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we study chaotic dynamics in two - dimensional conformal field theory through out - of - time order thermal correlators of the form $ \ langle w ( t ) vw ( t ) v \ rangle $. we reproduce bulk calculations similar to those of [ 1 ], by studying the large $ c $ virasoro identity block. the contribution of this block to the above correlation function begins to decrease exponentially after a delay of $ \ sim t _ * - \ frac { \ beta } { 2 \ pi } \ log \ beta ^ 2e _ w e _ v $, where $ t _ * $ is the scrambling time $ \ frac { \ beta } { 2 \ pi } \ log c $, and $ e _ w, e _ v $ are the energy scales of the $ w, v $ operators.
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arxiv:1412.5123
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recent neural network models for algorithmic tasks have led to significant improvements in extrapolation to sequences much longer than training, but it remains an outstanding problem that the performance still degrades for very long or adversarial sequences. we present alternative architectures and loss - terms to address these issues, and our testing of these approaches has not detected any remaining extrapolation errors within memory constraints. we focus on linear time algorithmic tasks including copy, parentheses parsing, and binary addition. first, activation binning was used to discretize the trained network in order to avoid computational drift from continuous operations, and a binning - based digital loss term was added to encourage discretizable representations. in addition, a localized differentiable memory ( ldm ) architecture, in contrast to distributed memory access, addressed remaining extrapolation errors and avoided unbounded growth of internal computational states. previous work has found that algorithmic extrapolation issues can also be alleviated with approaches relying on program traces, but the current effort does not rely on such traces.
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arxiv:2003.08494
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or may be published separately. some users are satisfied with the bundled apps and need never install additional applications. the system software manages the hardware and serves the application, which in turn serves the user. application software applies the power of a particular computing platform or system software to a particular purpose. some apps, such as microsoft office, are developed in multiple versions for several different platforms ; others have narrower requirements and are generally referred to by the platform they run on. for example, a geography application for windows or an android application for education or linux gaming. applications that run only on one platform and increase the desirability of that platform due to the popularity of the application, known as killer applications. = = = computer network = = = a computer network, often simply referred to as a network, is a collection of hardware components and computers interconnected by communication channels that allow the sharing of resources and information. when at least one process in one device is able to send or receive data to or from at least one process residing in a remote device, the two devices are said to be in a network. networks may be classified according to a wide variety of characteristics such as the medium used to transport the data, communications protocol used, scale, topology, and organizational scope. communications protocols define the rules and data formats for exchanging information in a computer network, and provide the basis for network programming. one well - known communications protocol is ethernet, a hardware and link layer standard that is ubiquitous in local area networks. another common protocol is the internet protocol suite, which defines a set of protocols for internetworking, i. e. for data communication between multiple networks, host - to - host data transfer, and application - specific data transmission formats. computer networking is sometimes considered a sub - discipline of electrical engineering, telecommunications, computer science, information technology, or computer engineering, since it relies upon the theoretical and practical application of these disciplines. = = = = internet = = = = the internet is a global system of interconnected computer networks that use the standard internet protocol suite ( tcp / ip ) to serve billions of users. this includes millions of private, public, academic, business, and government networks, ranging in scope from local to global. these networks are linked by a broad array of electronic, wireless, and optical networking technologies. the internet carries an extensive range of information resources and services, such as the inter - linked hypertext documents of the world wide web and the infrastructure to support email. = = = computer programming = = = computer programming is the process of writing
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https://en.wikipedia.org/wiki/Computing
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in multi - phase fluid flow, fluid - structure interaction, and other applications, partial differential equations ( pdes ) often arise with discontinuous coefficients and singular sources ( e. g., dirac delta functions ). these complexities arise due to changes in material properties at an immersed interface or embedded boundary, which may have an irregular shape. consequently, the solution and its gradient can be discontinuous, and numerical methods can be difficult to design. here a new method is presented and analyzed, using a simple formulation of one - dimensional finite differences on a cartesian grid, allowing for a relatively easy setup for one -, two -, or three - dimensional problems. the method preserves a sharp interface with discontinuous solutions, obtained from a small number of iterations ( approximately five ) of solving a symmetric linear system with updates to the right - hand side. second - order accuracy is rigorously proven in one spatial dimension and demonstrated through numerical examples in two and three spatial dimensions. the method is tested here on the variable - coefficient poisson equation, and it could be extended for use on time - dependent problems of heat transfer, fluid dynamics, or other applications.
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arxiv:1806.10593
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in this paper we outline the application of decomposition to condensation defects and their fusion rules. briefly, a condensation defect is obtained by gauging a higher - form symmetry along a submanifold, and so there is a natural interplay with notions of decomposition, the statement that d - dimensional quantum field theories with global ( d - 1 ) - form symmetries are equivalent to disjoint unions of other quantum field theories. we will also construct new ( sometimes non - invertible ) defects, and compute their fusion products, again utilizing decomposition. an important role will be played in all these analyses by theta angles for gauged higher - form symmetries, which can be used to select individual universes in a decomposition.
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arxiv:2208.05982
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in this letter, as a proof of concept, we propose a deep learning - based approach to attack the chaos - based image encryption algorithm in \ cite { guan2005chaos }. the proposed method first projects the chaos - based encrypted images into the low - dimensional feature space, where essential information of plain images has been largely preserved. with the low - dimensional features, a deconvolutional generator is utilized to regenerate perceptually similar decrypted images to approximate the plain images in the high - dimensional space. compared with conventional image encryption attack algorithms, the proposed method does not require to manually analyze and infer keys in a time - consuming way. instead, we directly attack the chaos - based encryption algorithms in a key - independent manner. moreover, the proposed method can be trained end - to - end. given the chaos - based encrypted images, a well - trained decryption model is able to automatically reconstruct plain images with high fidelity. in the experiments, we successfully attack the chaos - based algorithm \ cite { guan2005chaos } and the decrypted images are visually similar to their ground truth plain images. experimental results on both static - key and dynamic - key scenarios verify the efficacy of the proposed method.
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arxiv:1907.12245
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here we report mid infrared ( mid - ir ) photothermal response of multi layer mos2 thin film grown on crystalline ( p - type silicon and c - axis oriented single crystal sapphire ) and amorphous substrates ( si / sio2 and si / sin ) by pulsed laser deposition ( pld ) technique. the photothermal response of the mos2 films was measured as changes in the resistance of mos2 films when irradiated with mid ir ( 7 to 8. 2 { \ mu } m ) source. we show that it is possible to enhance the temperature coefficient of resistance ( tcr ) of the mos2 thin film by controlling the interface through proper choice of substrate and growth conditions. the thin films grown by pld were characterized using xrd, raman, afm, xps and tem. high - resolution transmission electron microscopy ( hrtem ) images show that the mos2 films grow on sapphire substrate in a layer - by - layer manner with misfit dislocations. layer growth morphology is disrupted when grown on substrates with diamond cubic structure such as silicon due to growth twin formation. the growth morphology is very different on amorphous substrates such as si / sio2 or si / sin. the mos2 film grown on silicon shows a very high tcr ( - 2. 9 % k - 1 ), mid ir sensitivity ( delr / r = 5. 2 % ) and responsivity ( 8. 7 v / w ) as compared to films on other substrates.
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arxiv:1607.04682
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we present multi - color photometry and time resolved spectroscopy of ou vir. the analysis of the quiescent light curve shows that ou vir is characterized by i ) strong cycle - to - cycle brightness variations, and ii ) hot spot modulated light curve with grazing eclipse of the impact region. colors are derived both in - and out - of eclipse. the time - resolved spectroscopy allows us to produce the radial velocity curve from the h $ \ alpha $ accretion disk emission line which possibly reveals only weak evidence for hot spot line emission. the hot spot is believed to be a turbulent optically thick region, producing mostly continuum emission.
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arxiv:astro-ph/0210210
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we have investigated the structural and magnetic properties of sm ( co0. 7fe0. 1ni0. 12zr0. 04b0. 04 ) 7. 5 melt spun ribbons. samples were arc melted then melt spun at 37 m / s up to 55 m / s to obtain ribbon for powdering. annealing has been performed in argon atmosphere for ( 30 to 75 ) min at ( 600 to 870 ) oc. in as - spun ribbons the hexagonal smco7 ( tbcu7 - type of structure ) of crystal structure has been determined from x - ray diffraction patterns, while fcc - co has been identified as a secondary phase. after annealing, the 1 : 7 phase of the as - spun ribbons transforms into 2 : 17 and 1 : 5 phases. x - ray patterns for as - milled powders exhibit very broad peaks making it difficult to identify a precise structure but represent the 1 : 7 structure after annealing at low temperature ( 650 oc ). tem analysis shows a homogeneous nanocrystalline microstructure with average grain size of ( 30 to 80 ) nm. coercivity values of ( 15 to 27 ) koe are obtained from hysteresis loops traced up to a field of 5 t. the coercivity decreases as temperature increases, but it maintains values higher than 5 koe at 380 oc. the maximum energy product at room temperature increases, as high as 7. 2 mgoe, for melt - spun isotropic ribbons produced at higher wheel speeds. anisotropic ribbons have a maximum energy product close to 12 mgoe.
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arxiv:1112.5334
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consider a piecewise smooth expanding map of the interval possessing several invariant subintervals and the same number of ergodic absolutely continuous invariant probability measures ( acims ). after this system is perturbed to make the subintervals lose their invariance in such a way that there is a unique acim, we show how to approximate the diffusion coefficient for an observable of bounded variation by the diffusion coefficient of a related continuous time markov chain.
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arxiv:1011.5330
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streets and tian introduced pluriclosed flow and symplectic curvature flow in recent years. here we construct a curvature flow to unify these two flows. we show the short time existence of our flow and exhibit an obstruction to long time existence.
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arxiv:1311.7191
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we study the interval constants that are related to the motions of the sun and the moon, i. e., the qi, intercalation, revolution, and crossing interval constants, in calendars affiliated with the shoushi calendar ( shoushili ), such as datongli and chiljeongsannaepyeon. it is known that those interval constants were newly introduced in shoushili and revised afterward, except for the qi interval constant, and the revised values were adopted in the shoushili - affiliated calendars. in this paper, we investigate first the accuracy of the interval constants and then the accuracy of the shoushili - affilated calendars in terms of the interval constants by comparing the times of the new moon and the solar eclipse maximum calculated by each calendar with modern calculations. during our study, we found that the qi and intercalation interval constants used in the early shoushili were well determined, whereas the revolution and crossing interval constants were relatively poorly measured. we also found that the interval constants used by the early shoushili were better than those of the later one, and hence than those of datongli and chiljeongsannaepyeon. on the other hand, we found that the early shoushili is, in general, a worse calendar than datongli for use in china but a better one than chiljeongsannaepyeon for use in korea in terms of the new moon and the solar eclipse times, at least for the period 1281 - 1644. finally, we verified that the sunrise and sunset times recorded in shoushili - li - cheng and mingshi are those at beijing and nanjing, respectively.
