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0709.0500
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we describe a formalism to calculate form factor and charge density distribution of the pion in the chiral limit using the holographic dual model of qcd with hard - wall cutoff . we introduce two conjugate pion wave functions and present analytic expressions for these functions and for the pion form factor . they allow to relate such observables as the pion decay constant and the pion charge electric radius to the values of chiral condensate and hard - wall cutoff scale . the evolution of the pion form factor to large values of the momentum transfer is discussed , and results are compared to existing experimental data .
| 109
|
1009.1617
|
we present a new assessment of the ability of infrared dark clouds ( irdcs ) to form massive stars and clusters . this is done by comparison with an empirical mass - size threshold for massive star formation ( msf ) . we establish @xmath0 as a novel approximate msf limit , based on clouds with and without msf . many irdcs , if not most , fall short of this threshold . without significant evolution , such clouds are unlikely msf candidates . this provides a first quantitative assessment of the small number of irdcs evolving towards msf . irdcs below this limit might still form stars and clusters of up to intermediate mass , though ( like , e.g. , the ophiuchus and perseus molecular clouds ) . nevertheless , a major fraction of the mass contained in irdcs might reside in few @xmath1 clouds sustaining msf .
| 150
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physics0411176
|
the propagation of ultracold atomic gases through abruptly changing waveguide potentials is examined in the limit of non - interacting atoms . time - independent scattering calculations of microstructured waveguides with discontinuous changes in the transverse harmonic binding potentials are used to mimic waveguide perturbations and imperfections . three basic configurations are examined : step - like , barrier - like and well - like with waves incident in the ground mode . at low energies , the spectra rapidly depart from single - moded , with significant transmission and reflection of excited modes . the high - energy limit sees @xmath0 transmission , with the distribution of the transmitted modes determined simply by the overlap of the mode wave functions and interference .
| 124
|
1603.08299
|
models where dark matter and dark energy interact with each other have been proposed to solve the coincidence problem . we review the motivations underlying the need to introduce such interaction , its influence on the background dynamics and how it modifies the evolution of linear perturbations . we test models using the most recent observational data and we find that the interaction is compatible with the current astronomical and cosmological data . finally , we describe the forthcoming data sets from current and future facilities that are being constructed or designed that will allow a clearer understanding of the physics of the dark sector .
| 106
|
nucl-th9509006
|
the convergence of the perturbation expansion for the effective interaction to be used in shell - model calculations is investigated as function of the mass number @xmath0 , from @xmath1 to @xmath2 . as the mass number increases , there are more intermediate states to sum over in each higher - order diagram which contributes to the effective interaction . together with the fact that the energy denominators in each diagram are smaller for larger mass numbers , these two effects could largely enhance higher - order contributions to the effective interaction , thereby deteriorating the order - by - order convergence of the effective interaction . this effect is counterbalanced by the short range of the nucleon - nucleon interaction , which implies that its matrix elements are weaker for valence single - particle states in `` large '' nuclei with large mass number as compared to those in light nuclei . these effects are examined by comparing various mean values of the matrix elements . it turns out that the contributions from higher - order terms remain fairly stable as the mass number increases from @xmath1 to @xmath2 . the implications for nuclear structure calculations are discussed .
| 200
|
1112.5263
|
recent discussion on the possibility to obtain more stringent bounds on neutrino magnetic moment has stimulated new interest to possible effects induced by neutrino magnetic moment . in particular , in this note after a short review on neutrino magnetic moment we re - examine the effect of plasmon mass on neutrino spin light radiation in dense matter . we track the entry of the plasmon mass quantity in process characteristics and found out that the most substantial role it plays is the formation of the process threshold . it is shown that far from this point the plasmon mass can be omitted in all the corresponding physical quantities and one can rely on the results of massless photon spin light radiation theory in matter . [ 1999/12/01 v1.4c il nuovo cimento ]
| 133
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1203.5992
|
we test the recent claim by hu et al . ( 2008 ) that feii emission in type 1 agn shows a systematic redshift relative to the local source rest frame and broad - line h@xmath0 . we compile high s / n median composites using sdss spectra from both the hu et al . sample and our own sample of the 469 brightest dr5 spectra . our composites are generated in bins of fwhm h@xmath0 and feii strength as defined in our 4d eigenvector 1 ( 4de1 ) formalism . we find no evidence for a systematic feii redshift and consistency with previous assumptions that feii shift and width ( fwhm ) follow h@xmath0 shift and fwhm in virtually all sources . this result is consistent with the hypothesis that feii emission ( quasi - ubiquitous in type 1 sources ) arises from a broad - line region with geometry and kinematics the same as that producing the balmer lines .
| 162
|
cond-mat9702221
|
we present an exact diagonalization study of the single particle spectral function in the 1d and 2d @xmath0@xmath1@xmath2 model . by studying the scaling properties with @xmath2 and @xmath0 we find a simple building pattern in 1d and show that every spectral feature can be uniquely assigned by a spinon and holon momentum . we find two types of low energy excitations : a band with energy scale @xmath2 and high spectral weight disperses upwards in the interior part of the brillouin zone and reaches @xmath3 at @xmath4 , and a band with energy scale @xmath0 and low spectral weight disperses downwards in the outer part of the zone , touching @xmath3 at @xmath5 . an analogous analysis of the 2d case at half filling shows that the @xmath0-band exists also in this case , but is diffuse and never reaches the fermi energy . for the doped case in 2d the picture is more reminiscent of 1d , in particular the ` main - band ' with a dispersion @xmath6 and the ` shadow band ' with energy scale @xmath0 can be identified also in this case . this leads us to propose that the shadow bands discovered by aebi _ et al . _ in bi2212 are the 2d analogue of the @xmath5 singularity in 1d systems and unrelated to antiferromagnetic spin fluctuations . 2
| 227
|
1005.4315
|
we reexamine the randall - sundrum ( rs ) model with enlarged gauge symmetry @xmath0 in the presence of a brane - localized higgs sector . in contrast to the existing literature , we perform the kaluza - klein ( kk ) decomposition within the mass basis , which avoids the truncation of the kk towers . expanding the low - energy spectrum as well as the gauge couplings in powers of the higgs vacuum expectation value , we obtain analytic formulas which allow for a deep understanding of the model - specific protection mechanisms of the @xmath1 parameter and the left - handed @xmath2-boson couplings . in particular , in the latter case we explain which contributions escape protection and identify them with the irreducible sources of @xmath3 symmetry breaking . we furthermore show explicitly that no protection mechanism is present in the charged - current sector confirming existing model - independent findings . the main focus of the phenomenological part of our work is a detailed discussion of higgs - boson couplings and their impact on physics at the cern large hadron collider . for the first time , a complete one - loop calculation of all relevant higgs - boson production and decay channels is presented , incorporating the effects stemming from the extended electroweak gauge - boson and fermion sectors . mz - th/10 - 18 + may 23 , 2010 + * the custodial randall - sundrum model : + from precision tests to higgs physics * s. casagrande@xmath4 , f. goertz@xmath5 , u. haisch@xmath5 , m. neubert@xmath6 and t. pfoh@xmath5 +
| 267
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1109.3911
|
from social networks to p2p systems , network sampling arises in many settings . we present a detailed study on the nature of biases in network sampling strategies to shed light on how best to sample from networks . we investigate connections between specific biases and various measures of structural representativeness . we show that certain biases are , in fact , beneficial for many applications , as they `` push '' the sampling process towards inclusion of desired properties . finally , we describe how these sampling biases can be exploited in several , real - world applications including disease outbreak detection and market research . [ data mining ]
| 111
|
1608.05513
|
recently , a multi - level fuzzy min max neural network ( mlf ) was proposed , which improves the classification accuracy by handling an overlapped region ( area of confusion ) with the help of a tree structure . in this brief , an extension of mlf is proposed which defines a new boundary region , where the previously proposed methods mark decisions with less confidence and hence misclassification is more frequent . a methodology to classify patterns more accurately is presented . our work enhances the testing procedure by means of data centroids . we exhibit an illustrative example , clearly highlighting the advantage of our approach . results on standard datasets are also presented to evidentially prove a consistent improvement in the classification rate . hyperbox , fuzzy min - max , data centroids , neural networks , neurofuzzy , classification , machine learning .
| 148
|
1406.3796
|
we define the anti - forcing number of a perfect matching @xmath0 of a graph @xmath1 as the minimal number of edges of @xmath1 whose deletion results in a subgraph with a unique perfect matching @xmath0 , denoted by @xmath2 . the anti - forcing number of a graph proposed by vukievi and trinajsti in kekul structures of molecular graphs is in fact the minimum anti - forcing number of perfect matchings . for plane bipartite graph @xmath1 with a perfect matching @xmath0 , we obtain a minimax result : @xmath2 equals the maximal number of @xmath0-alternating cycles of @xmath1 where any two either are disjoint or intersect only at edges in @xmath0 . for a hexagonal system @xmath3 , we show that the maximum anti - forcing number of @xmath3 equals the fries number of @xmath3 . as a consequence , we have that the fries number of @xmath3 is between the clar number of @xmath3 and twice . further , some extremal graphs are discussed . * keywords : * graph ; hexagonal system ; perfect matching ; forcing number ; anti - forcing number ; fries number .
| 191
|
0704.1374
|
we analyse star formation in the nuclei of 9 seyfert galaxies at spatial resolutions down to 0.085 , corresponding to length scales of order 10pc in most objects . our data were taken mostly with the near infrared adaptive optics integral field spectrograph sinfoni . the stellar light profiles typically have size scales of a few tens of parsecs . in two cases there is unambiguous kinematic evidence for stellar disks on these scales . in the nuclear regions there appear to have been recent but no longer active starbursts in the last 10 - 300myr . the stellar luminosity is less than a few percent of the agn in the central 10pc , whereas on kiloparsec scales the luminosities are comparable . the surface stellar luminosity density follows a similar trend in all the objects , increasing steadily at smaller radii up to @xmath0l@xmath1kpc@xmath2 in the central few parsecs , where the mass surface density exceeds 10@xmath3m@xmath1pc@xmath2 . the intense starbursts were probably eddington limited and hence inevitably short - lived , implying that the starbursts occur in multiple short bursts . the data hint at a delay of 50100myr between the onset of star formation and subsequent fuelling of the black hole . we discuss whether this may be a consequence of the role that stellar ejecta could play in fuelling the black hole . while a significant mass is ejected by ob winds and supernovae , their high velocity means that very little of it can be accreted . on the other hand winds from agb stars ultimately dominate the total mass loss , and they can also be accreted very efficiently because of their slow speeds .
