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astro-ph9708262
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a rarity among supernova , sn 1993j in m81 can be studied with high spatial resolution . its radio power and distance permit vlbi observations to monitor the expansion of its angular structure . this radio structure was previously revealed to be shell - like and to be undergoing a self - similar expansion at a constant rate . from vlbi observations at the wavelengths of 3.6 and 6 cm in the period 6 to 42 months after explosion , we have discovered that the expansion is decelerating . our measurement of this deceleration yields estimates of the density profiles of the supernova ejecta and circumstellar material in standard supernova explosion models .
| 113
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1207.0168
|
bell - state analysis ( bsa ) is essential in quantum communication , but it is impossible to distinguish unambiguously the four bell states in the polarization degree of freedom ( dof ) of two - photon systems with only linear optical elements , except for the case in which the bsa is assisted with hyperentangled states , the simultaneous entanglement in more than one dof . here , we propose a scheme to distinguish completely the 16 hyperentangled bell states in both the polarization and the spatial - mode dofs of two - photon systems , by using the giant nonlinear optics in quantum dot - cavity systems . this scheme can be applied to increase the channel capacity of long - distance quantum communication based on hyperentanglement , such as entanglement swapping , teleportation , and superdense coding . we use hyperentanglement swapping as an example to show the application of this hbsa .
| 156
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quant-ph0509026
|
the dynamics of particles moving in a medium defined by its relativistically invariant stochastic properties is investigated . for this aim , the force exerted on the particles by the medium is defined by a stationary random variable as a function of the proper time of the particles . the equations of motion for a single one - dimensional particle are obtained and numerically solved . a conservation law for the drift momentum of the particle during its random motion is shown . moreover , the conservation of the mean value of the total linear momentum for two particles repelling each other according with the coulomb interaction is also following . therefore , the results indicate the realization of a kind of stochastic noether theorem in the system under study . possible applications to the stochastic representation of quantum mechanics are advanced .
| 143
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astro-ph0004167
|
the good energy resolution ( 34 kev fwhm ) of the transient gamma ray spectrometer ( tgrs ) on board the _ wind _ spacecraft makes it sensitive to doppler - shifted outbursts of 511 kev electron - positron annihilation radiation , the reason being that the doppler shift causes the cosmic line to be slightly offset from a strong instrumental background 511 kev line at rest , which is ubiquitous in space environments . such a cosmic line ( blueshifted ) is predicted to arise in classical novae due to the annihilation of positrons from @xmath0-decay on a timescale of a few hours in an expanding envelope . a further advantage of tgrs its broad field of view , containing the entire southern ecliptic hemisphere has enabled us to make a virtually complete and unbiased 3year search for classical novae at distances up to @xmath1 kpc . we present negative results of this search , and estimate its implications for the highly - uncertain galactic classical nova rate and for future space missions .
| 175
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1211.1364
|
community detection is the process of assigning nodes and links in significant communities ( e.g. clusters , function modules ) and its development has led to a better understanding of complex networks . when applied to sizable networks , we argue that most detection algorithms correctly identify prominent communities , but fail to do so across multiple scales . as a result , a significant fraction of the network is left uncharted . we show that this problem stems from larger or denser communities overshadowing smaller or sparser ones , and that this effect accounts for most of the undetected communities and unassigned links . we propose a generic cascading approach to community detection that circumvents the problem . using real network datasets with two widely used community detection algorithms , we show how cascading detection allows for the detection of the missing communities and results in a significant drop of the fraction of unassigned links . = 1
| 159
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astro-ph9609183
|
we have studied the distribution of @xmath0 galaxies from the roe / nrl cosmos / ukst catalogue around two samples of @xmath1 qsos with similar redshift distributions . the first sample is formed by 144 radio - loud qsos from the parkes catalogue , and the other contains 167 optically selected qsos extracted from the large bright quasar survey . it is found that there is a @xmath2 significance level excess of cosmos / ukst galaxies around the pks qsos , whereas there is a marginal defect of galaxies around the lbqs qsos . when the distribution of galaxies around both samples is compared , we found that there is an overdensity of galaxies around the pks sample with respect to the lbqs sample anticorrelated with the distance from the qsos at a @xmath3 significance level . although this result apparently agrees with the predictions of the multiple magnification bias , it is difficult to explain by gravitational lensing effects alone ; dust in the foreground galaxies and selection effects in the detection of lbqs qsos should be taken into account . it has been established that the lines of sight to pks flat - spectrum qsos go through significatively higher foreground galaxy densities than the directions to lbqs quasars , what may be partially related with the reported reddening of pks qsos .
| 224
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hep-lat9708011
|
the order of the coulomb - higgs transition in the u(1)-higgs model with unfrozen modulus of the scalar field is studied . large lattices ( up to @xmath0 in one case ) and high statistics are used . we fix @xmath1 and explore specially a region of @xmath2-values where metastability is observed . we study the thermodynamical limit of several observables , in particular , the latent heat , the specific heat , the decrement of the free energy between the maxima and the central minimum of the two - peaked histogram , the binder cumulant and the displacement of the critical coupling with the lattice size . the results point towards a second order transition for @xmath3 , while for smaller values of @xmath2 the strong metastability growing with the lattice size seems to derive from a first order character . _ a ) _ departamento de fsica terica , facultad de ciencias , + universidad de zaragoza , 50009 zaragoza , spain + _ b ) _ departamento de fsica terica i , facultad de ciencias fsicas , + universidad complutense de madrid , 28040 madrid , spain + _ key words : _ lattice . monte carlo . u(1 ) . higgs . phase transition . pacs : _ 14.80.bn , 11.15.ha
| 215
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1107.4343
|
the arecibo l - band feed array zone of avoidance ( alfa zoa ) survey has discovered a nearby galaxy , alfa zoa j1952 + 1428 , at a heliocentric velocity of + 279 @xmath0 . the galaxy was discovered at low galactic latitude by 21-cm emission from neutral hydrogen ( h ) . we have obtained follow - up observations with the evla and the 0.9-m sara optical telescope . the h distribution overlaps an uncataloged , potential optical counterpart . the h linear size is 1.4 kpc at our adopted distance of d = 7 mpc , but the distance estimate is uncertain as hubble s law is unreliable at low recessional velocities . the optical counterpart has m@xmath1 = 16.9 mag and @xmath2 - @xmath3 = 0.1 mag . these characteristics , including m@xmath4 = 10@xmath5 m@xmath6 and @xmath7 = @xmath8 l@xmath6 , if at 7 mpc , indicate that this galaxy is a blue compact dwarf , but this remains uncertain until further follow - up observations are complete . optical follow - up observations are ongoing and near infrared follow - up observations have been scheduled .
