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we address a problem of identifying a given pure state with one of two reference pure states, when no classical knowledge on the reference states is given, but a certain number of copies of them are available. we assume the input state is guaranteed to be either one of the two reference states. this problem, which we call quantum pure state identification, is a natural generalization of the standard state discrimination problem. the two reference states are assumed to be independently distributed in a unitary invariant way in the whole state space. we give a complete solution for the averaged maximal success probability of this problem for an arbitrary number of copies of the reference states in general dimension. it is explicitly shown that the obtained mean identification probability approaches the mean discrimination probability as the number of the reference copies goes to infinity. | arxiv:quant-ph/0507237 |
speculative fiction is an umbrella genre of fiction that encompasses all the subgenres that depart from realism, or strictly imitating everyday reality, instead presenting fantastical, supernatural, futuristic, or other imaginative realms. this catch - all genre includes, but is not limited to : fantasy, science fiction, science fantasy, superhero, paranormal, supernatural, horror, alternate history, magical realism, slipstream, weird fiction, utopia and dystopia, apocalyptic and post - apocalyptic fiction. in other words, the genre speculates on individuals, events, or places beyond the ordinary real world. the term speculative fiction has been used for works of literature, film, television, drama, video games, radio, and hybrid media. = = speculative versus realistic fiction = = the umbrella genre of speculative fiction is characterized by a lesser degree of adherence to plausible depictions of individuals, events, or places, while the umbrella genre of realistic fiction ( partly crossing over with literary realism ) is characterized by a greater degree of adherence to such depictions. for instance, speculative fiction may depict an entirely imaginary universe or one in which the laws of nature do not strictly apply ( often the subgenre of fantasy ). alternatively, the genre depicts actual historical moments, except that they have concluded in an entirely imaginary way or been followed by major imaginary events ( i. e., the subgenre of alternative history ). as another alternative, the genre depicts impossible technology or technology that defies current scientific understanding or capabilities ( i. e., the subgenre of science fiction ). by contrast, realistic fiction involves a story whose basic setting is real and whose events could plausibly occur in the real world. one realistic fiction subgenre is historical fiction, which is centred around actual major events and time periods of the past. the attempt to make stories seem faithful to reality or to more objectively describe details — and also the 19th - century artistic movement that vigorously promoted this approach — is called " literary realism " ; this includes both fiction and non - fiction works. = = = distinguishing science fiction from other speculative fiction = = = " speculative fiction " is sometimes abbreviated as spec - fic, spec fic, specfic, s - f, sf, or sf. the last three abbreviations, however, are ambiguous since they have long been used to refer to science fiction ( which lies within this general area of literature ). the genre is sometimes known as the fantastic or fantastika ; the latter term is attributed to science fiction scholar john clute, | https://en.wikipedia.org/wiki/Speculative_fiction |
recent arpes measurements on the electron - doped cuprate nd _ { 2 - x } ce _ xcuo _ 4 can be interpreted in a mean field model of uniform doping of an antiferromagnet, with the mott gap closing near optimal doping. mode coupling calculations confirm the mean field results, while clarifying the relation between the mott gap and short - range magnetic order. the same calculations find that hole doped cuprates should follow a strikingly different doping dependence, involving instability toward spiral phases or stripes. nevertheless, the magnetic order ( now associated with stripes ) again collapses near optimal doping. | arxiv:cond-mat/0308361 |
sufficiently large seeds for generating the observed ( inter ) galactic magnetic fields emerge naturally in string cosmology from the amplification of electromagnetic vacuum fluctuations due to a dynamical dilaton background. the success of the mechanism depends crucially on two features of the so - called pre - big - bang scenario, an early epoch of dilaton - driven inflation at very small coupling, and a sufficiently long intermediate stringy era preceding the standard radiation - dominated evolution. | arxiv:hep-th/9504083 |
knowing when to answer or refuse is crucial for safe and reliable decision - making language agents. although prior work has introduced refusal strategies to boost lms ' reliability, how these models adapt their decisions to different risk levels remains underexplored. we formalize the task of risk - aware decision - making, expose critical weaknesses in existing lms, and propose skill - decomposition solutions to mitigate them. our findings show that even cutting - edge lms - - both regular and reasoning models - - still require explicit prompt chaining to handle the task effectively, revealing the challenges that must be overcome to achieve truly autonomous decision - making agents. | arxiv:2503.01332 |
motivated by cosmological considerations, and by the atmospheric and solar neutrino flux deficits, we consider the scenario in which the three standard model neutrinos are endowed with a nearly equal majorana mass in the ev range. combined constraints coming from ( 1 ) direct search for electron neutrino mass, ( 2 ) absence of neutrinoless double beta decay, and ( 3 ) unsuppressed electron neutrino flux in present reactor experiments, imply a quite well specified pattern of neutrino masses and mixing angles. we discuss the experimental tests of the model and comment on the features of this scenario. | arxiv:hep-ph/9708483 |
in this paper, we study groups of automorphisms of algebraic systems over a set of $ p $ - adic integers with different sets of arithmetic and coordinate - wise logical operations and congruence relations modulo $ p ^ k, $ $ k \ ge 1. $ the main result of this paper is the description of groups of automorphisms of $ p $ - adic integers with one or two arithmetic or coordinate - wise logical operations on $ p $ - adic integers. to describe groups of automorphisms, we use the apparatus of the $ p $ - adic analysis and $ p $ - adic dynamical systems. the motive for the study of groups of automorphism of algebraic systems over $ p $ - adic integers is the question of the existence of a fully homomorphic encryption in a given family of ciphers. the relationship between these problems is based on the possibility of constructing a " continuous " $ p $ - adic model for some families of ciphers ( in this context, these ciphers can be considered as " discrete " systems ). as a consequence, we can apply the " continuous " methods of $ p $ - adic analysis to solve the " discrete " problem of the existence of fully homomorphic ciphers. | arxiv:1805.12537 |
vehicle - to - vehicle communication is a fundamental requirement in cooperative vehicular systems to achieve high performance while keeping high safety standards. vehicles periodically exchange critical information with nearby vehicles to determine their maneuvers according to the information quality and established strategies. however, wireless communication is prone to failures. thus, participants can be unaware that other participants have not received the information on time resulting in conflicting trajectories that may not be safe. we present a deterministic solution that allows all participants to use a default strategy when other participants have not received on time the complete information. we base our solution on a timed distributed protocol that adapts its output according to the effect of message omission failures so that the disagreement period occurs for no longer than a constant time ( of the order of milliseconds ) that only depends on the message delay. we formally show the correctness and perform experiments to corroborate its efficiency. we explain how the proposed solution can be used on vehicular platooning to attain high performance and still guarantee high safety standards despite communication failures. we believe that this work can facilitate the implementation of cooperative driving systems that have to deal with inherent ( communication ) uncertainties. | arxiv:1408.7035 |
we consider a broad class of nonlinear integro - differential equations with a kernel whose differentiability order is described by a general function $ \ phi $. this class includes not only the fractional $ p $ - laplace equations, but also borderline cases when the fractional order approaches $ 1 $. under mild assumptions on $ \ phi $, we establish sharp sobolev - poincar \ ' e type inequalities for the associated sobolev spaces, which are connected to a question raised by brezis ( russian math. surveys 57 : 693 - - 708, 2002 ). using these inequalities, we prove h \ " older regularity and harnack inequalities for weak solutions to such nonlocal equations. all the estimates in our results remain stable as the associated nonlocal energy functional approaches its local counterpart. | arxiv:2503.09307 |
we present the results of an isophotal shape analysis of three samples of galaxies in the coma cluster. quantitative morphology, together with structural and photometric parameters, is given for each galaxy. special emphasis has been placed on the detailed classification of early - type galaxies. the three samples are : i ) a sample of 97 early - type galaxies brighter than m $ _ b $ = 17. 00 falling within one degree from the center of the coma cluster ; these galaxies were observed with ccd cameras, mostly in good to excellent resolution conditions ; ii ) a magnitude complete sample of 107 galaxies of all morphological types down to m $ _ b $ = 17. 00 falling in a circular region of 50 arcmin diameter, slightly offcentered to the north - west of the cluster center ; the images for this and the next sample come from digitized photographic plates ; iii ) a complete comparison sample of 26 galaxies of all morphological types down to m $ _ r $ = 16. 05 ( or m $ _ b $ $ \ simeq $ 17. 5 ), also in a region of 50 arcmin diameter, but centered 2. 6 degrees west of the cluster center. the reliability of our morphological classifications and structural parameters of galaxies, down to the adopted magnitude limits, is assessed by comparing the results on those galaxies for which we had images taken with different instrumentation and / or seeing conditions, and by comparing our results with similar data from other observers. | arxiv:astro-ph/9510095 |
we first develop a general theory of johnson filtrations and johnson homomorphisms for a group $ g $ acting on another group $ k $ equipped with a filtration indexed by a " good " ordered commutative monoid. then, specializing it to the case where the monoid is the additive monoid $ \ mathbb { n } ^ 2 $ of pairs on nonnegative integers, we obtain a theory of double johnson filtrations and homomorphisms. we apply this theory to the mapping class group $ \ mathcal { m } $ of a surface $ \ sigma _ { g, 1 } $ with one boundary component, equipped with the normal subgroups $ \ bar { x } $, $ \ bar { y } $ of $ \ pi _ 1 ( \ sigma _ { g, 1 } ) $ associated to a standard heegaard splitting of the $ 3 $ - sphere. we also consider the case where the group $ g $ is the automorphism group of a free group. | arxiv:2009.07484 |
photonic structures in diamond are key to most of its application in quantum technology. here, we demonstrate tapered nano - waveguides structured directly onto the diamond substrate hosting shallow - implanted nitrogen vacancy ( nv ) centers. by optimization based on simulations and precise experimental control of the geometry of these pillar - shaped nano - waveguides, we achieve a net photon flux up to ~ $ 1. 7 \ cdot 10 ^ 6 / s $. this presents the brightest monolithic bulk diamond structure based on single nv centers so far. we observe no impact on excited state lifetime and electronic spin dephasing time ( $ t _ 2 $ ) due to the nanofabrication process. possessing such high brightness with low background in addition to preserved spin quality, this geometry can improve the current nanomagnetometry sensitivity ~ 5 times. in addition, it facilitates a wide range of diamond defects - based magnetometry applications. as a demonstration, we measure the temperature dependency of $ t _ 1 $ relaxation time of a single shallow nv center electronic spin. we observe the two - phonon raman process to be negligible in comparison to the dominant two - phonon orbach process. | arxiv:1409.0027 |
