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hidden symmetries, described by higher order in momenta integrals of motion that generate nonlinear algebras, are explored at the level of classical and quantum mechanics in a variety of physical systems related to conformal and superconformal invariance.
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arxiv:2012.08963
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these notes introduce the fundamentals of black hole geometry, the thermality of the vacuum, and the hawking effect, in spacetime and its analogues. stimulated emission of hawking radiation, the trans - planckian question, short wavelength dispersion, and white hole radiation in the setting of analogue models are also discussed. no prior knowledge of differential geometry, general relativity, or quantum field theory in curved spacetime is assumed.
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arxiv:1212.6821
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we present synthesis models of the x - ray background where the available x - ray observational constraints are used to derive information on the agn population properties. we show the need for luminous x - ray absorbed agns, the qso2s, in reproducing the 2 - 10 kev source counts at relatively bright fluxes. we compare a model where the evolution of absorbed agns is faster than that of unabsorbed ones, with a standard model where absorbed and unabsorbed agns evolve at the same rate. it is found that an increase by a factor of ~ 2 from z = 0 to z ~ 1. 3 in the ratio between absorbed and unabsorbed agns would provide a significant improvement in the data description. finally, we make predictions on the agns to be observed in deep x - ray surveys which contain information on the agn space density at high redshift.
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arxiv:astro-ph/0011341
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spin foam models for quantum gravity are derived from lattice path integrals. the setting involves variables from both lattice bf theory and regge calculus. the action consists in a regge action, which depends on areas, dihedral angles and includes the immirzi parameter. in addition, a measure is inserted to ensure a consistent gluing of simplices, so that the amplitude is dominated by configurations which satisfy the parallel transport relations. we explicitly compute the path integral as a sum over spin foams for a generic measure. the freidel - krasnov and engle - pereira - rovelli models correspond to a special choice of gluing. in this case, the equations of motion describe genuine geometries, where the constraints of area - angle regge calculus are satisfied. furthermore, the immirzi parameter drops out of the on - shell action, and stationarity with respect to area variations requires spacetime geometry to be flat.
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arxiv:0905.1501
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in this short note we use the umbral formalism to derive the ramanujan master theorem and discuss its extension to more general cases.
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arxiv:1103.3947
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we show that the rate of pollution of white dwarfs by asteroidal material implies a concomitant rate of material ejection that can contribute significantly to the population of interstellar minor bodies. we note also that the irradiation during post main sequence evolution implies that much of this ejected material may lose volatiles, providing a rationale for the curious properties of the recently discovered interstellar object oumuamua.
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arxiv:1712.07247
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deformation quantization of bosonic strings is considered. we show that the light - cone gauge is the most convenient classical description to perform the quantization of bosonic strings in the deformation quantization formalism. similar to the field theory case, the oscillator variables greatly facilitates the analysis. the mass spectrum, propagators and the virasoro algebra are finally described within this deformation quantization scheme.
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arxiv:hep-th/0002212
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we integrate numerically the kardar - parisi - zhang ( kpz ) equation in 1 + 1 and 2 + 1 dimensions using an euler discretization scheme and the replacement of $ { ( \ nabla h ) } ^ 2 $ by exponentially decreasing functions of that quantity to suppress instabilities. when applied to the equation in 1 + 1 dimensions, the method of instability control provides values of scaling amplitudes consistent with exactly known results, in contrast to the deviations generated by the original scheme. in 2 + 1 dimensions, we spanned a range of the model parameters where transients with edwards - wilkinson or random growth are not bserved, in box sizes $ 8 \ leq l \ leq 128 $. we obtain roughness exponent $ 0. 37 \ leq \ alpha \ leq 0. 40 $ and steady state height distributions with skewness $ s = 0. 25 \ pm 0. 01 $ and kurtosis $ q = 0. 15 \ pm 0. 1 $. these estimates are obtained after extrapolations to the large $ l $ limit, which is necessary due to significant finite - size effects in the estimates of effective exponents and height distributions. on the other hand, the steady state roughness distributions show weak scaling corrections and evidence of stretched exponentials tails. these results confirm previous estimates from lattice models, showing their reliability as representatives of the kpz class.
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arxiv:0806.0588
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this paper is concerned with the generation of gaussian invariant states in cascades of open quantum harmonic oscillators governed by linear quantum stochastic differential equations. we carry out infinitesimal perturbation analysis of the covariance matrix for the invariant gaussian state of such a system and the related purity functional subject to inaccuracies in the energy and coupling matrices of the subsystems. this leads to the problem of balancing the state - space realizations of the component oscillators through symplectic similarity transformations in order to minimize the mean square sensitivity of the purity functional to small random perturbations of the parameters. this results in a quadratic optimization problem with an effective solution in the case of cascaded one - mode oscillators, which is demonstrated by a numerical example. we also discuss a connection of the sensitivity index with classical statistical distances and outline infinitesimal perturbation analysis for translation invariant cascades of identical oscillators. the findings of the paper are applicable to robust state generation in quantum stochastic networks.
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arxiv:1706.04358
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recent qcd related results from the cdf and the d0 experiments are presented based on proton anti - proton collision data at sqrt ( s ) = 1. 96 tev, taken in run ii of the fermilab tevatron collider. measured observables include inclusive photon and diphoton production, vector boson plus jets production, event shape variables, and inclusive multijet production. the measurement results are compared to qcd theory calculations in different approximations. a determination of the strong coupling constant from jet data is presented.
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arxiv:1202.0205
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the audible universe project aims at making dialogue between two scientific domains investigating two distinct research objects, briefly said, stars and sound. it has been instantiated within a collaborative workshop that started to mutually acculturate both communities, by sharing and transmitting respective knowledge, skills and practices. one main outcome of this exchange was a global view on the astronomical data sonification paradigm that allowed to observe either the diversity of tools, uses and users ( including visually - impaired people ), but also the current limitations and potential ways of improvement. from this perspective, the current paper presents basic elements gathered and contextualised by sound experts in their respective fields ( sound perception / cognition, sound design, psychoacoustics, experimental psychology ), in order to anchor sonification for astronomy in a more well - informed, methodological and creative process.
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arxiv:2211.12725
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isothermal fluid turbulence simulations have been performed in the edge and scrape - off - layer ( sol ) of an analytic stellarator configuration with an island divertor, thereby providing numerical insight into edge turbulence in regions around islands in a stellarator. the steady - state transport follows the 1 / r curvature drive toward the outboard side, but large fluctuations are present throughout the island divertor region, with the average wavelength of similar size to the island width. the system exhibits a prominent m = 2, n = 5 mode, although other modes are present. the amplitude and radial extent of the density fluctuations are similar throughout the edge and sol, but can decrease near island o - points. the fluctuations exhibit a predominantly positive skewness on the outboard midplane, indicating blob - like perturbations for the transport into the outer sol. it is determined that a point on the separatrix is generally more correlated with regions outside of the sol than a nearby reference point which does not lie on the separatrix.
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arxiv:2403.18220
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fega $ _ 3 $ is an unusual intermetallic semiconductor that presents intriguing magnetic responses to the tuning of its electronic properties. when doped with ge, the system evolves from diamagnetic to paramagnetic to ferromagnetic ground states that are not well understood. in this work, we have performed a joint theoretical and experimental study of fega $ _ { 3 - x } $ ge $ _ x $ using density functional theory and magnetic susceptibility measurements. for low ge concentrations we observe the formation of localized moments on some fe atoms and, as the dopant concentration increases, a more delocalized magnetic behavior emerges. the magnetic configuration strongly depends on the dopant distribution, leading even to the appearance of antiferromagnetic interactions in certain configurations.
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arxiv:1506.07159
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consider the focusing energy - critical wave equation in space dimension 3, 4 or 5. we prove that any global solution which is bounded in the energy space converges in the exterior of wave cones to a radiation term which is a solution of the linear wave equation.
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arxiv:1601.02107
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we have obtained h $ \ alpha $ ccd images of 21 compact planetary nebulae in the galactic bulge. all objects are resolved and, after deconvolving the seeing disk, we find diameters of 1 - - 2 $ ' ' $ with typical uncertainties of 20 \ %. the values are generally in good agreement with radio measurements but are smaller than older optical measurements. based on the new values, we find that the shklovsky method for distance determination greatly overestimates the actual distance for all of our objects.
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arxiv:astro-ph/9309020
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we study the quasi - local energy ( qle ) and the surface geometry for kerr spacetime in the boyer - lindquist coordinates without taking the slow rotation approximation. we also consider in the region $ r \ leq2m $, which is inside the ergosphere. for a certain region, $ r > r _ { k } ( a ) $, the gaussian curvature of the surface with constant $ t, r $ is positive, and for $ r > \ sqrt { 3 } a $ the critical value of the qle is positive. we found that the three curves : the outer horizon $ r = r _ { + } ( a ) $, $ r = r _ { k } ( a ) $ and $ r = \ sqrt { 3 } a $ intersect at the point $ a = \ sqrt { 3 } m / 2 $, which is the limit for the horizon to be isometrically embedded into $ \ mathbb { r } ^ 3 $. the numerical result indicates that the kerr qle is monotonically decreasing to the adm $ m $ from the region inside the ergosphere to large $ r $. based on the second law of black hole dynamics, the qle is increasing with respect to the irreducible mass $ m _ { \ mathrm { ir } } $. from a results of chen - wang - yau, we conclude that in a certain region, $ r > r _ { h } ( a ) $, the critical value of the kerr qle is a global minimum.
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arxiv:1606.08177
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survival analysis is a fundamental area of focus in biomedical research, particularly in the context of personalized medicine. this prominence is due to the increasing prevalence of large and high - dimensional datasets, such as omics and medical image data. however, the literature on non - linear regression algorithms and variable selection techniques for interval - censoring is either limited or non - existent, particularly in the context of neural networks. our objective is to introduce a novel predictive framework tailored for interval - censored regression tasks, rooted in accelerated failure time ( aft ) models. our strategy comprises two key components : i ) a variable selection phase leveraging recent advances on sparse neural network architectures, ii ) a regression model targeting prediction of the interval - censored response. to assess the performance of our novel algorithm, we conducted a comprehensive evaluation through both numerical experiments and real - world applications that encompass scenarios related to diabetes and physical activity. our results outperform traditional aft algorithms, particularly in scenarios featuring non - linear relationships.
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arxiv:2206.06885
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in this paper we define a dirichlet - to - neumann map for a twisted dirac laplacian acting on bundle - valued spinors over a spin manifold. we show that this map is a pseudodifferential operator of order 1 whose symbol determines the taylor series of the metric and connection at the boundary. we go on to show that if two real - analytic connections couple to a spinor via the yang - - mills - - dirac equations with appropriate boundary conditions, and have equal dirichlet - to - neumann maps, then the two connections are locally gauge equivalent. in the abelian case, the connections are globally gauge equivalent.