| 281
|
astro-ph0506212
|
we have developed a new , very efficient numerical scheme to solve the cr diffusion convection equation that can be applied to the study of the nonlinear time evolution of cr modified shocks for arbitrary spatial diffusion properties . the efficiency of the scheme derives from its use of coarse - grained finite momentum volumes . this approach has enabled us , using @xmath0 momentum bins spanning nine orders of magnitude in momentum , to carry out simulations that agree well with results from simulations of modified shocks carried out with our conventional finite difference scheme requiring more than an order of magnitude more momentum points . the coarse - grained , cgmv scheme reduces execution times by a factor approximately half the ratio of momentum bins used in the two methods . depending on the momentum dependence of the diffusion , additional economies in required spatial and time resolution can be utilized in the cgmv scheme , as well . these allow a computational speed - up of at least an order of magnitude in some cases . ,
| 180
|
1207.2023
|
we have presented dynamic phase transition features and stationary - state behavior of a ferrimagnetic small nanoparticle system with a core - shell structure . by means of detailed monte carlo simulations , a complete picture of the phase diagrams and magnetization profiles have been presented and the conditions for the occurrence of a compensation point @xmath0 in the system have been investigated . according to nel nomenclature , the magnetization curves of the particle have been found to obey p - type , n - type and q - type classification schemes under certain conditions . much effort has been devoted to investigation of hysteretic response of the particle and we observed the existence of triple hysteresis loop behavior which originates from the existence of a weak ferromagnetic core coupling @xmath1 , as well as a strong antiferromagnetic interface exchange interaction @xmath2 . most of the calculations have been performed for a particle in the presence of oscillating fields of very high frequencies and high amplitudes in comparison with exchange interactions which resembles a magnetic system under the influence of ultrafast switching fields . particular attention has also been paid on the influence of the particle size on the thermal and magnetic properties , as well as magnetic features such as coercivity , remanence and compensation temperature of the particle . we have found that in the presence of ultrafast switching fields , the particle may exhibit a dynamic phase transition from paramagnetic to a dynamically ordered phase with increasing ferromagnetic shell thickness .
| 255
|
1301.6373
|
we have used high - resolution , hst wfc3/ir , near - infrared imaging to conduct a detailed bulge - disk decomposition of the morphologies of @xmath0 of the most massive ( @xmath1 ) galaxies at @xmath2 in the candels - uds field . we find that , while such massive galaxies at low redshift are generally bulge - dominated , at redshifts @xmath3 they are predominantly mixed bulge+disk systems , and by @xmath4 they are mostly disk - dominated . interestingly , we find that while most of the quiescent galaxies are bulge - dominated , a significant fraction ( @xmath5% ) of the most quiescent galaxies , have disk - dominated morphologies . thus , our results suggest that the physical mechanisms which quench star - formation activity are not simply connected to those responsible for the morphological transformation of massive galaxies .
| 145
|
1312.6342
|
this paper considers @xmath0-graphs in which all vertices have degree 4 or 6 , and studies the question of calculating the genus of nonorientable surfaces into which such graphs may be embedded . in a previous paper @xcite by the authors , the problem of calculating whether a given @xmath0-graph in which all vertices have degree 4 or 6 admits a @xmath1-homologically trivial embedding into a given orientable surface was shown to be equivalent to a problem on matrices . here we extend those results to nonorientable surfaces . the embeddability condition that we obtain yields quadratic - time algorithms to determine whether a @xmath0-graph with all vertices of degree 4 or 6 admits a @xmath1-homologically trivial embedding into the projective plane or into the klein bottle . * keywords : * graph , @xmath0-graph , surface , embedding , genus * ams subject classification : * primary 05c10 ; secondary 57c15 , 57c27
| 154
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1506.04303
|
a coordinated cyber - attack on grid meter readings and breaker statuses can lead to incorrect state estimation that can subsequently destabilize the grid . this paper studies cyber - attacks by an adversary that changes breaker statuses on transmission lines to affect the estimation of the grid topology . the adversary , however , is incapable of changing the value of any meter data and can only block recorded measurements on certain lines from being transmitted to the control center . the proposed framework , with limited resource requirements as compared to standard data attacks , thus extends the scope of cyber - attacks to grids secure from meter corruption . we discuss necessary and sufficient conditions for feasible attacks using a novel graph - coloring based analysis and show that an optimal attack requires breaker status change at only one transmission line . the potency of our attack regime is demonstrated through simulations on ieee test cases .
| 160
|
1310.5840
|
given an n - dimensional natural hamiltonian l on a riemannian or pseudo - riemannian manifold , we call `` extension '' of l the n+1 dimensional hamiltonian @xmath0 with new canonically conjugated coordinates @xmath1 . for suitable l , the functions @xmath2 and @xmath3 can be chosen depending on any natural number m such that h admits an extra polynomial first integral in the momenta of degree m , explicitly determined in the form of the m - th power of a differential operator applied to a certain function of coordinates and momenta . in particular , if l is maximally superintegrable ( ms ) then h is ms also . therefore , the extension procedure allows the creation of new superintegrable systems from old ones . for m=2 , the extra first integral generated by the extension procedure determines a second - order symmetry operator of a laplace - beltrami quantization of h , modified by taking in account the curvature of the configuration manifold . the extension procedure can be applied to several hamiltonian systems , including the three - body calogero and wolfes systems ( without harmonic term ) , the tremblay - turbiner - winternitz system and n - dimensional anisotropic harmonic oscillators . we propose here a short review of the known results of the theory and some previews of new ones .
| 229
|
astro-ph0702691
|
dense cores are the simplest star - forming sites that we know , but despite their simplicity , they still hold a number of mysteries that limit our understanding of how solar - type stars form . alma promises to revolutionize our knowledge of every stage in the life of a core , from the pre - stellar phase to the final disruption by the newly born star . this contribution presents a brief review of the evolution of dense cores and illustrates particular questions that will greatly benefit from the increase in resolution and sensitivity expected from alma .
| 100
|
nucl-th9908088
|
the microcanonical multifragmentation model from [ al . h. raduta and ad . r. raduta , phys . rev . c * 55 * , 1344 ( 1997 ) ; * 56 * , 2059 ( 1997 ) ; * 59 * , 323 ( 1999 ) ] is refined and improved by taking into account the experimental discrete levels for fragments with @xmath0 and by including the stage of sequential decay of the primary excited fragments . the caloric curve is reevaluated and the heat capacity at constant volume curve is represented as a function of excitation energy and temperature . the sequence of equilibrated sources formed in the reactions studied by the aladin group ( @xmath1au+@xmath1au at 600 , 800 and 1000 mev / nucleon bombarding energy ) is deduced by fitting simultaneously the model predicted mean multiplicity of intermediate mass fragments ( @xmath2 ) and charge asymmetry of the two largest fragments ( @xmath3 ) versus bound charge ( @xmath4 ) on the corresponding experimental data . calculated heli isotopic temperature curves as a function of the bound charge are compared with the experimentally deduced ones .
| 190
|
cond-mat0509177
|
the ladder theory , in which the bethe - goldstone equation for the effective potential between two scattering particles plays a central role , is well known for its satisfactory description of the short - range correlations in the homogeneous electron liquid . by solving exactly the bethe - goldstone equation in the limit of large transfer momentum between two scattering particles , we obtain accurate results for the on - top pair - correlation density @xmath0 , in both three dimensions and two dimensions . furthermore , we prove , in general , the ladder theory satisfies the cusp condition for the pair - correlation density @xmath1 at zero distance @xmath2 .
| 113
|
gr-qc9907044
|
it is well known that the late - time behaviour of gravitational collapse is _ dominated _ by an inverse power - law decaying tail . we calculate _ higher - order corrections _ to this power - law behaviour in a spherically symmetric gravitational collapse . the dominant `` contamination '' is shown to die off at late times as @xmath0 . this decay rate is much _ slower _ than has been considered so far . it implies , for instance , that an ` exact ' ( numerical ) determination of the power index to within @xmath1 requires extremely long integration times of order @xmath2 . we show that the leading order fingerprint of the black - hole electric _ charge _ is of order @xmath3 .
| 130
|
0712.2783
|
we present a theoretical study on the orbital magnetism in multilayer graphenes within the effective mass approximation . the hamiltonian and thus susceptibility can be decomposed into contributions from sub - systems equivalent to monolayer or bilayer graphene . the monolayer - type subband exists only in odd layers and exhibits a delta - function susceptibility at @xmath0 . the bilayer - type subband appearing in every layer number gives a singular structure in the vicinity of @xmath0 due to the trigonal warping as well as a logarithmic tail away from @xmath0 . the integral of the susceptibility over energy is approximately given only by the layer number .
| 109
|
nlin0309068
|
it is shown that fractional derivatives of the ( integrated ) invariant measure of the feigenbaum map at the onset of chaos have power - law tails in their cumulative distributions , whose exponents can be related to the spectrum of singularities @xmath0 . this is a new way of characterizing multifractality in dynamical systems , so far applied only to multifractal random functions ( frisch and matsumoto ( _ j . stat . phys . _ * 108*:1181 , 2002 ) ) . the relation between the thermodynamic approach ( vul , sinai and khanin ( _ russian math . surveys _ * 39*:1 , 1984 ) ) and that based on singularities of the invariant measures is also examined . the theory for fractional derivatives is developed from a heuristic point view and tested by very accurate simulations . _ j. stat . phys . in press _ * keywords : * chaotic dynamics , multifractals , thermodynamic formalism .
| 162
|
1004.3454
|
heating mechanisms of the solar corona will be investigated at the high - altitude solar observatory lomnicky peak of the astronomical institute of sas ( slovakia ) using its mid - size lyot coronagraph and post - focal instrument secis provided by astronomical institute of the university of wrocaw ( poland ) . the data will be studied with respect to the energy transport and release responsible for heating the solar corona to temperatures of mega - kelvins . in particular investigations will be focused on detection of possible high - frequency mhd waves in the solar corona . the scientific background of the project , technical details of the secis system modified specially for the lomnicky peak coronagraph , and inspection of the test data are described in the paper .
