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as shown by ashtekar in the mid 80 ' s, general relativity can be extended to incorporate degenerate metrics. this extension is not unique, however, as one can change the form of the hamiltonian constraints and obtain an { \ it alternative } degenerate extension of general relativity that disagrees with ashtekar ' s original theory when the triads vectors are degenerate. in this paper, the constraint algebra of a particular alternative theory is explicitly evaluated and compared with that of ashtekar ' s original degenerate extension. a generic classification of the difference between the two theories is given in terms of the degeneracy and surface - forming properties of the triad vectors. ( this classification is valid when the degeneracy and surface - forming properties of the triad vectors is the same everywhere in an open set about a point in space. ) if the triad vectors are degenerate and surface - forming, then all the secondary constraints of the alternative degenerate extension are satisfied as a consequence of the primary constraints, and the constraints of this theory are weaker than those of ashtekar ' s. if the degenerate triad vectors are not surface - forming, then the first secondary constraint of the alternative theory already implies equivalence with ashtekar ' s degenerate extension. what happens when the degeneracy and surface - forming properties of the triad vectors change from point to point is an open question. | arxiv:gr-qc/9306034 |
the nitrogen vacancy ( nv ) center in diamond is a sensitive probe of magnetic field and a promising qubit candidate for quantum information processing. the performance of many nv - based devices improves by aligning the nv ( s ) parallel to a single crystallographic direction. using ab initio theoretical techniques, we show that nv orientation can be controlled by high - temperature annealing in the presence of strain under currently accessible experimental conditions. we find that $ ( 89 \ pm7 ) \ % $ of nvs align along the [ 111 ] crystallographic direction under 2 \ % compressive biaxial strain ( perpendicular to [ 111 ] ) and an annealing temperature of 970 $ ^ \ circ $ c. | arxiv:1406.0041 |
two - photon decays of vector mesons and dilepton decays of scalar mesons which are forbidden in vacuum and can occur in dense baryonic matter due to the explicit violation of lorentz symmetry are described within a quark model of the nambu - - jona - lasinio type. the temperature and chemical potential dependence of these processes is investigated. it is found that their contribution to the production of photons and leptons in heavy - ion collisions is enhanced near the conditions corresponding to the restoration of chiral symmetry. moreover, in the case of the a _ 0 meson and especially the \ rho - meson, a resonant behaviour ( an additional amplification ) is observed due to the degeneration of \ rho and a _ 0 masses when a hot hadron matter is approaching a chirally symmetric phase. | arxiv:hep-ph/0510329 |
the spectral and transport properties of a non - hermitian tight - binding lattice with unidirectional hopping are theoretically investigated in three different geometrical settings. it is shown that, while for the infinitely - extended ( open ) and for the ring lattice geometries the spectrum is complex, lattice truncation makes the spectrum real. however, an exceptional point of order equal to the number of lattice sites emerges. when a homogeneous dc force is applied to the lattice, in all cases an equally - spaced real wannier - stark ladder spectrum is obtained, corresponding to periodic oscillatory dynamics in real space. possible physical realizations of non - hermitian lattices with unidirectional hopping are briefly discussed. | arxiv:1404.3662 |
we propose a simple and systematic method to quantize the cranking model and to calculate the matrix elements of intrinsic operators entering the generalized intensity relations. an example of the application is given to show the coriolis coupling effects for b ( e3 ) values of the 3 - octupole states in gd isotopes. | arxiv:nucl-th/9612003 |
the nature of the enigmatic pseudogap region of the phase diagram is the most important and intriguing unsolved puzzle in the field of high transition - temperature ( tc ) superconductivity. this region, the temperature range above tc and below a characteristic temperature t *, is characterized by highly anomalous magnetic, charge transport, thermodynamic and optical properties. associated with the pseudogap puzzle are open questions pertaining to the number of distinct phases and the presence of a quantum - critical point underneath the superconducting dome. here we use polarized neutron diffraction to demonstrate for the model superconductor hgba2cuo4 + d ( hg1201 ) that t * marks the onset of an unusual magnetic order, and hence a novel state of matter with broken time - reversal symmetry. together with prior results for yba2cu3o6 + d ( ybco ), this observation constitutes an essential and decisive demonstration of the universal existence of such a state. the new findings appear to rule out a large class of theories that regard t * as a crossover temperature rather than a phase transition temperature. instead, they are consistent with a variant of previously proposed charge - current - loop order that involves apical oxygen orbitals, and with the notion that many of the unusual properties arise from the presence of a quantum - critical point. | arxiv:0805.2959 |
hermite reduction is a classical algorithmic tool in symbolic integration. it is used to decompose a given rational function as a sum of a function with simple poles and the derivative of another rational function. we extend hermite reduction to arbitrary linear differential operators instead of the pure derivative, and develop efficient algorithms for this reduction. we then apply the generalized hermite reduction to the computation of linear operators satisfied by single definite integrals of d - finite functions of several continuous or discrete parameters. the resulting algorithm is a generalization of reduction - based methods for creative telescoping. | arxiv:1805.03445 |
in the first part of the paper we characterize certain systems of first order nonlinear differential equations whose space of solutions is an $ \ mathfrak { sl } _ 2 ( \ mathbb { c } ) $ - module. we prove that such systems, called ramanujan systems of rankin - cohen type, have a special shape and are precisely the ones whose solution space admits a rankin - cohen structure. in the second part of the paper we consider triangle groups $ \ delta ( n, m, \ infty ) $. by means of modular embeddings, we associate to every such group a number of systems of non linear odes whose solutions are algebraically independent twisted modular forms. in particular, all rational weight modular forms on $ \ delta ( n, m, \ infty ) $ are generated by the solutions of one such system ( which is of rankin - cohen type ). as a corollary we find new relations for the gauss hypergeometric function evaluated at functions on the upper half - plane. to demonstrate the power of our approach in the non classical setting, we construct the space of integral weight twisted modular form on $ \ delta ( 2, 5, \ infty ) $ from solutions of systems of nonlinear odes. | arxiv:2207.07686 |
correct fusion of data from two sensors is not possible without an accurate estimate of their relative pose, which can be determined through the process of extrinsic calibration. when two or more sensors are capable of producing their own egomotion estimates ( i. e., measurements of their trajectories through an environment ), the ' hand - eye ' formulation of extrinsic calibration can be employed. in this paper, we extend our recent work on a convex optimization approach for hand - eye calibration to the case where one of the sensors cannot observe the scale of its translational motion ( e. g., a monocular camera observing an unmapped environment ). we prove that our technique is able to provide a certifiably globally optimal solution to both the known - and unknown - scale variants of hand - eye calibration, provided that the measurement noise is bounded. herein, we focus on the theoretical aspects of the problem, show the tightness and stability of our solution, and demonstrate the optimality and speed of our algorithm through experiments with synthetic data. | arxiv:2005.08298 |
inference into the unobservable past in order to meaningfully study it. " the assumption of spatial and temporal invariance of natural laws is by no means unique to geology since it amounts to a warrant for inductive inference which, as bacon showed nearly four hundred years ago, is the basic mode of reasoning in empirical science. without assuming this spatial and temporal invariance, we have no basis for extrapolating from the known to the unknown and, therefore, no way of reaching general conclusions from a finite number of observations. ( since the assumption is itself vindicated by induction, it can in no way " prove " the validity of induction — an endeavor virtually abandoned after hume demonstrated its futility two centuries ago ). " gould also notes that natural processes such as lyell ' s " uniformity of process " are an assumption : " as such, it is another a priori assumption shared by all scientists and not a statement about the empirical world. " according to r. hooykaas : " the principle of uniformity is not a law, not a rule established after comparison of facts, but a principle, preceding the observation of facts... it is the logical principle of parsimony of causes and of economy of scientific notions. by explaining past changes by analogy with present phenomena, a limit is set to conjecture, for there is only one way in which two things are equal, but there are an infinity of ways in which they could be supposed different. " that experimental procedures will be done satisfactorily without any deliberate or unintentional mistakes that will influence the results. that experimenters won ' t be significantly biased by their presumptions. that random sampling is representative of the entire population. a simple random sample ( srs ) is the most basic probabilistic option used for creating a sample from a population. the benefit of srs is that the investigator is guaranteed to choose a sample that represents the population that ensures statistically valid conclusions. = = = coherentism = = = in contrast to the view that science rests on foundational assumptions, coherentism asserts that statements are justified by being a part of a coherent system. or, rather, individual statements cannot be validated on their own : only coherent systems can be justified. a prediction of a transit of venus is justified by its being coherent with broader beliefs about celestial mechanics and earlier observations. as explained above, observation is a cognitive act. that is, it relies on a pre - existing understanding, a systematic set | https://en.wikipedia.org/wiki/Philosophy_of_science |
the higgs search strategies in minimal non - supersymmetric extensions of the sm are discussed. | arxiv:hep-ph/0009310 |
the pointing system of the prototype of the large size telescope ( lst - 1 ) for the cherenkov telescope array observatory, should ensure mapping of the gamma - ray image of a point - like source in the cherenkov camera to the sky coordinates with a precision better than 14 arcseconds. detailed studies of the telescope deformations are performed in order to disentangle different deformations and quantify their contributions to the miss - pointing, to learn how to correct for them, and finally how to design the system for offline and online pointing corrections. the lst - 1 pointing precision system consist of several devices mounted at the center of the dish : starguider camera ( sg ), camera displacement monitor ( cdm ), two inclinometers, four distance meters, and an optical axis reference laser ( oarl ), working together with the leds mounted in a circle around the cherenkov camera. the online pointing corrections are based on a bending model as currently done by existing iacts. the offline corrections will be performed combining measurements done by the sg and cdm cameras. sg will provide the position of the cherenkov camera center with respect to the sky coordinates with a precision of 5 arcseconds, while cdm will provide the deviation of the telescope optical axis defined by the oarl spots with respect to the cherenkov camera center with a precision better than 5 arcseconds. laboratory measurements on dedicated test benches showed that the required pointing precision can be achieved for sg, cdm and inclinometer. | arxiv:1908.01269 |
