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open - domain question answering can be formulated as a phrase retrieval problem, in which we can expect huge scalability and speed benefit but often suffer from low accuracy due to the limitation of existing phrase representation models. in this paper, we aim to improve the quality of each phrase embedding by augmenting it with a contextualized sparse representation ( sparc ). unlike previous sparse vectors that are term - frequency - based ( e. g., tf - idf ) or directly learned ( only few thousand dimensions ), we leverage rectified self - attention to indirectly learn sparse vectors in n - gram vocabulary space. by augmenting the previous phrase retrieval model ( seo et al., 2019 ) with sparc, we show 4 % + improvement in curatedtrec and squad - open. our curatedtrec score is even better than the best known retrieve & read model with at least 45x faster inference speed.
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arxiv:1911.02896
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the microservices paradigm aims at changing the way in which software is perceived, conceived and designed. one of the foundational characteristics of this new promising paradigm, compared for instance to monolithic architectures, is scalability. in this paper, we present a real world case study in order to demonstrate how scalability is positively affected by re - implementing a monolithic architecture into microservices. the case study is based on the fx core system, a mission critical system of danske bank, the largest bank in denmark and one of the leading financial institutions in northern europe.
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arxiv:1704.04173
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recent trends in communication networks have focused on quality of service ( qos ) requirements expressed through timing metrics such as latency or age of information ( aoi ). a possible way to achieve this is coded multipath communication : redundancy is added to a block of information through a robust packet - level code, transmitting across multiple independent channels to reduce the impact of blockages or rate fluctuation. the number of these links can grow significantly over traditional two - path schemes : in these scenarios, the optimization of the timing metrics is non - trivial, and latency and aoi might require different settings. in particular, packet preemption is often the optimal solution to optimize aoi in uncoded communication, but can significantly reduce the reliability of individual blocks. in this work, we model the multipath communication as a fork - join d / m / ( k, n ) / l queue, where k blocks of information are encoded into n > k redundant blocks. we derive the latency and peak aoi ( paoi ) distributions for different values of the queue size l. our results show that preemption is not always the optimal choice, as dropping a late packet on one path might affect the reliability of the whole block, and that minimizing the paoi leads to poor latency performance.
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arxiv:2302.07562
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let $ \ lambda $ be a complex number in the closed unit disc $ \ overline { \ bbb d } $, and $ \ cal h $ be a separable hilbert space with the orthonormal basis, say, $ { \ cal e } = \ { e _ n : n = 0, 1, 2, \ cdots \ } $. a bounded operator $ t $ on $ \ cal h $ is called a $ \ lambda $ - toeplitz operator if $ $ \ langle te _ { m + 1 }, e _ { n + 1 } \ rangle = \ lambda \ langle te _ m, e _ n \ rangle $ $ ( where $ \ langle \ cdot, \ cdot \ rangle $ is the inner product on $ \ cal h $ ). the subject arises naturally from a special case of the operator equation \ [ s ^ * as = \ lambda a + b, \ \ mbox { where $ s $ is a shift on $ \ cal h $ }, \ ] which plays an essential role in finding bounded matrix $ ( a _ { ij } ) $ on $ l ^ 2 ( \ bbb z ) $ that solves the system of equations $ $ \ left \ { \ begin { array } { lcc } a _ { 2i, 2j } & = & p _ { ij } + aa _ { ij } \ \ a _ { 2i, 2j - 1 } & = & q _ { ij } + ba _ { ij } \ \ a _ { 2i - 1, 2j } & = & v _ { ij } + ca _ { ij } \ \ a _ { 2i - 1, 2j - 1 } & = & w _ { ij } + da _ { ij } \ end { array } \ right. $ $ for all $ i, j \ in \ bbb z $, where $ ( p _ { ij } ) $, $ ( q _ { ij } ) $, $ ( v _ { ij } ) $, $ ( w _ { ij } ) $ are bounded matrices on $ l ^ 2 ( \ bbb z ) $ and $ a, b, c, d \ in \ bbb c $. it is also clear that the well - known toeplitz operators are precisely the solutions of $ s ^ * as = a $
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arxiv:1404.2700
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we present the theory of the dirichlet problem for nonlocal operators which are the generators of general pure - jump symmetric l \ ' evy processes whose l \ ' evy measures need not be absolutely continuous. we establish basic facts about the sobolev spaces for such operators, in particular we prove the existence and uniqueness of weak solutions. we present strong and weak variants of maximum principle, and l ^ \ infty bounds for solutions. we also discuss the related extension problem in c ^ { 1, 1 } domains.
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arxiv:1702.01054
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recently, a new parameterization of the gogny interaction suitable for astrophysical applications, named d1m *, has been presented. we investigate the possible existence of spurious finite - size instabilities of this new gogny force by repeating a study that we have already performed for the most commonly used parameterizations ( d1, d1s, d1n, d1m ) of the gogny force. this study is based on a fully - antisymmetrized random phase approximation ( rpa ) calculation of the nuclear matter response functions employing the continued fraction technique. it turns out that this new gogny interaction is affected by spurious finite - size instabilities in the scalar isovector channel ; hence, unphysical results are expected in the calculation of properties of nuclei, like neutron and proton densities, if this d1m * force is used. the conclusions from this study are then, for the first time, tested against mean - field calculations in a coordinate representation for several nuclei. unphysical results for several nuclei are also obtained with the d1n parameterization of the gogny force. these observations strongly advocate for the use of the linear response formalism to detect and avoid finite - size instabilities during the fit of the parameters of gogny interactions as it is already done for some skyrme forces.
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arxiv:1806.02080
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in this paper, the fully corrective forward greedy selection - cross validation - based ( fcfgs - cv - based ) channel estimator is proposed for wideband millimeter wave ( mmwave ) massive multiple - input multiple - output ( mimo ) systems with low - resolution analog - to - digital converters ( adcs ). the sparse nature of the mmwave virtual channel in the angular and delay domains is exploited to convert the maximum a posteriori ( map ) channel estimation problem to an optimization problem with a concave objective function and sparsity constraint. the fcfgs algorithm, which is the generalized orthogonal matching pursuit ( omp ) algorithm, is used to solve the sparsity - constrained optimization problem. furthermore, the cv technique is adopted to determine the proper termination condition by detecting overfitting when the sparsity level is unknown.
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arxiv:1908.00532
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there are two parts to this work : first, we study the error correction properties of the real - space renormalization group ( rg ). the long - distance operators are the ( approximately ) correctable operators encoded in the physical algebra of short - distance operators. this is closely related to modeling the holographic map as a quantum error correction code. as opposed to holography, the real - space rg of a many - body quantum system does not have the complementary recovery property. we discuss the role of large $ n $ and a large gap in the spectrum of operators in the emergence of complementary recovery. second, we study the operator algebra exact quantum error correction for any von neumann algebra. we show that similar to the finite dimensional case, for any error map in between von neumann algebras the petz dual of the error map is a recovery map if the inclusion of the correctable subalgebra of operators has finite index.
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arxiv:2012.14001
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we investigate the rates of drug resistance acquisition in a natural population using molecular epidemiological data from bolivia. first, we study the rate of direct acquisition of double resistance from the double sensitive state within patients and compare it to the rates of evolution to single resistance. in particular, we address whether or not double resistance can evolve directly from a double sensitive state within a given host. second, we aim to understand whether the differences in mutation rates to rifampicin and isoniazid resistance translate to the epidemiological scale. third, we estimate the proportion of mdr tb cases that are due to the transmission of mdr strains compared to acquisition of resistance through evolution. to address these problems we develop a model of tb transmission in which we track the evolution of resistance to two drugs and the evolution of vntr loci. however, the available data is incomplete, in that it is recorded only { for a fraction of the population and } at a single point in time. the likelihood function induced by the proposed model is computationally prohibitive to evaluate and accordingly impractical to work with directly. we therefore approach statistical inference using approximate bayesian computation techniques.
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arxiv:1704.04355
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the quantization error in a fixed - size self - organizing map ( som ) with unsupervised winner - take - all learning has previously been used successfully to detect, in minimal computation time, highly meaningful changes across images in medical time series and in time series of satellite images. here, the functional properties of the quantization error in som are explored further to show that the metric is capable of reliably discriminating between the finest differences in local contrast intensities and contrast signs. while this capability of the qe is akin to functional characteristics of a specific class of retinal ganglion cells ( the so - called y - cells ) in the visual systems of the primate and the cat, the sensitivity of the qe surpasses the capacity limits of human visual detection. here, the quantization error in the som is found to reliably signal changes in contrast or colour when contrast information is removed from or added to the image, but not when the amount and relative weight of contrast information is constant and only the local spatial position of contrast elements in the pattern changes. while the rgb mean reflects coarser changes in colour or contrast well enough, the som - qe is shown to outperform the rgb mean in the detection of single - pixel changes in images with up to five million pixels. this could have important implications in the context of unsupervised image learning and computational building block approaches to large sets of image data ( big data ), including deep learning blocks, and automatic detection of contrast change at the nanoscale in transmission or scanning electron micrographs ( tem, sem ), or at the subpixel level in multispectral and hyper - spectral imaging data.
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arxiv:2011.03970
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we consider the semi - classical limit of the quantum evolution of gaussian coherent states whenever the hamiltonian $ \ mathsf h $ is given, as sum of quadratic forms, by $ \ mathsf h = - \ frac { \ hbar ^ { 2 } } { 2m } \, \ frac { d ^ { 2 } \, } { dx ^ { 2 } } \, \ dot { + } \, \ alpha \ delta _ { 0 } $, with $ \ alpha \ in \ mathbb r $ and $ \ delta _ { 0 } $ the dirac delta - distribution at $ x = 0 $. we show that the quantum evolution can be approximated, uniformly for any time away from the collision time and with an error of order $ \ hbar ^ { 3 / 2 - \ lambda } $, $ 0 \! < \! \ lambda \! < \! 3 / 2 $, by the quasi - classical evolution generated by a self - adjoint extension of the restriction to $ \ mathcal c ^ { \ infty } _ { c } ( { \ mathscr m } _ { 0 } ) $, $ { \ mathscr m } _ { 0 } : = \ { ( q, p ) \! \ in \! \ mathbb r ^ { 2 } \, | \, q \! \ not = \! 0 \ } $, of ( $ - i $ times ) the generator of the free classical dynamics ; such a self - adjoint extension does not correspond to the classical dynamics describing the complete reflection due to the infinite barrier. similar approximation results are also provided for the wave and scattering operators.
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arxiv:1907.05801
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waldmeier [ 1971 ] found a very tight relationship between the f10. 7 solar radio flux and the sunspot number and suggested using the flux for an objective calibration of the sunspot number. he suggested that if this relationship changed later on, the sunspot number should be re - calibrated, assuming that the calibration must have drifted with time. i repeat his analysis using data up to the present and it is, indeed, clear that the relationship has changed significantly. this could be due to a drift of the calibration or to a secular change in the visibility of sunspots, or both.
