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dynamical properties of 2d antiferromagnets with hole doping are investigated to see the effects of short range local magnetic order on the temperature dependence of the dynamical magnetic susceptibility. we show the pseudo - gap like behavior of the temperature dependence of the nmr relaxation rate. we also discuss implications of the results in relations to the observed spin gap like behavior of low - doped copper oxide high - $ t _ c $ superconductors. | arxiv:cond-mat/9712104 |
we investigate one - dimensional driven diffusive systems where particles may also be created and annihilated in the bulk with sufficiently small rate. in an open geometry, i. e., coupled to particle reservoirs at the two ends, these systems can exhibit ergodicity breaking in the thermodynamic limit. the triggering mechanism is the random motion of a shock in an effective potential. based on this physical picture we provide a simple condition for the existence of a non - ergodic phase in the phase diagram of such systems. in the thermodynamic limit this phase exhibits two or more stationary states. however, for finite systems transitions between these states are possible. it is shown that the mean lifetime of such a metastable state is exponentially large in system - size. as an example the asep with the a0a - - aaa reaction kinetics is analyzed in detail. we present a detailed discussion of the phase diagram of this particular model which indeed exhibits a phase with broken ergodicity. we measure the lifetime of the metastable states with a monte carlo simulation in order to confirm our analytical findings. | arxiv:cond-mat/0511089 |
multimodal large language models ( mllms ) have demonstrated notable capabilities in general visual understanding and reasoning tasks. however, their deployment is hindered by substantial computational costs in both training and inference, limiting accessibility to the broader research and user communities. a straightforward solution is to leverage smaller pre - trained vision and language models, which inevitably cause significant performance drops. in this paper, we demonstrate the possibility of training a smaller but better mllm with high - quality training data. specifically, we introduce bunny, a family of lightweight mllms with flexible vision and language backbones for efficient multimodal learning from selected training data. experiments show that our bunny - 4b / 8b outperforms the state - of - the - art large mllms on multiple benchmarks. we expect that this work can provide the community with a clean and flexible open - source tool for further research and development. the code, models, and data can be found in https : / / github. com / baai - dcai / bunny. | arxiv:2402.11530 |
the origin of the variability in accretion disks of active galactic nuclei ( agn ) is still unknown, but its behavior can be characterized by modeling the time series of optical wavelength fluxes coming from the accretion disks with damped random walk ( drw ) being the most popular model for this purpose. the drw is modeled by a characteristic fluctuation amplitude and damping timescale { \ tau }, with the latter being potentially related to the mass and accretion rate onto the massive black hole. the estimation of { \ tau } is challenging, with commonly used methods such as the maximum likelihood ( ml ) and the least square error ( lse ) resulting in biased estimators. this problem arises most commonly for three reasons : i ) the light curve has been observed with additive noise ; ii ) some cadence scheme ; iii ) when the autocorrelation parameter is close to one. the latter is called the unit root problem. in order to improve these parameter estimation procedures for estimating { \ tau }, we developed a simulation - extrapolation ( simex ) methodology in the context of time series analysis. we consider both the standard class of autoregressive processes observed at regular intervals and a recently developed class of irregularly autoregressive processes ( iar ). the performance of the simex estimation method was evaluated under conditions of near - unit - root behavior and additive noise through extensive monte carlo simulations. monte carlo experiments confirm that the simex approach outperforms mle and lse methods, offering a reduction in estimation bias ranging from 30 % to 90 %. real - data applications further validate the methodology, yielding better model fits and lower mean squared errors ( mse ). the more accurate estimation of the damping timescale parameter can help to better understand the currently tentative links between drw and physical parameters in agn. | arxiv:2501.15586 |
nanson ' s and baldwin ' s voting rules select a winner by successively eliminating candidates with low borda scores. we show that these rules have a number of desirable computational properties. in particular, with unweighted votes, it is np - hard to manipulate either rule with one manipulator, whilst with weighted votes, it is np - hard to manipulate either rule with a small number of candidates and a coalition of manipulators. as only a couple of other voting rules are known to be np - hard to manipulate with a single manipulator, nanson ' s and baldwin ' s rules appear to be particularly resistant to manipulation from a theoretical perspective. we also propose a number of approximation methods for manipulating these two rules. experiments demonstrate that both rules are often difficult to manipulate in practice. these results suggest that elimination style voting rules deserve further study. | arxiv:1106.5312 |
spatio - temporal preferences and encounter statistics provide realistic measures to understand mobile user ' s behavioral preferences and transfer opportunities in delay tolerant networks ( dtns ). the time dependent behavior and periodic reappearances at specific locations can approximate future online presence while encounter statistics can aid to forward the routing decisions. it is theoretically shown that such characteristics heavily affect the performance of routing protocols. therefore, mobility models demonstrating such characteristics are also expected to show identical routing performance. however, we argue models despite capturing these properties deviate from their expected routing performance. we use realistic traces to validate this observation on two mobility models. our empirical results for epidemic routing show those models ' largely differ ( delay 67 % & reachability 79 % ) from the observed values. this in - turn call for two important activities : ( i ) analogous to routing, explore structural properties on a global scale ( ii ) design new mobility models that capture them. | arxiv:1007.0960 |
strategically combining four structured domains creates the first ever three - way topological energy - splitter ; remarkably, this is only possible using a square, or rectangular, lattice, and not the graphene - like structures more commonly used in valleytronics. to achieve this effect, the two mirror symmetries, present within all fully - symmetric square structures, are broken ; this leads to two nondistinct interfaces upon which valley - hall states reside. these interfaces are related to each other via the time - reversal operator and it is this subtlety that allows us to ignite the third outgoing lead. the geometrical construction of our structured medium allows for the three - way splitter to be adiabatically converted into a wave steerer around sharp bends. due to the tunability of the energies directionality by geometry, our results have far - reaching implications for applications such as beam - splitters, switches and filters across wave physics. | arxiv:1901.01937 |
the aim of the project is to improve our knowledge on the multiplicity of planet - host stars at wide physical separations. we cross - matched approximately 6200 square degree area of the southern sky imaged by the visible infrared survey telescope for astronomy ( vista ) hemisphere survey ( vhs ) with the two micron all sky survey ( 2mass ) to look for wide common proper motion companions to known planet - host stars. we complemented our astrometric search with photometric criteria. we confirmed spectroscopically the co - moving nature of seven sources out of 16 companion candidates and discarded eight, while the remaining one stays as a candidate. among these new wide companions to planet - host stars, we discovered a t4. 5 dwarf companion at 6. 3 arcmin ( ~ 9000 au ) from hip70849, a k7v star which hosts a 9 jupiter mass planet with an eccentric orbit. we also report two new stellar m dwarf companions to one g and one metal - rich k star. we infer stellar and substellar binary frequencies for our complete sample of 37 targets of 5. 4 + / - 3. 8 % and 2. 7 + / - 2. 7 % ( 1 sigma confidence level ), respectively, for projected physical separations larger than ~ 60 - 160 au assuming the range of distances of planet - host stars ( 24 - 75 pc ). these values are comparable to the frequencies of non planet - host stars. we find that the period - eccentricity trend holds with a lack of multiple systems with planets at large eccentricities ( e > 0. 2 ) for periods less than 40 days. however, the lack of planets more massive than 2. 5 jupiter masses and short periods ( < 40 days ) orbiting single stars is not so obvious due to recent discoveries by ground - based transit surveys and space missions. | arxiv:1408.1208 |
in this paper, how to successfully and efficiently condition a target population of agents towards consensus is discussed. to overcome the curse of dimensionality, the mean field formulation of the consensus control problem is considered. although such formulation is designed to be independent of the number of agents, it is feasible to solve only for moderate intrinsic dimensions of the agents space. for this reason, the solution is approached by means of a boltzmann procedure, i. e. quasi - invariant limit of controlled binary interactions as approximation of the mean field pde. the need for an efficient solver for the binary interaction control problem motivates the use of a supervised learning approach to encode a binary feedback map to be sampled at a very high rate. a gradient augmented feedforward neural network for the value function of the binary control problem is considered and compared with direct approximation of the feedback law. | arxiv:2207.09171 |
the occurrence of chaos for test particles moving around a slowly rotating black hole with a dipolar halo is studied using poincar \ ' e sections. we find a novel effect, particles with angular momentum opposite to the black hole rotation have larger chaotic regions in phase space than particles initially moving in the same direction. | arxiv:gr-qc/9712008 |
we show that holography poses non - trivial restrictions on various couplings of an interacting field. for a vector boson in the ads reissner - nordstrom background, the dual boundary theory is pathological unless its electromagnetic and gravitational multipole moments are constrained. among others, a generic dipole moment afflicts the dual cft with superluminal modes, whose remedy bounds the gyromagnetic ratio in a range around the natural value g = 2. we discuss the cft implications of our results, and argue that similar considerations can shed light on how massive higher - spin fields couple to electromagnetism and gravity. | arxiv:1212.6265 |
$ | \ mathbb p | $. | arxiv:1912.03327 |
the spin seebeck effect ( sse ) refers to the generation of a spin current as a result of a temperature gradient in a magnetic material, which can be detected electrically via the inverse spin hall effect in a metallic contact. since the discovery of sse in 2008, intensive studies on sse have been conducted to elucidate its origin. sses appear in a wide range of magnetic materials including ferro -, ferri -, and antiferro - magnets and also paramagnets with classical or quantum spin fluctuation. sse voltage reflects fundamental properties of a magnet, such as elementary excitation, static magnetic order, spin correlation, and spin transport. in this article, we review recent progress on sses in various systems, with particular emphasis on its emerging role as a probe of these magnetic properties in solids. we also briefly discuss the recently - discovered nuclear sse. | arxiv:2205.10509 |
