms. the notion of inexactness discussed here seems to be rather simple, but, interestingly, when comparing to related works, closely related decay rates of the errors terms yield closely related convergence rates. the derivation sheds some light on the somewhat mysterious origin of some parameters which appear in various accelerated methods. a consequence of the analysis is that the accelerated method is perturbation resilient, making it suitable, in principle, for the superiorization methodology. by taking this into account, we re - examine the superiorization methodology and significantly extend its scope.
arxiv:1508.05631
inverted - band $ pn $ junctions in two - dimensional materials offer a promising platform for electron optics in condensed matter, as they allow to manipulate and guide electron beams without the need for spatial confinement. in this work, we propose the realization of an aharonov - bohm ( ab ) interferometer using such $ pn $ junctions. we observe ab oscillations in numerically obtained conductance and analytically identify the conditions for their appearance by analyzing the scattering processes at the $ pn $ interface. to support experimental implementation, we also consider junctions with a graded interface, where the potential varies smoothly between the $ p $ - and $ n $ - doped regions. our results reveal an abrupt change in the ab - oscillation frequency, which we attribute to a distinct transition in the hybridization across the interface. we verify that our reported ab oscillations are robust to realistic disorder and temperature decoherence channels. our study paves the way for realizing the aharonov - bohm effect in bulk mesoscopic systems without the need for external spatial confinement, offering new possibilities in electron optics.
arxiv:2410.22298
we improve upon pairwise annotation for active learning in coreference resolution, by asking annotators to identify mention antecedents if a presented mention pair is deemed not coreferent. this simple modification, when combined with a novel mention clustering algorithm for selecting which examples to label, is much more efficient in terms of the performance obtained per annotation budget. in experiments with existing benchmark coreference datasets, we show that the signal from this additional question leads to significant performance gains per human - annotation hour. future work can use our annotation protocol to effectively develop coreference models for new domains. our code is publicly available at https : / / github. com / belindal / discrete - active - learning - coref.
arxiv:2004.13671
we briefly discuss theoretical and experimental discoveries in the field of supertransport and plasticity in imperfect solid \ he4 and argue that these promise new exciting developments. several experiments aimed at clarifying the origin of the supertransport and its relation to plasticity are proposed. in particular, we argue that " cold - working " protocols of sample preparation should be crucial in this respect.
arxiv:1912.03704
we study random variables of the form $ f ( x ) $, when $ f $ is a degree $ d $ polynomial, and $ x $ is a random vector on $ \ mathbb { r } ^ { n } $, motivated towards a deeper understanding of the covariance structure of $ x ^ { \ otimes d } $. for applications, the main interest is to bound $ \ mathrm { var } ( f ( x ) ) $ from below, assuming a suitable normalization on the coefficients of $ f $. our first result applies when $ x $ has independent coordinates, and we establish dimension - free bounds. we also show that the assumption of independence can be relaxed and that our bounds carry over to uniform measures on isotropic $ l _ { p } $ balls. moreover, in the case of the euclidean ball, we provide an orthogonal decomposition of $ \ mathrm { cov } ( x ^ { \ otimes d } ) $. finally, we utilize the connection between anti - concentration and decay of fourier coefficients to prove a high - dimensional analogue of the van der corput lemma, thus partially answering a question posed by carbery and wright.
arxiv:2108.04268
we address the localization of a reconfigurable intelligent surface ( ris ) for a single - input single - output multi - carrier system using bi - static sensing between a fixed transmitter and a fixed receiver. due to the deployment of riss with a large dimension, near - field ( nf ) scenarios are likely to occur, especially for indoor applications, and are the focus of this work. we first derive the cramer - rao bounds ( crbs ) on the estimation error of the ris position and orientation and the time of arrival ( toa ) for the path transmitter - ris - receiver. we propose a multi - stage low - complexity estimator for ris localization purposes. in this proposed estimator, we first perform a line search to estimate the toa. then, we use the far - field approximation of the nf signal model to implicitly estimate the angle of arrival and the angle of departure at the ris center. finally, the ris position and orientation estimate are refined via a quasi - newton method. simulation results reveal that the proposed estimator can attain the crbs. we also investigate the effects of several influential factors on the accuracy of the proposed estimator like the ris size, transmitted power, system bandwidth, and ris position and orientation.
arxiv:2206.13915
this work focuses on minimum - time low - thrust orbit transfers from a prescribed low earth orbit to a specified low lunar orbit. the well - established indirect formulation of minimum - time orbit transfers is extended to a multibody dynamical framework, with initial and final orbits around two distinct primaries. to do this, different representations, useful for describing orbit dynamics, are introduced, i. e., modified equinoctial elements ( mee ) and cartesian coordinates ( cc ). use of two sets of mee, relative to either earth or moon, allows simple writing of the boundary conditions about the two celestial bodies, but requires the formulation of a multiple - arc trajectory optimization problem, including two legs : ( a ) geocentric leg and ( b ) selenocentric leg. in the numerical solution process, the transition between the two mee representations uses cc, which play the role of convenient intermediate, matching variables. the multiple - arc formulation at hand leads to identifying a set of intermediate necessary conditions for optimality, at the transition between the two legs. this research proves that a closed - form solution to these intermediate conditions exists, leveraging implicit costate transformation. as a result, the parameter set for an indirect algorithm retains the reduced size of the typical set associated with a single - arc optimization problem. the indirect heuristic technique, based on the joint use of the necessary conditions and a heuristic algorithm ( i. e., differential evolution in this study ) is proposed as the numerical solution method, together with the definition of a layered fitness function, aimed at facilitating convergence. the minimum - time trajectory of interest is sought in a high - fidelity dynamical framework, with the use of planetary ephemeris and the inclusion of the simultaneous gravitational action of sun, earth, and moon, along the entire transfer path.
arxiv:2406.00336
strong second - harmonic generation has recently been experimentally observed from metamaterials consisting of periodic arrays of metal split ring resonators with an effective negative magnetic permeability [ science, 313, 502 ( 2006 ) ]. to explore the underlying physical mechanism, a classical model derived from microscopic theory is employed here. the quasi - free electrons inside the metal are approximated as a classical coulomb - interacting electron gas, and their motion under the excitation of an external electromagnetic field is described by the cold - plasma wave equations. through numerical simulations, it is demonstrated that the microscopic theory includes the dominant physical mechanisms bothqualitatively and quantitatively.