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arxiv:1008.4832
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image restoration ( ir ) in real - world scenarios presents significant challenges due to the lack of high - capacity models and comprehensive datasets. to tackle these issues, we present a dual strategy : genir, an innovative data curation pipeline, and dreamclear, a cutting - edge diffusion transformer ( dit ) - based image restoration model. genir, our pioneering contribution, is a dual - prompt learning pipeline that overcomes the limitations of existing datasets, which typically comprise only a few thousand images and thus offer limited generalizability for larger models. genir streamlines the process into three stages : image - text pair construction, dual - prompt based fine - tuning, and data generation & filtering. this approach circumvents the laborious data crawling process, ensuring copyright compliance and providing a cost - effective, privacy - safe solution for ir dataset construction. the result is a large - scale dataset of one million high - quality images. our second contribution, dreamclear, is a dit - based image restoration model. it utilizes the generative priors of text - to - image ( t2i ) diffusion models and the robust perceptual capabilities of multi - modal large language models ( mllms ) to achieve photorealistic restoration. to boost the model ' s adaptability to diverse real - world degradations, we introduce the mixture of adaptive modulator ( moam ). it employs token - wise degradation priors to dynamically integrate various restoration experts, thereby expanding the range of degradations the model can address. our exhaustive experiments confirm dreamclear ' s superior performance, underlining the efficacy of our dual strategy for real - world image restoration. code and pre - trained models are available at : https : / / github. com / shallowdream204 / dreamclear.
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arxiv:2410.18666
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we studied in a microscopic multiphonon approach the proton - neutron symmetry and phonon structure of some low - lying states recently discovered in 92zr. we confirm the breaking of f - spin symmetry, but argue that the breaking mechanism is more complex than the one suggested in the original shell model analysis of the data. we found other new intriguing features of the spectrum, like a pronounced multiphonon fragmentation of the states and a tentative evidence of a three - phonon mixed symmetry state.
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arxiv:nucl-th/0403058
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high - order parametric models that include terms for feature interactions are applied to various data mining tasks, where ground truth depends on interactions of features. however, with sparse data, the high - dimensional parameters for feature interactions often face three issues : expensive computation, difficulty in parameter estimation and lack of structure. previous work has proposed approaches which can partially re - solve the three issues. in particular, models with factorized parameters ( e. g. factorization machines ) and sparse learning algorithms ( e. g. ftrl - proximal ) can tackle the first two issues but fail to address the third. regarding to unstructured parameters, constraints or complicated regularization terms are applied such that hierarchical structures can be imposed. however, these methods make the optimization problem more challenging. in this work, we propose strongly hierarchical factorization machines and anova kernel regression where all the three issues can be addressed without making the optimization problem more difficult. experimental results show the proposed models significantly outperform the state - of - the - art in two data mining tasks : cold - start user response time prediction and stock volatility prediction.
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arxiv:1712.09133
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conformal prediction methods create prediction bands with distribution - free guarantees but do not explicitly capture epistemic uncertainty, which can lead to overconfident predictions in data - sparse regions. although recent conformal scores have been developed to address this limitation, they are typically designed for specific tasks, such as regression or quantile regression. moreover, they rely on particular modeling choices for epistemic uncertainty, restricting their applicability. we introduce $ \ texttt { epicscore } $, a model - agnostic approach that enhances any conformal score by explicitly integrating epistemic uncertainty. leveraging bayesian techniques such as gaussian processes, monte carlo dropout, or bayesian additive regression trees, $ \ texttt { epicscore } $ adaptively expands predictive intervals in regions with limited data while maintaining compact intervals where data is abundant. as with any conformal method, it preserves finite - sample marginal coverage. additionally, it also achieves asymptotic conditional coverage. experiments demonstrate its good performance compared to existing methods. designed for compatibility with any bayesian model, but equipped with distribution - free guarantees, $ \ texttt { epicscore } $ provides a general - purpose framework for uncertainty quantification in prediction problems.
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arxiv:2502.06995
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we introduce a variant of multicut decomposition algorithms ( muda ), called cusmuda ( cut selection for multicut decomposition algorithms ), for solving multistage stochastic linear programs that incorporates strategies to select the most relevant cuts of the approximate recourse functions. we prove the convergence of the method in a finite number of iterations and use it to solve six portfolio problems with direct transaction costs under return uncertainty and six inventory management problems under demand uncertainty. on all problem instances cusmuda is much quicker than muda : between 5. 1 and 12. 6 times quicker for the porfolio problems considered and between 6. 4 and 15. 7 times quicker for the inventory problems.
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arxiv:1705.08977
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in this paper we study the type iv knorr held space time models. such models typically apply intrinsic markov random fields and constraints are imposed for identifiability. inla is an efficient inference tool for such models where constraints are dealt with through a conditioning by kriging approach. when the number of spatial and / or temporal time points become large, it becomes computationally expensive to fit such models, partly due to the number of constraints involved. we propose a new approach, hymik, dividing constraints into two separate sets where one part is treated through a mixed effect approach while the other one is approached by the standard conditioning by kriging method, resulting in a more efficient procedure for dealing with constraints. the new approach is easy to apply based on existing implementations of inla. we run the model on simulated data, on a real data set containing dengue fever cases in brazil and another real data set of confirmed positive test cases of covid - 19 in the counties of norway. for all cases we get very similar results when comparing the new approach with the tradition one while at the same time obtaining a significant increase in computational speed, varying on a factor from 2 to 4, depending on the sizes of the data sets.
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arxiv:2304.11851
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we introduce a notion of local hilbert - - schmidt stability, motivated by the recent definition by bradford of local permutation stability, and give examples of ( non - residually finite ) groups that are locally hilbert - - schmidt stable but not hilbert - - schmidt stable. for amenable groups, we provide a criterion for local hilbert - - schmidt stability in terms of group characters, by analogy with the character criterion of hadwin and shulman for hilbert - - schmidt stable amenable groups. furthermore, we study the ( very ) flexible analogues of local hilbert - - schmidt stability, and we prove several results analogous to the classical setting. finally, we prove that infinite sofic, respectively hyperlinear, property ( t ) groups are never locally permutation stable, respectively locally hilbert - - schmidt stable. this strengthens the result of becker and lubotzky for classical stability, and answers a question of lubotzky.
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arxiv:2307.13155
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this note comprises a synthesis of certain results in the theory of exact interpolation between hilbert spaces. in particular, we examine various characterizations of interpolation spaces and their relations to a number of results in operator - theory and in function - theory.
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arxiv:1401.6090
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this article reports on a study investigating how computational essays can be used to redistribute epistemic agency - - cognitive control and responsibility over one ' s own learning - - to students in higher education stem. computational essays are a genre of scientific writing that combine live, executable computer code with narrative text to present a computational model or analysis. the study took place across two contrasting university contexts : an interdisciplinary data science and modeling course at michigan state university, usa, and a third - semester physics course at the university of oslo, norway. over the course of a semester, computational essays were simultaneously and independently used in both courses, and comparable datasets of student artifacts and retrospective interviews were collected from both student populations. these data were analyzed using a framework which operationalized the construct of epistemic agency across the dimensions of programming, inquiry, data analysis and modeling, and communication. based on this analysis, we argue that computational essays can be a useful tool in redistributing epistemic agency to students within higher education science due to their combination of adaptability and disciplinary authenticity. however, we also argue that educational contexts, scaffolding, expectations, and student backgrounds can constrain and influence the ways in which students choose to take up epistemic agency.
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arxiv:2108.13080
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the paper analyses international migration flows from the network perspective by the evaluation of centrality indices. in order to find the most influential countries in the international migration network classical centrality indices and new centrality indices are evaluated. new centrality indices consider short ( sric ) and long - range ( lric ) indirect interactions and the node attribute : population of the destination country. the model is applied to the annual data on international migration flows from 1970 to 2013 provided by united nations organization. the analysis is made for one year of each decade and indices dynamics is described. it is shown that countries with huge migration flows are outlined by both classical and sric, lric indices, and sric and lric indices point out countries with considerable outflows of migrants to countries highly involved in international migration and the most interconnected countries.
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arxiv:1806.06705
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in this letter, we show that the semiclassical einstein ' s field equation can be recovered using the generalized entropy $ s _ { gen } $. this approach is reminiscent of non - equilibrium thermodynamics. furthermore, contrary to the entanglement equilibrium approach of deriving the semiclassical einstein ' s equation, this approach does not require any such assumptions and still recovers its correct form. therefore, in a sense, we also show the validity of the semiclassical approximation, a crucial approach for establishing a number of important ideas such as the hawking effect.
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arxiv:2404.16912
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in the recent work [ arxiv : 2308. 03216 ], coghi and maurelli proved pathwise uniqueness of solutions to the vorticity form of stochastic 2d euler equation, with kraichnan transport noise and initial data in $ l ^ 1 \ cap l ^ p $ for $ p > 3 / 2 $. the aim of this note is to remove the constraint on $ p $, showing that pathwise uniqueness holds for all $ l ^ 1 \ cap l ^ p $ initial data with arbitrary $ p > 1 $.
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arxiv:2406.07167
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a detailed study of the relativistic classical and quantum mechanics of the massless harmonic oscillator is presented.
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arxiv:1002.0474
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a quota mechanism, such as a mandatory grading curve, links together multiple decisions. we analyze the performance of quota mechanisms when the number of linked decisions is finite and the designer has imperfect knowledge of the type distribution. using a new optimal transport approach, we derive an ex - post decision error guarantee for quota mechanisms. this guarantee cannot be improved by any mechanisms without transfers. we quantify the sensitivity of quota mechanisms to errors in the designer ' s estimate of the type distribution. finally, we show that quotas are robust to agents ' beliefs about each other.
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arxiv:2309.07363
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starting from the relativistic gauge - invariant quark - antiquark green function we obtain the relevant interaction in the one - body limit, which can be interpreted as the kernel of a non - perturbative dirac equation. we study this kernel in different kinematic regions, reproducing, in particular, for heavy quark the potential case and sum rules results. we discuss the relevance of the result for heavy - light mesons and the relation with the phenomenological dirac equations used up to now in the literature.
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arxiv:hep-ph/9703377
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i give a proof of the semisimplicity of the action of the geometric frobenius on etale cohomology. this proof is based on the weil conjectures.
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arxiv:1009.0596
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in this paper, we study the class of jordan dialgebras. we develop an approach for reducing problems on dialgebras to the case of ordinary algebras. it is shown that straightforward generalizations of the classical cohn ' s, shirshov ' s, and macdonald ' s theorems do not hold for dialgebras. however, we prove dialgebraic analogues of these statements. also, we study polylinear special identities which hold in all special jordan algebras and do not hold in all jordan algebras. we find a natural correspondence between special identities for ordinary algebras and dialgebras.
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arxiv:1011.3683
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gathering relevant information to predict student academic progress is a tedious task. due to the large amount of irrelevant data present in databases which provides inaccurate results. currently, it is not possible to accurately measure and analyze student data because there are too many irrelevant attributes and features in the data. with the help of educational data mining ( edm ), the quality of information can be improved. this research demonstrates how edm helps to measure the accuracy of data using relevant attributes and machine learning algorithms performed. with edm, irrelevant features are removed without changing the original data. the data set used in this study was taken from kaggle. com. the results compared on the basis of recall, precision and f - measure to check the accuracy of the student data. the importance of this research is to help improve the quality of educational research by providing more accurate results for researchers.