cubic bas has received recent attention for its large electron and hole mobilities and large thermal conductivity. this is a rare and much desired combination in semiconductor industry : commercial semiconductors typically have high electron mobilities, or hole mobilities, or large thermal conductivities, but not all of them together. here we report predictions from an advanced self - consistent many body perturbative theory and show that with respect to one - particle properties, bas is strikingly similar to si. there are some important differences, notably there is an unusually small variation in the valence band masses. with respect to two - particle properties, significant differences with si appear. we report the excitonic spectrum for both q = 0 and finite q, and show that while the direct gap in cubic bas is about 4 ev, dark excitons can be observed down to about $ \ sim $ 1. 5 ev, which may play a crucial role in application of bas in optoelectronics. | arxiv:2305.17215 |
quantum coherence ( qch ) is considered to be a key ingredient in quantum resource theories and also plays a pivotal role in the design and implementation of various information processing tasks. consequently, it becomes important for us to create more number coherent quantum states between two labs from a given coherent state shared initially. we call this process as \ textbf { broadcasting of quantum coherence ( qch ) }. in this work we extensively study the problem of broadcasting of qch. in order to have a holistic view of broadcasting, we start with a most general representation two qubit mixed state in terms of bloch vectors. as a cloning transformation we have used universal symmetric optimal buzek - hillery ( bh ) cloner locally as well as non locally. remarkably, we find that in either of the case it is impossible to do optimal broadcasting of qch. further we show in case of non optimal broadcasting it is impossible to increase qch of the state by both local and non local cloning operations. in non optimal case, apart from general result we consider examples like, a ) werner like states ( wls ) and b ) bell diagonal states ( bds ) and obtain ranges for broadcasting in terms of input state parameters. | arxiv:1605.02458 |
magnetic flux emergence has been shown to be a key mechanism for unleashing a wide variety of solar phenomena. however, there are still open questions concerning the rise of the magnetized plasma through the atmosphere, mainly in the chromosphere, where the plasma departs from local thermodynamic equilibrium ( lte ) and is partially ionized. we aim to investigate the impact of the nonequilibrium ( neq ) ionization and recombination and molecule formation of hydrogen, as well as ambipolar diffusion, on the dynamics and thermodynamics of the flux emergence process. using the bifrost code, we performed 2. 5d numerical experiments of magnetic flux emergence from the convection zone up to the corona. the experiments include the neq ionization and recombination of atomic hydrogen, the neq formation and dissociation of h2 molecules, and the ambipolar diffusion term of the generalized ohm ' s law. our experiments show that the lte assumption substantially underestimates the ionization fraction in most of the emerged region, leading to an artificial increase in the ambipolar diffusion and, therefore, in the heating and temperatures as compared to those found when taking the neq effects on the hydrogen ion population into account. we see that lte also overestimates the number density of h2 molecules within the emerged region, thus mistakenly magnifying the exothermic contribution of the h2 molecule formation to the thermal energy during the flux emergence process. we find that the ambipolar diffusion does not significantly affect the amount of total unsigned emerged magnetic flux, but it is important in the shocks that cross the emerged region, heating the plasma on characteristic times ranging from 0. 1 to 100 s. we also briefly discuss the importance of including elements heavier than hydrogen in the equation of state so as not to overestimate the role of ambipolar diffusion in the atmosphere. | arxiv:1912.01015 |
we present a method for microtubule tracking in electron microscopy volumes. our method first identifies a sparse set of voxels that likely belong to microtubules. similar to prior work, we then enumerate potential edges between these voxels, which we represent in a candidate graph. tracks of microtubules are found by selecting nodes and edges in the candidate graph by solving a constrained optimization problem incorporating biological priors on microtubule structure. for this, we present a novel integer linear programming formulation, which results in speed - ups of three orders of magnitude and an increase of 53 % in accuracy compared to prior art ( evaluated on three 1. 2 x 4 x 4 $ \ mu $ m volumes of drosophila neural tissue ). we also propose a scheme to solve the optimization problem in a block - wise fashion, which allows distributed tracking and is necessary to process very large electron microscopy volumes. finally, we release a benchmark dataset for microtubule tracking, here used for training, testing and validation, consisting of eight 30 x 1000 x 1000 voxel blocks ( 1. 2 x 4 x 4 $ \ mu $ m ) of densely annotated microtubules in the cremi data set ( https : / / github. com / nilsec / micron ). | arxiv:2009.08371 |
we present exponential and super factorial lower bounds on the number of hamiltonian cycles passing through any edge of the basis graphs of a graphic, generalized catalan and uniform matroids. all lower bounds were obtained by a common general strategy based on counting appropriated cycles of length four in the corresponding matroid basis graph. | arxiv:1608.02635 |
mars has been successfully explored by various space firms. globally, 44 mission attempts were made, lamentably 26 encountered setbacks. there have been instances where a trivial error in the progressive accomplishment of spaceflight sequence might prompt in an extreme loss. hence in this paper, we have investigated several failure records and investigation reports of spacecraft attempted towards mars. the report comprises a precise and summarized report assessed from various adequate online resources as well as published research articles. analyzing records, spaceflight sequence charts, and mission targets achieved were technically tabularized beginning from launch to the mars landing. additionally, we have estimated approximate mission duration, the rate of failure, and their proportions and were graphically portrayed. further, we have generated graphical representations of the number of spacecraft launches concerning the country, type of spacecraft, and launch vehicles. | arxiv:1903.02461 |
suppose that fourier transform of a function f is zero on the interval [ - a, a ]. we prove that the lower density of sign changes of f is at least a / pi, provided that f is a locally integrable temperate distribution in the sense of beurling, with non - quasianalytic weight. we construct an example showing that the last condition cannot be omitted. | arxiv:math/0301060 |
the calculation of material phonon thermal conductivity from density functional theory calculations requires computationally expensive evaluation of anharmonic interatomic force constants and has remained a computational bottleneck in the high - throughput discovery of materials. in this work, we present a machine learning - assisted approach for the extraction of anharmonic force constants through local learning of the potential energy surface. we demonstrate our approach on a diverse collection of 220 ternary materials for which the total computational time for anharmonic force constants evaluation is reduced by more than an order of magnitude from 480, 000 cpu - hours to less than 12, 000 cpu - hours while preserving the thermal conductivity prediction accuracy to within 10 %. our approach removes a major hurdle in computational thermal conductivity evaluation and will pave the way forward for the high - throughput discovery of materials. | arxiv:2409.00360 |
we introduce a new ` ` greedy cleaning ' ' model where a star - like state space ( containing n half - lines connected by the origin ) is covered by a homogeneous poisson process of ` ` dust particles ' ', and n ^ { \ alpha } cleaners / workers proceed with cleaning in a ` ` greedy ' ' manner : each worker chooses the closest particle next. assuming \ alpha \ in ( 0, 1 ), we analyse the asymptotic behaviour of the workers, as n \ to \ infty. we show that eventually all of them escape to infinity and that the way how do they do it depends on the value of \ alpha. | arxiv:1910.01166 |
we present x - ray spectral analysis of 20 point - like x - ray sources detected in chandra planetary nebula survey ( chanplans ) observations of 59 planetary nebulae ( pne ) in the solar neighborhood. most of these 20 detections are associated with luminous central stars within relatively young, compact nebulae. the vast majority of these point - like x - ray - emitting sources at pn cores display relatively " hard " ( $ \ geq0. 5 $ ~ kev ) x - ray emission components that are unlikely to be due to photospheric emission from the hot central stars ( cspn ). instead, we demonstrate that these sources are well modeled by optically - thin thermal plasmas. from the plasma properties, we identify two classes of cspn x - ray emission : ( 1 ) high - temperature plasmas with x - ray luminosities, $ l _ { \ rm x } $, that appear uncorrelated with the cspn bolometric luminosity, $ l _ { \ rm bol } $ ; and ( 2 ) lower - temperature plasmas with $ l _ { \ rm x } / l _ { \ rm bol } \ sim10 ^ { - 7 } $. we suggest these two classes correspond to the physical processes of magnetically active binary companions and self - shocking stellar winds, respectively. in many cases this conclusion is supported by corroborative multiwavelength evidence for the wind and binary properties of the pn central stars. by thus honing in on the origins of x - ray emission from pn central stars, we enhance the ability of cspn x - ray sources to constrain models of pn shaping that invoke wind interactions and binarity. | arxiv:1412.2793 |
recent years, multi - hop reasoning has been widely studied for knowledge graph ( kg ) reasoning due to its efficacy and interpretability. however, previous multi - hop reasoning approaches are subject to two primary shortcomings. first, agents struggle to learn effective and robust policies at the early phase due to sparse rewards. second, these approaches often falter on specific datasets like sparse knowledge graphs, where agents are required to traverse lengthy reasoning paths. to address these problems, we propose a multi - hop reasoning model with dual agents based on hierarchical reinforcement learning ( hrl ), which is named fulora. fulora tackles the above reasoning challenges by efficient guidance - exploration between dual agents. the high - level agent walks on the simplified knowledge graph to provide stage - wise hints for the low - level agent walking on the original knowledge graph. in this framework, the low - level agent optimizes a value function that balances two objectives : ( 1 ) maximizing return, and ( 2 ) integrating efficient guidance from the high - level agent. experiments conducted on three real - word knowledge graph datasets demonstrate that fulora outperforms rl - based baselines, especially in the case of long - distance reasoning. | arxiv:2408.01880 |
water under tension, as can be found in several systems including tree vessels, is metastable. cavitation can spontaneously occur, nucleating a bubble. we investigate the dynamics of spon - taneous or triggered cavitation inside water filled microcavities of a hydrogel. results show that a stable bubble is created in only a microsecond timescale, after transient oscillations. then, a diffusion driven expansion leads to filling of the cavity. analysis reveals that the nucleation of a bubble releases a tension of several tens of mpa, and a simple model captures the different time scales of the expansion process. | arxiv:1105.4104 |
achieving an end - to - end low - latency for computations offloading, in mobile edge computing ( mec ) systems, is still a critical design problem. this is because the offloading of computational tasks via the mec servers entails the use of uplink ( ul ) and downlink ( dl ) radio links that are usually assumed to be coupled to a single base station ( bs ). however, for heterogeneous networks, a new architectural paradigm whereby ul and dl are not associated with the same bs is proposed and seen to provide gains in network throughput due to the improved ul performance. motivated by such gains, and by using typical results from stochastic geometry, we formulate the offloading latency for the mec - based scheme with decoupled ul / dl association, or decoupled access, and compare its performance to the conventional coupled access scheme. despite the backhaul delay necessary for the communication between the two serving bss in ul and dl, the offloading scheme with decoupled access is still capable of providing a fairly lower offloading latency compared to the conventional offloading scheme with coupled access. | arxiv:1809.04717 |