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arxiv:1311.4735
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motivated by a problem arising when analysing data from quarantine searches, we explore properties of distributions of sums of independent means of independent lattice - valued random variables. the aim is to determine the extent to which approximations to those sums require continuity corrections. we show that, in cases where there are only two different means, the main effects of distribution smoothness can be understood in terms of the ratio $ \ rho _ { 12 } = ( e _ 2n _ 1 ) / ( e _ 1n _ 2 ) $, where $ e _ 1 $ and $ e _ 2 $ are the respective maximal lattice edge widths of the two populations, and $ n _ 1 $ and $ n _ 2 $ are the respective sample sizes used to compute the means. if $ \ rho _ { 12 } $ converges to an irrational number, or converges sufficiently slowly to a rational number ; and in a number of other cases too, for example those where $ \ rho _ { 12 } $ does not converge ; the effects of the discontinuity of lattice distributions are of smaller order than the effects of skewness. however, in other instances, for example where $ \ rho _ { 12 } $ converges relatively quickly to a rational number, the effects of discontinuity and skewness are of the same size. we also treat higher - order properties, arguing that cases where $ \ rho _ { 12 } $ converges to an algebraic irrational number can be less prone to suffer the effects of discontinuity than cases where the limiting irrational is transcendental. these results are extended to the case of three or more different means, and also to problems where distributions are estimated using the bootstrap. the results have practical interpretation in terms of the accuracy of inference for, among other quantities, the sum or difference of binomial proportions.
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arxiv:1309.7752
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we show how intrinsic material properties modify light transmission through subwavelength hole arrays on thin metallic films in the thz regime. we compare the temperature - dependent transmittance of au films and mgb $ _ { 2 } $ films. the experimental data is consistent with analytical calculations, and is attributed to the temperature change of the conductivity of both films. the transmission versus conductivity is interpreted within the open resonator model when taking the skin depth into consideration. we also show that the efficiency of this temperature control depends on the ratio of the transmission peak frequency to the superconducting energy gap in mgb $ _ { 2 } $ films.
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arxiv:1112.0640
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sequential data often possesses a hierarchical structure with complex dependencies between subsequences, such as found between the utterances in a dialogue. in an effort to model this kind of generative process, we propose a neural network - based generative architecture, with latent stochastic variables that span a variable number of time steps. we apply the proposed model to the task of dialogue response generation and compare it with recent neural network architectures. we evaluate the model performance through automatic evaluation metrics and by carrying out a human evaluation. the experiments demonstrate that our model improves upon recently proposed models and that the latent variables facilitate the generation of long outputs and maintain the context.
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arxiv:1605.06069
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united states department of justice report by the tort policy working group noted : the use of such invalid scientific evidence ( commonly referred to as ' junk science ' ) has resulted in findings of causation which simply cannot be justified or understood from the standpoint of the current state of credible scientific or medical knowledge. in 1989, the climate scientist jerry mahlman ( director of the geophysical fluid dynamics laboratory ) characterized the theory that global warming was due to solar variation ( presented in scientific perspectives on the greenhouse problem by frederick seitz et al. ) as " noisy junk science. " peter w. huber popularized the term with respect to litigation in his 1991 book galileo ' s revenge : junk science in the courtroom. the book has been cited in over 100 legal textbooks and references ; as a consequence, some sources cite huber as the first to coin the term. by 1997, the term had entered the legal lexicon as seen in an opinion by supreme court of the united states justice john paul stevens : an example of ' junk science ' that should be excluded under the daubert standard as too unreliable would be the testimony of a phrenologist who would purport to prove a defendant ' s future dangerousness based on the contours of the defendant ' s skull. lower courts have subsequently set guidelines for identifying junk science, such as the 2005 opinion of united states court of appeals for the seventh circuit judge frank h. easterbrook : positive reports about magnetic water treatment are not replicable ; this plus the lack of a physical explanation for any effects are hallmarks of junk science. as the subtitle of huber ' s book, junk science in the courtroom, suggests, his emphasis was on the use or misuse of expert testimony in civil litigation. one prominent example cited in the book was litigation over casual contact in the spread of aids. a california school district sought to prevent a young boy with aids, ryan thomas, from attending kindergarten. the school district produced an expert witness, steven armentrout, who testified that a possibility existed that aids could be transmitted to schoolmates through yet undiscovered " vectors ". however, five experts testified on behalf of thomas that aids is not transmitted through casual contact, and the court affirmed the " solid science " ( as huber called it ) and rejected armentrout ' s argument. in 1999, paul ehrlich and others advocated public policies to improve the dissemination of valid environmental scientific knowledge and discourage junk science : the intergovernmental panel on climate change reports
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https://en.wikipedia.org/wiki/Junk_science
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learning generalizable representation and classifier for class - imbalanced data is challenging for data - driven deep models. most studies attempt to re - balance the data distribution, which is prone to overfitting on tail classes and underfitting on head classes. in this work, we propose dual compensation residual networks to better fit both tail and head classes. firstly, we propose dual feature compensation module ( fcm ) and logit compensation module ( lcm ) to alleviate the overfitting issue. the design of these two modules is based on the observation : an important factor causing overfitting is that there is severe feature drift between training and test data on tail classes. in details, the test features of a tail category tend to drift towards feature cloud of multiple similar head categories. so fcm estimates a multi - mode feature drift direction for each tail category and compensate for it. furthermore, lcm translates the deterministic feature drift vector estimated by fcm along intra - class variations, so as to cover a larger effective compensation space, thereby better fitting the test features. secondly, we propose a residual balanced multi - proxies classifier ( rbmc ) to alleviate the under - fitting issue. motivated by the observation that re - balancing strategy hinders the classifier from learning sufficient head knowledge and eventually causes underfitting, rbmc utilizes uniform learning with a residual path to facilitate classifier learning. comprehensive experiments on long - tailed and class - incremental benchmarks validate the efficacy of our method.
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arxiv:2308.13165
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doped holes in cuprates reside pairwise at lattice - defect o atoms but at different sites in the two cuprate families. in the sr - doped lanthanum cuprates, the o atoms occupy anion lattice sites and spread due to coulomb repulsion ( relative to the host lattice ). in the oxygenated cuprates, the o atoms occupy interstitial sites, hybridize to ozone complexes, and aggregate to strings or ( at high oxygenation ) to nematic patches, always with spacing of ~ 3. 25a _ 0. at the closing of the pseudogap at hole doping p *, a highly symmetric configuration of the o atoms appears in each family. in the first family it consists of interlaced superlattices in the cuo _ 2 plane and each of the bracketing lao layers, with spacing a _ 0 ^ { lao } ( p * ) = 2a _ 0 ^ { cuo _ 2 } ( p * ). in the second family it consists in the completion of a 2d superlattice of ozone complexes, with spacing a _ 0 ( p * ) ~ 3. 25a _ 0. both cases are visualized. implications for the bandstructure and strange - metal phase are considered.
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arxiv:2110.05931
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quantum frequency conversion serves a key role in the realization of hybrid quantum networks by interfacing between wavelength - incompatible platforms. here we present the first quantum frequency converter connecting visible and telecom domains on a silicon nitride ( sin ) chip, using bragg - scattering four - wave mixing to upconvert heralded single photons from 1260 to 698 nm, which covers a 192 thz span. we examine the noise sources in sin and devise approaches to suppress noise photons at the source and target frequencies to enable measurements at the single - photon level. we demonstrate an on - chip conversion efficiency of 5 % in photon flux and describe design modifications that can be implemented to significantly improve it. our results pave the way for the implementation of cmos - compatible devices in quantum networks.
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arxiv:2505.10338
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the quantum entropy cones ( qec ) for $ w _ n $ states of qubits and $ w _ n ^ d $ states of qudits are computed. these cones emerge as symmetrized quantum entropy cones ( sqec ) for arbitrary $ n $ and $ d $. directed graph models are presented which describe the sqec for $ w _ n $ states and $ w _ n ^ d $ states. monogamous mutual information ( mmi ) is violated for all $ n > 3 $.
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arxiv:2204.04532
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it is proved that in a commutative unital banach algebra, every non - maximal closed prime ideal is accessible. specifically, it can be represented as the intersection of all closed ideals of the algebra that properly contain it. consequently, all derivations and epimorphisms on commutative unital semi - prime banach algebras are continuous. moreover, any separating ideal in a commutative unital banach algebra is nilpotent and, therefore, a nil ideal.
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arxiv:2505.04849
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deep anomaly detection models using a supervised mode of learning usually work under a closed set assumption and suffer from overfitting to previously seen rare anomalies at training, which hinders their applicability in a real scenario. in addition, obtaining annotations for x - rays is very time consuming and requires extensive training of radiologists. hence, training anomaly detection in a fully unsupervised or self - supervised fashion would be advantageous, allowing a significant reduction of time spent on the report by radiologists. in this paper, we present salad, an end - to - end deep self - supervised methodology for anomaly detection on x - ray images. the proposed method is based on an optimization strategy in which a deep neural network is encouraged to represent prototypical local patterns of the normal data in the embedding space. during training, we record the prototypical patterns of normal training samples via a memory bank. our anomaly score is then derived by measuring similarity to a weighted combination of normal prototypical patterns within a memory bank without using any anomalous patterns. we present extensive experiments on the challenging nih chest x - rays and mura dataset, which indicate that our algorithm improves state - of - the - art methods by a wide margin.
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arxiv:2010.09856
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dialogue systems capable of social influence such as persuasion, negotiation, and therapy, are essential for extending the use of technology to numerous realistic scenarios. however, existing research primarily focuses on either task - oriented or open - domain scenarios, a categorization that has been inadequate for capturing influence skills systematically. there exists no formal definition or category for dialogue systems with these skills and data - driven efforts in this direction are highly limited. in this work, we formally define and introduce the category of social influence dialogue systems that influence users ' cognitive and emotional responses, leading to changes in thoughts, opinions, and behaviors through natural conversations. we present a survey of various tasks, datasets, and methods, compiling the progress across seven diverse domains. we discuss the commonalities and differences between the examined systems, identify limitations, and recommend future directions. this study serves as a comprehensive reference for social influence dialogue systems to inspire more dedicated research and discussion in this emerging area.
