text
stringlengths 1
3.65k
| source
stringlengths 15
79
|
|---|---|
we discuss first - order phase transitions that are broadened by disorder, but still remain first order on the local mesoscopic level. using vortex - matter as our paradigm, we argue that phase transitions in general can be broadened by two different causes viz. due to a distribution of the phase transition point ( field or temperature ) from one region of the sample to another, or due to a distribution in the local magnetic field experienced by different regions of the sample. we show that in the second case there is an apparent " extrinsic " hysteresis even if the transition is locally second - order. we show that bulk measurements under isothermal conditions can be used to infer whether the broadened transition is first - order at the local ( mesoscopic ) level. keywords : vortex - matter, phase transitions, hysteresis
|
arxiv:cond-mat/0109310
|
we report sensitive detection of parametric resonances in a high - density sample of ultracold $ ^ { 87 } rb $ atoms confined to a far - off - resonance optical dipole trap. fluorescence imaging of the expanded ultracold atom cloud after a period of parametric excitation shows significant modification of the atomic spatial distribution and has high sensitivity compared with traditional measurements of parametrically - driven trap loss. using this approach, a significant shift of the parametric resonance frequency is observed, and attributed to the anharmonic shape of the dipole trap potential.
|
arxiv:0908.0263
|
social media has enabled people to circulate information in a timely fashion, thus motivating people to post messages seeking help during crisis situations. these messages can contribute to the situational awareness of emergency responders, who have a need for them to be categorised according to information types ( i. e. the type of aid services the messages are requesting ). we introduce a transformer - based multi - task learning ( mtl ) technique for classifying information types and estimating the priority of these messages. we evaluate the effectiveness of our approach with a variety of metrics by submitting runs to the trec incident streams ( is ) track : a research initiative specifically designed for disaster tweet classification and prioritisation. the results demonstrate that our approach achieves competitive performance in most metrics as compared to other participating runs. subsequently, we find that an ensemble approach combining disparate transformer encoders within our approach helps to improve the overall effectiveness to a significant extent, achieving state - of - the - art performance in almost every metric. we make the code publicly available so that our work can be reproduced and used as a baseline for the community for future work in this domain.
|
arxiv:2110.08010
|
new ccd photometry during 4 successive years from 2005 is presented for the eclipsing binary gw cep, together with reasonable explanations for the light and period variations. all historical light curves, obtained over a 30 - year interval, display striking light changes, and are best modeled by the simultaneous existence of a cool spot and a hot spot on the more massive cool component star. the facts that the system is magnetically active and that the hot spot has consistently existed on the inner hemisphere of the star indicate that the two spots are formed by ( 1 ) magnetic dynamo - related activity on the cool star and ( 2 ) mass transfer from the primary to the secondary component. based on 38 light - curve timings from the wilson - devinney code and all other minimum epochs, a period study of gw cep reveals that the orbital period has experienced a sinusoidal variation with a period and semi - amplitude of 32. 6 yrs and 0. 009 d, respectively. in principle, these may be produced either by a light - travel - time effect due to a third body or by an active magnetic cycle of at least one component star. because we failed to find any connection between luminosity variability and the period change, that change most likely arises from the existence of an unseen third companion star with a minimum mass of 0. 22 $ m _ \ odot $ gravitationally bound to the eclipsing pair.
|
arxiv:0911.4554
|
we present an extension of nagaoka ' s theorem in the su ( $ n $ ) generalization of the infinite - $ u $ hubbard model. it is shown that, when there is exactly one hole, the fully polarized states analogous to the ferromagnetic states in the su ( 2 ) hubbard model are ground states. for a restricted class of models satisfying the connectivity condition, these fully polarized states are the unique ground states up to the trivial degeneracy due to the su ( $ n $ ) symmetry. we also give examples of lattices in which the connectivity condition can be verified explicitly. the examples include the triangular, kagome, and hypercubic lattices in $ d ( \ ge 2 ) $ dimensions, among which the cases of $ d = 2 $ and 3 are experimentally realizable in ultracold atomic gases loaded into optical lattices.
|
arxiv:1210.4774
|
the wireless ad hoc networks are highly vulnerable to distributed denial of service ( ddos ) attacks because of its unique characteristics such as open network architecture, shared wireless medium and stringent resource constraints. these attacks throttle the tcp throughput heavily and reduce the quality of service ( qos ) to end systems gradually rather than refusing the clients from the services completely. in this paper, we discussed the ddos attacks and proposed a defense scheme to improve the performance of the ad hoc networks. our proposed defense mechanism uses the medium access control ( mac ) layer information to detect the attackers. the status values from mac layer that can be used for detection are frequency of receiving rts / cts packets, frequency of sensing a busy channel and the number of rts / data retransmissions. once the attackers are identified, all the packets from those nodes will be blocked. the network resources are made available to the legitimate users. we perform the simulation with network simulator ns2 and we proved that our proposed system improves the network performance.
|
arxiv:1106.1287
|
the angular dependence of magnetoresistance ( mr ) in antiferromagnetic half - heusler hoausn single crystals have been systematically studied. negative mr, as large as 99 %, is observed at 9 t, is not restricted to the specific configuration of applied magnetics fields and current, and can persist up to 20 k, much higher than the neel temperature ( tn 1. 9 k ). experiments and first - principles calculations suggest that the observed large negative mr is derived from a magnetic field that reconstructs the band structure and induces a weyl point, which changes the carrier concentration. taking into consideration that large negative mr has so far been rarely reported, especially in antiferromagnetic materials, it is anticipated that the present work not only offers a guideline for searching materials with large negative mr but also helps to further realize other exotic topological electronic states in a large class of antiferromagnetic half - heusler compounds.
|
arxiv:2411.14140
|
in this work, we develop a generic formalism for the study of tensor perturbations induced at second order by first - order vector metric perturbations, dubbing these induced tensor modes $ \ textit { vector - induced gravitational waves } $ ( vigws ). notably, considering an inflation - inspired power - law type magnetic field power spectrum of the form $ p _ b ( k ) \ propto k ^ { n _ \ mathrm { b } } $ ( where $ n _ { \ rm b } $ is the magnetic spectral index ), we show that the vigw signal is enhanced for stiff post - inflationary eos, with the maximum enhancement happening for $ w = 1 $. we explicitly demonstrate this contribution is dominant over the first - order magnetically - sourced gws. the vigw spectrum exhibits a maximum at around the scale crossing the cosmological horizon at the end of reheating, $ k _ \ mathrm { reh } $, with its present day peak amplitude scaling as $ \ omega _ { \ rm gw } ( k _ { \ rm reh }, \ eta _ 0 ) \ propto \ delta n _ { \ rm reh } \ times ( h _ { \ rm inf } / m _ { \ rm pl } ) ^ { 8 } $, where $ h _ { \ rm inf } $ is the hubble parameter at the end of inflation and $ \ delta n _ { \ rm reh } $ the duration of the post - inflationary era in $ e $ - folds. for $ w = 1 $ ( kination ) and $ n _ { \ rm b } > - 3 / 2 $, one further obtains a nearly $ n _ { \ rm b } $ - independent frequency scaling of the gw spectrum of the form $ \ omega _ { \ rm gw } ( f, \ eta _ 0 ) \ propto \ left ( \ frac { f } { f _ { \ rm reh } } \ right ) ^ { - 2. 8 } $ for $ f > f _ \ mathrm { reh } \ equiv k _ \ mathrm { reh } / ( 2 \ pi ) $. finally, we need to highlight that the vigw signal can be well within the detection bands of several next - generation interferometric gw missions at small scales. indicatively, for $ h _ { \ rm inf }
|
arxiv:2504.10477
|
jones introduced a method to produce unoriented links from elements of the thompson ' s group $ f $, and proved that any link can be produced by this construction. in this paper, we attempt to investigate the relations between conjugacy classes of the group $ f $ and the links being constructed. for each unoriented link $ l $, we find a sequence of elements of $ f $ from distinct conjugacy classes which yield $ l $ via jones ' s construction. we also show that a sequence of $ 2 $ - bridge links can be constructed from elements in the conjugacy class of $ x _ 0 $ ( resp. $ x _ 1 $ ).
|
arxiv:2504.01714
|
we provide a theory for scanning tunneling microscopy and spectroscopy using a spin - polarized tip. it it shown that the tunneling conductance can be partitioned into three separate contributions, a background conductance which is independent of the local spin, a dynamical conductance which is proportional to the local spin moment, and a conductance which is proportional to the noise spectrum of the local spin interactions. the presented theory is applicable to setups with magnetic tip and substrate in non - collinear arrangement, as well as for non - magnetic situations. the partitioning of the tunneling current suggests a possibility to extract the total spin moment of the local spin from the dynamical conductance. the dynamical conductance suggests a possibility to generate very high frequency spin - dependent ac currents and / or voltages. we also propose a measurement of the dynamical conductance that can be used to determine the character of the effective exchange interaction between individual spins in clusters. the third contribution to the tunneling current is associated with the spin - spin correlations induced by the exchange interaction between the local spin moment and the tunneling electrons. we demonstrate how this term can be used in the analysis of spin excitations recorded in conductance measurements. finally, we propose to use spin - polarized scanning tunneling microscopy for detailed studies of the spin excitation spectrum.
|
arxiv:0812.4956
|
intersection algorithms are very important in computation of geometrical problems. algorithms for a line intersection with linear or quadratic surfaces are quite efficient. however, algorithms for a line intersection with other surfaces are more complex and time consuming. in this case the object is usually closed into a simple bounding volume to speed up the cases when the given line cannot intersect the given object. in this paper new formulations of the line - torus intersection problem are given and new specification of the bounding volume for a torus is given as well. the presented approach is based on an idea of a line intersection with an envelope of rotating sphere that forms a torus. due to this approach new bounding volume can be formulated which is more effective as it enables to detect cases when the line passes the " hole " of a torus, too.