the colbert model has recently been proposed as an effective bert based ranker. by adopting a late interaction mechanism, a major advantage of colbert is that document representations can be precomputed in advance. however, the big downside of the model is the index size, which scales linearly with the number of tokens in the collection. in this paper, we study various designs for colbert models in order to attack this problem. while compression techniques have been explored to reduce the index size, in this paper we study token pruning techniques for colbert. we compare simple heuristics, as well as a single layer of attention mechanism to select the tokens to keep at indexing time. our experiments show that colbert indexes can be pruned up to 30 \ % on the ms marco passage collection without a significant drop in performance. finally, we experiment on ms marco documents, which reveal several challenges for such mechanism. | arxiv:2112.06540 |
we present a series of arguments showing that the seebeck coefficient can be used as a decisive experiment to characterize the nature of the quantum critical point ( qcp ) in heavy fermion compounds. being reactive almost exclusively to the presence of delocalized entropic carriers, the seebeck coefficient shows a drastic collapse at the kondo breakdown qcp, as the reconstruction of the fermi surface takes place. in contrast, around a spin density wave ( sdw ) qcp, the seebeck coefficient is broadly symmetric. we discuss the possibility of a change of sign at the qcp, the characteristic variation of $ | s / t | $ with temperature and external parameter, as well as the capacity of the seebeck coefficient to distinguish between localized and itinerant anti - ferromagnetism ( af ). suggestions of experiments are given in the case of four non conventional compounds : ybrh $ _ 2 $ si $ _ 2 $, ce ( mn ) in $ _ 5 $, cecu $ _ { 6 - x } $ au $ _ x $ and uru $ _ 2 $ si $ _ 2 $. | arxiv:1002.2612 |
a complete classification of binary doubly even self - dual codes of length 40 is given. as a consequence, a classification of binary extremal self - dual codes of length 38 is also given. | arxiv:1104.3727 |
flow delegation is a flexible technique to mitigate flow table capacity bottlenecks in software - defined networks ( sdn ). such bottlenecks occur when sdn switches provide insufficient flow table capacity which leads to performance degradation and network failures. flow delegation addresses this problem by automatically relocating flow rules from a bottlenecked switch to neighboring switches with spare capacity. this paper introduces a new algorithm to efficiently perform flow delegation based on a novel delegation template abstraction and multi - period multi - objective optimization. different from existing work, our approach can include estimated knowledge about future network situations and deal with different optimization criteria such as link and control overhead. we discuss the problem decomposition for the new algorithm and introduce an efficient two - step heuristic. results show, that our approach performs significantly better than the simple greedy algorithm used in earlier work and is capable of handling flow delegation for networks with hundreds of switches. | arxiv:2109.08482 |
we introduce twisted quantum $ k $ - rings, defined via twisted $ k $ - theoretic gromov - witten invariants. we develop a toolkit for computing relations by adapting some results about ordinary quantum k rings to our setting, and discuss some applications, including ruan - zhang ' s quantum $ k $ - theory with level structure, and complete intersections inside projective space, confirming some predictions coming from physics. in addition, we formulate a ring - theoretic abelian / non - abelian correspondence conjecture, relating the quantum k - ring of a git quotient $ x / / g $ to a certain twist of the quantum k - ring of $ x / / t $, the quotient by the maximal torus. we prove this conjecture for the case of grassmanians, and use this to give another proof of the whitney relations of mihalcea - gu - sharpe - zhou in that case. | arxiv:2406.00916 |
small planets ( $ r _ { p } \ leq 4 r _ { \ oplus } $ ) are divided into rocky super - earths and gaseous sub - neptunes separated by a radius gap, but the mechanisms that produce these distinct planet populations remain unclear. binary stars are the only main - sequence systems with an observable record of the protoplanetary disk lifetime and mass reservoir, and the demographics of planets in binaries may provide insights into planet formation and evolution. to investigate the radius distribution of planets in binary star systems, we observed 207 binary systems hosting 283 confirmed and candidate transiting planets detected by the kepler mission, then recharacterized the planets while accounting for the observational biases introduced by the secondary star. we found that the population of planets in close binaries ( $ \ rho \ leq 100 $ au ) is significantly different from the planet population in wider binaries ( $ \ rho > 300 $ au ) or single stars. in contrast to planets around single stars, planets in close binaries appear to have a unimodal radius distribution with a peak near the expected super - earth peak of $ r _ { p } \ sim 1. 3 r _ { \ oplus } $ and a suppressed population of sub - neptunes. we conclude that we are observing the direct impact of a reduced disk lifetime, smaller mass reservoir, and possible altered distribution of solids reducing the sub - neptune formation efficiency. our results demonstrate the power of binary stars as a laboratory for exploring planet formation and as a controlled experiment of the impact of varied initial conditions on mature planet populations. | arxiv:2406.17648 |
we provide sufficient conditions of local solvability for partial differential operators with variable colombeau coefficients. we mainly concentrate on operators which admit a right generalized pseudodifferential parametrix and on operators which are a bounded perturbation of a differential operator with constant colombeau coefficients. the local solutions are intended in the colombeau algebra $ \ g ( \ om ) $ as well as in the dual $ \ ll ( \ gc ( \ om ), \ wt { \ c } ) $. | arxiv:0902.0508 |
we propose a possibility to simulate the exciton - polariton ( ep ) system in the lossless limit, which is not currently available in semiconductor microcavities, by means of a simple optical dual - core waveguide, with one core carrying the nonlinearity and operating close to the zero - group - velocity - dispersion ( gvd ) point, and the other core being linear and dispersive. both 2d and 1d ep systems may be emulated by means of this optical setting. in the framework of this system, we find that, while the uniform state corresponding to the lower branch of the nonlinear dispersion relation is stable against small perturbations, the upper branch is always subject to the modulational instability ( mi ). the stability and instability are verified by direct simulations too. we analyze collective excitations on top of the stable lower - branch state, which include a bogoliubov - like gapless mode and a gapped one. analytical results are obtained for the corresponding sound velocity and energy gap. the effect of a uniform phase gradient ( superflow ) on the stability is considered too, with a conclusion that the lower - branch state becomes unstable above a critical wavenumber of the flux. finally, we demonstrate that the stable 1d state may carry robust dark solitons. | arxiv:1409.2346 |
text - rich graphs, which exhibit rich textual information on nodes and edges, are prevalent across a wide range of real - world business applications. large language models ( llms ) have demonstrated remarkable abilities in understanding text, which also introduced the potential for more expressive modeling in text - rich graphs. despite these capabilities, efficiently applying llms to representation learning on graphs presents significant challenges. recently, parameter - efficient fine - tuning methods for llms have enabled efficient new task generalization with minimal time and memory consumption. inspired by this, we introduce graph - aware parameter - efficient fine - tuning - gpeft, a novel approach for efficient graph representation learning with llms on text - rich graphs. specifically, we utilize a graph neural network ( gnn ) to encode structural information from neighboring nodes into a graph prompt. this prompt is then inserted at the beginning of the text sequence. to improve the quality of graph prompts, we pre - trained the gnn to assist the frozen llm in predicting the next token in the node text. compared with existing joint gnn and lms, our method directly generate the node embeddings from large language models with an affordable fine - tuning cost. we validate our approach through comprehensive experiments conducted on 8 different text - rich graphs, observing an average improvement of 2 % in hit @ 1 and mean reciprocal rank ( mrr ) in link prediction evaluations. our results demonstrate the efficacy and efficiency of our model, showing that it can be smoothly integrated with various large language models, including opt, llama and falcon. | arxiv:2404.18271 |
test takers do not give equally reliable responses. they take different responding strategies and they do not make the same effort to solve the problem and answer the question correctly. the consequences of differential test takers ' behavior are numerous : the test item parameters could be biased, there might emerge differential item functioning for certain subgroups, estimation of test taker ' s ability might have greater error, etc. all the consequences are becoming more prominent at low - stakes tests where test takers ' motivation is additionally decreased. we had analyzed a computer based test in physics and tried to find and describe relationship between the item response time and the item response likelihood. we have found that magnitude of such relationship depends on the item difficulty parameter. we have also noticed that boys, who respond faster, in average, give responses with greater likelihood than the boys who respond slower. the same trend was not detected for girls. | arxiv:0901.4356 |
the five exceptional simple lie algebras over the complex number are included one within the other as $ g _ 2 \ subset f _ 4 \ subset e _ 6 \ subset e _ 7 \ subset e _ 8 $. the biggest one, $ e _ 8 $, is in many ways the most mysterious. this article surveys what is known about it including many recent results, focusing on the point of view of lie algebras and algebraic groups over fields. | arxiv:1605.01721 |
accurate estimation of core ( irreversibly damaged tissue ) and penumbra ( salvageable tissue ) volumes is essential for ischemic stroke treatment decisions. perfusion ct, the clinical standard, estimates these volumes but is affected by variations in deconvolution algorithms, implementations, and thresholds. core tissue expands over time, with growth rates influenced by thrombus location, collateral circulation, and inherent patient - specific factors. understanding this tissue growth is crucial for determining the need to transfer patients to comprehensive stroke centers, predicting the benefits of additional reperfusion attempts during mechanical thrombectomy, and forecasting final clinical outcomes. this work presents the isles ' 24 challenge, which addresses final post - treatment stroke infarct prediction from pre - interventional acute stroke imaging and clinical data. isles ' 24 establishes a unique 360 - degree setting where all feasibly accessible clinical data are available for participants, including full ct acute stroke imaging, sub - acute follow - up mri, and clinical tabular data. the contributions of this work are two - fold : first, we introduce a standardized benchmarking of final stroke infarct segmentation algorithms through the isles ' 24 challenge ; second, we provide insights into infarct segmentation using multimodal imaging and clinical data strategies by identifying outperforming methods on a finely curated dataset. the outputs of this challenge are anticipated to enhance clinical decision - making and improve patient outcome predictions. all isles ' 24 materials, including data, performance evaluation scripts, and leading algorithmic strategies, are available to the research community following \ url { https : / / isles - 24. grand - challenge. org / }. | arxiv:2408.10966 |
cryogenic scanning tunneling microscopy is employed to investigate the stoichiometry and defects of epitaxial fese thin films on srtio3 ( 001 ) substrates under various post - growth annealing conditions. low - temperature annealing with an excess supply of se leads to formation of fe vacancies and superstructures, accompanied by a superconductivity ( metal ) - to - insulator transition in fese films. by contrast, high - temperature annealing could eliminate the fe vacancies and superstructures, and thus recover the high - temperature superconducting phase of monolayer fese films. we also observe multilayer fese during low - temperature annealing, which is revealed to link with fe vacancy formation and adatom migration. our results document very special roles of film stoichiometry and help unravel several controversies in the properties of monolayer fese films. | arxiv:2007.09823 |