| 132
|
0901.1379
|
this study presents miscellaneous properties of pseudo - factorials , which are numbers whose recurrence relation is a twisted form of that of usual factorials . these numbers are associated with special elliptic functions , most notably , a dixonian and a weierstra function , which parametrize the fermat cubic curve and are relative to a hexagonal lattice . a continued fraction expansion of the ordinary generating function of pseudo - factorials , first discovered empirically , is established here . this article also provides a characterization of the associated orthogonal polynomials , which appear to form a new family of `` elliptic polynomials '' , as well as various other properties of pseudo - factorials , including a hexagonal lattice sum expression and elementary congruences .
| 127
|
0806.1795
|
an approach is proposed to nuclear pairing at finite temperature and angular momentum , which includes the effects of the quasiparticle - number fluctuation and dynamic coupling to pair vibrations within the self - consistent quasiparticle random - phase approximation . the numerical calculations of pairing gaps , total energies , and heat capacities are carried out within a doubly folded multilevel model as well as several realistic nuclei . the results obtained show that , in the region of moderate and strong couplings , the sharp transition between the superconducting and normal phases is smoothed out , causing a thermal pairing gap , which does not collapse at a critical temperature predicted by the conventional bardeen - cooper - schrieffer s ( bcs ) theory , but has a tail extended to high temperatures . the theory also predicts the appearance of a thermally assisted pairing in hot rotating nuclei .
| 152
|
astro-ph9906037
|
we present observations of the 5@xmath04@xmath1 transition of water vapor _ at 325.15 ghz _ taken with the cso telescope towards orion irc2 . the emission is more extended than that of other molecular species such as ch@xmath2oh . however , it is much less extended than the emission of water vapor at 183.31 ghz reported by cernicharo et al ( 1994 ) . a comparison of the line intensities at 325.15 ghz and 183.31 ghz puts useful constraints on the density and temperature of the emitting regions and allows an estimate of h@xmath3o abundance , x(h@xmath3o ) , of @xmath410@xmath5 in the plateau and @xmath410@xmath6 - 10@xmath7 in the ridge . 21.75 cm -0.5 cm = 20pt ism : molecules ism : individual ( orion irc2 ) line : profiles masers radio lines : ism submillimeter
| 137
|
0804.3776
|
we study a new class of networks , generated by sequences of letters taken from a finite alphabet consisting of @xmath0 letters ( corresponding to @xmath0 types of nodes ) and a fixed set of connectivity rules . recently , it was shown how a binary alphabet might generate threshold nets in a similar fashion [ hagberg et al . , phys . rev . e 74 , 056116 ( 2006 ) ] . just like threshold nets , sequence nets in general possess a modular structure reminiscent of everyday life nets , and are easy to handle analytically ( i.e. , calculate degree distribution , shortest paths , betweenness centrality , etc . ) . exploiting symmetry , we make a full classification of two- and three - letter sequence nets , discovering two new classes of two - letter sequence nets . the new sequence nets retain many of the desirable analytical properties of threshold nets while yielding richer possibilities for the modeling of everyday life complex networks more faithfully .
| 173
|
astro-ph0309394
|
the majority of active galactic nuclei ( agn ) observed by _ xmm - newton _ reveal narrow fe k@xmath0 lines at @xmath1 6.4 kev , due to emission from cold ( neutral ) material . there is an x - ray baldwin effect in type i agn , in that the equivalent width of the line decreases with increasing luminosity , with weighted linear regression giving ew @xmath2 l@xmath3 ( spearman rank probability of @xmath4 99.9 per cent ) . with current instrumental capabilities it is not possible to determine the precise origin for the narrow line , with both the broad line region and putative molecular torus being possibilities . a possible explanation for the x - ray baldwin effect is a decrease in covering factor of the material forming the fluorescence line . [ firstpage ] galaxies : active x - rays : galaxies quasars : emission lines
| 151
|
1109.1532
|
although finding numerically the quasinormal modes of a nonrotating black hole is a well - studied question , the physics of the problem is often hidden behind complicated numerical procedures aimed at avoiding the direct solution of the spectral system in this case . in this article , we use the exact analytical solutions of the regge - wheeler equation and the teukolsky radial equation , written in terms of confluent heun functions . in both cases , we obtain the quasinormal modes numerically from spectral condition written in terms of the heun functions . the frequencies are compared with ones already published by andersson and other authors . a new method of studying the branch cuts in the solutions is presented the epsilon - method . in particular , we prove that the mode @xmath0 is not algebraically special and find its value with more than 6 firm figures of precision for the first time . the stability of that mode is explored using the @xmath1 method , and the results show that this new method provides a natural way of studying the behavior of the modes around the branch cut points .
| 194
|
1308.6069
|
in this paper we discuss bayesian nonconvex penalization for sparse learning problems . we explore a nonparametric formulation for latent shrinkage parameters using subordinators which are one - dimensional lvy processes . we particularly study a family of continuous compound poisson subordinators and a family of discrete compound poisson subordinators . we exemplify four specific subordinators : gamma , poisson , negative binomial and squared bessel subordinators . the laplace exponents of the subordinators are bernstein functions , so they can be used as sparsity - inducing nonconvex penalty functions . we exploit these subordinators in regression problems , yielding a hierarchical model with multiple regularization parameters . we devise ecme ( expectation / conditional maximization either ) algorithms to simultaneously estimate regression coefficients and regularization parameters . the empirical evaluation of simulated data shows that our approach is feasible and effective in high - dimensional data analysis .
| 149
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astro-ph0112125
|
we report on our search for the optical counterparts of the southern hemisphere anomalous x - ray pulsar 1e1048.1 - 5937 and the radio - quiet neutron stars in supernova remnants puppis a , rcw 103 , and pks 1209 - 52 . the observations were carried out with the new mit / cfa magic camera on the magellan - i 6.5 m telescope in chile . we present deep multiband optical images of the x - ray error circles for each of these targets and discuss the resulting candidates and limits . # 1_#1 _ # 1_#1 _ = # 1 1.25 in .125 in .25 in
| 108
|
1506.07573
|
we consider a three - dimensional chaotic system consisting of the suspension of arnold s cat map coupled with a clock via a weak dissipative interaction . we show that the coupled system displays a synchronization phenomenon , in the sense that the relative phase between the suspension flow and the clock locks to a special value , thus making the motion fall onto a lower dimensional attractor . more specifically , we construct the attractive invariant manifold , of dimension smaller than three , using a convergent perturbative expansion . moreover , we compute via convergent series the lyapunov exponents , including notably the central one . the result generalizes a previous construction of the attractive invariant manifold in a similar but simpler model . the main novelty of the current construction relies in the computation of the lyapunov spectrum , which consists of non - trivial analytic exponents . some conjectures about a possible smoothening transition of the attractor as the coupling is increased are also discussed . * _ keywords : _ * partially hyperbolic systems ; anosov systems ; synchronization ; phase - locking ; lyapunov exponents ; fractal attractor ; srb measure ; tree expansion ; perturbation theory .
| 204
|
1607.07038
|
in many analyses in high energy physics , attempts are made to remove the effects of detector smearing in data by techniques referred to as `` unfolding '' histograms , thus obtaining estimates of the true values of histogram bin contents . such unfolded histograms are then compared to theoretical predictions , either to judge the goodness of fit of a theory , or to compare the abilities of two or more theories to describe the data . when doing this , even informally , one is testing hypotheses . however , a more fundamentally sound way to test hypotheses is to smear the theoretical predictions by simulating detector response and then comparing to the data without unfolding ; this is also frequently done in high energy physics , particularly in searches for new physics . one can thus ask : to what extent does hypothesis testing after unfolding data materially reproduce the results obtained from testing by smearing theoretical predictions ? we argue that this `` bottom - line - test '' of unfolding methods should be studied more commonly , in addition to common practices of examining variance and bias of estimates of the true contents of histogram bins . we illustrate bottom - line - tests in a simple toy problem with two hypotheses .
| 218
|
1111.0265
|
here we report our recent study on the spectral energy distribution ( sed ) of the high frequency bllac object mrk421 in different luminosity states . we used a full - fledged @xmath0-minimization procedure instead of more commonly used `` eyeball '' fit to model the observed flux of the source ( from optical to very high energy ) , with a synchrotron - self - compton ( ssc ) emission mechanism . our study shows that the synchrotron power and peak frequency remain constant with varying source activity , and the magnetic field ( @xmath1 ) decreases with the source activity while the break energy of electron spectrum ( @xmath2 ) and the doppler factor ( @xmath3 ) increase . since a lower magnetic field and higher density of electrons result in increased electron - photon scattering efficiency , the compton power increases , so does the total emission .
| 151
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1301.5763
|
trace distance is available to capture the dynamical information of the unital aspect of a quantum process . however , it can not reflect the non - unital part . so , the non - divisibility originated from the non - unital aspect can not be revealed by the corresponding measure based on the trace distance . we provide a measure of non - unital non - markovianity of quantum processes , which is a supplement to breuer - laine - piilo ( blp ) non - markovianity measure . a measure on the degree of the non - unitality is also provided .
| 104
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1703.09979
|
we introduce a microscopic model aimed at describing superconductivity that can possibly exist in the background of a magnetic texture called spin - vortex checkerboard " . this texture was proposed previously as a possible alternative to stripes to interpret the experimental phenomenology of spin and charge modulations in 1/8-doped lanthanum cuprates . the model involves two kinds of interacting fermionic excitations residing in spin - rich and spin - poor regions of the modulated structure . it is a generalization of another model developed earlier for the so - called grid checkerboard " . we present the mean - field solution of the model , from which we obtain model s predictions for the temperature evolution of the superconducting gap , compare these predictions with available experiments on high-@xmath0 cuprate superconductors and find a good overall agreement .
| 139
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gr-qc0602071
|
the motion of free nearby test particles relative to a stable equatorial circular geodesic orbit about a kerr source is investigated . it is shown that the nonlinear generalized jacobi equation can be transformed in this case to an autonomous form . tidal dynamics beyond the critical speed @xmath0 is studied . we show , in particular , that a free test particle vertically launched from the circular orbit parallel or antiparallel to the kerr rotation axis is tidally accelerated if its initial relative speed exceeds @xmath1 . possible applications of our results to high - energy astrophysics are briefly mentioned .