the most general amplitude for the radiative pion decay pi - > e nu gamma including terms beyond v - a theory is considered. the experimental constraints on the decay amplitude components are discussed. a model independent presentation of the results of high statistics and high resolution experiments is suggested. | arxiv:hep-ph/0307166 |
we introduce the following submodular generalization of the shortest cycle problem. for a nonnegative monotone submodular cost function $ f $ defined on the edges ( or the vertices ) of an undirected graph $ g $, we seek for a cycle $ c $ in $ g $ of minimum cost $ \ textsf { opt } = f ( c ) $. we give an algorithm that given an $ n $ - vertex graph $ g $, parameter $ \ varepsilon > 0 $, and the function $ f $ represented by an oracle, in time $ n ^ { \ mathcal { o } ( \ log 1 / \ varepsilon ) } $ finds a cycle $ c $ in $ g $ with $ f ( c ) \ leq ( 1 + \ varepsilon ) \ cdot \ textsf { opt } $. this is in sharp contrast with the non - approximability of the closely related monotone submodular shortest $ ( s, t ) $ - path problem, which requires exponentially many queries to the oracle for finding an $ n ^ { 2 / 3 - \ varepsilon } $ - approximation [ goel et al., focs 2009 ]. we complement our algorithm with a matching lower bound. we show that for every $ \ varepsilon > 0 $, obtaining a $ ( 1 + \ varepsilon ) $ - approximation requires at least $ n ^ { \ omega ( \ log 1 / \ varepsilon ) } $ queries to the oracle. when the function $ f $ is integer - valued, our algorithm yields that a cycle of cost $ \ textsf { opt } $ can be found in time $ n ^ { \ mathcal { o } ( \ log \ textsf { opt } ) } $. in particular, for $ \ textsf { opt } = n ^ { \ mathcal { o } ( 1 ) } $ this gives a quasipolynomial - time algorithm computing a cycle of minimum submodular cost. interestingly, while a quasipolynomial - time algorithm often serves as a good indication that a polynomial time complexity could be achieved, we show a lower bound that $ n ^ { \ mathcal { o } ( \ log n ) } $ queries are required even when $ \ textsf { opt } = \ mathcal { o } ( n ) $. | arxiv:2211.04797 |
using few - body simulations, we investigate the evolution of supermassive black holes ( smbhs ) in galaxies ( $ m _ { \ star } = 10 ^ { 10 } - 10 ^ { 12 } { \ rm m } _ { \ odot } $ at $ z = 0 $ ) at $ 0 < z < 4 $. following galaxy merger trees from the millennium simulation, we model bh mergers with two extreme binary decay scenarios for the ` hard binary ' stage : a full or an empty loss cone. these two models should bracket the true evolution, and allow us to separately explore the role of dynamical friction and that of multi - body bh interactions on bh mergers. using the computed merger rates, we infer the stochastic gravitational wave background ( gwb ). our dynamical approach is a first attempt to study the dynamical evolution of multiple smbhs in the host galaxies undergoing mergers with various mass ratios ( $ 10 ^ { - 4 } < q _ { \ star } < 1 $ ). our main result demonstrates that smbh binaries are able to merge in both scenarios. in the empty loss cone case, we find that bhs merge via multi - body interactions, avoiding the ` final parsec ' problem, and entering the pta band with substantial orbital eccentricity. our full loss cone treatment, albeit more approximate, suggests that the eccentricity becomes even higher when gws become dominant, leading to rapid coalescences ( binary lifetime $ \ lesssim1 { \ rm ~ gyr } $ ). despite the lower merger rates in the empty loss cone case, due to their higher mass ratios and lower redshifts, the gwb in the full / empty loss cone models are comparable ( $ 0. 70 \ times10 ^ { - 15 } $ and $ 0. 53 \ times10 ^ { - 15 } $ at a frequency of $ 1 ~ { \ rm yr } ^ { - 1 } $, respectively ). finally, we compute the effects of high eccentricities on the gwb spectrum. | arxiv:1709.06501 |
we show that the wiedemann - franz law is violated in the vortex state of a d - wave superconductor at zero temperature. we use a semiclassical approach, which includes the doppler shift on the quasiparticles as well as the andreev scattering from a random distribution of vortices. we also show that the vertex corrections to the electrical conductivity due to the anisotropy of impurity scattering become unimportant in the presence of a sufficiently large magnetic field. | arxiv:cond-mat/0304220 |
the quasi - neutral hybrid model with kinetic ions and fluid electrons is a promising approach for bridging the inherent multi - scale nature of many problems in space and laboratory plasmas. here, a novel, implicit, particle - in - cell based scheme for the hybrid model is derived for multi - dimensional electromagnetic problems with multiple ion species, which features global mass, momentum and energy conservation. the scheme includes sub - cycling and orbit averaging of the ions, with cell - centered finite differences and implicit midpoint time advance. to reduce discrete particle noise, the scheme allows arbitrary - order shape functions for the particle - mesh interpolations and the application of conservative binomial smoothing. the algorithm is verified for a number of test problems to demonstrate the correctness of the implementation, the unique conservation properties, and the favorable stability properties of the new scheme. in particular, there is no indication of unstable growth of the finite - grid instability for a population of cold ions drifting through a uniform spatial mesh, in a set - up where several commonly used non - conservative schemes are highly unstable. | arxiv:1803.07158 |
cardiac magnetic resonance imaging ( cmri ) is an integral part of diagnosis in many heart related diseases. recently, deep neural networks have demonstrated successful automatic segmentation, thus alleviating the burden of time - consuming manual contouring of cardiac structures. moreover, frameworks such as nnu - net provide entirely automatic model configuration to unseen datasets enabling out - of - the - box application even by non - experts. however, current studies commonly neglect the clinically realistic scenario, in which a trained network is applied to data from a different domain such as deviating scanners or imaging protocols. this potentially leads to unexpected performance drops of deep learning models in real life applications. in this work, we systematically study challenges and opportunities of domain transfer across images from multiple clinical centres and scanner vendors. in order to maintain out - of - the - box usability, we build upon a fixed u - net architecture configured by the nnu - net framework to investigate various data augmentation techniques and batch normalization layers as an easy - to - customize pipeline component and provide general guidelines on how to improve domain generalizability abilities in existing deep learning methods. our proposed method ranked first at the multi - centre, multi - vendor & multi - disease cardiac image segmentation challenge ( m & ms ). | arxiv:2011.07592 |
a description of eigensubspaces of the cosine and sine operators is presented. the spectrum of each of these two operator consists of two eigenvalues ( 1, \, - 1 ) and their eigensubspaces are infinite - - dimensional. there are many possible bases for these subspaces, but most popular are bases constructed from the hermite functions. we present other " bases " which are not discrete orthogonal sequences of vectors, but continuous orthogonal chains of vectors. our work can be considered a continuation and further development of results in \ textit { self - reciprocal functions } by hardy and titchmarsh : quarterly journ. of math. ( oxford ser. ) \ textbf { 1 } ( 1930 ). | arxiv:1203.2427 |
self - supervised learning shows promise in harnessing extensive unlabeled data, but it also confronts significant privacy concerns, especially in vision. in this paper, we aim to perform membership inference on visual self - supervised models in a more realistic setting : self - supervised training method and details are unknown for an adversary when attacking as he usually faces a black - box system in practice. in this setting, considering that self - supervised model could be trained by completely different self - supervised paradigms, e. g., masked image modeling and contrastive learning, with complex training details, we propose a unified membership inference method called partcrop. it is motivated by the shared part - aware capability among models and stronger part response on the training data. specifically, partcrop crops parts of objects in an image to query responses with the image in representation space. we conduct extensive attacks on self - supervised models with different training protocols and structures using three widely used image datasets. the results verify the effectiveness and generalization of partcrop. moreover, to defend against partcrop, we evaluate two common approaches, i. e., early stop and differential privacy, and propose a tailored method called shrinking crop scale range. the defense experiments indicate that all of them are effective. our code is available at https : / / github. com / jiepku / partcrop. | arxiv:2404.02462 |
in this paper, we obtain and study typical beam entropy values for millimetre wave ( mm - wave ) channel models using the nyusim simulator for frequencies up to 100 ghz for fifth generation ( 5g ) and beyond 5g cellular communication systems. the beam entropy is used to quantify sparse mimo channel randomness in beamspace. lower relative beam entropy channels are suitable for memory - assisted statistically - ranked ( mars ) and hybrid radio frequency ( rf ) beam training algorithms. high beam entropies can potentially be advantageous for low overhead secured radio communications by generating cryptographic keys based on channel randomness in beamspace, especially for sparse multiple input multiple output ( mimo ) channels. urban micro ( umi ), urban macro ( uma ) and rural macro ( rma ) cellular scenarios have been investigated in this work for 28, 60, 73 and 100 ghz. | arxiv:1906.07012 |
we study numerically the monopole creation operator proposed recently by frohlich and marchetti. the operator is defined with the help of a three dimensional model which generates random mandelstam strings. these strings imitate the coulombic magnetic field around the monopole. we show that if the mandelstam strings are condensed the creation operator discriminates between the phases with condensed and non - - condensed monopoles in the abelian higgs model with the compact gauge field. | arxiv:hep-lat/0204033 |
the nuclear lattice effective field theory ( nleft ) is an efficient tool for solving nuclear many - body problems, which takes high - fidelity lattice chiral interactions as input and computes nuclear low - energy observables via quantum monte carlo techniques. in this work, we present the first next - to - next - to - next - to - leading order ( n $ ^ 3 $ lo ) chiral forces on the lattice with the isospin - breaking effects fully taken into account. we focus on both the charge - independence breaking ( cib ) and charge - symmetry breaking ( csb ) effects. specifically, we include the isospin - breaking effect from the mass difference between the charged and neutral pions in the one - pion - exchange potential ( opep ), the coulomb force for the $ pp $ interaction and the contribution of two additional charge - dependent contact operators. we also explicitly incorporate the two - pion - exchange potentials which was mostly neglected in previous nleft calculations. with these improvements, we are able to accurately reproduce the $ np $ and $ pp $ scattering phase shifts up to relative momentum $ p \ sim 200 $ mev as well as the deuteron properties. the construction of these charge - dependent lattice nuclear forces establishes a solid foundation for future high - precision nuclear ab initio calculations within the nleft framework. | arxiv:2503.18017 |
we consider a certain local generalization of brs transformations of yang - mills theory in which the anti - commuting parameter is space time dependent. while these are not exact symmetries, they do lead to a new nontrivial wt identity. we make a precise connection between the ` ` local brs " and the broken orthosymplectic symmetry recently found in superspace formulation of yang - mills theory by showing that the local brs wt identity is precisely the wt identity obtained in the superspace formulation via a superrotation. this ` ` local brs " wt identity could lead to new consequences not contained in the usual brs wt identity. | arxiv:hep-th/9512033 |