each investigation consists of several major problems that the teacher and students explore in class. applications / connections / extensions problem sets are included for each investigation to help students practice, apply, connect, and extend essential understandings. while engaged in collaborative problem - solving and classroom discourse about mathematics, students are explicitly encouraged to reflect on their use of what the nctm standards once called mathematical processes and now refer to as mathematical practices — making sense of problems and solving them, reasoning abstractly and quantitatively, constructing arguments and critiquing the reasoning of others, modeling with mathematics, using mathematical tools strategically, seeking and using structure, expressing regularity in repeated reasoning, and communicating ideas and results with precision. = = implementation challenges = = the introduction of new curriculum content, instructional materials, and teaching methods is challenging in k – 12 education. when the proposed changes contrast with long - standing traditional practice, it is common to hear concerns from parents, teachers, and other professionals, as well as from students who have been successful and comfortable in traditional classrooms. in recognition of this innovation challenge, the national science foundation complemented its investment in new curriculum materials with substantial investments in professional development for teachers. by funding state and urban systemic initiatives, local systemic change projects, and math - science partnership programs, as well as national centers for standards - based school mathematics curriculum dissemination and implementation, the nsf provided powerful support for the adoption and implementation of the various reform mathematics curricula developed during the standards era. in addition to those programs, for nearly twenty years, cmp has sponsored summer getting to know cmp institutes, workshops for leaders of cmp implementation, and an annual user ' s conference for the sharing of implementation experiences and insights, all on the campus of michigan state university. the whole reform curriculum effort has greatly enhanced the field ' s understanding of what works in that important and challenging process — the clearest message being that significant lasting change takes time, persistent effort, and coordination of work by teachers at all levels in a system. = = research findings = = connected mathematics has become the most widely used of the middle school curriculum materials developed to implement the nctm standards. the effects of its use have been described in expository journal articles and evaluated in mathematics education research projects. many of the research studies are master ' s or doctoral dissertation research projects focused on specific aspects of the cmp classroom experience and student learning. but there have also been a number of large - scale independent evaluations of the results of the program. in the large - scale controlled research studies the | https://en.wikipedia.org/wiki/Connected_Mathematics |
the bethe - salpeter equation is used to comprehensively study mesons with j = 0, 1 and equal - mass constituents for quark masses from the chiral limit to the b - quark mass. the survey contains masses of the ground states in all corresponding j ^ { pc } channels including those with " exotic " quantum numbers. the emphasis is put on each particular state ' s sensitivity to the low - and intermediate - momentum, i. e., long - range part of the strong interaction. | arxiv:0909.4016 |
the infeasible parts of the objective space in difficult many - objective optimization problems cause trouble for evolutionary algorithms. this paper proposes a reference vector based algorithm which uses two interacting engines to adapt the reference vectors and to evolve the population towards the true pareto front ( pf ) s. t. the reference vectors are always evenly distributed within the current pf to provide appropriate guidance for selection. the current pf is tracked by maintaining an archive of undominated individuals, and adaptation of reference vectors is conducted with the help of another archive that contains layers of reference vectors corresponding to different density. experimental results show the expected characteristics and competitive performance of the proposed algorithm teea. | arxiv:1904.06302 |
we present here a detailed analysis on the effects of charge on the anisotropic strange star candidates by considering a spherically symmetric interior spacetime metric. to obtain exact solution of the einstein - maxwell field equations we have considered the anisotropic strange quark matter ( sqm ) distribution governed by the simplified mit bag equation of state ( eos ), $ p = \ frac { 1 } { 3 } \ left ( { \ rho } - 4 \, b \ right ) $, where $ b $ is the bag constant and the distribution of the electrical charge is given as $ q ( r ) = q \ left ( { r } / { r } \ right ) ^ 3 = \ alpha { r ^ 3 } $, where $ \ alpha $ is a constant. to this end, to calculate different constants we have described the exterior spacetime by the reissner - nordstr { \ " o } m metric. by using the values of the observed mass for the different strange star candidates we have maximized anisotropic stress at the surface to predict the exact values of the radius for the different values of $ \ alpha $ and a specific value of the bag constant. further, we perform different tests to study the physical validity and the stability of the proposed stellar model. we found accumulation of the electric charge distribution is maximum at the surface having electric charge of the order $ { { 10 } ^ { 20 } } ~ c $ and electric field of the order $ { 10 } ^ { 21 - 22 } ~ v / cm $. to study the different physical parameters and the effects of charge on the anisotropic stellar system we have presented our analysis graphically and in the tabular format by considering $ lmc ~ x - 4 $ as the representative of the strange star candidates. | arxiv:1802.01332 |
a modelling language is described which is suitable for the correlation of information when the underlying functional model of the system is incomplete or uncertain and the temporal dependencies are imprecise. an efficient and incremental implementation is outlined which depends on cost functions satisfying certain criteria. possibilistic logic and probability theory ( as it is used in the applications targetted ) satisfy these criteria. | arxiv:1302.1521 |
from the present limits on the masses and mixings of fourth family quarks, they are expected to have mass larger than the top quark and allow a large range of mixing of the third family. they could also have different dynamics than the quarks of three families of the standard model. the single production of the fourth family up type quark t ' has been studied via anomalous production process pp - > t ' vx ( where v = g, z, \ gamma ) at the lhc with the center of mass energy of 7 and 14 tev. the signatures of such process are discussed within both the sm decay modes and anomalous decay modes of t ' quarks. the sensitivity to anomalous coupling kappa / lambda = 0. 004 tev ^ ( - 1 ) can be reached at sqrt ( s ) = 14 tev and l _ ( int ) = 100 pb ^ ( - 1 ). | arxiv:1106.6059 |
the role of lattice distortion in the charge, orbital and spin ordering in half doped manganites has been investigated. for fixed magnetic ordering, we show that the cooperative lattice distortion stabilize the experimentally observed ordering even when the strong on - site electronic correlation is taken into account. furthermore, without invoking the magnetic interactions, the cooperative lattice distortion alone may lead to the correct charge and orbital ordering including the charge stacking effect, and the magnetic ordering can be the consequence of such a charge and orbital ordering. we propose that the cooperative nature of the lattice distortion is essential to understand the complicated charge, orbital and spin ordering observed in doped manganites. | arxiv:cond-mat/0204095 |
the proton is formulated as a relativistic system of three constituent quarks interacting via a zero - range two - body force in the null - plane. the covariance of the null - plane faddeev - like equation under kinematical front - form boosts is discussed. a simplified three - boson model of the nucleon wave - function is obtained numerically. the proton electric form - factor reproduces the experimental data for low momentum transfers and qualitatively describes the asymptotic region. | arxiv:hep-ph/9806507 |
dialogue systems for hotel and tourist information have typically simplified the richness of the domain, focusing system utterances on only a few selected attributes such as price, location and type of rooms. however, much more content is typically available for hotels, often as many as 50 distinct instantiated attributes for an individual entity. new methods are needed to use this content to generate natural dialogues for hotel information, and in general for any domain with such rich complex content. we describe three experiments aimed at collecting data that can inform an nlg for hotels dialogues, and show, not surprisingly, that the sentences in the original written hotel descriptions provided on webpages for each hotel are stylistically not a very good match for conversational interaction. we quantify the stylistic features that characterize the differences between the original textual data and the collected dialogic data. we plan to use these in stylistic models for generation, and for scoring retrieved utterances for use in hotel dialogues | arxiv:1805.00551 |
we study a charged taub - nut spacetime solution in the dgp brane. we show that the reissner - nordstrom - taub - nut - de sitter solution of einstein - maxwell gravity solves the corresponding equations of motion, where the cosmological constant is related to the cross - over scale in the dgp model. following the approach by teitelboim in discussing the thermodynamics of de sitter spacetime and the proposal by wu et al. for a conserved charge associated to the nut parameter, we obtained the generalized smarr mass formula and the first law of thermodynamics of the spacetime. | arxiv:2212.03051 |
we present a high - performance n - body code for self - gravitating collisional systems accelerated with the aid of a new simd instruction set extension of the x86 architecture : advanced vector extensions ( avx ), an enhanced version of the streaming simd extensions ( sse ). with one processor core of intel core i7 - 2600 processor ( 8 mb cache and 3. 40 ghz ) based on sandy bridge micro - architecture, we implemented a fourth - order hermite scheme with individual timestep scheme ( makino and aarseth, 1992 ), and achieved the performance of 20 giga floating point number operations per second ( gflops ) for double - precision accuracy, which is two times and five times higher than that of the previously developed code implemented with the sse instructions ( nitadori et al., 2006b ), and that of a code implemented without any explicit use of simd instructions with the same processor core, respectively. we have parallelized the code by using so - called ninja scheme ( nitadori et al., 2006a ), and achieved 90 gflops for a system containing more than n = 8192 particles with 8 mpi processes on four cores. we expect to achieve about 10 tera flops ( tflops ) for a self - gravitating collisional system with n 105 on massively parallel systems with at most 800 cores with sandy bridge micro - architecture. this performance will be comparable to that of graphic processing unit ( gpu ) cluster systems, such as the one with about 200 tesla c1070 gpus ( spurzem et al., 2010 ). this paper offers an alternative to collisional n - body simulations with grapes and gpus. | arxiv:1104.2700 |
after having investigated the geodesic triangles and their angle sums in nil and $ sl \ times \ mathbb { r } $ geometries we consider the analogous problem in sol space that is one of the eight 3 - dimensional thurston geometries. we analyse the interior angle sums of geodesic triangles and we prove that it can be larger than, less than or equal to $ \ pi $. moreover, we determine the equations of sol isoptic surfaces of translation - like segments and as a special case of this we examine the sol translation - like thales sphere, which we call thaloid. we also discuss the behavior of this surface. in our work we will use the projective model of sol described by e. moln \ ' ar in \ cite { m97 }. | arxiv:2405.05266 |
the rapid progress in 3d scene understanding has come with growing demand for data ; however, collecting and annotating 3d scenes ( e. g. point clouds ) are notoriously hard. for example, the number of scenes ( e. g. indoor rooms ) that can be accessed and scanned might be limited ; even given sufficient data, acquiring 3d labels ( e. g. instance masks ) requires intensive human labor. in this paper, we explore data - efficient learning for 3d point cloud. as a first step towards this direction, we propose contrastive scene contexts, a 3d pre - training method that makes use of both point - level correspondences and spatial contexts in a scene. our method achieves state - of - the - art results on a suite of benchmarks where training data or labels are scarce. our study reveals that exhaustive labelling of 3d point clouds might be unnecessary ; and remarkably, on scannet, even using 0. 1 % of point labels, we still achieve 89 % ( instance segmentation ) and 96 % ( semantic segmentation ) of the baseline performance that uses full annotations. | arxiv:2012.09165 |
in [ lu6 ] lusztig defined a certain algebra $ h, $ which is a direct sum of various algebras $ h _ { \ mathfrak { o } }. $ we establish an explicit algebra isomorphism between each algebra $ h _ { \ mathfrak { o } } $ and some matrix algebra with coefficients in the tensor product of an ( affine or finite ) hecke algebra and a group algebra. we give an application. | arxiv:1708.01835 |