|
arxiv:2301.03191
|
the radio properties of powerful extended radio sources may be used to estimate the ambient gas density in the vicinity of radio lobes. a sample of 27 radio lobes from 14 radio galaxies and of 14 radio lobes from 8 radio loud quasars was constructed using sources from the published literature with sufficient radio information to allow an estimate of the ambient gas density. the ambient gas density as a function of separation of the lobe from the center of the parent galaxy indicates a composite density profile, where cygnus a plays the key role of determining the normalization for the ambient gas density. the composite density profile of the galaxies and quasars studied here is similar to the density profile of gas in low - redshift clusters of galaxies, which confirms the result obtained by daly [ 1 ] using a somewhat smaller sample of radio sources. the data presented here allow an estimate of the core gas density, core radius, and slope of the density profile assuming that the gas density can be fit by a king model. the data suggest that the core gas density decreases as the redshift of the source increases, and is consistent with either a roughly constant core radius, or a core radius that increases with increasing source redshift. thus, our results are completely consistent with observations indicating negative evolution of the cluster x - ray luminosity function. ( truncated to < 24 lines )
|
arxiv:astro-ph/9507105
|
this paper introduces a new behavioral system model with distinct external and internal signals possibly evolving on different time scales. this allows to capture abstraction processes or signal aggregation in the context of control and verification of large scale systems. for this new system model different notions of simulation and bisimulation are derived, ensuring that they are, respectively, preorders and equivalence relations for the system class under consideration. these relations can capture a wide selection of similarity notions available in the literature. this paper therefore provides a suitable framework for their comparison
|
arxiv:1402.3484
|
we study the local asymptotics at the edge for particle systems arising from : ( i ) eigenvalues of sums of unitarily invariant random hermitian matrices and ( ii ) signatures corresponding to decompositions of tensor products of representations of the unitary group. our method treats these two models in parallel, and is based on new formulas for observables described in terms of a special family of lifts, which we call supersymmetric lifts, of schur functions and multivariate bessel functions. we obtain explicit expressions for a class of supersymmetric lifts inspired by determinantal formulas for supersymmetric schur functions due to \ cite { mj03 }. asymptotic analysis of these lifts enable us to probe the edge. we focus on several settings where the airy point process arises.
|
arxiv:2009.06839
|
we identify close companions of brightest cluster galaxies ( bcgs ) for the purpose of quantifying the rate at which these galaxies grow via mergers. by exploiting deep photometric data from the cfhtls, we probe the number of companions per bcg ( nc ) with luminosity ratios down to those corresponding to potential minor mergers of 20 : 1. we also measure the average luminosity in companions per galaxy ( lc ). we find that nc and lc rise steeply with luminosity ratio for both the bcgs, and a control sample of other bright, red, cluster galaxies. the trend for bcgs rises more steeply, resulting in a larger number of close companions. for companions within 50kpc of a bcg, nc = 1. 38 + / - 0. 14 and lc = ( 2. 14 + / - 0. 31 ) x10 ^ ( 10 ) l _ sun and for companions within 50kpc of a luminosity matched control sample of non - bcgs, nc = 0. 87 + / - 0. 08 and lc = ( 1. 48 + / - 0. 20 ) x10 ^ ( 10 ) l _ sun. this suggests that the bcgs are likely to undergo more mergers compared to otherwise comparable luminous galaxies. additionally, compared to a local sample of luminous red galaxies, the more distant sample presented in this study ( with redshifts between 0. 15 - 0. 39, ) shows a higher nc, suggesting the younger and smaller bcgs are still undergoing hierarchical formation. using the millennium simulations we model and estimate the level of contamination due to unrelated cluster galaxies. the contamination by interloping galaxies is 50 % within projected separations of 50kpc, but within 30kpc, 60 % of identified companions are real physical companions. we conclude that the luminosity of bound merger candidates down to luminosity ratios of 20 : 1 could be adding as much as 10 % to the mass of a typical bcg over 0. 5gyr at redshifts of z ~ 0. 3.
|
arxiv:1206.1612
|
charge - changing cross - sections of $ ^ { 11 - 16 } $ c, $ ^ { 13 - 17 } $ n and $ ^ { 15 - 18 } $ o on a carbon target have been determined at energies around 300 mev / nucleon. a nucleon separation energy - dependent correction factor has been introduced to the glauber model calculation for extracting the nuclear charge radii from the experimental cccss. the charge radii of $ ^ { 11 } $ c, $ ^ { 13, 16 } $ n and $ ^ { 15 } $ o thus were determined for the first time. with the new radii, we studied the experimental mirror - difference charge radii ( $ \ delta r _ { \ text { ch } } ^ { \ text { mirror } } $ ) of $ ^ { 11 } $ b - $ ^ { 11 } $ c, $ ^ { 13 } $ c - $ ^ { 13 } $ n, $ ^ { 15 } $ n - $ ^ { 15 } $ o, $ ^ { 17 } $ n - $ ^ { 17 } $ ne pairs for the first time. we find that the $ \ delta r _ { \ text { ch } } ^ { \ text { mirror } } $ values of $ ^ { 13 } $ c - $ ^ { 13 } $ n and $ ^ { 15 } $ n - $ ^ { 15 } $ o pairs follow well the empirical relation to the isospin asymmetry predicted by the $ ab $ $ initio $ calculations, while $ \ delta r _ { \ text { ch } } ^ { \ text { mirror } } $ of $ ^ { 11 } $ b - $ ^ { 11 } $ c and $ ^ { 17 } $ n - $ ^ { 17 } $ ne pairs deviate from such relation by more than two standard deviations.
|
arxiv:2407.10199
|
we perform calculations of the energy shift of the nuclear clock transition frequency $ ^ { 229 } $ th as a function of the number of electrons in th ion. we demonstrate that the dependence of the nuclear frequency on electron configuration is significant. e. g., removing one electron from the atom leads to relative shift of the nuclear frequency $ \ sim 10 ^ { - 7 } $, which is twelve orders of magnitude larger than expected relative uncertainty of the nuclear clock transition frequency ( $ \ sim 10 ^ { - 19 } $ ). this leads to difference of the nuclear clock frequencies in th ~ iv, th ~ iii, th ~ ii and th ~ i. the relative change of the nuclear frequency between neutral th and its bare nucleus is 1 \ %. we also calculate the field shift constants for isotopic and isomeric shifts of atomic electron transitions in th ions.
|
arxiv:2309.11176
|
let $ x = \ { x _ t, t \ ge0 \ } $ be a c \ ` { a } dl \ ` { a } g l \ ' { e } vy process, centered, with moments of all orders. there are two families of orthogonal polynomials associated with $ x $. on one hand, the kailath - - segall formula gives the relationship between the iterated integrals and the variations of order $ n $ of $ x $, and defines a family of polynomials $ p _ 1 ( x _ 1 ), p _ 2 ( x _ 1, x _ 2 ),... $ that are orthogonal with respect to the joint law of the variations of $ x $. on the other hand, we can construct a sequence of orthogonal polynomials $ p ^ { \ sigma } _ n ( x ) $ with respect to the measure $ \ sigma ^ 2 \ delta _ 0 ( dx ) + x ^ 2 \ nu ( dx ) $, where $ \ sigma ^ 2 $ is the variance of the gaussian part of $ x $ and $ \ nu $ its l \ ' { e } vy measure. these polynomials are the building blocks of a kind of chaotic representation of the square functionals of the l \ ' { e } vy process proved by nualart and schoutens. the main objective of this work is to study the probabilistic properties and the relationship of the two families of polynomials. in particular, the l \ ' { e } vy processes such that the associated polynomials $ p _ n ( x _ 1,..., x _ n ) $ depend on a fixed number of variables are characterized. also, we give a sequence of l \ ' { e } vy processes that converge in the skorohod topology to $ x $, such that all variations and iterated integrals of the sequence converge to the variations and iterated integrals of $ x $.
|
arxiv:0804.2585
|
computer fonts can be one of solutions supporting a protection of information against electromagnetic penetration. this solution is called - soft tempest -. however, not every font has features which counteract the process of electromagnetic infiltration. the distinctive features of characters of font determine it. this article presents two sets of new computer fonts. these fonts are fully usable in everyday work. simultaneously they make it impossible to obtain information using the non - invasive method. names of these fonts are directly related to the shapes of the characters. each character of these fonts is built only with vertical and horizontal lines. the differences between them consist in the different widths of the vertical lines. the symmetrical safe font is built from vertical lines with the same widths. the asymmetrical safe font is built from vertical lines with two different widths of lines. however, the appropriate proportions of the widths of the lines and clearances of each character of the safe font have to be met.
|
arxiv:1902.07058
|
we consider fully nonlinear obstacle - type problems of the form \ begin { equation * } \ begin { cases } f ( d ^ { 2 } u, x ) = f ( x ) & \ text { a. e. in } b _ { 1 } \ cap \ omega, | d ^ { 2 } u | \ le k & \ text { a. e. in } b _ { 1 } \ backslash \ omega, \ end { cases } \ end { equation * } where $ \ omega $ is an unknown open set and $ k > 0 $. in particular, structural conditions on $ f $ are presented which ensure that $ w ^ { 2, n } ( b _ 1 ) $ solutions achieve the optimal $ c ^ { 1, 1 } ( b _ { 1 / 2 } ) $ regularity when $ f $ is h \ " older continuous. moreover, if $ f $ is positive on $ \ overline b _ 1 $, lipschitz continuous, and $ \ { u \ neq 0 \ } \ subset \ omega $, then we obtain local $ c ^ 1 $ regularity of the free boundary under a uniform thickness assumption on $ \ { u = 0 \ } $. lastly, we extend these results to the parabolic setting.
|
arxiv:1403.4300
|
the phenomenon of neutrino oscillation has been firmly established : neutrinos change their flavor in their path from their source to observers. this paper is dedicated to the description of experimental results in the oscillation field, of their present understanding and of possible future developments in experimental neutrino oscillation physics.
|
arxiv:0811.1194
|
antenna arrays will be an important ingredient in millimeter wave ( mmwave ) cellular systems. a natural application of antenna arrays is simultaneous transmission to multiple users. unfortunately, the hardware constraints in mmwave systems make it difficult to apply conventional lower frequency multiuser mimo precoding techniques at mmwave. this paper develops low complexity hybrid analog / digital precoding for downlink multiuser mmwave systems. hybrid precoding involves a combination of analog and digital processing that is inspired by the power consumption of complete radio frequency and mixed signal hardware. the proposed algorithm configures hybrid precoders at the transmitter and analog combiners at multiple receivers with a small training and feedback overhead. the performance of the proposed algorithm is analyzed in the large dimensional regime and in single path channels. when the analog and digital precoding vectors are selected from quantized codebooks, the rate loss due to the joint quantization is characterized and insights are given into the performance of hybrid beamforming compared with analog - only beamforming solutions. analytical and simulation results show that the proposed techniques offer higher sum rates compared with analog - only beamforming solutions, and approach the performance of the unconstrained digital beamforming with relatively small codebooks.