in the design of multiple description lattice vector quantizers ( mdlvq ), index assignment plays a critical role. in addition, one also needs to choose the voronoi cell size of the central lattice v, the sublattice index n, and the number of side descriptions k to minimize the expected mdlvq distortion, given the total entropy rate of all side descriptions rt and description loss probability p. in this paper we propose a linear - time mdlvq index assignment algorithm for any k > = 2 balanced descriptions in any dimensions, based on a new construction of so - called k - fraction lattice. the algorithm is greedy in nature but is proven to be asymptotically ( n - > infinity ) optimal for any k > = 2 balanced descriptions in any dimensions, given rt and p. the result is stronger when k = 2 : the optimality holds for finite n as well, under some mild conditions. for k > 2, a local adjustment algorithm is developed to augment the greedy index assignment, and conjectured to be optimal for finite n. our algorithmic study also leads to better understanding of v, n and k in optimal mdlvq design. for k = 2 we derive, for the first time, a non - asymptotical closed form expression of the expected distortion of optimal mdlvq in p, rt, n. for k > 2, we tighten the current asymptotic formula of the expected distortion, relating the optimal values of n and k to p and rt more precisely. | arxiv:cs/0609123 |
we have undertaken near - continuous monitoring of the seyfert 1 galaxy ngc 7469 in the x - ray with rxte over a ~ 30d baseline. the source shows strong variability with a root - mean - square ( rms ) amplitude of ~ 16 per cent, and peak - to - peak variations of a factor of order 2. simultaneous data over this period were obtained in the ultraviolet ( uv ) using iue, making this the most intensive x - ray uv / x - ray variability campaign performed for any active galaxy. comparison of the continuum light curves reveals very similar amplitudes of variability, but different variability characteristics, with the x - rays showing much more rapid variations. the data are not strongly correlated at zero lag. the largest absolute value of the correlation coefficient occurs for an anticorrelation between the two bands, with the x - ray variations leading the uv by ~ 4d. the largest positive correlation is for the ultraviolet to lead the x - rays by ~ 4d. neither option appears to be compatible with any simple interband transfer function. the peak positive correlation at ~ 4d occurs because the more prominent peaks in the uv light curve appear to lead those in the x - rays by this amount. however, the minima of the light curves are near - simultaneous. these observations provide new constraints on theoretical models of the central regions of active galactic nuclei. models in which the observed uv emission is produced solely by re - radiation of absorber x - rays are ruled out by our data, as are those in which the x - rays are produced solely by compton upscattering of the observed uv component by a constant distribution of particles. | arxiv:astro-ph/9804135 |
let $ u $ be the quantum group with divided powers in $ l - $ th root of unity and let $ u \ subset u $ be the frobenius kernel. v. ginzburg and s. kumar proved that the cohomology algebra of $ u $ with trivial coefficients is isomorphic to the functions algebra of the nilpotent cone of the corresponding lie algebra. in this note we show that there exists tilting module $ t $ such that the cohomology of $ u $ with coefficients in $ t $ is isomorphic to the functions algebra of the closure of the subregular nilpotent orbit. | arxiv:math/9902094 |
we suggest that the dark matter model based on bose einstein condensate or scalar field can resolve the apparently contradictory behaviors of dark matter in the abell 520 and the bullet cluster. during a collision of two galaxies in the cluster, if initial kinetic energy of the galaxies is large enough, two dark matter halos pass each other in a soliton - like way as observed in the bullet cluster. if not, the halos merge due to the tiny repulsive interaction among dark matter particles as observed in the abell 520. this idea can also explain the origin of the dark galaxy and the galaxy without dark matter. | arxiv:0805.3827 |
dark matter ( dm ) haloes forming near the thermal cut - off scale of the density perturbations are unique, since they are the smallest objects and form through monolithic gravitational collapse, while larger haloes contrastingly have experienced mergers. while standard cold dark matter ( cdm ) simulations readily produce haloes that follow the universal navarro - frenk - white ( nfw ) density profile with an inner slope, $ \ rho \ propto r ^ { - \ alpha } $, with $ \ alpha = 1 $, recent simulations have found that when the free - streaming cut - off expected for the cdm model is resolved, the resulting haloes follow nearly power - law density profiles of $ \ alpha \ sim1. 5 $. in this paper, we study the formation of density cusps in haloes using idealized $ n $ - body simulations of the collapse of proto - haloes. when the proto - halo profile is initially cored due to particle free - streaming at high redshift, we universally find $ \ sim r ^ { - 1. 5 } $ profiles irrespective of the proto - halo profile slope outside the core and large - scale non - spherical perturbations. quite in contrast, when the proto - halo has a power - law profile, then we obtain profiles compatible with the nfw shape when the density slope of the proto - halo patch is shallower than a critical value, $ \ alpha _ { \ rm ini } \ sim 0. 3 $, while the final slope can be steeper for $ \ alpha _ { \ rm ini } \ ga 0. 3 $. we further demonstrate that the $ r ^ { - 1. 5 } $ profiles are sensitive to small scale noise, which gradually drives them towards an inner slope of $ - 1 $, where they become resilient to such perturbations. we demonstrate that the $ r ^ { - 1. 5 } $ solutions are in hydrostatic equilibrium, largely consistent with a simple analytic model, and provide arguments that angular momentum appears to determine the inner slope. | arxiv:1707.07693 |
petri nets are a classical model of concurrency widely used and studied in formal verification with many applications in modeling and analyzing hardware and software, data bases, and reactive systems. the reachability problem is central since many other problems reduce to reachability questions. the reachability problem is known to be decidable but its complexity is extremely high ( non primitive recursive ). in 2011, a variant of the reachability problem, called the mutual reachability problem, that consists in deciding if two configurations are mutually reachable was proved to be exponential - space complete. recently, this problem found several unexpected applications in particular in the theory of population protocols. while the mutual reachability problem is known to be definable in the preburger arithmetic, the best known upper bound of such a formula was recently proved to be non - elementary ( tower ). in this paper we provide a way to compile the mutual reachability relation of a petri net with $ d $ counters into a quantifier - free presburger formula given as a doubly exponential disjunction of $ o ( d ) $ linear constraints of exponential size. we also provide some first results about presburger formulas encoding bottom configurations. | arxiv:2210.09931 |
colliding - wind binaries ( cwbs ) constitute an emerging class of $ \ gamma $ - ray sources powered by strong, dense winds in massive stellar systems. the most powerful of them are those binaries hosting a wolf - rayet ( wr ) star. following the recent discovery of apep - - the closest known galactic wr - - wr binary - - we discuss the non - detection of its putative high - energy emission by the fermi large area telescope ( fermi - lat ) in this letter. the limits reported in the gev regime can be used to set a lower limit on the magnetic field pressure density within the shocked wind - collision region ( wcr ), and to exclude apep as a bright gamma - ray emitting binary. given that this wr - - wr system is the most luminous cwb identified until now at radio wavelengths, this result proves unambiguously that non - thermal synchrotron emission is not a suitable identifier for the subset of gamma - ray emitters in this class of particle accelerators. rather, apep could be an interesting case of study for magnetic field amplification in shocked stellar winds. | arxiv:2212.10146 |
we examine the effect of self - gravity in a rotating thick - disk equilibrium in the presence of a dipolar magnetic field. in the first part, we find a self - similar solution for non - self - gravitating disks. the solution that we have found shows that the pressure and density equilibrium profiles are strongly modified by a self - consistent toroidal magnetic field. we introduce 3 dimensionless variables $ c _ b $, $ c _ c $, $ c _ t $ that indicate the relative importance of toroidal component of magnetic field ( $ c _ b $ ), centrifugal ( $ c _ c $ ) and thermal ( $ c _ t $ ) energy with respect to the gravitational potential energy of the central object. we study the effect of each of them on the structure of the disk. in the second part, we investigate the effect of self - gravity on the these disks ; thus we introduce another dimensionless variable ( $ c _ g $ ) that shows the importance of self - gravity. we find a self - similar solution for the equations of the system. our solution shows that the structure of the disk is modified by the self - gravitation of the disk, the magnetic field of the central object, and the azimuthal velocity of the gas disk. we find that self - gravity and magnetism from the central object can change the thickness and the shape of the disk. we show that as the effect of self - gravity increases the disk becomes thinner. we also show that for different values of the star ' s magnetic field and of the disk ' s azimuthal velocity, the disk ' s shape and its density and pressure profiles are strongly modified. | arxiv:astro-ph/0402434 |
i review four decades of numerical simulations of galaxy clusters focussing on the attempts to resolve their internal structure. overmerging describes the numerical or physical disruption of dark matter halos within dense environments. this problem was inherent in simulations prior to 1998 but can be completely overcome with current algorithms and hardware. we can now resolve many thousands of subhalos within clusters and we may have converged on their inner structure, allowing several new tests of the hierarchical structure formation model and the nature of dark matter. | arxiv:astro-ph/0009247 |
we consider the summability of one - and multi - dimensional trigonometric fourier series. the fej { \ ' e } r and riesz summability methods are investigated in detail. different types of summation and convergence are considered. we will prove that the maximal operator of the summability means is bounded from the hardy space $ h _ p $ to $ l _ p $, for all $ p > p _ 0 $, where $ p _ 0 $ depends on the summability method and the dimension. for $ p = 1 $, we obtain a weak type inequality by interpolation, which ensures the almost everywhere convergence of the summability means. similar results are formulated for the more general $ \ theta $ - summability and for fourier transforms. | arxiv:1206.1789 |
nanograv and other pulsar timing arrays ( ptas ) have discovered a common - spectrum process in the nhz range that may be due to gravitational waves ( gws ) : if so, they are likely to have been generated by black hole ( bh ) binaries with total masses $ > 10 ^ 9 m _ { \ odot } $. using the extended press - schechter formalism to model the galactic halo mass function and a simple relation between the halo and bh masses suggests that these binaries have redshifts $ z = { o } ( 1 ) $ and mass ratios $ \ gtrsim 10 $, and that the gw signal at frequencies above $ { o } ( 10 ) $ ~ nhz may be dominated by relatively few binaries that could be distinguished experimentally and would yield observable circular polarization. extrapolating the model to higher frequencies indicates that future gw detectors such as lisa and aedge could extend the pta observations to lower bh masses $ \ in ( 10 ^ 6, 10 ^ 9 ) m _ { \ odot } $ and $ \ in ( 10 ^ 3, 10 ^ 9 ) m _ { \ odot } $. | arxiv:2301.13854 |