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arxiv:2107.10669
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this paper studies the problem of designing sampled - data observers and observer - based, sampled - data, output feedback stabilizers for systems with both discrete and distributed, state and output time - delays. the obtained results can be applied to time delay systems of strict - feedback structure, transport partial differential equations ( pdes ) with nonlocal terms, and feedback interconnections of ordinary differential equations with a transport pde. the proposed design approach consists in exploiting an existing observer, which features robust exponential convergence of the error when continuous - time output measurements are available. the observer is then modified, mainly by adding an inter - sample output predictor, to compensate for the effect of data - sampling. using lyapunov stability tools and small - gain analysis, we show that robust exponential stability of the error is preserved, provided the sampling period is not too large. the general result is illustrated with different examples including state observation and output - feedback stabilization of a chemical reactor.
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arxiv:1907.06691
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new visible and k - band polarization measurements on stars surrounding molecular clouds in orion a and stars in the bn vicinity are presented. our results confirm that magnetic fields located inside the orion a molecular clouds and in their close neighborhood are spatially connected. on and around the bn object, we measured the angular offsets between the k - band polarization data and available submm data. we find high values of the polarization degree, p _ { k }, and of the optical depth, \ tau _ { k }, close to an angular offset position of 90 ^ { \ circ } whereas lower values of p _ { k } and \ tau _ { k } are observed for smaller angular offsets. we interpret these results as evidence for the presence of various magnetic field components toward lines of sight in the vicinity of bn. on a larger scale, we measured the distribution of angular offsets between available h - band polarization data and the same submm data set. here we find an increase of < p _ { h } > with angular offset which we interpret as a rotation of the magnetic field by \ lesssim 60 ^ { \ circ }. this trend generalizes previous results on small scale toward and around lines of sight to bn and is consistent with a twist of the magnetic field on a larger scale towards omc - 1. a comparison of our results with several other studies suggests that a two - component magnetic field, maybe helical, could be wrapping the omc - 1 filament.
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arxiv:1108.5925
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due to a rapid change of the entropy density $ s ( t ) $ across the critical temperature $ t _ c $ of the qcd phase transition, the pressure $ p ( t ) $ and the energy density $ e ( t ) $ above $ t _ c $ generally deviate from their stefan - boltzmann values. we shall demonstrate this both analytically and numerically for a general class of $ s ( t ) $ consistent with thermodynamical constraints and make a qualitative comparison of the result with the lattice qcd data. quantities related to $ ds ( t ) / dt $ such as the specific heat and sound velocity are also discussed.
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arxiv:hep-ph/9508360
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nuclear spin - lattice relaxation in one - dimensional heisenberg ferrimagnets is studied by means of a modified spin - wave theory. calculating beyond the first - order mechanism, where a nuclear spin directly interacts with spin waves through the hyperfine coupling, we demonstrate that the exchange - scattering - enhanced three - magnon nuclear relaxation may generally predominate over the raman one with increasing temperature and decreasing field. recent proton spin - lattice relaxation - time ( t _ 1 _ ) measurements on the ferrimagnetic chain compound nicu ( c _ 7 _ h _ 6 _ n _ 2 _ o _ 6 _ ) ( h _ 2 _ o ) _ 3 _ 2h _ 2 _ o suggest that the major contribution to 1 / t _ 1 _ be made by the three - magnon scattering.
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arxiv:cond-mat/0512629
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primordial stars formed in the early universe are thought to be hosted by compact dark matter ( dm ) halos. if dm consists of weakly interacting massive particles ( wimps ), such stars may be powered by dm annihilation during the early phases of their evolutions. we study the pre - main sequence evolutions of the primordial star using a detailed stellar evolution code under the assumption that the annihilation of adiabatically contracted wimps dm within the star provides a sufficient energy to sustain the stellar equilibrium. we follow the evolution of accreting stars using several gas mass accretion rates derived from cosmological simulations. we show that the stellar mass becomes very large, up to 900 - 1000 m _ sun when the star reaches the main - sequence phase for a reasonable set of model parameters such as dm particle mass and the annihilation cross section. during the dark star phase, the star expands over a thousand solar - radii, while the surface temperature remains below 10 ^ 4 k. the energy generated by nuclear reactions is not dominant during this phase. we also study models with different gas mass accretion rates and the dm particle masses. all our models for different dm particle masses pass the dark star phase. the final mass of the dark stars is essentially unchanged for dm mass of m _ dm < = 10 gev. gravitational collapse of the massive dark stars will leave massive black holes with mass as large as 1000 m _ sun in the early universe.
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arxiv:1105.1255
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we derive direct representations of the scaling functions of the 3d o ( 4 ) model which are relevant for comparisons to other models, in particular qcd. this is done in terms of expansions in the scaling variable z = t / h ^ { 1 / delta }. the expansions around z = 0 and the corresponding asymptotic ones for z - - > + - infinity overlap such that no interpolation is needed. the expansion coefficients are determined numerically from the data of a previous high statistics simulation of the o ( 4 ) model on a three - dimensional lattice of linear extension l = 120. from the scaling function of the magnetization we calculate the leading asymptotic coefficients of the scaling function of the free energy density. as a result we obtain the universal amplitude ratio a ^ + / a ^ - = 1. 84 ( 4 ) for the specific heat. comparing the scaling function of the energy density to the data we find the non - singular part of the energy density epsilon _ { ns } ( t ) with high precision and at the same time excellent scaling properties.
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arxiv:1105.0584
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data from direct numerical simulation of open channel flow over a geometrically rough wall at a bulk reynolds number of 2900, generated by chan - braun et al. [ " force and torque acting on particles in a transitionally rough open - channel flow ", j. fluid mech. 684, 441 - - 474 ( 2011 ), 10. 1017 / jfm. 2011. 311 ] are further analysed with respect to the time and length scales of force and torque acting on the wall - mounted spheres. for the two sizes of spheres in a square arrangement ( 11 and 49 wall units in diameter, yielding hydraulically smooth and transitionally rough flow, respectively ), the spatial structure of drag, lift and spanwise torque is investigated. the auto - correlation and spectra in time as well as the space - time correlation and convection velocities are presented and discussed. it is found that the statistics of spanwise particle torque are similar to those of shear stress at a smooth wall. particle drag and lift are shown to differ from spanwise particle torque, exhibiting considerably smaller time and length scales ; the convection velocities of drag and lift are somewhat larger than those of spanwise torque. furthermore, correlations between the flow field and particle - related quantities are presented. the spatial structure of the correlation between streamwise velocity and drag / spanwise torque features elongated shapes reminiscent of buffer - layer streaks. the correlation between the pressure field and the particle drag exhibits two opposite - signed bulges on the upstream and downstream sides of a particle.
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arxiv:1306.0680
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we consider an echo - assisted communication model wherein block - coded messages, when transmitted across several frames, reach the destination as multiple noisy copies. we address adversarial attacks on such models wherein a subset of the noisy copies are vulnerable to manipulation by an adversary. particularly, we study a non - persistent attack model with the adversary attacking 50 % of the frames on the vulnerable copies in an i. i. d. fashion. we show that this adversarial model drives the destination to detect the attack locally within every frame, thereby resulting in degraded performance due to false - positives and miss - detection. our main objective is to characterize the mutual information of this adversarial echo - assisted channel by incorporating the performance of attack - detection strategies. with the use of an imperfect detector, we show that the compound channel comprising the adversarial echo - assisted channel and the attack detector exhibits memory - property, and as a result, obtaining closed - form expressions on mutual information is intractable. to circumvent this problem, we present a new framework to approximate the mutual information by deriving sufficient conditions on the channel parameters and also the performance of the attack detectors. finally, we propose two attack - detectors, which are inspired by traditional as well as neural - network ideas, and show that the mutual information offered by these detectors is close to that of the genie detector for short frame - lengths.
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arxiv:1901.07013
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it is shown that each monotone minkowski endomorphism of convex bodies gives rise to an isoperimetric inequality which directly implies the classical urysohn inequality. among this large family of new inequalities, the only affine invariant one - the blaschke - santal \ ' o inequality - turns out to be the strongest one. a further extension of these inequalities to merely weakly monotone minkowski endomorphisms is proven to be impossible. moreover, for functional analogues of monotone minkowski endomorphisms, a family of analytic inequalities for log - concave functions is established which generalizes the functional blaschke - santal \ ' o inequality.
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arxiv:2101.07031
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the set n of natural numbers as given and form sn, the superstructure over n. this is often considered the universe of ordinary mathematics. the idea is that all of the mathematics that is ordinarily studied refers to elements of this universe. for example, any of the usual constructions of the real numbers ( say by dedekind cuts ) belongs to sn. even non - standard analysis can be done in the superstructure over a non - standard model of the natural numbers. there is a slight shift in philosophy from the previous section, where the universe was any set u of interest. there, the sets being studied were subsets of the universe ; now, they are members of the universe. thus although p ( sx ) is a boolean lattice, what is relevant is that sx itself is not. consequently, it is rare to apply the notions of boolean lattices and venn diagrams directly to the superstructure universe as they were to the power - set universes of the previous section. instead, one can work with the individual boolean lattices pa, where a is any relevant set belonging to sx ; then pa is a subset of sx ( and in fact belongs to sx ). in cantor ' s case x = r in particular, arbitrary sets of real numbers are not available, so there it may indeed be necessary to start the process all over again. = = in set theory = = it is possible to give a precise meaning to the claim that sn is the universe of ordinary mathematics ; it is a model of zermelo set theory, the axiomatic set theory originally developed by ernst zermelo in 1908. zermelo set theory was successful precisely because it was capable of axiomatising " ordinary " mathematics, fulfilling the programme begun by cantor over 30 years earlier. but zermelo set theory proved insufficient for the further development of axiomatic set theory and other work in the foundations of mathematics, especially model theory. for a dramatic example, the description of the superstructure process above cannot itself be carried out in zermelo set theory. the final step, forming s as an infinitary union, requires the axiom of replacement, which was added to zermelo set theory in 1922 to form zermelo – fraenkel set theory, the set of axioms most widely accepted today. so while ordinary mathematics may be done in sn, discussion of sn goes beyond the " ordinary ", into metamathematics. but if high - powered set theory
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https://en.wikipedia.org/wiki/Universe_(mathematics)
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a theory of quantum dynamics based on a discrete structure underlying the space time manifold is developed for single particles. it is shown that at the micro domain the interaction of particles with the underlying discrete structure results in the quantum space time manifold. regarding the resulting quantum space - time as perturbation from the lorentz metric it is shown it is possible to discuss the dynamics of particles in the quantum domain.