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arxiv:2204.04854
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hadronic decays of boosted resonances, e. g., top quark jets, at hadronic super colliders are frequent predictions in tev - scale extensions of the standard model of particle physics. in such scenarios, accurate modeling of qcd radiation is necessary for trustworthy predictions. we present the automation of fully differential, next - to - leading - order ( nlo ) in qcd corrections with parton shower ( ps ) matching for an effective left - right symmetric model ( lrsm ) that features $ w _ r ^ \ pm, z _ r $ gauge bosons and heavy majorana neutrinos $ n $. publicly available universal model files require remarkably fewer user inputs for predicting benchmark collider processes than leading order lrsm constructions. we present predictions for inclusive $ w _ r ^ \ pm, z _ r $ production at the $ \ sqrt { s } = 13 $ tev large hadron collider ( lhc ) and a hypothetical future 100 tev very large hadron collider ( vlhc ), as well as inclusive $ n $ production for a hypothetical large hadron electron collider ( lhec ). as a case study, we investigate at nlo + ps accuracy the properties of heavy neutrino ( color - singlet ) jets and top quark ( color - triplet ) jets from decays of high - mass $ w _ r $ bosons at the lhc. contrary to top jets, we find that the kinematic properties of heavy neutrinos jets, and in particular jet mass, are resilient against the effects of parton showers and hard qcd radiation. this suggests that in searches for neutrino jets, aggressive selection cuts that would otherwise be inappropriate for top jets can be imposed with minimal signal loss.
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arxiv:1610.08985
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airports worldwide are actively promoting the transition of ground service vehicles from traditional fuel - powered vehicles to electric vehicles. the key to the successful implementation of this transition lies in the development of efficient electric vehicle dispatching models that comprehensively consider the charge - discharge processes of electric vehicles. however, due to the nonlinear characteristics of charge - discharge processes, finding precise solutions poses a significant challenge. previous researchers have often used traditional energy consumption models and constant charging rates to simplify calculations, but this has resulted in inaccurate estimates of the remaining battery charge level. furthermore, the lack of diverse pacing and charging strategies for airport ground service vehicles necessitates more adaptable solutions to enhance operational efficiency. to address these challenges, this paper uses airport electric tractors as a case study, develops an accurate model that takes into account the start - stop process and a piecewise linear charging function, designs an improved genetic algorithm that incorporates a greedy algorithm and an adaptive strategy, and develops charge - discharge coupling strategies for different configuration scenarios at nanjing lukou airport to meet current and future needs. the research results indicate that compared to traditional genetic algorithms, the proposed improved genetic algorithm significantly enhances solution accuracy and convergence speed. additionally, with the increase in flight scale, airports can appropriately enhance their charging strategies ; airports with dispersed aircraft stands should devise higher pacing strategies compared to those with dense aircraft stands.
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arxiv:2408.14746
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motivated by mail delivery scheduling problems arising in royal mail, we study a generalization of the fundamental makespan scheduling p | | cmax problem which we call the bounded job start scheduling problem. given a set of jobs, each specified by an integer processing time p _ j, that have to be executed non - preemptively by a set of m parallel identical machines, the objective is to compute a minimum makespan schedule subject to an upper bound g < = m on the number of jobs that may simultaneously begin per unit of time. with perfect input knowledge, we show that longest processing time first ( lpt ) algorithm is tightly 2 - approximate. after proving that the problem is strongly np - hard even when g = 1, we elaborate on improving the 2 - approximation ratio for this case. we distinguish the classes of long and short instances satisfying p _ j > = m and p _ j < m, respectively, for each job j. we show that lpt is 5 / 3 - approximate for the former and optimal for the latter. then, we explore scheduling long jobs in parallel with short jobs to obtain tightly satisfied packing and bounded job start constraints. for a broad family of instances excluding degenerate instances with many very long jobs, we derive a 1. 985 - approximation ratio. for general instances, we require machine augmentation to obtain better than 2 - approximate schedules. under uncertain job processing times, we exploit machine augmentation and lexicographic optimization to propose a two - stage robust optimization approach for bounded job start scheduling under uncertainty aiming in a low number of used machines. given a collection of schedules of makespan < = d, this approach allows distinguishing which are the more robust. we substantiate both the heuristics and our recovery approach numerically using royal mail data. we show that, for the royal mail application, machine augmentation, i. e. short - term van rental, is especially relevant.
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arxiv:1912.06862
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also launched missions to mercury in 2004, with the messenger probe demonstrating as the first use of a solar sail. nasa also launched probes to the outer solar system starting in the 1960s. pioneer 10 was the first probe to the outer planets, flying by jupiter, while pioneer 11 provided the first close up view of the planet. both probes became the first objects to leave the solar system. the voyager program launched in 1977, conducting flybys of jupiter and saturn, neptune, and uranus on a trajectory to leave the solar system. the galileo spacecraft, deployed from the space shuttle flight sts - 34, was the first spacecraft to orbit jupiter, discovering evidence of subsurface oceans on the europa and observed that the moon may hold ice or liquid water. a joint nasa - european space agency - italian space agency mission, cassini – huygens, was sent to saturn ' s moon titan, which, along with mars and europa, are the only celestial bodies in the solar system suspected of being capable of harboring life. cassini discovered three new moons of saturn and the huygens probe entered titan ' s atmosphere. the mission discovered evidence of liquid hydrocarbon lakes on titan and subsurface water oceans on the moon of enceladus, which could harbor life. finally launched in 2006, the new horizons mission was the first spacecraft to visit pluto and the kuiper belt. beyond interplanetary probes, nasa has launched many space telescopes. launched in the 1960s, the orbiting astronomical observatory were nasa ' s first orbital telescopes, providing ultraviolet, gamma - ray, x - ray, and infrared observations. nasa launched the orbiting geophysical observatory in the 1960s and 1970s to look down at earth and observe its interactions with the sun. the uhuru satellite was the first dedicated x - ray telescope, mapping 85 % of the sky and discovering a large number of black holes. launched in the 1990s and early 2000s, the great observatories program are among nasa ' s most powerful telescopes. the hubble space telescope was launched in 1990 on sts - 31 from the discovery and could view galaxies 15 billion light years away. a major defect in the telescope ' s mirror could have crippled the program, had nasa not used computer enhancement to compensate for the imperfection and launched five space shuttle servicing flights to replace the damaged components. the compton gamma ray observatory was launched from the atlantis on sts - 37 in 1991, discovering a possible source of antimatter at the center of the milky way and observing that the majority of gamma - ray bursts
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https://en.wikipedia.org/wiki/NASA
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" on exactitude in science ", or " on rigor in science " ( spanish : " del rigor en la ciencia " ) is a one - paragraph short story by argentine writer jorge luis borges. = = plot = = the story, credited fictionally as a quotation from " suarez miranda, viajes de varones prudentes, libro iv, cap. xlv, lerida, 1658 ", describes an empire where cartography becomes so exact that only a map on the same scale as the empire itself will suffice. later generations come to disregard the map, however, and as it decays, so does the land and society beneath it. = = publication history = = the story was first published in the march 1946 edition of los anales de buenos aires as part of a piece called " museo " credited to " b. lynch davis ", a joint pseudonym of borges and adolfo bioy casares. it was collected later that year in the 1946 second argentinian edition of borges ' historia universal de la infamia ( a universal history of infamy ). the story is no longer included in current spanish editions of the historia universal de la infamia, as since 1961 it has appeared as part of borges ' collection el hacedor. the names " b. lynch davis " and " suarez miranda " would be combined later in 1946 to form another pseudonym, b. suarez lynch, under which borges and bioy casares published un modelo para la muerte, a collection of detective fiction. = = influences and legacy = = " on exactitude in science " elaborates on a concept in lewis carroll ' s sylvie and bruno concluded : a fictional map that had " the scale of a mile to the mile. " one of carroll ' s characters notes some practical difficulties with this map and states that " we now use the country itself, as its own map, and i assure you it does nearly as well. " italian writer umberto eco expanded upon the theme, quoting the story as the epigraph for his short story " on the impossibility of drawing a map of the empire on a scale of 1 to 1 ", collected in his how to travel with a salmon and other essays. french philosopher jean baudrillard cited " on exactitude in science " as a predecessor to his concept of hyperreality in his 1981 treatise simulacra and simulation. = = see also = = map – territory relation welcome to
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https://en.wikipedia.org/wiki/On_Exactitude_in_Science
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in this study, we focus on the bosonic decays of light charged higgs boson ( i. e., with $ m _ { h ^ \ pm } < m _ t $ ) in the 2 - higgs doublet model ( 2hdm ) type - i. to study the signal of such a charged higgs state at the large hadron collider ( lhc ), in a scenario where the $ h ^ 0 $ boson is the standard model ( sm ) - like one already discovered, we assume that it decays mainly via $ h ^ 0w ^ { \ pm * } $ and / or $ h ^ \ pm \ to a ^ 0w ^ { \ pm * } $ ( i. e., via an off - shell $ w ^ { \ pm } $ boson ), which can reach a sizable branching ratio ( br ) for $ \ tan \ beta \ geq4 $, when the exclusion bounds from $ h ^ \ pm \ to \ tau \ nu $ and $ c { s } $ searches get weaker. by using six benchmark points ( bps ), which are consistent with current lhc constraints, we perform a monte carlo ( mc ) study and examine the sensitivity of the lhc to light charged higgs boson decaying via the above bosonic modes and produced in top decay following both single top and top pair production processes. our findings demonstrate that, when the integrated luminosity can reach 100 fb $ ^ { - 1 } $, the lhc has the potential to either discover or rule out most of these bps via either of these two production and decay channels or both.
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arxiv:2003.11108
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the imaging - time - of - propogation ( itop ) counter is a new type of ring - imaging cherenkov counter developed for particle identification at the belle ii experiment. it consists of 16 modules arranged azimuthally around the beam line. each module consists of one mirror, one prism and two quartz bar radiators. here we describe the design, acceptance test, alignment, gluing and assembly of the optical components. all itop modules have been successfully assembled and installed in the belle ii detector by the middle of 2016. after installation, laser and cosmic ray data have been taken to test the performance of the modules. first results from these tests are presented.
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arxiv:1710.02397
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a long - standing question in two dimensional anisotropic kepler problem ( akp ) concerns with the uniqueness of an unstable periodic orbit ( po ) for a given binary code ( modulo symmetry equivalence ). in this paper, a finite level ( $ n $ ) surface defined by the binary coding of the orbit is considered over the initial value domain $ d _ 0 $. it is proved that a tiling of $ d _ 0 $ by base ribbons of the surface steps is proper ; the surface height increases monotonously when ribbons are traversed from left to right. the mechanism of level $ n + 1 $ tiling creation from $ n $ one is clarified. two cases are possible depending on the code and the anisotropy. ( a ) every ribbon shrinks to a line at $ n \ rightarrow \ infty $. here the uniqueness holds. ( b ) when future ( f ) and past ( p ) ribbon become tangent each other, they escape from shrinking, then, the initial values of a stable po ( $ s $ ) and an unstable po ( $ u $ ) sharing the same code co - exist inside the overlap of f and p non - shrinking ribbons. this case corresponds to broucke ' s po. at high anisotropy, it is only case ( a ), but with decreasing anisotropy, bifurcation $ u ( r ) \ rightarrow s ( r ) + u ' ( nr ) $ occurs, along with the emergence of a non - shrinking ribbon. ( here $ r $ and $ nr $ are short for self - retracing and non - retracing po respectively ). we conjecture that case ( b ) occurs only for odd rank, $ y $ - symmetric pos from a classification based on topology and symmetry. we report two applications. first, the classification is applied successfully to the successive bifurcation ( above bifurcation is followed by $ s ( r ) \ rightarrow s ' ( r ) + s ' ' ( nr ) $ ) of a high - rank po ( $ n = 15 $ ). second, enhancing sensitivity to co - existence of s and u pos by ribbon tiling, we examine high anisotropy region. a new symmetry type po ( $ o $ type ) is found and, at $ \ gamma = 0. 2 $, all pos are unstable and unique. 13648 pos at rank 10 verifies that gutzwiller '
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arxiv:1902.09275
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deep learning models are vulnerable to adversarial examples and make incomprehensible mistakes, which puts a threat on their real - world deployment. combined with the idea of adversarial training, preprocessing - based defenses are popular and convenient to use because of their task independence and good generalizability. current defense methods, especially purification, tend to remove ` ` noise " by learning and recovering the natural images. however, different from random noise, the adversarial patterns are much easier to be overfitted during model training due to their strong correlation to the images. in this work, we propose a novel adversarial purification scheme by presenting disentanglement of natural images and adversarial perturbations as a preprocessing defense. with extensive experiments, our defense is shown to be generalizable and make significant protection against unseen strong adversarial attacks. it reduces the success rates of state - of - the - art \ textbf { ensemble } attacks from \ textbf { 61. 7 \ % } to \ textbf { 14. 9 \ % } on average, superior to a number of existing methods. notably, our defense restores the perturbed images perfectly and does not hurt the clean accuracy of backbone models, which is highly desirable in practice.