|
arxiv:1409.5162
|
the leidenfrost effect - prolonged evaporation of droplets on a superheated surface - happens only when the surface temperature is above a certain transitional value. here, we show that specially engineered droplets - liquid marbles - can exhibit similar effect at any superheated temperatures ( up to 465 oc tested in our experiment ) without a transition. very possibly, this phenomenon is due to the fact that liquid marbles are droplets coated with microparticles and these microparticles help levitate the liquid core and maintain an insulation layer between the liquid and the superheated surface.
|
arxiv:1207.0849
|
this work analyses main features that should be present in knowledge representation. it suggests a model for representation and a way to implement this model in software. representation takes care of both low - level sensor information and high - level concepts.
|
arxiv:cs/0208019
|
the magnetic field - induced changes in the conductivity of metals are the subject of intense interest, both for revealing new phenomena and as a valuable tool for determining their fermi surface. here, we report a hitherto unobserved magnetoresistive effect in ultra - clean layered metals, namely a negative longitudinal magnetoresistance that is capable of overcoming their very pronounced orbital one. this effect is correlated with the inter - layer coupling disappearing for fields applied along the so - called yamaji angles where the inter - layer coupling vanishes. therefore, it is intrinsically associated with the fermi points in the field - induced quasi - one - dimensional electronic dispersion, implying that it results from the axial anomaly among these fermi points. in its original formulation, the anomaly is predicted to violate separate number conservation laws for left - and right - handed chiral - ( e. g. weyl ) fermions. its observation in pdcoo $ _ 2 $, ptcoo $ _ 2 $ and sr $ _ 2 $ ruo $ _ 4 $ suggests that the anomaly affects the transport of clean conductors, particularly near the quantum limit.
|
arxiv:1412.5168
|
we study, in the quenched approximation, luescher ' s relation between pion scattering lengths and the finite - volume energy of two pions at rest. the quenched relation is drastically different from the full theory one ; in particular, ` ` enhanced finite - volume corrections " of order $ l ^ 0 = 1 $ and $ l ^ { - 2 } $ occur at one loop ( $ l $ is the linear size of the box ), due to the special properties of the $ \ eta ' $ in the quenched approximation. numerical examples show that the size of these effects can be substantial.
|
arxiv:hep-lat/9509022
|
a spectacular, transient mass - loss event in the hydrogen - deficient central star of the planetary nebula longmore 4 was discovered in 1992 by werner et al. during that event, the star temporarily changed from its normal pg 1159 spectrum to that of an emission - line [ wce ] star. i have been monitoring the spectrum of lo 4 since 2003. out of 31 spectra, two of them reveal mass - loss outbursts similar to the one seen in 1992, showing that the phenomenon recurs. i speculate on possible mechanisms for these unique outbursts, but emphasize that we still have no fully convincing explanation.
|
arxiv:0711.2056
|
ultraviolet circularly polarised light has been suggested as the initial cause of the homochirality of organic molecules in terrestrial organisms, via enantiomeric selection of prebiotic molecules by asymmetric photolysis. we present a theoretical investigation of mechanisms by which ultraviolet circular polarisation may be produced in star formation regions. in the scenarios considered here, light scattering produces only a small percentage of net circular polarisation at any point in space, due to the forward throwing nature of the phase function in the ultraviolet. by contrast, dichroic extinction can produce a fairly high percentage of net circular polarisation ( ~ 10 % ) and may therefore play a key role in producing an enantiomeric excess.
|
arxiv:astro-ph/0308289
|
first - order goedel logics are a family of infinite - valued logics where the sets of truth values v are closed subsets of [ 0, 1 ] containing both 0 and 1. different such sets v in general determine different goedel logics g _ v ( sets of those formulas which evaluate to 1 in every interpretation into v ). it is shown that g _ v is axiomatizable iff v is finite, v is uncountable with 0 isolated in v, or every neighborhood of 0 in v is uncountable. complete axiomatizations for each of these cases are given. the r. e. prenex, negation - free, and existential fragments of all first - order goedel logics are also characterized.
|
arxiv:math/0601147
|
the total, elastic and inelastic cross - sections for quasi - coherent interactions of protons with si28 have been measured using hadron - gamma coincidence method at the energy 1 gev. the limits for the existence of long - lived excited states of the si28 nucleus have been obtained in the range of energies from 0 to 0. 8 gev.
|
arxiv:hep-ex/0009031
|
we prove that the $ 2 ^ \ infty $ - class groups of the imaginary quadratic fields have the distribution predicted by the cohen - lenstra heuristic. given an elliptic curve e / q with full rational 2 - torsion and no rational cyclic subgroup of order four, we analogously prove that the $ 2 ^ \ infty $ - selmer groups of the quadratic twists of e have distribution as predicted by delaunay ' s heuristic. in particular, among the twists e ^ d with | d | < n, the number of curves with rank at least two is $ o ( n ) $.
|
arxiv:1702.02325
|
recently it has been shown that large pre - trained language models like bert ( devlin et al., 2018 ) are able to store commonsense factual knowledge captured in its pre - training corpus ( petroni et al., 2019 ). in our work we further evaluate this ability with respect to an application from industry creating a set of probes specifically designed to reveal technical quality issues captured as described incidents out of unstructured customer feedback in the automotive industry. after probing the out - of - the - box versions of the pre - trained models with fill - in - the - mask tasks we dynamically provide it with more knowledge via continual pre - training on the office of defects investigation ( odi ) complaints data set. in our experiments the models exhibit performance regarding queries on domain - specific topics compared to when queried on factual knowledge itself, as petroni et al. ( 2019 ) have done. for most of the evaluated architectures the correct token is predicted with a $ precision @ 1 $ ( $ p @ 1 $ ) of above 60 \ %, while for $ p @ 5 $ and $ p @ 10 $ even values of well above 80 \ % and up to 90 \ % respectively are reached. these results show the potential of using language models as a knowledge base for structured analysis of customer feedback.
|
arxiv:2012.02558
|
for many kinds of interventions, such as a new advertisement, marketing intervention, or feature recommendation, it is important to target a specific subset of people for maximizing its benefits at minimum cost or potential harm. however, a key challenge is that no data is available about the effect of such a prospective intervention since it has not been deployed yet. in this work, we propose a split - treatment analysis that ranks the individuals most likely to be positively affected by a prospective intervention using past observational data. unlike standard causal inference methods, the split - treatment method does not need any observations of the target treatments themselves. instead it relies on observations of a proxy treatment that is caused by the target treatment. under reasonable assumptions, we show that the ranking of heterogeneous causal effect based on the proxy treatment is the same as the ranking based on the target treatment ' s effect. in the absence of any interventional data for cross - validation, split - treatment uses sensitivity analyses for unobserved confounding to select model parameters. we apply split - treatment to both a simulated data and a large - scale, real - world targeting task and validate our discovered rankings via a randomized experiment for the latter.
|
arxiv:2011.05877
|
for strongly convex objectives that are smooth, the classical theory of gradient descent ensures linear convergence relative to the number of gradient evaluations. an analogous nonsmooth theory is challenging. even when the objective is smooth at every iterate, the corresponding local models are unstable and the number of cutting planes invoked by traditional remedies is difficult to bound, leading to convergences guarantees that are sublinear relative to the cumulative number of gradient evaluations. we instead propose a multipoint generalization of the gradient descent iteration for local optimization. while designed with general objectives in mind, we are motivated by a ` ` max - of - smooth ' ' model that captures the subdifferential dimension at optimality. we prove linear convergence when the objective is itself max - of - smooth, and experiments suggest a more general phenomenon.
|
arxiv:2111.15645
|
we solve exactly the regge - wheeler equation for axial perturbations of the schwarzschild metric in the black hole interior in terms of heun functions and give a description of the spectrum and the eigenfunctions of the interior problem. the phenomenon of attraction and repulsion of the discrete eigenvalues of gravitational waves is discovered.
|
arxiv:gr-qc/0603003
|
we present four - dimensional gauge theories in minkowski spacetime which effectively generate in certain energy regimes five - dimensional warped geometries whereas, in general, the fifth dimension is latticized. after discussing in detail several general aspects in such theories we present a number of exactly solvable examples. we also point out how a particular case, defined in an n - sided polygon and having a z _ n symmetry, has a similar realization in an appropriate supersymmetric setting with d3 - branes.
|
arxiv:hep-th/0106126
|
context : over the last decade, software researchers and engineers have developed a vast body of methodologies and technologies in requirements engineering for self - adaptive systems. although existing studies have explored various aspects of this field, no systematic study has been performed on summarizing modeling methods and corresponding requirements activities. objective : this study summarizes the state - of - the - art research trends, details the modeling methods and corresponding requirements activities, identifies relevant quality attributes and application domains and assesses the quality of each study. method : we perform a systematic literature review underpinned by a rigorously established and reviewed protocol. to ensure the quality of the study, we choose 21 highly regarded publication venues and 8 popular digital libraries. in addition, we apply text mining to derive search strings and use kappa coefficient to mitigate disagreements of researchers. results : we selected 109 papers during the period of 2003 - 2013 and presented the research distributions over various kinds of factors. we extracted 29 modeling methods which are classified into 8 categories and identified 14 requirements activities which are classified into 4 requirements timelines. we captured 8 concerned software quality attributes based on the iso 9126 standard and 12 application domains. conclusion : the frequency of application of modeling methods varies greatly. enterprise models were more widely used while behavior models were more rigorously evaluated. requirements - driven runtime adaptation was the most frequently studied requirements activity. activities at runtime were conveyed with more details. finally, we draw other conclusions by discussing how well modeling dimensions were considered in these modeling methods and how well assurance dimensions were conveyed in requirements activities.
|
arxiv:1704.00421
|
utility preference robust optimization ( pro ) has recently been proposed to deal with optimal decision making problems where the decision maker ' s ( dm ) preference over gains and losses is ambiguous. in this paper, we take a step further to investigate the case that the dm ' s preference is not only ambiguous but also potentially inconsistent or even displaying some kind of randomness. we propose a distributionally preference robust optimization ( dpro ) approach where the dm ' s preference is represented by a random utility function and the ambiguity is described by a set of probability distributions of the random utility. an obvious advantage of the new dpro model is that it no longer concerns the dm ' s preference inconsistency. in the case when the random utility functions are of piecewise linear structure, we propose two statistical methods for constructing the ambiguity set : an ellipsoidal method and a bootstrap method both of which are fundamentally based on the idea of confidence region with the sample mean of the random parameters, and demonstrate how the resulting dpro can be solved by a cutting surface algorithm and an misocp respectively. we also show how the dpro models with general random utility functions may be approximated by those with piecewise linear random utility functions. finally, we apply the proposed dpro model in car manufacturing and facility location planning and show how the random samples may be extracted by multinomial logit method and conjoint analysis / machine learning. the paper is the first attempt to use distributionally robust optimization methods for pro.