we extend some classical results - such as quillen ' s theorem a, the grothendieck construction, thomason ' s theorem and the characterisation of homotopically cofinal functors - from the homotopy theory of small categories to polynomial monads and their algebras. as an application we give a categorical proof of the dwyer - hess and turchin results concerning the explicit double delooping of spaces of long knots. | arxiv:1712.00904 |
this paper presents a novel hybrid control protocol for de - conflicting multiple vehicles with constraints on control inputs. we consider turning rate and linear speed constraints to represent fixed - wing or car - like vehicles. a set of state - feedback controllers along with a state - dependent switching logic are synthesized in a hybrid system to generate collision - free trajectories that converge to the desired destinations of the vehicles. the switching law is designed so that the safety can be guaranteed while no zeno behavior can occur. a novel temporary goal assignment technique is also designed to guarantee convergence. we analyze the individual modes for safety and the closed - loop hybrid system for convergence. the theoretical developments are demonstrated via simulation results. | arxiv:1806.07328 |
let s be a finitely generated standard multi - graded algebra over a noetherian local ring a. this paper first expresses mixed multiplicities of s in term of hilbert - samuel multiplicity that explained the mixed multiplicities s as the hilbert - samuel multiplicities for quotient modules of s. as an application, we get formulas for the mixed multiplicities of ideals that covers the main result of trung - verma 2007 [ tv ]. | arxiv:0902.1240 |
we consider a gaussian two - hop network where the source and the destination can communicate only via a relay node who is both an eavesdropper and a byzantine adversary. both the source and the destination nodes are allowed to transmit, and the relay receives a superposition of their transmitted signals. we propose a new coding scheme that satisfies two requirements simultaneously : the transmitted message must be kept secret from the relay node, and the destination must be able to detect any byzantine attack that the relay node might launch reliably and fast. the three main components of the scheme are the nested lattice code, the privacy amplification and the algebraic manipulation detection ( amd ) code. specifically, for the gaussian two - hop network, we show that lattice coding can successfully pair with amd codes enabling its first application to a noisy channel model. we prove, using this new coding scheme, that the probability that the byzantine attack goes undetected decreases exponentially fast with respect to the number of channel uses, while the loss in the secrecy rate, compared to the rate achievable when the relay is honest, can be made arbitrarily small. in addition, in contrast with prior work in gaussian channels, the notion of secrecy provided here is strong secrecy. | arxiv:1004.1423 |
magnetically - doped graphene systems are potential candidates for application in future spintronic devices. a key step is to understand the pairwise interactions between magnetic impurities embedded in graphene that are mediated by the graphene conduction electrons. a large number of studies have been undertaken to investigate the indirect exchange, or rkky, interactions in graphene. many of these studies report a decay rate faster than expected for a 2 - dimensional material and the absence of the usual distance dependent oscillations. in this review we summarize the techniques used to calculate the interaction and present the key results obtained to date. the effects of more detailed parameterisations of the magnetic impurities and graphene host are considered, as are results obtained from ab initio calculations. since the fast decay of the interaction presents an obstacle to spintronic applications, we focus in particular on the possibility of augmenting the interaction range by a number of methods including doping, spin precession and the application of strain. | arxiv:1301.1779 |
dusty plasma crystals have traditionally been observed and studied in radio frequency ( rf ) discharge plasmas and their formation in a dc glow discharge plasma remains experimentally challenging. we report the first ever observation of a stable dusty plasma coulomb crystal in the cathode sheath region of a dc glow discharge plasma. the observations are made in the dpex device where crystals of mono - disperse melamine formaldehyde grains are produced in the background of an argon plasma. the crystalline nature of the structure is confirmed through a host of measurements that includes the radial pair correlation function, voronoi diagram, delaunay triangulation, the structural order parameter, the dust temperature and the coulomb coupling parameter. the special features of the dpex device that permit such a crystal formation are delineated and some principal physical features of the crystal discussed. | arxiv:1811.05114 |
in this paper we provide some simple characterizations for the spherical harmonics coefficients of an isotropic random field on the sphere. the main result is a characterization of isotropic gaussian fields through independence of the coefficients of their development in spherical harmonics. | arxiv:math/0606709 |
we study how different frame annotations complement one another when learning continuous lexical semantics. we learn the representations from a tensorized skip - gram model that consistently encodes syntactic - semantic content better, with multiple 10 % gains over baselines. | arxiv:1706.09562 |
this comprehensive review examines electrical and seismic refraction methods, emphasizing their advanced applications in electrical resistivity tomography ( ert ) and seismic refraction tomography ( srt ). these techniques are crucial for understanding surface - subsurface crustal dynamics, offering critical insights into resistivity and velocity structures for geological and geohazard assessments. the review also explores the induced polarization ( ip ) and self - potential ( sp ) methods as complementary approaches. despite their effectiveness, ert and srt face challenges due to lithological heterogeneities, complex geological processes, and geophysical data uncertainties, necessitating multidisciplinary solutions such as methodological advancements and data integration strategies. recently, machine learning ( ml ) techniques have been increasingly applied to joint ert and srt analyses, optimizing nonlinear inversion processes and improving the characterization of complex subsurface lithologies. the case studies presented in this review evaluate how supervised and unsupervised ml techniques enhance ert and srt by improving data interpretation, refining inversion accuracy, automating lithological differentiation, and predicting seismic velocity from resistivity data. the findings underscore the importance of integrating traditional geophysical methods with advanced data - driven approaches to improve subsurface investigations. continued innovations in ert and srt methodologies, along with emerging computational tools and ml applications, will further enhance their effectiveness in geological, hydrological, environmental, and hazard assessments. | arxiv:2404.00813 |
modern processors such as armv8 and risc - v allow executions in which independent instructions within a process may be reordered. to cope with such phenomena, so called promising semantics have been developed, which permit threads to read values that have not yet been written. each promise is a speculative update that is later validated ( fulfilled ) by an actual write. promising semantics are operational, providing a pathway for developing proof calculi. in this paper, we develop an incorrectness - style logic, resulting in a framework for reasoning about state reachability. like incorrectness logic, our assertions are underapproximating, since the set of all valid promises are not known at the start of execution. our logic uses event structures as assertions to compactly represent the ordering among events such as promised and fulfilled writes. we prove soundness and completeness of our proof calculus and demonstrate its applicability by proving reachability properties of standard weak memory litmus tests. | arxiv:2211.16330 |
using the most recent measurements of the ultraviolet ( uv ) luminosity functions ( lfs ) and dust estimates of early galaxies, we derive updated dust - corrected star - formation rate functions ( sfrfs ) at z ~ 4 - 8, which we model to predict the evolution to higher redshifts, z > 8. we employ abundance matching techniques to calibrate a relation between galaxy star formation rate ( sfr ) and host halo mass m $ _ { h } $ by mapping the shape of the observed sfrfs at z ~ 4 - 8 to that of the halo mass function. the resulting scaling law remains roughly constant over this redshift range. we apply the average sfr - m $ _ { h } $ relation to reproduce the observed sfr functions at 4 < = z < = 8 and also derive the expected uv lfs at higher redshifts. at z ~ 9 and z ~ 10 these model lfs are in excellent agreement with current observed estimates. our predicted number densities and uv lfs at z > 10 indicate that jwst will be able to detect galaxies out to z ~ 15 with an extensive treasury sized program. we also derive the redshift evolution of the star formation rate density and associated reionization history by galaxies. models which integrate down to the current hudf12 / xdf detection limit ( m $ _ { uv } $ ~ - 17. 7 mag ) result in a sfrd that declines as ( 1 + z ) $ ^ { - 10. 4 \ pm0. 3 } $ at high redshift and fail to reproduce the observed cmb electron scattering optical depth, $ \ tau $ ~ 0. 066, to within 1 $ \ sigma $. on the other hand, we find that the inclusion of galaxies with sfrs well below the current detection limit ( m $ _ { uv } $ < - 5. 7 mag ) leads to a fully reionized universe by z ~ 6. 5 and an optical depth of $ \ tau $ ~ 0. 054, consistent with the recently derived planck value at the 1 $ \ sigma $ level. | arxiv:1507.00999 |
this paper is related to nonzero - sum stochastic differential games in the markovian framework. we show existence of a nash equilibrium point for the game when the drift is no longer bounded and only satisfies a linear growth condition. the main tool is the notion of backward stochastic differential equations which, in our case, are multidimensional with continuous coefficient and stochastic linear growth. | arxiv:1308.5882 |
human body communication ( hbc ) provides a low power communication medium for energy constrained wearable / implantable devices in and around the human body. this paper presents a broadband hbc transceiver implemented in 65nm cmos that achieves 6. 3pj / b energy efficiency at 30mbps with - 30db interference - tolerance. capacitive termination at the receiver end is used to achieve a wideband hbc channel, and time domain signal - interference separation ( td - sis ) using integrating ddr ( i - ddr ) receiver allows a tolerance of - 30 db signal to interference ratio ( sir ) with a ber < 10 - 3. the transceiver achieves 18x improvement in energy - efficiency compared to the state - of - the - art hbc transceivers while being simultaneously broadband ( carrier - less, low - energy ) and interference - robust. such order - of - magnitude improvement in energy - efficiency and private communication through the human body may enable applications like closed - loop neuromodulation, health - monitoring, secure authentication among many others. | arxiv:1804.06743 |
we report on a dedicated effort to identify and study metal - poor stars strongly enhanced in r - process elements ( [ r / fe ] > 1 dex ; hereafter r - ii stars ), the hamburg / eso r - process enhanced star survey ( heres ). moderate - resolution ( ~ 2a ) follow - up spectroscopy has been obtained for metal - poor giant candidates selected from the hamburg / eso objective - prism survey ( hes ) as well as the hk survey to identify sharp - lined stars with [ fe / h ] < - 2. 5dex. for several hundred confirmed metal - poor giants brighter than b ~ 16. 5mag ( most of them from the hes ), ` ` snapshot ' ' spectra ( r ~ 20, 000 ; s / n ~ 30 per pixel ) are being obtained with vlt / uves, with the main aim of finding the 2 - 3 % r - ii stars expected to be among them. these are studied in detail by means of higher resolution and higher s / n spectra. in this paper we describe a pilot study based on a set of 35 stars, including 23 from the hk survey, 8 from the hes, and 4 comparison stars. we discovered two new r - ii stars, cs29497 - 004 ( [ eu / fe ] = 1. 64 + / - 0. 22 ) and cs29491 - 069 ( [ eu / fe ] = 1. 08 + / - 0. 23 ). a first abundance analysis of cs29497 - 004 yields that its abundances of ba to dy are on average enhanced by 1. 5dex with respect to iron and the sun and match a scaled solar r - process pattern well, while th is underabundant relative to that pattern by 0. 3dex, which we attribute to radioactive decay. that is, cs29497 - 004 seems not to belong to the class of r - process enhanced stars displaying an ` ` actinide boost ' ', like cs31082 - 001 ( hill et al. 2002 ), or cs30306 - 132 ( honda et al. 2004b ). the abundance pattern agrees well with predictions of the phenomenological model of qian & wasserburg. | arxiv:astro-ph/0408389 |