arxiv:0807.3531
reconfigurable intelligent surface ( ris ) can provide stable connectivity for vehicular communications when direct transmission becomes significantly weaker with dynamic channel conditions between an access point and a moving vehicle. in this paper, we analyze the performance of a ris - assisted vehicular network by coherently combining received signals reflected by ris elements and direct transmissions from the source terminal over double generalized gamma ( dgg ) fading channels. we present analytical expressions on the outage probability and average bit - error rate ( ber ) performance of the considered system by deriving exact density and distribution functions for the end - to - end signal - to - noise ratio ( snr ) resulted from the finite sum of the direct link and product of channel coefficients each distributed according to the dgg. we also develop asymptotic analysis on the outage probability and average ber to derive diversity order for a better insight into the system performance at high snr. we validate the derived analytical expressions through numerical and simulation results and demonstrate scaling of the system performance with ris elements and a comparison to the conventional relaying techniques and direct transmissions considering various practically relevant scenarios.
arxiv:2204.09958
we consider the effect on the length of the game of cops and robbers when more cops are added to the game play. in overprescribed cops and robbers, as more cops are added, the capture time ( the minimum length of the game assuming optimal play ) monotonically decreases. we give the full range of capture times for any number of cops on trees, and classify the capture time for an asymptotic number of cops on grids, hypercubes, and binomial random graphs. the capture time of planar graphs with a number of cops at and far above the cop number is considered.
arxiv:1611.07592
in this work, an intelligent controller is employed to the chaos control problem in a nonlinear pendulum. the adopted approach is based on the sliding mode control strategy and enhanced by an adaptive fuzzy algorithm to cope with modeling inaccuracies. the convergence properties of the closed - loop system are analytically proven using lyapunov ' s direct method and barbalat ' s lemma. numerical results are also presented in order to demonstrate the control system performance.
arxiv:2206.01617
sexually reproducing populations with small number of individuals may go extinct by stochastic fluctuations in sex determination, causing all their members to become male or female in a generation. in this work we calculate the time to extinction of isolated populations with fixed number $ n $ of individuals that are updated according to the moran birth and death process. at each time step, one individual is randomly selected and replaced by its offspring resulting from mating with another individual of opposite sex ; the offspring can be male or female with equal probability. a set of $ n $ time steps is called a generation, the average time it takes for the entire population to be replaced. the number k of females fluctuates in time, similarly to a random walk, and extinction, which is the only asymptotic possibility, occurs when k = 0 or k = n. we show that it takes only one generation for an arbitrary initial distribution of males and females to approach the binomial distribution. this distribution, however, is unstable and the population eventually goes extinct in 2 ^ n / n generations. we also discuss the robustness of these results against bias in the determination of the sex of the offspring, a characteristic promoted by infection by the bacteria wolbachia in some arthropod species or by temperature in reptiles.
arxiv:1204.4920
the light detection and ranging ( lidar ) sensor has become one of the most important perceptual devices due to its important role in simultaneous localization and mapping ( slam ). existing slam methods are mainly developed for mechanical lidar sensors, which are often adopted by large scale robots. recently, the solid - state lidar is introduced and becomes popular since it provides a cost - effective and lightweight solution for small scale robots. compared to mechanical lidar, solid - state lidar sensors have higher update frequency and angular resolution, but also have smaller field of view ( fov ), which is very challenging for existing lidar slam algorithms. therefore, it is necessary to have a more robust and computationally efficient slam method for this new sensing device. to this end, we propose a new slam framework for solid - state lidar sensors, which involves feature extraction, odometry estimation, and probability map building. the proposed method is evaluated on a warehouse robot and a hand - held device. in the experiments, we demonstrate both the accuracy and efficiency of our method using an intel l515 solid - state lidar. the results show that our method is able to provide precise localization and high quality mapping. we made the source codes public at \ url { https : / / github. com / wh200720041 / ssl _ slam }.
arxiv:2102.03800
we present the synchronized unsteady wall pressure measurements performed at the circumference of a full scale 35 m circular chimney submitted to natural wind. the atmospheric turbulent boundary layer generates a turbulence intensity of 15 % at the altitude of the measurements and the corresponding reynolds number is 1. 13 106. for the first time, the steady and unsteady pressure distributions around the circumference are presented, despite large difficulties in the measuring process. the analysis of the pressure distribution using the bi - orthogonal decomposition ( bod ) is a key factor in the success of the processing. by comparison with wind tunnel similar measurements, with 2d cylinders, the time - averaged pressure distribution is found between the one of a subcritical regime and a supercritical regime, slightly closer to the subcritical regime notably because the base pressure coefficients are similar. the atmospheric turbulence is an essential ingredient for the unsteady pressure response on the chimney, which generates high levels of rms pressure, much higher than all those measured in wind tunnel, even under the turbulent flow generated by a grid. the analysis by bod allowed the extraction of a term which is mainly generated by alternate vortex shedding. despite a very noisy signal, the strouhal number is determined to be 0. 20 - 0. 24. the corresponding shape of the pressure distribution is compared with those found in wind tunnel : it is shown that the full scale field measurements are close, but not identical, to the small scale measurements in wind tunnel on a rough cylinder submitted to a grid generated turbulent flow.
arxiv:2311.11688
objective : the brain operates via generation, transmission and integration of neuronal signals and most neurological disorders are related to perturbation of these processes. neurostimulation by focused ultrasound ( fus ) is a promising technology with potential to rival other clinically - used techniques for the investigation of brain function and treatment of numerous neurological diseases. the purpose of this study was to characterize spatial and temporal aspects of causal electrophysiological signals directly stimulated by short, single pulses of focused ultrasound ( fus ) on ex vivo mouse hippocampal brain slices. approach : microelectrode arrays ( mea ) are used to study the spatio - temporal dynamics of extracellular neuronal activities both at the single neuron and neural networks scales. hence, meas provide an excellent platform for characterization of electrical activity generated, modulated and transmitted in response to fus exposure. in this study, a novel mixed fus / mea platform was designed for the spatio - temporal description of the causal responses generated by single 1. 78 mhz fus pulses in ex vivo mouse hippocampal brain slices. main results : our results show that fus pulses can generate local field potentials ( lfps ), sustained by synchronized neuronal post - synaptic potentials, and reproducing network activities. lfps induced by fus stimulation were found to be repeatable to consecutive fus pulses though exhibiting a wide range of amplitudes ( 50 - 600 $ \ mu $ v ), durations ( 20 - 200 ms ), and response delays ( 10 - 60 ms ). moreover, lfps were spread across the hippocampal slice following single fus pulses thus demonstrating that fus may be capable of stimulating different neural structures within the hippocampus. significance : current knowledge on neurostimulation by ultrasound describes neuronal activity generated by trains of repetitive ultrasound pulses. this novel study details the causal neural responses produced by single - pulse fus neurostimulation while illustrating the distribution and propagation properties of this neural activity along major neural pathways of the hippocampus.