|
arxiv:2206.04491
|
we obtain closed - form expressions for all sums of the form \ mbox { $ \ sum _ { k = 1 } ^ n { f _ { mk } { } ^ 4 } $ } and \ mbox { $ \ sum _ { k = 1 } ^ n { l _ { mk } { } ^ 4 } $ } and their alternating versions, where $ f _ i $ and $ l _ i $ denote fibonacci and lucas numbers respectively. our results complement those of melham who studied the alternating sums.
|
arxiv:1706.00407
|
this paper is concerned with the nature of probability in physics, and in quantum mechanics in particular. it starts with a brief discussion of the evolution of itamar pitowsky ' s thinking about probability in quantum theory from 1994 to 2008, and the role of gleason ' s 1957 theorem in his derivation of the born rule. pitowsky ' s defence of probability therein as a logic of partial belief leads us into a broader discussion of probability in physics, in which the existence of objective " chances " is questioned, and the status of david lewis ' influential principal principle is critically examined. this is followed by a sketch of the work by david deutsch and david wallace which resulted in the deutsch - wallace ( dw ) theorem in everettian quantum mechanics. it is noteworthy that the authors of this important decision - theoretic derivation of the born rule have different views concerning the meaning of probability. the theorem, which was the subject of a 2007 critique by meir hemmo and pitowsky, is critically examined, along with recent related work by john earman. here our main argument is that the dw theorem does not provide a justification of the principal principle, contrary to claims by wallace and simon saunders. a final section analyses recent claims to the effect that that the dw theorem is redundant, a conclusion that seems to be reinforced by consideration of probabilities in " deviant ' branches in the everettian multiverse.
|
arxiv:2010.11591
|
to overcome the domain gap between synthetic and real - world datasets, unsupervised domain adaptation methods have been proposed for semantic segmentation. majority of the previous approaches have attempted to reduce the gap either at the pixel or feature level, disregarding the fact that the two components interact positively. to address this, we present contrastive feature and pixel alignment ( confeti ) for bridging the domain gap at both the pixel and feature levels using a unique contrastive formulation. we introduce well - estimated prototypes by including category - wise cross - domain information to link the two alignments : the pixel - level alignment is achieved using the jointly trained style transfer module with the prototypical semantic consistency, while the feature - level alignment is enforced to cross - domain features with the \ textbf { pixel - to - prototype contrast }. our extensive experiments demonstrate that our method outperforms existing state - of - the - art methods using deeplabv2. our code is available at https : / / github. com / cxa9264 / confeti
|
arxiv:2306.09098
|
now an important tool for establishing independence results in set theory. 1964 : inspired by the fundamental randomness in physics, gregory chaitin starts publishing results on algorithmic information theory ( measuring incompleteness and randomness in mathematics ). 1966 : paul cohen showed that the axiom of choice is unprovable in zf even without urelements. 1970 : hilbert ' s tenth problem is proven unsolvable : there is no recursive solution to decide whether a diophantine equation ( multivariable polynomial equation ) has a solution in integers. 1971 : suslin ' s problem is proven to be independent from zfc. = = toward resolution of the crisis = = starting in 1935, the bourbaki group of french mathematicians started publishing a series of books to formalize many areas of mathematics on the new foundation of set theory. the intuitionistic school did not attract many adherents, and it was not until bishop ' s work in 1967 that constructive mathematics was placed on a sounder footing. one may consider that hilbert ' s program has been partially completed, so that the crisis is essentially resolved, satisfying ourselves with lower requirements than hilbert ' s original ambitions. his ambitions were expressed in a time when nothing was clear : it was not clear whether mathematics could have a rigorous foundation at all. there are many possible variants of set theory, which differ in consistency strength, where stronger versions ( postulating higher types of infinities ) contain formal proofs of the consistency of weaker versions, but none contains a formal proof of its own consistency. thus the only thing we do not have is a formal proof of consistency of whatever version of set theory we may prefer, such as zf. in practice, most mathematicians either do not work from axiomatic systems, or if they do, do not doubt the consistency of zfc, generally their preferred axiomatic system. in most of mathematics as it is practiced, the incompleteness and paradoxes of the underlying formal theories never played a role anyway, and in those branches in which they do or whose formalization attempts would run the risk of forming inconsistent theories ( such as logic and category theory ), they may be treated carefully. the development of category theory in the middle of the 20th century showed the usefulness of set theories guaranteeing the existence of larger classes than does zfc, such as von neumann – bernays – godel set theory or tarski – grothendieck set theory, albeit that in very many cases the use of large cardinal axioms or grothend
|
https://en.wikipedia.org/wiki/Foundations_of_mathematics
|
random polyampholytes ( pas ) contain positively and negatively charged monomers that are distributed randomly along the polymer chain. the interaction between charges is assumed to be given by the debye - huckel potential. we show that the size of the pa is determined by an interplay between electrostatic interactions, giving rise to the polyelectrolyte ( pe ) effect due to net charge per monomer ( $ \ sigma $ ), and an effective attractive pa interaction due to charge fluctuations, $ \ delta \ sigma $. the interplay between these terms gives rise to non - monotonic dependence of the radius of gyration, $ r _ g $ on the inverse debye length, $ \ kappa $ when pa effects are important ( $ { \ frac { \ delta \ sigma } { \ sigma } } > 1 $ ). in the opposite limit, $ r _ g $ decreases monotonically with increasing $ \ kappa $. simulations of pa chains, using a charged bead - spring model, further corroborates our theoretical predictions. the simulations unambiguously show that conformational heterogeneity manifests itself among sequences that have identical pa parameters. a clear implication is that the phases of pa sequences, and by inference idps, cannot be determined using only the bare pa parameters ( $ \ sigma $ and $ \ delta \ sigma $ ). the theory is used to calculate the changes in $ r _ g $ on $ n $, the number of residues for a set of intrinsically disordered proteins ( idps ). for a certain class of idps, with $ n $ between 24 to 441, the size grows as $ r _ g \ sim n ^ { 0. 6 } $, which agrees with data from small angle x - ray scattering ( saxs ) experiments.
|
arxiv:1804.05609
|
in this paper, we address the problem of stabilization in continuous time linear dynamical systems using state feedback when compressive sampling techniques are used for state measurement and reconstruction. in [ 5 ], we had introduced the concept of using l1 reconstruction technique, commonly used in sparse data reconstruction, for state measurement and estimation in a discrete time linear system. in this work, we extend the previous scenario to analyse continuous time linear systems. we investigate the effect of switching within a set of sparsifiers, introduced in [ 5 ], on the stability of a linear plant in continuous time settings. initially, we analyze the problem of stabilization in low dimensional systems, following which we generalize the results to address the problem of stabilization in systems of arbitrary dimensions.
|
arxiv:1110.3531
|
radiation spectrum of extreme relativistic electrons and a probability of electron - positron pair production by energetic photons in a strong plasma wakefield are derived in the framework of a semiclassical approach. it is shown that that the radiation losses of the relativistic electron in the plasma wakefield scale as $ \ propto \ epsilon ^ { 2 / 3 } $ in the quantum limit when the energy of the radiated photon becomes close to the electron energy, $ \ epsilon $. the quantum effects will play a key role in future plasma - based accelerators operating at ultrahigh energy of the electrons.
|
arxiv:physics/0611094
|
i review the current state of our understanding of the galaxy formation and evolution process from the modeler ' s perspective. with the advent of the cold dark matter model and the support of fast computers and advanced simulation techniques, there has been considerable progress in explaining the growth of structure on the largest scales and in reproducing some of the basic properties of galaxies and their evolution with redshift. however, many properties of galaxies are still only poorly understood or appear to be in conflict with the prediction of the cold dark matter model. i discuss in what direction the next generation of galaxy formation models may go and why a large space - based optical - uv telescope could be critical for the calibration and testing of these advanced models.
|
arxiv:astro-ph/0208252
|
we present detailed spectroscopic analysis of nitrogen abundances in 31 unevolved metal - poor stars analysed by spectral synthesis of the near - uv nh band at 3360 a observed at high resolution with various telescopes. we found that [ n / fe ] scales with that of iron in the metallicity range - 3. 1 < [ fe / h ] < 0 with the slope 0. 01 + - 0. 02. furthermore, we derive uniform and accurate ( n / o ) ratios using oxygen abundances from near - uv oh lines obtained in our previous studies. we find that a primary component of nitrogen is required to explain the observations. the nh lines are discovered in the vlt / uves spectra of the very metal - poor subdwarfs g64 - 12 and lp815 - 43 indicating that these stars are n rich. the results are compared with theoretical models and observations of extragalactic hii regions and damped ly $ \ alpha $ systems. this is the first direct comparison of the ( n / o ) ratios in these objects with those in galactic stars.
|
arxiv:astro-ph/0405049
|
using the transfer principle, we classify the periodic points on the regular $ n $ - gon and double $ n $ - gon translation surfaces and deduce consequences for the finite blocking problem on rational triangles that unfold to these surfaces.
|
arxiv:2011.02668
|
by means of the method of moving frenet - serret frame the set of equations of motion is derived for spinning particle in an arbitrary external field, which is determined by potential depending from both position and the state of movement, as well as by two pseudo - vectors one of which is easily associated with external magnetic field, and another still remains undetermined. the equations give a possibility to describe the motion of both massive and massless particles with spin. all solutions of the equations of motion in the absence of external fields were found, and besides, we give more precise definition of a free object. it turns out that the massive particles always possess a longitudinal polarization. there are possible transversal motions of the following types : 1 ) oscillatory motion with proper frequency, 2 ) circular motion, and 3 ) complicated motion along rosette trajectories round the center of inertia with the velocity, varying in finite limits. free massless particles can either fluctuate or move along complicated paths around fixed centers of balance, when the spin of the particles can have any direction.
|
arxiv:1511.03515
|
in this paper we discuss the reason why the parameters of the sersic model best - fitting the major axis light profile of elliptical galaxies can differ significantly from those derived for the minor axis profile. we show that this discrepancy is a natural consequence of the fact that the isophote eccentricity varies with the radius of the isophote and present a mathematical transformation that allows the minor axis sersic model to be calculated from the major axis model, provided that the elliptical isophotes are aligned and concentric and that their eccentricity can be represented by a well behaved, though quite general, function of the radius. when there is no variation in eccentricity only the effective radius changes in the sersic model, while for radial - dependent eccentricity the transformation which allows the minor axis sersic model to be calculated from the major axis model is given by the lerch phi transcendental function. the proposed transformation was tested using photometric data for 28 early - type galaxies.