we have grown a single crystal of la _ 2 - x _ sr _ x _ cuo _ 4 _ in which the sr concentration, x, continuously changes from 0. 24 to 0. 29 in the overdoped regime and obtained many pieces of single crystals with different x values by slicing the single crystal. from detailed measurements of the magnetic susceptibility, chi, of each piece, it has been found that the absolute value of chi at the measured lowest temperature 2 k, | chi _ 2k _ |, on field cooling rapidly decreases with increasing x as well as the superconducting ( sc ) transition temperature. as the value of | chi _ 2k _ | is regarded as corresponding to the sc volume fraction in a sample, it has been concluded that a phase separation into sc and normal - state regions occurs in a sample of la _ 2 - x _ sr _ x _ cuo _ 4 _ in the overdoped regime. | arxiv:cond-mat/0508084 |
recently, diluted magnetic semiconductors ( dms ) doped with a small concentration of magnetic impurities, especially dms doped with transition metal, inducing ferromagnetic dmss have attracted a great interest. using the monte carlo method within the ising model, we study the magnetic properties of doped mn ions in semi - conductor for different carrier ' s concentration. for the case of zn1 - xmnxo, the results of our calculations show the effect of carriers in understanding the existence and the control of the magnetic order. we give also the exact values of carriers ' concentration that should be adopted or avoided in order to get ferromagnetic phase with high curie temperature. | arxiv:1106.0500 |
we present coordinated coronal observations of the august 21, 2017 total solar eclipse with the airborne infrared spectrometer ( air - spec ) and the extreme - ultraviolet imaging spectrometer ( eis ). these instruments provide an unprecedented view of the solar corona in two disparate wavelength regimes, the near to mid infrared ( ir ) and the extreme ultraviolet ( euv ), opening new pathways for characterizing the complex coronal plasma environment. during totality, air - spec sampled coronal ir spectra near the equatorial west limb, detecting strong sources of mg viii, s xi, si ix, and si x in two passbands encompassing 1. 4 - 4 $ \ mu $ m. we apply emission measure ( em ) loci analysis to these ir emission lines to test their capacity as coronal temperature diagnostics. the density - sensitive fe xii 186. 9 \ r { a } / 192. 4 \ r { a } line pair supplies spatially resolved, line - of - sight electron densities, supporting the em loci analysis. from this, we find em loci intersections at temperatures of $ 10 ^ { 6. 13 } $ k at 30 arcsec from the limb and $ 10 ^ { 6. 21 } $ k at 100 arcsec. applying the same em loci analysis to 27 eis emission lines associated with seven ion species ( fe x - xiv, s x, and si x ) confirms these results, displaying strong evidence of isothermal plasma throughout the region. however, the ir em loci analysis suffers from moderate uncertainties. the likely sources include : poor signal, infrared contamination from a prominence, and photoexcitation by continuum radiation. regardless, we demonstrate that euv spectral data are valuable constraints to coronal infrared emission models, and will be powerful supplements for future ir solar observatories, particularly dkist. | arxiv:1901.10425 |
large language models ( llms ) excellently generate human - like text, but also raise concerns about misuse in fake news and academic dishonesty. decoding - based watermark, particularly the gumbelmax - trick - based watermark ( gm watermark ), is a standout solution for safeguarding machine - generated texts due to its notable detectability. however, gm watermark encounters a major challenge with generation diversity, always yielding identical outputs for the same prompt, negatively impacting generation diversity and user experience. to overcome this limitation, we propose a new type of gm watermark, the logits - addition watermark, and its three variants, specifically designed to enhance diversity. among these, the gumbelsoft watermark ( a softmax variant of the logits - addition watermark ) demonstrates superior performance in high diversity settings, with its auroc score outperforming those of the two alternative variants by 0. 1 to 0. 3 and surpassing other decoding - based watermarking methods by a minimum of 0. 1. | arxiv:2402.12948 |
in order to prevent detection and evade signature - based scanning methods, which are normally exploited by antivirus software, metamorphic viruses use several various obfuscation approaches. they transform their code in new instances as look entirely or partly different and contain dissimilar sequences of string, but their behavior and function remain unchanged. this obfuscation process allows them to stay away from the string based signature detection. in this research, we use a statistical technique to compare the similarity between two files infected by two morphed versions of a given metamorphic virus. our proposed solution based on static analysis and it uses the histogram of machine instructions frequency in various offspring of obfuscated viruses. we use euclidean histogram distance metric to compare a pair of portable executable ( pe ) files. the aim of this study is to show that for some particular obfuscation methods, the presented solution can be exploited to detect morphed varieties of a file. hence, it can be utilized by non - string based signature scanning to identify whether a file is a version of a metamorphic virus or not. | arxiv:1104.3228 |
amorphous organic semiconductors based on small molecules and polymers are used in many applications, most prominently organic light emitting diodes ( oleds ) and organic solar cells. impurities and charge traps are omnipresent in most currently available organic semiconductors and limit charge transport and thus device efficiency. the microscopic cause as well as the chemical nature of these traps are presently not well understood. using a multiscale model we characterize the influence of impurities on the density of states and charge transport in small - molecule amorphous organic semiconductors. we use the model to quantitatively describe the influence of water molecules and water - oxygen complexes on the electron and hole mobilities. these species are seen to impact the shape of the density of states and to act as explicit charge traps within the energy gap. our results show that trap states introduced by molecular oxygen can be deep enough to limit the electron mobility in widely used materials. | arxiv:1908.11854 |
we report on direct experimental certification of the quantum non - gaussian character of a photon - number resolving detector. the certification protocol is based on an adaptation of the existing quantum non - gaussianity criteria for quantum states to quantum measurements. in our approach, it suffices to probe the detector with a vacuum state and two different thermal states to test its quantum non - gaussianity. the certification is experimentally demonstrated for the detector formed by a spatially multiplexed array of ten single - photon avalanche photodiodes. we confirm the quantum non - gaussianity of povm elements $ \ hat { \ pi } _ m $ associated with the $ m $ - fold coincidence counts, up to $ m = 7 $. the experimental ability to certify from the first principles the quantum non - gaussian character of $ \ hat { \ pi } _ m $ is for large $ m $ limited by low probability of the measurement outcomes, especially for vacuum input state. we find that the injection of independent gaussian background noise into the detector can be helpful and may reduce the measurement time required for reliable confirmation of quantum non - gaussianity. in addition, we modified and experimentally verified the quantum non - gaussianity certification protocol employing a third thermal state instead of a vacuum to speed up the whole measurement. our findings demonstrate the existence of efficient tools for the practical characterization of fundamental non - classical properties and benchmarking of complex optical quantum detectors. | arxiv:2208.12521 |
recently, a significant carbon - 14 enhancement in the year 994 in tree rings has been found, suggesting an extremely large cosmic ray flux event during a short period. the origin of this particular cosmic ray event has not been confirmed, but one possibility is that it is of solar origin. contemporary historical records of low latitude auroras can be used as supporting evidence for intense solar activity around that time. we investigated the previously reported as well as the new records found in contemporary observations from the 990s to determine potential auroras. records of potential red auroras in the late 992 and early 993 were found around the world, i. e. in the korean peninsula, germany, and the island of ireland, suggesting the occurrence of an intense geomagnetic storm driven by solar activity. | arxiv:1612.01106 |
cloud computing enables clients with limited computational power to economically outsource their large scale computations to a public cloud with huge computational power. cloud has the massive storage, computational power and software which can be used by clients for reducing their computational overhead and storage limitation. but in case of outsourcing, privacy of client ' s confidential data must be maintained. we have designed a protocol for outsourcing large scale eigen value problem to a malicious cloud which provides input / output data security, result verifiability and client ' s efficiency. as the direct computation method to find all eigenvectors is computationally expensive for large dimensionality, we have used power iterative method for finding the largest eigen value and the corresponding eigen vector of a matrix. for protecting the privacy, some transformations are applied to the input matrix to get encrypted matrix which is sent to the cloud and then decrypting the result that is returned from the cloud for getting the correct solution of eigen value problem. we have also proposed result verification mechanism for detecting robust cheating and provided theoretical analysis and experimental result that describes high - efficiency, correctness, security and robust cheating resistance of the proposed protocol. | arxiv:1609.01410 |
we present a scheme for a universal device which can be programmed by quantum states to approximate a chosen projective measurement to a given precision. our scheme can be viewed as an extension of the swap test to the instance where one state is supplied many times. as such, it has many potential applications given the variety of quantum information tasks which make use of the swap test. in particular, we show that our scheme is optimal for state discrimination under the one - sided error requirement, and optimally approximates any projective measurement. furthermore, we propose a practical implementation of our scheme with passive linear optics, which involves a simple interferometer composed only of balanced beam splitters. | arxiv:1805.02546 |
in this work, we present some recommendations on the evaluation of state - of - the - art generative models for constrained generation tasks. the progress on generative models has been rapid in recent years. these large - scale models have had three impacts : firstly, the fluency of generation in both language and vision modalities has rendered common average - case evaluation metrics much less useful in diagnosing system errors. secondly, the same substrate models now form the basis of a number of applications, driven both by the utility of their representations as well as phenomena such as in - context learning, which raise the abstraction level of interacting with such models. thirdly, the user expectations around these models and their feted public releases have made the technical challenge of out of domain generalization much less excusable in practice. subsequently, our evaluation methodologies haven ' t adapted to these changes. more concretely, while the associated utility and methods of interacting with generative models have expanded, a similar expansion has not been observed in their evaluation practices. in this paper, we argue that the scale of generative models could be exploited to raise the abstraction level at which evaluation itself is conducted and provide recommendations for the same. our recommendations are based on leveraging specifications as a powerful instrument to evaluate generation quality and are readily applicable to a variety of tasks. | arxiv:2212.00006 |
this is a collection of three written discussions of the paper " sequential quasi - monte carlo sampling " by m. gerber and n. chopin, following the presentation given before the royal statistical society in london on december 10th, 2014. | arxiv:1505.06473 |