| 102
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1204.1980
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the thermodynamic and transport properties of the unitary fermi gas at finite temperature @xmath0 are governed by a quantum critical point at @xmath1 and zero density . we compute the universal shear viscosity to entropy ratio @xmath2 in the high - temperature quantum critical regime @xmath3 and find that this strongly coupled quantum fluid comes close to perfect fluidity @xmath4 . using a controlled large-@xmath5 expansion we show that already at the first non - trivial order the equation of state and the tan contact density @xmath6 agree well with the most recent experimental measurements and theoretical luttinger - ward and bold diagrammatic monte carlo calculations .
| 107
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cond-mat0703764
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we report on our calculations of the inner - sphere reorganization energy and the interaction of the @xmath0 orbitals within dna oligomers . the exponential decrease of the electronic coupling between the highest and second highest occupied base orbitals of the intrastrand nucleobases in the ( a - t)@xmath1 and ( g - c)@xmath1 oligomers have been found with an increase of the sequence number @xmath2 in the dna structure . we conclude that for realistic estimation of the electronic coupling values between the nucleobases within the dna molecule , a dna chain containing at least four base pairs is required . we estimate the geometry relaxation of the base pairs within the ( a - t)@xmath1 and ( g - c)@xmath1 oligomers ( @xmath3 ) due to their oxidation . the decrease of the inner - sphere reorganization energy with elongation of the oligomer structure participating in the oxidation process have been observed . the maximum degree of geometry relaxation of the nucleobase structures and correspondingly the higher charge density in the oxidized state are found to be located close to the oligomer center . = 1.5truecm
| 188
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cond-mat0410006
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we report the observation and systematic investigation of the space charge effect and mirror charge effect in photoemission spectroscopy . when pulsed light is incident on a sample , the photoemitted electrons experience energy redistribution after escaping from the surface because of the coulomb interaction between them ( space charge effect ) and between photoemitted electrons and the distribution of mirror charges in the sample ( mirror charge effect ) . these combined coulomb interaction effects give rise to an energy shift and a broadening which can be on the order of 10 mev for a typical third - generation synchrotron light source . this value is comparable to many fundamental physical parameters actively studied by photoemission spectroscopy and should be taken seriously in interpreting photoemission data and in designing next generation experiments . key words : space charge , mirror charge , photoemission , fermi level shift , fermi level broadening .
| 153
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astro-ph9808110
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we present the results of a new calculation of the photodisintegration of ultrahigh energy cosmic - ray ( uhcr ) nuclei in intergalactic space . the critical interactions for energy loss and photodisintegration of uhcr nuclei occur with photons of the 2.73 k cosmic background radiation ( cbr ) and with photons of the infrared background radiation ( ibr ) . we have reexamined this problem making use of a new determination of the ibr based on empirical data , primarily from iras galaxies , consistent with direct measurements and upper limits from tev @xmath0-ray observations . we have also improved the calculation by including the specific threshold energies for the various photodisintegration interactions in our monte carlo calculation . with the new smaller ibr flux , the steepness of the wien side of the now relatively more important cbr makes their inclusion essential for more accurate results . our results indicate a significant increase in the propagation time of uhcr nuclei of a given energy over previous results . we discuss the possible significance of this for uhcr origin theory . # 1#23.6pt
| 184
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1612.03848
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quantum systems out of equilibrium are now a subject of intensive research both in theoretical and experimental physics . in this paper we study periodically modulated quantum systems which are in contact with a stationary environment . within the framework of lindblad quantum master equation , the asymptotic states of such systems are described by time - periodic density operators . resolution of these operators is a non - trivial computational task . approaches based on spectral and iterative methods are restricted to systems with the dimension of the hosting hilbert space @xmath0 , while the direct long - time integration of the master equation becomes problematic for @xmath1 . to overcome these limitations we use the quantum trajectory method which unravels the deterministic master equation for the density operator into a set of stochastic processes for wave functions . this method avoids calculations of the kernel of the floquet superoperator ; instead the asymptotic density matrix is calculated by performing a statistical sampling preceded by a long transient propagation . we present a high - accuracy realization of this idea based on exponential propagators combined with a time - stepping technique . employing a scalable model of interacting bosons hoping over a dimer , we test the performance of the algorithm on a supercomputer . we demonstrate that the algorithm allows to resolve non - equilibrium asymptotic states of model systems with @xmath2 on a small computer cluster thus reaching the scale on which numerical studies of isolated periodically - modulated systems are currently performed . open quantum systems , lindblad equation , periodic modulations , quantum trajectories
| 269
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0712.4255
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the point sets of all known optimal rectilinear drawings of @xmath0 share an unmistakeable clustering property , the so called _ 3decomposability_. it is widely believed that the underlying point sets of all optimal rectilinear drawings of @xmath0 are @xmath1decomposable . we give a lower bound for the minimum number of @xmath2sets in a @xmath1decomposable @xmath3point set . as an immediate corollary , we obtain a lower bound for the crossing number @xmath4 of any rectilinear drawing @xmath5 of @xmath0 with underlying @xmath1decomposable point set , namely @xmath6 . this closes this gap between the best known lower and upper bounds for the rectilinear crossing number @xmath7 of @xmath0 by over 40% , under the assumption of @xmath1decomposability .
| 119
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0903.0041
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1-nearest neighbor with the dynamic time warping ( dtw ) distance is one of the most effective classifiers on time series domain . since the global constraint has been introduced in speech community , many global constraint models have been proposed including sakoe - chiba ( s - c ) band , itakura parallelogram , and ratanamahatana - keogh ( r - k ) band . the r - k band is a general global constraint model that can represent any global constraints with arbitrary shape and size effectively . however , we need a good learning algorithm to discover the most suitable set of r - k bands , and the current r - k band learning algorithm still suffers from an overfitting phenomenon . in this paper , we propose two new learning algorithms , i.e. , band boundary extraction algorithm and iterative learning algorithm . the band boundary extraction is calculated from the bound of all possible warping paths in each class , and the iterative learning is adjusted from the original r - k band learning . we also use a silhouette index , a well - known clustering validation technique , as a heuristic function , and the lower bound function , lb_keogh , to enhance the prediction speed . twenty datasets , from the workshop and challenge on time series classification , held in conjunction of the sigkdd 2007 , are used to evaluate our approach .
| 243
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cond-mat0110219
|
spin and chirality orderings of the three - dimensional heisenberg spin glass under magnetic fields are studied by large - scale equilibrium monte carlo simulations . it is found that the chiral - glass transition and the chiral - glass ordered state , which are essentially of the same character as their zero - field counterparts , occur under magnetic fields . the chiral - glass ordered state exhibits a one - step - like peculiar replica - symmetry breaking in the chiral sector , while it does not accompany the spin - glass order perpendicular to the applied field . critical perperties of the chiral - glass transition are different from those of the standard ising spin glass . magnetic phase diagram of the model is constructed , which reveals that the chiral - glass state is quite robust against magnetic fields . the chiral - glass transition line has a character of the gabay - toulouse line of the mean - field model , yet its physical origin being entirely different . these numerical results are discussed in light of the recently developed spin - chirality decoupling - recoupling scenario . implication to experimental phase diagram is also discussed .
| 202
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1603.09730
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we present a method for rejecting competing models from noisy time - course data that does not rely on parameter inference . first we characterize ordinary differential equation models in only measurable variables using differential algebra elimination . next we extract additional information from the given data using gaussian process regression ( gpr ) and then transform the differential invariants . we develop a test using linear algebra and statistics to reject transformed models with the given data in a parameter - free manner . this algorithm exploits the information about transients that is encoded in the model s structure . we demonstrate the power of this approach by discriminating between different models from mathematical biology . keywords : model selection , differential algebra , algebraic statistics , mathematical biology
| 130
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0903.1636
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using a high resolution hydrodynamical cosmological simulation of the formation of a massive spheroidal galaxy we show that elliptical galaxies can be very compact and massive at high redshift in agreement with recent observations . accretion of stripped in - falling stellar material increases the size of the system with time and the central concentration is reduced by dynamical friction of the surviving stellar cores . in a specific case of a spheroidal galaxy with a final stellar mass of @xmath0 we find that the effective radius @xmath1 increases from @xmath2 at z = 3 to @xmath3 at z = 0 with a concomitant decrease in the effective density of an order of magnitude and a decrease of the central velocity dispersion by approximately 20% over this time interval . a simple argument based on the virial theorem shows that during the accretion of weakly bound material ( minor mergers ) the radius can increase as the square of the mass in contrast to the usual linear rate of increase for major mergers . by undergoing minor mergers compact high redshift spheroids can evolve into present - day systems with sizes and concentrations similar to observed local ellipticals . this indicates that minor mergers may be the main driver for the late evolution of sizes and densities of early - type galaxies .
| 223
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nucl-ex9911003
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the reaction @xmath0 was measured at the mainz microtron mami at an invariant mass of @xmath1 and four - momentum transfers of @xmath2 , @xmath3 and @xmath4 . for each value of @xmath5 , a rosenbluth separation of the transverse and longitudinal cross sections was performed . an effective lagrangian model was used to extract the ` axial mass ' from experimental data . we find a value of @xmath6 which is @xmath7 larger than the axial mass known from neutrino scattering experiments . this is consistent with recent calculations in chiral perturbation theory . , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , and _ pacs : _ 13.60.le , 25.30.rw , 14.20.dh _ keywords : _ nucleon axial form factor , coincident pion electroproduction
| 149
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1605.00661
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previous studies have shown that _ wise_-selected hyperluminous , hot dust - obscured galaxies ( hot dogs ) are powered by highly dust - obscured , possibly compton - thick agns . high obscuration provides us a good chance to study the host morphology of the most luminous agns directly . we analyze the host morphology of 18 hot dogs at @xmath0 using hubble space telescope / wfc3 imaging . we find that hot dogs have a high merger fraction ( @xmath1 ) . by fitting the surface brightness profiles , we find that the distribution of srsic indices in our hot dog sample peaks around 2 , which suggests that most of hot dogs have transforming morphologies . we also derive the agn bolometric luminosity ( @xmath2 ) of our hot dog sample by using ir seds decomposition . the derived merger fraction and agn bolometric luminosity relation is well consistent with the variability - based model prediction @xcite . both the high merger fraction in ir - luminous agn sample and relatively low merger fraction in uv / optical - selected , unobscured agn sample can be expected in the merger - driven evolutionary model . finally , we conclude that hot dogs are merger - driven and may represent a transit phase during the evolution of massive galaxies , transforming from the dusty starburst dominated phase to the unobscured qso phase .