weak gravitational lensing provides a sensitive probe of cosmology by measuring the mass distribution and the geometry of the low redshift universe. we show how an all - sky weak lensing tomographic survey can jointly constrain different sets of cosmological parameters describing dark energy, massive neutrinos ( hot dark matter ), and the primordial power spectrum. in order to put all sectors on an equal footing, we introduce a new parameter $ \ beta $, the second order running spectral index. using the fisher matrix formalism with and without cmb priors, we examine how the constraints vary as the parameter set is enlarged. we find that weak lensing with cmb priors provides robust constraints on dark energy parameters and can simultaneously provide strong constraints on all three sectors. we find that the dark energy sector is largely insensitive to the inclusion of the other cosmological sectors. implications for the planning of future surveys are discussed. | arxiv:0911.3448 |
we investigate theoretically the freezing behaviour of a two - dimensional ( 2d ) system of hard discs on a one - dimensional ( 1d ) external potential ( typically called laser - induced freezing ). as shown by earlier theoretical and numerical studies, one observes freezing of the modulated liquid upon increase of the substrate potential amplitude, and re - entrant melting back into the modulated liquid when the substrate potential amplitude is increased even further. the purpose of our present work is to calculate the freezing and re - entrant melting phase diagram based on information from the bulk system. to this end, we employ an integrated pressure - balance equation derived from density functional theory [ phys. rev. e \ textbf { 101 }, 012609 ( 2020 ) ]. furthermore, we define a measure to quantify the influence of registration effects that qualitatively explain re - entrant melting. despite severe approximations, the calculated phase diagram shows good agreement with the known phase diagram obtained by monte carlo simulations. | arxiv:2007.05977 |
research in combating misinformation reports many negative results : facts may not change minds, especially if they come from sources that are not trusted. individuals can disregard and justify lies told by trusted sources. this problem is made even worse by social recommendation algorithms which help amplify conspiracy theories and information confirming one ' s own biases due to companies ' efforts to optimize for clicks and watch time over individuals ' own values and public good. as a result, more nuanced voices and facts are drowned out by a continuous erosion of trust in better information sources. most misinformation mitigation techniques assume that discrediting, filtering, or demoting low veracity information will help news consumers make better information decisions. however, these negative results indicate that some news consumers, particularly extreme or conspiracy news consumers will not be helped. we argue that, given this background, technology solutions to combating misinformation should not simply seek facts or discredit bad news sources, but instead use more subtle nudges towards better information consumption. repeated exposure to such nudges can help promote trust in better information sources and also improve societal outcomes in the long run. in this article, we will talk about technological solutions that can help us in developing such an approach, and introduce one such model called trust nudging. | arxiv:1911.05825 |
covid - 19 abatement strategies have risks and uncertainties which could lead to repeating waves of infection. we show - - as proof of concept grounded on rigorous mathematical evidence - - that periodic, high - frequency alternation of into, and out - of, lockdown effectively mitigates second - wave effects, while allowing continued, albeit reduced, economic activity. periodicity confers ( i ) predictability, which is essential for economic sustainability, and ( ii ) robustness, since lockdown periods are not activated by uncertain measurements over short time scales. in turn - - while not eliminating the virus - - this fast switching policy is sustainable over time, and it mitigates the infection until a vaccine or treatment becomes available, while alleviating the social costs associated with long lockdowns. typically, the policy might be in the form of 1 - day of work followed by 6 - days of lockdown every week ( or perhaps 2 days working, 5 days off ) and it can be modified at a slow - rate based on measurements filtered over longer time scales. our results highlight the potential efficacy of high frequency switching interventions in post lockdown mitigation. all code is available on github ( https : / / github. com / v4p1d / fpsp _ covid19 ). a software tool has also been developed so that interested parties can explore the proof - of - concept system. | arxiv:2003.09930 |
we present a physics - based framework to simulate porous, deformable materials and interactive tools with haptic feedback that can reshape it. in order to allow the material to be moulded non - homogeneously, we propose an algorithm to change the material properties of the object depending on its water content. we present a multi - resolution, multi - timescale simulation framework to enable stable visual and haptic feedback at interactive rates. we test our model for physical consistency, accuracy, interactivity and appeal through a user study and quantitative performance evaluation. | arxiv:2112.04362 |
the scope of the present paper is to determine how ion electrostatic wave perturbations in plasma flows are influenced by the presence of a kinematically complex velocity shear. for this purpose we consider a model based on the following set of physical equations : the equation of motion, the continuity equation and the poisson equation for the electric potential governing the evolution of the system. after linearizing the equations, we solve them numerically. we find out that for a variety of specific values of parameters the system may exhibit quite interesting dynamic behaviour. in particular, we demonstrate that the system exhibits two different kinds of shear flow instabilities : ( a ) ~ when the wave vectors evolve exponentially, the ion sound modes become unstable as well ; while, ( b ) ~ on the other hand, one can find areas in a parametric space where, when the wave vectors vary periodically, the physical system is subject to a strongly pronounced parametric instability. we also show the possibility of the generation of beat wave phenomena, characterized by a noteworthy quasi - periodic temporal behaviour. in the conclusion, we discuss the possible areas of applications and further directions of generalization of the presented work. | arxiv:1504.04292 |
we propose a computationally efficient alternative to generalized random forests arxiv : 1610. 01271 ( grfs ) for estimating heterogeneous effects in large dimensions. while grfs rely on a gradient - based splitting criterion, which in large dimensions is computationally expensive and unstable, our method introduces a fixed - point approximation that eliminates the need for jacobian estimation. this gradient - free approach preserves grfs theoretical guarantees of consistency and asymptotic normality while significantly improving computational efficiency. we demonstrate that our method achieves multiple times the speed over standard grfs without compromising statistical accuracy. experiments on both simulated and real - world data, validate our approach. our findings suggest that the proposed method is a scalable alternative for localized effect estimation in machine learning and causal inference applications. | arxiv:2306.11908 |
we use quantum monte carlo methods to determine $ t = 0 $ green functions, $ g ( \ vec { r }, \ omega ) $, on lattices up to $ 16 \ times 16 $ for the 2d hubbard model at $ u / t = 4 $. for chemical potentials, $ \ mu $, within the hubbard gap, $ | \ mu | < \ mu _ c $, and at { \ it long } distances, $ \ vec { r } $, $ g ( \ vec { r }, \ omega = \ mu ) \ sim e ^ { - | \ vec { r } | / \ xi _ l } $ with critical behavior : $ \ xi _ l \ sim | \ mu - \ mu _ c | ^ { - \ nu } $, $ \ nu = 0. 26 \ pm 0. 05 $. this result stands in agreement with the assumption of hyperscaling with correlation exponent $ \ nu = 1 / 4 $ and dynamical exponent $ z = 4 $. in contrast, the generic band insulator as well as the metal - insulator transition in the 1d hubbard model are characterized by $ \ nu = 1 / 2 $ and $ z = 2 $. | arxiv:cond-mat/9510084 |
we report on the design, manufacturing, and performance of the image slicer for the high dispersion spectrograph ( hds ) on the subaru telescope. this instrument is a bowen - walraven type image slicer providing five 0. 3 arcsec x 1. 5 arcsec images with a resolving power of r = 110, 000. the resulting resolving power and line profiles are investigated in detail, including estimates of the defocusing effect on the resolving power. the throughput in the wavelength range from 400 to 700 nm is higher than 80 %, thereby improving the efficiency of the spectrograph by a factor of 1. 8 for 0. 7 arcsec seeing. | arxiv:1203.5568 |
we report the first beam - target double - polarization asymmetries in the $ \ gamma + n ( p ) \ rightarrow \ pi ^ - + p ( p ) $ reaction spanning the nucleon resonance region from invariant mass $ w $ = $ 1500 $ to $ 2300 $ mev. circularly polarized photons and longitudinally polarized deuterons in $ h \! d $ have been used with the clas detector at jefferson lab. the exclusive final state has been extracted using three very different analyses that show excellent agreement, and these have been used to deduce the { \ it { e } } polarization observable for an effective neutron target. these results have been incorporated into new partial wave analyses, and have led to significant revisions for several $ \ gamma nn ^ * $ resonance photo - couplings. | arxiv:1705.04713 |
this paper describes a cryogenic optical testbed developed to characterize u - spec spectrometers in a dedicated dilution refrigerator ( dr ) system. u - spec is a far - infrared integrated spectrometer that is an analog to a rowland - type grating spectrometer. it employs a single - crystal silicon substrate with niobium microstrip lines and aluminum kinetic inductance detectors ( kids ). current designs with a resolution of 512 are in fabrication for the exclaim ( experiment for cryogenic large aperture intensity mapping ) balloon mission. the primary spectrometer performance and design parameters are efficiency, nep, inter - channel isolation, spectral resolution, and frequency response for each channel. here we present the development and design of an optical characterization facility and preliminary validation of that facility with earlier prototype r = 64 devices. we have conducted and describe initial optical measurements of r = 64 devices using a swept photomixer line source. we also discuss the test plan for optical characterization of the exclaim r = 512 u - spec devices in this new testbed. | arxiv:2208.06401 |
in this paper, we introduce an extension of the dirac equation, very similar to dirac oscillator, that gives stationary localized wave packets as eigenstates of the equation. the extension to the dirac equation is achieved through the replacement of the momentum operator by a pt - symmetric generalized momentum operator. in the 1d case, the solutions represent bound particles carrying spin having continuous energy spectrum, where the envelope parameter defines the width of the packet without affecting the dispersion relation of the original dirac equation. in the 2d case, the solutions are localized wave packets and are eigenstates of the third component of total angular momentum and involve bessel functions of integral order. in the 3d case, the solutions are localized spherical wave packets with definite total angular momentum. | arxiv:1902.06232 |
as an extension of the class of algebraic links, a ' campo, gibson, and ishikawa constructed links associated to immersed arcs and trees in a two - dimensional disk. by extending their arguments, we construct links associated to immersed graphs in a disk, and show that such links are quasipositive. | arxiv:math/0409086 |
this paper introduces a quasiequilibrium one - dimensional bose - einstein condensation of photons trapped in a microtube. light modes with a cut - off frequency ( a photon ' s " mass " ) interact through different processes of absorption, emission, and scattering on molecules and atoms. in this paper, we study the conditions for the one - dimensional condensation of light and the role of photon - photon interactions in the system. the technique in use is the matsubara ' s green ' s functions formalism modified for the quasiequilibrium system under study. | arxiv:1512.09257 |
in this work, we study the existence and multiplicity of solutions for a class of problems involving the $ \ phi $ - laplacian operator in a bounded domain, where the nonlinearity has a critical growth. the main tool used is the variational method combined with the genus theory for even functionals. | arxiv:1501.06224 |