| 192
|
1609.02736
|
we show that resonant dipole - dipole interactions between rydberg atoms in a triangular lattice can give rise to artificial magnetic fields for spin excitations . we consider the coherent dipole - dipole coupling between @xmath0 and @xmath1 rydberg states and derive an effective spin-1/2 hamiltonian for the @xmath0 excitations . by breaking time - reversal symmetry via external fields we engineer complex hopping amplitudes for transitions between two rectangular sub - lattices . the phase of these hopping amplitudes depends on the direction of the hop . this gives rise to a staggered , artificial magnetic field which induces non - trivial topological effects . we calculate the single - particle band structure and investigate its chern numbers as a function of the lattice parameters and the detuning between the two sub - lattices . we identify extended parameter regimes where the chern number of the lowest band is @xmath2 or @xmath3 .
| 154
|
0707.4660
|
the influence of lorentz- and cpt - violating terms of the extended standard model on a semi - classical two - level system is analyzed . it is shown that the lorentz - violating background ( when coupled with the fermion sector in a vector way ) is able to induce modifications on the rabi oscillation pattern , promoting sensitive modulations on the usual oscillations . as for the term involving the coefficient coupled in an axial vector way , it brings about oscillations both on energy states and on the spin states ( implied by the background ) . it is also seen that such backgrounds are able to yield state oscillations even in the absence of the electromagnetic field . the foreseen effects are used to establish upper bounds on the lorentz - violating coefficients .
| 138
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1606.06017
|
we propose an approach for multiple sequence alignment ( msa ) derived from the dynamic time warping viewpoint and recent techniques of curve synchronization developed in the context of functional data analysis . starting from pairwise alignments of all the sequences ( viewed as paths in a certain space ) , we construct a median path that represents the msa we are looking for . we establish a proof of concept that our method could be an interesting ingredient to include into refined msa techniques . we present a simple synthetic experiment as well as the study of a benchmark dataset , together with comparisons with 2 widely used msa softwares . \1 . departamento de estadstica , universidad carlos iii de madrid , c/ madrid , 126 - 28903 getafe , spain . e - mail : ana.arribas@uc3m.es + 2 . sorbonne universits , universit pierre et marie curie , universit paris diderot , centre national de la recherche scientifique , laboratoire de probabilits et modles alatoires , 4 place jussieu , 75252 paris cedex 05 , france . e - mail : catherine.matias@math.cnrs.fr _ key words and phrases : alignment ; dynamic time warping ; multiple sequence alignment ; warping _ +
| 204
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1510.06014
|
in 1982 , marshall p. tulin published a report proposing a framework for reducing the equations for gravity waves generated by moving bodies into a single nonlinear differential equation solvable in closed form [ _ proc . 14th symp . on naval hydrodynamics _ , 1982 , pp.1951 ] . several new and puzzling issues were highlighted by tulin , notably the existence of weak and strong wave - making regimes , and the paradoxical fact that the theory seemed to be applicable to flows at low speeds , _ but not too low speeds"_. these important issues were left unanswered , and despite the novelty of the ideas , tulin s report fell into relative obscurity . now thirty years later , we will revive tulin s observations , and explain how an asymptotically consistent framework allows us to address these concerns . most notably , we will explain , using the asymptotic method of steepest descents , how the production of free - surface waves can be related to the arrangement of integration contours connected to the shape of the moving body . this approach provides an intuitive and visual procedure for studying nonlinear wave - body interactions . surface gravity waves , wave - structure interactions , waves / free - surface flows
| 216
|
1009.0894
|
w28 is one of the archetype supernova remnants ( snrs ) interacting with molecular clouds . h.e.s.s . observation found four tev sources which are coincident with the molecular clouds ( mcs ) around w28 , but _ fermi _ lat detected no prominent gev counterparts for two of them . an accumulative diffusion model is established in this letter and the energetic protons colliding the nearby mcs are considered to be an accumulation of the diffusive protons escaping from the shock front throughout the history of the snr expansion . we have fitted the @xmath0-ray spectra of the four sources and naturally explained the gev spectral break of the northeastern source ( source n ) and the nonsignificant gev emission of the southern sources a and c. the distances of sources a and c from the snr centre are found to be much larger than those of sources n and b , which may be the basic reason for the faint gev @xmath0-rays of the two former sources . [ firstpage ] radiation mechanisms : non - thermal gamma rays : theory ism : supernova remnants .
| 188
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1604.08791
|
the hypothesis of a pevatron in the galactic center , emerged with the recent @xmath0-ray measurements of h.e.s.s . @xcite , motivates the search for neutrinos from this source . the effect of @xmath0-ray absorption is studied : at the energies currently probed , the known background radiation fields lead to small effects , whereas it is not possible to exclude large effects due to new ir radiation fields near the very center . precise upper limits on neutrino fluxes are derived and the underlying hypotheses are discussed . the expected number of events for antares , icecube and km3net , based on the h.e.s.s . measurements , are calculated . it is shown that km@xmath1-class telescopes in the northern hemisphere have the potential of observing high - energy neutrinos from this important astronomical object and can check the existence of a hadronic pev galactic accelerator .
| 147
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0801.4568
|
in the cdm cosmological framework structures grow from merging with smaller structures . merging should have observable effects on galaxies including destroying disks and creating spheroids . this proceeding aims to give a brief overview of how mergers occur in cosmological simulations . in this regard it is important to understand that dark matter halo mergers are not galaxy mergers ; a theory of galaxy formation is necessary to connect the two . mergers of galaxies in hydrodynamical simulations show a stronger dependence on mass than halo mergers in n - body simulations . if one knows how to connect galaxies to dark matter halos then the halo merger rate can be converted into a galaxy merger rate . when this is done it becomes clear that major mergers are many times more common in more massive galaxies offering a possible explanation of why hubble type depends on galaxy mass .
| 151
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cond-mat0610671
|
in this paper , we investigate the microscopic dynamics of a polymer of length @xmath0 translocating through a narrow pore . characterization of its purportedly anomalous dynamics has so far remained incomplete . we show that the polymer dynamics is anomalous until the rouse time @xmath1 , with a mean square displacement through the pore consistent with @xmath2 , with @xmath3 the flory exponent . this is shown to be directly related to a decay in time of the excess monomer density near the pore as @xmath4 . beyond the rouse time translocation becomes diffusive . in consequence of this , the dwell - time @xmath5 , the time a translocating polymer typically spends within the pore , scales as @xmath6 , in contrast to previous claims .