we show that, in cosmological microlensing, corrections of order $ v / c \ sim \ delta \ lambda / \ lambda $, to the deflection angle of light beams from a distant source are not negligible and that all microlensing quantities should be corrected up to this order independently of the cosmological model used. | arxiv:astro-ph/9902373 |
design of an effective and reliable communication network supporting smart grid applications requires a selection of appropriate communication technologies and protocols. the objective of this paper is to study and quantify the capabilities of an advanced metering infrastructure ( ami ) to support the simultaneous operation of major smart grid functions. these include smart metering, price - induced controls, distribution automation, demand response and electric vehicle charging / discharging applications in terms of throughput and latency. opnet is used to simulate the performance of selected communication technologies and protocols. research findings indicate that smart grid applications can operate simultaneously by piggybacking on an existing ami infrastructure and still achieve their latency requirements. | arxiv:1901.11509 |
we present a review of recent qcd related results from the fermilab tevatron fixed target and collider experiments. topics include jet and boson production, w boson and top quark mass measurements, and studies of cp violation. | arxiv:hep-ex/9906016 |
let $ x $ be a finite vertex - transitive graph of valency $ d $, and let $ a $ be the full automorphism group of $ x $. then the arc - type of $ x $ is defined in terms of the sizes of the orbits of the action of the stabiliser $ a _ v $ of a given vertex $ v $ on the set of arcs incident with $ v $. specifically, the arc - type is the partition of $ d $ as the sum $ $ n _ 1 + n _ 2 + \ dots + n _ t + ( m _ 1 + m _ 1 ) + ( m _ 2 + m _ 2 ) + \ dots + ( m _ s + m _ s ), $ $ where $ n _ 1, n _ 2, \ dots, n _ t $ are the sizes of the self - paired orbits, and $ m _ 1, m _ 1, m _ 2, m _ 2, \ dots, m _ s, m _ s $ are the sizes of the non - self - paired orbits, in descending order. in this paper, we find the arc - types of several families of graphs. also we show that the arc - type of a cartesian product of two ` relatively prime ' graphs is the natural sum of their arc - types. then using these observations, we show that with the exception of $ 1 + 1 $ and $ ( 1 + 1 ) $, every partition as defined above is realisable, in the sense that there exists at least one graph with the given partition as its arc - type. | arxiv:1505.02029 |
in the attention economy, online platforms are incentivized to design products that maximize user engagement, even when such practices conflict with users ' best interests. we conducted a structured content analysis of all very large online platforms ( vlops ) to identify the designs these influential apps and sites use to capture attention and extend engagement. specifically, we conducted this analysis posing as a teenager to identify the designs that young people are exposed to. we find that vlops use four strategies to extend teens ' use : pressuring, enticing, trapping, and lulling them into spending more time online. we report on a hierarchical taxonomy organizing the 63 designs that fall under these categories. applying this taxonomy to all 17 vlops, we identify 583 instances of engagement - prolonging designs, with social media platforms using twice as many as other vlops. we present three vignettes illustrating how these designs reinforce one another in practice. we further contribute a graphical dataset of videos illustrating these features in the wild. | arxiv:2411.12083 |
we show that a finitely generated subgroup of the genus two handlebody group is stable if and only if the orbit map to the disk graph is a quasi - isometric embedding. to this end, we prove that the genus two handlebody group is a hierarchically hyperbolic group, and that the maximal hyperbolic space in the hierarchy is quasi - isometric to the disk graph of a genus two handlebody by appealing to a construction of hamenst \ " adt - hensel. we then utilize the characterization of stable subgroups of hierarchically hyperbolic groups provided by abbott - behrstock - berlyne - durham - russell. we also present several applications of the main theorems, and show that the higher genus analogues of the genus two results do not hold. | arxiv:2009.05067 |
we present a novel bird ' s - eye - view ( bev ) detector with perspective supervision, which converges faster and better suits modern image backbones. existing state - of - the - art bev detectors are often tied to certain depth pre - trained backbones like vovnet, hindering the synergy between booming image backbones and bev detectors. to address this limitation, we prioritize easing the optimization of bev detectors by introducing perspective space supervision. to this end, we propose a two - stage bev detector, where proposals from the perspective head are fed into the bird ' s - eye - view head for final predictions. to evaluate the effectiveness of our model, we conduct extensive ablation studies focusing on the form of supervision and the generality of the proposed detector. the proposed method is verified with a wide spectrum of traditional and modern image backbones and achieves new sota results on the large - scale nuscenes dataset. the code shall be released soon. | arxiv:2211.10439 |
magnetic reconnection is the most likely mechanism responsible for the high temperature events that are observed in strongly magnetized locations around the temperature minimum in the low solar chromosphere. this work improves upon our previous work [ " magnetic reconnection in strongly magnetized regions of the low solar chromosphere ", the astrophysical journal 852, 95 ( 2018 ) ] by using a more realistic radiative cooling model computed from the opacity project and the chianti database. we find that the rate of ionization of the neutral component of the plasma is still faster than recombination within the current sheet region. for low $ \ beta $ plasmas, the ionized and neutral fluid flows are well - coupled throughout the reconnection region resembling the single - fluid sweet - parker model dynamics. decoupling of the ion and neutral inflows appears in the higher $ \ beta $ case with $ \ beta _ 0 = 1. 46 $, which leads to a reconnection rate about three times faster than the rate predicted by the sweet - parker model. in all cases, the plasma temperature increases with time inside the current sheet, and the maximum value is above $ 2 \ times10 ^ 4 $ ~ k when the reconnection magnetic field strength is greater than $ 500 $ ~ g. while the more realistic radiative cooling model does not result in qualitative changes of the characteristics of magnetic reconnection, it is necessary for studying the variations of the plasma temperature and ionization fraction inside current sheets in strongly magnetized regions of the low solar atmosphere. it is also important for studying energy conversion during the magnetic reconnection process when the hydrogen - dominated plasma approaches full ionization. | arxiv:1804.05631 |
the recent discovery of strong spin hall effects ( she ) in 2d layered topological semimetals has attracted intensive attention due to its exotic electronic properties and potential applications in spintronic devices. in this paper, we systematically study the topological properties and intrinsic she of layered transition metal carbides $ m _ { 2 } \ rm { c } $ ( $ m = \ rm { v }, \ rm { nb }, \ rm { ta } $ ). the results show that both bulk and monolayer $ m _ { 2 } \ rm { c } $ have symmetry - protected nodal points ( nps ) and lines ( nls ) originating from the $ d $ band crossing near the fermi level ( $ e _ f $ ). the inclusion of soc breaks the degeneracy of nls and nps, contributing to large spin hall conductivity ( shc ) up to $ \ sim $ 1100 and $ \ sim $ 200 $ ( \ hbar / e ) ( \ omega \ mathrm { cm } ) ^ { - 1 } $ for bulk and monolayer ta $ _ { 2 } $ c, respectively. remarkably, we find that magnitude of shc exhibits a significant enhancement by increasing the layer number. for eight - layer ta $ _ { 2 } $ c, the maximum value of shc can reach up to $ \ sim $ 600 $ ( \ hbar / e ) ( \ omega \ mathrm { cm } ) ^ { - 1 } $, comparable to many reported 3d topological materials. analysis of spin berry curvature reveals that the large shc originates from layer - number - dependent nodal line structure near the $ e _ f $, in which the repeated crossover between valence and conduction bands creates large amounts of nps along the $ \ gamma \ rm { - k } $ route. our findings not only provide a new platform for experimental research of low - dimensional she, but also suggest an effective way of realizing giant she by controlling layer thickness. | arxiv:2301.01436 |
we study the sensitivity of optimal solutions of convex separable optimization problems over an integral polymatroid base polytope with respect to parameters determining both the cost of each element and the polytope. under convexity and a regularity assumption on the functional dependency of the cost function with respect to the parameters, we show that reoptimization after a change in parameters can be done by elementary local operations. applying this result, we derive that starting from any optimal solution there is a new optimal solution to new parameters such that the l1 - norm of the difference of the two solutions is at most two times the l1 norm of the difference of the parameters. we apply these sensitivity results to a class of non - cooperative polymatroid games and derive the existence of pure nash equilibria. we complement our results by showing that polymatroids are the maximal combinatorial structure enabling these results. for any non - polymatroid region, there is a corresponding optimization problem for which the sensitivity results do not hold. in addition, there is a game where the players strategies are isomorphic to the non - polymatroid region and that does not admit a pure nash equilibrium. | arxiv:1611.05372 |
type - 2 fuzzy differential equations ( t2fdes ) of order 1 are already known and the solution method of type - 2 fuzzy initial value problems ( t2fivps ) for them was given by m. mazandarani and m. najariyan \ cite { mn } in 2014. we give the solution method of second - order t2fivps in this paper. furthermore, we would like to propose new notations for type - 2 fuzzy theory where symbols tend to be complicated and misleading. in particular, the hukuhara differential symbols introduced experimentally in this paper will give us clearler meanings and expressions. | arxiv:2101.10324 |
we can obtain one solution of the hamiltonian constraint equation in the local sense. the form of the state is suggested from the up - to - down method in our previous work. the up - to - down method works for different way in treating the general metrics. in the mini - superspace approach there appears additional constraint in the 4 - dimensional quantum gravity hilbert space. however, in the general treatment of the metrics this method works as only solving technique. | arxiv:gr-qc/0605073 |
we consider a gaussian field $ x = \ { x _ t, t \ in t \ } $ with values in a banach space $ b $ defined on a parametric set $ t $ equal to $ r ^ m $ or $ z ^ m. $ it is supposed that the distribution $ \ cal p $ of $ x _ t $ is independent of $ t. $ we consider the asymptotic behavior of closed convex hulls $ $ w _ n = \ conv \ { x _ t, t \ in t _ n \ } $ $ where $ ( t _ n ) $ is an increasing sequence of subsets of $ t $ and we show that under some conditions of the weak dependence with probability 1 $ $ \ lim _ { n \ rightarrow \ infty } \ frac { 1 } { b _ n } \, w _ n = { \ cal e } $ $ ( in the sense of hausdorff distance ), where the limit shape $ { \ cal e } $ is the concentration ellipsoid of $ \ cal p. $ the asymptotic behavior of the mathematical expectations $ ef ( w _ n ), $ where $ f $ is an homogeneous function is also studied. | arxiv:1210.5590 |
the superconductor - insulator ( si ) transition in two - dimensional ta thin films is investigated by controlling both film thickness and magnetic field. an intriguing metallic phase intervening superconductor and an insulator phase is observed within a narrow range of film thickness and magnetic field. finite scaling analysis has been performed to investigate the nature of the si transition in the thickness - tuned metallic and superconducting samples. the critical exponents in the disorder - induced metallic samples are clearly different from the exponents obtained in the superconducting samples. dynamical exponent z of the superconducting samples is consistent with the theoretical predictions ( z = 1 ), while the exponent for the metallic samples is approximately 0. 7. the discrepancy in the transition behaviors supports that the disorder induced metallic phase cannot be classified to the same universality class of the superconducting ta thin films. | arxiv:1401.3947 |