recent developments in synthetic and supramolecular chemistry have created opportunities to design organic systems with tailored nanoscale structure for various technological applications. a key application area is the capture of light energy and its conversion into electrochemical or chemical forms for photovoltaic or sensing applications. in this work we consider cylindrical assemblies of chromophores that model structures produced by several supramolecular techniques. our study is especially guided by the versatile structures produced by virus - templated assembly. we use a multi - objective optimization framework to determine design principles and limitations in light harvesting performance for such assemblies, both in the presence and absence of disorder. we identify a fundamental trade - off in cylindrical assemblies that is encountered when attempting to maximize both efficiency of energy transfer and absorption bandwidth. we also rationalize the optimal design strategies and provide explanations for why various structures provide optimal performance. most importantly, we find that the optimal design strategies depend on the amount of energetic and structural disorder in the system. the aim of these studies is to develop a program of quantum - informed rational design for construction of organic assemblies that have the same degree of tailored nanoscale structure as biological photosynthetic light harvesting complexes, and also have the potential to reproduce their remarkable light harvesting performance. | arxiv:1210.2111 |
thermus is a package of c + + classes and functions allowing statistical - thermal model analyses of particle production in relativistic heavy - ion collisions to be performed within the root framework of analysis. calculations are possible within three statistical ensembles ; a grand - canonical treatment of the conserved charges b, s and q, a fully canonical treatment of the conserved charges, and a mixed - canonical ensemble combining a canonical treatment of strangeness with a grand - canonical treatment of baryon number and electric charge. thermus allows for the assignment of decay chains and detector efficiencies specific to each particle yield, which enables sensible fitting of model parameters to experimental data. | arxiv:hep-ph/0407174 |
in a recently proposed model of ` ` ghost condensation ' ', spatially homogeneous states may mix, via tunneling, with inhomogeneous states which are somewhat similar to bubbles in the theory of false vacuum decay, the corresponding bubble nucleation rate being exponentially sensitive to the ultraviolet completion of the model. the conservation of energy and charge requires that the energy density is negative and the field is strongly unstable in a part of the nucleated bubble. unlike in the theory of false vacuum decay, this region does not expand during subsequent real - time evolution. in the outer part, positive energy outgoing waves develop, which eventually form shocks. behind the outgoing waves and away from the bubble center, the background settles down to its original value. the outcome of the entire process is thus a microscopic region of negative energy and strong field - - ` ` hole in the ghost condensate ' ' - - plus a collection of outgoing waves ( particles of the ghost condensate field ) carrying away finite energy. | arxiv:hep-ph/0407081 |
logging is a development practice that plays an important role in the operations and monitoring of complex systems. developers place log statements in the source code and use log data to understand how the system behaves in production. unfortunately, anticipating where to log during development is challenging. previous studies show the feasibility of leveraging machine learning to recommend log placement despite the data imbalance since logging is a fraction of the overall code base. however, it remains unknown how those techniques apply to an industry setting, and little is known about the effect of imbalanced data and sampling techniques. in this paper, we study the log placement problem in the code base of adyen, a large - scale payment company. we analyze 34, 526 java files and 309, 527 methods that sum up + 2m sloc. we systematically measure the effectiveness of five models based on code metrics, explore the effect of sampling techniques, understand which features models consider to be relevant for the prediction, and evaluate whether we can exploit 388, 086 methods from 29 apache projects to learn where to log in an industry setting. our best performing model achieves 79 % of balanced accuracy, 81 % of precision, 60 % of recall. while sampling techniques improve recall, they penalize precision at a prohibitive cost. experiments with open - source data yield under - performing models over adyen ' s test set ; nevertheless, they are useful due to their low rate of false positives. our supporting scripts and tools are available to the community. | arxiv:2103.01755 |
we prove that the solutions of the cohomological equation for roth type interval exchange maps are h \ " older continuous provided that the datum is of class $ c ^ r $ with $ r > 1 $ and belongs to a finite - codimension linear subspace. | arxiv:1407.1776 |
contrary to the general consensus in the literature that friedmann - - lema \ ^ { i } tre - - robertson - - walker ( flrw ) geometries are of embedding class one ( i. e., \ embeddable in one higher dimensional pseudo - euclidean spaces ), we show that the most general $ k = 0 $ and $ k = - 1 $ flrw geometries are of embedding class two, and their corresponding pseudo - euclidean spaces have strictly one and two negative eigenvalues, respectively. these are particular results that follow from the new perspective on flrw embedding that we develop in this paper, namely that these embeddings are equivalent to unit - speed parametrized curves in two or three dimensions. a careful analysis of appropriate tensor fields then gives identical results and further explains why the class - two geometries remained hidden. however, the signatures of the embedding spaces, as well as the explicit embedding formulae, follow only from the curve picture. this also streamlines the comparatively difficult $ k = 0 $ class and provides new explicit embedding formulae for it and reproduces known embedding formulae for the $ k = 1, - 1 $ classes. embedding into anti - de sitter space in one higher dimension can likewise be done by constructing associated curves. in particular, we find that all $ k = 1 $ and mildly restricted subclasses of $ k = 0, - 1 $ geometries are embeddable in anti - de sitter space in one higher dimension. | arxiv:1702.00987 |
an investigation of the structural, magnetic, thermodynamic, and charge transport properties of non - centrosymmetric hexagonal scfege reveals it to be an anisotropic metal with a transition to a weak itinerant incommensurate helimagnetic state below $ t _ n = 36 $ k. neutron diffraction measurements discovered a temperature and field independent helical wavevector \ textbf { \ textit { k } } = ( 0 0 0. 193 ) with magnetic moments of 0. 53 $ \ mu _ { b } $ per formula unit confined to the { \ it ab } - plane. density functional theory calculations are consistent with these measurements and find several bands that cross the fermi level along the { \ it c } - axis with a nearly degenerate set of flat bands just above the fermi energy. the anisotropy found in the electrical transport is reflected in the calculated fermi surface, which consists of several warped flat sheets along the $ c $ - axis with two regions of significant nesting, one of which has a wavevector that closely matches that found in the neutron diffraction. the electronic structure calculations, along with a strong anomaly in the { \ it c } - axis conductivity at $ t _ n $, signal a fermi surface driven magnetic transition, similar to that found in spin density wave materials. magnetic fields applied in the { \ it ab } - plane result in a metamagnetic transition with a threshold field of $ \ approx $ 6. 7 t along with a sharp, strongly temperature dependent, discontinuity and a change in sign of the magnetoresistance for in - plane currents. thus, scfege is an ideal system to investigate the effect of in - plane magnetic fields on an easy - plane magnetic system, where the relative strength of the magnetic interactions and anisotropies determine the topology and magnetic structure. | arxiv:2009.14387 |
also bring to attention the opportunity cost of utilizing other forms of electricity. for example, the environmental protection agency estimates that coal kills 30, 000 people a year, as a result of its environmental impact, while 60 people died in the chernobyl disaster. a real world example of impact provided by proponents of nuclear energy is the 650, 000 ton increase in carbon emissions in the two months following the closure of the vermont yankee nuclear plant. = = see also = = atomic age lists of nuclear disasters and radioactive incidents nuclear power debate outline of nuclear technology radiology = = references = = = = external links = = nuclear energy institute – beneficial uses of radiation nuclear technology national isotope development center – u. s. government source of isotopes for basic and applied nuclear science and nuclear technology – production, research, development, distribution, and information | https://en.wikipedia.org/wiki/Nuclear_technology |
we present a combined experimental and theoretical study of the drag force acting on a high porosity aerogel immersed in liquid $ { } ^ 3 $ he and its effect on sound propagation. the drag force is characterized by the knudsen number, which is defined as the ratio of the quasiparticle mean free path to the radius of an aerogel strand. evidence of the knudsen - hydrodynamic crossover is clearly demonstrated by a drastic change in the temperature dependence of ultrasound attenuation in 98 % porosity aerogel. our theoretical analysis shows that the frictional sound damping caused by the drag force is governed by distinct laws in the two regimes, providing excellent agreement with the experimental observation. | arxiv:1201.5259 |
we construct type i string models with supersymmetry broken by compactification that are non - tachyonic and have exponentially small effective potential at one - loop. all open string moduli can be stabilized, while the closed string moduli remain massless at one - loop. the backgrounds of interest have rigid wilson lines by the use of stacked branes, and some models should have heterotic duals. we also present non - tachyonic backgrounds with positive potentials of runaway type at one - loop. this class of models could be used to test various swampland conjectures. | arxiv:1812.09714 |
we consider the problem of minimizing queue - length costs in a system with heterogenous parallel servers, operating in a many - server heavy - traffic regime with nondegenerate slowdown. this regime is distinct from the well - studied heavy traffic diffusion regimes, namely the ( single server ) conventional regime and the ( many - server ) halfin - whitt regime. it has the distinguishing property that waiting times and service times are of comparable magnitudes. we establish an asymptotic lower bound on the cost and devise a sequence of policies that asymptotically attain this bound. as in the conventional regime, the asymptotics can be described by means of a brownian control problem, the solution of which exhibits a state space collapse. | arxiv:1403.5399 |
we calculate the pyrocoefficient, static dielectric susceptibility profiles and its thickness dependence of ferroelectric thin films. also, the temperature dependences of above quantities have been calculated. for the calculations we use landau phenomenological theory, leading to lame equations. these equations subject to boundary conditions with different extrapolation length on the surfaces have been solved numerically. the divergency of pyroelectric coefficient and static dielectric susceptibility in the vicinity of thickness induced ferroelectric phase transition ( i. e. at $ l \ approx l _ c $ or $ % t \ approx t _ { cl } $ ) has been shown to be the most prominent size effect in ferroelectric thin films. | arxiv:cond-mat/0103083 |
we study the asymptotic behavior of the max $ \ kappa $ - cut on a family of sparse, inhomogeneous random graphs. in the large degree limit, the leading term is a variational problem, involving the ground state of a constrained inhomogeneous potts spin glass. we derive a parisi type formula for the free energy of this model, with possible constraints on the proportions, and derive the limiting ground state energy by a suitable zero temperature limit. | arxiv:1703.03455 |
we consider the unitary time evolution of continuous quantum mechanical systems confined to a cavity in contact with a finite bath of variable size. measures for markovianity for such finite system - bath configurations are developed in terms of hilbert - schmidt distances of time evolving wave packets. the relevant time scales are identified, which characterize pseudo - markovian transient behavior, boundary scattering induced non - markovian oscillations at intermediate times, and non - markovian rephasing events at long time scales. it is shown how these time scales can be controlled by tunable parameters such as the bath size and the strength of the system - bath coupling. | arxiv:1312.0396 |