| 128
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1009.0365
|
we investigate the effects of quantum gravity on the planck era of the universe . in particular , using different versions of the generalized uncertainty principle and under specific conditions we find that the main planck quantities such as the planck time , length , mass and energy become larger by a factor of order @xmath0 compared to those quantities which result from the heisenberg uncertainty principle . however , we prove that the dimensionless entropy enclosed in the cosmological horizon at the planck time remains unchanged . these results , though preliminary , indicate that we should anticipate modifications in the set - up of cosmology since changes in the planck era will be inherited even to the late universe through the framework of quantum gravity ( or quantum field theory ) which utilizes the planck scale as a fundamental one . more importantly , these corrections will not affect the entropic content of the universe at the planck time which is a crucial element for one of the basic principles of quantum gravity named holographic principle .
| 179
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1105.1877
|
we study the velocity structure of penumbral filaments in the deep photosphere to obtain direct evidence for the convective nature of sunspot penumbrae . a sunspot was observed at high spatial resolution with the 1-m swedish solar telescope in the deep photospheric c@xmath0i5380 absorption line . the multi - object multi - frame blind deconvolution ( momfbd ) method is used for image restoration and straylight is filtered out . we report here the discovery of clear redshifts in the c@xmath0i5380 line at multiple locations in sunspot penumbral filaments . for example , bright head of filaments show larger concentrated blueshift and are surrounded by darker , redshifted regions , suggestive of overturning convection . elongated downflow lanes are also located beside bright penumbral fibrils . our results provide the strongest evidence yet for the presence of overturning convection in penumbral filaments and highlight the need to observe the deepest layers of the penumbra in order to uncover the energy transport processes taking place there .
| 166
|
hep-lat0206010
|
the laplacian gauge is a nonperturbative gauge fixing that reduces to landau gauge in the asymptotic limit . like landau gauge , it respects lorentz invariance , but it is free of gribov copies ; the gauge fixing is unambiguous . in this paper we study the infrared behavior of the lattice gluon propagator in laplacian gauge by using a variety of lattices with spacings from @xmath0 to 0.35 fm , to explore finite volume and discretization effects . three different implementations of the laplacian gauge are defined and compared . the laplacian gauge propagator has already been claimed to be insensitive to finite volume effects and this is tested on lattices with large volumes .
| 116
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astro-ph9610097
|
it is believed that most giant elliptical galaxies possess nuclear black holes with masses in excess of @xmath0 . bondi accretion from the interstellar medium might then be expected to produce quasar - like luminosities from the nuclei of even quiescent elliptical galaxies . it is a puzzle that such luminosities are _ not observed_. motivated by this problem , fabian & rees have recently suggested that the final stages of accretion in these objects occurs in an advection - dominated mode with a correspondingly small radiative efficiency . despite possessing a long - known active nucleus and dynamical evidence for a black hole , the low radiative and kinetic luminosities of the core of m87 provide the best illustration of this problem . we examine an advection - dominated model for the nucleus of m87 and show that accretion at the bondi rate is compatible with the best known estimates for the core flux from radio through to x - ray wavelengths . the success of this model prompts us to propose that fr - i radio galaxies and quiescent elliptical galaxies accrete in an advection dominated mode whereas fr - ii type radio - loud nuclei possess radiatively efficient thin accretion disks . ps . # 1to 0pt#1 galaxies : individual : m87 , galaxies : active , accretion , accretion discs
| 224
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1201.1780
|
we analyze spacetime momentum currents on a classical string worldsheet , study their generic connection via ads / cft correspondence to the instantaneous energy loss of the dual field theory degrees of freedom and suggest a general formula for computing energy loss in a time - dependent string configuration . applying this formula to the case of falling strings , generally dual to light quarks , reveals that the energy loss does not display a well - pronounced bragg peak at late times , as previously believed . finally , we comment on the possible implications of this result to the jet quenching phenomena in heavy ion collisions .
| 109
|
1003.0002
|
recent claims of a gamma - ray excess in the diffuse galactic emission detected by the fermi large area telescope made use of spatial templates from the interstellar medium ( ism ) column density and the 408 mhz sky as proxies for neutral pion and inverse compton ( ic ) gamma - ray emission , respectively . we identify significant systematic effects in this procedure that can artificially induce an additional diffuse component with a morphology strikingly similar to the claimed gamma - ray haze . to quantitatively illustrate this point we calculate sky - maps of the ratio of the gamma - ray emission from neutral pions to the ism column density , and of ic to synchrotron emission , using detailed galactic cosmic - ray models and simulations . in the region above and below the galactic center , the ism template underestimates the gamma - ray emission due to neutral pion decay by approximately 20% . additionally , the synchrotron template tends to under - estimate the ic emission at low energies ( few gev ) and to over - estimate it at higher energies ( tens of gev ) by potentially large factors that depend crucially on the assumed magnetic field structure of the galaxy . the size of the systematic effects we find are comparable to the size of the claimed `` fermi haze '' signal . we thus conclude that a detailed model for the galactic diffuse emission is necessary in order to conclusively assess the presence of a gamma - ray excess possibly associated to the wmap haze morphology .
| 267
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1409.5641
|
the complexity of computing the lempel - ziv factorization and the set of all runs (= maximal repetitions ) is studied in the decision tree model of computation over ordered alphabet . it is known that both these problems can be solved by ram algorithms in @xmath0 time , where @xmath1 is the length of the input string and @xmath2 is the number of distinct letters in it . we prove an @xmath3 lower bound on the number of comparisons required to construct the lempel - ziv factorization and thereby conclude that a popular technique of computation of runs using the lempel - ziv factorization can not achieve an @xmath4 time bound . in contrast with this , we exhibit an @xmath5 decision tree algorithm finding all runs in a string . therefore , in the decision tree model the runs problem is easier than the lempel - ziv factorization . thus we support the conjecture that there is a linear ram algorithm finding all runs .