arxiv:2101.06935
a quaternary compound bi3o2s2cl, which consists of novel [ bis2cl ] 2 - layers, is reported. it adopts a layered structure of the space group i4 / mmm ( no. 139 ) with lattice parameters : a = 3. 927 ( 1 ) { \ aa }, c = 21. 720 ( 5 ) { \ aa }. in this compound, bismuth and chlorine atoms form an infinite planar layer, which is unique among the bismuth halides. superconductivity is observed in both polycrystals and single crystals, and is significantly enhanced in the samples prepared with less sulfur or at higher temperatures. by tuning the content of sulfur, bi3o2s2cl can be converted from a semiconductor into a superconductor. the superconducting critical temperature ranges from 2. 6 k to 3. 5 k. our discovery of the [ bis2cl ] 2 - layer opens another door in searching for the bismuth compounds with novel physical properties.
arxiv:1903.02698
we study quasimorphisms and bounded cohomology of a variety of braided versions of thompson groups. our first main result is that the brin - - dehornoy braided thompson group $ bv $ has an infinite - dimensional space of quasimorphisms and thus infinite - dimensional second bounded cohomology. this implies that despite being perfect, $ bv $ is not uniformly perfect, in contrast to thompson ' s group $ v $. we also prove that relatives of $ bv $ like the ribbon braided thompson group $ rv $ and the pure braided thompson group $ bf $ similarly have an infinite - dimensional space of quasimorphisms. our second main result is that, in stark contrast, the close relative of $ bv $ denoted $ \ hat { bv } $, which was introduced concurrently by brin, has trivial second bounded cohomology. this makes $ \ hat { bv } $ the first example of a left - orderable group of type $ \ operatorname { f } _ \ infty $ that is not locally indicable and has trivial second bounded cohomology. this also makes $ \ hat { bv } $ an interesting example of a subgroup of the mapping class group of the plane minus a cantor set that is non - amenable but has trivial second bounded cohomology, behaviour that cannot happen for finite - type mapping class groups.
arxiv:2204.05272
the longest increasing subsequence problem for permutations has been studied extensively in the last fifty years. the interpretation of the longest increasing subsequence as the longest 21 - avoiding subsequence in the context of permutation patterns leads to many interesting research directions. we introduce and study the statistical properties of hammersleytype interacting particle processes related to these generalizations and explore the finer structures of their distributions. we also propose three different interacting particle systems in the plane analogous to the hammersley process in one dimension and obtain estimates for the asymptotic orders of the mean and variance of the number of particles in the systems.
arxiv:2106.11186
observations in the solar wind suggest that the compressive component of inertial - range solar - wind turbulence is dominated by slow modes. the low collisionality of the solar wind allows for non - thermal features to survive, which suggests the requirement of a kinetic plasma description. the least - damped kinetic slow mode is associated with the ion - acoustic ( ia ) wave and a non - propagating ( np ) mode. we derive analytical expressions for the ia - wave dispersion relation in an anisotropic plasma in the framework of gyrokinetics and then compare them to fully - kinetic numerical calculations, results from two - fluid theory, and mhd. this comparison shows major discrepancies in the predicted wave phase speeds from mhd and kinetic theory at moderate to high $ \ beta $. mhd and kinetic theory also dictate that all plasma normal modes exhibit a unique signature in terms of their polarization. we quantify the relative amplitude of fluctuations in the three lowest particle velocity moments associated with ia and np modes in the gyrokinetic limit and compare these predictions with mhd results and in - situ observations of the solar - wind turbulence. the agreement between the observations of the wave polarization and our mhd predictions is better than the kinetic predictions, suggesting that the plasma behaves more like a fluid in the solar wind than expected.
arxiv:1703.03040
the self - energy - functional approach proposed recently is applied to the single - band hubbard model at half - filling to study the mott - hubbard metal - insulator transition within the most simple but non - trivial approximation. this leads to a mean - field approach which is interesting conceptually : trial self - energies from a two - site single - impurity anderson model are used to evaluate an exact and general variational principle. while this restriction of the domain of the functional represents a strong approximation, the approach is still thermodynamically consistent by construction and represents a conceptual improvement of the ` ` linearized dmft ' ' which has been suggested previously as a handy approach to study the critical regime close to the transition. it turns out that the two - site approximation is able to reproduce the complete ( zero and finite - temperature ) phase diagram for the mott transition. for the critical point at t = 0, the entire calculation can be done analytically. this calculation elucidates different general aspects of the self - energy - functional theory. furthermore, it is shown how to deal with a number of technical difficulties which appear when the self - energy functional is evaluated in practice.
arxiv:cond-mat/0306278
we discuss an effective theory for qcd at finite chemical potential and non - zero temperature, where qcd is reduced to its center degrees of freedom. the effective action can be mapped to a flux representation, where the complex phase problem is solved and the theory accessible to monte carlo techniques. in this work, we use a generalized prokof ' ev - svistunov worm algorithm to perform the simulations and determine the phase diagram as a function of temperature, quark mass and chemical potential. it turns out that the transition is qualitatively as expected for qcd.
arxiv:1110.6862
we model time series of vix ( monthly average ) and monthly stock index returns. we use log - heston model : logarithm of vix is modeled as an autoregression of order 1. our main insight is that normalizing monthly stock index returns ( dividing them by vix ) makes them much closer to independent identically distributed gaussian. the resulting model is mean - reverting, and the innovations are non - gaussian. the combined stochastic volatility model fits well, and captures pareto - like tails of real - world stock market returns. this works for small and large stock indices, for both price and total returns.
arxiv:2410.22471
layered van der waals materials have risen as powerful platforms to artificially engineer correlated states of matter. here we show the emergence of a multiferroic order in a twisted dichalcogenide bilayer superlattice at quarter - filling. we show that the competition between coulomb interactions leads to the simultaneous emergence of ferrimagnetic and ferroelectric orders. we derive the magnetoelectric coupling for this system, which leads to a direct strong coupling between the charge and spin orders. we show that, due to intrinsic spin - orbit coupling effects, the electronic structure shows a non - zero chern number, thus displaying a topological multiferroic order. we show that this topological state gives rise to interface modes at the different magnetic and ferroelectric domains of the multiferroic. we demonstrate that these topological modes can be tuned with external electric fields as well as triggered by supermoire effects generated by a substrate. our results put forward twisted van der waals materials as a potential platform to explore multiferroic symmetry breaking orders and, ultimately, controllable topological excitations in magnetoelectric domains.