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arxiv:2210.05664
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periodic forcing of an oscillatory system produces frequency locking bands within which the system frequency is rationally related to the forcing frequency. we study extended oscillatory systems that respond to uniform periodic forcing at one quarter of the forcing frequency ( the 4 : 1 resonance ). these systems possess four coexisting stable states, corresponding to uniform oscillations with successive phase shifts of $ \ pi / 2 $. using an amplitude equation approach near a hopf bifurcation to uniform oscillations, we study front solutions connecting different phase states. these solutions divide into two groups : $ \ pi $ - fronts separating states with a phase shift of $ \ pi $ and $ \ pi / 2 $ - fronts separating states with a phase shift of $ \ pi / 2 $. we find a new type of front instability where a stationary $ \ pi $ - front ` ` decomposes ' ' into a pair of traveling $ \ pi / 2 $ - fronts as the forcing strength is decreased. the instability is degenerate for an amplitude equation with cubic nonlinearities. at the instability point a continuous family of pair solutions exists, consisting of $ \ pi / 2 $ - fronts separated by distances ranging from zero to infinity. quintic nonlinearities lift the degeneracy at the instability point but do not change the basic nature of the instability. we conjecture the existence of similar instabilities in higher 2n : 1 resonances ( n = 3, 4,.. ) where stationary $ \ pi $ - fronts decompose into n traveling $ \ pi / n $ - fronts. the instabilities designate transitions from stationary two - phase patterns to traveling 2n - phase patterns. as an example, we demonstrate with a numerical solution the collapse of a four - phase spiral wave into a stationary two - phase pattern as the forcing strength within the 4 : 1 resonance is increased.
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arxiv:patt-sol/9902006
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we study the superstring theory on pp - wave background with nsns - flux that is realized as the penrose limit of ads _ 3 x s ^ 3 x m ^ 4, where m ^ 4 is t ^ 4 or t ^ 4 / z _ 2 ( ~ k3 ). quantizing this system in the covariant gauge, we explicitly construct the space - time supersymmetry algebra and the complete set of ddf operators. we analyse the spectrum of physical states by using the spectrally flowed representations of current algebra. this spectrum is classified by the ` ` short string sectors ' ' and the ` ` long string sectors ' ' as in ads _ 3 string theory. the states of the latter propagate freely along the transverse plane of pp - wave background, but the states of the former do not. we compare the short string spectrum with the bps and almost bps states which have large r - charges in the symmetric orbifold conformal theory, which is known as the candidate of dual theory of superstrings on ads _ 3 x s ^ 3 x m ^ 4. we show that every short string states can be embedded successfully in the single particle hilbert space of symmetric orbifold conformal theory.
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arxiv:hep-th/0205200
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de finetti theorems tell us that if we expect the likelihood of outcomes to be independent of their order, then these sequences of outcomes could be equivalently generated by drawing an experiment at random from a distribution, and repeating it over and over. in particular, the quantum de finetti theorem says that exchangeable sequences of quantum states are always represented by distributions over a single state produced over and over. the main result of this paper is that this quantum de finetti construction has a universal property as a categorical limit. this allows us to pass canonically between categorical treatments of finite dimensional quantum theory and the infinite dimensional. the treatment here is through understanding properties of ( co ) limits with respect to the contravariant functor which takes a c * - algebra describing a physical system to its convex, compact space of states, and through discussion of the radon probability monad. we also show that the same categorical analysis also justifies a continuous de finetti theorem for classical probability.
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arxiv:2207.05832
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as a transient x - ray binary, maxi j1659 - 152 contains a black hole candidate as its compact star. maxi j1659 - 152 was discovered on 2010 september 25 during its only known outburst. previously - published studies of this outburst indicate that maxi j1659 - 152 may have an extreme retrograde spin, which, if confirmed, would provide an important clue as to the origin of black hole spin. in this paper, utilizing updated dynamical binary - system parameters ( i. e. the black hole mass, the orbital inclination and the source distance ) provided by \ cite { torres2021 }, we analyze 65 spectra of maxi j1659 - 152 from \ emph { rxte } / pca, in order to assess the spin parameter. with a final selection of 9 spectra matching our $ f _ { \ mathrm { sc } } \ lesssim 25 \ % $, soft - state criteria, we apply a relativistic thin disk spectroscopic model \ texttt { kerrbb2 } over 3. 0 - 45. 0 kev. we find that inclination angle correlates inversely with spin, and, considering the possible values for inclination angle, we constrain spin to be $ - 1 < a _ { * } \ lesssim 0. 44 $ at 90 \ % confidence interval via x - ray continuum - fitting. we can only rule out an extreme prograde ( positive ) spin. we confirm that an extreme retrograde solution is possible and is not ruled out by considering accretion torques given the young age of the system.
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arxiv:2112.03479
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multivariate functions of continuous variables arise in countless branches of science. numerical computations with such functions typically involve a compromise between two contrary desiderata : accurate resolution of the functional dependence, versus parsimonious memory usage. recently, two promising strategies have emerged for satisfying both requirements : ( i ) the quantics representation, which expresses functions as multi - index tensors, with each index representing one bit of a binary encoding of one of the variables ; and ( ii ) tensor cross interpolation ( tci ), which, if applicable, yields parsimonious interpolations for multi - index tensors. here, we present a strategy, quantics tci ( qtci ), which combines the advantages of both schemes. we illustrate its potential with an application from condensed matter physics : the computation of brillouin zone integrals.
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arxiv:2303.11819
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the mixing of scalar substances in fluid flows by stirring and diffusion is ubiquitous in natural flows, chemical engineering, and microfluidic drug delivery. here, we present a spectral quantum algorithm for scalar mixing by solving the advection - diffusion equation in a quantum computational fluid dynamics framework. we derive exact gate decompositions of the advection and diffusion operators in spectral space. for all but the simplest one - dimensional flows, these operators do not commute. therefore, we use operator splitting and construct quantum circuits capable of simulating arbitrary polynomial velocity profiles, such as the blasius profile of a laminar boundary layer. periodic, neumann, and dirichlet boundary conditions can be imposed with the appropriate quantum spectral transform plus additional constraints on the fourier expansion. we evaluate our approach in statevector simulations of a couette flow, plane poiseuille flow, and a polynomial blasius profile approximation to demonstrate its potential and versatility for scalar mixing in shear flows. the number of gates grows with, at most, the cubed logarithm of the number of grid points. this evaluation shows that spectral accuracy allows comparably large time steps even though the operator splitting limits the temporal order.
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arxiv:2505.10136
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multi - wavelength images from the hubble space telescope covering the wavelength range 0. 27 - 1. 6 $ \ mu $ m show that the central area of the nearby dwarf galaxy ngc4449 contains several tens of compact sources that are emitting in the hydrogen recombination line pa $ \ beta $ ( 1. 2818 $ \ mu $ m ) but are only marginally detected in h $ \ alpha $ ( 0. 6563 $ \ mu $ m ) and undetected at wavelengths $ \ lambda \ le $ 0. 55 $ \ mu $ m. an analysis of the spectral energy distributions ( seds ) of these sources indicates that they are likely relatively young star clusters heavily attenuated by dust. the selection function used to identify the sources prevents meaningful statistical analyses of their age, mass, and dust extinction distributions. however, these cluster candidates have ages $ \ sim $ 5 - 6 myr and a $ _ v > $ 6 mag, according to their sed fits, and are extremely compact, with typical deconvolved radii of 1 pc. the dusty clusters are located at the periphery of dark clouds within the galaxy and appear to be partially embedded. density and pressure considerations indicate that the hii regions surrounding these clusters may be stalled, and that pre - supernova feedback has not been able to clear the clusters of their natal cocoons. these findings are in potential tension with existing models that regulate star formation with pre - supernova feedback, since pre - supernova feedback acts on short timescales, $ \ lesssim $ 4 myr, for a standard stellar initial mass function. the existence of a population of dusty star clusters with ages $ > $ 4 myr, if confirmed by future observations, paints a more complex picture for the role of stellar feedback in controlling star formation.
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arxiv:2302.11117
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optical imaging plays a critical role in advancing our understanding of three dimensional dynamics of biological systems. coherent imaging ( ci ) methods exploit spatial phase information, encoded through propagation of coherent signal light emerging from a specimen, to extract a three - dimensional representation of the object from a single high - speed measurement. until now, ci methods could not be applied to incoherent light, severely limiting their ability to image the most powerful biological probes available - fluorescent molecules - with sufficient speed and volume to observe important processes, such as neural processing in live specimens. we introduce a new imaging technique that transfers the spatial propagation phase of coherent illumination light to incoherent fluorescent light emission. the transfer of propagation phase allows ci techniques to be applied to fluorescent light imaging, and leads to large increases in imaging speed and depth of field. with this advance, biological imaging of fluorescent molecules is significantly expanded.
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arxiv:1507.06324
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following the remarkable success of diffusion models on image generation, recent works have also demonstrated their impressive ability to address a number of inverse problems in an unsupervised way, by properly constraining the sampling process based on a conditioning input. motivated by this, in this paper, we present the first approach to use diffusion models as a prior for highly accurate 3d facial brdf reconstruction from a single image. we start by leveraging a high - quality uv dataset of facial reflectance ( diffuse and specular albedo and normals ), which we render under varying illumination settings to simulate natural rgb textures and, then, train an unconditional diffusion model on concatenated pairs of rendered textures and reflectance components. at test time, we fit a 3d morphable model to the given image and unwrap the face in a partial uv texture. by sampling from the diffusion model, while retaining the observed texture part intact, the model inpaints not only the self - occluded areas but also the unknown reflectance components, in a single sequence of denoising steps. in contrast to existing methods, we directly acquire the observed texture from the input image, thus, resulting in more faithful and consistent reflectance estimation. through a series of qualitative and quantitative comparisons, we demonstrate superior performance in both texture completion as well as reflectance reconstruction tasks.
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arxiv:2305.06077
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motivated by the topologically insulating ( ti ) circuit of capacitors and inductors proposed and tested in arxiv : 1309. 0878, we present a related circuit with less elements per site. the normal mode frequency matrix of our circuit is unitarily equivalent to the hopping matrix of a quantum spin hall insulator ( qshi ) and we identify perturbations that do not backscatter the circuit ' s edge modes. the idea behind these models is generalized, providing a platform to simulate tunable and locally accessible lattices with arbitrary complex spin - dependent hopping of any range. a simulation of a non - abelian aharonov - bohm effect using such linear circuit designs is discussed.
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arxiv:1410.1243
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i use recent photometric and stellar velocity dispersion measurements of the super - star - clusters ( sscs ) ngc 1569a and ngc 1705 - 1 to determine their present - day luminosity / mass ( l _ v / m ) ratios. i then use the inferred l _ v / m ratios, together with population synthesis models of evolving star - clusters, to constrain the initial - mass - functions ( imfs ) in these objects. i find that ( l _ v / m ) _ solar = 28. 9 in 1569a, and ( l _ v / m ) _ solar = 126 in 1705 - 1. it follows that in 1569a the imf is steep with alpha ~ 2. 5 for m * * ( - alpha ) dm imfs which extend to 0. 1 m _ sun. this implies that most of the stellar mass in 1569a is contained in low - mass ( < 1 m _ sun ) stars. however, in 1705 - 1 the imf is either flat, with alpha < 2 $, or it is truncated at a lower mass - limit between 1 and 3 m _ sun. i compare the inferred imfs with the mass functions ( mfs ) of galactic globular clusters. it appears that 1569a has a sufficient reservoir of low - mass stars for it to plausibly evolve into an object similar to galactic globular clusters. however, the apparent deficiency of low - mass stars in 1705 - 1 may make it difficult for this ssc to become a globular cluster. if low - mass stars do dominate the cluster mass in 1705 - 1, the large l _ v / m ratio in this ssc may be evidence that the most massive stars have formed close to the cluster cores.