|
arxiv:astro-ph/0309589
|
one of the major challenges in stochastic thermodynamics is to compute the distributions of stochastic observables for small - scale systems for which fluctuations play a significant role. hitherto much theoretical and experimental research has focused on systems composed of passive brownian particles. in this paper, we study the heat fluctuations in a system of interacting active particles. specifically we consider a one - dimensional harmonic chain of $ n $ active ornstein - uhlenbeck particles, with the chain ends connected to heat baths of different temperatures. we compute the moment - generating function for the heat flow in the steady state. we employ our general framework to explicitly compute the moment - generating function for two example single - particle systems. further, we analytically obtain the scaled cumulants for the heat flow for the chain. numerical langevin simulations confirm the long - time analytical expressions for first and second cumulants for the heat flow for a two - particle chain.
|
arxiv:2103.09358
|
video action detection ( vad ) is a formidable vision task that involves the localization and classification of actions within the spatial and temporal dimensions of a video clip. among the myriad vad architectures, two - stage vad methods utilize a pre - trained person detector to extract the region of interest features, subsequently employing these features for action detection. however, the performance of two - stage vad methods has been limited as they depend solely on localized actor features to infer action semantics. in this study, we propose a new two - stage vad framework called joint actor - scene context relation modeling based on visual semantics ( jarvis ), which effectively consolidates cross - modal action semantics distributed globally across spatial and temporal dimensions using transformer attention. jarvis employs a person detector to produce densely sampled actor features from a keyframe. concurrently, it uses a video backbone to create spatio - temporal scene features from a video clip. finally, the fine - grained interactions between actors and scenes are modeled through a unified action - scene context transformer to directly output the final set of actions in parallel. our experimental results demonstrate that jarvis outperforms existing methods by significant margins and achieves state - of - the - art performance on three popular vad datasets, including ava, ucf101 - 24, and jhmdb51 - 21.
|
arxiv:2408.03612
|
the galactic microquasar grs 1915 + 105 exhibits at least sixteen types of variability classes. transitions from one class to another could take place in a matter of hours. in some of the classes, the spectral state transitions ( burst - off to burst - on and vice versa ) were found to take place in a matter of few to few tens of seconds. in the literature, there is no attempt to understand in which order these classes were exhibited. since the observation was not continuous, the appearances of these classes seem to be in random order. our goal is to find a natural sequence of these classes and compare with the existing observations. we also wish to present a physical interpretation of the sequence so obtained using two component advective flow model of black hole accretion. in the present paper, we compute the ratios of the power - law photons and the black body photons in the spectrum of each class and call these ratios as the ` comptonizing efficiency ' ( ce ). we sequence the classes from the low to the high value of ce. we clearly find that each variability class could be characterized by a unique average comptonizing efficiency. the sequence of the classes based on this parameter seem to be corroborated by a handful of the observed transitions caught by rossi x - ray timing explorer and the indian payload indian x - ray astronomy experiment and we believe that future observation of the object would show that the transitions can only take place between consecutive classes in this sequence. since the power - law photons are produced by inverse comptonization of the intercepted soft - photons from the keplerian disk, a change in ce actually corresponds to a change in geometry of the compton cloud. thus we claim that the size of the compton cloud gradually rises from very soft class to the very hard class.
|
arxiv:1101.1739
|
modern artificial intelligence ( ai ) systems are powered by foundation models. this paper presents a new set of foundation models, called llama 3. it is a herd of language models that natively support multilinguality, coding, reasoning, and tool usage. our largest model is a dense transformer with 405b parameters and a context window of up to 128k tokens. this paper presents an extensive empirical evaluation of llama 3. we find that llama 3 delivers comparable quality to leading language models such as gpt - 4 on a plethora of tasks. we publicly release llama 3, including pre - trained and post - trained versions of the 405b parameter language model and our llama guard 3 model for input and output safety. the paper also presents the results of experiments in which we integrate image, video, and speech capabilities into llama 3 via a compositional approach. we observe this approach performs competitively with the state - of - the - art on image, video, and speech recognition tasks. the resulting models are not yet being broadly released as they are still under development.
|
arxiv:2407.21783
|
every major technical invention resurfaces the dual - use dilemma - - the new technology has the potential to be used for good as well as for harm. generative ai ( genai ) techniques, such as large language models ( llms ) and diffusion models, have shown remarkable capabilities ( e. g., in - context learning, code - completion, and text - to - image generation and editing ). however, genai can be used just as well by attackers to generate new attacks and increase the velocity and efficacy of existing attacks. this paper reports the findings of a workshop held at google ( co - organized by stanford university and the university of wisconsin - madison ) on the dual - use dilemma posed by genai. this paper is not meant to be comprehensive, but is rather an attempt to synthesize some of the interesting findings from the workshop. we discuss short - term and long - term goals for the community on this topic. we hope this paper provides both a launching point for a discussion on this important topic as well as interesting problems that the research community can work to address.
|
arxiv:2308.14840
|
the cheeger inequalities give an upper and lower bound on the spectral gap of discrete laplacians defined on a graph in terms of the geometric characteristics of the graph. we generalise this approach and we employ it to determine if a given discrete hamiltonian with non - positive elements is gapped or not in the thermodynamic limit. first, we define the graph that corresponds to such a generic hamiltonian. then we present a suitable generalisation of the cheeger inequalities that overcomes scaling deficiencies of the original version. by employing simple examples we illustrate how the generalised cheeger inequalities can successfully identify gapped or gapless phases and we comment on the computational complexity of this approach.
|
arxiv:1010.4130
|
targeted stimulation of the brain has the potential to treat mental illnesses. we propose an approach to help design the stimulation protocol by identifying electrical dynamics across many brain regions that relate to illness states. we model multi - region electrical activity as a superposition of activity from latent networks, where the weights on the latent networks relate to an outcome of interest. in order to improve on drawbacks of latent factor modeling in this context, we focus on supervised autoencoders ( saes ), which can improve predictive performance while maintaining a generative model. we explain why saes yield improved predictions, describe the distributional assumptions under which saes are an appropriate modeling choice, and provide modeling constraints to ensure biological relevance of the learned network. we use the analysis strategy to find a network associated with stress that characterizes a genotype associated with bipolar disorder. this discovered network aligns with a previously used stimulation technique, providing experimental validation of our approach.
|
arxiv:2004.05209
|
this paper proposes a safe reinforcement learning ( rl ) algorithm that approximately solves the state - constrained optimal control problem for continuous - time uncertain nonlinear systems. we formulate the safe rl problem as the minimization of a lagrangian that includes the cost functional and a user - defined barrier lyapunov function ( blf ) encoding the state constraints. we show that the analytical solution obtained by the application of karush - kuhn - tucker ( kkt ) conditions contains a state - dependent expression for the lagrange multiplier, which is a function of uncertain terms in the system dynamics. we argue that a naive estimation of the lagrange multiplier may lead to safety constraint violations. to obviate this challenge, we propose an actor - critic - identifier - lagrangian ( acil ) algorithm that learns optimal control policies from online data without compromising safety. we provide safety and boundedness guarantees with the proposed algorithm and compare its performance with existing offline / online rl methods via a simulation study.
|
arxiv:2305.12967
|
for a given quantum field theory, provided the area of the entangling surface is fixed, what surface maximizes entanglement entropy? we analyze the answer to this question in four and higher dimensions. surprisingly, in four dimensions the answer is related to a mathematical problem of finding surfaces which minimize the willmore ( bending ) energy and eventually to the willmore conjecture. we propose a generalization of the willmore energy in higher dimensions and analyze its minimizers in a general class of topologies $ s ^ m \ times s ^ n $ and make certain observations and conjectures which may have some mathematical significance.
|
arxiv:1407.4719
|
let $ g $ be a graph each edge $ e $ of which is given a length $ \ ell ( e ) $. this naturally induces a distance $ d _ \ ell ( x, y ) $ between any two vertices $ x, y $, and we let $ \ ell - top $ denote the completion of the corresponding metric space. it turns out that several well studied topologies on infinite graphs are special cases of $ \ ell - top $. moreover, it seems that $ \ ell - top $ is the right setting for studying various problems. the aim of this paper is to introduce $ \ ell - top $, providing basic facts, motivating examples and open problems, and indicate possible applications.
|
arxiv:0903.1744
|
we report the first terahertz kerr measurements on bulk crystals of the topological insulator bi2se3. at t = 10k and fields up to 8t, the real and imaginary kerr angle and reflectance measurements utilizing both linearly and circularly polarized incident radiation were measured at a frequency of 5. 24mev. a single fluid free carrier bulk response can not describe the line - shape. surface states with a small mass and surprisingly large associated spectral weight quantitatively fit all data. however, carrier concentration inhomogeneity has not been ruled out. a method employing a gate is shown to be promising for separating surface from bulk effects.
|
arxiv:1007.4482
|
we show that each rigid symmetry of a d - string action is contained in a family of infinitely many symmetries. in particular, kappa - invariant d - string actions have infinitely many supersymmetries. the result is not restricted to standard d - string actions, but holds for any two - dimensional action depending on an abelian world - sheet gauge field only via the field strength. it applies thus also to manifestly $ sl ( 2, z ) $ covariant d - string actions. furthermore, it extends analogously to $ d $ - dimensional actions with $ ( d - 1 ) $ - form gauge potentials, such as brane actions with dynamical tension.
|
arxiv:hep-th/9807113
|
we investigate static and spherically symmetric black hole ( bh ) solutions in shift - symmetric quadratic - order degenerate higher - order scalar - tensor ( dhost ) theories. we allow a nonconstant kinetic term $ x = g ^ { \ mu \ nu } \ partial _ \ mu \ phi \ partial _ \ nu \ phi $ for the scalar field $ \ phi $ and assume that $ \ phi $ is, like the spacetime, a pure function of the radial coordinate $ r $, namely $ \ phi = \ phi ( r ) $. first, we find analytic static and spherically symmetric vacuum solutions in the so - called { \ it class ia } dhost theories, which include the quartic horndeski theories as a subclass. we consider several explicit models in this class and apply our scheme to find the exact vacuum bh solutions. bh solutions obtained in our analysis are neither schwarzschild or schwarzschild ( anti - ) de sitter. we show that a part of the bh solutions obtained in our analysis are free of ghost and laplacian instabilities and are also mode stable against the odd - parity perturbations. finally, we argue the case that the scalar field has a linear time dependence $ \ phi = qt + \ psi ( r ) $ and show several simple examples of nontrivial bh solutions with a nonconstant kinetic term obtained analytically and numerically.