| 167
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1008.1070
|
we study the effect of marginal and irrelevant deformations on the renormalization of operators near a cft fixed point . new divergences in a given operator are determined by its ope with the operator @xmath0 that generates the deformation . this provides a scheme to compute the couplings @xmath1 between the operator @xmath0 and two arbitrary operators @xmath2 and @xmath3 . we exemplify for the case of @xmath4 sym , considering the simplest case of the exact lagrangian deformation . in this case the deformed anomalous dimension matrix is determined by the derivative of the anomalous dimension matrix with respect to the coupling . we use integrability techniques to compute the one - loop couplings @xmath5 between the lagrangian and two distinct large operators built with magnons , in the su(2 ) sector of the theory . then we consider @xmath6 at strong coupling , and show how to compute it using the gauge / gravity duality , when @xmath0 is a chiral operator dual to any supergravity field and @xmath2 is dual to a heavy string state . we exemplify for the lagrangian and operators @xmath2 dual to heavy string states , showing agreement with the prediction derived from the renormalization group arguments . miguel s. costa@xmath7 , ricardo monteiro@xmath8 , jorge e. santos@xmath8 , dimitrios zoakos@xmath7 + _ @xmath9 centro de fsica do porto + departamento de fsica e astronomia + faculdade de cincias da universidade do porto + rua do campo alegre 687 , 4169007 porto , portugal _ + _ @xmath10damtp , centre for mathematical sciences + university of cambridge + wilberforce road , cambridge cb3 0wa , uk _
| 274
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math-ph0407013
|
an embedding scheme is developed for the dirac hamiltonian @xmath0 . dividing space into regions i and ii separated by surface @xmath1 , an expression is derived for the expectation value of @xmath0 which makes explicit reference to a trial function defined in i alone , with all details of region ii replaced by an effective potential acting on @xmath1 and which is related to the green function of region ii . stationary solutions provide approximations to the eigenstates of @xmath0 within i. the green function for the embedded hamiltonian is equal to the green function for the entire system in region i. application of the method is illustrated for the problem of a hydrogen atom in a spherical cavity and an au(001)/ag / au(001 ) sandwich structure using basis sets that satisfy kinetic balance .
| 136
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1508.04036
|
there is some consensus among orthodox category theorists that the concept of adjoint functors is the most important concept contributed to mathematics by category theory . we give a heterodox treatment of adjoints using heteromorphisms ( object - to - object morphisms between objects of different categories ) that parses an adjunction into two separate parts ( left and right representations of heteromorphisms ) . then these separate parts can be recombined in a new way to define a cognate concept , the brain functor , to abstractly model the functions of perception and action of a brain . the treatment uses relatively simple category theory and is focused on the interpretation and application of the mathematical concepts . the mathematical appendix is of general interest to category theorists as it is a defense of the use of heteromorphisms as a natural and necessary part of category theory .
| 149
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1405.6917
|
the search for sharp features in the gamma - ray spectrum is a promising approach to identify a signal from dark matter annihilations over the astrophysical backgrounds . in this paper we investigate the generation of gamma - ray lines and internal bremsstrahlung signals in a toy model where the dark matter particle is a real scalar that couples to a lepton and an exotic fermion via a yukawa coupling . we show that the fermi - lat and h.e.s.s . searches for line - like spectral features severely constrain regions of the parameter space where the scalar dark matter is thermally produced . finally , we also discuss the complementarity of the searches for sharp spectral features with other indirect dark matter searches , as well as with direct and collider searches .
| 134
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astro-ph0411229
|
techniques for the construction of dynamical galaxy models should be considered essential infrastructure that should be put in place before gaia flies . three possible modelling techniques are discussed . although one of these seems to have significantly more potential than the other two , at this stage work should be done on all three . a major effort is needed to decide how to make a model consistent with a catalogue such as that which gaia will produce . given the complexity of the problem , it is argued that a hierarchy of models should be constructed , of ever increasing complexity and quality of fit to the data . the potential that resonances and tidal streams have to indicate how a model should be refined is briefly discussed .
| 131
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astro-ph0509475
|
i summarize some results from the recent co survey of late - type , low surface brightness ( lsb ) spiral galaxies by matthews et al . ( 2005 ) . we have now detected co emission from six late - type , lsb spirals , demonstrating that despite their typical low metallicities and low mean gas surface densities , some lsb galaxies contain a molecular medium that is traced by co. we find that the co - detected lsb spirals adhere to the same @xmath0-fir correlation as brighter galaxies . we also find a significant drop - off in the detectability of co among low - to - intermediate surface brightness galaxies with @xmath190 km s@xmath2 , pointing toward fundamental changes in the physical conditions of the ism with decreasing disk mass .
| 134
|
cond-mat0507293
|
the ising spin - glasses are investigated on three dual pairs of hierarchical lattices , using exact renormalization - group transformation of the quenched bond probability distribution . the goal is to investigate a recent conjecture which relates , on such pairs of dual lattices , the locations of the multicritical points , which occur on the nishimori symmetry line . towards this end we precisely determine the global phase diagrams for these six hierarchical spin - glasses , using up to @xmath0 probability bins to represent the quenched distribution subjected to an exact renormalization - group transformation . we find in all three cases that the conjecture is realized to a very good approximation , even when the mutually dual models belong to different spatial dimensionalities @xmath1 and have different phase diagram topologies at the multicritical points of the conjecture and even though the contributions to the conjecture from each lattice of the dual pair are strongly asymmetric . in all six phase diagrams , we find reentrance near the multicritical point . in the models with @xmath2 or 1.5 , the spin - glass phase does not occur and the phase boundary between the ferromagnetic and paramagnetic phases is second order with a strong violation of universality . pacs numbers : 75.10.nr , 64.60.kw , 05.45.df , 05.10.cc
| 220
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astro-ph0009205
|
we present the current results of a survey for oh megamasers ( ohms ) underway at the arecibo observatory . the survey is 2/3 complete and has produced a high ohm detection rate ( 1 in 6 ) from a redshift - selected sample of _ iras _ galaxies . the survey will relate the ohm luminosity function to the galaxy merger rate , allowing subsequent blind ohm surveys to measure the galaxy merger rate as a function of cosmic time . the survey has also made the first detection of strong variability in ohms . variability will provide a powerful tool for understanding the small - scale physical settings and mechanisms of ohms .