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arxiv:astro-ph/9805240
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astrophysical neutrinos are excellent probes of astroparticle physics and high - energy physics. with energies far beyond solar, supernovae, atmospheric, and accelerator neutrinos, high - energy and ultra - high - energy neutrinos probe fundamental physics from the tev scale to the eev scale and beyond. they are sensitive to physics both within and beyond the standard model through their production mechanisms and in their propagation over cosmological distances. they carry unique information about their extreme non - thermal sources by giving insight into regions that are opaque to electromagnetic radiation. this white paper describes the opportunities astrophysical neutrino observations offer for astrophysics and high - energy physics, today and in coming years.
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arxiv:2203.08096
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a phase conjugation algorithm for localizing an extended radiating electromagnetic source from boundary measurements of the electric field is presented. measurements are taken over a finite number of frequencies. the artifacts related to the finite frequency data are tackled with $ l _ 1 - $ regularization blended with the fast iterative shrinkage - thresholding algorithm with backtracking of beck & teboulle.
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arxiv:1403.5184
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we consider the orthogonal least - squares ( ols ) algorithm for the recovery of a $ m $ - dimensional $ k $ - sparse signal from a low number of noisy linear measurements. the exact recovery condition ( erc ) in bounded noisy scenario is established for ols under certain condition on nonzero elements of the signal. the new result also improves the existing guarantees for orthogonal matching pursuit ( omp ) algorithm. in addition, this framework is employed to provide probabilistic guarantees for the case that the coefficient matrix is drawn at random according to gaussian or bernoulli distribution where we exploit some concentration properties. it is shown that under certain conditions, ols recovers the true support in $ k $ iterations with high probability. this in turn demonstrates that $ { \ cal o } \ left ( k \ log m \ right ) $ measurements is sufficient for exact recovery of sparse signals via ols.
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arxiv:1608.02554
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we investigate the mass distribution of long gamma - ray burst ( grb ) host galaxies and the redshift distribution of long grbs by considering that long grbs occur in low - metallicity environments. we calculate the upper limit on the stellar mass of a galaxy which can produce long grbs by utilizing the mass - metallicity ( m - z ) relation of galaxies. after comparing with the observed grb host galaxies masses, we find that the observed grb host galaxy masses can fit the predicted masses well if grbs occur in low - metallicity $ 12 + \ log \ rm ( o / h ) _ { \ rm kk04 } < 8. 7 $. grb host galaxies have low metallicity, low mass, and high star formation rate compared with galaxies of seventh data release of the sloan digital sky survey. we also study the cumulative redshift distribution of the latest \ emph { swift } long grbs by adding dark grbs and 10 new grbs redshifts from tough survey. the observed discrepancy between the grb rate and the star formation history can be reconciled by considering that grbs tend to occur in low - metallicity galaxies with $ 12 + \ log \ rm ( o / h ) _ { \ rm kk04 } < 8. 7 $. we conclude that the metallicity cutoff that can produce long grbs is about $ 12 + \ log \ rm ( o / h ) _ { \ rm kk04 } < 8. 7 $ from the host mass distribution and redshift distribution.
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arxiv:1406.0568
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robot localization is a one of the most important problems in robotics. most of the existing approaches assume that the map of the environment is available beforehand and focus on accurate metrical localization. in this paper, we address the localization problem when the map of the environment is not present beforehand, and the robot relies on a hand - drawn map from a non - expert user. we addressed this problem by expressing the robot pose in the pixel coordinate and simultaneously estimate a local deformation of the hand - drawn map. experiments show that we are able to localize the robot in the correct room with a robustness up to 80 %
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arxiv:1504.00522
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in a recent publication we established an analogy between the free energy of a hard sphere system and the energy of an elastic network [ 1 ]. this result enables one to study the free energy landscape of hard spheres, in particular to define normal modes. in this letter we use these tools to analyze the activated transitions between meta - bassins, both in the aging regime deep in the glass phase and near the glass transition. we observe numerically that structural relaxation occurs mostly along a very small number of nearly - unstable extended modes. this number decays for denser packing and is significantly lowered as the system undergoes the glass transition. this observation supports that structural relaxation and marginal modes share common properties. in particular theoretical results [ 2, 3 ] show that these modes extend at least on some length scale $ l ^ * \ sim ( \ phi _ c - \ phi ) ^ { - 1 / 2 } $ where $ \ phi _ c $ corresponds to the maximum packing fraction, i. e. the jamming transition. this prediction is consistent with very recent numerical observations of sheared systems near the jamming threshold [ 4 ], where a similar exponent is found, and with the commonly observed growth of the rearranging regions with compression near the glass transition.
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arxiv:cond-mat/0611097
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code - switching is a prevalent linguistic phenomenon in which multilingual individuals seamlessly alternate between languages. despite its widespread use online and recent research trends in this area, research in code - switching presents unique challenges, primarily stemming from the scarcity of labelled data and available resources. in this study we investigate how pre - trained language models handle code - switched text in three dimensions : a ) the ability of plms to detect code - switched text, b ) variations in the structural information that plms utilise to capture code - switched text, and c ) the consistency of semantic information representation in code - switched text. to conduct a systematic and controlled evaluation of the language models in question, we create a novel dataset of well - formed naturalistic code - switched text along with parallel translations into the source languages. our findings reveal that pre - trained language models are effective in generalising to code - switched text, shedding light on the abilities of these models to generalise representations to cs corpora. we release all our code and data including the novel corpus at https : / / github. com / francesita / code - mixed - probes.
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arxiv:2403.04872
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by using schur transformed sequences and dyukarev - stieltjes parameters we obtain a new representation of the resolvent matrix corresponding to the truncated matricial stieltjes moment problem. explicit relations between orthogonal matrix polynomials and matrix polynomials of the second kind constructed from consecutive schur transformed sequences are obtained. additionally, a non - negative hermitian measure for which the matrix polynomials of the second kind are the orthogonal matrix polynomials is found.
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arxiv:1609.04616
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we consider primal - dual mixed finite element methods for the solution of the elliptic cauchy problem, or other related data assimilation problems. the method has a local conservation property. we derive a priori error estimates using known conditional stability estimates and determine the minimal amount of weakly consistent stabilization and tikhonov regularization that yields optimal convergence for smooth exact solutions. the effect of perturbations in data is also accounted for. a reduced version of the method, obtained by choosing a special stabilization of the dual variable, can be viewed as a variant of the least squares mixed finite element method introduced by dard \ ' e, hannukainen and hyv \ " onen in \ emph { an { $ h \ sb { \ sf { div } } $ } - based mixed quasi - reversibility method for solving elliptic { c } auchy problems }, siam j. numer. anal., 51 ( 4 ) 2013. the main difference is that our choice of regularization does not depend on auxiliary parameters, the mesh size being the only asymptotic parameter. finally, we show that the reduced method can be used for defect correction iteration to determine the solution of the full method. the theory is illustrated by some numerical examples.
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arxiv:1712.10172
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management and efficient operations in critical infrastructure such as smart grids take huge advantage of accurate power load forecasting which, due to its nonlinear nature, remains a challenging task. recently, deep learning has emerged in the machine learning field achieving impressive performance in a vast range of tasks, from image classification to machine translation. applications of deep learning models to the electric load forecasting problem are gaining interest among researchers as well as the industry, but a comprehensive and sound comparison among different architectures is not yet available in the literature. this work aims at filling the gap by reviewing and experimentally evaluating on two real - world datasets the most recent trends in electric load forecasting, by contrasting deep learning architectures on short term forecast ( one day ahead prediction ). specifically, we focus on feedforward and recurrent neural networks, sequence to sequence models and temporal convolutional neural networks along with architectural variants, which are known in the signal processing community but are novel to the load forecasting one.
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arxiv:1907.09207
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we study the convergence of entropically regularized optimal transport to optimal transport. the main result is concerned with the convergence of the associated optimizers and takes the form of a large deviations principle quantifying the local exponential convergence rate as the regularization parameter vanishes. the exact rate function is determined in a general setting and linked to the kantorovich potential of optimal transport. our arguments are based on the geometry of the optimizers and inspired by the use of $ c $ - cyclical monotonicity in classical transport theory. the results can also be phrased in terms of schr \ " odinger bridges.
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arxiv:2102.04397
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in this paper, we consider the filtering and smoothing recursions in nonparametric finite state space hidden markov models ( hmms ) when the parameters of the model are unknown and replaced by estimators. we provide an explicit and time uniform control of the filtering and smoothing errors in total variation norm as a function of the parameter estimation errors. we prove that the risk for the filtering and smoothing errors may be uniformly upper bounded by the risk of the estimators. it has been proved very recently that statistical inference for finite state space nonparametric hmms is possible. we study how the recent spectral methods developed in the parametric setting may be extended to the nonparametric framework and we give explicit upper bounds for the l2 - risk of the nonparametric spectral estimators. when the observation space is compact, this provides explicit rates for the filtering and smoothing errors in total variation norm. the performance of the spectral method is assessed with simulated data for both the estimation of the ( nonparametric ) conditional distribution of the observations and the estimation of the marginal smoothing distributions.
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arxiv:1507.06510
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in the standard model, the photon emitted in b - > s \ gamma decays is predicted to be left - handed polarized. we discuss the types of new physics which can produce a deviation from this prediction, focusing on the minimal supersymmetric standard model. a new method is proposed for testing these predictions, which makes use of angular correlations in exclusive b - > k \ pi \ pi \ gamma decays.
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arxiv:hep-ph/0207095
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in spatially non - compact minisuperpace models, spatial integrals in the hamiltonian and symplectic form must be regularised by confining them to a finite volume $ v _ o $, known as the fiducial cell. as this restriction is unnecessary in the complete theory before homogeneous reduction, the physical significance of the fiducial cell has been largely debated, especially in the context of loop quantum cosmology. understanding its role is in turn essential for assessing the minisuperspace description ' s validity and its connection to the full theory. in this work we present a systematic procedure for reduction to spatially homogeneous and isotropic minisuperspaces within the canonical framework and apply it to a massive scalar field theory and gravity. our strategy consists in implementing spatial homogeneity via second - class constraints for discrete field modes over a partitioning of the spatial slice into countably many disjoint cells. the reduced theory ' s canonical structure is then given by the corresponding dirac bracket. importantly, the latter can only be defined on a finite number of cells patched together. this identifies a finite region, the fiducial cell, whose physical size acquires then a precise meaning already at the classical level as the scale over which homogenenity is imposed. additionally, the procedure allows to track the information lost during reduction and how the error depends on $ v _ o $. we then move to the quantisation of the classically reduced theories, focusing on the relation between theories for different $ v _ o $, and study the implications for statistical moments, quantum fluctuations, and semiclassical states. in the case of a quantum scalar field, a subsector of the full quantum field theory where the results from the " first reduced, then quantised " approach can be reproduced is identified and the conditions for this to be a good approximation are also determined.