|
arxiv:1912.01744
|
we investigate the implications of parity - violating electron scattering experiment on neutron skin thickness of $ ^ { 48 } $ ca ( crex ) and $ ^ { 208 } $ pb ( prex - ii ) data on the bulk properties of finite nuclei, nuclear matter, and neutron stars. the neutron skin thickness from the crex and prex - ii data is employed to constrain the parameters of relativistic mean field models which includes different non - linear, self and cross - couplings among isoscalar - scalar $ \ sigma $, isoscalar - vector $ \ omega $, isovector - scalar $ \ delta $ and isovector - vector $ \ rho $ meson fields up to the quartic order. three parametrizations of rmf model are proposed by fitting crex, prex - ii and both crex as well as prex - ii data to assess their implications. a covariance analysis is performed to assess the theoretical uncertainties of model parameters and nuclear matter observables along with correlations among them. the rmf model parametrization obtained with the crex data acquires much smaller value of symmetry energy ( j = 28. 97 $ \ pm $ 0. 99 mev ), its slope parameter ( l = 30. 61 $ \ pm 6. 74 $ mev ) in comparison to those obtained with prex - ii data. the neutron star properties are studied by employing the equations of state ( eoss ) composed of nucleons and leptons in $ \ beta $ equilibrium.
|
arxiv:2305.05937
|
the $ \ mathsf { hybrid } $ model, introduced in [ augustine et al., soda ' 20 ], provides a theoretical foundation for networks that allow multiple communication modes. the model follows the principles of synchronous message passing, whereas nodes are allowed to use \ textit { two } fundamentally different communication modes. first, a local mode where nodes may exchange arbitrary information per round over edges of a local communication graph $ g $ ( akin to the $ \ mathsf { local } $ model ). second, a global mode where every node may exchange $ o ( \ log n ) $ messages of size $ o ( \ log n ) $ bits per round with arbitrary nodes in the network. the $ \ mathsf { hybrid } $ model intends to reflect the conditions of many real hybrid networks, where high - bandwidth but inherently local communication is combined with highly flexible global communication with restricted bandwidth. we continue to explore the power and limitations of the $ \ mathsf { hybrid } $ model by investigating the complexity of computing shortest paths and diameter of the local communication graph $ g $. we improve on the known upper bound for the exact all pairs shortest paths problem ( apsp ) from [ augustine et al., soda ' 20 ] and provide algorithms to approximate solutions for the $ k $ source shortest paths problem ( $ k $ - sssp ). we demonstrate that our results for apsp and $ k $ - ssp are almost tight ( up to poly - logarithmic factors ). furthermore, we give an improved algorithm for the exact single source shortest paths problem for graphs with large diameter. for the problem of approximating the diameter of the local communication network we give the first non - trivial upper bound. this upper bound is complemented by a lower bound for the exact diameter problem.
|
arxiv:2006.08408
|
we consider the bit complexity of computing chow forms and their generalization to multiprojective spaces. we develop a deterministic algorithm using resultants and obtain a single exponential complexity upper bound. earlier computational results for chow forms were in the arithmetic complexity model, and our result represents the first bit complexity bound. we also extend our algorithm to hurwitz forms in projective space, and explore connections between multiprojective hurwitz forms and matroid theory. the motivation for our work comes from incidence geometry where intriguing computational algebra problems remain open.
|
arxiv:2202.11582
|
automatic speech recognition and voice identification systems are being deployed in a wide array of applications, from providing control mechanisms to devices lacking traditional interfaces, to the automatic transcription of conversations and authentication of users. many of these applications have significant security and privacy considerations. we develop attacks that force mistranscription and misidentification in state of the art systems, with minimal impact on human comprehension. processing pipelines for modern systems are comprised of signal preprocessing and feature extraction steps, whose output is fed to a machine - learned model. prior work has focused on the models, using white - box knowledge to tailor model - specific attacks. we focus on the pipeline stages before the models, which ( unlike the models ) are quite similar across systems. as such, our attacks are black - box and transferable, and demonstrably achieve mistranscription and misidentification rates as high as 100 % by modifying only a few frames of audio. we perform a study via amazon mechanical turk demonstrating that there is no statistically significant difference between human perception of regular and perturbed audio. our findings suggest that models may learn aspects of speech that are generally not perceived by human subjects, but that are crucial for model accuracy. we also find that certain english language phonemes ( in particular, vowels ) are significantly more susceptible to our attack. we show that the attacks are effective when mounted over cellular networks, where signals are subject to degradation due to transcoding, jitter, and packet loss.
|
arxiv:1910.05262
|
the angular power spectrum is a powerful statistic for analysing cosmological signals imprinted in the clustering of matter. however, current galaxy and quasar surveys cover limited portions of the sky, and are contaminated by systematics that can mimic cosmological signatures and jeopardise the interpretation of the measured power spectra. we provide a framework for obtaining unbiased estimates of the angular power spectra of large - scale structure surveys at the largest scales using quadratic estimators. the method is tested by analysing the 600 cmass mock catalogues constructed by manera et al. ( 2013 ) for the baryon oscillation spectroscopic survey ( boss ). we then consider the richards et al. ( 2009 ) catalogue of photometric quasars from the sixth data release ( dr6 ) of the sloan digital sky survey ( sdss ), which is known to include significant stellar contamination and systematic uncertainties. focusing on the sample of ultraviolet - excess ( uvx ) sources, we show that the excess clustering power present on the largest - scales can be largely mitigated by making use of improved sky masks and projecting out the modes corresponding to the principal systematics. in particular, we find that the sample of objects with photometric redshift $ 1. 3 < z _ p < 2. 2 $ exhibits no evidence of contamination when using our most conservative mask and mode projection. this indicates that any residual systematics are well within the statistical uncertainties. we conclude that, using our approach, this sample can be used for cosmological studies.
|
arxiv:1306.0005
|
we theoretically study the transmittance for normal incidence of linearly polarized light between two media separated by a strained graphene monolayer. we analytically characterize the degree of dichroism and the transparency of graphene as a function of an arbitrary uniform strain and the incident polarization. we discuss how measurements of dichroism and transparency for two different polarization directions can be used to determine the magnitude and direction of strain. ours findings result in very useful tools to tune the graphene absorption by mechanical strain, as well as to design nano - devices to determine crack propagation in materials.
|
arxiv:1411.1376
|
labeling intervertebral discs is relevant as it notably enables clinicians to understand the relationship between a patient ' s symptoms ( pain, paralysis ) and the exact level of spinal cord injury. however manually labeling those discs is a tedious and user - biased task which would benefit from automated methods. while some automated methods already exist for mri and ct - scan, they are either not publicly available, or fail to generalize across various imaging contrasts. in this paper we combine a fully convolutional network ( fcn ) with inception modules to localize and label intervertebral discs. we demonstrate a proof - of - concept application in a publicly - available multi - center and multi - contrast mri database ( n = 235 subjects ). the code is publicly available at https : / / github. com / neuropoly / vertebral - labeling - deep - learning.
|
arxiv:2003.04387
|
in this paper we examine t - violating triple - product correlations ( tp ' s ) in b - > v1 v2 decays. tp ' s are excellent probes of physics beyond the standard model ( sm ) for two reasons : ( i ) within the sm, most tp ' s are expected to be tiny, and ( ii ) unlike direct cp asymmetries, tp ' s are not suppressed by the small strong phases which are expected in b decays. tp ' s are obtained via the angular analysis of b - > v1 v2. in a general analysis based on factorization, we demonstrate that the most promising decays for measuring tp ' s in the sm involve excited final - state vector mesons, and we provide estimates of such tp ' s. we find that there are only a handful of decays in which large tp ' s are possible, and the size of these tp ' s depends strongly on the size of nonfactorizable effects. we show that tp ' s which vanish in the sm can be very large in models with new physics. the measurement of a nonzero tp asymmetry in a decay where none is expected would specifically point to new physics involving large couplings to the right - handed b - quark.
|
arxiv:hep-ph/0303159
|
we discuss cosmological consequences of the existence of physics beyond the standard model that exhibits banks - zaks and unparticle behavior in the uv and ir respectively. we first derive the equation of state for unparticles and use it to obtain the temperature dependence of the corresponding energy and entropy densities. we then formulate the boltzmann and kubo equations for both the unparticles and the banks - zaks particles, and use these results to determine the equilibrium conditions between the standard model and the new physics. we conclude by obtaining the constraints on the effective number of degrees of freedom of unparticles imposed by big - bang nucleosynthesis.
|
arxiv:0809.0977
|
we consider a system rotating at extremely high angular velocity, so that its matter is found mostly at the light - cylinder. we posit that it can be described by quantum fields confined to the two - dimensional cylindrical surface rotating about its symmetry axis. we apply this model to study the electromagnetic radiation. in particular, we compute the photon spectrum emitted by the quark - gluon plasma.
|
arxiv:2308.10349
|
in this letter, we present the direct loss tangent measurement of a high - resistivity intrinsic ( 100 ) silicon wafer in the temperature range from ~ 70 mk to 1 k, approaching the quantum regime. the measurement was performed using a technique that takes advantage of a high quality factor superconducting niobium resonator and allows to directly measure the loss tangent of insulating materials with high level of accuracy and precision. we report silicon loss tangent values at the lowest temperature and for electric field amplitudes comparable to those found in planar transmon devices one order of magnitude larger than what was previously estimated. in addition, we discover a non - monotonic trend of the loss tangent as a function of temperature that we describe by means of a phenomenological model based on variable range hopping conduction between localized states around the fermi energy. we also observe that the dissipation increases as a function of the electric field and that this behavior can be qualitatively described by the variable range hopping conduction mechanism as well. this study lays the foundations for a novel approach to investigate the loss mechanisms and accurately estimate the loss tangent in insulating materials in the quantum regime, leading to a better understanding of coherence in quantum devices.