| 235
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nucl-th0306012
|
adequate description of electro and gamma nuclear physics is of utmost importance in studies of electron beam - dumps and intense electron beam accelerators . i also is mandatory to describe neutron backgrounds and activation in linear colliders . this physics was elaborated in geant4 over the last year , and now entered into the stage of practical application . in the geant4 photo - nuclear data base there are at present about 50 nuclei for which the photo - nuclear absorption cross sections have been measured . of these , data on 14 nuclei are used to parametrize the gamma nuclear reaction cross - section the resulting cross section is a complex , factorized function of @xmath0 and @xmath1 , where @xmath2 is the energy of the incident photon . electro - nuclear reactions are so closely connected with photo - nuclear reactions that sometimes they are often called `` photo - nuclear '' . the one - photon exchange mechanism dominates in electro - nuclear reactions , and the electron can be substituted by a flux of photons . folding this flux with the gamma - nuclear cross - section , we arrive at an acceptable description of the electro - nuclear physics . final states in gamma and electro nuclear physics are described using chiral invariant phase - space decay at low gamma or equivalent photon energies , and quark gluon string model at high energies . we will present the modeling of this physics in geant4 , and show results from practical applications .
| 258
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hep-ph0601107
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the attenuation of heavy - flavored particles in nucleus nucleus collisions tests the microscopic dynamics of medium - induced parton energy loss and , in particular , its expected dependence on the identity ( color charge and mass ) of the parent parton . we discuss the comparison of theoretical calculations with recent single - electron data from rhic experiments . then , we present predictions for the heavy - to - light ratios of @xmath0 and @xmath1 mesons at lhc energy . address = universit degli studi di padova and infn , padova , italy address = dep . de fsica de partculas and igfae , universidade de santiago de compostela , spain address = lpthe , universit pierre et marie curie ( paris 6 ) , france address = department of physics , cern , theory division , genve , switzerland address = department of physics and astronomy , university of stony brook , ny , usa
| 159
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cond-mat0402613
|
monte carlo simulations using the newly proposed wang - landau algorithm together with the broad histogram relation are performed to study the antiferromagnetic six - state clock model on the triangular lattice , which is fully frustrated . we confirm the existence of the magnetic ordering belonging to the kosterlitz - thouless ( kt ) type phase transition followed by the chiral ordering which occurs at slightly higher temperature . we also observe the lower temperature phase transition of kt type due to the discrete symmetry of the clock model . by using finite - size scaling analysis , the higher kt temperature @xmath0 and the chiral critical temperature @xmath1 are respectively estimated as @xmath2 and @xmath3 . the results are in favor of the double transition scenario . the lower kt temperature is estimated as @xmath4 . two decay exponents of kt transitions corresponding to higher and lower temperatures are respectively estimated as @xmath5 and @xmath6 , which suggests that the exponents associated with the kt transitions are universal even for the frustrated model .
| 176
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quant-ph0601028
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we propose a technique to prepare coherent superpositions of two nondegenerate quantum states in a three - state ladder system , driven by two simultaneous fields near resonance with an intermediate state . the technique , of potential application to enhancement of nonlinear processes , uses adiabatic passage assisted by dynamic stark shifts induced by a third laser field . the method offers significant advantages over alternative techniques : ( i ) it does not require laser pulses of specific shape and duration and ( ) it requires less intense fields than schemes based on two - photon excitation with non - resonant intermediate states . we discuss possible experimental implementation for enhancement of frequency conversion in mercury atoms .
| 120
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1406.2412
|
we report a detailed nuclear magnetic resonance ( nmr ) study by combined @xmath0na and @xmath1as measurements over a broad range of doping to map the phase diagram of nafe@xmath2co@xmath3as . in the underdoped regime ( @xmath4 0.017 ) , we find a magnetic phase with robust antiferromagnetic ( afm ) order , which we denote the _ s_-afm phase , cohabiting with a phase of weak and possibly proximity - induced afm order ( _ w_-afm ) whose volume fraction @xmath5% is approximately constant . near optimal doping , at @xmath6 , we observe a phase separation between static antiferromagnetism related to the _ s_-afm phase and a paramagnetic ( pm ) phase related to _ w_-afm . the volume fraction of afm phase increases upon cooling , but both the nel temperature and the volume fraction can be suppressed systematically by applying a @xmath7-axis magnetic field . on cooling below @xmath8 , superconductivity occupies the pm region and its volume fraction grows at the expense of the afm phase , demonstrating a phase separation of the two types of order based on volume exclusion . at higher dopings , static antiferromagnetism and even critical afm fluctuations are completely suppressed by superconductivity . thus the phase diagram we establish contains two distinct types of phase separation and reflects a strong competition between afm and superconducting phases both in real space and in momentum space . we suggest that both this strict mutual exclusion and the robustness of superconductivity against magnetism are consequences of the extreme two - dimensionality of nafeas .
| 262
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1307.7160
|
several high - performance lab instruments suitable for manual assembly have been developed using low - pin - count 32-bit microcontrollers that communicate with an android tablet via a usb interface . a single android tablet app accommodates multiple interface needs by uploading parameter lists and graphical data from the microcontrollers , which are themselves programmed with easily - modified c code . the hardware design of the instruments emphasizes low chip counts and is highly modular , relying on small daughter boards `` for special functions such as usb power management , waveform generation , and phase - sensitive signal detection . in one example , a daughter board provides a complete waveform generator and direct digital synthesizer that fits on a 1.5''@xmath00.8 " circuit card .
| 128
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1005.1001
|
we study the entanglement dynamics of two qubits , each of which is embedded into its local amplitude - damping reservoir , and the entanglement distribution among all the bipartite subsystems including qubit - qubit , qubit - reservoir , and reservoir - reservoir . it is found that the entanglement can be stably distributed among all components , which is much different to the result obtained under the born - markovian approximation by c. e. lpez _ et al . _ [ phys . rev . lett . * 101 * , 080503 ( 2008 ) ] , and particularly it also satisfies an identity . our unified treatment includes the previous results as special cases . the result may give help to understand the physical nature of entanglement under decoherence .
| 133
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astro-ph0603119
|
the rosette hh1 jet is a collimated flow immersed in the strong uv radiation field of the rosette nebula . we investigate the physical properties of the rosette hh1 jet using high - quality narrow - band images and high - dispersion spectroscopy . the new images show that the axis of the jet is not precisely aligned with the star near the base of the jet . the high resolution of the spectra allows us to accurately determine the contributions from the region , jet , and star . the appoaching and receding sides of the expanding shell of the rosette nebula are at heliocentric velocities of 13 and 40 km s@xmath0 , while the jet reaches a maximum velocity offset at a heliocentric velocity of @xmath130 km s@xmath0 . the [ ] doublet ratios indicate an electron density of @xmath21000 @xmath3 in the jet and @xmath4100 @xmath3 in the region . with a careful subtraction of the nebular and jet components , we find the stellar h@xmath5 line is dominated by a broad absorption profile with little or no emission component , indicating a lack of substantial circumstellar material . the circumstellar material has most likely been photo - evaporated by the strong uv radiation field in the rosette nebula . the evaporation time scale is 10@xmath6 10@xmath7 yr . the rosette hh1 jet source provides evidence for an accelerated evolution from a ctts to a wtts due to the strong uv radiation field ; therefore , both cttss and wttss can be spatially mixed in regions with massive star formation .
| 264
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1106.4784
|
we report a detection of the excited @xmath0 rotational transition of para- in apm 08279 + 5255 using the iram plateau de bure interferometer . at @xmath1 , this is the highest - redshift detection of interstellar water to date . from lvg modeling , we conclude that this transition is predominantly radiatively pumped and on its own does not provide a good estimate of the water abundance . however , additional water transitions are predicted to be detectable in this source , which would lead to an improved excitation model . we also present a sensitive upper limit for the hf @xmath2 absorption toward apm 08279 + 5255 . while the face - on geometry of this source is not favorable for absorption studies , the lack of hf absorption is still puzzling and may be indicative of a lower fluorine abundance at @xmath1 compared with the galactic ism .
| 151
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1012.4946
|
a huge amount of entropy is produced at places where fresh water and seawater mix , for example at river mouths . this mixing process is a potentially enormous source of sustainable energy , provided it is harnessed properly , for instance by a cyclic charging and discharging process of porous electrodes immersed in salt and fresh water , respectively [ d. brogioli , phys . . lett . * 103 * , 058501 ( 2009 ) ] . here we employ a modified poisson - boltzmann free - energy density functional to calculate the ionic adsorption and desorption onto and from the charged electrodes , from which the electric work of a cycle is deduced . we propose optimal ( most efficient ) cycles for two given salt baths involving two canonical and two grand - canonical ( dis)charging paths , in analogy to the well - known carnot cycle for heat - to - work conversion from two heat baths involving two isothermal and two adiabatic paths . we also suggest a slightly modified cycle which can be applied in cases that the stream of fresh water is limited . + bob evans about water ( 1998 ) . + + bob evans about ionic criticality ( 1998 ) .
| 212
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1012.5922
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using molecular dynamics based on langevin equations with a coordinate- and velocity - dependent damping coefficient , we study the frictional properties of a thin layer of `` soft '' lubricant ( where the interaction within the lubricant is weaker than the lubricant - substrate interaction ) confined between two solids . at low driving velocities the system demonstrates stick - slip motion . the lubricant may or may not be melted during sliding , thus exhibiting either the `` liquid sliding '' ( ls ) or the `` layer over layer sliding '' ( lols ) regimes . the lols regime mainly operates at low sliding velocities . we investigate the dependence of friction properties on the misfit angle between the sliding surfaces and calculate the distribution of static frictional thresholds for a contact of polycrystalline surfaces .
| 139
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1312.5839
|
we consider a gaussian sequence space model @xmath0 where @xmath1 has a diagonal covariance matrix @xmath2 . we consider the situation where the parameter vector @xmath3 is sparse . our goal is to estimate the unknown parameter by a model selection approach . the heterogenous case is much more involved than the direct model . indeed , there is no more symmetry inside the stochastic process that one needs to control since each empirical coefficient has its own variance . the problem and the penalty do not only depend on the number of coefficients that one selects , but also on their position . this appears also in the minimax bounds where the worst coefficients will go to the larger variances . however , with a careful and explicit choice of the penalty we are able to select the correct coefficients and get a sharp non - asymptotic control of the risk of our procedure . some simulation results are provided .