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arxiv:2211.01268
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visual place recognition is a challenging task in computer vision and a key component of camera - based localization and navigation systems. recently, convolutional neural networks ( cnns ) achieved high results and good generalization capabilities. they are usually trained using pairs or triplets of images labeled as either similar or dissimilar, in a binary fashion. in practice, the similarity between two images is not binary, but continuous. furthermore, training these cnns is computationally complex and involves costly pair and triplet mining strategies. we propose a generalized contrastive loss ( gcl ) function that relies on image similarity as a continuous measure, and use it to train a siamese cnn. furthermore, we present three techniques for automatic annotation of image pairs with labels indicating their degree of similarity, and deploy them to re - annotate the msls, tb - places, and 7scenes datasets. we demonstrate that siamese cnns trained using the gcl function and the improved annotations consistently outperform their binary counterparts. our models trained on msls outperform the state - of - the - art methods, including netvlad, netvlad - sare, ap - gem and patch - netvlad, and generalize well on the pittsburgh30k, tokyo 24 / 7, robotcar seasons v2 and extended cmu seasons datasets. furthermore, training a siamese network using the gcl function does not require complex pair mining. we release the source code at https : / / github. com / marialeyvallina / generalized _ contrastive _ loss.
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arxiv:2103.06638
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we propose a new strategy for applying large pre - trained language models to novel tasks when labeled training data is limited. rather than apply the model in a typical zero - shot or few - shot fashion, we treat the model as the basis for labeling functions in a weak supervision framework. to create a classifier, we first prompt the model to answer multiple distinct queries about an example and define how the possible responses should be mapped to votes for labels and abstentions. we then denoise these noisy label sources using the snorkel system and train an end classifier with the resulting training data. our experimental evaluation shows that prompting large language models within a weak supervision framework can provide significant gains in accuracy. on the wrench weak supervision benchmark, this approach can significantly improve over zero - shot performance, an average 19. 5 % reduction in errors. we also find that this approach produces classifiers with comparable or superior accuracy to those trained from hand - engineered rules.
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arxiv:2205.02318
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the chelyabinsk meteorite is a highly shocked, low porosity, ordinary chondrite, probably similar to s - or q - type asteroids. therefore, nanoindentation experiments on this meteorite allow us to obtain key data to understand the physical properties of near - earth asteroids. tests at different length scales provide information about the local mechanical properties of the minerals forming this meteorite : reduced young ' s modulus, hardness, elastic recovery, and fracture toughness. those tests are also useful to understand the potential to deflect threatening asteroids using a kinetic projectile. we found that the differences in mechanical properties between regions of the meteorite, which increase or reduce the efficiency of impacts, are not a result of compositional differences. a low mean particle size, attributed to repetitive shock, can increase hardness, while low porosity promotes a higher momentum multiplication. momentum multiplication is the ratio between the change in momentum of a target due to an impact, and the momentum of the projectile, and, therefore higher values imply more efficient impacts. in the chelyabinsk meteorite, the properties of the light - colored lithology materials facilitate obtaining higher momentum multiplication values, compared to the other regions described for this meteorite. also, we found a low value of fracture toughness in the shock - melt veins of chelyabinsk, which would promote the ejection of material after an impact and, therefore, increase the momentum multiplication. these results are relevant considering the growing interest in missions to test asteroid deflection, such as the recent collaboration between the european space agency and nasa, known as the asteroid impact and deflection assessment mission.
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arxiv:1612.07131
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we give a complete and explicit description of the kinematical data of higher gauge theory on principal 2 - bundles with the string 2 - group model of schommer - pries as structure 2 - group. we start with a self - contained review of the weak 2 - category bibun of lie groupoids, bibundles and bibundle morphisms. we then construct categories internal to bibun, which allow us to define principal 2 - bundles with 2 - groups internal to bibun as structure 2 - groups. using these, we lie - differentiate the 2 - group model of the string group and we obtain the well - known string lie 2 - algebra. generalizing the differentiation process, we find maurer - cartan forms leading us to higher non - abelian deligne cohomology, encoding the kinematical data of higher gauge theory together with their ( finite ) gauge symmetries. we end by discussing an example of non - abelian self - dual strings in this setting.
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arxiv:1602.03441
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the macroscopic control of ubiquitous heat flow remains poorly explored due to the lack of a fundamental theoretical method. here, by establishing temperature - dependent transformation thermotics for treating materials whose conductivity depends on temperature, we show analytical and simulation evidence for switchable thermal cloaking and a macroscopic thermal diode based on the cloaking. the latter allows heat flow in one direction but prohibits the flow in the opposite direction, which is also confirmed by our experiments. our results suggest that the temperature - dependent transformation thermotics could be a fundamental theoretical method for achieving macroscopic heat rectification, and provide guidance both for macroscopic control of heat flow and for the design of the counterparts of switchable thermal cloaks or macroscopic thermal diodes in other fields like seismology, acoustics, electromagnetics, or matter waves.
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arxiv:1505.00971
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measurements of the dc transport properties and the low - frequency conductivity noise in films of charge ordered nd _ 0. 5ca _ 0. 5mno _ 3 grown on si subtrate reveal the existence of a threshold field in the charge ordered regime beyond which strong non linear conduction sets in along with a large broad band conductivity noise. threshold - dependent conduction disappears as t - > t _ { co }, the charge ordering temperature. this observation suggests that the charge ordered state gets depinned at the onset of the non - linear conduction.
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arxiv:cond-mat/9907376
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we study movable singularities of garnier systems using the connection of the latter with schlesinger isomonodromic deformations of fuchsian systems
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arxiv:0907.1834
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the suspicion that gravity is holographic has been supported mainly by a variety of specific examples from string theory. in this paper, we propose that such a holography can actually be observed in the context of einstein ' s gravity and at least a class of generalized gravitational theories, based on a definite holographic principle where neither is the bulk space - time required to be asymptotically ads nor the boundary to be located at conformal infinity, echoing wilson ' s formulation of quantum field theory. after showing the general equilibrium thermodynamics from the corresponding holographic dictionary, in particular, we provide a rather general proof of the equality between the entropy production on the boundary and the increase of black hole entropy in the bulk, which can be regarded as strong support to this holographic principle. the entropy production in the familiar holographic superconductors / superfluids is investigated as an important example, where the role played by the holographic renormalization is explained.
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arxiv:1407.8273
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we report on robust features of the longitudinal conductivity ( $ \ sigma _ { xx } $ ) of the graphene zero - energy landau level in presence of disorder and varying magnetic fields. by mixing an anderson disorder potential with a low density of sublattice impurities, the transition from metallic to insulating states is theoretically explored as a function of landau - level splitting, using highly efficient real - space methods to compute the kubo conductivities ( both $ \ sigma _ { xx } $ and hall $ \ sigma _ { xy } $ ). as long as valley - degeneracy is maintained, the obtained critical conductivity $ \ sigma _ { xx } \ simeq 1. 4 e ^ { 2 } / h $ is robust upon disorder increase ( by almost one order of magnitude ) and magnetic fields ranging from about 2 to 200 tesla. when the sublattice symmetry is broken, $ \ sigma _ { xx } $ eventually vanishes at the dirac point owing to localization effects, whereas the critical conductivities of pseudospin - split states ( dictating the width of a $ \ sigma _ { xy } = 0 $ plateau ) change to $ \ sigma _ { xx } \ simeq e ^ { 2 } / h $, regardless of the splitting strength, superimposed disorder, or magnetic strength. these findings point towards the non dissipative nature of the quantum hall effect in disordered graphene in presence of landau level splitting.
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arxiv:1302.3483
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a fully conservative sharp - interface method is developed for multiphase flows with phase change. the coupling between two phases is implemented via introducing the interfacial fluxes, which are obtained by solving a general riemann problem with phase change. a novel four - wave model is proposed to obtain an approximate riemann solution, which simplifies the eight - dimensional roo - finding procedure in the exact solver to a sole iteration of the mass flux. unlike in the previous research, the jump conditions of all waves are imposed strictly in the present approximate riemann solver so that conservation is guaranteed. different choices of the fluid states used in the phase change model are compared, and we have shown that the adjacent states of phase interface should be used to ensure numerical consistency. to the authors ' knowledge, it has not been reported before in the open literature. with good agreements, various numerical examples are considered to validate the present method by comparing the results against the exact solutions or the previous simulations.
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arxiv:2110.07995
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the electron transport layer ( etl ) plays a fundamental role in perovskite solar cells. recently, graphene - based etls have been proved to be good candidate for scalable fabrication processes and to achieve higher carrier injection with respect to most commonly used etls. in this work we experimentally study the effects of different graphene - based etls in sensitized mapi solar cells. by means of time - integrated and picosecond time - resolved photoluminescence techniques, the carrier recombination dynamics in mapi films embedded in different etls is investigated. using graphene doped mesoporous tio2 ( g + mtio2 ) with the addition of a lithium - neutralized graphene oxide ( go - li ) interlayer as etl, we find that the carrier collection efficiency is increased by about a factor two with respect to standard mtio2. taking advantage of the absorption coefficient dispersion, we probe the mapi layer morphology, along the thickness, finding that the mapi embedded in the etl composed by g + mtio2 plus go - li brings to a very good crystalline quality of the mapi layer with a trap density about one order of magnitude lower than that found with the other etls. in addition, this etl freezes mapi at the tetragonal phase, regardless of the temperature. graphene - based etls can open the way to significant improvement of perovskite solar cells.
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arxiv:1702.04159
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the electronic and structural properties of zigzag and armchair single - wall carbon nanotubes ( swcnt ) with a single vacancy or two vacancies located at various distances have been obtained within the frame of the density function theory ( dft ) and a molecular dynamics method. it is found that the vacancy defects interact at long ranges in armchair swcnts unlike the short - range interaction in zigzag swcnts. the density of states for different vacancy densities shows that the local energy gap shrinks with the vacancy density increase. this and other results of the investigation provide insight into understanding the relation between the local deformation of a defective nanotube and its measurable electronic properties.
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arxiv:0807.1999
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in this article we define a natural tropicalization procedure for closed subsets of log - regular varieties in the case of constant coefficients and study its basic properties. this framework allows us to generalize some of tevelev ' s results on tropical compactification as well as hacking ' s result on the cohomology of the link of a tropical variety to log - regular varieties.