the pion form factors of the qcd energy - momentum tensor ( emt ) are studied in the instanton liquid model ( ilm ) of the qcd vacuum. in this approach the breaking of conformal symmetry is encoded in the form of stronger - than - poisson fluctuations in the number of instantons. for the trace of the emt, it is shown that the gluonic trace anomaly term contributes half the pion mass, with the other half coming from the quark - mass - dependent sigma term. the $ q ^ 2 $ dependence of the form factors is governed by glueball and scalar meson exchanges. for the traceless emt, the spin - 0 and 2 form factors are computed at next - to - leading order in the instanton density using effective quark operators. relations between the gluon and quark contributions to the emt form factors are derived. the form factors are also expressed in terms of the pion light - front wave functions in the ilm. the results at the low resolution scale of the inverse instanton size are evolved to higher scales using the renormalization group equation. the ilm results compare well with those of recent lattice qcd calculations. | arxiv:2405.14026 |
it is proved that the generalized cluster complex defined by fomin and reading has a dihedral symmetry. together with diagram symmetries, they generate its automorphism group. a consequence is a simple explicit formula for the order of this automorphism group. | arxiv:2404.06945 |
language models trained on large - scale unfiltered datasets curated from the open web acquire systemic biases, prejudices, and harmful views from their training data. we present a methodology for programmatically identifying and removing harmful text from web - scale datasets. a pretrained language model is used to calculate the log - likelihood of researcher - written trigger phrases conditioned on a specific document, which is used to identify and filter documents from the dataset. we demonstrate that models trained on this filtered dataset exhibit lower propensity to generate harmful text, with a marginal decrease in performance on standard language modeling benchmarks compared to unfiltered baselines. we provide a partial explanation for this performance gap by surfacing examples of hate speech and other undesirable content from standard language modeling benchmarks. finally, we discuss the generalization of this method and how trigger phrases which reflect specific values can be used by researchers to build language models which are more closely aligned with their values. | arxiv:2108.07790 |
despite their ever more widespread deployment throughout society, machine learning algorithms remain critically vulnerable to being spoofed by subtle adversarial tampering with their input data. the prospect of near - term quantum computers being capable of running { quantum machine learning } ( qml ) algorithms has therefore generated intense interest in their adversarial vulnerability. here we show that quantum properties of qml algorithms can confer fundamental protections against such attacks, in certain scenarios guaranteeing robustness against classically - armed adversaries. we leverage tools from many - body physics to identify the quantum sources of this protection. our results offer a theoretical underpinning of recent evidence which suggest quantum advantages in the search for adversarial robustness. in particular, we prove that quantum classifiers are : ( i ) protected against weak perturbations of data drawn from the trained distribution, ( ii ) protected against local attacks if they are insufficiently scrambling, and ( iii ) protected against universal adversarial attacks if they are sufficiently quantum chaotic. our analytic results are supported by numerical evidence demonstrating the applicability of our theorems and the resulting robustness of a quantum classifier in practice. this line of inquiry constitutes a concrete pathway to advantage in qml, orthogonal to the usually sought improvements in model speed or accuracy. | arxiv:2405.10360 |
we investigate generalisations of the classical percolation critical probabilities $ p _ c $, $ p _ t $ and the critical probability $ \ tilde { p _ c } $ defined by duminil - copin and tassion ( 2015 ) to bounded degree unimodular random graphs. we further examine schramm ' s conjecture in the case of unimodular random graphs : does $ p _ c ( g _ n ) $ converge to $ p _ c ( g ) $ if $ g _ n \ to g $ in the local weak sense? among our results are the following : 1. $ p _ c = \ tilde { p _ c } $ holds for bounded degree unimodular graphs. however, there are unimodular graphs with sub - exponential volume growth and $ p _ t < p _ c $ ; i. e., the classical sharpness of phase transition does not hold. 2. we give conditions which imply $ \ lim p _ c ( g _ n ) = p _ c ( \ lim g _ n ) $. 3. there are sequences of unimodular graphs such that $ g _ n \ to g $ but $ p _ c ( g ) > \ lim p _ c ( g _ n ) $ or $ p _ c ( g ) < \ lim p _ c ( g _ n ) < 1 $. as a corollary to our positive results, we show that for any transitive graph with sub - exponential volume growth there is a sequence $ t _ n $ of large girth bi - lipschitz invariant subgraphs such that $ p _ c ( t _ n ) \ to 1 $. it remains open whether this holds whenever the transitive graph has cost 1. | arxiv:1609.07043 |
in general, deep learning - based video frame interpolation ( vfi ) methods have predominantly focused on estimating motion vectors between two input frames and warping them to the target time. while this approach has shown impressive performance for linear motion between two input frames, it exhibits limitations when dealing with occlusions and nonlinear movements. recently, generative models have been applied to vfi to address these issues. however, as vfi is not a task focused on generating plausible images, but rather on predicting accurate intermediate frames between two given frames, performance limitations still persist. in this paper, we propose a multi - in - single - out ( miso ) based vfi method that does not rely on motion vector estimation, allowing it to effectively model occlusions and nonlinear motion. additionally, we introduce a novel motion perceptual loss that enables miso - vfi to better capture the spatio - temporal correlations within the video frames. our miso - vfi method achieves state - of - the - art results on vfi benchmarks vimeo90k, middlebury, and ucf101, with a significant performance gap compared to existing approaches. | arxiv:2311.11602 |
large language models ( llms ) have been widely employed across various application domains, yet their black - box nature poses significant challenges to understanding how these models process input data internally to make predictions. in this paper, we introduce a precise and quantitative law that governs the learning of contextualized token embeddings through intermediate layers in pre - trained llms for next - token prediction. our findings reveal that each layer contributes equally to enhancing prediction accuracy, from the lowest to the highest layer - - a universal phenomenon observed across a diverse array of open - source llms, built on architectures such as transformer, rwkv, and mamba. we demonstrate that this law offers new perspectives and insights to inform and guide practices in llm development and applications, including model scaling, pre - training tasks, and information flow. overall, our law enables more fine - grained approaches to the design, training, and interpretation of llms through scrutinizing their internal data processing mechanisms. | arxiv:2408.13442 |
long prediction horizons in model predictive control ( mpc ) often prove to be efficient, however, this comes with increased computational cost. recently, a robust model predictive control ( rmpc ) method has been proposed which exploits models of different granularity. the prediction over the control horizon is split into short - term predictions with a detailed model using mpc and long - term predictions with a coarse model using rmpc. in many applications robustness is required for the short - term future, but in the long - term future, subject to major uncertainty and potential modeling difficulties, robust planning can lead to highly conservative solutions. we therefore propose combining rmpc on a detailed model for short - term predictions and stochastic mpc ( smpc ), with chance constraints, on a simplified model for long - term predictions. this yields decreased computational effort due to a simple model for long - term predictions, and less conservative solutions, as robustness is only required for short - term predictions. the effectiveness of the method is shown in a mobile robot collision avoidance simulation. | arxiv:2003.06652 |
we have obtained infrared ( 1 to 2. 5 micron ) spectroscopy for 42 halo and disk dwarfs with spectral type m1 to m6. 5. these data are compared to synthetic spectra generated by the latest model atmospheres of allard & hauschildt. photospheric parameters metallicity, effective temperature and radius are determined for the sample. we find good agreement between observation and theory except for known problems due to incomplete molecular data for metal hydrides and water. the metal - poor m subdwarfs are well matched by the models as oxide opacity sources are less important in this case. the derived effective temperatures for the sample range from 3600k to 2600k ; at these temperatures grain formation and extinction are not significant in the photosphere. the derived metallicities range from solar to one - tenth solar. the radii and effective temperatures derived agree well with recent models of low mass stars. | arxiv:astro-ph/0001100 |
coronary artery calcium ( cac ) is highly predictive of cardiovascular events. while millions of chest ct scans are performed annually in the united states, cac is not routinely quantified from scans done for non - cardiac purposes. a deep learning algorithm was developed using 446 expert segmentations to automatically quantify cac on non - contrast, non - gated ct scans ( ai - cac ). our study differs from prior works as we leverage imaging data across the veterans affairs national healthcare system, from 98 medical centers, capturing extensive heterogeneity in imaging protocols, scanners, and patients. ai - cac performance on non - gated scans was compared against clinical standard ecg - gated cac scoring. non - gated ai - cac differentiated zero vs. non - zero and less than 100 vs. 100 or greater agatston scores with accuracies of 89. 4 % ( f1 0. 93 ) and 87. 3 % ( f1 0. 89 ), respectively, in 795 patients with paired gated scans within a year of a non - gated ct scan. non - gated ai - cac was predictive of 10 - year all - cause mortality ( cac 0 vs. > 400 group : 25. 4 % vs. 60. 2 %, cox hr 3. 49, p < 0. 005 ), and composite first - time stroke, mi, or death ( cac 0 vs. > 400 group : 33. 5 % vs. 63. 8 %, cox hr 3. 00, p < 0. 005 ). in a screening dataset of 8, 052 patients with low - dose lung cancer - screening cts ( ldct ), 3, 091 / 8, 052 ( 38. 4 % ) individuals had ai - cac > 400. four cardiologists qualitatively reviewed ldct images from a random sample of > 400 ai - cac patients and verified that 527 / 531 ( 99. 2 % ) would benefit from lipid - lowering therapy. to the best of our knowledge, this is the first non - gated ct cac algorithm developed across a national healthcare system, on multiple imaging protocols, without filtering intra - cardiac hardware, and compared against a strong gated ct reference. we report superior performance relative to previous cac algorithms evaluated against paired gated scans that included patients with intra - cardiac hardware. | arxiv:2409.09968 |
we introduce the notion of domain - structured chaos and apply it to establish a connection between stochastic dynamics and deterministic chaos. | arxiv:1912.10478 |
in this work, we present a randomized coreset construction for projective clustering, which involves computing a set of $ k $ closest $ j $ - dimensional linear ( affine ) subspaces of a given set of $ n $ vectors in $ d $ dimensions. let $ a \ in \ mathbb { r } ^ { n \ times d } $ be an input matrix. an earlier deterministic coreset construction of feldman \ textit { et. al. } relied on computing the svd of $ a $. the best known algorithms for svd require $ \ min \ { nd ^ 2, n ^ 2d \ } $ time, which may not be feasible for large values of $ n $ and $ d $. we present a coreset construction by projecting the rows of matrix $ a $ on some orthonormal vectors that closely approximate the right singular vectors of $ a $. as a consequence, when the values of $ k $ and $ j $ are small, we are able to achieve a faster algorithm, as compared to the algorithm of feldman \ textit { et. al. }, while maintaining almost the same approximation. we also benefit in terms of space as well as exploit the sparsity of the input dataset. another advantage of our approach is that it can be constructed in a streaming setting quite efficiently. | arxiv:1606.07992 |