| 162
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astro-ph0508488
|
we present an analysis of the behaviour of the ` coarse - grained ' ( ` mesoscopic ' ) rank partitioning of the mean energy of collections of particles composing virialized dark matter halos in a @xmath0-cdm cosmological simulation . we find evidence that rank preservation depends on halo mass , in the sense that more massive halos show more rank preservation than less massive ones . we find that the most massive halos obey arnold s theorem ( on the ordering of the characteristic frequencies of the system ) more frequently than less massive halos . this method may be useful to evaluate the coarse - graining level ( minimum number of particles per energy cell ) necessary to reasonably measure signatures of ` mesoscopic ' rank orderings in a gravitational system .
| 134
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astro-ph9706294
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the prediction of cross sections for nuclei far off stability is crucial in the field of nuclear astrophysics . in recent calculations the nuclear level density as an important ingredient to the statistical model ( hauser - feshbach ) has shown the highest uncertainties . we present a global parametrization of nuclear level densities within the back - shifted fermi - gas formalism . employment of an energy - dependent level density parameter @xmath0 , based on microscopic corrections from a recent frdm mass formula , and a backshift @xmath1 , based on pairing and shell corrections , leads to a highly improved fit of level densities at the neutron - separation energy in the mass range @xmath2 . the importance of using proper microscopic corrections from mass formulae is emphasized . the resulting level description is well suited for astrophysical applications . the level density can also provide clues to the applicability of the statistical model which is only correct for a high density of excited states . using the above description , one can derive a `` map '' for the applicability of the model to reactions of stable and unstable nuclei with neutral and charged particles .
| 200
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cond-mat0112052
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we introduce and solve a model which considers two coupled networks growing simultaneously . the dynamics of the networks is governed by the new arrival of network elements ( nodes ) making preferential attachments to pre - existing nodes in both networks . the model segregates the links in the networks as intra - links , cross - links and mix - links . the corresponding degree distributions of these links are found to be power - laws with exponents having coupled parameters for intra- and cross - links . in the weak coupling case the model reduces to a simple citation network . as for the strong coupling , it mimics the mechanism of _ the web of human sexual contacts_.
| 122
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astro-ph0112455
|
we present optical spectroscopic identifications of hard x - ray ( 5 - 10 kev ) selected sources belonging to the hellas sample obtained with _ bepposax _ down to a 5 - 10 kev flux limit of @xmath0@xmath1@xmath2 erg @xmath3 s@xmath4 . the sample consists of 118 sources . 25 sources have been identified trough correlations with catalogues of known sources . 49 have been searched for spectroscopic identification at the telescope . 13 fields resulted empty down to r=21 . 37 sources have been identified with type 1 agn and 9 with type 2 agn . the remaining are : 5 narrow emission line galaxies , 6 clusters , 2 bl lac , 1 radio galaxy and 1 star . combining these objects with other hard x - ray selected agns from _ asca _ and _ heao1 _ , we find that the local luminosity function of type 1 agn in the 2 - 10 kev band is fairly well represented by a double - power - law - function . there is evidence for significant cosmological evolution according to a pure luminosity evolution ( ple ) model @xmath5@xmath6@xmath7 , with @xmath8=2.12 and @xmath8=2.22 ( @xmath9@xmath10@xmath11 ) in a ( @xmath12,@xmath13)=(1.0,0.0 ) and in a ( @xmath12,@xmath13)=(0.3,0.7 ) cosmology , respectively . the data show an excess of faint high redshift type 1 agn which is well modeled by a luminosity dependent density evolution ( ldde ) , similarly to what observed in the soft x - rays . however , in both cosmologies , the statistic is not significant enough to distinguish between the ple and ldde models . the fitted models imply a contribution of agn1 to the 2 - 10 kev x - ray background from 35% up to 60% .
| 297
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1601.04235
|
the explosive transition of a massive neutron star to a quark star ( the quark - nova ; qn ) releases in excess of @xmath0 erg in kinetic energy which can drastically impact the surrounding environment of the qn . a qn is triggered when a neutron star gains enough mass to reach the critical value for quark deconfinement to happen in the core . in binaries , a neutron star has access to mass reservoirs ( e.g. accretion from a companion or from a common envelope ; ce ) . we explain observed light - curves of hydrogen - poor superluminous supernovae ( slsne ia ) in the context of a qn occurring in the second ce phase of a massive binary . in particular this model gives good fits to light - curves of slsne with double - humped light - curves . our model suggests the qn as a mechanism for ce ejection and that they be taken into account during binary evolution . in a short period binary with a white dwarf companion , the neutron star can quickly grow in mass and experience a qn event . part of the qn ejecta collides with the white dwarf ; shocking , compressing ; and heating it to driving a thermonuclear runaway producing a sn ia impostor ( a qn - ia ) . unlike `` normal '' type ia supernovae where no compact remnant is formed , a qn - ia produces a quark star undergoing rapid spin - down providing additional power along with the @xmath1ni decay energy . type ia sne are used as standard candles and contamination of this data by qne - ia can infer an incorrect cosmology .
| 287
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astro-ph9910456
|
we present low - state iue spectroscopy of the rosat - discovered polar rxj1313.2@xmath03259 . the swp spectrum displays a broad absorption profile , which can be fitted with a two - temperature model of a white dwarf of @xmath1k with a hot spot of @xmath2k which covers @xmath3 of the white dwarf surface . the white dwarf temperature is atypically low for the long orbital period ( 4.18h ) of rxj1313.2@xmath03259 . this low temperature implies either that the system is a young cv in the process of switching on mass transfer or that it is an older cv found in a prolonged state of low accretion rate , much below that predicted by standard evolution theory . in the first case , we can put a lower limit on the life time as pre - cv of @xmath4yrs . in the second case , the good agreement of the white dwarf temperature with that expected from compressional heating suggests that the system has experienced the current low accretion rate for an extended period @xmath5yrs . a possible explanation for the low accretion rate is that rxj1313.2@xmath03259 is a hibernating post nova and observational tests are suggested .
| 199
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hep-ph0207062
|
we show that exclusive double - diffractive higgs production , @xmath0 , followed by the @xmath1 decay , could play an important role in identifying a ` light ' higgs boson at the lhc , provided that the forward outgoing protons are tagged . we predict the cross sections for the signal and for all possible @xmath2 backgrounds . ippp/02/41 + dcpt/02/82 + 3 july 2002 * forward proton tagging as a way to identify a light higgs boson at the lhc * a.d . martin , v.a . khoze and m.g . ryskin institute for particle physics phenomenology , + university of durham , dh1 3le , uk
| 109
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1410.1612
|
in this article , we study the new q - tensor model previously derived from onsager s molecular theory by han _ et al . _ [ _ arch . rational mech . anal . _ , 215.3 ( 2014 ) , pp . 741 - 809 ] for static liquid crystal modeling . taking density and q - tensor as order parameters , the new q - tensor model not only characterizes important phases while capturing density variation effects , but also remains computationally tractable and efficient . we report the results of two numerical applications of the model , namely the isotropic nematic smectic - a smectic - c phase transitions and the isotropic nematic interface problem , in which density variations are indispensable . meanwhile , we show the connections of the new q - tensor model with classical models including generalized landau - de gennes models , generalized mcmillan models , and the chen - lubensky model . the new q - tensor model is the pivot and an appropriate trade - off between the classical models in three scales . liquid crystals , q - tensor model , density variations , smectic phase , phase transition , isotropic - nematic interface
| 206
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1010.3321
|
we obtain the nuclear proximity potential by using semiclassical extended thomas fermi ( etf ) approach in skyrme energy density formalism ( sedf ) , and use it in the extended @xmath0-summed wong formula under frozen density approximation . this method has the advantage of allowing the use of different skyrme forces , giving different barriers . thus , for a given reaction , we could choose a skyrme force with proper barrier characteristics , not - requiring extra barrier lowering " or barrier narrowing " for a best fit to data . for the @xmath1ni+@xmath2mo reaction , the @xmath0-summed wong formula , with effects of deformations and orientations of nuclei included , fits the fusion - evaporation cross section data exactly for the force gski , requiring additional barrier modifications for forces siii and sv . however , the same for other similar reactions , like @xmath3ni+@xmath3ni , fits the data best for siii force . hence , the barrier modification effects in @xmath0-summed wong expression depends on the choice of skyrme force in extended etf method .
| 179
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1110.5298
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we study non - adiabatic charge pumping through single - level quantum dots taking into account coulomb interactions . we show how a truncated set of equations of motion can be propagated in time by means of an auxiliary - mode expansion . this formalism is capable of treating the time - dependent electronic transport for arbitrary driving parameters . we verify that the proposed method describes very precisely the well - known limit of adiabatic pumping through quantum dots without coulomb interactions . as an example we discuss pumping driven by short voltage pulses for various interaction strengths . such finite pulses are particular suited to investigate transient non - adiabatic effects , which may be also important for periodic drivings , where they are much more difficult to reveal .
| 132
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physics0410160
|
a case study in bifurcation and stability analysis is presented , in which reduced dynamical system modelling yields substantial new global and predictive information about the behaviour of a complex system . the first smooth pathway , free of pathological and persistent degenerate singularities , is surveyed through the parameter space of a nonlinear dynamical model for a gradient - driven , turbulence shear flow energetics in magnetized fusion plasmas . along the route various obstacles and features are identified and treated appropriately . an organizing centre of low codimension is shown to be robust , several trapped singularities are found and released , and domains of hysteresis , threefold stable equilibria , and limit cycles are mapped . characterization of this rich dynamical landscape achieves unification of previous disparate models for plasma confinement transitions , supplies valuable intelligence on the big issue of shear flow suppression of turbulence , and suggests targeted experimental design , control and optimization strategies .