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arxiv:quant-ph/0610042
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code generation aims to produce code that fulfills requirements written in natural languages automatically. large language models ( llms ) like chatgpt have demonstrated promising effectiveness in this area. nonetheless, these llms often fail to ensure the syntactic and semantic correctness of the generated code. recently, researchers proposed multi - agent frameworks that guide llms with different prompts to analyze programming tasks, generate code, perform testing in a sequential workflow. however, the performance of the workflow is not robust as the code generation depends on the performance of each agent. to address this challenge, we propose codecor, a self - reflective multi - agent framework that evaluates the effectiveness of each agent and their collaborations. specifically, for a given task description, four agents in codecor generate prompts, code, test cases, and repair advice, respectively. each agent generates more than one output and prunes away the low - quality ones. the generated code is tested in the local environment : the code that fails to pass the generated test cases is sent to the repair agent and the coding agent re - generates the code based on repair advice. finally, the code that passes the most number of generated test cases is returned to users. our experiments on four widely used datasets, humaneval, humaneval - et, mbpp, and mbpp - et, demonstrate that codecor significantly outperforms existing baselines ( e. g., codecot and mapcoder ), achieving an average pass @ 1 score of 77. 8 %.
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arxiv:2501.07811
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we perform direct numerical simulations of laminar separated flows over finite - aspect - ratio swept wings at a chord - base reynolds number of $ re = 400 $ to reveal a variety of wake structures generated for a range of aspect ratios ( $ sar = 0. 5 - 4 $ ), angles of attack ( $ \ alpha = 16 ^ { \ circ } - 30 ^ { \ circ } $ ), and sweep angles ( $ \ lambda = 0 ^ { \ circ } - 45 ^ { \ circ } $ ). flows behind swept wings exhibit increased complexity in their dynamical features compared to unswept - wing wakes. for unswept wings, the wake dynamics are predominantly influenced by the tip effects. steady wakes are mainly limited to low - aspect - ratio wings. unsteady vortex shedding takes place near the midspan of higher - $ ar $ wings due to weakened downwash induced by the tip vortices. with increasing sweep angle, the source of three dimensionality transitions from the tip to the midspan. a pair of symmetric vortical structures forms along the two sides of the midspan, imposing downward velocity upon each other in a manner similar to the downwash induced by tip vortices. such stabilizing midspan effects not only expand the steady wake region to higher aspect ratios, but also enhance lift. at higher aspect ratios, the midspan effects of swept wings diminish at outboard region, allowing unsteady vortex shedding to develop near the tip. in the wakes of highly swept wings, streamwise finger - like structures form repetitively along the wing span, providing a stabilizing effect. the insights revealed from this study can aid the design of high - lift devices and serve as a stepping stone for understanding the complex wake dynamics at higher reynolds numbers and those generated by unsteady wing maneuvers.
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arxiv:2005.09737
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in this paper we classify and construct differential symmetry breaking operators $ \ mathbb { d } $ from a line bundle over the real projective space $ \ mathbb { r } \ mathbb { p } ^ n $ to a vector bundle over $ \ mathbb { r } \ mathbb { p } ^ { n - 1 } $. we further determine the factorization identities of $ \ mathbb { d } $ and the branching laws of the corresponding generalized verma modules of $ \ mathfrak { sl } ( n + 1, \ mathbb { c } ) $. by utilizing the factorization identities, the $ sl ( n, \ mathbb { r } ) $ - representations realized on the image $ \ text { im } ( \ mathbb { d } ) $ are also investigated.
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arxiv:2408.01213
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since the development of the conjugate gradient ( cg ) method in 1952 by hestenes and stiefel, cg, has become an indispensable tool in computational mathematics for solving positive definite linear systems. on the other hand, the conjugate residual ( cr ) method, closely related cg and introduced by stiefel in 1955 for the same settings, remains relatively less known outside the numerical linear algebra community. since their inception, these methods - - henceforth collectively referred to as conjugate direction methods - - have been extended beyond positive definite to indefinite, albeit consistent, settings. going one step further, in this paper, we investigate the theoretical and empirical properties of these methods under inconsistent systems. among other things, we show that small modifications to the original algorithms allow for the pseudo - inverse solution. furthermore, we show that cr is essentially equivalent to the minimum residual method, proposed by paige and saunders in 1975, in such contexts. lastly, we conduct a series of numerical experiments to shed lights on their numerical stability ( or lack thereof ) and their performance for inconsistent systems. surprisingly, we will demonstrate that, unlike cr and contrary to popular belief, cg can exhibit significant numerical instability, bordering on catastrophe in some instances.
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arxiv:2401.11714
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the strength and spectrum of the extragalactic magnetic field are still unknown. its measurement would help answer the question of whether galactic fields are purely a primordial relic or were dynamically enhanced from a much smaller cosmological seed field. in this letter, we show that the composition, spectrum, and directional distribution of extragalactic ultrahigh energy cosmic rays with energies above $ \ simeq 10 ^ { 18 } \ ev $ can probe the large scale component of the extragalactic magnetic field below the present observational upper limit of $ 10 ^ { - 9 } $ gauss. cosmic ray detectors under construction or currently in the proposal stage should be able to test the existence of the extragalactic magnetic fields on scales of a few to tens of mpc and strengths in the range $ \ simeq 10 ^ { - 10 } - 10 ^ { - 9 } $ gauss.
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arxiv:astro-ph/9508088
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suppose $ h $ is a hyperbolic subgroup of a hyperbolic group $ g $. assume there exists $ n > 0 $ such that the intersection of $ n $ essentially distinct conjugates of $ h $ is always finite. further assume $ g $ splits over $ h $ with hyperbolic vertex and edge groups and the two inclusions of $ h $ are quasi - isometric embeddings. then $ h $ is quasiconvex in $ g $. this answers a question of swarup and provides a partial converse to the main theorem of \ cite { gmrs }.
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arxiv:math/0403125
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the systematic underestimation of band gaps is one of the most fundamental challenges in semilocal density functional theory ( dft ). in addition to hindering the application of dft to predicting electronic properties, the band gap problem is intimately related to self - interaction and delocalization errors, which make the study of charge transfer mechanisms with dft difficult. in this work, we present two key innovations to address the band gap problem. first, we design an approach for machine learning density functionals based on gaussian processes to explicitly fit single - particle energy levels. second, we introduce novel nonlocal features of the density matrix that are expressive enough to fit these single - particle levels. combining these developments, we train a machine - learned functional for the exact exchange energy that predicts molecular energy gaps and reaction energies of a wide range of molecules in excellent agreement with reference hybrid dft calculations. in addition, while being trained solely on molecular data, our model predicts reasonable formation energies of polarons in solids, showcasing its transferability and robustness. our approach generalizes straightforwardly to full exchange - correlation functionals, thus paving the way to the design of novel state - of - the - art functionals for the prediction of electronic properties of molecules and materials.
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arxiv:2403.17002
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we apply the regge - wheeler formalism to study axial and polar gravitational waves in kantowski - sachs universe. the background field equations and the linearised perturbation equations for the modes are derived in presence of matter. to find analytical solutions, we analyze the propagation of waves in vacuum spacetime. the background field equations in absence of matter are solved by assuming the expansion scalar to be proportional to the shear scalar. using the method of separation of variables, the axial perturbation parameter $ h _ 0 ( t, r ) $ is obtained from its wave equation. the other perturbation $ h _ 1 ( t, r ) $ is then determined from $ h _ 0 ( t, r ) $. the anisotropy of the background spacetime is responsible for the damping of the axial waves. the polar perturbation equations are much more involved compared to their flrw counterparts, as well as to the axial perturbations in kantowski - sachs background. in both the axial and polar cases, the radial and temporal solutions separate out as products. the temporal part of the polar perturbation solutions are plotted against time to obtain an order of magnitude estimate of the frequency of the propagating gws and lies in the range 1000 - 2000 hz. using standard observational data for the gw strain we have placed constraints on the parameters in the polar perturbation solutions. the perturbation equations in presence of matter show that the axial waves can cause perturbations only in the azimuthal velocity of the fluid without deforming the matter field. but the polar waves must perturb the energy density, the pressure and also the non - azimuthal components of the fluid velocity.
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arxiv:2106.03203
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we give a general reduction of lengths - of - proofs lower bounds for constant depth frege systems in demorgan language augmented by a connective counting modulo a prime $ p $ ( the so called $ ac ^ 0 [ p ] $ frege systems ) to computational complexity lower bounds for search tasks involving search trees branching upon values of maps on the vector space of low degree polynomials over the finite filed with $ p $ elements.
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arxiv:1311.2501
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two dimensional electron gases ( 2degs ) realized at gaas / algaas single interfaces by molecular - beam epitaxy ( mbe ) reach mobilities of about 15 million cm ^ 2 / vs if the algaas alloy is grown after the gaas. surprisingly, the mobilities may drop to a few millions for the identical but inverted algaas / gaas interface, i. e. reversed layering. here we report on a series of inverted heterostructures with varying growth parameters including temperature, doping, and composition. minimizing the segregation of both dopants and background impurities leads to mobilities of 13 million cm ^ 2 / vs for inverted structures. the dependence of the mobility on electron density tunes by a gate or by illumination is found to be the identical if no doping layers exist between the 2deg and the respective gate. otherwise, it differs significantly compared to normal interface structures. reducing the distance of the 2deg to the surface down to 50nm requires an additional doping layer between 2deg and surface in order to compensate for the surface - schottky barrier. the suitability of such shallow inverted structures for future semiconductor - superconductor hybrid systems is discussed. lastly, our understanding of the improved inverted interface enables us to produce optimized double - sided doped quantum wells exhibiting an electron mobility of 40 million cm ^ 2 / vs at 1k.
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arxiv:2103.15935
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for the interpretation of x - ray radiation from kiloparsec jets of quasars, the inverse compton scattering of the cosmic microwave background has been widely used for almost 20 years. a recent analysis of the fermi - lat observational data showed that this assumption is inapplicable for jets of several quasars. in this paper, we consider the inverse compton scattering of photons from a central source as a possible mechanism for the formation of x - ray radiation from kiloparsec jets of the quasars pks 0637 - 752, 3c 273, pks 1510 - 089, and pks 1045 - 188. estimates for the angle between the line of sight and the velocity of kiloparsec - scale jets are obtained. the predicted gamma - ray flux for all objects turned out to be below the upper limit on the flux from a kiloparsec jet obtained from the fermi - lat data. it is shown that our assumption about the mechanism of kiloparsec jets x - ray radiation is consistent with all data of multiwavelength observations available to date.
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arxiv:2012.04923
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we consider the problem of online interval scheduling on a single machine, where intervals arrive online in an order chosen by an adversary, and the algorithm must output a set of non - conflicting intervals. traditionally in scheduling theory, it is assumed that intervals arrive in order of increasing start times. we drop that assumption and allow for intervals to arrive in any possible order. we call this variant any - order interval selection ( aois ). we assume that some online acceptances can be revoked, but a feasible solution must always be maintained. for unweighted intervals and deterministic algorithms, this problem is unbounded. under the assumption that there are at most $ k $ different interval lengths, we give a simple algorithm that achieves a competitive ratio of $ 2k $ and show that it is optimal amongst deterministic algorithms, and a restricted class of randomized algorithms we call memoryless, contributing to an open question by adler and azar 2003 ; namely whether a randomized algorithm without access to history can achieve a constant competitive ratio. we connect our model to the problem of call control on the line, and show how the algorithms of garay et al. 1997 can be applied to our setting, resulting in an optimal algorithm for the case of proportional weights. we also discuss the case of intervals with arbitrary weights, and show how to convert the single - length algorithm of fung et al. 2014 into a classify and randomly select algorithm that achieves a competitive ratio of 2k. finally, we consider the case of intervals arriving in a random order, and show that for single - lengthed instances, a one - directional algorithm ( i. e. replacing intervals in one direction ), is the only deterministic memoryless algorithm that can possibly benefit from random arrivals.