arxiv:2204.03360
this paper provides an overview of the electric vehicle transition in the uk. the spatial disparity in the uptake of bevs across the different regions is analysed using historic bev sales. a forecast for future growth in bevs ( ignoring the impact of covid - 19 ) is performed using an s - curve model. currently, south east england and greater london have the highest bev sales as a percentage of new vehicle sales. the spatial distribution of ev chargers across the different regions is also analysed. the spatial analysis clearly shows the regional disparity in the uptake of ev. south east england has the highest number of public chargers excluding greater london. however, if we consider the number of evs in that region, it has the second - lowest ratio of approx. 1 charger per 10 bev. the lowest ratio being 0. 8 in the west midlands.
arxiv:2007.03745
photon - photon interactions are an essential requirement of quantum photonic information processing. one way to generate these interactions is to utilize an atom strongly coupled to an optical cavity. this system exhibits the photon blockade effect which enables single photon switching and creation of non - classical light. but the nonlinear effects enabled by this system suffer from a fundamental time - bandwidth constraint. for the the simple case of splitting an input pulse of two indistinguishable photons, this constraint imposes a limit on the efficiency of routing photons to different output ports. we show that this limit can be exceeded by combining the strongly - coupled atom with linear optics. by optimizing the unitary of the linear optical transformation, we achieve improved splitting efficiency for both un - entangled and entangled photons. our results suggest that it may be possible to improve the efficiency of nonlinear optical processes at the single photon level by making suitable use of linear optics. these results could have implications for quantum information processing with photons.
arxiv:2201.04555
quantum optimal control for gate optimization aims to provide accurate, robust, and fast pulse sequences to achieve gate fidelities on quantum systems below the error correction threshold. many methods have been developed and successfully applied in simulation and on quantum hardware. in this paper, we establish a connection between the iterative linear quadratic regulator and quantum optimal control by adapting it to gate optimization of quantum systems. we include constraints on the controls and their derivatives to enable smoother pulses. we achieve high - fidelity simulation results for x and cross - resonance gates on one - and two - qubit fixed - frequency transmons simulated with two and three levels.
arxiv:2504.10938
we have studied the anomalous hall effect ( ahe ) in strained thin films of the frustrated antiferromagnet mn $ _ { 3 } $ nin. the ahe does not follow the conventional relationships with magnetization or longitudinal conductivity and is enhanced relative to that expected from the magnetization in the antiferromagnetic state below $ t _ { \ mathrm { n } } = 260 $ \, k. this enhancement is consistent with origins from the non - collinear antiferromagnetic structure, as the latter is closely related to that found in mn $ _ { 3 } $ ir and mn $ _ { 3 } $ pt where a large ahe is induced by the berry curvature. as the berry phase induced ahe should scale with spin - orbit coupling, yet larger ahe may be found in other members of the chemically flexible mn $ _ { 3 } a $ n structure.
arxiv:1902.04357
markov chain sampling methods form the backbone of modern computational statistics. however, many popular methods are prone to random walk behavior, i. e., diffusion - like exploration of the sample space, leading to slow mixing that requires intricate tuning to alleviate. non - reversible samplers can resolve some of these issues. we introduce a device that turns jump processes that satisfy a skew - detailed balance condition for a reference measure into a process that samples a target measure that is absolutely continuous with respect to the reference measure. the resulting sampler is rejection - free, non - reversible, and continuous - time. as an example, we apply the device to hamiltonian dynamics discretized by the leapfrog integrator, resulting in a rejection - free non - reversible continuous - time version of hamiltonian monte carlo ( hmc ). we prove the geometric ergodicity of the resulting sampler under certain convexity conditions, and demonstrate its qualitatively different behavior to hmc through numerical examples.
arxiv:2504.12190
computational social science research has made advances in machine learning and natural language processing that support content moderators in detecting harmful content. these advances often rely on training datasets annotated by crowdworkers for harmful content. in designing instructions for annotation tasks to generate training data for these algorithms, researchers often treat the harm concepts that we train algorithms to detect - ' hateful ', ' offensive ', ' toxic ', ' racist ', ' sexist ', etc. - as interchangeable. in this work, we studied whether the way that researchers define ' harm ' affects annotation outcomes. using venn diagrams, information gain comparisons, and content analyses, we reveal that annotators do not use the concepts ' hateful ', ' offensive ', and ' toxic ' interchangeably. we identify that features of harm definitions and annotators ' individual characteristics explain much of how annotators use these terms differently. our results offer empirical evidence discouraging the common practice of using harm concepts interchangeably in content moderation research. instead, researchers should make specific choices about which harm concepts to analyze based on their research goals. recognizing that researchers are often resource constrained, we also encourage researchers to provide information to bound their findings when their concepts of interest differ from concepts that off - the - shelf harmful content detection algorithms identify. finally, we encourage algorithm providers to ensure their instruments can adapt to contextually - specific content detection goals ( e. g., soliciting instrument users ' feedback ).
arxiv:2309.15827
we present the detection of a rare case of dramatic strengthening in the uv absorption profiles in the spectrum of the quasar j115122. 14 + 020426. 3 between observations ~ 2. 86 years apart in the quasar rest - frame. a 2001 spectrum from the sloan digital sky survey ( sdss ) shows a civ " mini - broad " absorption line ( fwhm = 1, 220 km / s ) with a maximum blueshift velocity ~ 9, 520 km / s, while a later spectrum from the very large telescope ( vlt ) shows significantly broader and stronger absorption line, with a maximum blueshift velocity of ~ 12, 240 km / s, that qualifies as a broad absorption line. a similar variability pattern is observed in two additional systems at lower blueshifted velocities and in the lya and nv transitions as well. one of the absorption systems appears to be resolved and shows evidence for partial covering of the quasar continuum source ( cf ~ 0. 65 ), indicating a transverse absorber size of, at least, ~ 6 x 10 ^ ( 16 ) cm. in contrast, a cluster of narrower civ lines appears to originate in gas that fully covers the continuum and broad emission line sources. there is no evidence for changes in the centroid velocity of the absorption troughs. this case suggests that, at least some of the absorbers that produce " mini - broad " and broad absorption lines in quasar spectra do not belong to intrinsically separate classes. here, the " mini - broad " absorption line is most likely interpreted as an intermediate phase before the appearance of a broad absorption line due to their similar velocity. while the current observations do not provide enough constraints to discern among the possible causes for this variability, future monitoring of multiple transitions at high resolution will help achieve this goal.
arxiv:1307.6266
we present a simultaneous measurement of the b0bar lifetime tau ( b0 ) and mixing parameter $ delta m _ d $. we use a sample of about 50000 b0bar - > d * + l - anti - nu ( l ) partially reconstructed decays identified with the babar detector at the pep - ii storage ring at slac, where the flavor of the other b meson is determined from the charge of another high momentum lepton in the same event. the preliminary results are : tau ( b0 ) = ( 1. 501 + / - 0. 008 ( stat. ) + / - 0. 030 ( syst. ) ) ps, $ delta m _ d $ = ( 0. 523 + / - 0. 004 ( stat. ) + / - 0. 007 ( syst. ) ) ps ^ { - 1 }.