| 161
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0911.3112
|
we present the result of a search for a massive color - octet vector particle , ( e.g. a massive gluon ) decaying to a pair of top quarks in proton - antiproton collisions with a center - of - mass energy of 1.96 tev . this search is based on 1.9 fb@xmath0 of data collected using the cdf detector during run ii of the tevatron at fermilab . we study @xmath1 events in the lepton+jets channel with at least one @xmath2-tagged jet . a massive gluon is characterized by its mass , decay width , and the strength of its coupling to quarks . these parameters are determined according to the observed invariant mass distribution of top quark pairs . we set limits on the massive gluon coupling strength for masses between 400 and 800 gev@xmath3 and width - to - mass ratios between 0.05 and 0.50 . the coupling strength of the hypothetical massive gluon to quarks is consistent with zero within the explored parameter space . massive gluon , top quark 13.85.rm , 14.65.ha , 14.80.-j
| 179
|
0909.1182
|
it is well known that the dark matter dominates the dynamics of galaxies and clusters of galaxies . its constituents remain a mystery despite an assiduous search for them over the past three decades . recent results from the satellite - based pamela experiment detect an excess in the positron fraction at energies between @xmath0 gev in the secondary cosmic ray spectrum . other experiments namely atic , hess and fermi show an excess in the total electron ( ps . + @xmath1 ) spectrum for energies greater 100 gev . these excesses in the positron fraction as well as the electron spectrum could arise in local astrophysical processes like pulsars , or can be attributed to the annihilation of the dark matter particles . the second possibility gives clues to the possible candidates for the dark matter in galaxies and other astrophysical systems . in this article , we give a report of these exciting developments . = 22.8 cm .6 true cm
| 164
|
cond-mat0011308
|
a simple model is presented for the appearance of attraction between two like charged polyions inside a polyelectrolyte solution . the polyions are modeled as rigid cylinders in a continuum dielectric solvent . the strong electrostatic interaction between the polyions and the counterions results in counterion condensation . if the two polyions are sufficiently close to each other their layers of condensed counterions can become correlated resulting in attraction between the macromolecules . to explore the counterion induced attraction we calculate the correlation functions for the condensed counterions . it is found that the correlations are of very short range . for the parameters specific to the double stranded dna , the correlations and the attraction appear only when the surface - to - surface separation is less than @xmath0 . 2
| 132
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1009.6197
|
in this paper , a cognitive relay channel is considered , and amplify - and - forward ( af ) relay beamforming designs in the presence of an eavesdropper and a primary user are studied . our objective is to optimize the performance of the cognitive relay beamforming system while limiting the interference in the direction of the primary receiver and keeping the transmitted signal secret from the eavesdropper . we show that under both total and individual power constraints , the problem becomes a quasiconvex optimization problem which can be solved by interior point methods . we also propose two sub - optimal null space beamforming schemes which are obtained in a more computationally efficient way . _ index terms : _ amplify - and - forward relaying , cognitive radio , physical - layer security , relay beamforming .
| 141
|
1608.08007
|
ultrasensitive response motifs , which are capable of converting graded stimulus in binary responses , are very well - conserved in signal transduction networks . although it has been shown that a cascade arrangement of multiple ultrasensitive modules can produce an enhancement of the system s ultrasensitivity , how the combination of layers affects the cascade s ultrasensitivity remains an open - ended question for the general case . here we have developed a methodology that allowed us to quantify the effective contribution of each module to the overall cascade s ultrasensitivity and to determine the impact of sequestration effects in the overall system s ultrasensitivity . the proposed analysis framework provided a natural link between global and local ultrasensitivity descriptors and was particularly well - suited to study the ultrasensitivity in map kinase cascades . we used our methodology to revisit oshaughnessy et al . tunable synthetic mapk cascade , in which they claim to have found a new source of ultrasensitivity : ultrasensitivity generated de novo , which arises due to cascade structure itself . in this respect , we showed that the system s ultrasensitivity in its single - step cascade did not come from a cascading effect but from a ` hidden ' first - order ultrasensitivity process in one of the cascade s layer . our analysis also highlighted the impact of the detailed functional form of a module s response curve on the overall system s ultrasensitivity in cascade architectures . local sensitivity features of the involved transfer functions were found to be of the uttermost importance in this kind of setting and could be at the core of non - trivial phenomenology associated to ultrasensitive motifs .
| 284
|
1310.2605
|
stars with radiative envelopes , specifically the upper main sequence chemically peculiar ( ap ) stars , were among the first objects outside our solar system for which surface magnetic fields have been detected . currently magnetic ap stars remains the only class of stars for which high - resolution measurements of both linear and circular polarization in individual spectral lines are feasible . consequently , these stars provide unique opportunities to study the physics of polarized radiative transfer in stellar atmospheres , to analyze in detail stellar magnetic field topologies and their relation to starspots , and to test different methodologies of stellar magnetic field mapping . here i present an overview of different approaches to modeling the surface fields in magnetic a- and b - type stars . in particular , i summarize the ongoing efforts to interpret high - resolution full stokes vector spectra of these stars using magnetic doppler imaging . these studies reveal an unexpected complexity of the magnetic field geometries in some ap stars .
| 171
|
1212.0503
|
we studied the radio spectrum of psr b1259 - 63 in an unique binary with be star ls 2883 and showed that the shape of the spectrum depends on the orbital phase . we proposed a qualitative model which explains this evolution . we considered two mechanisms that might influence the observed radio emission : free - free absorption and cyclotron resonance . recently published results have revealed a new aspect in pulsar radio spectra . there were found objects with turnover at high frequencies in spectra , called gigahertz - peaked spectra ( gps ) pulsars . most of them adjoin such interesting environments as hii regions or compact pulsar wind nebulae ( pwn ) . thus , it is suggested that the turnover phenomenon is associated with the environment than being related intrinsically to the radio emission mechanism . having noticed the apparent resemblance between the b1259 - 63 spectrum and the gps , we suggest that the same mechanisms should be responsible for both cases . therefore , the case of b1259 - 63 can be treated as a key factor to explain the gps phenomenon observed for the solitary pulsars with interesting environments and also another types of spectra ( e.g. with break ) .
| 209
|
1410.7178
|
we study andreev reflection in normal metal - superconductor junctions by using an extended blonder - tinkham - klapwijk model combined with transport calculations based on density functional theory . starting from a parameter - free description of the underlying electronic structure , we perform a detailed investigation of normal metal - superconductor junctions , as the separation between the superconductor and the normal metal is varied . the results are interpreted by means of transverse momentum resolved calculations , which allow us to examine the contributions arising from different regions of the brillouin zone . furthermore we investigate the effect of a voltage bias on the normal metal - superconductor conductance spectra . finally , we consider andreev reflection in carbon nanotubes sandwiched between normal and superconducting electrodes .
| 130
|
0808.0065
|
we report a systematic first - principles study on the recent discovered superconducting ba@xmath0k@xmath1fe@xmath2as@xmath2 systems ( @xmath3 = 0.00 , 0.25 , 0.50 , 0.75 , and 1.00 ) . previous theoretical studies strongly overestimated the magnetic moment on fe of the parent compound bafe@xmath2as@xmath2 . using a negative on - site energy @xmath4 , we obtain a magnetic moment 0.83 @xmath5 per fe , which agrees well with the experimental value ( 0.87 @xmath5 ) . k doping tends to increase the density of states at fermi level . the magnetic instability is enhanced with light doping , and is then weaken by increasing the doping level . the energetics for the different k doping sites are also discussed .
| 121
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0912.3025
|
in this article , i examine several observational trends regarding protoplanetary disks , debris disks and exoplanets in binary systems in an attempt to constrain the physical mechanisms of planet formation in such a context . binaries wider than about 100au are indistinguishable from single stars in all aspects . binaries in the 5100au range , on the other hand , are associated with shorter - lived but ( at least in some cases ) equally massive disks . furthermore , they form planetesimals and mature planetary systems at a similar rate as wider binaries and single stars , albeit with the peculiarity that they predominantly produce high - mass planets . i posit that the location of a stellar companion influences the relative importance of the core accretion and disk fragmentation planet formation processes , with the latter mechanism being predominant in binaries tighter than 100au .
| 148
|
1005.1444
|
the pivot algorithm for self - avoiding walks has been implemented in a manner which is dramatically faster than previous implementations , enabling extremely long walks to be efficiently simulated . we explicitly describe the data structures and algorithms used , and provide a heuristic argument that the mean time per attempted pivot for @xmath0-step self - avoiding walks is @xmath1 for the square and simple cubic lattices . numerical experiments conducted for self - avoiding walks with up to 268 million steps are consistent with @xmath2 behavior for the square lattice and @xmath3 behavior for the simple cubic lattice . our method can be adapted to other models of polymers with short - range interactions , on the lattice or in the continuum , and hence promises to be widely useful . 0 + + * keywords * self - avoiding walk ; polymer ; monte carlo ; pivot algorithm 0 0
| 153
|
0805.2776
|
we calculate the lateral casimir force between corrugated parallel plates , described by @xmath0-function potentials , interacting through a scalar field , using the multiple scattering formalism . the contributions to the casimir energy due to uncorrugated parallel plates is treated as a background from the outset . we derive the leading- and next - to - leading - order contribution to the lateral casimir force for the case when the corrugation amplitudes are small in comparison to corrugation wavelengths . we present explicit results in terms of finite integrals for the case of the dirichlet limit , and exact results for the weak - coupling limit , for the leading- and next - to - leading - orders . the correction due to the next - to - leading contribution is significant . in the weak coupling limit we calculate the lateral casimir force exactly in terms of a single integral which we evaluate numerically . exact results for the case of the weak limit allows us to estimate the error in the perturbative results . we show that the error in the lateral casimir force , in the weak coupling limit , when the next - to - leading order contribution is included is remarkably low when the corrugation amplitudes are small in comparison to corrugation wavelengths . we expect similar conclusions to hold for the dirichlet case . the analogous calculation for the electromagnetic case should reduce the theoretical error sufficiently for comparison with the experiments .
| 250
|
1205.3804
|
we present an @xmath0-covariant quantization of the free electromagnetic field in conformally flat spaces ( cfs ) . a cfs is realized in a six - dimensional space as an intersection of the null cone with a given surface . the smooth move of the latter is equivalent to perform a weyl rescaling . this allows to transport the @xmath0-invariant quantum structure of the maxwell field from minkowski space to any cfs . calculations are simplified and the cfs wightman two - point functions are given in terms of their minkowskian counterparts . the difficulty due to gauge freedom is surpassed by introducing two auxiliary fields and using the gupta - bleuler quantization scheme . the quantum structure is given by a vacuum state and creators / annihilators acting on some hilbert space . in practice , only the hilbert space changes under weyl rescalings . also the quantum @xmath0-invariant free maxwell field does not distinguish between two cfss .