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arxiv:2303.06127
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by invoking the microscopic response method in conjunction with a reasonable set of approximations, we obtain new explicit expressions for the electrical conductivity and temperature coefficient of resistivity ( tcr ) in amorphous semiconductors, especially a - si : h and a - ge : h. the predicted tcr for n - doped a - si : h and a - ge : h is in agreement with experiments. the conductivity from the transitions from a localized state to an extended state ( le ) is comparable to that from the transitions between two localized states ( ll ). this resolves a long - standing anomaly, a " kink " in the experimental $ \ log _ { 10 } \ sigma $ vs. t $ ^ { - 1 } $ curve.
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arxiv:1112.2169
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much research in stringology focuses on structures that can, in a way, ` ` grasp ' ' repeats ( substrings that occur multiple times ) as, for example, the so - called runs, a. k. a. maximal repetitions, compactly describe all tandem repeats. in this paper we introduce closed repeats : given a string $ s $, its non - empty substring $ s [ i \,.. \, j ] $ is a right ( left ) closed repeat if its closest occurrence $ s [ i ' \,.. \, j ' ] $ with $ i ' > i $ cannot be ` ` extended ' ' to the right ( respectively, left ) matching $ s [ j { + } 1 ] = s [ j ' { + } 1 ] $ ( respectively, $ s [ i { - } 1 ] = s [ i ' { - } 1 ] $ ) ; the repeat is closed if it is both left and right closed. we note that the closed repeats correspond to the maximal closed substrings recently proposed by badkobeh et al. and they include all runs as a special case. we prove that the number of right / left closed repeats is $ o ( n \ log n ) $, where $ n $ is the length of $ s $, and we show that this bound is tight. the ( right / left ) closed repeats can be computed in the optimal time $ o ( n \ log n ) $ ; as we prove, the computation time cannot be lower than $ \ omega ( n \ log \ sigma ) $ over a general ordered alphabet of size $ \ sigma $ even when the number of the closed repeats is $ o ( n ) $. as an application, we describe data structures using the closed repeats for a number of substring queries : finding the period of the substring provided it is ` ` periodic ' ', finding the longest repeat in the substring, computing the rightmost lz77 parsing of the substring.
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arxiv:2410.00209
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open radio access network systems, with their virtualized base stations ( vbss ), offer operators the benefits of increased flexibility, reduced costs, vendor diversity, and interoperability. optimizing the allocation of resources in a vbs is challenging since it requires knowledge of the environment, ( i. e., " external ' ' information ), such as traffic demands and channel quality, which is difficult to acquire precisely over short intervals of a few seconds. to tackle this problem, we propose an online learning algorithm that balances the effective throughput and vbs energy consumption, even under unforeseeable and " challenging ' ' environments ; for instance, non - stationary or adversarial traffic demands. we also develop a meta - learning scheme, which leverages the power of other algorithmic approaches, tailored for more " easy ' ' environments, and dynamically chooses the best performing one, thus enhancing the overall system ' s versatility and effectiveness. we prove the proposed solutions achieve sub - linear regret, providing zero average optimality gap even in challenging environments. the performance of the algorithms is evaluated with real - world data and various trace - driven evaluations, indicating savings of up to 64. 5 % in the power consumption of a vbs compared with state - of - the - art benchmarks.
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arxiv:2309.01730
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we provide arguments for the use of the rational form of unitarization, its relation with the diffraction peak shrinkage and asymptotics of the inelastic cross - - section. the particular problems of the regge model and the exponential form of unitarization with a factorized eikonal are discussed as well. central role belongs to the asymptotic amplitude factorization resulting from mandelstam analyticity and its symmetry over the scattering variables.
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arxiv:2206.02360
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in this paper, we study an optimal control problem for a brain tumor growth model that incorporates lactate metabolism, viscoelastic effects, and tissue damage. the pde system, introduced in [ g. cavalleri, p. colli, a. miranville, e. rocca, on a brain tumor growth model with lactate metabolism, viscoelastic effects, and tissue damage ( 2025 ) ], couples a fisher - kolmogorov type equation for tumor cell density with a reaction - diffusion equation for the lactate, a quasi - static force balance governing the displacement, and a nonlinear differential inclusion for tissue damage. the control variables, representing chemotherapy and a lactate - targeting drug, influence tumor progression and treatment response. starting from well - posedness, regularity, and continuous dependence results already established, we define a suitable cost functional and prove the existence of optimal controls. then, we analyze the differentiability of the control - to - state operator and establish a necessary first - order condition for treatment optimality.
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arxiv:2503.17049
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in 2016, the global burden of disease reported that neurological disorders were the principal cause of disability - adjusted life years ( dalys ) and the second leading cause of deaths. research in the last decade has pushed neuroscience to design and implement low - cost, efficient, implantable, flexible electrodes / probes and 3d arrays for neuron stimulation and sensing. electrical arrays used in current cmos - based technologies can be affected by the migration of cells ( such as astrocytes ) that attempt to seal off the electronic devices, causing increased impedance and alternations in the electric field. in this regard, magnetic nanodevices can be better candidates. a wide assortment of magnetic skyrmion - based device ideas and models have as of late been proposed featuring their potential applications. in this paper we propose a highly tunable skyrmion - based spintronic nanodevice for neuron stimulation. the effects of tunable material and magnetic properties specifically dzyaloshinskii - moriya interaction ( dmi ), perpendicular magnetic anisotropy ( pma ) constant, number of skyrmions and device dimensions on stable skyrmion nucleation and smooth skyrmion dynamics in a magnetic ultra - thin film have been extensively studied. the aim of this study was to meet the standard therapeutic specifications of neuron stimulation, which is an electric field of about 10 mv / mm for a duration of 50 { \ mu } s. from faraday ' s laws of induction, skyrmion dynamics that generates an alternating magnetic flux density induces an electric field for a certain time duration in the ultra - thin film. the results of this work show that on tuning the skyrmion dynamics, the induced electric field can reach the standard value required for neurostimulation, thereby providing a strong futuristic possibility to exploit skyrmion - based spintronic nanodevices for neuron stimulation.
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arxiv:1901.01349
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the observations of psr j0952 - 0607 and the second object in gw190814 event indicate the possible existence of supermassive neutron stars. in this work, by using the constant - sound - speed ( css ) parametrization to describe the equation of state ( eos ) of quark matter, the constraints on the eos parameters from supermassive hybrid stars are investigated through the maxwell and gibbs constructions. it is shown that to support a supermassive hybrid star, a lower transition energy density, a smaller energy density discontinuity and a higher sound speed of quark matter are favored. for the constructed hybrid star eos model, the maximum mass of the corresponding hybrid stars will not meet the lower mass limit of the second object in gw190814 if the energy density discontinuity takes a value higher than $ 180 ~ { \ rm mev ~ fm ^ { - 3 } } $. moreover, it is confirmed that the supermassive neutron star observation can also rule out the existence of twin stars as a supermassive hybrid star requires a relatively small energy density discontinuity. finally, we give a rough estimate of the lower limit of the dimensionless tidal deformability of neutron stars which ranges from 2 to 3.
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arxiv:2308.06993
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bilevel optimization has gained significant attention in recent years due to its broad applications in machine learning. this paper focuses on bilevel optimization in decentralized networks and proposes a novel single - loop algorithm for solving decentralized bilevel optimization with a strongly convex lower - level problem. our approach is a fully single - loop method that approximates the hypergradient using only two matrix - vector multiplications per iteration. importantly, our algorithm does not require any gradient heterogeneity assumption, distinguishing it from existing methods for decentralized bilevel optimization and federated bilevel optimization. our analysis demonstrates that the proposed algorithm achieves the best - known convergence rate for bilevel optimization algorithms. we also present experimental results on hyperparameter optimization problems using both synthetic and mnist datasets, which demonstrate the efficiency of our proposed algorithm.
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arxiv:2311.08945
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we aim to study the effects of controlling the resource level in agent - based models. we study, both numerical and analytically, a binary - agent - resource ( b - a - r ) model in which $ n $ agents are competing for resources described by a resource level $ 1 / 2 \ leq { \ cal l } < 1 $, where $ { \ cal l } = l / n $ with $ l $ being the maximum amount of resource per turn available to the agents. each agent picks the momentarily best - performing strategy for decision with the performance of the strategy being a result of the cumulative collective decisions of the agents. the agents may or may not be networked for information sharing. detailed numerical simulations reveal that the system exhibits well - defined plateaux regions in the success rate which are separated from each other by abrupt transitions. as $ l $ increases, the maximum success rate forms a well defined sequence of simple fractions. we analyze the features by studying the outcome time series, the dynamics of the strategies ' performance ranking pattern and the dynamics in the history space. while the system tends to explore the whole history space due to its competitive nature, an increasing $ l $ has the effect of driving the system to a restricted portion of the history space. thus the underlying cause of the observed features is an interesting self - organized phenomena in which the system, in response to the global resource level, effectively avoids particular patterns of history outcomes. we also compare results in networked population with those in non - networked population.
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arxiv:cond-mat/0505575
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computational galois theory, in particular the problem of computing the galois group of a given polynomial is a very old problem. currently, the best algorithmic solution is stauduhar ' s method. computationally, one of the key challenges in the application of stauduhar ' s method is to find, for a given pair of groups h < g a g - relative h - invariant, that is a multivariate polynomial f that is h - invariant, but not g - invariant. while generic, theoretical methods are known to find such f, in general they yield impractical answers. we give a general method for computing invariants of large degree which improves on previous known methods, as well as various special invariants that are derived from the structure of the groups. we then apply our new invariants to the task of computing the galois groups of polynomials over the rational numbers, resulting in the first practical degree independent algorithm.
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arxiv:1211.3588
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we study the problem of fitting the high dimensional sparse linear regression model with sub - gaussian covariates and responses, where the data are provided by strategic or self - interested agents ( individuals ) who prioritize their privacy of data disclosure. in contrast to the classical setting, our focus is on designing mechanisms that can effectively incentivize most agents to truthfully report their data while preserving the privacy of individual reports. simultaneously, we seek an estimator which should be close to the underlying parameter. we attempt to solve the problem by deriving a novel private estimator that has a closed - form expression. based on the estimator, we propose a mechanism which has the following properties via some appropriate design of the computation and payment scheme : ( 1 ) the mechanism is $ ( o ( 1 ), o ( n ^ { - \ omega ( { 1 } ) } ) ) $ - jointly differentially private, where $ n $ is the number of agents ; ( 2 ) it is an $ o ( \ frac { 1 } { n } ) $ - approximate bayes nash equilibrium for a $ ( 1 - o ( 1 ) ) $ - fraction of agents to truthfully report their data ; ( 3 ) the output could achieve an error of $ o ( 1 ) $ to the underlying parameter ; ( 4 ) it is individually rational for a $ ( 1 - o ( 1 ) ) $ fraction of agents in the mechanism ; ( 5 ) the payment budget required from the analyst to run the mechanism is $ o ( 1 ) $. to the best of our knowledge, this is the first study on designing truthful ( and privacy - preserving ) mechanisms for high dimensional sparse linear regression.