the present work builds on previous investigations of the authors ( and their collaborators ) regarding bridges, a certain type of morphisms between encryption schemes, making a step forward in developing a ( category theory ) language for studying relations between encryption schemes. here we analyse the conditions under which bridges can be performed sequentially, formalizing the notion of composability. one of our results gives a sufficient condition for a pair of bridges to be composable. we illustrate that composing two bridges, each independently satisfying a previously established ind - cpa security definition, can actually lead to an insecure bridge. our main result gives a sufficient condition that a pair of secure composable bridges should satisfy in order for their composition to be a secure bridge. we also introduce the concept of a complete bridge and show that it is connected to the notion of fully composable homomorphic encryption ( fche ), recently considered by micciancio. moreover, we show that a result of micciancio which gives a construction of fche schemes can be phrased in the language of complete bridges, where his insights can be formalised in a greater generality. | arxiv:2305.16435 |
in this letter, we investigate a quite recent new class of spin one - half fermions, namely \ emph { ahluwalia class - 7 spinors }, endowed with mass dimensionality $ 1 $ rather than $ 3 / 2 $, being candidates to describe dark matter. such spinors, under the dirac adjoint structure, belongs to the lounesto ' s class - 6, namely dipole spinors. up to our knowledge, dipole spinor fields have weyl spinor fields as their most known representative, nonetheless, here we explore the \ emph { dark } counterpart of the dipole spinors, which represents eigenspinors of the chirality operator. | arxiv:2009.08318 |
we present an approach to perform 3d pose estimation of multiple people from a few calibrated camera views. our architecture, leveraging the recently proposed unprojection layer, aggregates feature - maps from a 2d pose estimator backbone into a comprehensive representation of the 3d scene. such intermediate representation is then elaborated by a fully - convolutional volumetric network and a decoding stage to extract 3d skeletons with sub - voxel accuracy. our method achieves state of the art mpjpe on the cmu panoptic dataset using a few unseen views and obtains competitive results even with a single input view. we also assess the transfer learning capabilities of the model by testing it against the publicly available shelf dataset obtaining good performance metrics. the proposed method is inherently efficient : as a pure bottom - up approach, it is computationally independent of the number of people in the scene. furthermore, even though the computational burden of the 2d part scales linearly with the number of input views, the overall architecture is able to exploit a very lightweight 2d backbone which is orders of magnitude faster than the volumetric counterpart, resulting in fast inference time. the system can run at 6 fps, processing up to 10 camera views on a single 1080ti gpu. | arxiv:2004.02688 |
a microscopic theory of the electrical conductivity $ \ sigma ( \ omega ) $ within the t - j model is developed. an exact representation for $ \ sigma ( \ omega ) $ is obtained using the memory - function technique for the relaxation function in terms of the hubbard operators, and the generalized drude law is derived. the relaxation rate due to the decay of charge excitations into particle - hole pairs assisted by antiferromagnetic spin fluctuations is calculated in the mode - coupling approximation. using results for the spectral function of spin excitations calculated previously, the relaxation rate and the optical and dc conductivities are calculated in a broad region of doping and temperatures. the reasonable agreement of the theory with experimental data for cuprates proves the important role of spin - fluctuation scattering in the charge dynamics. | arxiv:1206.4474 |
the schwarzschild, schwarzschild - ads, and schwarzschild - de sitter solutions all admit freely acting discrete involutions which commute with the continuous symmetries of the spacetimes. intuitively, these involutions correspond to the antipodal map of the corresponding spacetimes. in analogy with the ordinary de sitter example, this allows us to construct new vacua by performing a mottola - allen transform on the modes associated with the hartle - hawking, or euclidean, vacuum. these vacua are the ` alpha ' - vacua for these black holes. the causal structure of a typical black hole may ameliorate certain difficulties which are encountered in the case of de sitter alpha - vacua. for schwarzschild - ads black holes, a bogoliubov transformation which mixes operators of the two boundary cft ' s provides a construction of the dual cft alpha - states. finally, we analyze the thermal properties of these vacua. | arxiv:hep-th/0610133 |
language is a method by which individuals express their thoughts. each language has its own set of alphabetic and numeric characters. people can communicate with one another through either oral or written communication. however, each language has a sign language counterpart. individuals who are deaf and / or mute communicate through sign language. the bangla language also has a sign language, which is called bdsl. the dataset is about bangla hand sign images. the collection contains 49 individual bangla alphabet images in sign language. bdsl49 is a dataset that consists of 29, 490 images with 49 labels. images of 14 different adult individuals, each with a distinct background and appearance, have been recorded during data collection. several strategies have been used to eliminate noise from datasets during preparation. this dataset is available to researchers for free. they can develop automated systems using machine learning, computer vision, and deep learning techniques. in addition, two models were used in this dataset. the first is for detection, while the second is for recognition. | arxiv:2208.06827 |
in this paper, we study the various ways 3rd - 5th grade educators in wisconsin utilized jo wilder and the capitol case, a historical inquiry game, as part of their classroom instruction. the 15 educators involved in the study were all grade school teachers in wisconsin who took part in the " doing history fellowship " program, a professional development opportunity offered by the authors, designed to increase their understanding of historical inquiry instruction and game - based learning. as part of the program, the educators planned and implemented the game within their own classroom context and reported their results back to the authors and other educators. through their reports, surveys and semi - structured interviews we discovered the educators were motivated by five distinct instructional purposes, which influenced how the game was integrated into their curriculum. in this paper, we name and describe these five purposes. we see these findings as useful insights into how educators think about games and how educational video games and corresponding professional development activities may be designed in the future. | arxiv:2210.09433 |
automatic identification of proper image frames at the end - diastolic ( ed ) and end - systolic ( es ) frames during the review of invasive coronary angiograms ( ica ) is important to assess blood flow during a cardiac cycle, reconstruct the 3d arterial anatomy from bi - planar views, and generate the complementary fusion map with myocardial images. the current identification method primarily relies on visual interpretation, making it not only time - consuming but also less reproducible. in this paper, we propose a new method to automatically identify angiographic image frames associated with the ed and es cardiac phases by using the trajectories of key vessel points ( i. e. landmarks ). more specifically, a detection algorithm is first used to detect the key points of coronary arteries, and then an optical flow method is employed to track the trajectories of the selected key points. the ed and es frames are identified based on all these trajectories. our method was tested with 62 ica videos from two separate medical centers ( 22 and 9 patients in sites 1 and 2, respectively ). comparing consensus interpretations by two human expert readers, excellent agreement was achieved by the proposed algorithm : the agreement rates within a one - frame range were 92. 99 % and 92. 73 % for the automatic identification of the ed and es image frames, respectively. in conclusion, the proposed automated method showed great potential for being an integral part of automated ica image analysis. | arxiv:2110.02844 |
this report contains the description of two novel job shop scheduling benchmarks that resemble instances of real scheduling problem as they appear in industry. in particular, the aim was to provide large - scale benchmarks ( up to 1 million operations ) to test the state - of - the - art scheduling solutions on problems that are closer to what occurs in a real industrial context. the first benchmark is an extension of the well known taillard benchmark ( 1992 ), while the second is a collection of scheduling instances with a known - optimum solution. | arxiv:2102.08778 |
star formation in the universe ' s largest galaxies - - - the ones at the centers of galaxy clusters - - - depends critically on the thermodynamic state of their hot gaseous atmospheres. central galaxies with low - entropy, high - density atmospheres frequently contain multiphase star - forming gas, while those with high - entropy, low - density atmospheres never do. the dividing line between these two populations in central entropy, and therefore central cooling time, is amazingly sharp. two hypotheses have been proposed to explain the dichotomy. one points out that thermal conduction can prevent radiative cooling of cluster cores above the dividing line. the other holds that cores below the dividing line are subject to thermal instability that fuels the central agn through a cold - feedback mechanism. here we explore those hypotheses with an analysis of the h - alpha properties of accept galaxy clusters. we find that the two hypotheses are likely to be complementary. our results support a picture in which cold clouds inevitably precipitate out of cluster cores in which cooling outcompetes thermal conduction and rain down on the central black hole, causing agn feedback that stabilizes the cluster core. in particular, the observed distribution of the cooling - time to freefall - time ratio is nearly identical to that seen in simulations of this cold - feedback process, implying that cold - phase accretion, and not bondi - like accretion of hot - phase gas, is responsible for the agn feedback that regulates star formation in large galaxies. | arxiv:1409.1601 |
we study the problem of learning from positive and unlabeled ( pu ) data in the federated setting, where each client only labels a little part of their dataset due to the limitation of resources and time. different from the settings in traditional pu learning where the negative class consists of a single class, the negative samples which cannot be identified by a client in the federated setting may come from multiple classes which are unknown to the client. therefore, existing pu learning methods can be hardly applied in this situation. to address this problem, we propose a novel framework, namely federated learning with positive and unlabeled data ( fedpu ), to minimize the expected risk of multiple negative classes by leveraging the labeled data in other clients. we theoretically analyze the generalization bound of the proposed fedpu. empirical experiments show that the fedpu can achieve much better performance than conventional supervised and semi - supervised federated learning methods. code is available at https : / / github. com / littlesunlxy / fedpu - torch | arxiv:2106.10904 |
we formulate a set of equations that facilitate an exact numerical solution of the kohn - sham potential for a finite hubbard chain with nearest neighbour hopping and arbitrary site potentials. the approach relies on a mapping of the non - interacting kohn - sham ground state wave function onto the exact interacting system wavefunction and two interconnected self - consistent cycles. the self - consistent cycles are performed within the framework of the kohn - sham non - interacting system without any direct reference to the interacting system. the first self - consistent cycle updates the mapping of the non - interacting wavefunction onto the interacting wavefunction based on a trial input density, while the second self - consistent cycle updates the kohn - sham potential to yield the trial density. at the solution point, the exact density, the exact kohn - sham potential, the density functional correlation energy and the exact interacting system ground state energy are available. | arxiv:1810.10442 |