| 160
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1210.3600
|
we present a new model for the observed ly@xmath0 blobs ( labs ) within the context of the standard cold dark matter model . in this model , labs are the most massive halos with the strongest clustering ( proto - clusters ) undergoing extreme starbursts in the high - z universe . aided by calculations of detailed radiative transfer of @xmath1 photons through ultra - high resolution ( @xmath2pc ) large - scale ( @xmath3mpc ) adaptive mesh - refinement cosmological hydrodynamic simulations with galaxy formation , this model is shown to be able to , for the first time , reproduce simultaneously the global @xmath1 luminosity function and luminosity - size relation of the observed labs . physically , a combination of dust attenuation of @xmath1 photons within galaxies , clustering of galaxies , and complex propagation of @xmath1 photons through circumgalactic and intergalactic medium gives rise to the large sizes and frequently irregular isophotal shapes of labs that are observed . a generic and unique prediction of this model is that there should be strong far - infrared ( fir ) sources within each lab , with the most luminous fir source likely representing the gravitational center of the proto - cluster , not necessarily the apparent center of the @xmath1 emission of the lab or the most luminous optical source . upcoming alma observations should unambiguously test this prediction . if verified , labs will provide very valuable laboratories for studying formation of galaxies in the most overdense regions of the universe at a time when global star formation is most vigorous . = 1
| 269
|
physics0410242
|
the problem of sheath formation in front of a conductive planar plate inserted into the plasma is formulated . initially , the plate is assumed to be neutral . it is shown that the charging - up process of the plate is accompanied by the excitation of electron plasma waves . _ @xmath0 plasma physics department , faculty of physics , al . i. cuza university , ro-700506 iasi , romania , + @xmath1j . stefan institute , university of ljubljana , jamova 39 , slo-1000 ljubljana , slovenia , + @xmath2 association euratom - oaw , department of theoretical physics , university of innsbruck , a-6020 innsbruck , austria , + @xmath3 permanent address : institute of physics , georgian academy of sciences , 380077 tbilisi , georgia , + @xmath4association euratom - oaw , department of ion physics , university of innsbruck , a-6020 innsbruck , austria _
| 150
|
1105.0533
|
a systematic analysis is performed for quantum phase transitions in a bond - alternative one - dimensional ising model with a dzyaloshinskii - moriya ( dm ) interaction by using the fidelity of ground state wave functions based on the infinite matrix product states algorithm . for an antiferromagnetic phase , the fidelity per lattice site exhibits a bifurcation , which shows spontaneous symmetry breaking in the system . a critical dm interaction is inversely proportional to an alternating exchange coupling strength for a quantum phase transition . further , a finite - entanglement scaling of von neumann entropy with respect to truncation dimensions gives a central charge @xmath0 at the critical point .
| 114
|
hep-th0504025
|
we construct explicit bps and non - bps solutions of the yang - mills equations on the noncommutative space @xmath0 which have manifest spherical symmetry . using @xmath1-equivariant dimensional reduction techniques , we show that the solutions imply an equivalence between instantons on @xmath0 and nonabelian vortices on @xmath2 , which can be interpreted as a blowing - up of a chain of d0-branes on @xmath2 into a chain of spherical d2-branes on @xmath0 . the low - energy dynamics of these configurations is described by a quiver gauge theory which can be formulated in terms of new geometrical objects generalizing superconnections . this formalism enables the explicit assignment of d0-brane charges in equivariant k - theory to the instanton solutions . hep - th/0504025 + itp uh05/05 + hwm0503 + empg0504 + 1.5 cm * quiver gauge theory of nonabelian vortices + and noncommutative instantons in higher dimensions * alexander d. popov + _ institut fr theoretische physik , universitt hannover + appelstrae 2 , 30167 hannover , germany _ + and + _ bogoliubov laboratory of theoretical physics , jinr + 141980 dubna , moscow region , russia _ + email : popov@itp.uni-hannover.de + richard j. szabo + _ department of mathematics , heriot - watt university + colin maclaurin building , riccarton , edinburgh eh14 4as , u.k . _ + email : r.j.szabo@ma.hw.ac.uk
| 227
|
1510.02314
|
we investigate the ( electro-)geodesic structure of the majumdar - papapetrou solution representing static charged black holes in equilibrium . we assume only two point sources , imparting thus the spacetime axial symmetry . we study electrogeodesics both in and off the equatorial plane and explore the stability of circular trajectories via geodesic deviation equation . in contrast to the classical newtonian situation , we find regions of spacetime admitting two different angular frequencies for a given radius of the circular electrogeodesic . we look both at the weak- and near - field limits of the solution . we use analytic as well as numerical methods in our approach . _ keywords _ : electrogeodesic , majumdar - papapetrou , black hole , extreme reissner - nordstrm
| 127
|
1003.0943
|
the parallel chip - firing game is a periodic automaton on graphs in which vertices `` fire '' chips to their neighbors . in 1989 , bitar conjectured that the period of a parallel chip - firing game with @xmath0 vertices is at most @xmath0 . though this conjecture was disproven in 1994 by kiwi et . al . , it has been proven for particular classes of graphs , specifically trees ( bitar and goles , 1992 ) and the complete graph @xmath1 ( levine , 2008 ) . we prove bitar s conjecture for complete bipartite graphs and characterize completely all possible periods for positions of the parallel chip - firing game on such graphs . furthermore , we extend our construction of all possible periods for games on the bipartite graph to games on complete @xmath2-partite graphs , @xmath3 , and prove some pertinent lemmas about games on general simple connected graphs . tian - yi jiang
| 160
|
1401.2943
|
we propose a real - time machine translation system that allows users to select a news category and to translate the related live news articles from arabic , czech , danish , farsi , french , german , italian , polish , portuguese , spanish and turkish into english . the moses - based system was optimised for the news domain and differs from other available systems in four ways : ( 1 ) news items are automatically categorised on the source side , before translation ; ( 2 ) named entity translation is optimised by recognising and extracting them on the source side and by re - inserting their translation in the target language , making use of a separate entity repository ; ( 3 ) news titles are translated with a separate translation system which is optimised for the specific style of news titles ; ( 4 ) the system was optimised for speed in order to cope with the large volume of daily news articles .
| 169
|
1101.5759
|
on 17 january 2005 two fast coronal mass ejections were recorded in close succession during two distinct episodes of a 3b / x3.8 flare . both were accompanied by metre - to - kilometre type - iii groups tracing energetic electrons that escape into the interplanetary space and by decametre - to - hectometre type - ii bursts attributed to cme - driven shock waves . a peculiar type - iii burst group was observed below 600 khz 1.5 hours after the second type iii group . it occurred without any simultaneous activity at higher frequencies , around the time when the two cmes were expected to interact . we associate this emission with the interaction of the cmes at heliocentric distances of about 25 r@xmath0 . near - relativistic electrons observed by the epam experiment onboard ace near 1 au revealed successive particle releases that can be associated with the two flare / cme events and the low - frequency type - iii burst at the time of cme interaction . we compare the pros and cons of shock acceleration and acceleration in the course of magnetic reconnection for the escaping electron beams revealed by the type iii bursts and for the electrons measured _ in situ_.
| 208
|
1611.03811
|
one of the main challenges faced by biometric - based authentication systems is the need to offer secure authentication while maintaining the privacy of the biometric data . previous solutions , such as secure sketch and fuzzy extractors , rely on assumptions that can not be guaranteed in practice , and often affect the authentication accuracy . in this paper , we introduce honeyfaces : the concept of adding a large set of synthetic faces ( indistinguishable from real ) into the biometric `` password file '' . this password inflation protects the privacy of users and increases the security of the system without affecting the accuracy of the authentication . in particular , privacy for the real users is provided by `` hiding '' them among a large number of fake users ( as the distributions of synthetic and real faces are equal ) . in addition to maintaining the authentication accuracy , and thus not affecting the security of the authentication process , honeyfaces offer several security improvements : increased exfiltration hardness , improved leakage detection , and the ability to use a two - server setting like in honeywords . finally , honeyfaces can be combined with other security and privacy mechanisms for biometric data . we implemented the honeyfaces system and tested it with a password file composed of 270 real users . the `` password file '' was then inflated to accommodate up to @xmath0 users ( resulting in a 56.6 tb `` password file '' ) . at the same time , the inclusion of additional faces does not affect the true acceptance rate or false acceptance rate which were 93.33% and 0.01% , respectively . biometrics ( access control ) , face recognition , privacy
| 292
|
hep-ph0504286
|
electroweak precision data have been extensively used to constrain models containing physics beyond that of the standard model . when the model contains higgs scalars in representations other than singlets or doublets , and hence @xmath0 at tree level , a correct renormalization scheme requires more inputs than the three commonly used for the standard model case . in such cases , the one loop electroweak results can not be split into a standard model contribution plus a piece which vanishes as the scale of new physics becomes much larger than @xmath1 . we illustrate our results by presenting the dependence of @xmath1 on the top quark mass in a model with a higgs triplet and in the @xmath2 left - right symmetric model . in these models , the allowed range for the lightest neutral higgs mass can be as large as a few tev .
| 147
|
1504.00518
|
the passage of cold cesium 49s@xmath0 rydberg atoms through an electric - field - induced multi - level avoided crossing with nearby hydrogen - like rydberg levels is employed to prepare a cold , dipolar rydberg atom gas . when the electric field is ramped through the avoided crossing on time scales on the order of 100 ns or slower , the 49s@xmath0 population adiabatically transitions into high-_l _ rydberg stark states . the adiabatic state transformation results in a cold gas of rydberg atoms with large electric dipole moments . after a waiting time of about @xmath1s and at sufficient atom density , the adiabatically transformed highly dipolar atoms become undetectable , enabling us to discern adiabatic from diabatic passage behavior through the avoided crossing . we attribute the state - selectivity to @xmath2-mixing collisions between the dipolar atoms . the data interpretation is supported by numerical simulations of the passage dynamics and of binary @xmath2-mixing collisions .
| 159
|
1405.1768
|
our aim in the present work is to develop approximations for the collisional dynamics of traveling waves in the context of granular chains in the presence of precompression . to that effect , we aim to quantify approximations of the relevant hertzian fpu - type lattice through both the korteweg - de vries ( kdv ) equation and the toda lattice . using the availability in such settings of both 1-soliton and 2-soliton solutions in explicit analytical form , we initialize such coherent structures in the granular chain and observe the proximity of the resulting evolution to the underlying integrable ( kdv or toda ) model . while the kdv offers the possibility to accurately capture collisions of solitary waves propagating in the same direction , the toda lattice enables capturing both co - propagating and counter - propagating soliton collisions . the error in the approximation is quantified numerically and connections to bounds established in the mathematical literature are also given .
| 163
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