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arxiv:2410.13046
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zero - shot sketch - based image retrieval ( sbir ) is an emerging task in computer vision, allowing to retrieve natural images relevant to sketch queries that might not been seen in the training phase. existing works either require aligned sketch - image pairs or inefficient memory fusion layer for mapping the visual information to a semantic space. in this work, we propose a semantically aligned paired cycle - consistent generative ( sem - pcyc ) model for zero - shot sbir, where each branch maps the visual information to a common semantic space via an adversarial training. each of these branches maintains a cycle consistency that only requires supervision at category levels, and avoids the need of highly - priced aligned sketch - image pairs. a classification criteria on the generators ' outputs ensures the visual to semantic space mapping to be discriminating. furthermore, we propose to combine textual and hierarchical side information via a feature selection auto - encoder that selects discriminating side information within a same end - to - end model. our results demonstrate a significant boost in zero - shot sbir performance over the state - of - the - art on the challenging sketchy and tu - berlin datasets.
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arxiv:1903.03372
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this paper presents the details of a system capable of recording on video a traditional class. by traditional class it is meant a teacher, a blackboard and a white canvas where course notes are projected. the system is able to track the movements of the lecturer, while recording it on video at the required frame rate ( e. g., 25 fps ). the system is also capable of understanding five arm gestures made by the lecturer with the intent of controlling which scenario is recorded : himself, the blackboard or the white canvas. the remaining two gestures are for start / stop the recorder. the system is composed by a kinect sensor, a video camera, a microphone, one pan - tilt system and one pan system, using a total of three step motors.
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arxiv:1501.00149
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we describe a cognitive architecture intended to solve a wide range of problems based on the five identified principles of brain activity, with their implementation in three subsystems : logical - probabilistic inference, probabilistic formal concepts, and functional systems theory. building an architecture involves the implementation of a task - driven approach that allows defining the target functions of applied applications as tasks formulated in terms of the operating environment corresponding to the task, expressed in the applied ontology. we provide a basic ontology for a number of practical applications as well as for the subject domain ontologies based upon it, describe the proposed architecture, and give possible examples of the execution of these applications in this architecture.
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arxiv:2204.07919
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e - commerce search and recommendation usually operate on structured data such as product catalogs and taxonomies. however, creating better search and recommendation systems often requires a large variety of unstructured data including customer reviews and articles on the web. traditionally, the solution has always been converting unstructured data into structured data through information extraction, and conducting search over the structured data. however, this is a costly approach that often has low quality. in this paper, we envision a solution that does entirely the opposite. instead of converting unstructured data ( web pages, customer reviews, etc ) to structured data, we instead convert structured data ( product inventory, catalogs, taxonomies, etc ) into textual data, which can be easily integrated into the text corpus that trains llms. then, search and recommendation can be performed through a q / a mechanism through an llm instead of using traditional information retrieval methods over structured data.
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arxiv:2312.03217
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we report superconducting properties of noncentrosymmetric superconductor laptge which crystallizes in noncentrosymmetric $ \ alpha $ - thsi $ _ { 2 } $ structure. the magnetization, resistivity and specific heat measurements confirm that laptge is a type - ii bulk superconductor with a transition temperature t $ _ { c } $ = 3. 05 $ \ pm $ 0. 05 k. muon - spin relaxation / rotation measurements confirms that time reversal preserved in the superconducting ground state.
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arxiv:1810.03271
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deep learning is changing many areas in molecular physics, and it has shown great potential to deliver new solutions to challenging molecular modeling problems. along with this trend arises the increasing demand of expressive and versatile neural network architectures which are compatible with molecular systems. a new deep neural network architecture, molecular configuration transformer ( molecular ct ), is introduced for this purpose. molecular ct is composed of a relation - aware encoder module and a computationally universal geometry learning unit, thus able to account for the relational constraints between particles meanwhile scalable to different particle numbers and invariant with respect to the trans - rotational transforms. the computational efficiency and universality make molecular ct versatile for a variety of molecular learning scenarios and especially appealing for transferable representation learning across different molecular systems. as examples, we show that molecular ct enables representational learning for molecular systems at different scales, and achieves comparable or improved results on common benchmarks using a more light - weighted structure compared to baseline models.
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arxiv:2012.11816
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regular functions of infinite words are ( partial ) functions realized by deterministic two - way transducers with infinite look - ahead. equivalently, alur et. al. have shown that they correspond to functions realized by deterministic muller streaming string transducers, and to functions defined by mso - transductions. regular functions are however not computable in general ( for a classical extension of turing computability to infinite inputs ), and we consider in this paper the class of deterministic regular functions of infinite words, realized by deterministic two - way transducers without look - ahead. we prove that it is a well - behaved class of functions : they are computable, closed under composition, characterized by the guarded fragment of mso - transductions, by deterministic b \ " uchi streaming string transducers, by deterministic two - way transducers with finite look - ahead, and by finite compositions of sequential functions and one fixed basic function called map - copy - reverse.
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arxiv:2302.06672
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recently we have used spectroscopic mapping with the scanning tunneling microscope to probe modulations of the electronic density of states in single crystals of the high temperature superconductor bi2sr2cacu2o8 + d ( bi - 2212 ) as a function of temperature [ c. v. parker et al., nature ( london ) 468, 677 ( 2010 ) ]. these measurements showed cu - o bond - oriented modulations that form below the pseudogap temperature with a temperature - dependent energy dispersion displaying different behaviors in the superconducting and pseudogap states. here we demonstrate that quasiparticle scattering off impurities does not capture the experimentally observed energy - and temperature - dependence of these modulations. instead, a model of scattering of quasiparticles from short - range stripe order, with periodicity near four lattice constants ( 4a ), reproduces the experimentally observed energy dispersion of the bond - oriented modulations and its temperature dependence across the superconducting critical temperature, tc. the present study confirms the existence of short - range stripe order in bi - 2212.
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arxiv:1111.2564
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modern communication systems need to fulfill multiple and often conflicting objectives at the same time. in particular, new applications require high reliability while operating at low transmit powers. moreover, reliability constraints may vary over time depending on the current state of the system. one solution to address this problem is to use joint transmissions from a number of base stations ( bss ) to meet the reliability requirements. however, this approach is inefficient when considering the overall total transmit power. in this work, we propose a reinforcement learning - based power allocation scheme for an unmanned aerial vehicle ( uav ) communication system with varying communication reliability requirements. in particular, the proposed scheme aims to minimize the total transmit power of all bss while achieving an outage probability that is less than a tolerated threshold. this threshold varies over time, e. g., when the uav enters a critical zone with high - reliability requirements. our results show that the proposed learning scheme uses dynamic power allocation to meet varying reliability requirements, thus effectively conserving energy.
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arxiv:2312.04742
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we have studied the thermodynamic properties of single - crystalline tbfe3 ( bo3 ) 4. magnetization measurements have been carried out as a function of magnetic field ( up to 50 t ) and temperature up to 350k with the magnetic field both parallel and perpendicular to the trigonal c - axis of the crystal. the specific heat has been measured in the temperature range 2 - 300k with a magnetic field up to 9 t applied parallel to the c - axis. the data indicate a structural phase transition at 192 k and antiferromagnetic spin ordering at 40 k. a schottky anomaly is present in the specific heat data around 20 k, arising due to two low - lying energy levels of the tb3 + ions being split by f - d coupling. below tn magnetic fields parallel to the c - axis drive a spin - flop phase transition, which is associated with a large magnetization jump. the highly anisotropic character of the magnetic susceptibility is ascribed mainly to the ising - like behavior of the tb3 + ions in the trigonal crystal field. we describe our results in the framework of an unified approach which is based on mean - field approximation and crystal - field calculations.
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arxiv:0704.3041
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we consider extensions of the standard model based on open strings ending on d - branes, with gauge bosons due to strings attached to stacks of d - branes and chiral matter due to strings stretching between intersecting d - branes. assuming that the fundamental string mass scale is in the tev range and the theory is weakly coupled, we discuss possible signals of string physics at the large hadron collider ( lhc ). in previous works, direct channel excitations of regge recurrences in parton - parton scattering supplied the outstanding new signature. the present work considers the deviation from standard model expectations for the 4 - fermion processes qq \ to qq and qq ' \ to qq ', in which the s - channel excitation of string resonances is absent. in this case, we find that kaluza - klein recurrences at masses somewhat less than the string scale generate effective 4 - fermion contact terms which can significantly enhance the dijet r ratio above its qcd value of about 0. 6. the simultaneous observation of a nearby resonant structure in the dijet mass spectrum would provide a " smoking gun " for tev scale string theory. in this work, we also show that ( 1 ) for m _ { string } < 3. 5 tev, the rates for various topologies arising from the pp \ to z ^ 0 + jet channel could deviate significantly from standard model predictions and ( 2 ) that the sizeable cross sections for regge recurrences can allow a 6 \ sigma discovery for string scales as large as 3 tev after about 1 year of lhc operation at \ sqrt { s } = 10 tev and \ int l dt ~ 100 pb ^ { - 1 }.
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arxiv:0904.3547
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this paper analyzes a revised fragile watermarking scheme proposed by botta et al. which was developed as a revision of the watermarking scheme previously proposed by rawat et al. a new attack is presented that allows an attacker to apply a valid watermark on tampered images, therefore circumventing the protection that the watermarking scheme under study was supposed to offer. furthermore, the presented attack has very low computational and memory requirements.
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arxiv:1504.05226
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a sample of the brightest point - like sources observed with the rosat - hri were analysed to asses on the intrinsic shape of the rosat - hri point spread function ( psf ). almost all of the hri observations collected during the rosat lifetime are found to be artificially broadened by factors up two ~ 2 due to residual errors in the rosat aspect solution. after correction by departing pointing positions, the width of the core of the psf is found to be less than 5 arcsec ( half energy width, hew ). on the basis of these results, an improved analytical representation of the rosat - hri psf is provided. however, for most of the new observations the source countrate is too weak to allow reliable recovering pf the rosat - hri resolution. therefore, a series of examples ( data, correction, and theoretical psf ) are given in order to help the rosat user in determining whether " his / her source " is extended or not.
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arxiv:astro-ph/0109542
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the model for orr - - sommerfeld equation with quadratic profile on the finite interval is considered. the behavior of the spectrum of this problem is completely investigated for large reynolds numbers. the limit curves are found to which the eigenvalues concentrate and the counting eigenvalue functions along these curves are obtained.