each transiting planet discovered is characterized by 7 measurable quantities, that may or may not be linked together ( planet mass, radius, orbital period, and star mass, radius, effective temperature, and metallicity ). correlations between planet mass and period, surface gravity and period, planet radius and star temperature have been previously observed among the known transiting giant planets. two classes of planets have been previously identified based on their safronov number. we use the corotlux code to compare simulated events to the sample of discovered planets and test the statistical significance of these correlations. we first generate a stellar field with planetary companions based on radial velocity discoveries and a planetary evolution model, then apply a detection criterion that includes both statistical and red noise sources. we compare the yield of our simulated survey with the ensemble of 31 well - characterized giant transiting planets, using a multivariate logistic analysis to assess whether the simulated distribution matches the known transiting planets. our multivariate analysis shows that our simulated sample and observations are consistent to 76 %. the mass vs. period correlation for giant planets first observed with radial velocity holds with transiting planets. our model naturally explains the correlation between planet surface gravity and period and the one between planet radius and stellar effective temperature. finally, we are also able to reproduce the previously observed apparent bimodal distribution of safronov numbers in 10 % of our simulated cases, although our model predicts a continuous distribution. this shows that the evidence for the existence of two groups of planets with different intrinsic properties is not statistically significant. | arxiv:0901.3083 |
let $ ( \ mathsf { hypo } _ n, ~ ^ \ sharp ) $ be the hypoplactic monoid of finite rank $ n $ with sch \ " { u } tzenberger ' s involution $ ^ { \ sharp } $. in this paper, we exhibit a faithful representation of $ ( \ mathsf { hypo } _ n, ~ ^ \ sharp ) $ as an involution monoid of upper triangular matrices over any semiring from a large class including the tropical semiring under the skew transposition. we then give a transparent combinatorial characterization of the word identities satisfied by $ ( \ mathsf { hypo } _ n, ~ ^ \ sharp ) $. further, we prove that $ ( \ mathsf { hypo } _ n, ~ ^ \ sharp ) $ is non - finitely based if and only if $ n = 2, 3 $ and give a polynomial time algorithm to check whether a given word identity holds in $ ( \ mathsf { hypo } _ n, ~ ^ \ sharp ) $. | arxiv:2301.12449 |
the problem of software artifact retrieval has the goal to effectively locate software artifacts, such as a piece of source code, in a large code repository. this problem has been traditionally addressed through the textual query. in other words, information retrieval techniques will be exploited based on the textual similarity between queries and textual representation of software artifacts, which is generated by collecting words from comments, identifiers, and descriptions of programs. however, in addition to these semantic information, there are rich information embedded in source codes themselves. these source codes, if analyzed properly, can be a rich source for enhancing the efforts of software artifact retrieval. to this end, in this paper, we develop a feature extraction method on source codes. specifically, this method can capture both the inherent information in the source codes and the semantic information hidden in the comments, descriptions, and identifiers of the source codes. moreover, we design a heterogeneous metric learning approach, which allows to integrate code features and text features into the same latent semantic space. this, in turn, can help to measure the artifact similarity by exploiting the joint power of both code and text features. finally, extensive experiments on real - world data show that the proposed method can help to improve the performances of software artifact retrieval with a significant margin. | arxiv:1409.7165 |
we introduce and prove some basic results about a combinatorial model which produces embedded polygons in the plane. the model is closely related to outer billiards on kites, and also is related to corner percolation, to hooper ' s truchet tile system, to self - similar tilings, and to polyhedron exchange transformations. | arxiv:1506.01202 |
we consider a single stage stochastic program without recourse with a strictly convex loss function. we assume a compact decision space and grid it with a finite set of points. in addition, we assume that the decision maker can generate samples of the stochastic variable independently at each grid point and form a sample average approximation ( saa ) of the stochastic program. our objective in this paper is to characterize an asymptotically optimal linear sample allocation rule, given a fixed sampling budget, which maximizes the decay rate of probability of making false decision. | arxiv:1811.07186 |
when used in a real - world noisy environment, the capacity to generalize to multiple domains is essential for any autonomous scene text spotting system. however, existing state - of - the - art methods employ pretraining and fine - tuning strategies on natural scene datasets, which do not exploit the feature interaction across other complex domains. in this work, we explore and investigate the problem of domain - agnostic scene text spotting, i. e., training a model on multi - domain source data such that it can directly generalize to target domains rather than being specialized for a specific domain or scenario. in this regard, we present the community a text spotting validation benchmark called under - water text ( uwt ) for noisy underwater scenes to establish an important case study. moreover, we also design an efficient super - resolution based end - to - end transformer baseline called da - textspotter which achieves comparable or superior performance over existing text spotting architectures for both regular and arbitrary - shaped scene text spotting benchmarks in terms of both accuracy and model efficiency. the dataset, code and pre - trained models will be released upon acceptance. | arxiv:2310.00558 |
a new method is given for computing generators of the homology groups with integer coefficients for any finite $ t _ 0 $ - space. an important role in this method is played by irreducible cycles which are defined here and give rise to continuous injective maps between spaces called immersions. the so - called orb complex which is much smaller than the order complex induces a surjective map of its homology to the simplicial homology of the space. an analysis of the kernel of this map allows to define an effective algorithm for computing the homology groups, whose time complexity is polynomial in the size of the space. | arxiv:1712.08549 |
we present imaging and spectroscopic observations from the interface region imaging spectrograph ( iris ) of the evolution of the flare ribbon in the sol2014 - 04 - 18t13 : 03 m - class flare event, at high spatial resolution and time cadence. these observations reveal small - scale substructure within the ribbon, which manifests as coherent quasi - periodic oscillations in both position and doppler velocities. we consider various alternative explanations for these oscillations, including modulation of chromospheric evaporation flows. among these we find the best support for some form of wave localized to the coronal current sheet, such as a tearing mode or kelvin - helmholtz instability. | arxiv:1507.01554 |
answering temporal cqs over temporalized description logic knowledge bases ( tkb ) is a main technique to realize ontology - based situation recognition. in case the collected data in such a knowledge base is inaccurate, important query answers can be missed. in this paper we introduce the tkb alignment problem, which computes a variant of the tkb that minimally changes the tkb, but entails the given temporal cq and is in that sense ( cost - ) optimal. we investigate this problem for alc tkbs and conjunctive queries with ltl operators and devise a solution technique to compute ( cost - optimal ) alignments of tkbs that extends techniques for the alignment problem for propositional ltl over finite traces. | arxiv:2307.15439 |
combining molecular simulation, onsager theory and the elastic description of nematic liquid crystals, we study the dependence of the nematic liquid crystal elastic constants and the zenithal surface anchoring coefficient on the value of the bulk order parameter. | arxiv:cond-mat/0203016 |
we give a short and elementary proof that the first hitting time of an open set by the jump process of a c \ ` adl \ ` ag adapted process is a stopping time. | arxiv:1205.2479 |
in this contribution we discuss the inclusive production of jets in central regions of rapidity in the context of $ k _ t $ - factorization at next - to - leading order ( nlo ). we work in the regge limit of qcd and use the nlo bfkl results. a jet cone definition is proposed together with a phase - space separation into multi - regge and quasi - multi - regge kinematics. we discuss scattering of highly virtual photons, with a symmetric energy scale to separate the impact factors from the gluon green ' s function, and hadron - hadron collisions, with a non - symmetric scale choice. | arxiv:hep-ph/0611137 |
we study possibilities of creation and detection of oscillating gravitational fields from lab - scale high energy, relativistic sources. the sources considered are high energy laser beams in an optical cavity and the ultra - relativistic proton bunches circulating in the beam of the large hadron collider ( lhc ) at cern. these sources allow for signal frequencies much higher and far narrower in bandwidth than what most celestial sources produce. in addition, by modulating the beams, one can adjust the source frequency over a very broad range, from hz to ghz. the gravitational field of these sources and responses of a variety of detectors are analyzed. we optimize a mechanical oscillator such as a pendulum or torsion balance as detector and find parameter regimes such that - - combined with the planned high - luminosity upgrade of the lhc as a source - - a signal - to - noise ratio substantially larger than 1 should be achievable at least in principle, neglecting all sources of technical noise. this opens new perspectives of studying general relativistic effects and possibly quantum - gravitational effects with ultra - relativistic, well - controlled terrestrial sources. | arxiv:2104.09209 |
studies on star clusters with the same age and initial chemical composition have gained momentum in recent years with the use of \ textit { gaia }. in addition, the discovery of new clusters with gaia has increased the number of open clusters to be examined. many of these discovered sources are intermediate - age open clusters and have not been analyzed in detail yet. in this study, we focused on newly cataloged open cluster upk ~ 220. the fundamental parameters ( distance, age, metallicity and reddening ) of upk ~ 220 were determined by analysing the variable stars within the cluster, while simultaneously constraining the parameters of the variable stars using these cluster parameters. to achieve this, we combined gaiadr3 and tess photometric observations. using gaiadr3, we derive fundamental parameters of upk ~ 220 through membership analyses, and with tess, we discovered eight member variable stars. we also extracted the atmospheric parameters ( $ logg $, $ [ fe / h ] $ and $ t _ { \ rm eff } $ ) for the variable stars using sed, gsp - phot and gsp - spec, and mesa models. | arxiv:2502.03861 |
ieee 802. 11ad - based integrated sensing and communications ( isac ) have been identified as a potential solution for enabling next - generation intelligent transportation systems in the millimeter wave ( mmw ) spectrum. the radar functionality within the isac enables accurate detection and localization of mobile targets, which can significantly speed up the selection of the optimal high - directional narrow beam required for mmw communications between the base station and mobile target. to bring isac to reality, a radar signal processing ( rsp ) accelerator, co - located with the wireless communication physical layer ( phy ), on edge platforms, is desired. in this work, we discuss the three - dimensional digital hardware rsp framework for 802. 11ad - based isac to detect the range, azimuth, and doppler velocity of multiple targets. we present an efficient reconfigurable architecture for rsp on multi - processor system - on - chip ( mpsoc ) via hardware - software co - design, word - length optimization, and serial - parallel configurations. we demonstrate the functional correctness of the proposed fixed - point architecture and significant savings in resource utilization ( 40 - 70 % ), execution time ( 1. 5x improvement ), and power consumption ( 50 % ) over floating - point architecture. the acceleration on hardware offers a 120 - factor improvement in execution time over the benchmark quad - core processor. the proposed architecture enables on - the - fly reconfigurability to support different azimuth precision and doppler velocity resolution, offering a real - time trade - off between functional accuracy and detection time. we implement end - to - end isac comprising rsp and phy on mpsoc and demonstrate significant improvement in throughput over ieee 802. 11ad. | arxiv:2303.01702 |