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arxiv:2110.07801
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the logarithmic potential is of great interest and relevance in the study of the dynamics of galaxies. some small corrections to the work of contopoulos & seimenis ( 1990 ) who used the method of prendergast ( 1982 ) to find periodic orbits and bifurcations within such a potential are presented. the solution of the orbital radial equation for the purely radial logarithmic potential is then considered using the p - ellipse ( precessing ellipse ) method pioneered by struck ( 2006 ). this differential orbital equation is a special case of the generalized burgers equation. the apsidal angle is also determined, both numerically as well as analytically by means of the lambert w and the polylogarithm functions. the use of these functions in computing the gravitational lensing produced by logarithmic potentials is discussed.
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arxiv:1209.1342
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distortion - based analysis has established itself as a fruitful framework for comparing voting mechanisms. m voters and n candidates are jointly embedded in an ( unknown ) metric space, and the voters submit rankings of candidates by non - decreasing distance from themselves. based on the submitted rankings, the social choice rule chooses a winning candidate ; the quality of the winner is the sum of the ( unknown ) distances to the voters. the rule ' s choice will in general be suboptimal, and the worst - case ratio between the cost of its chosen candidate and the optimal candidate is called the rule ' s distortion. it was shown in prior work that every deterministic rule has distortion at least 3, while the copeland rule and related rules guarantee worst - case distortion at most 5 ; a very recent result gave a rule with distortion $ 2 + \ sqrt { 5 } \ approx 4. 236 $. we provide a framework based on lp - duality and flow interpretations of the dual which provides a simpler and more unified way for proving upper bounds on the distortion of social choice rules. we illustrate the utility of this approach with three examples. first, we give a fairly simple proof of a strong generalization of the upper bound of 5 on the distortion of copeland, to social choice rules with short paths from the winning candidate to the optimal candidate in generalized weak preference graphs. a special case of this result recovers the recent $ 2 + \ sqrt { 5 } $ guarantee. second, using this generalized bound, we show that the ranked pairs and schulze rules have distortion $ \ theta ( \ sqrt ( n ) ) $. finally, our framework naturally suggests a combinatorial rule that is a strong candidate for achieving distortion 3, which had also been proposed in recent work. we prove that the distortion bound of 3 would follow from any of three combinatorial conjectures we formulate.
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arxiv:1911.07162
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the study of animal movement is challenging because it is a process modulated by many factors acting at different spatial and temporal scales. several models have been proposed which differ primarily in the temporal conceptualization, namely continuous and discrete time formulations. naturally, animal movement occurs in continuous time but we tend to observe it at fixed time intervals. to account for the temporal mismatch between observations and movement decisions, we used a state - space model where movement decisions ( steps and turns ) are made in continuous time. the movement process is then observed at regular time intervals. as the likelihood function of this state - space model turned out to be complex to calculate yet simulating data is straightforward, we conduct inference using a few variations of approximate bayesian computation ( abc ). we explore the applicability of these methods as a function of the discrepancy between the temporal scale of the observations and that of the movement process in a simulation study. we demonstrate the application of this model to a real trajectory of a sheep that was reconstructed in high resolution using information from magnetometer and gps devices. our results suggest that accurate estimates can be obtained when the observations are less than 5 times the average time between changes in movement direction. the state - space model used here allowed us to connect the scales of the observations and movement decisions in an intuitive and easy to interpret way. our findings underscore the idea that the time scale at which animal movement decisions are made needs to be considered when designing data collection protocols, and that sometimes high - frequency data may not be necessary to have good estimates of certain movement processes.
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arxiv:1907.10115
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instant messaging has become a predominant form of communication, with texts and emoticons enabling users to express emotions and ideas efficiently. emoticons, in particular, have gained significant traction as a medium for conveying sentiments and information, leading to the growing importance of emoticon retrieval and recommendation systems. however, one of the key challenges in this area has been the absence of datasets that capture both the temporal dynamics and user - specific interactions with emoticons, limiting the progress of personalized user modeling and recommendation approaches. to address this, we introduce the emoticon dataset, a comprehensive resource that includes time - based data along with anonymous user identifiers across different conversations. as the largest publicly accessible emoticon dataset to date, it comprises 22k unique users, 370k emoticons, and 8. 3m messages. the data was collected from a widely - used messaging platform across 67 conversations and 720 hours of crawling. strict privacy and safety checks were applied to ensure the integrity of both text and image data. spanning across 10 distinct domains, the emoticon dataset provides rich insights into temporal, multilingual, and cross - domain behaviors, which were previously unavailable in other emoticon - based datasets. our in - depth experiments, both quantitative and qualitative, demonstrate the dataset ' s potential in modeling user behavior and personalized recommendation systems, opening up new possibilities for research in personalized retrieval and conversational ai. the dataset is freely accessible.
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arxiv:2502.19108
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we construct locally lindel \ " of scattered p - spaces ( llsp spaces, in short ) with prescribed widths and heights under different set - theoretic assumptions. we prove that there is an llsp space of width $ \ omega _ 1 $ and height $ \ omega _ 2 $ and that it is relatively consistent with zfc that there is an llsp space of width $ \ omega _ 1 $ and height $ \ omega _ 3 $. also, we prove a stepping up theorem that, for every cardinal $ \ lambda \ geq \ omega _ 2 $, permits us to construct from an llsp space of width $ \ omega _ 1 $ and height $ \ lambda $ satisfying certain additional properties an llsp space of width $ \ omega _ 1 $ and height $ \ alpha $ for every ordinal $ \ alpha < \ lambda ^ + $. then, we obtain as consequences of the above results the following theorems : ( 1 ) for every ordinal $ \ alpha < \ omega _ 3 $ there is an llsp space of width $ \ omega _ 1 $ and height $ \ alpha $. ( 2 ) it is relatively consistent with zfc that there is an llsp space of width $ \ omega _ 1 $ and height $ \ alpha $ for every ordinal $ \ alpha < \ omega _ 4 $.
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arxiv:2111.05038
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we study the exponential ornstein - uhlenbeck stochastic volatility model and observe that the model shows a multiscale behavior in the volatility autocorrelation. it also exhibits a leverage correlation and a probability profile for the stationary volatility which are consistent with market observations. all these features make the model quite appealing since it appears to be more complete than other stochastic volatility models also based on a two - dimensional diffusion. we finally present an approximate solution for the return probability density designed to capture the kurtosis and skewness effects.
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arxiv:cond-mat/0501639
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let $ g $ be a finite group and construct a graph $ \ delta ( g ) $ by taking $ g \ setminus \ { 1 \ } $ as the vertex set of $ \ delta ( g ) $ and by drawing an edge between two vertices $ x $ and $ y $ if $ \ langle x, y \ rangle $ is cyclic. let $ k ( g ) $ be the set consisting of the universal vertices of $ \ delta ( g ) $ along the identity element. for a solvable group $ g $, we present a necessary and sufficient conditon for $ k ( g ) $ to be nontrivial. we also develop a connection between $ \ delta ( g ) $ and $ k ( g ) $ when $ | g | $ is divisible by two distinct primes and the diameter of $ \ delta ( g ) $ is $ 2 $.
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arxiv:2402.06157
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we present a method for estimating the number of shots required for some desired variance in the results of a quantum circuit. first, we establish a baseline for a single qubit characterization of individual noise sources separately. we then extend the method to multi - qubit problems and test our method on two case studies. we will proceed to estimate the number of shots required for a desired variance in the result or, equivalently estimate the variance at a known number of shots. we will show we ' re able to estimate variance accurately to within a factor of 2. following these, we also provide a closed - form expression for variance at a given number of shots.
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arxiv:2501.03194
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we construct uncountably many infinite characters of type ii for $ sl _ n ( \ mathbb { z } ) $, $ n \ geq 2 $.
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arxiv:2111.11754
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we discuss a structural approach to subset - sum problems in additive combinatorics. the core of this approach are freiman - type structural theorems, many of which will be presented through the paper. these results have applications in various areas, such as number theory, combinatorics and mathematical physics.
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arxiv:0804.3211
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we consider a finite group acting on a vector space and the corresponding skew group algebra generated by the group and the symmetric algebra of the space. this skew group algebra illuminates the resulting orbifold and serves as a replacement for the ring of invariant polynomials, especially in the eyes of cohomology. one analyzes the hochschild cohomology of the skew group algebra using isomorphisms which convert between resolutions. we present an explicit chain map from the bar resolution to the koszul resolution of the symmetric algebra which induces various isomorphisms on hochschild homology and cohomology, some of which have appeared in the literature before. this approach unifies previous results on homology and cohomology of both the symmetric algebra and skew group algebra. we determine induced combinatorial cochain maps which invoke quantum differentiation ( expressed by demazure - bbg operators ).
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arxiv:0911.0917
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graph neural networks ( gnns ) are powerful machine learning models that excel at analyzing structured data represented as graphs, demonstrating remarkable performance in applications like social network analysis and recommendation systems. however, classical gnns face scalability challenges when dealing with large - scale graphs. this paper proposes frameworks for implementing gnns on quantum computers to potentially address the challenges. we devise quantum algorithms corresponding to the three fundamental types of classical gnns : graph convolutional networks, graph attention networks, and message - passing gnns. a complexity analysis of our quantum implementation of the simplified graph convolutional ( sgc ) network shows potential quantum advantages over its classical counterpart, with significant improvements in time and space complexities. our complexities can have trade - offs between the two : when optimizing for minimal circuit depth, our quantum sgc achieves logarithmic time complexity in the input sizes ( albeit at the cost of linear space complexity ). when optimizing for minimal qubit usage, the quantum sgc exhibits space complexity logarithmic in the input sizes, offering an exponential reduction compared to classical sgcs, while still maintaining better time complexity. these results suggest our quantum gnn frameworks could efficiently process large - scale graphs. this work paves the way for implementing more advanced graph neural network models on quantum computers, opening new possibilities in quantum machine learning for analyzing graph - structured data.