|
arxiv:2108.08894
|
this paper provides a theoretical framework for understanding the performance of reconfigurable intelligent surface ( ris ) - aided massive multiple - input multiple - output ( mimo ) with zero - forcing ( zf ) detectors under imperfect channel state information ( csi ). we first propose a low - overhead minimum mean square error ( mmse ) channel estimator, and then derive and analyze closed - form expressions for the uplink achievable rate. our analytical results demonstrate that : $ 1 ) $ regardless of the ris phase shift design, the rate of all users scales at least on the order of $ \ mathcal { o } \ left ( \ log _ 2 \ left ( mn \ right ) \ right ) $, where $ m $ and $ n $ are the numbers of antennas and reflecting elements, respectively ; $ 2 ) $ by aligning the ris phase shifts to one user, the rate of this user can at most scale on the order of $ \ mathcal { o } \ left ( \ log _ 2 \ left ( mn ^ 2 \ right ) \ right ) $ ; $ 3 ) $ either $ m $ or the transmit power can be reduced inversely proportional to $ n $, while maintaining a given rate. furthermore, we propose two low - complexity majorization - minimization ( mm ) - based algorithms to optimize the sum user rate and the minimum user rate, respectively, where closed - form solutions are obtained in each iteration. finally, simulation results validate all derived analytical results. our simulation results also show that the maximum sum rate can be closely approached by simply aligning the ris phase shifts to an arbitrary user.
|
arxiv:2111.01585
|
we examine the evolution of an almost circular keplerian orbit interacting with unbound perturbers. we calculate the change in eccentricity and angular momentum that results from a single encounter, assuming the timescale for the interaction is shorter than the orbital period. the orbital perturbations are incorporated into a boltzmann equation that allows for eccentricity dissipation. we present an analytic solution to the boltzmann equation that describes the distribution of orbital eccentricity and relative inclination as a function of time. the eccentricity and inclination of the binary do not evolve according to a normal random walk but perform a levy flight. the slope of the mass spectrum of perturbers dictates whether close gravitational scatterings are more important than distant tidal ones. when close scatterings are important, the mass spectrum sets the slope of the eccentricity and inclination distribution functions. we use this general framework to understand the eccentricities of several kuiper belt systems : pluto, 2003 el 61, and eris. we use the model of tholen et al ( 2007 ) to separate the non - keplerian components of the orbits of pluto ' s outer moons nix and hydra from the motion excited by interactions with other kuiper belt objects. our distribution is consistent with the observations of nix, hydra, and the satellites of 2003 el 61 and eris. we address applications of this work to objects outside of the solar system, such as extrasolar planets around their stars and millisecond pulsars.
|
arxiv:0810.1525
|
inspired by the group structure on $ s ^ 1 / \ bbz $, we introduce a weak hopfish structure on an irrational rotation algebra $ a $ of finite fourier series. we consider a class of simple $ a $ - modules defined by invertible elements, and we compute the tensor product between these modules defined by the hopfish structure. this class of simple modules turns out to generate an interesting commutative unital ring.
|
arxiv:math/0604405
|
we study the ginzburg - landau equations in order to describe a two - dimensional superconductor in a bounded domain. using the properties of a particular integrability point ( $ \ kappa = 1 / \ sqrt2 $ ) of these nonlinear equations which allows vortex solutions, we obtain a closed expression for the energy of the superconductor. the presence of the boundary provides a selection mechanism for the number of vortices. a perturbation analysis around $ \ kappa = 1 / \ sqrt2 $ enables us to include the effects of the vortex interactions and to describe quantitatively the magnetization curves recently measured on small superconducting disks. we also calculate the optimal vortex configuration and obtain an expression for the confining potential away from the london limit.
|
arxiv:cond-mat/0001219
|
we calculate the x - ray absorption spectra of liquid water at ambient conditions and of hexagonal ice close to melting, using a static gw approach that includes approximately local field effects. quantum dynamics of the nuclei is taken into account by averaging the absorption cross section over molecular configurations generated by path integral simulations. we find that inclusion of quantum disorder is essential to bring the calculated spectra in close agreement with experiment. in particular, the intensity of the pre - edge feature, a spectral signature of broken and distorted hydrogen bonds, is accurately reproduced, in water and ice, only when quantum nuclei are considered. the effect of the local fields is less important but non negligible, particularly in ice.
|
arxiv:1204.0268
|
we have analysed the combined greenwich and solar optical observing network ( soon ) sunspot group data during the period of 1874 - 2011 and determined variations in the annual numbers ( counts ) of the small, large and big sunspot groups ( these classifications are made on the basis of the maximum areas of the sunspot groups ). we found that the amplitude of an even - numbered cycle of the number of large groups is smaller than that of its immediately following odd - numbered cycle. this is consistent with the well known gnevyshev and ohl rule or g - o rule of solar cycles, generally described by using the zurich sunspot number ( rz ). during cycles 12 - 21 the g - o rule holds good for the variation in the number of small groups also, but it is violated by cycle pair ( 22, 23 ) as in the case of rz. this behaviour of the variations in the small groups is largely responsible for the anomalous behaviour of rz in cycle pair ( 22, 23 ). it is also found that the amplitude of an odd - numbered cycle of the number of small groups is larger than that of its immediately following even - numbered cycle. this can be called as ` reverse g - o rule '. in the case of the number of the big groups, both cycle pairs ( 12, 13 ) and ( 22, 23 ) violated the g - o rule. in many cycles the positions of the peaks of the small, large, and big groups are different and considerably differ with respect to the corresponding positions of the rz peaks. in the case of cycle 23, the corresponding cycles of the small and large groups are largely symmetric / less asymmetric ( waldmeier effect is weak / absent ) with their maxima taking place two years later than that of rz. the corresponding cycle of the big groups is more asymmetric ( strong waldmeier effect ) with its maximum epoch taking place at the same time as that of rz.
|
arxiv:1208.2862
|
we demonstrate that the method of coupled gaussian wave packets is a full - fledged alternative to direct numerical solutions of the gross - pitaevskii equation of condensates with electromagnetically induced attractive 1 / r interaction, or with dipole - dipole interaction. moreover, gaussian wave packets are superior in that they are capable of producing both stable and unstable stationary solutions, and thus of giving access to yet unexplored regions of the space of solutions of the gross - pitaevskii equation. we apply the method to clarify the theoretical nature of the collapse mechanism of blood - cell shaped dipolar condensates : on the route to collapse the condensate passes through a pitchfork bifurcation, where the ground state itself turns unstable, before it finally vanishes in a tangent bifurcation.
|
arxiv:1001.1253
|
we propose a construction for joint feature learning and clustering of multichannel extracellular electrophysiological data across multiple recording periods for action potential detection and discrimination ( " spike sorting " ). our construction improves over the previous state - of - the art principally in four ways. first, via sharing information across channels, we can better distinguish between single - unit spikes and artifacts. second, our proposed " focused mixture model " ( fmm ) elegantly deals with units appearing, disappearing, or reappearing over multiple recording days, an important consideration for any chronic experiment. third, by jointly learning features and clusters, we improve performance over previous attempts that proceeded via a two - stage ( " frequentist " ) learning process. fourth, by directly modeling spike rate, we improve detection of sparsely spiking neurons. moreover, our bayesian construction seamlessly handles missing data. we present state - of - the - art performance without requiring manually tuning of many hyper - parameters on both a public dataset with partial ground truth and a new experimental dataset.
|
arxiv:1304.0542
|
for links with vanishing pairwise linking numbers, the link components bound pairwise disjoint surfaces in $ b ^ { 4 } $. in this paper, we describe the set of genera of such surfaces in terms of the $ h $ - function, which is a link invariant from heegaard floer homology. in particular, we use the $ h $ - function to give lower bounds for the 4 - genus of the link. for $ l $ - space links, the $ h $ - function is explicitly determined by alexander polynomials of the link and sublinks. we show some $ l $ - space links where the lower bounds are sharp, and also describe all possible genera of disjoint surfaces bounded by such links.
|
arxiv:1805.02122
|
graph clustering is an important technique to understand the relationships between the vertices in a big graph. in this paper, we propose a novel random - walk - based graph clustering method. the proposed method restricts the reach of the walking agent using an inflation function and a normalization function. we analyze the behavior of the limited random walk procedure and propose a novel algorithm for both global and local graph clustering problems. previous random - walk - based algorithms depend on the chosen fitness function to find the clusters around a seed vertex. the proposed algorithm tackles the problem in an entirely different manner. we use the limited random walk procedure to find attracting vertices in a graph and use them as features to cluster the vertices. according to the experimental results on the simulated graph data and the real - world big graph data, the proposed method is superior to the state - of - the - art methods in solving graph clustering problems. since the proposed method uses the embarrassingly parallel paradigm, it can be efficiently implemented and embedded in any parallel computing environment such as a mapreduce framework. given enough computing resources, we are capable of clustering graphs with millions of vertices and hundreds millions of edges in a reasonable time.
|
arxiv:1606.06450
|
the polymorphic rpc calculus allows programmers to write succinct multitier programs using polymorphic location constructs. however, until now it lacked an implementation. we develop an experimental programming language based on the polymorphic rpc calculus. we introduce a polymorphic client - server ( cs ) calculus with the client and server parts separated. in contrast to existing untyped cs calculi, our calculus is not only able to resolve polymorphic locations statically, but it is also able to do so dynamically. we design a type - based slicing compilation of the polymorphic rpc calculus into this cs calculus, proving type and semantic correctness. we propose a method to erase types unnecessary for execution but retaining locations at runtime by translating the polymorphic cs calculus into an untyped cs calculus, proving semantic correctness.
|
arxiv:2107.10793
|
a branching process in a markovian environment consists of an irreducible markov chain on a set of " environments " together with an offspring distribution for each environment. at each time step the chain transitions to a new random environment, and one individual is replaced by a random number of offspring whose distribution depends on the new environment. we give a first moment condition that determines whether this process survives forever with positive probability. on the event of survival we prove a law of large numbers and a central limit theorem for the population size. we also define a matrix - valued generating function for which the extinction matrix ( whose entries are the probability of extinction in state j given that the initial state is i ) is a fixed point, and we prove that iterates of the generating function starting with the zero matrix converge to the extinction matrix.
|
arxiv:2106.11249
|
we construct relational observables in group field theory ( gft ) in terms of covariant positive operator - valued measures ( povms ), using techniques developed in the context of quantum reference frames. we focus on matter quantum reference frames ; this can be generalized to other types of frames within the same povm - based framework. the resulting family of relational observables provides a covariant framework to extract localized observables from gft, which is typically defined in a perspective - neutral way. then, we compare this formalism with previous proposals for relational observables in gft. we find that our quantum reference frame - based relational observables overcome the intrinsic limitations of previous proposals while reproducing the same continuum limit results concerning expectation values of the number and volume operators on coherent states. nonetheless, there can be important differences for more complex operators, as well as for other types of gft states. finally, we also use a specific class of povms to show how to project states and operators from the more general perspective - neutral gft fock space to a perspective - dependent one where a scalar matter field plays the role of a relational clock.