| 115
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1602.08456
|
in this paper , we study the dynamics of epidemic processes taking place in adaptive networks of arbitrary topology . we focus our study on the adaptive susceptible - infected - susceptible ( asis ) model , where healthy individuals are allowed to temporarily cut edges connecting them to infected nodes in order to prevent the spread of the infection . in this paper , we derive a closed - form expression for a lower bound on the epidemic threshold of the asis model in arbitrary networks with heterogeneous node and edge dynamics . for networks with homogeneous node and edge dynamics , we show that the resulting lower bound is proportional to the epidemic threshold of the standard sis model over static networks , with a proportionality constant that depends on the adaptation rates . furthermore , based on our results , we propose an efficient algorithm to optimally tune the adaptation rates in order to eradicate epidemic outbreaks in arbitrary networks . we confirm the tightness of the proposed lower bounds with several numerical simulations and compare our optimal adaptation rates with popular centrality measures .
| 188
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1301.6545
|
stars form in dense cores of molecular clouds that are observed to be significantly magnetized . in the simplest case of a laminar ( non - turbulent ) core with the magnetic field aligned with the rotation axis , both analytic considerations and numerical simulations have shown that the formation of a large , @xmath0-scale , rotationally supported protostellar disk is suppressed by magnetic braking in the ideal mhd limit for a realistic level of core magnetization . this theoretical difficulty in forming protostellar disks is termed `` magnetic braking catastrophe . '' a possible resolution to this problem , proposed by @xcite and @xcite , is that misalignment between the magnetic field and rotation axis may weaken the magnetic braking enough to enable disk formation . we evaluate this possibility quantitatively through numerical simulations . we confirm the basic result of @xcite that the misalignment is indeed conducive to disk formation . in relatively weakly magnetized cores with dimensionless mass - to - flux ratio @xmath1 , it enabled the formation of rotationally supported disks that would otherwise be suppressed if the magnetic field and rotation axis are aligned . for more strongly magnetized cores , disk formation remains suppressed , however , even for the maximum tilt angle of @xmath2 . if dense cores are as strongly magnetized as indicated by oh zeeman observations ( with a mean dimensionless mass - to - flux ratio @xmath3 ) , it would be difficult for the misalignment alone to enable disk formation in the majority of them . we conclude that , while beneficial to disk formation , especially for the relatively weak field case , the misalignment does not completely solve the problem of catastrophic magnetic braking in general .
| 291
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1402.0218
|
recently much attention has been paid to the study of the robustness of interdependent and multiplex networks and , in particular , networks of networks . the robustness of interdependent networks can be evaluated by the size of a mutually connected component when a fraction of nodes have been removed from these networks . here we characterize the emergence of the mutually connected component in a network of networks in which every node of a network ( layer ) @xmath0 is connected with @xmath1 its randomly chosen replicas in some other networks and is interdependent of these nodes with probability @xmath2 . we find that when the superdegrees @xmath1 of different layers in the network of networks are distributed heterogeneously , multiple percolation phase transition can occur . we show that , depending on the value of @xmath2 , these transition are continuous or discontinuous .
| 146
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1702.05629
|
the recent discovery of a gravitational wave from the merging of two black holes of about 30 solar masses each challenges our incomplete understanding of massive stars and their evolution . critical ingredients comprise mass - loss , rotation , magnetic fields , internal mixing , and mass transfer in close binary systems . the imperfect knowledge of these factors implies large uncertainties for models of stellar populations and their feedback . in this contribution we summarize our empirical studies of wolf - rayet populations at different metallicities by means of modern non - lte stellar atmosphere models , and confront these results with the predictions of stellar evolution models . at the metallicity of our galaxy , stellar winds are probably too strong to leave remnant masses as high as @xmath030m@xmath1 , but given the still poor agreement between evolutionary tracks and observation even this conclusion is debatable . at the low metallicity of the small magellanic cloud , all wn stars which are ( at least now ) single are consistent with evolving quasi - homogeneously . o and b - type stars , in contrast , seem to comply with standard evolutionary models without strong internal mixing . close binaries which avoided early merging could evolve quasi - homogeneously and lead to close compact remnants of relatively high masses that merge within a hubble time .
| 229
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cond-mat0012510
|
critical behavior of the infrared reflectivity of rusr@xmath0gdcu@xmath0o@xmath1 ceramics is observed near the superconducting @xmath2 = 45 k and magnetic @xmath3 = 133 k transition temperatures . the optical conductivity reveals the typical features of the @xmath4-axis optical conductivity of strongly underdoped multilayer superconducting cuprates . the transformation of the cu - o bending mode at 288 @xmath5 to a broad absorption peak at the temperatures between @xmath6 = 90 k and @xmath2 is clearly observed , and is accompanied by the suppression of spectral weight at low frequencies . the correlated shifts to lower frequencies of the ru - related phonon mode at 190 @xmath5 and the mid - ir band at 4800 @xmath5 on decreasing temperature below @xmath3 are observed . it provides experimental evidence in favor of strong electron - phonon coupling of the charge carriers in the ru - o layers which critically depends on the ru core spin alignment . the underdoped character of the superconductor is explained by strong hole depletion of the cuo@xmath0 planes caused by the charge carrier self - trapping at the ru moments .
| 184
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1103.3273
|
some tails of ram - pressure stripped galaxies are detected in h@xmath0 , some in h@xmath1 , and some in x - ray ( but never all three so far ) . we use numerical simulations to probe the conditions for the production of x - ray bright tails , demonstrating that the primary requirement is a high pressure intracluster medium ( icm ) . this is because the stripped tail is mostly in pressure equilibrium with the icm , but mixing leaves it with densities and temperatures intermediate between the cold gas in the disk and the hot icm . given a high enough icm pressure , this mixed gas lies in the x - ray bright region of the phase diagram . we compare the simulations to observations of the ram pressure stripped tail of eso 137 - 001 , showing excellent agreement in the total measured x - ray and h@xmath1 emission and non - flaring morphology of the tail , and consistent h@xmath0 measurements . using these comparisons we constrain the level of mixing and efficiency of heat conduction in the intracluster medium ( icm ) .
| 191
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1402.1043
|
using spectral data from non - strange and strange hadronic @xmath0 decays , flavor - breaking chiral sum rules involving the flavor @xmath1 and @xmath2 current - current two - point functions are constructed and used to determine the @xmath3 nnlo low - energy constant combinations @xmath4 , @xmath5 and @xmath6 . the first of these determinations updates the results of an earlier analysis by drr and kambor , while the latter two are new . the error on the @xmath5 is particularly small . comparisons are made to model estimates for these quantities . the role of the third combination in significantly improving the determination of the nlo low - energy constant @xmath7 from nnlo analyses of the flavor @xmath1 v - a correlator is also highlighted .