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arxiv:2405.17060
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a possibility of explaining the anomalies in the semileptonic $ b $ - meson decay $ b \ to k ^ { * } \ mu \ bar \ mu $ has been explored in the framework of the gauged $ u ( 1 ) _ { \ mu - \ tau } $ symmetry. apart from the muon anomalous magnetic moment and neutrino sector, we formulate the model starting with a valid lagrangian and consider the constraints from the neutral meson mixings, the bounds on direct detection and the relic density of the bosonic dark matter candidate augmented to collider constraints. we search the parameter space, which accommodates the size of the anomaly of the $ b \ rightarrow k ^ * \ mu \ bar \ mu $ decay, to satisfy all experimental constraints. we found the allowed region on the plane of the dark matter and $ z ' $ masses is a rather narrow compared to the previous analysis.
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arxiv:1901.03932
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a self - dual generalization of the lump - impurity system is introduced. this model possesses lump - antilump - like pairs as static solutions of the pertinent bogomolny equations. this allows for a moduli space approximation analysis of the bps solutions which are identified as lump - antilump configurations. some geometrical properties of the resulting moduli are analyzed. in addition, it is argued that, this type of impurity models can be interpreted as a limit of certain non - impurity theories.
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arxiv:2112.02122
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in this work, we numerically investigate flow instabilities of inertialess circular couette flow of dilute wormlike micelle solutions. using the reformulated reactive rod model ( rrm - r ) [ hommel and graham, jnnfm 295 ( 2021 ) 104606 ], which treats micelles as rigid brownian rods undergoing reversible scission and fusion in flow, we study the development and behavior of both vorticity banding and finger - like instabilities. in particular, we focus on solutions that exhibit reentrant constitutive curves, in which there exists some region where the shear stress, $ \ tau $, has a multivalued relation to shear rate, $ \ dot { \ gamma } $. we find that the radial dependence of the shear stress in circular couette flow allows for solutions in which parts of the domain lie in the region of the flow curve where $ \ partial \ tau / \ partial \ dot { \ gamma } > 0 $, while others lie in the region where $ \ partial \ tau / \ partial \ dot { \ gamma } < 0 $ ; this mixed behavior can lead to complex flow instabilities that manifest as finger - like structures of elongated and anisotropically - oriented micelles. in 3d simulations we find that the initial instability is 2d in origin, and 3d finger - like structures arise through the axial instability of 2d sheets. finally, we show that the rrm - r can capture vorticity banding in narrow - gap circular couette flow and that vorticity bands are linearly stable to perturbations.
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arxiv:2309.02554
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instruction - tuned large language models ( llms ) show impressive results in numerous practical applications, but they lack essential safety features that are common in other areas of computer science, particularly an explicit separation of instructions and data. this makes them vulnerable to manipulations such as indirect prompt injections and generally unsuitable for safety - critical tasks. surprisingly, there is currently no established definition or benchmark to quantify this phenomenon. in this work, we close this gap by introducing a formal measure for instruction - data separation and an empirical variant that is calculable from a model ' s outputs. we also present a new dataset, sep, that allows estimating the measure for real - world models. our results on various llms show that the problem of instruction - data separation is real : all models fail to achieve high separation, and canonical mitigation techniques, such as prompt engineering and fine - tuning, either fail to substantially improve separation or reduce model utility. the source code and sep dataset are openly accessible at https : / / github. com / egozverev / shold - it - be - executed - or - processed.
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arxiv:2403.06833
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in this work we study the analogues of r - matrices that arise in 5d non - commutative topological - holomorphic chern - simons theory, which is known to describe twisted m - theory. we first study the intersections of line and surface operators in 5d chern - simons theory, which correspond to m2 - and m5 - branes, respectively. a feynman diagram computation of the correlation function of this configuration furnishes an expression reminiscent of an r - matrix derivable from 4d chern - simons theory. we explain how this object is related to a miura operator that is known to realize ( matrix - extended ) $ w _ { \ infty } $ - algebras. for 5d chern - simons theory with nonabelian gauge group, we then perform a feynman diagram computation of coproducts for deformed double current algebras and matrix - extended $ w _ { \ infty } $ - algebras from fusions of m2 - branes, m5 - branes, and m2 - m5 intersections.
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arxiv:2408.15732
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wigner crystals are prime candidates for the realization of regular electron lattices under minimal requirements on external control and electronics. however, several technical challenges have prevented their detailed experimental investigation and applications to date. we propose an implementation of two - dimensional electron lattices for quantum simulation of ising spin systems based on self - assembled wigner crystals in transition - metal dichalcogenides. we show that these semiconductors allow for minimally invasive all - optical detection schemes of charge ordering and total spin. for incident light with optimally chosen beam parameters and polarization, we predict a strong dependence of the transmitted and reflected signals on the underlying lattice periodicity, thus revealing the charge order inherent in wigner crystals. at the same time, the selection rules in transition - metal dichalcogenides provide direct access to the spin degree of freedom via faraday rotation measurements.
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arxiv:1912.11089
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fighting fantasy is a popular recreational fantasy gaming system worldwide. combat in this system progresses through a stochastic game involving a series of rounds, each of which may be won or lost. each round, a limited resource ( ` luck ' ) may be spent on a gamble to amplify the benefit from a win or mitigate the deficit from a loss. however, the success of this gamble depends on the amount of remaining resource, and if the gamble is unsuccessful, benefits are reduced and deficits increased. players thus dynamically choose to expend resource to attempt to influence the stochastic dynamics of the game, with diminishing probability of positive return. the identification of the optimal strategy for victory is a markov decision problem that has not yet been solved. here, we combine stochastic analysis and simulation with dynamic programming to characterise the dynamical behaviour of the system in the absence and presence of gambling policy. we derive a simple expression for the victory probability without luck - based strategy. we use a backward induction approach to solve the bellman equation for the system and identify the optimal strategy for any given state during the game. the optimal control strategies can dramatically enhance success probabilities, but take detailed forms ; we use stochastic simulation to approximate these optimal strategies with simple heuristics that can be practically employed. our findings provide a roadmap to improving success in the games that millions of people play worldwide, and inform a class of resource allocation problems with diminishing returns in stochastic games.
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arxiv:2002.10172
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we present the mathematica package hypexp which allows to expand hypergeometric functions $ _ jf _ { j - 1 } $ around integer parameters to arbitrary order. at this, we apply two methods, the first one being based on an integral representation, the second one on the nested sums approach. the expansion works for both symbolic argument $ z $ and unit argument. we also implemented new classes of integrals that appear in the first method and that are, in part, yet unknown to mathematica.
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arxiv:hep-ph/0507094
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restoring degraded music signals is essential to enhance audio quality for downstream music manipulation. recent diffusion - based music restoration methods have demonstrated impressive performance, and among them, diffusion posterior sampling ( dps ) stands out given its intrinsic properties, making it versatile across various restoration tasks. in this paper, we identify that there are potential issues which will degrade current dps - based methods ' performance and introduce the way to mitigate the issues inspired by diverse diffusion guidance techniques including the repaint ( rp ) strategy and the pseudoinverse - guided diffusion models ( $ \ pi $ gdm ). we demonstrate our methods for the vocal declipping and bandwidth extension tasks under various levels of distortion and cutoff frequency, respectively. in both tasks, our methods outperform the current dps - based music restoration benchmarks. we refer to \ url { http : / / carlosholivan. github. io / demos / audio - restoration - 2023. html } for examples of the restored audio samples.
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arxiv:2309.06934
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the cuore experiment is a large bolometric array searching for the lepton number violating neutrino - less double beta decay ( $ 0 \ nu \ beta \ beta $ ) in the isotope $ \ mathrm { ^ { 130 } te } $. in this work we present the latest results on two searches for the double beta decay ( dbd ) of $ \ mathrm { ^ { 130 } te } $ to the first $ 0 ^ { + } _ 2 $ excited state of $ \ mathrm { ^ { 130 } xe } $ : the $ 0 \ nu \ beta \ beta $ decay and the standard model - allowed two - neutrinos double beta decay ( $ 2 \ nu \ beta \ beta $ ). both searches are based on a 372. 5 kg $ \ times $ yr teo $ _ 2 $ exposure. the de - excitation gamma rays emitted by the excited xe nucleus in the final state yield a unique signature, which can be searched for with low background by studying coincident events in two or more bolometers. the closely packed arrangement of the cuore crystals constitutes a significant advantage in this regard. the median limit setting sensitivities at 90 \ % credible interval ( c. i. ) of the given searches were estimated as $ \ mathrm { s ^ { 0 \ nu } _ { 1 / 2 } = 5. 6 \ times 10 ^ { 24 } \ : \ mathrm { yr } } $ for the $ { 0 \ nu \ beta \ beta } $ decay and $ \ mathrm { s ^ { 2 \ nu } _ { 1 / 2 } = 2. 1 \ times 10 ^ { 24 } \ : \ mathrm { yr } } $ for the $ { 2 \ nu \ beta \ beta } $ decay. no significant evidence for either of the decay modes was observed and a bayesian lower bound at $ 90 \ % $ c. i. on the decay half lives is obtained as : $ \ mathrm { ( t _ { 1 / 2 } ) ^ { 0 \ nu } _ { 0 ^ + _ 2 } > 5. 9 \ times 10 ^ { 24 } \ : \ mathrm { yr } } $ for the $ 0 \ nu \ beta \ beta $ mode and $ \ mathrm { ( t _ { 1 / 2 } ) ^ { 2 \ nu } _ { 0 ^ + _ 2 } > 1. 3 \ times
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arxiv:2101.10702
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in both quantum mechanics and relativity theory, the concept of the observer plays a critical role. however, there is no consensus on the definition of observer in these theories. following einstein ' s thought experiments, one could ask : what would it look like to sit inside a photon or to be a photon? and what type of observer could represent this more global perspective of the photon ' s interior? to address these questions, we introduce the concepts of internal and external observers with a focus on their relationship in quantum theory and relativity theory. the internal observer, associated with the internal observables super - algebra, glues the external interactions. drawing inspiration from the advancements in abstract algebraic topology, we propose mathematical representation of the internal observer. we also outline principles for ensuring the consistency of observers in terms of information theory. it becomes evident, through the analysis of the introduced hierarchy of observers, that entanglement is a primitive of space - time causal relationships. while external observers must abide by the relativistic causality linked with the no - signaling principle in quantum mechanics, the internal observer is inherently non - local and may be acausal. however, its consistency is maintained through the formulation of the self - consistency principle. one of the goals of this paper is to construct the representation of the internal observer from the local external algebra of observables, which can be associated with external observers. additionally, we demonstrate how the concepts of internal and external observers can be applied in the fields of quantum information theory, algebraic quantum field theory, and loop quantum gravity. the concept of internal observer seems to be also fundamental for further development of quantum gravity.