using classical model atmospheres and an lte analysis, mg isotope ratios 24mg : 25mg : 26mg are measured in 32 hyades dwarfs covering 4000k < teff < 5000k. we find no significant trend in any isotope ratio versus teff and the mean isotope ratio is in excellent agreement with the solar value. we determine stellar parameters and fe abundances for 56 hyades dwarfs covering 4000k < teff < 6200k. for stars warmer than 4700k, we derive a cluster mean value of [ fe / h ] = 0. 16 + / - 0. 02 ( sigma = 0. 1 ), in good agreement with previous studies. for stars cooler than 4700k, we find that the abundance of fe from ionized lines exceeds the abundance of fe from neutral lines. at 4700k [ fe / h ] _ ii - [ fe / h ] _ i = 0. 3 dex while at 4000k [ fe / h ] _ ii - [ fe / h ] _ i = 1. 2 dex. this discrepancy between the fe abundance from neutral and ionized lines likely reflects inadequacies in the model atmospheres and the presence of non - lte or other effects. despite the inability of the models to reproduce ionization equilibrium for fe, the mg isotope ratios appear immune to these problems and remain a powerful tool for studying galactic chemical evolution. | arxiv:astro-ph/0312054 |
using an algebraic method for solving the wave equation in quantum mechanics, we encountered a new class of orthogonal polynomials on the real line. it consists of a four - parameter polynomial with continuous spectrum on the whole real line and two of its discrete versions ; one with a finite spectrum and another with countably infinite spectrum. a second class of these new orthogonal polynomials appeared recently while solving a heun - type equation. based on these results and on our recent study of the solution space of an ordinary differential equation of the second kind with four singular points, we introduce a modification of the askey scheme of hyper - geometric orthogonal polynomials. up to now, these polynomials are defined by their three - term recursion relations and initial values. however, their other properties like the weight functions, generating functions, orthogonality, rodrigues - type formulas, etc. are yet to be derived analytically. due to the prime significance of these polynomials in physics and mathematics, we call upon experts in the field of orthogonal polynomials to study them, derive their properties and write them in closed form ( e. g., in terms of hypergeometric functions ). | arxiv:1709.06081 |
in this paper, we consider cell - free communication systems with several access points ( aps ) serving terrestrial users ( ues ) simultaneously. to enhance the uplink multi - user multiple - input multiple - output communications, we adopt a hybrid - csi - based two - layer distributed multi - user detection scheme comprising the local minimum mean - squared error ( mmse ) detection at aps and the one - shot weighted combining at the central processing unit ( cpu ). furthermore, to improve the propagation environment, we introduce multiple reconfigurable intelligent surfaces ( riss ) to assist the transmissions from ues to aps. aiming to maximize the weighted sum rate, we formulate the weighted sum - mmse ( wmmse ) problem, where the ues ' beamforming matrices, the cpu ' s weighted combining matrix, and the riss ' phase - shifting matrices are alternately optimized. considering the limited fronthaul capacity constraint in cell - free networks, we resort to the operator - valued free probability theory to derive the asymptotic alternating optimization ( ao ) algorithm to solve the wmmse problem, which only depends on long - term channel statistics and thus reduces the interaction overhead. numerical results demonstrate that the asymptotic ao algorithm can achieve a high communication rate as well as reduce the interaction overhead. | arxiv:2412.03175 |
in this paper we study $ n $ - dimensional ricci flows $ ( m ^ n, g ( t ) ) _ { t \ in [ 0, t ) }, $ where $ t < \ infty $ is a potentially singular time, and for which the spatial $ l ^ p $ norm, $ p > \ frac n 2 $, of the scalar curvature is uniformly bounded on $ [ 0, t ). $ in the case that $ m $ is closed and four dimensional, we explain why non - collapsing estimates hold and how they can be combined with integral bounds on the ricci and full curvature tensor of the prequel paper of the authors, as well as non - inflating estimates ( already known due to works of bamler ), to obtain an improved space time integral bound of the ricci curvature. as an application of these estimates, we show that if we further restrict to $ n = 4 $, then the solution convergences to an orbifold as $ t \ to t $ and that the flow can be extended using the orbifold ricci flow to the time interval $ [ 0, t + \ sigma ) $ for some $ \ sigma > 0. $ we also prove local versions of many of the results mentioned above. | arxiv:2410.08667 |
we prove that any mild solution in the koch - - tataru space to the incompressible navier - - stokes equation with initial data in $ \ mathrm { bmo } ^ { - 1 } $ is weak * - continuous in time, valued in $ \ mathrm { bmo } ^ { - 1 } $. we also show that the global mild solution vanishes in $ \ mathrm { bmo } ^ { - 1 } $ at infinity in time. | arxiv:2410.16468 |
we discuss the status of different determinations of alpha _ s, motivating a precise and reliable computation from lattice qcd. in order to suppress perturbative errors, the non - perturbative computation has to reach high energy scales mu. such results already exist in the sf - scheme for n _ f = 0, 2 and n _ f = 3. we recently added the running with four massless flavours in a range of alpha from about 0. 07 to 0. 3. it is based on our recent determination of the sheikholeslami wohlert coefficient in the four - flavour theory. | arxiv:1011.2332 |
we propose a new model selection method, the posterior averaging information criterion, for bayesian model assessment from a predictive perspective. the theoretical foundation is built on the kullback - leibler divergence to quantify the similarity between the proposed candidate model and the underlying true model. from a bayesian perspective, our method evaluates the candidate models over the entire posterior distribution in terms of predicting a future independent observation. without assuming that the true distribution is contained in the candidate models, the new criterion is developed by correcting the asymptotic bias of the posterior mean of the log - likelihood against its expected log - likelihood. it can be generally applied even for bayesian models with degenerate non - informative prior. the simulation in both normal and binomial settings demonstrates decent small sample performance. | arxiv:2009.09248 |
a stochastic model for the field - driven polarization reversal in rhombohedral ferroelectrics is developed, providing a description of their temporal electromechanical response. application of the model to simultaneous measurements of polarization and strain kinetics in a rhombohedral pb ( zr, ti ) o3 ceramic over a wide time window allows identification of preferable switching paths, fractions of individual switching processes, and their activation fields. complementary, the phenomenological landau - ginzburg - devenshire theory is used to analyze the impact of external field and stress on switching barriers showing that residual mechanical stress may promote the fast switching. | arxiv:2004.04966 |
we give a proof of varadhan estimates for a degenerated jump process with independent increments with more and more jumps which become smaller and smaller. the proof uses the malliavin calculus of bismut type for jump process in semi - group theory and wentzel - freidlin estimates for jump process in semi - group theory. | arxiv:1007.0653 |
ground - state and finite - temperature properties of the exactly solvable mixed spin - 1 / 2 ising - heisenberg planar model composed of identical trigonal bipyramids that are arranged into a regular archimedean lattice are examined with the aim to clarify the frustration phenomenon at zero and finite temperatures. it is shown that the ground - state spin frustration persists even far above the second - order phase transition. if the interaction ratio between the heisenberg and ising exchange interactions is close enough to the ground - state boundaries between the neighboring phases, a remarkable re - entrance of the ( non - ) frustrated spin arrangement of the heisenberg spins can be observed around the critical temperature of the model. it is also evidenced that entropy and specific heat show pronounced temperature variations not only around the critical temperature, but also in low - temperature regime if values of the interaction parameters are taken from neighborhood of the ground - state phase transitions, where energies of the neighboring phases are very close. | arxiv:1908.01721 |
as a fundamental notion, the free differential algebra on a set is concretely constructed as the polynomial algebra on the differential variables. such a construction is not known for the more general notion of the free differential algebra on an algebra, from the left adjoint functor of the forgetful functor from differential algebras to algebras, instead of sets. in this paper we show that generator - relation properties of a base algebra can be extended to the free differential algebra on this base algebra. more precisely, a gr \ " obner - shirshov basis property of the base algebra can be extended to the free differential algebra on this base algebra, allowing a poincar \ ' e - birkhoff - witt type basis for these more general free differential algebras. examples are given as illustrations. | arxiv:2009.13847 |
based on a previously proposed thermodynamic analysis, we study the relative stabilities of five si phases under uniaxial compression using ab initio methods. the five phases are diamond, beta - tin, sh, sc, and hcp structures. the possible phase - transition patterns were investigated by considering the phase transitions between any two chosen phases of the five phases. by analyzing the different conributions to the relative pahse stability, we identified the most important factors in reducing the phase - transition pressures at uniaxial compression. we also show that it is possible to have phase transitions occur only when the phases are under uniaxial compression, in spite of no phase transition when under hydrostatic commpression. taking all five phases into consideration, the phase diagram at uniaxial compression was constructed for pressures under 20 gpa. the stable phases were found to be diamond, beta - tin and sh structures, i. e. the same as those when under hydrostatic condition. according to the phase diagram, direct phase transition from the diamond to the sh phase is possible if the applied uniaxial pressures, on increasing, satisfy the condition of px > pz. simiilarly, the sh - to - beta - tin transition on increeasing pressures is also possible if the applied uniaxial pressures are varied from the condition of px > pz, on which the phase of sh is stable, to that of px < pz, on which the beta - tin is stable. | arxiv:cond-mat/0205610 |
lsi + 61 303 is one of the few x - ray binaries with a be star companion from which radio, x - rays and high - energy gamma - ray ( gev and tev ) emission have been observed. the nature of the high energy activity of the system is not yet fully understood, but it is widely believed that it is generated due to the interaction of the relativistic electrons leaving the compact object with the photons and non - relativistic wind of the be star. the superorbital variability of the system has been observed in the radio, optical and x - ray domains and could be due to the cyclic change of the be star disk size. in this paper we systematically review all publicly available data from suzaku, xmm - newton, chandra and swift observatories in order to measure the absorption profile of the circumstellar be disk as a function of orbital and superorbital phases. we also discuss short - term variability of the system, found during the analysis and its implications for the understanding of the physical processes in this system. | arxiv:1705.09343 |