arxiv:hep-ex/0408039
we have performed simulations of cluster formation along two regions of a spiral arm taken from a global milky way simulation, including photoionising feedback. one region is characterised by strongly converging flows, the other represents a more typical spiral arm region. we find that more massive clusters are able to form on shorter timescales for the region with strongly converging flows. mergers between clusters are frequent in the case of the strongly converging flows and enable the formation of massive clusters. we compare equivalent clusters formed in simulations with and without ionisation. photoionisation does not prevent massive cluster formation, but can be seen to limit the masses of the clusters. on average the mass is reduced by around 20 %, but we see a large spread from ionisation having minimal difference to leading to a 50 % reduction in mass. photoionisation is also able to clear out the gas in the vicinity of the clusters on myr timescales, which can produce clusters with larger radii that are surrounded by more massive stellar halos. we find that the ionising feedback has more impact in our second region which is less dense and has less strongly converging flows.
arxiv:2110.09201
we examine a recent prediction for the chirality - dependence of the casimir force in chiral metamaterials by numerical computation of the forces between the exact microstructures, rather than homogeneous approximations. we compute the exact force for a chiral bent - cross pattern, as well as forces for an idealized " omega " - particle medium in the dilute approximation and identify the effects of structural inhomogeneity ( i. e. proximity forces and anisotropy ). we find that these microstructure effects dominate the force for separations where chirality was predicted to have a strong influence. to get observations of chirality free from microstructure effects, one must go to large separations where the effect of chirality is at most $ \ sim10 ^ { - 4 } $ of the total force.
arxiv:1006.5489
quantum and classical systems evolving under the same formal hamiltonian $ h $ may exhibit dramatically different behavior after the ehrenfest timescale $ t _ e \ sim \ log ( \ hbar ^ { - 1 } ) $, even as $ \ hbar \ to 0 $. coupling the system to a markovian environment results in a lindblad equation for the quantum evolution. its classical counterpart is given by the fokker - planck equation on phase space, which describes hamiltonian flow with friction and diffusive noise. the quantum and classical evolutions may be compared via the wigner - weyl representation. due to decoherence, they are conjectured to match closely for times far beyond the ehrenfest timescale as $ \ hbar \ to 0 $. we prove a version of this correspondence, bounding the error between the quantum and classical evolutions for any sufficiently regular hamiltonian $ h ( x, p ) $ and lindblad functions $ l _ k ( x, p ) $. the error is small when the strength of the diffusion $ d $ associated to the lindblad functions satisfies $ d \ gg \ hbar ^ { 4 / 3 } $, in particular allowing vanishing noise in the classical limit. we use a time - dependent semiclassical mixture of variably squeezed gaussian states evolving by a local harmonic approximation to the lindblad dynamics. both the exact quantum trajectory and its classical counterpart can be expressed as perturbations of this semiclassical mixture, with the errors bounded using duhamel ' s principle. we present heuristic arguments suggesting the $ 4 / 3 $ exponent is optimal and defines a boundary in the sense that asymptotically weaker diffusion permits a breakdown of quantum - classical correspondence at the ehrenfest timescale. our presentation aims to be comprehensive and accessible to both mathematicians and physicists. in a shorter companion paper, we treat the special case of hamiltonians of the form $ h = p ^ 2 / ( 2m ) + v ( x ) $ and linear lindblad operators, with explicit bounds that can be applied directly to physical systems.
arxiv:2307.05326
the ability to predict the evolution of a pathogen would significantly improve the ability to control, prevent, and treat disease. despite significant progress in other problem spaces, deep learning has yet to contribute to the issue of predicting mutations of evolving populations. to address this gap, we developed a novel machine learning framework using generative adversarial networks ( gans ) with recurrent neural networks ( rnns ) to accurately predict genetic mutations and evolution of future biological populations. using a generalized time - reversible phylogenetic model of protein evolution with bootstrapped maximum likelihood tree estimation, we trained a sequence - to - sequence generator within an adversarial framework, named mutagan, to generate complete protein sequences augmented with possible mutations of future virus populations. influenza virus sequences were identified as an ideal test case for this deep learning framework because it is a significant human pathogen with new strains emerging annually and global surveillance efforts have generated a large amount of publicly available data from the national center for biotechnology information ' s ( ncbi ) influenza virus resource ( ivr ). mutagan generated " child " sequences from a given " parent " protein sequence with a median levenshtein distance of 2. 00 amino acids. additionally, the generator was able to augment the majority of parent proteins with at least one mutation identified within the global influenza virus population. these results demonstrate the power of the mutagan framework to aid in pathogen forecasting with implications for broad utility in evolutionary prediction for any protein population.
arxiv:2008.11790
the left - right twin higgs ( lrth ) model predicts the existence of the charged higgs $ \ phi ^ { \ pm } $. in this paper, we study the production of the charged higgs boson $ \ phi ^ { - } $ with single top quark via the process $ bg \ to t \ phi ^ { - } $ at the $ cern $ large hadron collider ( lhc ). the numerical results show that the production cross section can reach the level of $ 10 pb $ in the reasonable parameter space of the lrth model. we expect that, as long as it is not too heavy, the possible signatures of the heavy charged higgs boson $ \ phi ^ { - } $ might be detected via the decay mode $ \ phi ^ { - } \ to \ bar { t } b $ at the lhc experiments.
arxiv:0704.0840
with a mere usage of well - established properties of para - differential operators, the conjugacy equations in several model kam problems are converted to para - homological equations solvable by standard fixed point argument. such discovery greatly simplifies kam proofs, renders the traditional kam iteration steps unnecessary, and may suggest a systematic scheme of finding quasi - periodic solutions of realistic magnitude.
arxiv:2312.13971
in 2014 the patient protection and affordable care act ( aca ) introduced the expansion of medicaid where states can opt to expand the eligibility for those in need of free health insurance. in this paper, we attempt to assess the effectiveness of medicaid expansion on health outcomes of state populations using difference - in - difference ( dd ) regressions to seek for causal impacts of expanding medicaid on health outcomes in 49 states. we find that in the time frame of 2013 to 2016, medicaid expansion seems to have had no significant impact on the health outcomes of states that have chosen to expand.