maximal $ ( k + 1 ) $ - crossing - free graphs on a planar point set in convex position, that is, $ k $ - triangulations, have received attention in recent literature, with motivation coming from several interpretations of them. we introduce a new way of looking at $ k $ - triangulations, namely as complexes of star polygons. with this tool we give new, direct, proofs of the fundamental properties of $ k $ - triangulations, as well as some new results. this interpretation also opens - up new avenues of research, that we briefly explore in the last section. | arxiv:0706.3121 |
a chief technology officer ( cto ) ( also known as a chief technical officer or chief technologist ) is an officer tasked with managing technical operations of an organization. they oversee and supervise research and development and serve as a technical advisor to a higher executive such as a chief executive officer. a cto is very similar to a chief information officer ( cio ). ctos will make decisions for the overarching technology infrastructure that closely align with the organization ' s goals, while cios work alongside the organization ' s information technology ( " it " ) staff members to perform everyday operations. the attributes of the roles a cto holds vary from one company to another, mainly depending on their organizational structure. = = history = = after world war ii, large corporations established research laboratories at locations separate from their headquarters. the corporation ' s goals were to hire scientists and offer them facilities to conduct research on behalf of the company without the burdens of day - to - day office work. this is where the idea of a cto focusing on the overarching technology infrastructures originates. at that time, the director of the laboratory was a corporate vice president who did not participate in the company ' s corporate decisions. instead, the technical director was the individual responsible for attracting new scientists, to do research, and to develop products. in the 1980s, the role of these research directors changed substantially. since technology was becoming a fundamental part of the development for most products and services, companies needed an operational executive who could understand the product ' s technical side and provide advice on ways to improve and develop. this all led to the creation of the position of chief technology officer by large companies in the late 1980s with the growth of the information technology industry and computer ( internet ) companies. = = overview = = a cto " examines the short and long term needs of an organization, and utilizes capital to make investments designed to help the organization reach its objectives... [ the cto ] is the highest technology executive position within a company and leads the technology or engineering department ". the role became prominent with the ascent of the it industry, but has since become prevalent in technology - based industries of all types – including computer - based technologies ( such as game developer, e - commerce, and social networking service ) and other / non - computer - focused technology ( such as biotech / pharma, defense, and automotive ). in non - technical organizations as a corporate officer position, the cto typically reports directly to the chief information officer ( cio ) and | https://en.wikipedia.org/wiki/Chief_technology_officer |
we compute the one - loop quark - photon vertex and the quark magnetic moment in three different models with an infrared - modified gluon propagator, namely : the massive ( curci - ferrari - like ) model, the gribov - zwanziger model, and the refined gribov - zwanziger model. we show results for the $ f _ 2 $ form factor and analyze the role played by the mass parameters associated with the confined gluon in these models. using the framework of the constituent quark model, we further construct the observable proton magnetic moment including the effects of qcd interactions generated by the different confining models. our results show that there is no qualitative observable difference stemming from the presence of complex - conjugated poles. on the other hand, quantitative differences between the various confining models can be sizable, so that observable constraints would in principle be possible, provided one has sufficient information about the constituent quark mass and the qcd running coupling. | arxiv:2311.14178 |
we develop a compact perturbative series for accoustic wave propagation in a medium with a non gaussian stochastic speed of sound. we use martin - siggia and rose auxiliary field techniques to render the classical wave propagation problem into a " quantum " field theory one, and then frame this problem within so - called schwinger - keldysh of closed time - path ( ctp ) formalism. variation of the so - called two - particle irreducible ( 2pi ) effective action ( ea ), whose arguments are both the mean fields and the irreducible two point correlations, yields the schwinger - dyson and the bethe - salpeter equations. we work out the loop expansion of the 2pi ctp ea and show that, in the paradigmatic problem of overlapping spherical intrusions in an otherwise homogeneous medium, non gaussian corrections may be much larger than gaussian ones at the same order of loops | arxiv:1406.2647 |
banach ' s fixed point theorem for contraction maps has been widely used to analyze the convergence of iterative methods in non - convex problems. it is a common experience, however, that iterative maps fail to be globally contracting under the natural metric in their domain, making the applicability of banach ' s theorem limited. we explore how generally we can apply banach ' s fixed point theorem to establish the convergence of iterative methods when pairing it with carefully designed metrics. our first result is a strong converse of banach ' s theorem, showing that it is a universal analysis tool for establishing global convergence of iterative methods to unique fixed points, and for bounding their convergence rate. in other words, we show that, whenever an iterative map globally converges to a unique fixed point, there exists a metric under which the iterative map is contracting and which can be used to bound the number of iterations until convergence. we illustrate our approach in the widely used power method, providing a new way of bounding its convergence rate through contraction arguments. we next consider the computational complexity of banach ' s fixed point theorem. making the proof of our converse theorem constructive, we show that computing a fixed point whose existence is guaranteed by banach ' s fixed point theorem is cls - complete. we thus provide the first natural complete problem for the class cls, which was defined in [ daskalakis, papadimitriou 2011 ] to capture the complexity of problems such as p - matrix lcp, computing kkt - points, and finding mixed nash equilibria in congestion and network coordination games. | arxiv:1702.07339 |
arabian sea mid - tropospheric cyclones ( mtcs ), which are responsible for extreme rainfall events in western india, often coincide with monsoon low - pressure systems ( lps ) over the bay of bengal. however, the role of bay of bengal lpss in the formation of arabian sea mtcs remains unclear. this study utilizes the weather research and forecasting model ( wrf ) to investigate the atmospheric connection between the two basins. by introducing a balanced bogus vortex over the bay of bengal, cyclonic systems are induced over the arabian sea in the majority of ensemble members, exhibiting characteristics consistent with observations. as the bay of bengal vortex moves westward, the middle tropospheric trough deepens, horizontal wind shear increases, the low - level arabian sea stable inversion layer weakens, and the middle troposphere moisture content increases over western india and the northeast arabian sea. subsequently, mtc genesis occurs along the western edge of the trough within 2 - 4 days of model integration over the northeast arabian sea. vorticity budget analysis highlights the critical role of vorticity advection and tilting during the initial 24 hours of mtc genesis, while vortex stretching becomes the dominant vorticity source during rapid intensification. to further substantiate these findings, a mechanism denial experiment is conducted using a real - world instance of coexistent arabian sea mtc and bay of bengal lps, which was replicated in the model. in the experiment, conditions unfavorable for lps genesis are created by cooling and drying the bay of bengal. the results demonstrate that when the bay of bengal lps does not develop or intensify, the arabian sea mtc fails to form. this study presents compelling evidence for the significant influence of bay of bengal low - pressure systems on the formation of severe weather - inducing mtcs over the arabian sea and western india. | arxiv:2307.02607 |
to a complex projective structure $ \ sigma $ on a surface, thurston associates a locally convex pleated surface. we derive bounds on the geometry of both in terms of the norms $ \ | \ phi _ \ sigma \ | _ \ infty $ and $ \ | \ phi _ \ sigma \ | _ 2 $ of the quadratic differential $ \ phi _ \ sigma $ of $ \ sigma $ given by the schwarzian derivative of the associated locally univalent map. we show that these give a unifying approach that generalizes a number of important, well known results for convex cocompact hyperbolic structures on 3 - manifolds, including bounds on the lipschitz constant for the nearest - point retraction and the length of the bending lamination. we then use these bounds to begin a study of the weil - petersson gradient flow of renormalized volume on the space $ cc ( n ) $ of convex cocompact hyperbolic structures on a compact manifold $ n $ with incompressible boundary, leading to a proof of the conjecture that the renormalized volume has infimum given by one - half the simplicial volume of $ dn $, the double of $ n $. | arxiv:1704.06021 |
dissipation is mostly achieved by passive conduction / convection. means to achieve greater dissipation include heat sinks and fans for air cooling, and other forms of computer cooling such as water cooling. these techniques use convection, conduction, and radiation of heat energy. = = = noise = = = electronic noise is defined as unwanted disturbances superposed on a useful signal that tend to obscure its information content. noise is not the same as signal distortion caused by a circuit. noise is associated with all electronic circuits. noise may be electromagnetically or thermally generated, which can be decreased by lowering the operating temperature of the circuit. other types of noise, such as shot noise cannot be removed as they are due to limitations in physical properties. = = packaging methods = = many different methods of connecting components have been used over the years. for instance, early electronics often used point to point wiring with components attached to wooden breadboards to construct circuits. cordwood construction and wire wrap were other methods used. most modern day electronics now use printed circuit boards made of materials such as fr4, or the cheaper ( and less hard - wearing ) synthetic resin bonded paper ( srbp, also known as paxoline / paxolin ( trade marks ) and fr2 ) – characterised by its brown colour. health and environmental concerns associated with electronics assembly have gained increased attention in recent years, especially for products destined to go to european markets. electrical components are generally mounted in the following ways : through - hole ( sometimes referred to as ' pin - through - hole ' ) surface mount chassis mount rack mount lga / bga / pga socket = = industry = = the electronics industry consists of various sectors. the central driving force behind the entire electronics industry is the semiconductor industry sector, which has annual sales of over $ 481 billion as of 2018. the largest industry sector is e - commerce, which generated over $ 29 trillion in 2017. the most widely manufactured electronic device is the metal - oxide - semiconductor field - effect transistor ( mosfet ), with an estimated 13 sextillion mosfets having been manufactured between 1960 and 2018. in the 1960s, u. s. manufacturers were unable to compete with japanese companies such as sony and hitachi who could produce high - quality goods at lower prices. by the 1980s, however, u. s. manufacturers became the world leaders in semiconductor development and assembly. however, during the 1990s and subsequently, the industry shifted overwhelmingly to east asia ( a process begun with the initial movement of micro | https://en.wikipedia.org/wiki/Electronics |