it is conjectured that the coefficients of the jones polynomial can be computed by counting solutions of the kw equations on a four - dimensional half - space, with certain boundary conditions that depend on a knot. the boundary conditions are defined by a " nahm pole " away from the knot with a further singularity along the knot. in a previous paper, we gave a precise formulation of the nahm pole boundary condition in the absence of knots, in the present paper, we do this in the more general case with knots included. we show that the kw equations with generalized nahm pole boundary conditions are elliptic, and that the solutions are polyhomogeneous near the boundary and near the knot, with exponents determined by solutions of appropriate indicial equations. this involves the analysis of a " depth two incomplete iterated edge operator. " as in our previous paper, a key ingredient in the analysis is a convenient new weitzenb \ " ock formula that is well - adapted to the specific problem. } | arxiv:1712.00835 |
we present a comprehensive framework that unifies several research areas within the context of vertex - weighted bipartite graphs, providing deeper insights and improved solutions. the fundamental solution concept for each problem involves refinement, where vertex weights on one side are distributed among incident edges. the primary objective is to identify a refinement pair with specific optimality conditions that can be verified locally. this framework connects existing and new problems that are traditionally studied in different contexts. we explore three main problems : ( 1 ) density - friendly hypergraph decomposition, ( 2 ) universally closest distribution refinements problem, and ( 3 ) symmetric fisher market equilibrium. our framework presents a symmetric view of density - friendly hypergraph decomposition, wherein hyperedges and nodes play symmetric roles. this symmetric decomposition serves as a tool for deriving precise characterizations of optimal solutions for other problems and enables the application of algorithms from one problem to another. | arxiv:2406.17964 |
from a general metric for stationary cyclic symmetric gravitational fields coupled to maxwell electromagnetic fields within the $ ( 2 + 1 ) $ - dimensional gravity the uniqueness of wide families of exact solutions is established, among them, all uniform electromagnetic solutions possessing electromagnetic fields with vanishing covariant derivatives, all fields having constant electromagnetic invariants $ f _ { \ mu \ nu } \, f ^ { \ mu \ nu } $ and $ t _ { \ mu \ nu } \, t ^ { \ mu \ nu } $, the whole classes of hybrid electromagnetic solutions, and also wide classes of stationary solutions are derived for a third order nonlinear key equations. certain of these families can be thought of as black hole solutions. for the most general set of einstein - maxwell equations, reducible to three non - linear equations for the three unknown functions, two new classes of solutions - having anti - de sitter spinning metric limit - are derived. the relationship of various families with those reported by different authors ' solutions has been established. among the classes of solutions with cosmological constant a relevant place occupy : the electrostatic and magnetostatic peldan solutions, the stationary uniform and spinning clement classes, the constant electromagnetic invariant branches with the particular kamata - koikawa solution, the hybrid cyclic symmetric stationary black hole fields, and the non - less important solutions generated via $ sl ( 2, r ) $ transformations where the clement spinning charged solution, the martinez - teitelboim - zanelli black hole solution, and dias - lemos metric merit mention. | arxiv:1307.6655 |
the mini - spiral is a feature of the interstellar medium in the central ~ 2 pc of the galactic center. it is composed of several streamers of dust and ionised and atomic gas with temperatures between a few 100 k to 10 ^ 4 k. there is evidence that these streamers are related to the so - called circumnuclear disk of molecular gas and are ionized by photons from massive, hot stars in the central parsec. we attempt to constrain the emission mechanisms and physical properties of the ionized gas and dust of the mini - spiral region with the help of our multiwavelength data sets. our observations were carried out at 1. 3 mm and 3 mm with the mm interferometric array carma in california in march and april 2009, with the mir instrument visir at eso ' s vlt in june 2006, and the nir br - gamma with vlt naco in august 2009. we present high resolution maps of the mini - spiral, and obtain a spectral index of 0. 5 for sgr a *, indicating an inverted synchrotron spectrum. we find electron densities within the range 0. 8 - 1. 5x10 ^ 4 cm - 3 for the mini - spiral from the radio continuum maps, along with a dust mass contribution of ~ 0. 25 solar masses from the mir dust continuum, and extinctions ranging from 1. 8 - 3 at 2. 16 micron in the br - gamma line. we observe a mixture of negative and positive spectral indices in our 1. 3 mm and 3 mm observations of the extended emission of the mini - spiral, which we interpret as evidence that there are a range of contributions to the thermal free - free emission by the ionized gas emission and by dust at 1. 3 mm. | arxiv:1201.2362 |
we use a replica approach to deal with portfolio optimization problems. a given risk measure is minimized using empirical estimates of asset values correlations. we study the phase transition which happens when the time series is too short with respect to the size of the portfolio. we also study the noise sensitivity of portfolio allocation when this transition is approached. we consider explicitely the cases where the absolute deviation and the conditional value - at - risk are chosen as a risk measure. we show how the replica method can study a wide range of risk measures, and deal with various types of time series correlations, including realistic ones with volatility clustering. | arxiv:physics/0608035 |
we study the mathematical theory of second order systems with two species, arising in the dynamics of interacting particles subject to linear damping, to nonlocal forces and to external ones, and resulting into a nonlocal version of the compressible euler system with linear damping. our results are limited to the $ 1 $ space dimensional case but allow for initial data taken in a wasserstein space of probability measures. we first consider the case of smooth nonlocal interaction potentials, not subject to any symmetry condition, and prove existence and uniqueness. the concept of solutions relies on a stickiness condition in case of collisions, in the spirit of previous works in the literature. the result uses concepts from classical hilbert space theory of gradient flows ( cf. brezis [ 7 ] ) and a trick used in [ 4 ]. we then consider a large - time and large - damping scaled version of our system and prove convergence to solutions to the corresponding first order system. finally, we consider the case of newtonian potentials - - subject to symmetry of the cross - interaction potentials - - and external convex potentials. after showing existence in the sticky particles framework in the spirit of [ 4 ], we prove convergence for large times towards dirac delta solutions for the two densities. all the results share a common technical framework in that solutions are considered in a lagrangian framework, which allows to estimate the behavior of solutions via $ l ^ 2 $ estimates of the pseudo - inverse variables corresponding to the two densities. in particular, due to this technique, the large - damping result holds under a rather weak condition on the initial data, which does not require well - prepared initial velocities. we complement the results with numerical simulations. | arxiv:2210.06162 |
convolutional neural networks ( cnns ) have achieved remarkable success in image recognition. although the internal patterns of the input images are effectively learned by the cnns, these patterns only constitute a small proportion of useful patterns contained in the input images. this can be attributed to the fact that the cnns will stop learning if the learned patterns are enough to make a correct classification. network regularization methods like dropout and spatialdropout can ease this problem. during training, they randomly drop the features. these dropout methods, in essence, change the patterns learned by the networks, and in turn, forces the networks to learn other patterns to make the correct classification. however, the above methods have an important drawback. randomly dropping features is generally inefficient and can introduce unnecessary noise. to tackle this problem, we propose selectscale. instead of randomly dropping units, selectscale selects the important features in networks and adjusts them during training. using selectscale, we improve the performance of cnns on cifar and imagenet. | arxiv:2012.15766 |
some results on cross - diffusion systems with entropy structure are reviewed. the focus is on local - in - time existence results for general systems with normally elliptic diffusion operators, due to amann, and global - in - time existence theorems by lepoutre, moussa, and co - workers for cross - diffusion systems with an additional laplace structure. the boundedness - by - entropy method allows for global bounded weak solutions to certain diffusion systems. furthermore, a partial result on the uniqueness of weak solutions is recalled, and some open problems are presented. | arxiv:1710.01623 |
there are many ways to construct the field r of real numbers. the most important and famous of these employ cauchy sequences ( cantor ) or cuts ( dedekind ) in the field q of rational numbers. these constructions sometimes overlook important details and often are complicated and cumbersome. in this note, the authors propose an essential, clear and rigorous construction of r from the stucture q + of positive rational numbers by the key notion of initial segment. | arxiv:1203.1283 |
location recommendation is defined as to recommend locations ( pois ) to users in location - based services. the existing data - driving approaches of location recommendation suffer from the limitation of the implicit modeling of the geographical factor, which may lead to sub - optimal recommendation results. in this work, we address this problem by introducing knowledge - driven solutions. specifically, we first construct the urban knowledge graph ( urbankg ) with geographical information and functional information of pois. on the other side, there exist a fact that the geographical factor not only characterizes pois but also affects user - poi interactions. to address it, we propose a novel method named ukgc. we first conduct information propagation on two sub - graphs to learn the representations of pois and users. we then fuse two parts of representations by counterfactual learning for the final prediction. extensive experiments on two real - world datasets verify that our method can outperform the state - of - the - art methods. | arxiv:2111.01013 |
we investigate a diffusive motion of a system of interacting brownian particles in quasi - one - dimensional micropores. in particular, we consider a semi - infinite 1d geometry with a partially absorbing boundary and the hard - core inter - particle interaction. due to the absorbing boundary the number of particles in the pore gradually decreases. we present the exact analytical solution of the problem. our procedure merely requires the knowledge of the corresponding single - particle problem. first, we calculate the simultaneous probability density of having still a definite number $ n - k $ of surviving particles at definite coordinates. focusing on an arbitrary tagged particle, we derive the exact probability density of its coordinate. secondly, we present a complete probabilistic description of the emerging escape process. the survival probabilities for the individual particles are calculated, the first and the second moments of the exit times are discussed. generally speaking, although the original inter - particle interaction possesses a point - like character, it induces entropic repulsive forces which, e. g., push the leftmost ( rightmost ) particle towards ( opposite ) the absorbing boundary thereby accelerating ( decelerating ) its escape. more importantly, as compared to the reference problem for the non - interacting particles, the interaction changes the dynamical exponents which characterize the long - time asymptotic dynamics. interesting new insights emerge after we interpret our model in terms of a ) diffusion of a single particle in a $ n $ - dimensional space, and b ) order statistics defined on a system of $ n $ independent, identically distributed random variables. | arxiv:1203.0778 |