margin trading in which investors purchase shares with money borrowed from brokers is blamed to be a major cause of the 2015 chinese stock market crash. we propose a cascading failure model and examine how an increase in margin trading increases share price vulnerability. the model is based on a bipartite graph of investors and shares that includes four margin trading factors, ( i ) initial margin $ k $, ( ii ) minimum maintenance $ r $, ( iii ) volatility $ v $, and ( iv ) diversity $ s $. we use our model to simulate margin trading and observe how the share prices are affected by these four factors. the experimental results indicate that a stock market can be either vulnerable or stable. a stock market is vulnerable when an external shock can cause a cascading failure of its share prices. it is stable when its share prices are resilient to external shocks. furthermore, we investigate how the cascading failure of share price is affected by these four factors, and find that by increasing $ v $ and $ r $ or decreasing $ k $ we increase the probability that the stock market will experience a phase transition from stable to vulnerable. it is also found that increasing $ s $ decreases resilience and increases systematic risk. these findings could be useful to regulators supervising margin trading activities. | arxiv:1804.07352 |
we show that random walk on a stationary random graph with positive anchored expansion and exponential volume growth has positive speed. we also show that two families of random triangulations of the hyperbolic plane, the hyperbolic poisson voronoi tessellation and the hyperbolic poisson delaunay triangulation, have 1 - skeletons with positive anchored expansion. as a consequence, we show that the simple random walks on these graphs have positive speed. we include a section of open problems and conjectures on the topics of stationary geometric random graphs and the hyperbolic poisson voronoi tessellation. | arxiv:1409.4312 |
in this paper, we prove new relations between the bias of multilinear forms, the correlation between multilinear forms and lower degree polynomials, and the rank of tensors over $ gf ( 2 ) = \ { 0, 1 \ } $. we show the following results for multilinear forms and tensors. 1. correlation bounds : we show that a random $ d $ - linear form has exponentially low correlation with low - degree polynomials. more precisely, for $ d \ ll 2 ^ { o ( k ) } $, we show that a random $ d $ - linear form $ f ( x _ 1, x _ 2, \ dots, x _ d ) : \ left ( gf ( 2 ) ^ { k } \ right ) ^ d \ rightarrow gf ( 2 ) $ has correlation $ 2 ^ { - k ( 1 - o ( 1 ) ) } $ with any polynomial of degree at most $ d / 10 $. this result is proved by giving near - optimal bounds on the bias of random $ d $ - linear form, which is in turn proved by giving near - optimal bounds on the probability that a random rank - $ t $ $ d $ - linear form is identically zero. 2. tensor - rank vs bias : we show that if a $ d $ - dimensional tensor has small rank, then the bias of the associated $ d $ - linear form is large. more precisely, given any $ d $ - dimensional tensor $ $ t : \ underbrace { [ k ] \ times \ ldots [ k ] } _ { \ text { $ d $ times } } \ to gf ( 2 ) $ $ of rank at most $ t $, the bias of the associated $ d $ - linear form $ $ f _ t ( x _ 1, \ ldots, x _ d ) : = \ sum _ { ( i _ 1, \ dots, i _ d ) \ in [ k ] ^ d } t ( i _ 1, i _ 2, \ ldots, i _ d ) x _ { 1, i _ 1 } \ cdot x _ { 1, i _ 2 } \ cdots x _ { d, i _ d } $ $ is at least $ \ left ( 1 - \ frac1 { 2 ^ { d - 1 } } \ right ) ^ t $. the above bias vs tensor - rank connection suggests a natural approach to proving nontrivial tensor - rank lower bounds for | arxiv:1804.09124 |
we present an analysis of the relative abundance features of a number of chemical elements in the atmospheres of metal - rich ( $ \ rm { [ fe / h ] } > - 1. 0 $ ) galactic - field rr ~ lyrae variable stars and the kinematic characteristics of these stars. we have previously shown that the relative abundances of some $ \ alpha $ - elements : magnesium, silicon, calcium, and to a greater extent of titanium, as well as yttrium and scandium in such stars are lower than in most of other types of stars, bearing similar metallicity. it is found here that some of these metal - rich rr ~ lyrae stars also have very low relative abundances of sodium, aluminum and nickel. the orbital parameters of all the metal - rich rr ~ lyrae variables studied in this paper are typical of the galactic thin or thick disk objects, however, unusual chemical composition let us to suggests a possible extragalactic origin for some of them. | arxiv:2408.03107 |
quantifying complexity in quantum systems has witnessed a surge of interest in recent years, with krylov - based measures such as krylov complexity ( $ c _ k $ ) and spread complexity ( $ c _ s $ ) gaining prominence. in this study, we investigate their interplay by considering the complexity of states represented by density matrix operators. after setting up the problem, we analyze a handful of analytical and numerical examples spanning generic two - dimensional hilbert spaces, qubit states, quantum harmonic oscillators, and random matrix theories, uncovering insightful relationships. for generic pure states, our analysis reveals two key findings : ( i ) a correspondence between moment - generating functions ( of lanczos coefficients ) and survival amplitudes, and ( ii ) an early - time equivalence between $ c _ k $ and $ 2c _ s $. furthermore, for maximally entangled pure states, we find that the moment - generating function of $ c _ k $ becomes the spectral form factor and, at late - times, $ c _ k $ is simply related to $ nc _ s $ for $ n \ geq2 $ within the $ n $ - dimensional hilbert space. notably, we confirm that $ c _ k = 2c _ s $ holds across all times when $ n = 2 $. through the lens of random matrix theories, we also discuss deviations between complexities at intermediate times and highlight subtleties in the averaging approach at the level of the survival amplitude. | arxiv:2402.09522 |
in this paper, we obtain some simpson type inequalities for functions whose second derivatives absolute value or q - th power of them are q - class functions. also we give applications to numerical integration. | arxiv:1207.2435 |
by taking the virtual inter - band transitions along with the intra - band ones into full account, here we first propose an effective band mass theorem that is suitable for a wide - class of single - particle hamiltonians exhibiting multiple energy bands. then, for the special case of two - band systems, we show that the inter - band contribution to the effective band mass of a particle at a given quantum state is directly controlled by the quantum metric of the corresponding state. as an illustration, we consider a spin - orbit coupled spin - $ 1 / 2 $ particle and calculate its effective band mass at the band minimum of the lower helicity band. independent of the coupling strength, we find that the bare mass $ m _ 0 $ of the particle jumps to $ 2m _ 0 $ for the rashba and to $ 3m _ 0 $ for the weyl coupling. this geometric mass enhancement is a non - perturbative effect, uncovering the mystery behind the effective mass of the two - body bound states in the non - interacting limit. as a further illustration, we show that a massless dirac particle acquires a linearly dispersing band mass ( equivalent to the effective cyclotron one up to a prefactor ) with its momentum through the same mechanism. | arxiv:1803.04176 |
we have studied the force in mesoscopic wires in the presence of an external magnetic field along the wire using a free electron model. we show that the applied magnetic field can be used to affect the force in the wire. the magnetic field breaks the degeneracy of the eigenenergies of the conduction modes, resulting in more structure in the force as a function of wire length. the use of an external magnetic field is an equilibrium method to control the number of transporting channels. under the least favorable circumstances ( on the middle of a low conduction step ) one needs about 1. 3 t, for a mesoscopic bismuth wire, to see an abrupt change in the force, at fixed wire length. | arxiv:cond-mat/9908466 |
we consider a classical and possibly driven composite system $ x \ otimes y $ weakly coupled to a markovian thermal reservoir $ r $ so that an unambiguous stochastic thermodynamics ensues for $ x \ otimes y $. this setup can be equivalently seen as a system $ x $ strongly coupled to a non - markovian reservoir $ y \ otimes r $. we demonstrate that only in the limit where the dynamics of $ y $ is much faster then $ x $, our unambiguous expressions for thermodynamic quantities such as heat, entropy or internal energy, are equivalent to the strong coupling expressions recently obtained in the literature using the hamiltonian of mean force. by doing so, we also significantly extend these results by formulating them at the level of instantaneous rates and by allowing for time - dependent couplings between $ x $ and its environment. away from the limit where $ y $ evolves much faster than $ x $, previous approaches fail to reproduce the correct results from the original unambiguous formulation, as we illustrate numerically for an underdamped brownian particle coupled strongly to a non - markovian reservoir. | arxiv:1703.05098 |
since the first detection of gravitational - wave ( gw ), gw150914, september 14th 2015, the multi - messenger astronomy added a new way of observing the universe together with electromagnetic ( em ) waves and neutrinos. after two years, gw together with its em counterpart from binary neutron stars, gw170817 and grb170817a, has been observed. the detection of gws opened a new window of astronomy / astrophysics and will be an important messenger to understand the universe. in this article, we briefly review the gravitational - wave and the astrophysical sources and introduce the basic principle of the laser interferometer as a gravitational - wave detector and its noise sources to understand how the gravitational - waves are detected in the laser interferometer. finally, we summarize the search algorithms currently used in the gravitational - wave observatories and the detector characterization algorithms used to suppress noises and to monitor data quality in order to improve the reach of the astrophysical searches. | arxiv:1806.08912 |
in 1977 john tukey described how in exploratory data analysis, data analysts use tools, such as data visualizations, to separate their expectations from what they observe. in contrast to statistical theory, an underappreciated aspect of data analysis is that a data analyst must make decisions by comparing the observed data or output from a statistical tool to what the analyst previously expected from the data. however, there is little formal guidance for how to make these data analytic decisions as statistical theory generally omits a discussion of who is using these statistical methods. in this paper, we propose a model for the iterative process of data analysis based on the analyst ' s expectations, using what we refer to as expected and anomaly probabilistic outcome sets, and the concept of statistical information gain. here, we extend the basic idea of comparing an analyst ' s expectations to what is observed in a data visualization to more general analytic situations. our model posits that the analyst ' s goal is to increase the amount of information the analyst has relative to what the analyst already knows, through successive analytic iterations. we introduce two criteria - - expected information gain and anomaly information gain - - to provide guidance about analytic decision - making and ultimately to improve the practice of data analysis. finally, we show how our framework can be used to characterize common situations in practical data analysis. | arxiv:2309.08494 |
an isolated hi cloud with peculiar properties has recently been discovered by dedes, dedes, & kalberla ( 2008, a & a, 491, l45 ) with the 300 - m arecibo telescope, and subsequently imaged with the vla. it has an angular size of ~ 6 ', and the hi emission has a narrow line profile of width ~ 3 km / s. we explore the possibility that this cloud could be associated with a circumstellar envelope ejected by an evolved star. observations were made in the rotational lines of co with the iram - 30m telescope, on three positions in the cloud, and a total - power mapping in the hi line was obtained with the nancay radio telescope. co was not detected and seems too underabundant in this cloud to be a classical late - type star circumstellar envelope. on the other hand, the hi emission is compatible with the detached - shell model that we developed for representing the external environments of agb stars. we propose that this cloud could be a fossil circumstellar shell left over from a system that is now in a post - planetary - nebula phase. nevertheless, we cannot rule out that it is a galactic cloud or a member of the local group, although the narrow line profile would be atypical in both cases. | arxiv:0904.2299 |