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arxiv:1309.4011
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version identification ( vi ) systems now offer accurate and scalable solutions for detecting different renditions of a musical composition, allowing the use of these systems in industrial applications and throughout the wider music ecosystem. such use can have an important impact on various stakeholders regarding recognition and financial benefits, including how royalties are circulated for digital rights management. in this work, we take a step toward acknowledging this impact and consider vi systems as socio - technical systems rather than isolated technologies. we propose a framework for quantifying performance disparities across 5 systems and 6 relevant side attributes : gender, popularity, country, language, year, and prevalence. we also consider 3 main stakeholders for this particular information retrieval use case : the performing artists of query tracks, those of reference ( original ) tracks, and the composers. by categorizing the recordings in our dataset using such attributes and stakeholders, we analyze whether the considered vi systems show any implicit biases. we find signs of disparities in identification performance for most of the groups we include in our analyses. moreover, we also find that learning - and rule - based systems behave differently for some attributes, which suggests an additional dimension to consider along with accuracy and scalability when evaluating vi systems. lastly, we share our dataset with attribute annotations to encourage vi researchers to take these aspects into account while building new systems.
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arxiv:2109.15188
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in recent years, supervised learning with convolutional networks ( cnns ) has seen huge adoption in computer vision applications. comparatively, unsupervised learning with cnns has received less attention. in this work we hope to help bridge the gap between the success of cnns for supervised learning and unsupervised learning. we introduce a class of cnns called deep convolutional generative adversarial networks ( dcgans ), that have certain architectural constraints, and demonstrate that they are a strong candidate for unsupervised learning. training on various image datasets, we show convincing evidence that our deep convolutional adversarial pair learns a hierarchy of representations from object parts to scenes in both the generator and discriminator. additionally, we use the learned features for novel tasks - demonstrating their applicability as general image representations.
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arxiv:1511.06434
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we investigate the cosmological perturbations in f ( t ) gravity. examining the pure gravitational perturbations in the scalar sector using a diagonal vierbien, we extract the corresponding dispersion relation, which provides a constraint on the f ( t ) ansatzes that lead to a theory free of instabilities. additionally, upon inclusion of the matter perturbations, we derive the fully perturbed equations of motion, and we study the growth of matter overdensities. we show that f ( t ) gravity with f ( t ) constant coincides with general relativity, both at the background as well as at the first - order perturbation level. applying our formalism to the power - law model we find that on large subhorizon scales ( o ( 100 mpc ) or larger ), the evolution of matter overdensity will differ from lcdm cosmology. finally, examining the linear perturbations of the vector and tensor sectors, we find that ( for the standard choice of vierbein ) f ( t ) gravity is free of massive gravitons.
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arxiv:1008.1250
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we use the solution of the dirac equation for quarkonium atom in the 4d anti de sitter ( ads $ _ { 4 } $ ) space to investigate the effect of the large negative cosmological constant on the phenomenon of quark confinement. we do the required calculations in the ads $ _ { 4 } $ space to indicate that large cosmological constant can describe the quark confinement. in fact using the coulomb potential in dirac equation while we employ the ads metric will additionally lead us to a linear potential in the quark - antiquark interaction which can be considered to explain the quark confinement. this confining term is arising essentially from the geometrical features of the space. on the other hand the origin of the large cosmological constant can be justified by assuming the appearance of micro black holes in the recent hadronic collision process which is now current, for instance, at the lhc project.
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arxiv:1611.05316
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the aim of this paper was the detection of pathologies through respiratory sounds. the icbhi ( international conference on biomedical and health informatics ) benchmark was used. this dataset is composed of 920 sounds of which 810 are of chronic diseases, 75 of non - chronic diseases and only 35 of healthy individuals. as more than 88 % of the samples of the dataset are from the same class ( chronic ), the use of a variational convolutional autoencoder was proposed to generate new labeled data and other well known oversampling techniques after determining that the dataset classes are unbalanced. once the preprocessing step was carried out, a convolutional neural network ( cnn ) was used to classify the respiratory sounds into healthy, chronic, and non - chronic disease. in addition, we carried out a more challenging classification trying to distinguish between the different types of pathologies or healthy : urti, copd, bronchiectasis, pneumonia, and bronchiolitis. we achieved results up to 0. 993 f - score in the three - label classification and 0. 990 f - score in the more challenging six - class classification.
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arxiv:2402.02183
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for the past decade observations of the alignement of pne symmetries with respect to the galactic disk have led to conflicting results. recently observational evidence for alignment between pne and local interstellar magnetic fields in the central part of the galaxy ( $ b < 5 ^ \ circ $ ) has been found. we studied the role of the interstellar magnetic field on the dynamical evolution of a pn by means of an analytical model and from 3d mhd numerical simulations. we test under what conditions typical ejecta would have their dynamics severely modified by an interstellar magnetic field. we found that uniform fields of $ > 100 \ mu $ g are required in order to be dynamically dominant. this is found to occur only at later evolutionary stages, therefore being unable to change the general morphology of the nebula. however, the symmetry axis of bipolar and elliptical nebulae end up aligned to the external field. this result can explain why different samples of pne result in different conclusions regarding the alignment of pne. objects located at high galactic latitudes, or at large radii, should present no preferential alignment with respect to the galactic plane. pne located at the galactic centre and low latitudes would, on the other hand, be preferentiably aligned to the disk. finally, we present synthetic polarization maps of the nebulae to show that the polarization vectors, as well as the field lines at the expanding shell, are not uniform even in the strongly magnetized case, indicating that polarization maps of nebulae are not adequate in probing the orientation, or intensity, of the dominant external field.
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arxiv:1312.2910
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we present high - precision measurements of the nusselt number n as a function of the rayleigh number r for cylindrical samples of water ( prandtl number sigma = 4. 4 ) with a diameter d of 49. 7 cm and heights l = 116. 3, 74. 6, and 50. 6 cm, as well as for d = 24. 8 cm and l = 90. 2 cm. for each aspect ratio gamma = d / l = 0. 28, 0. 43, 0. 67, and 0. 98 the data cover a range of a little over a decade of r. the maximum r ~ = 10 ^ 12 and nusselt number n ~ = 600 were reached for gamma = 0. 43 and d = 49. 7. the data were corrected for the influence of the finite conductivity of the top and bottom plates on the heat transport in the fluid to obtain estimates of n _ infty for plates with infinite conductivity. the results for n _ infty and gamma > = 0. 43 are nearly independent of gamma. for gamma = 0. 275 n _ infty falls about 2. 5 % below the other data. for r ~ < = 10 ^ 11, the effective exponent gamma _ eff of n _ infty = n _ 0 r ^ gamma _ eff is about 0. 321, larger than those of the grossmann - lohse model with its current parameters by about 0. 01. for the largest rayleigh numbers covered for gamma = 0. 98, 0. 67, and 0. 43, gamma _ eff saturates at the asymptotic value gamma = 1 / 3 of the grossmann - lohse model. the data do not reveal any crossover to a kraichnan regime with gamma _ eff > 1 / 3.
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arxiv:physics/0409052
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we prove that the arithmetic fundamental group of x admits no section over the absolute galois group of q when x is the schinzel curve, thereby confirming in this example the prediction given by grothendieck ' s section conjecture. - - - - - nous d \ ' emontrons que le groupe fondamental arithm \ ' etique de x n ' admet pas de section au - dessus du groupe de galois absolu de q lorsque x est la courbe de schinzel, confirmant ainsi sur cet exemple la pr \ ' ediction donn \ ' ee par la conjecture des sections de grothendieck.
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arxiv:1005.1984
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we revisit the leading irrelevant deformation of $ \ mathcal { n } = 4 $ super yang - mills theory that preserves sixteen supercharges. we consider the deformed theory on $ s ^ 3 \ times \ mathbb { r } $. we are able to write a closed form expression of the classical action thanks to a formalism that realizes eight supercharges off shell. we then investigate integrability of the spectral problem, by studying the spin - chain hamiltonian in planar perturbation theory. while there are some structural indications that a suitably defined deformation might preserve integrability, we are unable to settle this question by our two - loop calculation ; indeed up to this order we recover the integrable hamiltonian of undeformed $ \ mathcal { n } = 4 $ sym due to accidental symmetry enhancement. we also comment on the holographic interpretation of the theory.
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arxiv:2006.04792
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we study experimentally a coiling instability of cylindrical multilamellar stacks of phospholipid membranes, induced by polymers with hydrophobic anchors grafted along their hydrophilic backbone. our system is unique in that coils form in the absence of both twist and adhesion. we interpret our experimental results in terms of a model in which local membrane curvature and polymer concentration are coupled. the model predicts the occurrence of maximally tight coils above a threshold polymer occupancy. a proper comparison between the model and experiment involved imaging of projections from simulated coiled tubes with maximal curvature and complicated torsions.
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arxiv:cond-mat/0008435
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we report experimental results on the dynamics of heavy particles of the size of the kolmogorov - scale in a fully developed turbulent flow. the mixed eulerian structure function of two - particle velocity and acceleration difference vectors < \ delta v \ cdot \ delta a _ p > was observed to increase significantly with particle inertia for identical flow conditions. we show that this increase is related to a preferential alignment between these dynamical quantities. with increasing particle density the probability for those two vectors to be collinear was observed to grow. we show that these results are consistent with the preferential sampling of strain - dominated regions by inertial particles.
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arxiv:1002.3755
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the phenomena of strong running coupling and hadron mass generating have been studied in the framework of a qcd - inspired relativistic model of quark - gluon interaction with infrared confined propagators. we derived a meson mass equation and revealed a specific new behaviour of the mass - dependent strong coupling $ \ hat \ alpha _ s ( m ) $ defined in the time - like region. a new infrared freezing point $ \ hat \ alpha _ s ( 0 ) = 1. 03198 $ at origin has been found and it did not depend on the confinement scale $ \ lambda > 0 $. independent and new estimates on the scalar glueball mass, ' radius ' and gluon condensate value have been performed. the spectrum of conventional mesons have been calculated by introducing a minimal set of parameters : the masses of constituent quarks and $ \ lambda $. the obtained values are in good agreement with the latest experimental data with relative errors less than 1. 8 percent. accurate estimates of the leptonic decay constants of pseudoscalar and vector mesons have been performed.
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arxiv:1712.05531
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we consider bosonic atoms with a repulsive contact interaction in a trap potential for a bose - einstein condensation and additionally include a random potential. the ensemble averages for two models of static and dynamic disorder are performed and investigated in parallel. the bosonic many body systems of the two disorder models are represented by coherent state path integrals on the keldysh time contour which allow exact ensemble averages for zero and finite temperatures. these ensemble averages of coherent state path integrals therefore present alternatives to replica field theories or supersymmetric averaging techniques.