arxiv:2012.11286
random program generators often exhibit opportunism : they generate programs without a specific focus within the vast search space defined by the programming language. this opportunistic behavior hinders the effective generation of programs that trigger bugs in compilers and analyzers, even when such programs closely resemble those generated. to address this limitation, we propose bounded exhaustive random program generation, a novel method that focuses the search space of program generation with the aim of more quickly identifying bug - triggering programs. our approach comprises two stages : 1 ) generating random program templates, which are incomplete test programs containing bug - related placeholders, and 2 ) conducting a bounded exhaustive enumeration of valid values for each placeholder within these templates. to ensure efficiency, we maintain a solvable constraint set during the template generation phase and then methodically explore all possible values of placeholders within these constraints during the exhaustive enumeration phase. we have implemented this approach for solidity, a popular smart contract language for the ethereum blockchain, in a tool named erwin. based on a recent study of solidity compiler bugs, the placeholders used by erwin relate to language features commonly associated with compiler bugs. erwin has successfully identified 23 previously unknown bugs across two solidity compilers, solc and solang, and one solidity static analyzer, slither. evaluation results demonstrate that erwin outperforms state - of - the - art solidity fuzzers in bug detection and complements developer - written test suites by covering 4, 582 edges and 14, 737 lines of the solc compiler that were missed by solc unit tests.
arxiv:2503.20332
we propose an energy amplification technique to address the issue that existing models easily overlook low - energy components in time series forecasting. this technique comprises an energy amplification block and an energy restoration block. the energy amplification block enhances the energy of low - energy components to improve the model ' s learning efficiency for these components, while the energy restoration block returns the energy to its original level. moreover, considering that the energy - amplified data typically displays two distinct energy peaks in the frequency spectrum, we integrate the energy amplification technique with a seasonal - trend forecaster to model the temporal relationships of these two peaks independently, serving as the backbone for our proposed model, amplifier. additionally, we propose a semi - channel interaction temporal relationship enhancement block for amplifier, which enhances the model ' s ability to capture temporal relationships from the perspective of the commonality and specificity of each channel in the data. extensive experiments on eight time series forecasting benchmarks consistently demonstrate our model ' s superiority in both effectiveness and efficiency compared to state - of - the - art methods.
arxiv:2501.17216
in classic program synthesis algorithms, such as counterexample - guided inductive synthesis ( cegis ), the algorithms alternate between a synthesis phase and an oracle ( verification ) phase. many synthesis algorithms use a white - box oracle based on satisfiability modulo theory ( smt ) solvers to provide counterexamples. but what if a white - box oracle is either not available or not easy to work with? we present a framework for solving a general class of oracle - guided synthesis problems which we term synthesis modulo oracles. in this setting, oracles may be black boxes with a query - response interface defined by the synthesis problem. as a necessary component of this framework, we also formalize the problem of satisfiability modulo theories and oracles, and present an algorithm for solving this problem. we implement a prototype solver for satisfiability and synthesis modulo oracles and demonstrate that, by using oracles that execute functions not easily modeled in smt - constraints, such as recursive functions or oracles that incorporate compilation and execution of code, smto and symo are able to solve problems beyond the abilities of standard smt and synthesis solvers.
arxiv:2107.13477
steganography and steganalysis are two interrelated aspects of the field of information security. steganography seeks to conceal communications, whereas steganalysis is aimed to either find them or even, if possible, recover the data they contain. steganography and steganalysis have attracted a great deal of interest, particularly from law enforcement. steganography is often used by cybercriminals and even terrorists to avoid being captured while in possession of incriminating evidence, even encrypted, since cryptography is prohibited or restricted in many countries. therefore, knowledge of cutting - edge techniques to uncover concealed information is crucial in exposing illegal acts. over the last few years, a number of strong and reliable steganography and steganalysis techniques have been introduced in the literature. this review paper provides a comprehensive overview of deep learning - based steganalysis techniques used to detect hidden information within digital media. the paper covers all types of cover in steganalysis, including image, audio, and video, and discusses the most commonly used deep learning techniques. in addition, the paper explores the use of more advanced deep learning techniques, such as deep transfer learning ( dtl ) and deep reinforcement learning ( drl ), to enhance the performance of steganalysis systems. the paper provides a systematic review of recent research in the field, including data sets and evaluation metrics used in recent studies. it also presents a detailed analysis of dtl - based steganalysis approaches and their performance on different data sets. the review concludes with a discussion on the current state of deep learning - based steganalysis, challenges, and future research directions.
arxiv:2308.04522
the secular evolution of the orbital angular momentum ( oam ), the systemic mass $ ( m = m _ { 1 } + m _ { 2 } ) $ and the orbital period of 114 chromospherically active binaries ( cabs ) were investigated after determining the kinematical ages of the sub - samples which were set according to oam bins. oams, systemic masses and orbital periods were shown to be decreasing by the kinematical ages. the first order decreasing rates of oam, systemic mass and orbital period have been determined as $ \ dot j = 3. 48 \ times 10 ^ { - 10 } yr ^ { - 1 } $ per systemic oam, $ \ dot m = 1. 30 \ times 10 ^ { - 10 } yr ^ { - 1 } $ per systemic mass and $ \ dot p = 3. 96 \ times 10 ^ { - 10 } yr ^ { - 1 } $ per orbital period respectively from the kinematical ages. the ratio of $ d \ log j / d \ log m = 2. 68 $, which were derived from the kinematics of the present sample, implies that there must be a mechanism which amplifies the angular momentum loss $ \ bar a = 2. 68 $ times in comparison to isotropic angular momentum loss of hypothetical isotropic wind from the components. it has been shown that simple isotropic mass loss from the surface of a component or both components would increase the orbital period.
arxiv:astro-ph/0512021
consider the equation of the linear oscillator $ u " + u = h ( \ theta ) $, where the forcing term $ h : \ mathbb r \ to \ mathbb r $ is $ 2 \ pi $ - periodic and positive. we show that the existence of a periodic solution implies the existence of a positive solution. to this aim we establish connections between this problem and some separation questions of convex analysis.
arxiv:2201.09272
among the distinguishing characteristics of the remarkable hot r coronae borealis star dy cen, which was recently found to be a spectroscopic binary, is the presence of nebular forbidden lines in its optical spectrum. a compilation of photometry from 1970 to the present suggests that the star has evolved to higher effective temperatures. comparison of spectra from 2010 with earlier spectra show that between 2003 and 2010, the 6717 and 6730 a emission lines of [ s ii ] underwent a dramatic change in their fluxes suggesting an increase in the nebula ' s electron density of 290 cm - 3 to 3140 cm - 3 from 1989 to 2010 while the stellar temperature increased from 19500 k to 25000 k. the nebular radius is about 0. 02 pc, 60000 times bigger than the semimajor axis of dy cen binary system. rapid changes of stellar temperature and its response by the nebula demonstrate stellar evolution in action.