| 129
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1504.00184
|
the relaxation times over which dissipative fluxes restore their steady state values have been evaluated for a pion gas using the 14-moment method . the effect of the medium has been implemented through a temperature dependent @xmath0 cross - section in the collision integral which is obtained by including one - loop self - energies in the propagators of the exchanged @xmath1 and @xmath2 mesons . to account for chemical freeze out in heavy ion collisions , a temperature dependent pion chemical potential has been introduced in the distribution function . the temperature dependence of the relaxation times for shear and bulk viscous flows as well as the heat flow is significantly affected .
| 114
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1302.1743
|
we consider high energy electron scattering by hydrogen atoms in the presence of a laser field of moderate power and higher frequencies . if the field is a superposition of a linearly and a circularly polarized laser beam in a particular configuration , then we can show that circular dichroism in two photon transitions can be observed not only for the differential but also for the integrated cross sections , provided the laser - dressing of the atomic target is treated in second order perturbation theory and the coupling between hydrogenic bound and continuum states is involved . pacs numbers : 34.80.qb ; 34.50.rk ; 32.80.wr this is the revtex shell .
| 112
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1312.5103
|
we consider two alternative tests to the higher criticism test of donoho and jin [ _ ann . statist . _ * 32 * ( 2004 ) 962994 ] for high - dimensional means under the sparsity of the nonzero means for sub - gaussian distributed data with unknown column - wise dependence . the two alternative test statistics are constructed by first thresholding @xmath0 and @xmath1 statistics based on the sample means , respectively , followed by maximizing over a range of thresholding levels to make the tests adaptive to the unknown signal strength and sparsity . the two alternative tests can attain the same detection boundary of the higher criticism test in [ _ ann . statist . _ * 32 * ( 2004 ) 962994 ] which was established for uncorrelated gaussian data . it is demonstrated that the maximal @xmath1-thresholding test is at least as powerful as the maximal @xmath0-thresholding test , and both the maximal @xmath1 and @xmath0-thresholding tests are at least as powerful as the higher criticism test . ,
| 176
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1603.02284
|
we present the first direct comparison between balmer line and panchromatic sed - based sfrs for @xmath0 galaxies . for this comparison we used 17 star - forming galaxies selected from the mosfire deep evolution field ( mosdef ) survey , with @xmath1 detections for h@xmath2 and at least two ir bands ( _ spitzer_/mips 24@xmath3 m and _ herschel_/pacs 100 and 160@xmath3 m , and in some cases _ herschel_/spire 250 , 350 , and 500@xmath3 m ) . the galaxies have total ir ( @xmath4 m ) luminosities of @xmath5 and star - formation rates ( sfrs ) of @xmath6 . we fit the uv - to - far - ir seds with flexible stellar population synthesis ( fsps ) models which include both stellar and dust emission and compare the inferred sfrs with the sfr(h@xmath2,h@xmath7 ) values corrected for dust attenuation using balmer decrements . the two sfrs agree with a scatter of 0.17 dex . our results imply that the balmer decrement accurately predicts the obscuration of the nebular lines and can be used to robustly calculate sfrs for star - forming galaxies at @xmath0 with sfrs up to @xmath8 . we also use our data to assess sfr indicators based on modeling the uv - to - mid - ir seds or by adding sfr(uv ) and sfr(ir ) , for which the latter is based on the mid - ir only or on the full ir sed . all these sfrs show a poorer agreement with sfr(h@xmath2,h@xmath7 ) and in some cases large systematic biases are observed . finally , we show that the sfr and dust attenuation derived from the uv - to - near - ir sed alone are unbiased when assuming a delayed exponentially declining star - formation history .
| 299
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0707.4176
|
we report the discovery of gas streaming motions along nuclear spiral arms towards the liner nucleus of the galaxy ngc6951 . the observations , obtained using the gmos integral field spectrograph on the gemini north telescope , yielded maps of the flux distributions and gas kinematics in the h@xmath0 , [ nii]@xmath16584 and [ sii]@xmath26717,31 emission lines of the inner 7@xmath315 of the galaxy . this region includes a circumnuclear star - forming ring with radius @xmath4500pc , a nuclear spiral inside the ring and the liner nucleus . the kinematics of the ionized gas is dominated by rotation , but subtraction of a kinematic model of a rotating exponential disk reveals deviations from circular rotation within the nuclear ring which can be attributed to ( 1 ) streaming motions along the nuclear spiral arms and ( 2 ) a bipolar outflow which seems to be associated to a nuclear jet . on the basis of the observed streaming velocities and geometry of the spiral arms we estimate a mass inflow rate of ionized gas of @xmath5m@xmath6yr@xmath7 , which is of the order of the accretion rate necessary to power the liner nucleus of ngc6951 . similar streaming motions towards the nucleus of another galaxy with liner nucleus ngc1097 have been reported by our group in a previous paper . taken together , these results support a scenario in which nuclear spirals are channels through which matter is transferred from galactic scales to the nuclear region to feed the supermassive black hole .
| 253
|
cond-mat0204060
|
we investigate the presence of off - diagonal long - range order in a harmonically confined two - dimensional bose gas . in the noninteracting case , an analytical calculation of the the finite - temperature one - particle density martix provides an exact description of the spatial correlations known to be associated with the existence of a bose - einstein condensate below the transition temperature @xmath0 . we treat the effects of repulsive interactions within the semiclassical hartree - fock - bogliubov approximation and find that even though the system remains in the same _ uncondensed phase _ for all @xmath1 , there appears to be a revival of off - diagonal long - range order for temperatures @xmath2 . we suggest that this reentrant order is related to a phase transition in the system which _ is not _ the bec state .
| 145
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1201.3949
|
recent theoretical works have shown that matter swapping between two parallel braneworlds could occur under the influence of magnetic vector potentials . in our visible world , galactic magnetism possibly produces a huge magnetic potential . as a consequence , this paper discusses the possibility to observe neutron disappearance into another braneworld in certain circumstances . the setup under consideration involves stored ultracold neutrons @xmath0 in a vessel @xmath0 which should exhibit a non - zero probability @xmath1 to disappear into an invisible brane at each wall collision . an upper limit of @xmath1 is assessed based on available experimental results . this value is then used to constrain the parameters of the theoretical model . possible improvements of the experiments are discussed , including enhanced stimulated swapping by artificial means . brane phenomenology , braneworlds , matter disappearance , ultracold neutrons
| 142
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astro-ph0604154
|
we consider modified gravity models involving inverse powers of fourth - order curvature invariants . using these models equivalence to the theory of a scalar field coupled to a linear combination of the invariants , we investigate the properties of the propagating modes . even in the case for which the fourth derivative terms in the field equations vanish , we find that the second derivative terms can give rise to ghosts , instabilities , and superluminal propagation speeds . we establish the conditions which the theories must satisfy in order to avoid these problems in friedmann backgrounds , and show that the late - time attractor solutions generically exhibit superluminally propagating tensor or scalar modes .