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arxiv:cond-mat/0611416
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is the first deliverable that conditions the following design and manufacturing steps. the risk management stage shall drive the product so that product risks are reduced at an acceptable level with respect to the benefits expected for the patients for the use of the device. the technical file contains all the documentation data and records supporting medical device certification. fda technical file has similar content although organized in a different structure. the quality system deliverables usually include procedures that ensure quality throughout all product life cycles. the same standard ( iso en 13485 ) is usually applied for quality management systems in the us and worldwide. in the european union, there are certifying entities named " notified bodies ", accredited by the european member states. the notified bodies must ensure the effectiveness of the certification process for all medical devices apart from the class i devices where a declaration of conformity produced by the manufacturer is sufficient for marketing. once a product has passed all the steps required by the medical device directive, the device is entitled to bear a ce marking, indicating that the device is believed to be safe and effective when used as intended, and, therefore, it can be marketed within the european union area. the different regulatory arrangements sometimes result in particular technologies being developed first for either the u. s. or in europe depending on the more favorable form of regulation. while nations often strive for substantive harmony to facilitate cross - national distribution, philosophical differences about the optimal extent of regulation can be a hindrance ; more restrictive regulations seem appealing on an intuitive level, but critics decry the tradeoff cost in terms of slowing access to life - saving developments. = = = rohs ii = = = directive 2011 / 65 / eu, better known as rohs 2 is a recast of legislation originally introduced in 2002. the original eu legislation " restrictions of certain hazardous substances in electrical and electronics devices " ( rohs directive 2002 / 95 / ec ) was replaced and superseded by 2011 / 65 / eu published in july 2011 and commonly known as rohs 2. rohs seeks to limit the dangerous substances in circulation in electronics products, in particular toxins and heavy metals, which are subsequently released into the environment when such devices are recycled. the scope of rohs 2 is widened to include products previously excluded, such as medical devices and industrial equipment. in addition, manufacturers are now obliged to provide conformity risk assessments and test reports – or explain why they are lacking. for the first time, not only manufacturers but also importers and distributors share a responsibility to ensure electrical and electronic equipment within the scope of rohs compl
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https://en.wikipedia.org/wiki/Biomedical_engineering
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an alternative approach to introducing gravitational dynamics on a brane embedded in a higher dimensional spacetime is presented. the brane is treated as a boundary of a higher dimensional manifold in which the bulk action is described by a metric independent topological quantum field theory. the example of a five dimensional non - abelian bf theory with a boundary brane is considered. a natural boundary condition is adopted chosen for consistency of the topological action despite the presence of a boundary. the resulting effective action on the brane is the action of general relativity in first order form plus terms involving the extrinsic curvature of the brane.
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arxiv:hep-th/0108066
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the paper presents a joint beamforming algorithm using statistical channel state information ( s - csi ) for reconfigurable intelligent surfaces ( ris ) for multiuser miso wireless communications. we used s - csi, which is a long - term average of the cascaded channel as opposed to instantaneous csi utilized in most existing works. through this method, the overhead of channel estimation is dramatically reduced. we propose a proximal policy optimization ( ppo ) algorithm which is a well - known actor - critic based reinforcement learning ( rl ) algorithm to solve the optimization problem. to test the efficacy of this algorithm, simulation results are presented along with evaluations of key system parameters, including the rician factor and ris location, on the achievable sum rate of the users.
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arxiv:2209.09856
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we propose an extension of the cable equation by introducing a caputo time fractional derivative. the fundamental solutions of the most common boundary problems are derived analitically via laplace transform, and result be written in terms of known special functions. this generalization could be useful to describe anomalous diffusion phenomena with leakage as signal conduction in spiny dendrites. the presented solutions are computed in matlab and plotted.
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arxiv:1702.05339
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in this paper, we address the problem of designing stochastic model predictive control ( mpc ) schemes for linear systems affected by unbounded disturbances. the contribution of the paper is twofold. first, motivated by the difficulty of guaranteeing recursive feasibility in this framework, due to the nonzero probability of violating chance - constraints in the case of unbounded noise, we introduce the novel definition of measured - state conditioned recursive feasibility in expectation. second, we construct a stochastic mpc scheme, based on the introduction of ellipsoidal probabilistic reachable sets, which implements a closed - loop initialization strategy, i. e., the current measured - state is employed for initializing the optimization problem. this new scheme is proven to satisfy the novel definition of recursive feasibility, and its superiority with respect to open - loop initialization schemes, arising from the fact that one never neglects the information brought by the current measurement, is shown through numerical examples.
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arxiv:2406.13522
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we theoretically study the topological properties of the tight - binding model on the breathing kagome lattice with antisymmetric spin - orbit coupling ( soc ) between nearest neighbors. we show that the system hosts nontrivial topological phases even without second - nearest - neighbor hopping, and that the weakly dispersing band of the kagome lattice can become topological. the main results are presented in the form of phase diagrams, where the $ \ mathbb { z } _ 2 $ topological index is shown as a function of soc ( intrinsically allowed and rashba ) and lattice trimerization. in addition, exact diagonalization is compared with effective low - energy theories around the high - symmetry points. we find that the weakly dispersing band has a very robust topological property associated with it. moreover, the rashba soc can produce a topological phase rather than hinder it, in contrast to the honeycomb lattice. finally, we consider the case of a fully spin polarized ( ferromagnetic ) system, breaking time - reversal symmetry. we find a phase diagram that includes systems with finite chern numbers. in this case too, the weakly dispersing band is topologically robust to trimerization.
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arxiv:1811.08182
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pseudothermal light by scattering laser light from rotating groundglass has been extensively employed to study optical coherence in both classical and quantum optics ever since its invention in 1960s. in this paper, we will show that by replacing the invariant intensity laser light in pseudothermal light source with intensity modulated laser light, superbunching pseudothermal light can be obtained. two - photon interference in feynman ' s path integral theory is employed to interpret the phenomenon. two - photon superbunching is experimentally observed by employing common instruments in optical laboratory. the proposed superbunching pseudothermal light is helpful to understand the physics of two - photon bunching and superbunching, and the difference between classical and quantum interpretations of the second - and higher - order interference of light.
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arxiv:1809.00181
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the results of a world - wide coordinated observational campaign on the broad - lined type ic sn 2003jd are presented. in total, 74 photometric data points and 26 spectra were collected using 11 different telescopes. sn 2003jd is one of the most luminous sn ic ever observed. a comparison with other type ic supernovae ( sne ic ) confirms that sn 2003jd represents an intermediate case between broad - line events ( 2002ap, 2006aj ), and highly energetic sne ( 1997ef, 1998bw, 2003dh, 2003lw ), with an ejected mass of m _ { ej } = 3. 0 + / - 1 mo and a kinetic energy of e _ { k } ( tot ) = 7 _ { - 2 } ^ { + 3 } 10 ^ { 51 } erg. sn 2003jd is similar to sn 1998bw in terms of overall luminosity, but it is closer to sne 2006aj and 2002ap in terms of light - curve shape and spectral evolution. the comparison with other sne ic, suggests that the v - band light curves of sne ic can be partially homogenized by introducing a time stretch factor. finally, due to the similarity of sn 2003jd to the sn 2006aj / xrf 060218 event, we discuss the possible connection of sn 2003jd with a grb.
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arxiv:0710.5173
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cross - camera image data association is essential for many multi - camera computer vision tasks, such as multi - camera pedestrian detection, multi - camera multi - target tracking, 3d pose estimation, etc. this association task is typically stated as a bipartite graph matching problem and often solved by applying minimum - cost flow techniques, which may be computationally inefficient with large data. furthermore, cameras are usually treated by pairs, obtaining local solutions, rather than finding a global solution at once. other key issue is that of the affinity measurement : the widespread usage of non - learnable pre - defined distances, such as the euclidean and cosine ones. this paper proposes an efficient approach for cross - cameras data - association focused on a global solution, instead of processing cameras by pairs. to avoid the usage of fixed distances, we leverage the connectivity of graph neural networks, previously unused in this scope, using a message passing network to jointly learn features and similarity. we validate the proposal for pedestrian multi - view association, showing results over the epfl multi - camera pedestrian dataset. our approach considerably outperforms the literature data association techniques, without requiring to be trained in the same scenario in which it is tested. our code is available at \ url { http : / / www - vpu. eps. uam. es / publications / gnn _ cca }.
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arxiv:2201.06311
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kagome vanadates { \ it a } v $ _ 3 $ sb $ _ 5 $ display unusual low - temperature electronic properties including charge density waves ( cdw ), whose microscopic origin remains unsettled. recently, cdw order has been discovered in a new material scv $ _ 6 $ sn $ _ 6 $, providing an opportunity to explore whether the onset of cdw leads to unusual electronic properties. here, we study this question using angle - resolved photoemission spectroscopy ( arpes ) and scanning tunneling microscopy ( stm ). the arpes measurements show minimal changes to the electronic structure after the onset of cdw. however, stm quasiparticle interference ( qpi ) measurements show strong dispersing features related to the cdw ordering vectors. a plausible explanation is the presence of a strong momentum - dependent scattering potential peaked at the cdw wavevector, associated with the existence of competing cdw instabilities. our stm results further indicate that the bands most affected by the cdw are near vhs, analogous to the case of { \ it a } v $ _ 3 $ sb $ _ 5 $ despite very different cdw wavevectors.
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arxiv:2406.11212
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a class of strange star is analyzed in the present article in hydrostatic equilibrium whose state is defined by a cfl phase equation of state. we compare our result with those obtained from mit bag equation of state for strange quark matter which are regarded as free particles. we note that if we consider quarks to form cooper pair and their description is made by cfl equation of state, the maximum mass of strange star assumes value as high as 3. 61 $ m _ { \ odot } $ which is well above the value 2. 03 $ m _ { \ odot } $ obtained by considering mit bag equation of state for massless free quarks. both the maximum masses are determined by solving tov equation for different values of strange quark mass $ m _ s $. thus inclusion of possibility of quark pair formation in the theory permits us to accommodate a wider class of compact objects like 4u 1820 - 30, psr j1614 - 2230, psr j0030 + 0451, psr j1903 + 0327, psr j0740 + 6620, psr j0952 - 0607 and mass of the companion star in gw170817 and gw190814 events in our model. the consideration of such high value of mass is hardly obtainable theoretically from normal strange star models in general relativity even with fast rotation effect. the object psr j0952 - 0607 is found to be the fastest and heaviest pulsar in the disk of milky way galaxy having mass 2. 59 $ m _ { \ odot } $ may be predicted in our model as observational evidence supports the existence of strange quark matter in its composition.
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arxiv:2304.01629
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fractional kinetic equations are investigated in order to describe the various phenomena governed by anomalous reaction in dynamical systems with chaotic motion. many authors have provided solutions for various families of fractional kinetic equations involving special functions. here, in this paper, we aim at presenting solutions of certain general families of fractional kinetic equations associated with the generalized modified $ k $ - bessel function of the first kind. it is also pointed out that the main results presented here are general enough to be able to be specialized to yield many known and ( presumably ) new solutions for fractional kinetic equations.