arxiv:1301.5773
passive red galaxies frequently contain warm ionized gas and have spectra similar to low - ionization nuclear emission - line regions ( liners ). here we investigate the nature of the ionizing sources powering this emission, by comparing nuclear spectroscopy from the palomar survey with larger aperture data from the sloan digital sky survey. we find the line emission in the majority of passive red galaxies is spatially extended ; the halpha surface brightness profile depends on radius ( r ) as r ^ ( - 1. 28 ). we detect strong line ratio gradients with radius in [ n ii ] / ha, [ s ii ] / ha, and [ o iii ] / [ s ii ], requiring the ionization parameter to increase outwards. combined with a realistic gas density profile, this outward increasing ionization parameter convincingly rules out agn as the dominant ionizing source, and strongly favors distributed ionizing sources. sources that follow the stellar density profile can additionally reproduce the observed luminosity - dependence of the line ratio gradient. post - agb stars provide a natural ionization source candidate, though they have an ionization parameter deficit. velocity width differences among different emission lines disfavor shocks as the dominant ionization mechanism, and suggest that the interstellar medium in these galaxies contains multiple components. we conclude that the line emission in most liner - like galaxies found in large aperture ( > 100pc ) spectroscopy is not primarily powered by agn activity and thus does not trace the agn bolometric luminosity. however, they can be used to trace warm gas in these red galaxies.
arxiv:1109.1280
we develop a theoretical framework that unifies concepts of multiple time dimensions, quantum shortcut dynamics, and complex topological structures ( ' supermazes ' ) to explore novel phenomena in quantum and classical systems. in particular, we introduce a temporal tensor formalism to describe multidimensional time, define quantum shortcut operators that enact near - instantaneous state transitions, and incorporate these into a supermaze topological model inspired by labyrinthine geometry and network complexity. we show how this framework can give rise to surprising effects such as anomalous thermodynamic relaxation ( analogous to the mpemba effect ) in quantum systems. theoretical implications for quantum computing ( including quantum cloud networks ) are discussed, and connections are drawn to established mathematical paradoxes and physical principles.
arxiv:2504.07900
we present a new method of self - supervised learning and knowledge distillation based on the multi - views and multi - representations ( mv - mr ). the mv - mr is based on the maximization of dependence between learnable embeddings from augmented and non - augmented views, jointly with the maximization of dependence between learnable embeddings from augmented view and multiple non - learnable representations from non - augmented view. we show that the proposed method can be used for efficient self - supervised classification and model - agnostic knowledge distillation. unlike other self - supervised techniques, our approach does not use any contrastive learning, clustering, or stop gradients. mv - mr is a generic framework allowing the incorporation of constraints on the learnable embeddings via the usage of image multi - representations as regularizers. along this line, knowledge distillation is considered a particular case of such a regularization. mv - mr provides the state - of - the - art performance on the stl10 and imagenet - 1k datasets among non - contrastive and clustering - free methods. we show that a lower complexity resnet50 model pretrained using proposed knowledge distillation based on the clip vit model achieves state - of - the - art performance on stl10 linear evaluation. the code is available at : https : / / github. com / vkinakh / mv - mr
arxiv:2303.12130
we aim to obtain accurate rate coefficients for the collisional excitation of ch + by he for high gas temperatures. the ab initio coupled - cluster [ ccsd ( t ) ] approximation was used to compute the interaction potential energy. cross sections are then derived in the close coupling ( cc ) approach and rate coefficients inferred by averaging these cross sections over a maxwell - boltzmann distribution of kinetic energies. cross sections are calculated up to 10 ' 000 cm ^ - 1 for j ranging from 0 to 10. rate coefficients are obtained at high temperatures up to 2000 k.
arxiv:0909.2010
in the framework of carrol - field - jackiw electrodynamics we calculate the spectral distribution of the cherenkov radiation ( chr ) produced by a charge moving at constant velocity in a chiral medium. we find zero, one or two cherenkov angles according to the relation between the velocity of the particle and the refraction index of the medium.
arxiv:2207.01104
a threshold result was proved in this paper for semilinear parabolic system with pure power type nonlinearities
arxiv:1009.3733
this paper tackles the purely unsupervised person re - identification ( re - id ) problem that requires no annotations. some previous methods adopt clustering techniques to generate pseudo labels and use the produced labels to train re - id models progressively. these methods are relatively simple but effective. however, most clustering - based methods take each cluster as a pseudo identity class, neglecting the large intra - id variance caused mainly by the change of camera views. to address this issue, we propose to split each single cluster into multiple proxies and each proxy represents the instances coming from the same camera. these camera - aware proxies enable us to deal with large intra - id variance and generate more reliable pseudo labels for learning. based on the camera - aware proxies, we design both intra - and inter - camera contrastive learning components for our re - id model to effectively learn the id discrimination ability within and across cameras. meanwhile, a proxy - balanced sampling strategy is also designed, which facilitates our learning further. extensive experiments on three large - scale re - id datasets show that our proposed approach outperforms most unsupervised methods by a significant margin. especially, on the challenging msmt17 dataset, we gain $ 14. 3 \ % $ rank - 1 and $ 10. 2 \ % $ map improvements when compared to the second place. code is available at : \ texttt { https : / / github. com / terminator8758 / cap - master }.
arxiv:2012.10674
we study natural composite cold dark matter candidates which are pseudo nambu - goldstone bosons ( pngb ) in models of dynamical electroweak symmetry breaking. some of these can have a significant thermal relic abundance, while others must be mainly asymmetric dark matter. by considering the thermal abundance alone we find a lower bound of mw on the pngb mass when the ( composite ) higgs is heavier than 115 gev. being pngbs, the dark matter candidates are in general light enough to be produced at the lhc.
arxiv:1007.4839
we investigate the correlation structure of pure n - mode gaussian resources which can be experimentally generated by means of squeezers and beam splitters, whose entanglement properties are generic. we show that those states are specified ( up to local unitaries ) by n ( n - 1 ) / 2 parameters, corresponding to the two - point correlations between any pair of modes. our construction yields a practical scheme to engineer such generic - entangled n - mode pure gaussian states by linear optics. we discuss our findings in the framework of gaussian matrix product states of harmonic lattices, raising connections with entanglement frustration and the entropic area law.