in studies ranging from clinical medicine to policy research, complete data are usually available from a population $ \ mathscr { p } $, but the quantity of interest is often sought for a related but different population $ \ mathscr { q } $ which only has partial data. in this paper, we consider the setting that both outcome $ y $ and covariate $ { \ bf x } $ are available from $ \ mathscr { p } $ whereas only $ { \ bf x } $ is available from $ \ mathscr { q } $, under the so - called label shift assumption, i. e., the conditional distribution of $ { \ bf x } $ given $ y $ remains the same across the two populations. to estimate the parameter of interest in $ \ mathscr { q } $ via leveraging the information from $ \ mathscr { p } $, the following three ingredients are essential : ( a ) the common conditional distribution of $ { \ bf x } $ given $ y $, ( b ) the regression model of $ y $ given $ { \ bf x } $ in $ \ mathscr { p } $, and ( c ) the density ratio of $ y $ between the two populations. we propose an estimation procedure that only needs standard nonparametric technique to approximate the conditional expectations with respect to ( a ), while by no means needs an estimate or model for ( b ) or ( c ) ; i. e., doubly flexible to the possible model misspecifications of both ( b ) and ( c ). this is conceptually different from the well - known doubly robust estimation in that, double robustness allows at most one model to be misspecified whereas our proposal can allow both ( b ) and ( c ) to be misspecified. this is of particular interest in our setting because estimating ( c ) is difficult, if not impossible, by virtue of the absence of the $ y $ - data in $ \ mathscr { q } $. furthermore, even though the estimation of ( b ) is sometimes off - the - shelf, it can face curse of dimensionality or computational challenges. we develop the large sample theory for the proposed estimator, and examine its finite - sample performance through simulation studies as well as an application to the mimic - iii database. | arxiv:2307.04250 |
the nature of the dark matter of the universe is yet unknown and most likely is connected with new physics. the search for its composition is under way through direct and indirect detection. fundamental physical aspects such as energy threshold, geometry and location are taken into account to investigate proposed neutrino telescopes of km ^ 3 volume sensitivities to dark matter. these sensitivities are just sufficient to test a few wimp scenarios. telescopes of km ^ 3 volume, such as icecube, can definitely discover or exclude superheavy ( m > 10 ^ 10 gev ) strong interacting massive particles ( simpzillas ). smaller neutrino telescopes such as antares, amanda - ii and nestor can probe a large region of the simpzilla parameter space. | arxiv:hep-ph/0204301 |
the representation of numbers by tensor product states of composite quantum systems is examined. consideration is limited to k - ary representations of length l and arithmetic modulo k ^ { l }. an abstract representation on an l fold tensor product hilbert space h ^ { arith } of number states and operators for the basic arithmetic operations is described. unitary maps onto a physical parameter based tensor product space h ^ { phy } are defined and the relations between these two spaces and the dependence of algorithm dynamics on the unitary maps is discussed. the important condition of efficient implementation by physically realizable hamiltonians of the basic arithmetic operations is also discussed. | arxiv:quant-ph/0009124 |
a graph class $ \ mathcal { g } $ admits product structure if there exists a constant $ k $ such that every $ g \ in \ mathcal { g } $ is a subgraph of $ h \ boxtimes p $ for a path $ p $ and some graph $ h $ of treewidth $ k $. famously, the class of planar graphs, as well as many beyond - planar graph classes are known to admit product structure. however, we have only few tools to prove the absence of product structure, and hence know of only a few interesting examples of classes. motivated by the transition between product structure and no product structure, we investigate subclasses of intersection graphs in the plane ( e. g., disk intersection graphs ) and present necessary and sufficient conditions for these to admit product structure. specifically, for a set $ s \ subset \ mathbb { r } ^ 2 $ ( e. g., a disk ) and a real number $ \ alpha \ in [ 0, 1 ] $, we consider intersection graphs of $ \ alpha $ - free homothetic copies of $ s $. that is, each vertex $ v $ is a homothetic copy of $ s $ of which at least an $ \ alpha $ - portion is not covered by other vertices, and there is an edge between $ u $ and $ v $ if and only if $ u \ cap v \ neq \ emptyset $. for $ \ alpha = 1 $ we have contact graphs, which are in most cases planar, and hence admit product structure. for $ \ alpha = 0 $ we have ( among others ) all complete graphs, and hence no product structure. in general, there is a threshold value $ \ alpha ^ * ( s ) \ in [ 0, 1 ] $ such that $ \ alpha $ - free homothetic copies of $ s $ admit product structure for all $ \ alpha > \ alpha ^ * ( s ) $ and do not admit product structure for all $ \ alpha < \ alpha ^ * ( s ) $. we show for a large family of sets $ s $, including all triangles and all trapezoids, that it holds $ \ alpha ^ * ( s ) = 1 $, i. e., we have no product structure, except for the contact graphs ( when $ \ alpha = 1 $ ). for other sets $ s $, including regular $ n $ - gons for infinitely many values of $ n $, we | arxiv:2409.01732 |
wireless backhaul allows densification of mobile networks without incurring additional fiber deployment cost. this, in turn, leads to high spatial reuse, which is a significant tool to meet increasing wireless demand in 5g networks. integrated access and backhaul ( iab ), where access and backhaul network share the same standard wireless technology ( e. g. 5g new radio ( nr ) standard ), allows interoperability among different iab manufacturers and flexible operation between access and backhaul. this paper investigates joint resource allocation and relay selection in a multi - hop iab network to maximize geometric mean of ue rates. our study illustrates several advantages and features of iab. first, iab significantly improves ue rates compared to access only networks and can provide an important intermediate solution during incremental fiber deployment. second, iab networks with optimal mesh outperforms iab networks with rsrp based spanning tree both in terms of rate and latency. | arxiv:1804.00312 |
we consider the multi - broadcast problem in arbitrary connected radio networks consisting of $ n $ nodes. there are $ k $ designated source nodes for some fixed $ k \ in \ { 1, \ ldots, n \ } $, and each source node has a distinct piece of information that it wants to share with all nodes in the network. we set out to determine the shortest possible labels so that multi - broadcast can be solved deterministically in the labeled radio network by some universal deterministic distributed algorithm. | arxiv:2104.08644 |
consider a linear autonomous hamiltonian system with a time periodic bound state solution. in this paper we study the structural instability of this bound state ^ m relative to time almost periodic perturbations which are small, localized and hamiltonian. this class of perturbations includes those whose time dependence is periodic, but encompasses a large class of those with finite ( quasiperiodic ) or infinitely many non - commensurate frequencies. problems of the type considered arise in many areas of application including ionization physics and the propagation of light in optical fibers in the presence of defects. the mechanism of instability is radiation damping due to resonant coupling of the bound state to the continuum modes by the time - dependent perturbation. this results in a transfer of energy from the discrete modes to the continuum. the rate of decay of solutions is slow and hence the decaying bound states can be viewed as metastable. these results generalize those of a. soffer and m. i. weinstein, who treated localized time - periodic perturbations of a particular form. in the present work, new analytical issues need to be addressed in view of ( i ) the presence of infinitely many frequencies which may resonate with the continuum as well as ( ii ) the possible accumulation of such resonances in the continuous spectrum. the theory is applied to a general class of schr \ " odinger operators. | arxiv:nlin/0012021 |
two recent landmark experiments have performed gaussian boson sampling ( gbs ) with a non - programmable linear interferometer and threshold detectors on up to 144 output modes ( see refs. ~ \ onlinecite { zhong _ quantum _ 2020, zhong2021phase } ). here we give classical sampling algorithms with better total variation distance and kullback - leibler divergence than these experiments and a computational cost quadratic in the number of modes. our method samples from a distribution that approximates the single - mode and two - mode ideal marginals of the given gaussian boson sampler, which are calculated efficiently. one implementation sets the parameters of a boltzmann machine from the calculated marginals using a mean field solution. this is a 2nd order approximation, with the uniform and thermal approximations corresponding to the 0th and 1st order, respectively. the $ k $ th order approximation reproduces ursell functions ( also known as connected correlations ) up to order $ k $ with a cost exponential in $ k $ and high precision, while the experiment exhibits higher order ursell functions with lower precision. this methodology, like other polynomial approximations introduced previously, does not apply to random circuit sampling because the $ k $ th order approximation would simply result in the uniform distribution, in contrast to gbs. | arxiv:2109.11525 |
we establish an exact formula for the length of the shortest permutation containing all layered permutations of length $ n $, proving a conjecture of gray. | arxiv:1710.04240 |
we examine the effects of gas expulsion on initially sub - structured and out - of - equilibrium star clusters. we perform $ n $ - body simulations of the evolution of star clusters in a static background potential before removing that potential to model gas expulsion. we find that the initial star formation efficiency is not a good measure of the survivability of star clusters. this is because the stellar distribution can change significantly, causing a large change in the relative importance of the stellar and gas potentials. we find that the initial stellar distribution and velocity dispersion are far more important parameters than the initial star formation efficiency, and that clusters with very low star formation efficiencies can survive gas expulsion. we suggest that it is variations in cluster initial conditions rather than in their star formation efficiencies that cause some clusters to be destroyed while a few survive. | arxiv:1102.5360 |
incomplete utterance rewriting ( iur ) has recently become an essential task in nlp, aiming to complement the incomplete utterance with sufficient context information for comprehension. in this paper, we propose a novel method by directly extracting the coreference and omission relationship from the self - attention weight matrix of the transformer instead of word embeddings and edit the original text accordingly to generate the complete utterance. benefiting from the rich information in the self - attention weight matrix, our method achieved competitive results on public iur datasets. | arxiv:2202.12160 |
the proposed field - of - view of the kepler mission is at an ecliptic latitude of ~ 55 degrees, where the surface density of scattered kuiper belt objects ( kbos ) is a few percent that in the ecliptic plane. the rate of occultations of kepler target stars by scattered kbos with radii r > 10km is ~ 10 ^ - 6 to 10 ^ - 4 per star per year, where the uncertainty reflects the current ignorance of the thickness of the scattered kbo disk and the faint - end slope of their magnitude distribution. these occultation events will last only ~ 0. 1 % of the planned t _ exp = 15 minute integration time, and thus will appear as single data points that deviate by tiny amounts. however, given the target photometric accuracy of kepler, these deviations will nevertheless be highly significant, with typical signal - to - noise ratios of ~ 10. i estimate that 1 - 20 of the 10 ^ 5 main - sequence stars in kepler ' s field - of - view will exhibit detectable occultations during its four - year mission. for unresolved events, the signal - to - noise of individual occultations scales as t _ exp ^ { - 1 / 2 }, and the minimum detectable radius could be decreased by an order of magnitude to ~ 1 km by searching the individual 3 - second readouts for occultations. i propose a number of methods by which occultation events may be differentiated from systematic effects. kepler should measure or significantly constrain the frequency of highly - inclined, ~ 10 km - sized kbos. | arxiv:astro-ph/0404057 |