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arxiv:math-ph/0212074
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the heisenberg limit to laser coherence $ \ mathfrak { c } $ - - the number of photons in the maximally populated mode of the laser beam - - is the fourth power of the number of excitations inside the laser. we generalize the previous proof of this upper bound scaling by dropping the requirement that the beam photon statistics be poissonian ( i. e., mandel ' s $ q = 0 $ ). we then show that the relation between $ \ mathfrak { c } $ and sub - poissonianity ( $ q < 0 $ ) is win - win, not a tradeoff. for both regular ( non - markovian ) pumping with semi - unitary gain ( which allows $ q \ xrightarrow { } - 1 $ ), and random ( markovian ) pumping with optimized gain, $ \ mathfrak { c } $ is maximized when $ q $ is minimized.
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arxiv:2208.14081
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recently, magnetic reconnection during collisionless, stressed, x - point collapse was studied using kinetic, 2. 5d, fully electromagnetic, relativistic particle - in - cell numerical code [ d. tsiklauri and t. haruki, phys. plasmas, 14, 112905 ( 2007 ) ]. here we finalise the investigation of this topic by addressing key outstanding physical questions. it has been established here that : ( i ) reconnection out - of - plane electric field at the magnetic null is generated by the electron pressure tensor off - diagonal terms, resembling to the case of tearing unstable harris current sheet studied by the gem reconnection challenge ; ( ii ) for m _ i / m _ e > > 1 the time evolution of the reconnected flux is independent of ion - electron mass ratio ; also, in the case of m _ i / m _ e = 1 we show that reconnection proceeds slowly as the hall term is zero ; when m _ i / m _ e > > 1 ( i. e. the hall term is non - zero ) reconnection is fast and we conjecture that this is due to magnetic field being frozen into electron fluid, which moves significantly faster than ion fluid ; ( iii ) within one alfven time, somewhat less than half ( 40 % ) of the initial total ( roughly magnetic ) energy is converted into the kinetic energy of electrons, and somewhat more than half ( 60 % ) into kinetic energy of ions ( similar to solar flare observations ) ; ( iv ) in the strongly stressed x - point case, in about one alfven time, a full isotropy in all three spatial directions of the velocity distribution is seen for super - thermal electrons ( also commensurate to solar flare observations ).
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arxiv:0807.3252
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in this paper, we establish the well - posedness for the third grade fluid equation perturbed by a multiplicative white noise. this equation describes the motion of a non - newtonian fluid of differential type with relevant viscoelastic properties. we are faced with a strongly nonlinear stochastic partial differential equation supplemented with a navier slip boundary condition. taking the initial condition in the sobolev space h ^ 2, we show the existence and the uniqueness of the strong ( in the probability sense ) solution in a two dimensional and non axisymmetric bounded domain.
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arxiv:2103.06791
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tasks cannot be done with standard footwear. the uses include vibrating of the smart phone to tell users when and where to turn to reach their destination via google maps or self - lacing. self - lacing sneaker technology, similar to the nike mag in back to the future part ii, is another use of the smart shoe. in 2019 german footwear company puma was recognized as one of the " 100 best inventions of 2019 " by time for its fi laceless shoe that uses micro - motors to adjust the fit from an iphone. nike also introduced a smart shoe in 2019 known as adapt bb. the shoe featured buttons on the side to loosen or tighten the fit with a custom motor and gear, which could also be controlled by a smartphone. = = modern technologies = = on april 16, 2013, google invited " glass explorers " who had pre - ordered its wearable glasses at the 2012 google i / o conference to pick up their devices. this day marked the official launch of google glass, a device intended to deliver rich text and notifications via a heads - up display worn as eyeglasses. the device also had a 5 mp camera and recorded video at 720p. its various functions were activated via voice command, such as " ok glass ". the company also launched the google glass companion app, myglass. the first third - party google glass app came from the new york times, which was able to read out articles and news summaries. however, in early 2015, google stopped selling the beta " explorer edition " of glass to the public, after criticism of its design and the $ 1, 500 price tag. while optical head - mounted display technology remains a niche, two popular types of wearable devices have taken off : smartwatches and activity trackers. in 2012, abi research forecast that sales of smartwatches would hit $ 1. 2 million in 2013, helped by the high penetration of smartphones in many world markets, the wide availability and low cost of mems sensors, energy efficient connectivity technologies such as bluetooth 4. 0, and a flourishing app ecosystem. crowdfunding - backed start - up pebble reinvented the smartwatch in 2013, with a campaign running on kickstarter that raised more than $ 10m in funding. at the end of 2014, pebble announced it had sold a million devices. in early 2015, pebble went back to its crowdfunding roots to raise a further $ 20m for its next - generation smartwatch, pebble time,
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https://en.wikipedia.org/wiki/Wearable_technology
|
webs are planar graphs with boundary that describe morphisms in a diagrammatic representation category for $ \ mathfrak { sl } _ k $. they are studied extensively by knot theorists because braiding maps provide a categorical way to express link diagrams in terms of webs, producing quantum invariants like the well - known jones polynomial. one important question in representation theory is to identify the relationships between different bases ; coefficients in the change - of - basis matrix often describe combinatorial, algebraic, or geometric quantities ( like, e. g., kazhdan - lusztig polynomials ). by " flattening " the braiding maps, webs can also be viewed as the basis elements of a symmetric - group representation. in this paper, we define two new combinatorial structures for webs : band diagrams and their one - dimensional projections, shadows, that measure depths of regions inside the web. as an application, we resolve an open conjecture that the change - of - basis between the so - called specht basis and web basis of this symmetric - group representation is unitriangular for $ \ mathfrak { sl } _ 3 $ - webs. we do this using band diagrams and shadows to construct a new partial order on webs that is a refinement of the usual partial order. in fact, we prove that for $ \ mathfrak { sl } _ 2 $ - webs, our new partial order coincides with the tableau partial order on webs studied by the authors and others. we also prove that though the new partial order for $ \ mathfrak { sl } _ 3 $ - webs is a refinement of the previously - studied tableau order, the two partial orders do not agree for $ \ mathfrak { sl } _ 3 $.
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arxiv:2006.09491
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combinatorial optimization problems on graphs have broad applications in science and engineering. the quantum approximate optimization algorithm ( qaoa ) is a method to solve these problems on a quantum computer by applying multiple rounds of variational circuits. however, there exist several challenges limiting the real - world applications of qaoa. in this paper, we demonstrate on a trapped - ion quantum computer that qaoa results improve with the number of rounds for multiple problems on several arbitrary graphs. we also demonstrate an advanced mixing hamiltonian that allows sampling of all optimal solutions with predetermined weights. our results are a step towards applying quantum algorithms to real - world problems.
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arxiv:2201.12335
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we use electron transport to characterize monolayer graphene - multilayer mos2 heterostructures. our samples show ambipolar characteristics and conductivity saturation on the electron branch which signals the onset of mos2 conduction band population. surprisingly, the carrier density in graphene decreases with gate bias once mos2 is populated, demonstrating negative compressibility in mos2. we are able to interpret our measurements quantitatively by accounting for disorder and using the random phase approximation ( rpa ) for the exchange and correlation energies of both dirac and parabolic - band two - dimensional electron gases. this interpretation allows us to extract the energetic offset between the conduction band edge of mos2 and the dirac point of graphene.
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arxiv:1402.1981
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we present a theory of generation of strong ( sub - equipartition ) magnetic fields in relativistic collisionless grb shocks. these fields produced by the kinetic two - stream instability are tangled on very small spatial scales. this has a clear signature in the otherwise synchrotron ( - self - compton ) $ \ gamma $ - ray spectrum. second, we present an analytical theory of jitter radiation, which is emitted when the correlation length of the magnetic field is smaller then the gyration ( larmor ) radius of the accelerated electrons. we demonstrate that the spectral power $ p ( \ nu ) $ for pure jitter radiation is well - described by a sharply broken power - law : $ p ( \ nu ) \ propto \ nu ^ 1 $ for $ \ nu < \ nu _ j $ and $ p ( \ nu ) \ propto \ nu ^ { - ( p - 1 ) / 2 } $ for $ \ nu > \ nu _ j $, where $ p $ is the electron power - law index and $ \ nu _ j $ is the jitter break, which is independent of the magnetic field strength and depends on the shock energetics and kinematics. here we mostly focus on the first problem. the radiation theory and comparison with observations will be discussed in the forthcoming publications.
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arxiv:astro-ph/0102399
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the internet - of - things ( iot ) is an emerging and cognitive technology which connects a massive number of smart physical devices with virtual objects operating in diverse platforms through the internet. iot is increasingly being implemented in distributed settings, making footprints in almost every sector of our life. unfortunately, for healthcare systems, the entities connected to the iot networks are exposed to an unprecedented level of security threats. relying on a huge volume of sensitive and personal data, iot healthcare systems are facing unique challenges in protecting data security and privacy. although blockchain has posed to be the solution in this scenario thanks to its inherent distributed ledger technology ( dlt ), it suffers from major setbacks of increasing storage and computation requirements with the network size. this paper proposes a holochain - based security and privacy - preserving framework for iot healthcare systems that overcomes these challenges and is particularly suited for resource constrained iot scenarios. the performance and thorough security analyses demonstrate that a holochain - based iot healthcare system is significantly better compared to blockchain and other existing systems.
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arxiv:2103.01322
|
the missile technology control regime ( mtcr ) is a multilateral export control regime. it is an informal political understanding among 35 member states that seek to limit the proliferation of missiles and missile technology. the regime was formed in 1987 by the g - 7 industrialized countries. the mtcr seeks to limit the risks of proliferation of weapons of mass destruction ( wmd ) by controlling exports of goods and technologies that could make a contribution to delivery systems ( other than manned aircraft ) for such weapons. in this context, the mtcr places particular focus on rockets and unmanned aerial vehicles capable of delivering a payload of at least 500 kilograms ( 1, 100 lb ) to a range of at least 300 kilometres ( 190 mi ) and on equipment, software, and technology for such systems. the mtcr is not a treaty and does not impose any legally binding obligations on partners ( members ). rather, it is an informal political understanding among states that seek to limit the proliferation of missiles and missile technology. = = guidelines and the equipment, software and technology annex = = the regime ’ s documents include the mtcr guidelines and the equipment, software and technology annex. the guidelines define the purpose of the mtcr and provide the overall structure and rules to guide the member countries and those adhering unilaterally to the guidelines. the equipment, software and technology annex is designed to assist in implementing export controls on mtcr annex items. the annex is divided into “ category i ” and “ category ii ” items. it includes a broad range of equipment and technology, both military and dual - use, that are relevant to missile development, production, and operation. partner countries exercise restraint in the consideration of all transfers of items contained in the annex. all such transfers are considered on a case by case basis. greatest restraint is applied to what are known as category i items. these items include complete rocket systems ( including ballistic missiles, space launch vehicles and sounding rockets ) and unmanned air vehicle systems ( including cruise missiles systems, target and reconnaissance drones ) with capabilities exceeding a 300km / 500kg range / payload threshold ; production facilities for such systems ; and major sub - systems including rocket stages, re - entry vehicles, rocket engines, guidance systems and warhead mechanisms. the remainder of the annex is regarded as category ii, which includes complete rocket systems ( including ballistic missiles systems, space launch vehicles and sounding rockets ) and unmanned air vehicles ( including cruise missile systems, target drones, and reconnaissance drones ) not covered in item i, capable of a maximum range equal to or greater than,
|
https://en.wikipedia.org/wiki/Missile_Technology_Control_Regime
|
the current status of the determinations of the ckm elements vub and vcb is reviewed and future prospects are discussed.