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arxiv:2304.01677
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jammed particulate systems composed of various shapes of particles undergo the jamming transition as they are compressed or decompressed. to date, sphere packings have been extensively studied in many previous works, where isostaticity at the transition and scaling laws with the pressure of various quantities, including the contact number and the vibrational density of states, have been established. additionally, much attention has been paid to nonspherical packings, and particularly recent work has made progress in understanding ellipsoidal packings. in the present work, we study the dimer packings in two dimensions, which have been much less understood than systems of spheres and ellipsoids. we first study the contact number of dimers near the jamming transition. it turns out that packings of dimers have " rotational rattlers ", each of which still has a free rotational motion. after correcting this effect, we show that dimers become isostatic at the jamming, and the excess contact number obeys the same critical law and finite size scaling law as those of spheres. we next study the vibrational properties of dimers near the transition. we find that the vibrational density of states of dimers exhibits two characteristic plateaus that are separated by a peak. the high - frequency plateau is dominated by the translational degree of freedom, while the low - frequency plateau is dominated by the rotational degree of freedom. we establish the critical scaling laws of the characteristic frequencies of the plateaus and the peak near the transition. in addition, we present detailed characterizations of the real space displacement fields of vibrational modes in the translational and rotational plateaus.
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arxiv:1905.02966
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a model for the acoustic production of gravitational waves at a first order phase transition is presented. the source of gravitational radiation is the sound waves generated by the explosive growth of bubbles of the stable phase. the model assumes that the sound waves are linear and that their power spectrum is determined by the characteristic form of the sound shell around the expanding bubble. the predicted power spectrum has two length scales, the average bubble separation and the sound shell width when the bubbles collide. the peak of the power spectrum is at wavenumbers set by the sound shell width. for higher wavenumber $ k $, the power spectrum decreases as $ k ^ { - 3 } $. at wavenumbers below the inverse bubble separation, the power spectrum goes as $ k ^ 5 $. for bubble wall speeds near the speed of sound where these two length scales are distinguished, there is an intermediate $ k ^ { 1 } $ power law. the detailed dependence of the power spectrum on the wall speed and the other parameters of the phase transition raises the possibility of their constraint or measurement at a future space - based gravitational wave observatory such as elisa.
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arxiv:1608.04735
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this paper is devoted to the study of generalized differentiation properties of the infimal convolution. this class of functions covers a large spectrum of nonsmooth functions well known in the literature. the subdifferential formulas obtained unify several known results and allow us to characterize the differentiability of the infimal convolution which plays an important role in variational analysis and optimization.
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arxiv:1404.0787
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two types of coseismic magnetic field events are simultaneously observed : transient offset events and magnetic field signal that occurred at the destructive, mw6. 1 laquila earthquake ( eq ) mainshock. the offset event, conventionally interpreted as a signature of piezomagnetic effects, however could not be ascribed as such. the reason is that the presently known geology of the laquila basin consists mainly of carbonates, dolomites and limestone, thus it does not suggest an appearance of piezomagnetic related effects under eq fracture / slip events. the second type of coseismic event, the transient magnetic signal starts simultaneously with the offset event and reaches amplitude of 0. 8 nt in the total magnetic field. the signal is local one, in the sense that its form differs from the signals of ionospheric / magnetospheric origin confirmed ( indirectly ) by additional magnetic field data in italy and central europe. the reliability of the observed local signal is examined also : it follows from the fact that the transient signal is recorded by two different measurements : i ) in components ( by fluxgate magnetometers ) and 2 ) absolute one ( overhauser magnetometer ), it persists after the seismic wave train passage but within the first five minutes after the eq shock and is not a consequence of ionosphere disturbances caused by the seismic wave train. its amplitude shape resembles diffusion - like form with time scale characteristics that are indicative for a source deep in the crust. the polarity of the transient signal is in the horizontal plane and nearly parallel to the laquila fault strike, i. e. along the nw - se direction.
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arxiv:1506.05938
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we investigate a spectrum of a fermion, which we call a quark, above the critical temperature of the chiral phase transition in a gauge theory using the schwinger - dyson ( sd ) equation. the sd equation enables us to study the spectrum over a wide range of the gauge coupling. it is shown that the quark spectrum has two sharp peaks which correspond to the normal quasi - quark and the plasmino and is consistent with that obtained in the hard thermal loop approximation in the weak coupling region, while it has also two peaks but with smaller thermal masses and broader widths in the strong coupling region. temperature - dependence of the quark spectrum is also discussed.
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arxiv:hep-ph/0702253
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we investigate experimentally parity - time ( $ { \ cal pt } $ ) symmetric scattering using $ lrc $ circuits in an inductively coupled $ { \ cal pt } $ - symmetric pair connected to transmission line leads. in the single - lead case, the $ { \ cal pt } $ - symmetric circuit acts as a simple dual device - an amplifier or an absorber depending on the orientation of the lead. when a second lead is attached, the system exhibits unidirectional transparency for some characteristic frequencies. this non - reciprocal behavior is a consequence of generalized ( non - unitary ) conservation relations satisfied by the scattering matrix.
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arxiv:1205.2176
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impurities immersed in a bose - einstein condensate ( bec ) can interact indirectly through the exchange of bogoliubov excitations. these impurities, which form dressed quasiparticles known as bose polarons due to their interaction with the bec, can pair up to form a bound state called bipolarons, via an induced interaction. previous studies on induced interactions have primarily focused on cases with an isotropic excitation spectrum. in this work, we investigate the properties of induced interactions and bipolarons mediated by anisotropic bogoliubov excitations using field theory. taking a bec with spin - orbit coupling as an example, we show that the induced interaction becomes anisotropic. notably, a double - minima feature appears in the induced interaction in momentum space due to the exchange of roton excitations. additionally, we calculate the binding energy and wave functions of these bipolarons induced by anisotropic interactions. unlike previously studied bipolarons formed through the exchange of isotropic phonon excitations, we identify a new type of bipolarons whose wave functions feature a double - peak structure under strong impurity - boson interactions. our work extends the theory of induced interactions from isotropic to anisotropic systems, and reveals the novel features in both the induced interactions and bipolarons arising from bec with an unconventional excitation spectrum.
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arxiv:2501.16657
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we have measured the electrical conductivity of nominally uncompensated ^ { 70 } ge : ga samples in magnetic fields up to b = 8 t at low temperatures ( t = 0. 05 - 0. 5 k ) in order to investigate the metal - insulator transition in magnetic fields. the values of the critical exponents in magnetic fields are consistent with the scaling theories.
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arxiv:cond-mat/0206256
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we study a graph partitioning problem motivated by the simulation of the physical movement of multi - body systems on an atomistic level, where the forces are calculated from a quantum mechanical description of the electrons. several advanced algorithms have been published in the literature for such simulations that are based on evaluations of matrix polynomials. we aim at efficiently parallelizing these computations by using a special type of graph partitioning. for this, we represent the zero - nonzero structure of a thresholded matrix as a graph and partition that graph into several components. the matrix polynomial is then evaluated for each separate submatrix corresponding to the subgraphs and the evaluated submatrix polynomials are used to assemble the final result for the full matrix polynomial. the paper provides a rigorous definition as well as a mathematical justification of this partitioning problem. we use several algorithms to compute graph partitions and experimentally evaluate their performance with respect to the quality of the partition obtained with each method and the time needed to produce it.
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arxiv:1605.01118
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in this paper, we investigate the problem of coordination between economic dispatch ( ed ) and demand response ( dr ) in multi - energy systems ( mess ), aiming to improve the economic utility and reduce the waste of energy in mess. since multiple energy sources are coupled through energy hubs ( ehs ), the supply - demand constraints are nonconvex. to deal with this issue, we propose a linearization method to transform the coordination problem to a convex social welfare optimization one. then a decentralized algorithm based on parallel alternating direction method of multipliers ( admm ) and dynamic average tracking protocol is developed, where each agent could only make decisions based on information from their neighbors. moreover, by using variational inequality and lyapunov - based techniques, we show that our algorithm could always converge to the global optimal solution. finally, a case study on the modified ieee 14 - bus network verifies the feasibility and effectiveness of our algorithm.
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arxiv:2103.13680
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recently, deep learning methods have made great progress in traffic prediction, but their performance depends on a large amount of historical data. in reality, we may face the data scarcity issue. in this case, deep learning models fail to obtain satisfactory performance. transfer learning is a promising approach to solve the data scarcity issue. however, existing transfer learning approaches in traffic prediction are mainly based on regular grid data, which is not suitable for the inherent graph data in the traffic network. moreover, existing graph - based models can only capture shared traffic patterns in the road network, and how to learn node - specific patterns is also a challenge. in this paper, we propose a novel transfer learning approach to solve the traffic prediction with few data, which can transfer the knowledge learned from a data - rich source domain to a data - scarce target domain. first, a spatial - temporal graph neural network is proposed, which can capture the node - specific spatial - temporal traffic patterns of different road networks. then, to improve the robustness of transfer, we design a pattern - based transfer strategy, where we leverage a clustering - based mechanism to distill common spatial - temporal patterns in the source domain, and use these knowledge to further improve the prediction performance of the target domain. experiments on real - world datasets verify the effectiveness of our approach.
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arxiv:2207.01301
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we report chandra and xmm - newton observations of the transient neutron star low - mass x - ray binary grs 1741. 9 - 2853. chandra detected the source in outburst on 2000 october 26 at an x - ray luminosity of ~ 10 ^ { 36 } erg / s ( 2 - - 8 kev ; 8 kpc ), and in quiescence on 2001 july 18 at ~ 10 ^ { 32 } erg / s. the latter observation is the first detection of grs 1741. 9 - 2853 in quiescence. we obtain an accurate position for the source of 17h 45m 2. 33s, - 28o 54 ' 49. 7 " ( j2000 ), with an uncertainty of 0. 7 ". grs 1741. 9 - 2853 was not detected significantly in three other chandra observations, nor in three xmm - newton observations, indicating that the luminosity of the source in quiescence varies by at least a factor of 5 between ( < 0. 9 - 5. 0 ) \ times 10 ^ { 32 } erg / s ( 2 - - 8 kev ). a weak x - ray burst with a peak luminosity of 5 \ times 10 ^ { 36 } erg / s above the persistent level was observed with chandra during the outburst on 2000 october 26. the energy of this burst, 10 ^ { 38 } erg, is unexpectedly low, and may suggest that the accreted material is confined to the polar caps of the neutron star. a search of the literature reveals that grs 1741. 9 - 2853 was observed in outburst with asca in fall 1996 as well, when the bepposax wfc detected the three previous x - ray bursts from this source. the lack of x - ray bursts from grs 1741. 9 - 2853 at other epochs suggests that it produces bursts only during transient outbursts when the accretion rate onto the surface of the neutron star is about 10 ^ { - 10 } m _ sun / yr. a similar situation may hold for other low - luminosity bursters recently identified from wfc data.
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arxiv:astro-ph/0307179
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the dynamics of quantum fisher information ( qfi ) of the phase parameter in a driven two - state system is studied within the framework of non - markovian dissipative process. the influences of memory effects, classical driving and detunings on the parameter - estimation precision are demonstrated by exactly solving the hamiltonian under rotating - wave approximation. in sharp contrast with the results obtained in the presence of markovian dissipation, we find that classical driving can drastically enhance the qfi, namely, the precision of parameter estimation in the non - markovian regime. moreover, the parameter - estimation precision may even be preserved from the influence of surrounding non - markovian dissipation with the assistance of classical driving. remarkably, we reveal that the enhancement and preservation of qfi highly depend on the combination of classical driving and non - markovian effects. finally, a phenomenological explanation of the underlying mechanism is presented in detail via the quasimode theory
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arxiv:1503.02260
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off - policy learning to rank ( ltr ) aims to optimize a ranker from data collected by a deployed logging policy. however, existing off - policy learning to rank methods often make strong assumptions about how users generate the click data, i. e., the click model, and hence need to tailor their methods specifically under different click models. in this paper, we unified the ranking process under general stochastic click models as a markov decision process ( mdp ), and the optimal ranking could be learned with offline reinforcement learning ( rl ) directly. building upon this, we leverage offline rl techniques for off - policy ltr and propose the click model - agnostic unified off - policy learning to rank ( cuolr ) method, which could be easily applied to a wide range of click models. through a dedicated formulation of the mdp, we show that offline rl algorithms can adapt to various click models without complex debiasing techniques and prior knowledge of the model. results on various large - scale datasets demonstrate that cuolr consistently outperforms the state - of - the - art off - policy learning to rank algorithms while maintaining consistency and robustness under different click models.