| 117
|
1305.5884
|
interference is a major performance bottleneck in heterogeneous network ( hetnet ) due to its multi - tier topological structure . we propose almost blank resource block ( abrb ) for interference control in hetnet . when an abrb is scheduled in a macro bs , a resource block ( rb ) with blank payload is transmitted and this eliminates the interference from this macro bs to the pico bss . we study a two timescale hierarchical radio resource management ( rrm ) scheme for hetnet with _ dynamic abrb _ control . the long term controls , such as dynamic abrb , are adaptive to the large scale fading at a rrm server for co - tier and cross - tier interference control . the short term control ( user scheduling ) is adaptive to the local channel state information within each bs to exploit the _ multi - user diversity_. the two timescale optimization problem is challenging due to the exponentially large solution space . we exploit the sparsity in the _ interference graph _ of the hetnet topology and derive structural properties for the optimal abrb control . based on that , we propose a _ two timescale alternative optimization _ solution for the user scheduling and abrb control . the solution has low complexity and is asymptotically optimal at high snr . simulations show that the proposed solution has significant gain over various baselines . heterogeneous network , dynamic abrb control , two timescale rrm
| 249
|
1111.1968
|
the length spectra of flat three - dimensional dielectric resonators of circular shape were determined from a microwave experiment . they were compared to a semiclassical trace formula obtained within a two - dimensional model based on the effective index of refraction approximation and a good agreement was found . it was necessary to take into account the dispersion of the effective index of refraction for the two - dimensional approximation . furthermore , small deviations between the experimental length spectrum and the trace formula prediction were attributed to the systematic error of the effective index of refraction approximation . in summary , the methods developed in this article enable the application of the trace formula for two - dimensional dielectric resonators also to realistic , flat three - dimensional dielectric microcavities and -lasers , allowing for the interpretation of their spectra in terms of classical periodic orbits .
| 149
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1407.8139
|
in this paper the four - dimensional ( 4-d ) space - velocity cosmological general relativity of carmeli is developed by a general solution of the einstein field equations . the tolman metric is applied in the form @xmath0 where @xmath1 is the metric tensor . we use comoving coordinates @xmath2 , where @xmath3 is the hubble - carmeli time constant , @xmath4 is the universe expansion velocity and @xmath5 , @xmath6 and @xmath7 are the spatial coordinates . we assume that @xmath8 and @xmath9 are each functions of the coordinates @xmath10 and @xmath5 . the vacuum mass density @xmath11 is defined in terms of a cosmological constant @xmath12 , @xmath13 where the carmeli gravitational coupling constant @xmath14 , where @xmath15 is the speed of light in vacuum . this allows the definitions of the effective mass density @xmath16 and effective pressure @xmath17 where @xmath18 is the mass density and @xmath19 is the pressure . then the energy - momentum tensor @xmath20 , \label{abs : t_uv_eff}\ ] ] where @xmath21 is the 4-velocity . the einstein field equations are taken in the form @xmath22 where @xmath23 is the ricci tensor , @xmath24 is carmeli s gravitation constant , where @xmath25 is newton s constant and the trace @xmath26 . by solving the field equations ( [ abs : field - eqs - new ] ) a space - velocity cosmology is obtained analogous to the friedmann - lematre - robertson - walker space - time cosmology . we choose an equation of state such that @xmath27 with an evolving state parameter @xmath28 where @xmath29 is the scale factor and @xmath30 and @xmath31 are constants . carmeli s 4-d space - velocity cosmology is derived as a special case .
| 289
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1404.6494
|
we derive an analytical gauge - invariant formula between the polyakov loop @xmath0 and the dirac eigenvalues @xmath1 in qcd , i.e. , @xmath2 , in ordinary periodic square lattice qcd with odd - number temporal size @xmath3 . here , @xmath4 denotes the dirac eigenstate , and @xmath5 temporal link - variable operator . this formula is a dirac spectral representation of the polyakov loop in terms of dirac eigenmodes @xmath4 . because of the factor @xmath6 in the dirac spectral sum , this formula indicates negligibly small contribution of low - lying dirac modes to the polyakov loop in both confinement and deconfinement phases , while these modes are essential for chiral symmetry breaking . next , we find a similar formula between the wilson loop and dirac modes on arbitrary square lattices , without restriction of odd - number size . this formula suggests a small contribution of low - lying dirac modes to the string tension @xmath7 , or the confining force . these findings support no crucial role of low - lying dirac modes for confinement , i.e. , no direct one - to - one correspondence between confinement and chiral symmetry breaking in qcd , which seems to be natural because heavy quarks are also confined even without light quarks or the chiral symmetry .
| 221
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1601.02715
|
we present the first dedicated x - ray study of the supernova remnant ( snr ) g32.8@xmath00.1 ( kes 78 ) with _ suzaku_. x - ray emission from the whole snr shell has been detected for the first time . the x - ray morphology is well correlated with the emission from the radio shell , while anti - correlated with the molecular cloud found in the snr field . the x - ray spectrum shows not only conventional low - temperature ( @xmath1 kev ) thermal emission in a non - equilibrium ionization state , but also a very high temperature ( @xmath2 kev ) component with a very low ionization timescale ( @xmath3 @xmath4 s ) , or a hard non - thermal component with a photon index @xmath5@xmath62.3 . the average density of the low - temperature plasma is rather low , of the order of @xmath7@xmath8 @xmath4 , implying that this snr is expanding into a low - density cavity . we discuss the x - ray emission of the snr , also detected in tev with h.e.s.s . , together with multi - wavelength studies of the remnant and other gamma - ray emitting snrs , such as w28 and rcw 86 . analysis of a time - variable source , 2xmm j185114.3@xmath0000004 , found in the northern part of the snr , is also reported for the first time . rapid time variability and a heavily absorbed hard x - ray spectrum suggest that this source could be a new supergiant fast x - ray transient .