rapidity distributions are presented for events containing either a z boson or a photon with a single jet in proton - proton collisions produced at the cern lhc. the data, collected with the cms detector at sqrt ( s ) = 7 tev, correspond to an integrated luminosity of 5. 0 inverse femtobarns. the individual rapidity distributions of the boson and the jet are consistent within 5 % with expectations from perturbative qcd. however, qcd predictions for the sum and the difference in rapidities of the two final - state objects show discrepancies with cms data. in particular, next - to - leading - order qcd calculations, and two common monte carlo event generators using different methods to match matrix - element partons with parton showers, appear inconsistent with the data as well as with each other. | arxiv:1310.3082 |
horizontal federated learning ( fl ) handles multi - client data that share the same set of features, and vertical fl trains a better predictor that combine all the features from different clients. this paper targets solving vertical fl in an asynchronous fashion, and develops a simple fl method. the new method allows each client to run stochastic gradient algorithms without coordination with other clients, so it is suitable for intermittent connectivity of clients. this method further uses a new technique of perturbed local embedding to ensure data privacy and improve communication efficiency. theoretically, we present the convergence rate and privacy level of our method for strongly convex, nonconvex and even nonsmooth objectives separately. empirically, we apply our method to fl on various image and healthcare datasets. the results compare favorably to centralized and synchronous fl methods. | arxiv:2007.06081 |
we study the monge - ampere equation with some power nonlinear term. a solution u is called to be euclidean complete if it is an entire solution defined over the whole r ^ n or its graph is a large hypersurface satisfying the large condition on boundary \ partial \ omega in case \ omega \ not = r ^ n. in this paper, we will give various sharp conditions on p and \ omega classifying the euclidean complete solution. our results clarify and extend largely the existence theorem of cirstea - trombetti ( calc. var., 31, 2008, 167 - 186 ) for bounded convex domain and p > n. | arxiv:2105.04243 |
today, many network applications require shorter react time. robotic field is an excellent example of these needs : robot react time has a direct effect on its task ' s complexity. here, we propose a full deterministic medium access method for a wireless robotic application. this contribution is based on some low - power wireless personal area networks, like zigbee standard. indeed, zigbee has identified limits with quality of service due to non - determinist medium access and probable collisions during medium reservation requests. in this paper, two major improvements are proposed : an efficient polling of the star nodes and a temporal deterministic distribution of peer - to - peer messages. this new mac protocol with no collision offers some qos faculties. | arxiv:0806.2509 |
orientation and microstructure are investigated in sheared brownian suspensions of hard dicolloidal particles, with the dicolloids modeled as two fused spheres of varying radii and center to center separations. two different particle shapes named homonuclear ( aspect ratio 1. 1 ) and fused - dumbbells ( aspect ratio 1. 5 ) were considered. hydrodynamic interactions between the particles were computed with a modified lubrication model called fast lubrication dynamics. studies were conducted for a wide range of volume fractions between $ 0. 3 \ leq \ phi \ leq 0. 5 $ and p \ ` { e } clet numbers between $ 0 \ leq pe \ leq 1000 $. the microstructure was found to be disordered at all volume fractions, though signatures of weak string like ordering were evident particularly in $ \ phi = 0. 5 $ homonuclear suspensions at intermediate to high shear rates ( $ pe $ in the range 10 - 100 ). complex orientation behavior was observed as a function of shape, shear rates, and volume fractions. at very low shear rates, random orientation distribution was observed in all cases. at the highest shear rates, orientation distribution in suspensions of homonuclear particles exhibited a shift towards an alignment with the vorticity axis at all volume fractions, while in suspensions of fused - dumbbells it exhibited a shift away from the vorticity axis at low volume fractions and a negligible shift at higher volume fractions. the orientation behavior is further characterized by examining the orientation distribution in the velocity - - gradient plane - - in this case an increased particle alignment with the velocity axis is generally observed with increasing volume fractions, but not universally with increasing shear rates. mechanistic origins for the complex orientation behavior as a function of shear rate, volume fraction, and particle shape is described. | arxiv:1207.5158 |
we study the brane / flux annihilation in the double - throat system in which the corresponding cycles of two throats are homologically equivalent. when we put $ \ overline { \ rm d3 } $ - branes at only one of throat tips, two throats are no longer identical. then the brane / flux annihilation can be interpreted as the process for reducing the difference between two throat geometries through the transition to the supersymmetric vacuum. to see this, we describe the changes in the amounts of the nsns 3 - form flux supporting the b - cycle contained in two throat regions during the brane / flux annihilation. we also compare our analysis with the recently proposed thraxion scenario, which also describes the inequivalence of two throats caused by the different nsns 3 - form flux distributions in two throat regions. | arxiv:2112.02465 |
microlensing of gravitationally lensed quasars by the stars in the foreground lens galaxy can be used to probe the nature of dark matter, to determine the mean stellar mass in the lens galaxy, and to measure the internal structure of quasar accretion disks. until recently, little progress has been made toward using microlensing for these purposes because of the difficulty in obtaining the necessary data and the lack of good analysis methods. in the last few years, both problems have been solved. in particular, bayesian analysis methods provide a general approach to measuring quantities of physical interest and their uncertainties from microlensing light curves. we discuss the data and the analysis methods and show preliminary results for all three astrophysical applications. | arxiv:astro-ph/0609112 |
we investigate the chemical equilibration of the parton distributions in collisions of two heavy nuclei. we use initial conditions obtained from a self - screened parton cascade calculation and, for comparison, from the hijing model. we consider a one - dimensional, as well as a three - dimensional expansion of the parton plasma and find that the onset of the transverse expansion impedes the chemical equilibration. at energies of 100 gev / nucleon, the results for one - dimensional and three - dimensional expansion are quite similar except at large values of the transverse radius. at energies of several tev / nucleon, the plasma initially approaches chemical equilibrium, but then is driven away from it, when the transverse velocity gradients develop. we find that the total parton multiplicity density remains essentially unaffected by the flow, but the individual concentrations of quarks, antiquarks, and gluons are sensitive to the transverse flow. the consequences of the flow are also discernible in the transverse momenta of the partons and in the lepton pair spectra, where the flow causes a violation of the so - called $ m _ t $ scaling. | arxiv:nucl-th/9611041 |
are considered a two - phase material composed of rock or mineral particles and water. structures may be fixed in place in the seabed — as is the case for piers, jetties and fixed - bottom wind turbines — or may comprise a floating structure that remains roughly fixed relative to its geotechnical anchor point. undersea mooring of human - engineered floating structures include a large number of offshore oil and gas platforms and, since 2008, a few floating wind turbines. two common types of engineered design for anchoring floating structures include tension - leg and catenary loose mooring systems. = = observational method = = first proposed by karl terzaghi and later discussed in a paper by ralph b. peck, the observational method is a managed process of construction control, monitoring, and review, which enables modifications to be incorporated during and after construction. the method aims to achieve a greater overall economy without compromising safety by creating designs based on the most probable conditions rather than the most unfavorable. using the observational method, gaps in available information are filled by measurements and investigation, which aid in assessing the behavior of the structure during construction, which in turn can be modified per the findings. the method was described by peck as " learn - as - you - go ". the observational method may be described as follows : general exploration sufficient to establish the rough nature, pattern, and properties of deposits. assessment of the most probable conditions and the most unfavorable conceivable deviations. creating the design based on a working hypothesis of behavior anticipated under the most probable conditions. selection of quantities to be observed as construction proceeds and calculating their anticipated values based on the working hypothesis under the most unfavorable conditions. selection, in advance, of a course of action or design modification for every foreseeable significant deviation of the observational findings from those predicted. measurement of quantities and evaluation of actual conditions. design modification per actual conditions the observational method is suitable for construction that has already begun when an unexpected development occurs or when a failure or accident looms or has already happened. it is unsuitable for projects whose design cannot be altered during construction. = = see also = = = = notes = = = = references = = bates and jackson, 1980, glossary of geology : american geological institute. krynine and judd, 1957, principles of engineering geology and geotechnics : mcgraw - hill, new york. pierfranco ventura, fondazioni, modellazioni : verifiche statiche e sis | https://en.wikipedia.org/wiki/Geotechnical_engineering |
classical lattice gas automata effectively simulate physical processes such as diffusion and fluid flow ( in certain parameter regimes ) despite their simplicity at the microscale. motivated by current interest in quantum computation we recently defined quantum lattice gas automata ; in this paper we initiate a project to analyze which physical processes these models can effectively simulate. studying the single particle sector of a one dimensional quantum lattice gas we find discrete analogues of plane waves and wave packets, and then investigate their behaviour in the presence of inhomogeneous potentials. | arxiv:quant-ph/9611005 |
in explainable ai ( xai ), counterfactual explanations ( ces ) are a well - studied method to communicate feature relevance through contrastive reasoning of " what if " to explain ai models ' predictions. however, they only focus on important ( i. e., relevant ) features and largely disregard less important ( i. e., irrelevant ) ones. such irrelevant features can be crucial in many applications, especially when users need to ensure that an ai model ' s decisions are not affected or biased against specific attributes such as gender, race, religion, or political affiliation. to address this gap, the concept of alterfactual explanations ( aes ) has been proposed. aes explore an alternative reality of " no matter what ", where irrelevant features are substituted with alternative features ( e. g., " republicans " - > " democrats " ) within the same attribute ( e. g., " politics " ) while maintaining a similar prediction output. this serves to validate whether ai model predictions are influenced by the specified attributes. despite the promise of aes, there is a lack of computational approaches to systematically generate them, particularly in the text domain, where creating aes for ai text classifiers presents unique challenges. this paper addresses this challenge by formulating ae generation as an optimization problem and introducing momatterxai, a novel algorithm that generates aes for text classification tasks. our approach achieves high fidelity of up to 95 % while preserving context similarity of over 90 % across multiple models and datasets. a human study further validates the effectiveness of aes in explaining ai text classifiers to end users. all codes will be publicly available. | arxiv:2408.10528 |
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