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arxiv:2306.07528
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we present a c + + header - only parallel sparse matrix library, based on sparse quadtree representation of matrices using the chunks and tasks programming model. the library implements a number of sparse matrix algorithms for distributed memory parallelization that are able to dynamically exploit data locality to avoid movement of data. this is demonstrated for the example of block - sparse matrix - matrix multiplication applied to three sequences of matrices with different nonzero structure, using the cht - mpi 2. 0 runtime library implementation of the chunks and tasks model. the runtime library succeeds to dynamically load balance the calculation regardless of the sparsity structure.
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arxiv:2011.11762
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video streaming services depend on the underlying communication infrastructure and available network resources to offer ultra - low latency, high - quality content delivery. open radio access network ( oran ) provides a dynamic, programmable, and flexible ran architecture that can be configured to support the requirements of time - critical applications. this work considers a setup in which the constrained network resources are supplemented by \ gls { gai } and \ gls { mec } { techniques } in order to reach a satisfactory video quality. specifically, we implement a novel semantic control channel that enables \ gls { mec } to support low - latency applications by tight coupling among the oran xapp, \ gls { mec }, and the control channel. the proposed concepts are experimentally verified with an actual oran setup that supports video streaming. the performance evaluation includes the \ gls { psnr } metric and end - to - end latency. our findings reveal that latency adjustments can yield gains in image \ gls { psnr }, underscoring the trade - off potential for optimized video quality in resource - limited environments.
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arxiv:2412.12751
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topological states of matter possess bulk electronic structures categorized by topological invariants and edge / surface states due to the bulk - boundary correspondence. topological materials hold great potential in the development of dissipationless spintronics, information storage, and quantum computation, particularly if combined with magnetic order intrinsically or extrinsically. here, we review the recent progress in the exploration of intrinsic magnetic topological materials, including but not limited to magnetic topological insulators, magnetic topological metals, and magnetic weyl semimetals. we pay special attention to their characteristic band features such as the gap of topological surface state, gapped dirac cone induced by magnetization ( either bulk or surface ), weyl nodal point / line, and fermi arc, as well as the exotic transport responses resulting from such band features. we conclude with a brief envision for experimental explorations of new physics or effects by incorporating other orders in intrinsic magnetic topological materials.
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arxiv:2212.09057
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we report results from a 2003 fuse observation, and reanalysis of a 1996 hst observation of the unusual x - ray transient narrow - line seyfert 1 galaxy wpvs 007. the hst fos spectrum revealed mini - bals with v _ max ~ 900 km s ^ - 1 and fwhm ~ 550 km s ^ - 1. the fuse spectrum showed that an additional bal outflow with v _ max ~ 6000 km s ^ - 1 and fwhm ~ 3400 km s ^ - 1 had appeared. wpvs 007 is a low - luminosity object in which such a high velocity outflow is not expected ; therefore, it is an outlier on the m _ v / v _ max relationship. template spectral fitting yielded apparent ionic columns, and a cloudy analysis showed that the presence of pv requires a high ionization parameter log ( u ) > = 0 and high column density log ( n _ h ) > = 23 assuming solar abundances and a nominal sed for low - luminosity nls1s with alpha _ ox = - 1. 28. a recent long swift observation revealed the first hard x - ray detection and an intrinsic ( unabsorbed ) alpha _ ox ~ - 1. 9 $. using this sed in our analysis yielded lower column density constraints ( log ( n _ h ) > = 22. 2 for z = 1, or log ( n _ h ) > = 21. 6 if z = 5 ). the x - ray weak continuum, combined with x - ray absorption consistent with the uv lines, provides the best explanation for the observed swift x - ray spectrum. the large column densities and velocities implied by the uv data in any of these scenarios could be problematic for radiative acceleration. we also point out that since the observed pv absorption can be explained by lower total column densities using an intrinsically x - ray weak spectrum, we might expect to find pv absorption preferentially more often ( or stronger ) in quasars that are intrinsically x - ray weak.
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arxiv:0906.2149
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we study the dynamics of test particles and pointlike gyroscopes in 5d manifolds like those used in the randall - sundrum brane world and non - compact kaluza - klein models. our analysis is based on a covariant foliation of the manifold using 3 + 1 dimensional spacetime slices orthogonal to the extra dimension, and is hence similar to the adm 3 + 1 split in ordinary general relativity. we derive gauge invariant equations of motion for freely - falling test particles in the 5d and 4d affine parameterizations and contrast these results with previous work concerning the so - called ` ` fifth force ' '. motivated by the conjectured localization of matter fields on a 3 - brane, we derive the form of the classical non - gravitational force required to confine particles to a 4d hypersurface and show that the resulting trajectories are geometrically identical to the spacetime geodesics of einstein ' s theory. we then discuss the issue of determining the 5d dynamics of a torque - free spinning body in the point - dipole approximation, and then perform a covariant ( 3 + 1 ) + 1 decomposition of the relevant formulae ( i. e. the 5d fermi - walker transport equation ) for the cases of freely - falling and hypersurface - confined point gyroscopes. in both cases, the 4d spin tensor is seen to be subject to an anomalous torque. we solve the spin equations for a gyroscope confined to a single spacetime section in a simple 5d cosmological model and observe a cosmological variation of the magnitude and orientation of the 4d spin.
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arxiv:gr-qc/0204032
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schema linking is a critical bottleneck in achieving human - level performance in text - to - sql tasks, particularly in real - world large - scale multi - database scenarios. addressing schema linking faces two major challenges : ( 1 ) database retrieval : selecting the correct database from a large schema pool in multi - database settings, while filtering out irrelevant ones. ( 2 ) schema item grounding : accurately identifying the relevant tables and columns from within a large and redundant schema for sql generation. to address this, we introduce linkalign, a novel framework that can effectively adapt existing baselines to real - world environments by systematically addressing schema linking. our framework comprises three key steps : multi - round semantic enhanced retrieval and irrelevant information isolation for challenge 1, and schema extraction enhancement for challenge 2. we evaluate our method performance of schema linking on the spider and bird benchmarks, and the ability to adapt existing text - to - sql models to real - world environments on the spider 2. 0 - lite benchmark. experiments show that linkalign outperforms existing baselines in multi - database settings, demonstrating its effectiveness and robustness. on the other hand, our method ranks highest among models excluding those using long chain - of - thought reasoning llms. this work bridges the gap between current research and real - world scenarios, providing a practical solution for robust and scalable schema linking. the codes are available at https : / / github. com / satissss / linkalign.
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arxiv:2503.18596
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we study the regional controllability problem for delayed fractional control systems through the use of the standard caputo derivative. first, we recall several fundamental results and introduce the family of fractional - order systems under consideration. afterwards, we formulate the notion of regional controllability for fractional systems with control delays and give some of their important properties. our main method consists in defining an attainable set, which allow us to prove exact and weak controllability. moreover, main results include not only those of controllability but also a powerful hilbert uniqueness method that allow us to solve the minimum energy optimal control control problem. precisely, an explicit control is obtained that drives the system from an initial given state to a desired regional state with minimum energy. examples are given to illustrate the obtained theoretical results.
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arxiv:2212.09466
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the presence of correlations between particles significantly separated in pseudorapidity in proton - proton and proton - nucleus collisions has raised questions about whether collective effects are observed in small collision systems as well as in heavy - ion collisions. the quantification of these long - range correlations by $ v _ n $ coefficients is of particular interest. a selection of the latest $ v _ n $ measurements is presented, including results from the recent $ d $ + au beam energy scan at rhic where a significant non - zero $ v _ 2 $ is measured down to low center - of - mass energies ( $ \ sqrt { s _ { \ rm { nn } } } $ = 39 gev ). results from a collision system scan - comprising $ p $ + au, $ d $ + au, and $ ^ 3 $ he + au collisions - are also shown to address the role of the initial nuclear geometry in the final state anisotropy. finally, the challenge of measuring multi - particle cumulants, particularly $ c _ 2 \ { 4 \ } $, in $ p $ + $ p $ collisions is discussed, and new methods for reducing the effects of non - flow are shown to produce a more robust measurement of $ v _ 2 \ { 4 \ } $ in $ p $ + $ p $ collisions.
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arxiv:1901.00710
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monte carlo techniques based on indivisible energy packets are described for computing light curves and spectra for 3 - d supernovae. the radiative transfer is time - dependent and includes all effects of o ( v / c ). monte carlo quantization is achieved by discretizing the initial distribution of 56ni into radioactive pellets. each pellet decays with the emission of a single energy packet comprising gamma - ray photons representing one line from either the 56ni or the 56co decay spectrum. subsequently, these energy packets propagate through the homologously - expanding ejecta with appropriate changes in the nature of their contained energy as they undergo compton scatterings and pure absorptions. the 3 - d code is tested by applying it to a spherically - symmetric sn in which the transfer of optical radiation is treated with a grey absorption coefficient. this 1 - d problem is separately solved using castor ' s co - moving frame moment equations. satisfactory agreement is obtained. the monte carlo code is a platform onto which more advanced treatments of the interactions of matter and radiation can be added. some of these have already been developed and tested in previous papers and are summarized here.
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arxiv:astro-ph/0409249
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for many applications in the field of computer assisted surgery, such as providing the position of a tumor, specifying the most probable tool required next by the surgeon or determining the remaining duration of surgery, methods for surgical workflow analysis are a prerequisite. often machine learning based approaches serve as basis for surgical workflow analysis. in general machine learning algorithms, such as convolutional neural networks ( cnn ), require large amounts of labeled data. while data is often available in abundance, many tasks in surgical workflow analysis need data annotated by domain experts, making it difficult to obtain a sufficient amount of annotations. the aim of using active learning to train a machine learning model is to reduce the annotation effort. active learning methods determine which unlabeled data points would provide the most information according to some metric, such as prediction uncertainty. experts will then be asked to only annotate these data points. the model is then retrained with the new data and used to select further data for annotation. recently, active learning has been applied to cnn by means of deep bayesian networks ( dbn ). these networks make it possible to assign uncertainties to predictions. in this paper, we present a dbn - based active learning approach adapted for image - based surgical workflow analysis task. furthermore, by using a recurrent architecture, we extend this network to video - based surgical workflow analysis. we evaluate these approaches on the cholec80 dataset by performing instrument presence detection and surgical phase segmentation. here we are able to show that using a dbn - based active learning approach for selecting what data points to annotate next outperforms a baseline based on randomly selecting data points.