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arxiv:hep-ex/0610059
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based on direct numerical simulations and symmetry arguments, we show that the large - scale fourier modes are useful tools to describe the flow structures and dynamics of flow reversals in rayleigh - b \ ' enard convection ( rbc ). we observe that during the reversals, the amplitude of one of the large - scale modes vanishes, while another mode rises sharply, very similar to the " cessation - led " reversals observed earlier in experiments and numerical simulations. we find anomalous fluctuations in the nusselt number during the reversals. using the structures of the rbc equations in the fourier space, we deduce two symmetry transformations that leave the equations invariant. these symmetry transformations help us in identifying the reversing and non - reversing fourier modes.
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arxiv:1103.4106
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advancements in reinforcement learning ( rl ) have demonstrated superhuman performance in complex tasks such as starcraft, go, chess etc. however, knowledge transfer from artificial " experts " to humans remain a significant challenge. a promising avenue for such transfer would be the use of curricula. recent methods in curricula generation focuses on training rl agents efficiently, yet such methods rely on surrogate measures to track student progress, and are not suited for training robots in the real world ( or more ambitiously humans ). in this paper, we introduce a method named parameterized environment response model ( perm ) that shows promising results in training rl agents in parameterized environments. inspired by item response theory, perm seeks to model difficulty of environments and ability of rl agents directly. given that rl agents and humans are trained more efficiently under the " zone of proximal development ", our method generates a curriculum by matching the difficulty of an environment to the current ability of the student. in addition, perm can be trained offline and does not employ non - stationary measures of student ability, making it suitable for transfer between students. we demonstrate perm ' s ability to represent the environment parameter space, and training with rl agents with perm produces a strong performance in deterministic environments. lastly, we show that our method is transferable between students, without any sacrifice in training quality.
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arxiv:2306.13028
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gw170817 represents the first observed binary neutron star merger event by humanity. the observation of gw170817 has identified the correlation between kilonova, gravitational wave and short grb. the shocks from gw170817 have the capacity to inject significant thermal and kinetic energies into the interstellar medium and evolve for over a million years. in this letter, we adopt the special relativity fluid dynamics equations to simulate the evolution of the gw170817 remnant over a span of one million years. our simulations yield the evolution profiles of the velocity, density, mass, radius, luminosity, and energies of the remnant. we estimate that the gw170817 remnant will reach the average maximum luminosity $ 2. 56 \ times 10 ^ { 39 } $ erg s $ ^ { - 1 } $ at approximately $ 3. 96 \ times 10 ^ 4 $ yr. at the end of the cooling stage, the contaminated radius and mass are $ 48. 35 $ pc and $ 2. 25 \ times 10 ^ 4 m _ { \ odot } $, respectively.
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arxiv:2403.08223
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known as polytechnic universities ) with 5 years of study legally equivalent to bachelor ' s and master ' s degree 300 ects, isced 7 and has the full professional rights of the engineer. and had technological educational institutes ( teis ) ( 1982 – 2019 ) also known as higher educational institute of technology, technological institute, institute of technology ( provides at least 4 - year undergraduate degree qualification πτυχιο, latinised version : ptychion, in line with the bologna process legally equivalent to bachelor ' s honours degree 240 ects, isced 6. previously it was three and a half years studies from 1983 to 1995, 210 ects ). all the technical universities and technological educational institutes are higher education institutions ( heis ) with university title ( ut ) and degree awarding powers ( daps ). teis existed from 1983 to 2019 ; they were reformed between 2013 and 2019 and their departments incorporated into existing higher education institutions ( heis ). the two polytechnic universities ( technical universities ) in greece ( greek : πολυτεχνειο ) are the national technical university of athens and the technical university of crete. however, many other universities have a faculty of engineering that provides an equivalent diploma of engineerings with an integrated master and the full professional rights as well. many teis that got dismantled created engineering faculty with 5 years of study and 300 ects, isced 6. but those faculty are not under the general term of polytechnics nor they have an integrated master ' s degree yet waiting evaluation to be characterised as equivalent. these have been named school of engineers for the time being and not technical universities or polytechnic. in greece, all higher education institutions ( heis ) are public university owned and government - funded, with free education undergraduate programmes that can be attended without any payment of tuition fee. about 1 out of 4 ( one - fourth of ) heis postgraduate programmes are offered free without any payment of tuition fee, especially about a 30 % percentage of students can be entitled without tuition fee to attend all the heis statutory tuition fee postgraduate programmes after they be assessed on an individual basis of determined criteria as set out in the ministry of education. = = = hong kong = = = the first polytechnic in hong kong is the hong kong polytechnic, established in 1972 through upgrading the hong kong technical college ( government trade school before 1947 ). the second polytechnic, the city polytechnic of hong kong, was founded in 1984. these polytechnics awards diplomas, higher diplomas, as well as academic degrees. like the
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https://en.wikipedia.org/wiki/Institute_of_technology
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the recently introduced continuous skip - gram model is an efficient method for learning high - quality distributed vector representations that capture a large number of precise syntactic and semantic word relationships. in this paper we present several extensions that improve both the quality of the vectors and the training speed. by subsampling of the frequent words we obtain significant speedup and also learn more regular word representations. we also describe a simple alternative to the hierarchical softmax called negative sampling. an inherent limitation of word representations is their indifference to word order and their inability to represent idiomatic phrases. for example, the meanings of " canada " and " air " cannot be easily combined to obtain " air canada ". motivated by this example, we present a simple method for finding phrases in text, and show that learning good vector representations for millions of phrases is possible.
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arxiv:1310.4546
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we study new cohomologies for the bps operators of the $ \ mathcal { n } = 4 $ yang - mills theory with $ su ( 3 ) $ and $ su ( 4 ) $ gauge groups, to better understand the black hole microstates. we first study the index of these black hole operators and identify their apparent threshold levels. for $ su ( 3 ) $, we find many towers of states and partial no - hair behaviors. we explicitly construct the threshold cohomology in the $ su ( 3 ) $ theory. we study throughout this paper a subsector of the field theory corresponding to the bmn matrix theory. we also argue that the bmn sector exhibits a black hole like entropy growth at large $ n $.
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arxiv:2312.16443
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generative modelling paradigms based on denoising diffusion processes have emerged as a leading candidate for conditional sampling in inverse problems. in many real - world applications, we often have access to large, expensively trained unconditional diffusion models, which we aim to exploit for improving conditional sampling. most recent approaches are motivated heuristically and lack a unifying framework, obscuring connections between them. further, they often suffer from issues such as being very sensitive to hyperparameters, being expensive to train or needing access to weights hidden behind a closed api. in this work, we unify conditional training and sampling using the mathematically well - understood doob ' s h - transform. this new perspective allows us to unify many existing methods under a common umbrella. under this framework, we propose deft ( doob ' s h - transform efficient finetuning ), a new approach for conditional generation that simply fine - tunes a very small network to quickly learn the conditional $ h $ - transform, while keeping the larger unconditional network unchanged. deft is much faster than existing baselines while achieving state - of - the - art performance across a variety of linear and non - linear benchmarks. on image reconstruction tasks, we achieve speedups of up to 1. 6 $ \ times $, while having the best perceptual quality on natural images and reconstruction performance on medical images. further, we also provide initial experiments on protein motif scaffolding and outperform reconstruction guidance methods.
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arxiv:2406.01781
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we present explicit filtration / backprojection - type formulae for the inversion of the spherical ( circular ) mean transform with the centers lying on the boundary of some polyhedra ( or polygons, in 2d ). the formulae are derived using the double layer potentials for the wave equation, for the domains with certain symmetries. the formulae are valid for a rectangle and certain triangles in 2d, and for a cuboid, certain right prisms and a certain pyramid in 3d. all the present inversion formulae yield exact reconstruction within the domain surrounded by the acquisition surface even in the presence of exterior sources.
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arxiv:1009.0288
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recent advances in cross - lingual word embeddings have primarily relied on mapping - based methods, which project pretrained word embeddings from different languages into a shared space through a linear transformation. however, these approaches assume word embedding spaces are isomorphic between different languages, which has been shown not to hold in practice ( s { \ o } gaard et al., 2018 ), and fundamentally limits their performance. this motivates investigating joint learning methods which can overcome this impediment, by simultaneously learning embeddings across languages via a cross - lingual term in the training objective. we propose a bilingual extension of the cbow method which leverages sentence - aligned corpora to obtain robust cross - lingual word and sentence representations. our approach significantly improves cross - lingual sentence retrieval performance over all other approaches while maintaining parity with the current state - of - the - art methods on word - translation. it also achieves parity with a deep rnn method on a zero - shot cross - lingual document classification task, requiring far fewer computational resources for training and inference. as an additional advantage, our bilingual method leads to a much more pronounced improvement in the the quality of monolingual word vectors compared to other competing methods.
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arxiv:1912.12481
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class imbalance and group ( e. g., race, gender, and age ) imbalance are acknowledged as two reasons in data that hinder the trade - off between fairness and utility of machine learning classifiers. existing techniques have jointly addressed issues regarding class imbalance and group imbalance by proposing fair over - sampling techniques. unlike the common oversampling techniques, which only address class imbalance, fair oversampling techniques significantly improve the abovementioned trade - off, as they can also address group imbalance. however, if the size of the original clusters is too small, these techniques may cause classifier overfitting. to address this problem, we herein develop a fair oversampling technique using data from heterogeneous clusters. the proposed technique generates synthetic data that have class - mix features or group - mix features to make classifiers robust to overfitting. moreover, we develop an interpolation method that can enhance the validity of generated synthetic data by considering the original cluster distribution and data noise. finally, we conduct experiments on five realistic datasets and three classifiers, and the experimental results demonstrate the effectiveness of the proposed technique in terms of fairness and utility.
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arxiv:2305.13875
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in this paper, we investigate the asymptotic behaviors of the survival probability and maximal displacement of a subcritical branching killed spectrally negative l \ ' { e } vy process $ x $ in $ \ mathbb { r } $. let $ \ zeta $ denote the extinction time, $ m _ t $ be the maximal position of all the particles alive at time $ t $, and $ m : = \ sup _ { t \ ge 0 } m _ t $ be the all - time maximum. under the assumption that the offspring distribution satisfies the $ l \ log l $ condition and some conditions on the spatial motion, we find the decay rate of the survival probability $ \ mathbb { p } _ x ( \ zeta > t ) $ and the tail behavior of $ m _ t $ as $ t \ to \ infty $. as a consequence, we establish a yaglom - type theorem. we also find the asymptotic behavior of $ \ mathbb { p } _ x ( m > y ) $ as $ y \ to \ infty $.
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arxiv:2503.03580
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