we propose the supervised hierarchical dirichlet process ( shdp ), a nonparametric generative model for the joint distribution of a group of observations and a response variable directly associated with that whole group. we compare the shdp with another leading method for regression on grouped data, the supervised latent dirichlet allocation ( slda ) model. we evaluate our method on two real - world classification problems and two real - world regression problems. bayesian nonparametric regression models based on the dirichlet process, such as the dirichlet process - generalised linear models ( dp - glm ) have previously been explored ; these models allow flexibility in modelling nonlinear relationships. however, until now, hierarchical dirichlet process ( hdp ) mixtures have not seen significant use in supervised problems with grouped data since a straightforward application of the hdp on the grouped data results in learnt clusters that are not predictive of the responses. the shdp solves this problem by allowing for clusters to be learnt jointly from the group structure and from the label assigned to each group. | arxiv:1412.5236 |
avanzi et al. ( 2016 ) recently studied an optimal dividend problem where dividends are paid both periodically and continuously with different transaction costs. in the brownian model with poissonian periodic dividend payment opportunities, they showed that the optimal strategy is either of the pure - continuous, pure - periodic, or hybrid - barrier type. in this paper, we generalize the results of their previous study to the dual ( spectrally positive l \ ' evy ) model. the optimal strategy is again of the hybrid - barrier type and can be concisely expressed using the scale function. these results are confirmed through a sequence of numerical experiments. | arxiv:1612.02444 |
the advancement of insect - computer hybrid robots holds significant promise for navigating complex terrains and enhancing robotics applications. this study introduced an automatic assembly method for insect - computer hybrid robots, which was accomplished by mounting backpack with precise implantation of custom - designed bipolar electrodes. we developed a stimulation protocol for the intersegmental membrane between pronotum and mesothorax of the madagascar hissing cockroach, allowing for bipolar electrodes ' automatic implantation using a robotic arm. the assembly process was integrated with a deep learning - based vision system to accurately identify the implantation site, and a dedicated structure to fix the insect ( 68 s for the whole assembly process ). the automatically assembled hybrid robots demonstrated steering control ( over 70 degrees for 0. 4 s stimulation ) and deceleration control ( 68. 2 % speed reduction for 0. 4 s stimulation ), matching the performance of manually assembled systems. furthermore, a multi - agent system consisting of 4 hybrid robots successfully covered obstructed outdoor terrain ( 80. 25 % for 10 minutes 31 seconds ), highlighting the feasibility of mass - producing these systems for practical applications. the proposed automatic assembly strategy reduced preparation time for the insect - computer hybrid robots while maintaining their precise control, laying a foundation for scalable production and deployment in real - world applications. | arxiv:2411.13164 |
we introduce a novel paradigm for offline video instance segmentation ( vis ), based on the hypothesis that explicit object - oriented information can be a strong clue for understanding the context of the entire sequence. to this end, we propose vita, a simple structure built on top of an off - the - shelf transformer - based image instance segmentation model. specifically, we use an image object detector as a means of distilling object - specific contexts into object tokens. vita accomplishes video - level understanding by associating frame - level object tokens without using spatio - temporal backbone features. by effectively building relationships between objects using the condensed information, vita achieves the state - of - the - art on vis benchmarks with a resnet - 50 backbone : 49. 8 ap, 45. 7 ap on youtube - vis 2019 & 2021, and 19. 6 ap on ovis. moreover, thanks to its object token - based structure that is disjoint from the backbone features, vita shows several practical advantages that previous offline vis methods have not explored - handling long and high - resolution videos with a common gpu, and freezing a frame - level detector trained on image domain. code is available at https : / / github. com / sukjunhwang / vita. | arxiv:2206.04403 |
we present the conservative effective two - body hamiltonian at the third order in the post - newtonian expansion with gravitoelectric quadrupolar dynamical tidal - interactions. our derivation of the effective two - body lagrangian is based on the diagrammatic effective field theory approach and it involves feynman integrals up to three loops, which are evaluated within the dimensional regularization scheme. the elimination of the divergent terms occurring in the effective lagrangian requires the addition of counterterms to ensure finite observables, thereby introducing a renormalization group flow to the post - adiabatic love number. as a limiting case of the renormalized dynamical effective hamiltonian, we also derive the effective hamiltonian for adiabatic tides, and, in this regime, calculate the binding energy for a circular orbit, and the scattering angle in a hyperbolic scattering. | arxiv:2308.01865 |
asymmetric numeral systems ( ans ) is a class of entropy encoders that had an immense impact on the data compression, substituting arithmetic and huffman coding. it was studied by different authors but the precise asymptotics of its redundancy ( in relation to the entropy ) was not completely understood. we obtain optimal bounds for the redundancy of the tabled ans ( tans ), the most popular ans variant. given a sequence $ a _ 1, a _ 2, \ ldots, a _ n $ of symbols from an alphabet $ \ { 0, 1, \ ldots, \ sigma - 1 \ } $ such that each symbol $ a $ occurs in it $ f _ a $ times and $ n = 2 ^ r $, the tans encoder using duda ' s ` ` precise initialization ' ' to fill tans tables transforms this sequence into a bit string of the following length ( the frequencies are not included in the encoding ) : $ \ sum \ limits _ { a \ in [ 0.. \ sigma ) } f _ a \ cdot \ log \ frac { n } { f _ a } + o ( \ sigma + r ) $, where $ o ( \ sigma + r ) $ can be bounded by $ \ sigma \ log e + r $. the $ r $ - bit term is an artifact indispensable to ans ; the rest incurs a redundancy of $ o ( \ frac { \ sigma } { n } ) $ bits per symbol. we complement this by examples showing that an $ \ omega ( \ sigma + r ) $ redundancy is necessary. we argue that similar examples exist for most adequate initialization methods for tans. thus, we refute duda ' s conjecture that the redundancy is $ o ( \ frac { \ sigma } { n ^ 2 } ) $ bits per symbol. we also propose a variant of the range ans ( rans ), called rans with fixed accuracy, parameterized by $ k \ ge 1 $. in this variant the integer division, which is unavoidable in rans, is performed only when its result belongs to $ [ 2 ^ k.. 2 ^ { k + 1 } ) $. therefore, the division can be computed by faster methods provided $ k $ is small. we bound the redundancy for our rans variant by $ \ frac { n } { | arxiv:2201.02514 |
asymmetric electrical conductance is theoretically demonstrated on the surface of a topological insulator ( ti ) in the limit of infinitesimally small forward and reverse biases between two spin selective electrodes. the discontinuous behavior relies on the spin - momentum interlocked nature of ti surface electrons together with the resulting imbalance in the coupling coefficients between the electrodes and ti surface states. the analysis is based on a transmission matrix model that, in combination with a phenomenological treatment for the diffusive limit, accounts for both ballistic and scattered paths simultaneously. with the estimated conductance asymmetry over a factor of 10, implementation in the ratchet - like applications and low - voltage rectification circuits appears practicable. | arxiv:1509.04406 |
large language models ( llms ) have shown remarkable abilities across various tasks, yet their development has predominantly centered on high - resource languages like english and chinese, leaving low - resource languages underserved. to address this disparity, we present seallms 3, the latest iteration of the seallms model family, tailored for southeast asian languages. this region, characterized by its rich linguistic diversity, has lacked adequate language technology support. seallms 3 aims to bridge this gap by covering a comprehensive range of languages spoken in this region, including english, chinese, indonesian, vietnamese, thai, tagalog, malay, burmese, khmer, lao, tamil, and javanese. leveraging efficient language enhancement techniques and a specially constructed instruction tuning dataset, seallms 3 significantly reduces training costs while maintaining high performance and versatility. our model excels in tasks such as world knowledge, mathematical reasoning, translation, and instruction following, achieving state - of - the - art performance among similarly sized models. additionally, we prioritized safety and reliability by addressing both general and culture - specific considerations and incorporated mechanisms to reduce hallucinations. this work underscores the importance of inclusive ai, showing that advanced llm capabilities can benefit underserved linguistic and cultural communities. | arxiv:2407.19672 |
we have applied a relativistic tolman - bondi model of the virgo cluster to a sample of 183 galaxies with measured distances within a radius of 8 degrees from m87. we find that the sample is significantly contaminated by background galaxies which lead to too large a cluster mean distance if not excluded. the tolman - bondi model predictions, together with the hi deficiency of spiral galaxies, allows one to identify these background galaxies. one such galaxy is clearly identified among the 6 calibrating galaxies with cepheid distances. as the tolman - bondi model predicts the expected distance ratio to the virgo distance, this galaxy can still be used to estimate the virgo distance, and the average value over the 6 galaxies is 15. 4 + - 0. 5 mpc. well - known background groups of galaxies are clearly recovered, together with filaments of galaxies which link these groups to the main cluster, and are falling into it. no foreground galaxy is clearly detected in our sample. applying the b - band tully - fisher method to a sample of 51 true members of the virgo cluster according to our classification gives a cluster distance of 18. 0 + - 1. 2 mpc, larger than the mean cepheid distance. finally, the same model is used to estimate the virgo cluster mass, which is m = 1. 2 10 ^ { 15 } msun within 8 degrees from the cluster center ( 2. 2 mpc radius ), and amounts to 1. 7 virial mass. | arxiv:astro-ph/0106261 |
we show that, due to the weak ferromagnetism of la $ _ { 2 - x } $ sr $ _ x $ cuo $ _ 4 $, an external magnetic field leads to a dimensional crossover 2d $ \ to $ 3d for the in - plane transport. the crossover results in an increase of the hole ' s localization length and hence in a dramatic negative magnetoresistance in the variable range hopping regime. this mechanism quantitatively explains puzzling experimental data on the negative magnetoresistance in the n \ ' eel phase of la $ _ { 2 - x } $ sr $ _ x $ cuo $ _ 4 $. | arxiv:cond-mat/0610818 |
in this paper, the author discusses the eigenvalues and entropies under the harmonic - ricci flow, which is the ricci flow coupled with the harmonic map flow. we give an alternative proof of results for compact steady and expanding harmonic - ricci breathers. in the second part, we derive some monotonicity formulas for eigenvalues of laplacian under the harmonic - ricci flow. finally, we obtain the first variation of the shrinker and expanding entropies of the harmonic - ricci flow. | arxiv:1011.1697 |
nonlinear optical ( nlo ) imaging has emerged as a promising plant cell imaging technique due to its large optical penetration, inherent 3d spatial resolution, and reduced photodamage, meanwhile exogenous nanoprobes are usually needed for non - signal target cell analysis. here, we report in - vivo, simultaneous 3d labeling and imaging of potato cell structures using plasmonic nanoprobe - assisted multimodal nlo microscopy. experimental results show that the complete cell structure could be imaged by the combination of second - harmonic generation ( shg ) and two - photon luminescence ( tpl ) when noble metal silver or gold ions are added. in contrast, without noble metal ion solution, no nlo signals from the cell wall could be acquired. the mechanism can be attributed to noble metal nanoprobes with strong nonlinear optical responses formed along the cell walls via a femtosecond laser scan. during the shg - tpl imaging process, noble metal ions that cross the cell wall could be rapidly reduced to plasmonic nanoparticles by fs laser and selectively anchored onto both sides of the cell wall, thereby leading to simultaneous 3d labeling and imaging of potato cells. compared with traditional labeling technique that needs in - vitro nanoprobe fabrication and cell labeling, our approach allows for one - step, in - vivo labeling of plant cells, thus providing a rapid, cost - effective way for cellular structure construction and imaging. | arxiv:2308.11211 |
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