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arxiv:1811.03382
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mixing length theory is the predominant treatment of convection in stellar models today. usually described by a single free parameter, alpha, the common practice is to calibrate it using the properties of the sun, and apply it to all other stellar models as well. asteroseismic data from kepler and corot provide precise properties of other stars which can be used to determine alpha as well, and a recent study of stars in the kepler field of view found alpha to vary with metallicity. interpreting alpha obtained from calibrated stellar models, however, is complicated by the fact that the value for alpha depends on the surface boundary condition of the stellar model, or t - tau relation. calibrated models that use typical t - tau relations, which are static and insensitive to chemical composition, do not include the complete effect of metallicity on alpha. we use 3d radiation - hydrodynamic simulations to extract metallicity - dependent t - tau relations and use them in calibrated stellar models. we find the previously reported alpha - metallicity trend to be robust, and not significantly affected by the surface boundary condition of the stellar models.
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arxiv:1402.1182
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this paper calculates the elastic form factors for nucleons based on generalized parton distributions using an extended new ansatz introduced in http : / / dx. doi. org / 10. 1103 / physrevc. 105. 025202 ( phys. rev. c 105, no. 2, 025202 ( 2022 ) ). different parton distribution functions ( pdfs ) are considered, and modifications are made to the free parameters of the new ansatz. the obtained results are systematically compared among the combinations of different pdfs and ansatzes for high ranges of momentum transfer, with $ - t < 35 gev ^ { - 2 } $. the minimum suitable parameters are used to parametrize the model. after obtaining the form factors, we proceed to compute the electric radius and the transversely unpolarized densities for the nucleon. in addition, we derive the parton distribution functions ( pdfs ) that depend on the impact parameter. finally, we analyze the results by comparing them with the findings from other research and experimental data.
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arxiv:2305.02438
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by constructing a new coupling, the log - harnack inequality is established for the functional solution of a delay stochastic differential equation with multiplicative noise. as applications, the strong feller property and heat kernel estimates w. r. t. quasi - invariant probability measures are derived for the associated transition semigroup of the solution. the dimension - free harnack inequality in the sense of \ cite { w97 } is also investigated.
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arxiv:1012.5688
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the petty projection inequality for sets of finite perimeter is proved. our approach is based on steiner symmetrization. neither the affine sobolev inequality nor the functional minkowski problem is used in our proof. moreover, for sets of finite perimeter, we prove the petty projection inequality with respect to steiner symmetrization.
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arxiv:2102.07103
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in this paper we study the dynamics of an ensemble of nitrogen - vacancy centers in diamond when its photoluminescence is detected by means of a widefield imaging system. we develop a seven - level model and use it to simulate the widefield detection of nitrogen - vacancy centers rabi oscillations. the simulation results are compared with experimental measurements showing a good agreement. in particular, we use the model to explain the asymmetric shape of the detected rabi oscillations due to an incomplete repolarization of the nitrogen - vacancy center during the pulse sequence implemented for the detection of rabi oscillations.
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arxiv:2309.06203
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we initiate the study of the coefficients of the distinct monomials in the expansion of the multivariate polynomials $ x _ 1 ( x _ 1 + x _ 2 ) \ cdots ( x _ 1 + x _ 2 + \ cdots + x _ n ), n \ in \ n $. in particular we obtain several results regarding their maximal coefficients.
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arxiv:2111.07331
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the semantic web is becoming more and more a reality, as the required technologies have reached an appropriate level of maturity. however, at this stage, it is important to provide tools facilitating the use and deployment of these technologies by end - users. in this paper, we describe edhibou, an automatically generated, ontology - based graphical user interface that integrates in a semantic portal. the particularity of edhibou is that it makes use of owl reasoning capabilities to provide intelligent features, such as decision support, upon the underlying ontology. we present an application of edhibou to medical decision support based on a formalization of clinical guidelines in owl and show how it can be customized thanks to an ontology of graphical components.
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arxiv:0811.0310
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and standardization. new conventions and symbols were created by engineers ; the use of which became standardized throughout industries, so that any person who could read a technical drawing could know the specifications of a component or structure. the standardization process helped engineer practices to become standardized, making it easier for engineers, manufacturers, and builders to work together. in the 20th century, technical drawing underwent yet another transformation with the introduction of drafting tools such as the t - square, compasses, and protractors. these tools helped drafters achieve the high degree of precision necessary for increasingly complex projects, such as skyscrapers, airplanes, and automobiles. the establishment of standards such as the american national standards institute ( ansi ) and international organization for standardization ( iso ) further formalized technical drawing conventions, ensuring consistency in engineering practices around the world. today, technical drawing has largely transitioned from manual drafting to computer - aided design ( cad ). cad software has revolutionized the way technical drawings are created, allowing for faster, more precise, and easily modifiable drawings. engineers can now visualize designs in three dimensions, simulate performance, and make adjustments before any physical prototype is built. this digital transformation has not only increased efficiency but also broadened the possibilities for innovation, enabling engineers to tackle challenges that were previously unimaginable. however, despite the advent of digital tools, the fundamental principles of technical drawing remain rooted in its history. precision, clarity, and the ability to convey complex information visually are still at the core of technical drawing. the conventions established over centuries — from orthographic projection to the use of scale and dimension lines — continue to be essential in modern engineering and architectural practice. the evolution of technical drawing is a testament to human ingenuity, demonstrating how the ability to convey complex ideas visually has been pivotal in the advancement of civilization. = = standardization and disambiguation = = engineering drawings specify the requirements of a component or assembly which can be complicated. standards provide rules for their specification and interpretation. standardization also aids internationalization, because people from different countries who speak different languages can read the same engineering drawing, and interpret it the same way. one major set of engineering drawing standards is asme y14. 5 and y14. 5m ( most recently revised in 2018 ). these apply widely in the united states, although iso 8015 ( geometrical product specifications ( gps ) — fundamentals — concepts, principles and rules ) is now also important. in 2018, asme aed - 1 was created to develop advanced practices unique to aerospace and
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https://en.wikipedia.org/wiki/Engineering_drawing
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over the past decades, enormous efforts have been made to improve the performance of linear or nonlinear mixing models for hyperspectral unmixing, yet their ability to simultaneously generalize various spectral variabilities and extract physically meaningful endmembers still remains limited due to the poor ability in data fitting and reconstruction and the sensitivity to various spectral variabilities. inspired by the powerful learning ability of deep learning, we attempt to develop a general deep learning approach for hyperspectral unmixing, by fully considering the properties of endmembers extracted from the hyperspectral imagery, called endmember - guided unmixing network ( egu - net ). beyond the alone autoencoder - like architecture, egu - net is a two - stream siamese deep network, which learns an additional network from the pure or nearly - pure endmembers to correct the weights of another unmixing network by sharing network parameters and adding spectrally meaningful constraints ( e. g., non - negativity and sum - to - one ) towards a more accurate and interpretable unmixing solution. furthermore, the resulting general framework is not only limited to pixel - wise spectral unmixing but also applicable to spatial information modeling with convolutional operators for spatial - spectral unmixing. experimental results conducted on three different datasets with the ground - truth of abundance maps corresponding to each material demonstrate the effectiveness and superiority of the egu - net over state - of - the - art unmixing algorithms. the codes will be available from the website : https : / / github. com / danfenghong / ieee _ tnnls _ egu - net.
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arxiv:2105.10194
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measurement of the gas velocity distribution in galaxy clusters provides insight into the physics of mergers, through which large scale structures form in the universe. velocity estimates within the intracluster medium ( icm ) can be obtained via the sunyaev - zel ' dovich ( sz ) effect, but its observation is challenging both in term of sensitivity requirement and control of systematic effects, including the removal of contaminants. in this paper we report resolved observations, at 150 and 260 ghz, of the sz effect toward the triple merger macs j0717. 5 + 3745 ( z = 0. 55 ), using data obtained with the nika camera at the iram 30m telescope. assuming that the sz signal is the sum of a thermal ( tsz ) and a kinetic ( ksz ) component and by combining the two nika bands, we extract for the first time a resolved map of the ksz signal in a cluster. the ksz signal is dominated by a dipolar structure that peaks at - 5. 1 and + 3. 4 sigma, corresponding to two subclusters moving respectively away and toward us and coincident with the cold dense x - ray core and a hot region undergoing a major merging event. we model the gas electron density and line - of - sight velocity of macs j0717. 5 + 3745 as four subclusters. combining nika data with x - ray observations from xmm - newton and chandra, we fit this model to constrain the gas line - of - sight velocity of each component, and we also derive, for the first time, a velocity map from ksz data ( i. e. that is model - dependent ). our results are consistent with previous constraints on the merger velocities, and thanks to the high angular resolution of our data, we are able to resolve the structure of the gas velocity. finally, we investigate possible contamination and systematic effects with a special care given to radio and submillimeter galaxies. among the sources that we detect with nika, we find one which is likely to be a high redshift lensed submillimeter galaxy.
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arxiv:1606.07721
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high - sensitive measurement of radio - frequency ( rf ) electric field is available via the electromagnetically induced transparency ( eit ) effect of rydberg atom at room - temperature, which has been developed to be a promising atomic rf receiver. in this letter, we investigate the credibility of the digital communication via this quantum - based antenna over the entire continuously tunable rf - carrier. our experiment shows that digital communication at a rate of 500 kbps performs reliably within a tunable bandwidth of 200 mhz at carrier 10. 22 ghz and a bit error rate ( ber ) appears out of this range, for example, the ber runs up to 15 % at rf - detuning $ \ pm150 $ mhz. in the measurement, the time - variant rf field is retrieved by detecting the density of the probe laser at the center frequency of rf - induced symmetric or asymmetric autler - townes splitting in eit. prior to the digital test, we have studied the rf - receiving quality versus the physical ambiance and found that a choice of linear gain response to the rf - amplitude can suppress the signal distortion and the modulating signal is able to be decoded as fast as up to 500 khz in the tunable bandwidth. our checkout consolidates the physical foundation for a reliable communication and spectrum sensing over the broadband rf - carrier.
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arxiv:1808.10839
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the article suggests a new approach what is called a consistency method for the inversion of the spherical radon transform in 2d with detectors on a line. it is known that there is not an exact inversion formula in 2d. by means of the method was proved that the reconstruction has a local description and found a new iteration formula which give an practical algorithm to recover an unknown function supported completely on one side of a line $ l $ from its spherical means over circles centered on the line $ l $. such an inversion is required in problems of thermo - and photo - acoustic tomography.
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arxiv:1705.10690
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using a numerical decimation method, we compute the localisation length $ \ lambda _ { 2 } $ for two onsite interacting particles ( tip ) in a one - dimensional random potential. we show that an interaction $ u > 0 $ does lead to $ \ lambda _ 2 ( u ) > \ lambda _ 2 ( 0 ) $ for not too large $ u $ and test the validity of various proposed fit functions for $ \ lambda _ 2 ( u ) $. finite - size scaling allows us to obtain infinite sample size estimates $ \ xi _ { 2 } ( u ) $ and we find that $ \ xi _ { 2 } ( u ) \ sim \ xi _ 2 ( 0 ) ^ { \ alpha ( u ) } $ with $ \ alpha ( u ) $ varying between $ \ alpha ( 0 ) \ approx 1 $ and $ \ alpha ( 1 ) \ approx 1. 5 $. we observe that all $ \ xi _ 2 ( u ) $ data can be made to coalesce onto a single scaling curve. we also present results for the problem of tip in two different random potentials corresponding to interacting electron - hole pairs.