arxiv:quant-ph/0606190
robot autonomy in unknown, gps - denied, and complex underground environments requires real - time, robust, and accurate onboard pose estimation and mapping for reliable operations. this becomes particularly challenging in perception - degraded subterranean conditions under harsh environmental factors, including darkness, dust, and geometrically self - similar structures. this paper details compslam, a highly resilient and hierarchical multi - modal localization and mapping framework designed to address these challenges. its flexible architecture achieves resilience through redundancy by leveraging the complementary nature of pose estimates derived from diverse sensor modalities. developed during the darpa subterranean challenge, compslam was successfully deployed on all aerial, legged, and wheeled robots of team cerberus during their competition - winning final run. furthermore, it has proven to be a reliable odometry and mapping solution in various subsequent projects, with extensions enabling multi - robot map sharing for marsupial robotic deployments and collaborative mapping. this paper also introduces a comprehensive dataset acquired by a manually teleoperated quadrupedal robot, covering a significant portion of the darpa subterranean challenge finals course. this dataset evaluates compslam ' s robustness to sensor degradations as the robot traverses 740 meters in an environment characterized by highly variable geometries and demanding lighting conditions. the compslam code and the darpa subt finals dataset are made publicly available for the benefit of the robotics community
arxiv:2505.06483
we review our knowledge of the most basic properties of the agn obscuring region - its location, scale, symmetry, and mean covering factor - and discuss new evidence on the distribution of covering factors in a sample of ~ 9000 quasars with wise, ukidss, and sdss photometry. the obscuring regions of agn may be in some ways more complex than we thought - multi - scale, not symmetric, chaotic - and in some ways simpler - with no dependence on luminosity, and a covering factor distribution that may be determined by the simplest of considerations - e. g. random misalignments.
arxiv:1303.0219
we treat projective dependency trees as latent variables in our probabilistic model and induce them in such a way as to be beneficial for a downstream task, without relying on any direct tree supervision. our approach relies on gumbel perturbations and differentiable dynamic programming. unlike previous approaches to latent tree learning, we stochastically sample global structures and our parser is fully differentiable. we illustrate its effectiveness on sentiment analysis and natural language inference tasks. we also study its properties on a synthetic structure induction task. ablation studies emphasize the importance of both stochasticity and constraining latent structures to be projective trees.
arxiv:1906.09992
entanglement is widely considered the cornerstone of quantum information and an essential resource for relevant quantum effects, such as quantum teleportation, quantum cryptography, or the speed - up of quantum computing, as in shor ' s algorithm. however, up to now, there is no general characterization of entanglement for many - body systems. in this sense, it is encouraging that quantum states connected by stochastic local operations assisted with classical communication ( slocc ), which perform probabilistically the same quantum tasks, can be collected into entanglement classes. nevertheless, there is an infinite number of classes for four or more parties that may be gathered, in turn, into a finite number of entanglement families. unfortunately, we have not been able to relate all classes and families to specific properties or quantum information tasks, although a few of them have certainly raised experimental interest. here, we present a novel entanglement classification for quantum states according to their matrix - product - state structure, exemplified for the symmetric subspace. the proposed classification relates entanglement families to the interaction length of hamiltonians, establishing the first connection between entanglement classification and condensed matter. additionally, we found a natural nesting property in which the families for $ n $ parties carry over to the $ n + 1 $ case. we anticipate our proposal to be a starting point for the exploration of the connection between entanglement classification properties and condensed - matter models.
arxiv:1504.07524
high fidelity representation of shapes with arbitrary topology is an important problem for a variety of vision and graphics applications. owing to their limited resolution, classical discrete shape representations using point clouds, voxels and meshes produce low quality results when used in these applications. several implicit 3d shape representation approaches using deep neural networks have been proposed leading to significant improvements in both quality of representations as well as the impact on downstream applications. however, these methods can only be used to represent topologically closed shapes which greatly limits the class of shapes that they can represent. as a consequence, they also often require clean, watertight meshes for training. in this work, we propose dude - a deep unsigned distance embedding method which alleviates both of these shortcomings. dude is a disentangled shape representation that utilizes an unsigned distance field ( udf ) to represent proximity to a surface, and a normal vector field ( nvf ) to represent surface orientation. we show that a combination of these two ( udf + nvf ) can be used to learn high fidelity representations for arbitrary open / closed shapes. as opposed to prior work such as deepsdf, our shape representations can be directly learnt from noisy triangle soups, and do not need watertight meshes. additionally, we propose novel algorithms for extracting and rendering iso - surfaces from the learnt representations. we validate dude on benchmark 3d datasets and demonstrate that it produces significant improvements over the state of the art.
arxiv:2011.02570
ionic microgel particles in a good solvent swell to an equilibrium size determined by a balance of electrostatic and elastic forces. when crowded, ionic microgels deswell owing to a redistribution of microions inside and outside the particles. the concentration - dependent deswelling affects the interactions between the microgels, and consequently the suspension properties. we present a comprehensive theoretical study of crowding effects on thermodynamic, structural, and dynamic properties of weakly cross - linked ionic microgels in a good solvent. the microgels are modeled as microion - and solvent - permeable colloidal spheres with fixed charge uniformly distributed over the polymer gel backbone, whose elastic and solvent - interaction free energies are described using flory - rehner theory. two mean - field methods for calculating the crowding - dependent microgel radius are investigated, and combined with calculations of the net microgel charge characterizing the electrostatic part of an effective microgel pair potential, with charge renormalization accounted for. using this effective pair potential, thermodynamic and static suspension properties are calculated including the osmotic pressure and microgel pair distribution function. the latter is used in our calculations of dynamic suspension properties, where we account for hydrodynamic interactions. results for diffusion and rheological properties are presented over ranges of microgel concentration and charge. we show that deswelling mildly enhances self - and collective diffusion and the osmotic pressure, lowers the suspension viscosity, and significantly shifts the suspension crystallization point to higher concentrations. the paper presents a bottom - up approach to efficiently computing suspension properties of crowded ionic microgels using single - particle characteristics.
arxiv:1910.00833
context : ensuring safety for any sophisticated system is getting more complex due to the rising number of features and functionalities. this calls for formal methods to entrust confidence in such systems. nevertheless, using formal methods in industry is demanding because of their lack of usability and the difficulty of understanding verification results. objective : we evaluate the acceptance of formal methods by bosch automotive engineers, particularly whether the difficulty of understanding verification results can be reduced. method : we perform two different exploratory studies. first, we conduct a user survey to explore challenges in identifying inconsistent specifications and using formal methods by bosch automotive engineers. second, we perform a one - group pretest - posttest experiment to collect impressions from bosch engineers familiar with formal methods to evaluate whether understanding verification results is simplified by our counterexample explanation approach. results : the results from the user survey indicate that identifying refinement inconsistencies, understanding formal notations, and interpreting verification results are challenging. nevertheless, engineers are still interested in using formal methods in real - world development processes because it could reduce the manual effort for verification. additionally, they also believe formal methods could make the system safer. furthermore, the one - group pretest - posttest experiment results indicate that engineers are more comfortable understanding the counterexample explanation than the raw model checker output. limitations : the main limitation of this study is the generalizability beyond the target group of bosch automotive engineers.
arxiv:2304.08950