effective methodologies for evaluating recommender systems are critical, so that such systems can be compared in a sound manner. a commonly overlooked aspect of recommender system evaluation is the selection of the data splitting strategy. in this paper, we both show that there is no standard splitting strategy and that the selection of splitting strategy can have a strong impact on the ranking of recommender systems. in particular, we perform experiments comparing three common splitting strategies, examining their impact over seven state - of - the - art recommendation models for two datasets. our results demonstrate that the splitting strategy employed is an important confounding variable that can markedly alter the ranking of state - of - the - art systems, making much of the currently published literature non - comparable, even when the same dataset and metrics are used. | arxiv:2007.13237 |
dna language models, such as grover, dnabert2 and the nucleotide transformer, operate on dna sequences that inherently contain sequencing errors, mutations, and laboratory - induced noise, which may significantly impact model performance. despite the importance of this issue, the robustness of dna language models remains largely underexplored. in this paper, we comprehensivly investigate their robustness in dna classification by applying various adversarial attack strategies : the character ( nucleotide substitutions ), word ( codon modifications ), and sentence levels ( back - translation - based transformations ) to systematically analyze model vulnerabilities. our results demonstrate that dna language models are highly susceptible to adversarial attacks, leading to significant performance degradation. furthermore, we explore adversarial training method as a defense mechanism, which enhances both robustness and classification accuracy. this study highlights the limitations of dna language models and underscores the necessity of robustness in bioinformatics. | arxiv:2409.19788 |
dexterous multi - fingered hands can provide robots with the ability to flexibly perform a wide range of manipulation skills. however, many of the more complex behaviors are also notoriously difficult to control : performing in - hand object manipulation, executing finger gaits to move objects, and exhibiting precise fine motor skills such as writing, all require finely balancing contact forces, breaking and reestablishing contacts repeatedly, and maintaining control of unactuated objects. learning - based techniques provide the appealing possibility of acquiring these skills directly from data, but current learning approaches either require large amounts of data and produce task - specific policies, or they have not yet been shown to scale up to more complex and realistic tasks requiring fine motor skills. in this work, we demonstrate that our method of online planning with deep dynamics models ( pddm ) addresses both of these limitations ; we show that improvements in learned dynamics models, together with improvements in online model - predictive control, can indeed enable efficient and effective learning of flexible contact - rich dexterous manipulation skills - - and that too, on a 24 - dof anthropomorphic hand in the real world, using just 4 hours of purely real - world data to learn to simultaneously coordinate multiple free - floating objects. videos can be found at https : / / sites. google. com / view / pddm / | arxiv:1909.11652 |
the suitability of a transportable 3he - spin filter as temporary broadband polarizer for a time - of - flight neutron reflectometer is demonstrated. a simple two - wavelength method for characterisation of a 3he - spin filter is proposed, which can be applied even if the absolute transmittance of the 3he - spin filter cannot be accurately determined. we demonstrate the data treatment procedure for extracting the spin - up and spin - down neutron reflectivity from measurements obtained with a time dependent 3he polarization. the extraction of a very weak magnetic signal from reflectivity data, measured on the in - situ grown magnetic heterostructure fe1 nm / cu20 nm / sisubstrate in an externally applied magnetic field of 30mt is presented and compared to similar measurements on the growth stage cu20 nm / sisubstrate of the very same sample, which does not yet contain any magnetic material. | arxiv:1604.00816 |
group field theory has shown to be a promising framework to derive cosmological predictions from full quantum gravity. in this brief note, we revisit the background dynamics when interaction terms are taken into account and conclude that, although the bounce is clearly robust, providing a geometrical explanation for inflation seems to be very difficult. we consider possible improvements and modifications of the original scenario and derive several limits on the parameters of the model. | arxiv:2305.05438 |
dynamical systems can be modelled by partial differential equations and numerical computations are used everywhere in science and engineering. in this work, we investigate the performance of recurrent and convolutional deep neural network architectures to predict the surface waves. the system is governed by the saint - venant equations. we improve on the long - term prediction over previous methods while keeping the inference time at a fraction of numerical simulations. we also show that convolutional networks perform at least as well as recurrent networks in this task. finally, we assess the generalisation capability of each network by extrapolating in longer time - frames and in different physical settings. | arxiv:2002.08981 |
surprising enhancement of the magnetic moments recently observed in dilute co - mn alloy clusters is explained using ab initio electronic structure calculations. the calculated magnetic moments generally agree with the reported experimental data. an equation for calculating the magnetic moments of the co - mn alloy clusters has been derived to correct the deviations predicted by the rigid - band model and the virtual bound states approximation. a strategy is proposed to obtain the ground - state structures of the co - mn clusters and it was also put to the test of the experiment. | arxiv:0908.2358 |
the speed of convergence of the expectation maximization ( em ) algorithm for gaussian mixture model fitting is known to be dependent on the amount of overlap among the mixture components. in this paper, we study the impact of mixing coefficients on the convergence of em. we show that when the mixture components exhibit some overlap, the convergence of em becomes slower as the dynamic range among the mixing coefficients increases. we propose a deterministic anti - annealing algorithm, that significantly improves the speed of convergence of em for such mixtures with unbalanced mixing coefficients. the proposed algorithm is compared against other standard optimization techniques like bfgs, conjugate gradient, and the traditional em algorithm. finally, we propose a similar deterministic anti - annealing based algorithm for the dirichlet process mixture model and demonstrate its advantages over the conventional variational bayesian approach. | arxiv:1206.6427 |
recent years have witnessed the improving performance of chinese named entity recognition ( ner ) from proposing new frameworks or incorporating word lexicons. however, the inner composition of entity mentions in character - level chinese ner has been rarely studied. actually, most mentions of regular types have strong name regularity. for example, entities end with indicator words such as " company " or " bank " usually belong to organization. in this paper, we propose a simple but effective method for investigating the regularity of entity spans in chinese ner, dubbed as regularity - inspired recognition network ( ricon ). specifically, the proposed model consists of two branches : a regularity - aware module and a regularityagnostic module. the regularity - aware module captures the internal regularity of each span for better entity type prediction, while the regularity - agnostic module is employed to locate the boundary of entities and relieve the excessive attention to span regularity. an orthogonality space is further constructed to encourage two modules to extract different aspects of regularity features. to verify the effectiveness of our method, we conduct extensive experiments on three benchmark datasets and a practical medical dataset. the experimental results show that our ricon significantly outperforms previous state - of - the - art methods, including various lexicon - based methods. | arxiv:2204.05544 |
we show that type - ii weyl point formation in mnbi2 - xsbxte4 is more likely than in mnbi2te4 when x reaches 0. 5, as the alloy case does not suffer from the same degree of lattice parameter sensitivity as in mnbi2te4. to further substantiate the stability of type - ii weyl points in mnbi2 - xsbxte4, we demonstrate that among the three conditions of establishing a type - ii weyl point, two are robustly satisfied by the zone - folded dispersion of bi and te pz orbitals and spin - orbit coupling already available in mnbi2te4, and that the control over mnbi2 - xsbxte4 alloy composition provides a rational means to satisfy the third condition. the stability of type - ii weyl points in mnbi1. 5sb0. 5te4 is thus intimately associated with orbital interactions, providing a concrete foundation for future efforts in band engineering and the rational design of topological electronic structures. | arxiv:2103.12730 |
using resonantly excited photoluminescence along with photoluminescence excitation spectroscopies, we study the carrier excitation processes in cdte / znte and cdse / znse self - assembled quantum dots. photoluminescence excitation spectra of single cdte quantum dots reflect two major mechanisms for carrier excitation : the first, associated with the presence of sharp and intense lines in the spectrum, is a direct excited state? ground state transition. the second, associated with the appearance of up to four much broader excitation lines, is a lo phonon - assisted absorption directly into the quantum dot ground states. lo phonons with energies of both quantum dots and znte barrier material are identified in the photoluminescence excitation spectra. resonantly excited pl measurements for the dot ensemble as a function of excitation energy makes it possible to separate the contributions of these two mechanisms. we find that for cdte quantum dots the distribution of excited states coupled to the ground states reflects the energy distribution of the quantum dot emission, but shifted up in energy by 100 mev. this large splitting between excited and ground states in cdte quantum dots suggests strong spatial confinement. in contrast, the lo phonon - assisted absorption shows significant size selectivity. in the case of cdte dots the exciton - lo phonon coupling is strongly enhanced for smaller - sized dots which have higher emission energies. in contrast, for cdse quantum dots the exciton - lo phonon coupling is uniform over the ensemble? that is, the energy distribution determines the intensities of lo phonon replicas. we show that for cdte quantum dots after annealing, that is after an increase in the average dot size, the exciton - lo phonon interaction reflects the dot energy distribution, as observed for cdse quantum dots. | arxiv:cond-mat/0309410 |
in a previous paper, based on the black hole perturbation approach, we formulated a new analytical method for regularizing the self - force acting on a particle of small mass $ \ mu $ orbiting a schwarzschild black hole of mass $ m $, where $ \ mu \ ll m $. in our method, we divide the self - force into the $ \ tilde s $ - part and $ \ tilde r $ - part. all the singular behaviors are contained in the $ \ tilde s $ - part, and hence the $ \ tilde r $ - part is guaranteed to be regular. in this paper, focusing on the case of a scalar - charged particle for simplicity, we investigate the precision of both the regularized $ \ tilde s $ - part and the $ \ tilde r $ - part required for the construction of sufficiently accurate waveforms for almost circular inspiral orbits. for the regularized $ \ tilde s $ - part, we calculate it for circular orbits to 18 post - newtonian ( pn ) order and investigate the convergence of the post - newtonian expansion. we also study the convergence of the remaining $ \ tilde { r } $ - part in the spherical harmonic expansion. we find that a sufficiently accurate green function can be obtained by keeping the terms up to $ \ ell = 13 $. | arxiv:gr-qc/0410115 |
a fully relativistic analysis of gravitational lensing in teves is presented. by estimating the lensing masses for a set of six lenses from the castles database, and then comparing them to the stellar mass, the deficit between the two is obtained and analysed. considering a parametrised range for the teves function $ mu ( y ) $, which controls the strength of the modification to gravity, it is found that on galactic scales teves requires additional dark matter with the commonly used $ mu ( y ) $. a soft dependence of the results on the cosmological framework and the teves free parameters is discussed. for one particular form of $ mu ( y ) $, teves is found to require very little dark matter. this choice is however ruled out by rotation curve data. the inability to simultaneously fit lensing and rotation curves for a single form of $ mu ( y ) $ is a challenge to a " no dark matter " teves proposal. | arxiv:0901.3932 |
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