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arxiv:1612.03267
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we present the first - principle derivation of a weak - strong duality between the fishnet theory in four dimensions and a discretized string - like model living in five dimensions. at strong coupling, the dual description becomes classical and we demonstrate explicitly the classical integrability of the model. we test our results by reproducing the strong coupling limit of the $ 4 $ - point correlator computed before non - perturbatively from the conformal partial wave expansion. due to the extreme simplicity of our model, it could provide an ideal playground for holography with no super - symmetry. furthermore, since the fishnet model and $ { \ cal n } = 4 $ sym theory are continuously linked our consideration could shed light on the derivation of ads / cft for the latter.
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arxiv:1903.10508
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in the application of semiconductor detectors, the charge - sensitive amplifier is widely used in front - end electronics. the output signal is shaped by a typical exponential decay. depending on the feedback network, this type of front - end electronics suffers from the ballistic deficit problem, or an increased rate of pulse pile - ups. moreover, spectroscopy applications require a correction of the pulse - height, while a shortened pulse - width is desirable for high - throughput applications. for both objectives, digital deconvolution of the exponential decay is convenient. with a general method and the signals of our custom charge - sensitive amplifier for cadmium zinc telluride detectors, we show how the transfer function of an amplifier is adapted to an infinite impulse response ( iir ) filter. this paper investigates different design methods for an iir filter in the discrete - time domain and verifies the obtained filter coefficients with respect to the equivalent continuous - time frequency response. finally, the exponential decay is shaped to a step - like output signal that is exploited by a forward - looking pulse processing.
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arxiv:1604.08750
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we report neutron inelastic scattering experiments on single crystal pbmg $ _ { 1 / 3 } $ nb $ _ { 2 / 3 } $ o $ _ { 3 } $ doped with 32 \ % pbtio $ _ { 3 } $, a relaxor ferroelectric that lies close to the morphotropic phase boundary. when cooled under an electric field $ \ mathbf { e } \ parallel $ [ 001 ] into tetragonal and monoclinic phases, the scattering cross section from transverse acoustic ( ta ) phonons polarized parallel to $ \ mathbf { e } $ weakens and shifts to higher energy relative to that under zero - field - cooled conditions. likewise, the scattering cross section from transverse optic ( to ) phonons polarized parallel to $ \ mathbf { e } $ weakens for energy transfers $ 4 \ leq \ hbar \ omega \ leq 9 $ mev. however, ta and to phonons polarized perpendicular to $ \ mathbf { e } $ show no change. this anisotropic field response is similar to that of the diffuse scattering cross section, which, as previously reported, is suppressed when polarized parallel to $ \ mathbf { e } $, but not when polarized perpendicular to $ \ mathbf { e } $. our findings suggest that the lattice dynamics and dynamic short - range polar correlations that give rise to the diffuse scattering are coupled.
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arxiv:1509.07085
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the babar and belle collaborations have recently found evidence for mixing within the d meson system. we present some of the mixing search techniques used by babar and their status as of the beginning of the summer 2007. these have culminated in a measurement in the k decay final state of the d that is inconsistent with the no - mixing hypothesis with a significance of 3. 9 standard deviations.
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arxiv:0710.1211
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acoustics - based techniques are investigated to focus and bunch nanoparticle beams. this allows to overcome the prominent problem of the longitudinal and transverse mismatch of particle stream and x - ray beam in single - particle / single molecule imaging at x - ray free - electron lasers ( xfel ). it will also enable synchronised injection of particle streams at khz repetition rates. transverse focusing concentrates the particle flux to the ( sub ) micrometer x - ray focus. in the longitudinal direction, focused acoustic waves can be used to bunch the particle to the same repetition rate as the x - ray pulses. the acoustic manipulation is based on simple mechanical recoil effects and could be advantageous over light - pressure - based methods, which rely on absorption. the acoustic equipment is easy to implement and can be conveniently inserted into current xfel endstations. with the proposed method, data collection times could be reduced by a factor of $ 10 ^ 4 $. this work does not just provide an efficient method for acoustic manipulation of streams of arbitrary gas phase particles, but also opens up wide avenues for acoustics - based particle optics.
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arxiv:1803.07472
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in complex environments with large discrete action spaces, effective decision - making is critical in reinforcement learning ( rl ). despite the widespread use of value - based rl approaches like q - learning, they come with a computational burden, necessitating the maximization of a value function over all actions in each iteration. this burden becomes particularly challenging when addressing large - scale problems and using deep neural networks as function approximators. in this paper, we present stochastic value - based rl approaches which, in each iteration, as opposed to optimizing over the entire set of $ n $ actions, only consider a variable stochastic set of a sublinear number of actions, possibly as small as $ \ mathcal { o } ( \ log ( n ) ) $. the presented stochastic value - based rl methods include, among others, stochastic q - learning, stochdqn, and stochddqn, all of which integrate this stochastic approach for both value - function updates and action selection. the theoretical convergence of stochastic q - learning is established, while an analysis of stochastic maximization is provided. moreover, through empirical validation, we illustrate that the various proposed approaches outperform the baseline methods across diverse environments, including different control problems, achieving near - optimal average returns in significantly reduced time.
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arxiv:2405.10310
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we study a complex ginzburg - landau ( gl ) type model related to fluid instabilities in the boundary of magnetized toroidal plasmas ( called edge - localized modes ) with a prescribed shear flow on the neumann boundary condition. we obtain the following universal results for the model in a one - dimensional interval. first, if the shear is weak, there is a unique linearly stable steady - state perturbed from the nonzero constant steady - state corresponding to the zero shear case. second, if the shear is strong, there is no plausible steady - state except the trivial zero solution in the interval. with the help of these results and the existence of global attractors, we can dramatically reduce the number of cases for the long - time behavior of a solution in the model.
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arxiv:1706.08036
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in mathematics and other fields, a lemma ( pl. : lemmas or lemmata ) is a generally minor, proven proposition which is used to prove a larger statement. for that reason, it is also known as a " helping theorem " or an " auxiliary theorem ". in many cases, a lemma derives its importance from the theorem it aims to prove ; however, a lemma can also turn out to be more important than originally thought. = = etymology = = from the ancient greek λημμα, ( perfect passive ειλημμαι ) something received or taken. thus something taken for granted in an argument. = = comparison with theorem = = there is no formal distinction between a lemma and a theorem, only one of intention ( see theorem terminology ). however, a lemma can be considered a minor result whose sole purpose is to help prove a more substantial theorem – a step in the direction of proof. = = well - known lemmas = = some powerful results in mathematics are known as lemmas, first named for their originally minor purpose. these include, among others : while these results originally seemed too simple or too technical to warrant independent interest, they have eventually turned out to be central to the theories in which they occur. = = see also = = = = notes = = = = references = = = = external links = = doron zeilberger, opinion 82 : a good lemma is worth a thousand theorems this article incorporates material from lemma on planetmath, which is licensed under the creative commons attribution / share - alike license.
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https://en.wikipedia.org/wiki/Lemma_(mathematics)
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ultra low radiation dose in x - ray computed tomography ( ct ) is an important clinical objective in order to minimize the risk of carcinogenesis. compressed sensing ( cs ) enables significant reductions in radiation dose to be achieved by producing diagnostic images from a limited number of ct projections. however, the excessive computation time that conventional cs - based ct reconstruction typically requires has limited clinical implementation. in this paper, we first demonstrate that a thorough analysis of ct reconstruction through a maximum a posteriori objective function results in a weighted compressive sensing problem. this analysis enables us to formulate a low dose fan beam and helical cone beam ct reconstruction. subsequently, we provide an efficient solution to the formulated cs problem based on a fast composite splitting algorithm - latent expected maximization ( fcsa - lem ) algorithm. in the proposed method we use pseudo polar fourier transform as the measurement matrix in order to decrease the computational complexity ; and rebinning of the projections to parallel rays in order to extend its application to fan beam and helical cone beam scans. the weight involved in the proposed weighted cs model, denoted by error adaptation weight ( eaw ), is calculated based on the statistical characteristics of ct reconstruction and is a function of poisson measurement noise and rebinning interpolation error. simulation results show that low computational complexity of the proposed method made the fast recovery of the ct images possible and using eaw reduces the reconstruction error by one order of magnitude. recovery of a high quality 512 $ \ times $ 512 image was achieved in less than 20 sec on a desktop computer without numerical optimizations.
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arxiv:1402.1801
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modeling quasar spectra is a fundamental task in astrophysics as quasars are the tell - tale sign of cosmic evolution. we introduce a novel unsupervised learning algorithm, quasar factor analysis ( qfa ), for recovering the intrinsic quasar continua from noisy quasar spectra. qfa assumes that the ly $ \ alpha $ forest can be approximated as a gaussian process, and the continuum can be well described as a latent factor model. we show that qfa can learn, through unsupervised learning and directly from the quasar spectra, the quasar continua and ly $ \ alpha $ forest simultaneously. compared to previous methods, qfa achieves state - of - the - art performance for quasar continuum prediction robustly but without the need for predefined training continua. in addition, the generative and probabilistic nature of qfa paves the way to understanding the evolution of black holes as well as performing out - of - distribution detection and other bayesian downstream inferences.
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arxiv:2207.02788
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the semileptonic $ d _ { l4 } $ decay including $ d \ to k \ pi l \ nu $ and $ d \ to \ pi \ pi l \ nu $ have been extensively studied. in these references, the form factors and differential decay rate are explicitly stated. however, we would like to stress that in these papers the final state interactions are often overlooked, i. e. rescattering effect of the pseudoscalars produced by $ d _ { l4 } $ decay may be very important, at least on the side of phase of form factors due to watson ' s theorem. in this short paper, we will display this rescattering effect in the framework of heavy hadron chiral perturbation theory, it thus must be a very useful and indispensable supplement of the previous papers on $ d _ { l4 } $ study.
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arxiv:1102.5426
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a suitable state representation is a fundamental part of the learning process in reinforcement learning. in various tasks, the state can either be described by natural language or be natural language itself. this survey outlines the strategies used in the literature to build natural language state representations. we appeal for more linguistically interpretable and grounded representations, careful justification of design decisions and evaluation of the effectiveness of different approaches.
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arxiv:2007.09774
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in recent years, journalists and other researchers have used web archives as an important resource for their study of disinformation. this paper provides several examples of this use and also brings together some of the work that the old dominion university web science and digital libraries ( ws - dl ) research group has done in this area. we will show how web archives have been used to investigate changes to webpages, study archived social media including deleted content, and study known disinformation that has been archived.
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arxiv:2306.10004
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we have studied the coherent excitation of a strongly coupled qd / photonic crystal cavity system. time - resolved reflectivity measurements show the vacuum rabi oscillation of the dot in the cavity. next, we considered the resonant driving of a cavity - detuned dot, which efficiently populates the cavity mode. this cavity - controlled read - out channel allows high - resolution single quantum dot spectroscopy. autocorrelation measurements on the cavity mode show antibunching and suggest the use of the resonantly driven qd / cavity system as an on - demand source of single photons with potentially near - unity indistinguishability.
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arxiv:0902.2428
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