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arxiv:cond-mat/9809369
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about a dozen hot white dwarfs with effective temperatures teff = 65, 000 - 120, 000 k exhibit unusual absorption features in their optical spectra. these objects were tentatively identified as rydberg lines of ultra - high excited metals in ionization stages v - x, indicating line formation in a dense environment with temperatures near one million kelvin. since some features show blueward extensions, it was argued that they stem from a superionized wind. a unique assignment of the lines to particular elements is not possible, although they probably stem from c, n, o, and ne. to further investigate this phenomenon, we analyzed the ultraviolet spectra available from only three stars of this group ; that is, two helium - rich white dwarfs, he 0504 - 2408 and hs 0713 + 3958 with spectral type do, and a hydrogen - rich white dwarf, hs 2115 + 1148 with spectral type dao. we identified light metals ( c, n, o, si, p, and s ) with generally subsolar abundances and heavy elements from the iron group ( cr, mn, fe, co, ni ) with solar or oversolar abundance. the abundance patterns are not unusual for hot wds and can be interpreted as the result of gravitational settling and radiative levitation of elements. as to the origin of the ultra - high ionized metals lines, we discuss the possible presence of a multicomponent radiatively driven wind that is frictionally heated.
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arxiv:1711.04138
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the recent discovery of the superconductivity in the doped infinite layer nickelates $ r $ nio $ _ 2 $ ( $ r $ = la, pr, nd ) is of great interest since the nickelates are isostructural to doped ( ca, sr ) cuo $ _ 2 $ having superconducting transition temperature ( $ t _ { \ rm c } $ ) of about 110 k. verifying the commonalities and differences between these oxides will certainly give a new insight into the mechanism of high $ t _ { \ rm c } $ superconductivity in correlated electron systems. in this paper, we review experimental and theoretical works on this new superconductor and discuss the future perspectives for the " nickel age " of superconductivity.
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arxiv:2107.12923
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we study continuous - time markov chains on the non - negative integers under mild regularity conditions ( in particular, the set of jump vectors is finite and both forward and backward jumps are possible ). based on the so - called flux balance equation, we derive an iterative formula for calculating stationary measures. specifically, a stationary measure $ \ pi ( x ) $ evaluated at $ x \ in \ n _ 0 $ is represented as a linear combination of a few generating terms, similarly to the characterization of a stationary measure of a birth - death process, where there is only one generating term, $ \ pi ( 0 ) $. the coefficients of the linear combination are recursively determined in terms of the transition rates of the markov chain. for the class of markov chains we consider, there is always at least one stationary measure ( up to a scaling constant ). we give various results pertaining to uniqueness and non - uniqueness of stationary measures, and show that the dimension of the linear space of signed invariant measures is at most the number of generating terms. a minimization problem is constructed in order to compute stationary measures numerically. moreover, a heuristic linear approximation scheme is suggested for the same purpose by first approximating the generating terms. the correctness of the linear approximation scheme is justified in some special cases. furthermore, a decomposition of the state space into different types of states ( open and closed irreducible classes, and trapping, escaping and neutral states ) is presented. applications to stochastic reaction networks are well illustrated.
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arxiv:2312.06186
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we define a floer - homology invariant for links in $ s ^ 3 $, and study its properties.
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arxiv:math/0512286
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the met office space weather operations centre produces 24 / 7 / 365 space weather guidance, alerts, and forecasts to a wide range of government and commercial end users across the united kingdom. solar flare forecasts are one of its products, which are issued multiple times a day in two forms ; forecasts for each active region on the solar disk over the next 24 hours, and full - disk forecasts for the next four days. here the forecasting process is described in detail, as well as first verification of archived forecasts using methods commonly used in operational weather prediction. real - time verification available for operational flare forecasting use is also described. the influence of human forecasters is highlighted, with human - edited forecasts outperforming original model results, and forecasting skill decreasing over longer forecast lead times.
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arxiv:1703.06754
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incentives are more likely to elicit desired outcomes when they are designed based on accurate models of agents ' strategic behavior. a growing literature, however, suggests that people do not quite behave like standard economic agents in a variety of environments, both online and offline. what consequences might such differences have for the optimal design of mechanisms in these environments? in this paper, we explore this question in the context of optimal contest design for simple agents - - - agents who strategically reason about whether or not to participate in a system, but not about the input they provide to it. specifically, consider a contest where $ n $ potential contestants with types $ ( q _ i, c _ i ) $ each choose between participating and producing a submission of quality $ q _ i $ at cost $ c _ i $, versus not participating at all, to maximize their utilities. how should a principal distribute a total prize $ v $ amongst the $ n $ ranks to maximize some increasing function of the qualities of elicited submissions in a contest with such simple agents? we first solve the optimal contest design problem for settings with homogenous participation costs $ c _ i = c $. here, the optimal contest is always a simple contest, awarding equal prizes to the top $ j ^ * $ contestants for a suitable choice of $ j ^ * $. ( in comparable models with strategic effort choices, the optimal contest is either a winner - take - all contest or awards possibly unequal prizes, depending on the curvature of agents ' effort cost functions. ) we next address the general case with heterogeneous costs where agents ' types are inherently two - dimensional, significantly complicating equilibrium analysis. our main result here is that the winner - take - all contest is a 3 - approximation of the optimal contest when the principal ' s objective is to maximize the quality of the best elicited contribution.
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arxiv:1406.1790
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we present a comprehensive structural study on perovskite - type 6h - ba3cusb2o9, which exhibits a spin - orbital short - range ordering on a honeycomb - based lattice. by combining synchrotron x - ray diffraction, electron spin resonance, ultrasound measurement and raman spectroscopy, we found that the static jahn - teller distortion is absent down to the lowest temperature in the present material, indicating orbital ordering is strongly suppressed. we discuss such an unusual state is realized with the help of spin degree of freedom, leading to a spin - orbital entangled liquid state.
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arxiv:1403.4779
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finite - precision floating point arithmetic unavoidably introduces rounding errors which are traditionally bounded using a worst - case analysis. however, worst - case analysis might be overly conservative because worst - case errors can be extremely rare events in practice. here we develop a probabilistic model of rounding errors with which it becomes possible to estimate the likelihood that the rounding error of an algorithm lies within a given interval. given an input distribution, we show how to compute the distribution of rounding errors. we do this exactly for low precision arithmetic, for high precision arithmetic we derive a simple approximation. the model is then entirely compositional : given a numerical program written in a simple imperative programming language we can recursively compute the distribution of rounding errors at each step of the computation and propagate it through each program instruction. this is done by applying a formalism originally developed by kozen to formalize the semantics of probabilistic programs. we then discuss an implementation of the model and use it to perform probabilistic range analyses on some benchmarks.
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arxiv:1912.00867
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in a recent paper dewolfe et al. have shown how to use the self - intersection number of junctions to constrain the bps spectrum of n = 2, d = 4 theories with ade flavor symmetry arising on a single d3 - brane probe in a 7 - brane background. motivated by the existence of more general n = 2, d = 4 theories arising on the worldvolume of multiple d3 - brane probes we show how to compute the self - intersection number of junctions in the presence of 7 - branes and multiple d3 - branes.
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arxiv:hep-th/9807117
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antiferromagnetic fluctuations in two dimensions cause a decrease in spectral weight at so - called hot spots associated with the pseudogap in electron - doped cuprates. in the 2d hubbard model, these hot spots occur when the vilk criterion is satisfied, namely when the spin correlation length exceeds the thermal de broglie wavelength. using the two - particle self - consistent approach, here we show that this criterion may be violated near the antiferromagnetic quantum critical point when sufficient disorder is added to the model. static disorder decreases inelastic scattering, in contradiction with matthiessen ' s rule, leading to a shift in the position of the quantum critical point and a modification of the conditions for the appearance of hot spots. this opens the road to a study of the interplay between disorder, antiferromagnetic fluctuations and superconductivity in electron - doped cuprates.
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arxiv:2205.00066
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we study a smoluchowski equation describing a simple mean - field model of particles moving in $ d $ dimensions and aggregating with conservation of ` mass ' $ s = r ^ d $ ( $ r $ is the particle radius ). in the scaling regime the scaled mass distribution $ p ( s ) \ sim s ^ { - \ tau } $, and $ \ tau $ can be computed by perturbative and non perturbative expansions. a possible application to two - dimensional decaying turbulence is briefly discussed.
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arxiv:cond-mat/9607081
|
a monte carlo simulation is performed in a cubic lattice of interacting identical stoner - woldfarth nanoparticles. the model system is a randomly - anisotropic heisenberg spin system with a small anisotropy - to - exchange ratio d / j = 3. 5. the dc susceptibility, chi ( dc ) ( t ), shows a curie - weiss - like transition at a temperature t - c / j approximate to 1. 5, followed by a low - temperature glassy behavior manifested by cusps in both the zero - field - cooled and the field - cooled curves. the ac susceptibility, chi ( ac ) ( t, omega ), at various frequencies, w, shows that with decreasing temperature, a non - arrhenius dispersive peak occurs at t - b ( omega ), succeeded by another dispersionless peak at t - g / j approximate to 1. 20 in the in - phase part, chi ' ( t, omega ), of chi ( t, omega ) while the out - of - phase part, chi ' ' ( t, omega ), shows only one peak. a dynamic scaling analysis shows that the system exhibits a critical slowing - down at t - g with a quite small exponent zv approximate to 1. 65. however, no universal collapse is seen for the fully - scaled data of chi ' ' ( t, omega ). these observed behaviors are interpreted under the droplet - like hypothesis that the formation and development of exchange - induced correlated clusters drive ensembles of nanoparticles undergoing a transition from a paramagnetic order to a short - range order ( sro ) at t - c, followed by a transition at t - g to the magnetic state in which a magnetic glassy order and a magnetic quasi - long - range order ( qlro ) coexist. in addition, our simulation shows that the onset of the latter transition, which is peculiarly manifested by the dispersionless peak, occurs only for those ensembles possessing the anisotropy strength in the region 1. 0 < = d / j < = 5. 0.....
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arxiv:0903.1571
|
an existing approach for dealing with massive data sets is to stream over the input in few passes and perform computations with sublinear resources. this method does not work for truly massive data where even making a single pass over the data with a processor is prohibitive. successful log processing systems in practice such as google ' s mapreduce and apache ' s hadoop use multiple machines. they efficiently perform a certain class of highly distributable computations defined by local computations that can be applied in any order to the input. motivated by the success of these systems, we introduce a simple algorithmic model for massive, unordered, distributed ( mud ) computation. we initiate the study of understanding its computational complexity. our main result is a positive one : any unordered function that can be computed by a streaming algorithm can also be computed with a mud algorithm, with comparable space and communication complexity. we extend this result to some useful classes of approximate and randomized streaming algorithms. we also give negative results, using communication complexity arguments to prove that extensions to private randomness, promise problems and indeterminate functions are impossible. we believe that the line of research we introduce in this paper has the potential for tremendous impact. the distributed systems that motivate our work successfully process data at an unprecedented scale, distributed over hundreds or even thousands of machines, and perform hundreds of such analyses each day. the mud model ( and its generalizations ) inspire a set of complexity - theoretic questions that lie at their heart.
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arxiv:cs/0611108
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