|
arxiv:2412.14622
|
let $ \ omega $ be a bounded symmetric domain except the two exceptional domains of $ { \ bbb c } ^ n $ and $ \ phi $ a holomorphic self - map of $ \ omega. $ this paper gives a sufficient and necessary condition for the composition operator $ c _ { \ phi } $ induced by $ \ phi $ to be compact on the bloch space $ \ beta ( \ omega ) $.
|
arxiv:math/0504006
|
this paper presents a method for jointly designing the transmitter - receiver pair in a block - by - block communication system that employs ( intra - block ) decision feedback detection. we provide closed - form expressions for transmitter - receiver pairs that simultaneously minimize the arithmetic mean squared error ( mse ) at the decision point ( assuming perfect feedback ), the geometric mse, and the bit error rate of a uniformly bit - loaded system at moderate - to - high signal - to - noise ratios. separate expressions apply for the ` ` zero - forcing ' ' and ` ` minimum mse ' ' ( mmse ) decision feedback structures. in the mmse case, the proposed design also maximizes the gaussian mutual information and suggests that one can approach the capacity of the block transmission system using ( independent instances of ) the same ( gaussian ) code for each element of the block. our simulation studies indicate that the proposed transceivers perform significantly better than standard transceivers, and that they retain their performance advantages in the presence of error propagation.
|
arxiv:cs/0504015
|
let $ \ { f _ \ mu \ } _ { \ mu \ in \ mathbb { d } } $ be a family of automorphisms of $ \ mathbb { c } ^ 2 $ unfolding a generic homoclinic tangency associated to a fixed point $ p $ belonging to a horseshoe. we prove that if the linearized versions of the cantor sets representing the local intersections of the stable and unstable manifolds of $ p $ with the horseshoe have stable intersections, then the set of parameters $ \ mu $ corresponding to automorphisms with persistent tangencies has positive density at $ \ mu = 0 $.
|
arxiv:1912.09548
|
media composed of colliding hard disks ( 2d ) or hard spheres ( 3d ) serve as good approximations for the collective hydrodynamic description of gases, liquids and granular media. in the present study, the compressible hydrodynamics and shock dynamics are studied for a two - dimensional hard - disk medium at both the continuum and discrete particle level descriptions. for the continuum description, closed form analytical expressions for the inviscid hydrodynamic description, shock hugoniot, isentropic exponent and shock jump conditions were obtained using the helfand equation of state. the closed - form analytical solutions permitted us to gain physical insight on the role of the material ' s density on its compressibility, i. e. how the medium compresses under mechanical loadings and sustains wave motion. furthermore, the predictions were found in excellent agreement with calculations using the event driven molecular dynamic method involving 30, 000 particles over the entire range of compressibility spanning the dilute ideal gas and liquid phases. in all cases, it was found that the energy imparted by the piston motion to the thermalized medium behind the propagating shock was quasi - independent of the medium ' s packing fraction, with a correction vanishing with increasing shock mach numbers.
|
arxiv:1108.0879
|
this paper presents interval prediction methodology to address limitations in existing evaluation indicators and improve prediction accuracy and reliability. first, new evaluation indicators are proposed to comprehensively assess interval prediction methods, considering both all - sample and single - sample scenarios. second, a novel pattern - diversity conditional time - series generative adversarial network ( pdctsgan ) is introduced to generate realistic scenarios, enabling a new interval prediction approach based on scenario generation. the pdctsgan model innovatively incorporates modifications to random noise inputs, allowing the generation of pattern - diverse realistic scenarios. these scenarios are further utilized to construct multiple interval patterns with high coverage probability and low average width. the effectiveness of the proposed methodology is demonstrated through comprehensive case studies. the paper concludes by highlighting future research directions to further enhance interval prediction methods.
|
arxiv:2501.08531
|
thus the area of analysis, to purely algebraic properties. emil artin redeveloped galois theory from 1928 through 1942, eliminating the dependency on the primitive element theorem. = = constructing fields = = = = = constructing fields from rings = = = a commutative ring is a set that is equipped with an addition and multiplication operation and satisfies all the axioms of a field, except for the existence of multiplicative inverses a−1. for example, the integers z form a commutative ring, but not a field : the reciprocal of an integer n is not itself an integer, unless n = ±1. in the hierarchy of algebraic structures fields can be characterized as the commutative rings r in which every nonzero element is a unit ( which means every element is invertible ). similarly, fields are the commutative rings with precisely two distinct ideals, ( 0 ) and r. fields are also precisely the commutative rings in which ( 0 ) is the only prime ideal. given a commutative ring r, there are two ways to construct a field related to r, i. e., two ways of modifying r such that all nonzero elements become invertible : forming the field of fractions, and forming residue fields. the field of fractions of z is q, the rationals, while the residue fields of z are the finite fields fp. = = = = field of fractions = = = = given an integral domain r, its field of fractions q ( r ) is built with the fractions of two elements of r exactly as q is constructed from the integers. more precisely, the elements of q ( r ) are the fractions a / b where a and b are in r, and b = 0. two fractions a / b and c / d are equal if and only if ad = bc. the operation on the fractions work exactly as for rational numbers. for example, a b + c d = a d + b c b d. { \ displaystyle { \ frac { a } { b } } + { \ frac { c } { d } } = { \ frac { ad + bc } { bd } }. } it is straightforward to show that, if the ring is an integral domain, the set of the fractions form a field. the field f ( x ) of the rational fractions over a field ( or an integral domain ) f is the field of fractions of the polynomial
|
https://en.wikipedia.org/wiki/Field_(mathematics)
|
despite the advent of autonomous cars, it ' s likely - at least in the near future - that human attention will still maintain a central role as a guarantee in terms of legal responsibility during the driving task. in this paper we study the dynamics of the driver ' s gaze and use it as a proxy to understand related attentional mechanisms. first, we build our analysis upon two questions : where and what the driver is looking at? second, we model the driver ' s gaze by training a coarse - to - fine convolutional network on short sequences extracted from the dr ( eye ) ve dataset. experimental comparison against different baselines reveal that the driver ' s gaze can indeed be learnt to some extent, despite i ) being highly subjective and ii ) having only one driver ' s gaze available for each sequence due to the irreproducibility of the scene. eventually, we advocate for a new assisted driving paradigm which suggests to the driver, with no intervention, where she should focus her attention.
|
arxiv:1611.08215
|
names : authors list ( link ) medical engineering stories in the news school of engineering and materials science, queen mary university of london = = external links = = ebme website ebme website for medical, biomedical, and clinical engineering professionals.
|
https://en.wikipedia.org/wiki/Clinical_engineering
|
the ultrametric skeleton theorem [ mendel, naor 2013 ] implies, among other things, the following nonlinear dvoretzky - type theorem for hausdorff dimension : for any $ 0 < \ beta < \ alpha $, any compact metric space $ x $ of hausdorff dimension $ \ alpha $ contains a subset which is bilipschitz equivalent to an ultrametric and has hausdorff dimension at least $ \ beta $. in this note we present a simple proof of the ultrametric skeleton theorem in doubling spaces using bartal ' s ramsey decompositions [ bartal 2021 ]. the same general approach is also used to answer a question of zindulka [ zindulka 2020 ] about the existence of " nearly ultrametric " subsets of compact spaces having full hausdorff dimension.
|
arxiv:2104.11944
|
we report the observation of channel - width dependent enhancement in nanoscale field effect transistors containing lithographically - patterned silicon nanowires as the conduction channel. these devices behave as conventional metal - oxide - semiconductor field - effect transistors in reverse source drain bias. reduction of nanowire width below 200 nm leads to dramatic change in the threshold voltage. due to increased surface - to - volume ratio, these devices show higher transconductance per unit width at smaller width. our devices with nanoscale channel width demonstrate extreme sensitivity to surface field profile, and therefore can be used as logic elements in computation and as ultrasensitive sensors of surface - charge in chemical and biological species.
|
arxiv:0802.2140
|
the use of nuclear emulsions in very large physics experiments is now possible thanks to the recent improvements in the industrial production of emulsions and to the development of fast automated microscopes. in this paper the hardware performances of the european scanning system ( ess ) are described. the ess is a very fast automatic system developed for the mass scanning of the emulsions of the opera experiment, which requires microscopes with scanning speeds of about 20 cm ^ 2 / h in an emulsion volume of 44 micron thickness.
|
arxiv:physics/0604043
|
the scalable, low overhead attributes of peer - to - peer ( p2p ) internet protocols and networks lend themselves well to being exploited by criminals to execute a large range of cybercrimes. the types of crimes aided by p2p technology include copyright infringement, sharing of illicit images of children, fraud, hacking / cracking, denial of service attacks and virus / malware propagation through the use of a variety of worms, botnets, malware, viruses and p2p file sharing. this project is focused on study of active p2p nodes along with the analysis of the undocumented communication methods employed in many of these large unstructured networks. this is achieved through the design and implementation of an efficient p2p monitoring and crawling toolset. the requirement for investigating p2p based systems is not limited to the more obvious cybercrimes listed above, as many legitimate p2p based applications may also be pertinent to a digital forensic investigation, e. g, voice over ip, instant messaging, etc. investigating these networks has become increasingly difficult due to the broad range of network topologies and the ever increasing and evolving range of p2p based applications. in this work we introduce the universal p2p network investigation framework ( up2pnif ), a framework which enables significantly faster and less labour intensive investigation of newly discovered p2p networks through the exploitation of the commonalities in p2p network functionality. in combination with a reference database of known network characteristics, it is envisioned that any known p2p network can be instantly investigated using the framework, which can intelligently determine the best investigation methodology and greatly expedite the evidence gathering process. a proof of concept tool was developed for conducting investigations on the bittorrent network.
|
arxiv:1712.03455
|
for models of gravity coupled to hyperbolic sigma models, such as the metric - scalar sector of iib supergravity, we show how smooth trajectories in the ` augmented target space ' connect flrw cosmologies to non - extremal d - instantons through a cosmological singularity. in particular, we find closed cyclic universes that undergo an endless sequence of big - bang to big - crunch cycles separated by instanton ` phases '. we also find ` big - bounce ' universes in which a collapsing closed universe bounces off its cosmological singularity to become an open expanding universe.
|
arxiv:hep-th/0504011
|
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.