| 264
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1309.3955
|
recent observations of the diffuse galactic @xmath0-ray emission ( dge ) by the _ fermi _ large area telescope ( _ fermi_-lat ) have shown significant deviations , above a few gev until about 100 gev , from dge models that use the galprop code for the propagation of cosmic ray ( cr ) particles outside their sources in the galaxy and their interaction with the target distributions of the interstellar gas and radiation fields . the surplus of radiation observed is most pronounced in the inner galaxy , where the concentration of cr sources is strongest . the present study investigates this `` _ fermi_-lat galactic plane surplus '' by estimating the @xmath0-ray emission from the sources themselves , which is disregarded in the above dge models . it is shown that indeed the expected hard spectrum of crs , still confined in their sources ( scrs ) , can explain this surplus . the method is based on earlier studies regarding the so - called egret gev excess which by now is generally interpreted as an instrumental effect . the contribution from scrs is predicted to increasingly exceed the dge models also above 100 gev , up to @xmath0-ray energies of about ten tev , where the corresponding surplus exceeds the hadronic part of the dge by about one order of magnitude . above such energies the emission surplus should decrease again with energy due to the finite life - time of the assumed supernova remnant sources . observations of the dge in the inner galaxy at 15 tev with the milagro @xmath0-ray detector and , at tev energies , with the argo - ybj detector are interpreted to provide confirmation of a significant scr contribution to the dge .
| 292
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1501.04962
|
stellar multiplicity lies at the heart of many problems in modern astrophysics , including the physics of star formation , the observational properties of unresolved stellar populations , and the rates of interacting binaries such as cataclysmic variables , x - ray binaries , and type ia supernovae . however , little is known about the stellar multiplicity of field stars in the milky way , in particular about the differences in the multiplicity characteristics between metal - rich disk stars and metal - poor halo stars . in this study we perform a statistical analysis of @xmath014,000 f - type dwarf stars in the milky way through time - resolved spectroscopy with the sub - exposures archived in the sloan digital sky survey . we obtain absolute radial velocity measurements through template cross - correlation of individual sub - exposures with temporal baselines varying from minutes to years . these sparsely sampled radial velocity curves are analyzed using markov chain monte carlo techniques to constrain the very short - period binary fraction for field f - type stars in the milky way . metal - rich disk stars were found to be @xmath1 more likely to have companions with periods shorter than 12 days than metal - poor halo stars .
| 212
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0810.1341
|
observations and numerical magnetohydrodynamic ( mhd ) simulations indicate the existence of outflows and ordered large - scale magnetic fields in the inner region of hot accretion flows . in this paper we present the self - similar solutions for advection - dominated accretion flows ( adafs ) with outflows and ordered magnetic fields . stimulated by numerical simulations , we assume that the magnetic field has a strong toroidal component and a vertical component in addition to a stochastic component . we obtain the self - similar solutions to the equations describing the magnetized adafs , taking into account the dynamical effects of the outflow . we compare the results with the canonical adafs and find that the dynamical properties of adafs such as radial velocity , angular velocity and temperature can be significantly changed in the presence of ordered magnetic fields and outflows . the stronger the magnetic field is , the lower the temperature of the accretion flow will be , and the faster the flow rotates . the relevance to observations is briefly discussed . accretion , accretion discs magnetohydrodynamics : mhd ism : jets and outflow black hole physics
| 194
|
1403.1193
|
we study the possibility that primordial magnetic fields generated in the transition between inflation and reheating posses magnetic helicity , @xmath0 . the fields are induced by stochastic currents of scalar charged particles created during the mentioned transition . we estimate the rms value of the induced magnetic helicity by computing different four - point sqed feynman diagrams . for any considered volume , the magnetic flux across its boundaries is in principle non null , which means that the magnetic helicity in those regions is gauge dependent . we use the prescription given by berger and field and interpret our result as the difference between two magnetic configurations that coincide in the exterior volume . in this case the magnetic helicity gives only the number of magnetic links inside the considered volume . we calculate a concrete value of @xmath0 for large scales and analyze the distribution of magnetic defects as a function of the scale . those defects correspond to regular as well as random fields in the considered volume . we find that the fractal dimension of the distribution of topological defects is @xmath1 . we also study if the regular fields induced on large scales are helical , finding that they are and that the associated number of magnetic defects is independent of the scale . in this case the fractal dimension is @xmath2 . we finally estimate the intensity of fields induced at the horizon scale of reheating , and evolve them until the decoupling of matter and radiation under the hypothesis of inverse cascade of magnetic helicity . the resulting intensity is high enough and the coherence length long enough to have an impact on the subsequent process of structure formation .
| 288
|
math0006056
|
we consider the derived categories of modules over a certain family @xmath0 ( @xmath1 ) of graded rings , and floer cohomology of lagrangian intersections in the symplectic manifolds which are the milnor fibres of simple singularities of type @xmath2 we show that each of these two rather different objects encodes the topology of curves on an @xmath3-punctured disc . we prove that the braid group @xmath4 acts faithfully on the derived category of @xmath0-modules , and that it injects into the symplectic mapping class group of the milnor fibers . the philosophy behind our results is as follows . using floer cohomology , one should be able to associate to the milnor fibre a triangulated category ( its construction has not been carried out in detail yet ) . this triangulated category should contain a full subcategory which is equivalent , up to a slight difference in the grading , to the derived category of @xmath0-modules . the full embedding would connect the two occurrences of the braid group , thus explaining the similarity between them .
| 178
|
1110.1310
|
using the mathisson - papapetrou - dixon ( mpd ) equations , we investigate the trajectories of a spinning particle starting near @xmath0 in a kerr field and moving with the velocity close to the velocity of light ( @xmath0 is the boyer - lindquist radial coordinate of the counter - rotation circular photon orbits ) . first , as a partial case of these trajectories , we consider the equatorial circular orbit with @xmath1 . this orbit is described by the solution that is common for the rigorous mpd equations and their linear spin approximation . then different cases of the nonequatorial motions are computed and illustrated by the typical figures . all these orbits exhibit the effects of the significant gravitational repulsion that are caused by the spin - gravity interaction . possible applications in astrophysics are discussed .
| 141
|
astro-ph0511541
|
we present a search for o i in the spectra of nine @xmath0 qsos taken with keck / hires . we detect six systems with @xmath1 in the redshift intervals where o i @xmath2 falls redward of the ly@xmath3 forest . four of these lie towards sdss j1148 + 5251 ( @xmath4 ) . this imbalance is unlikely to arise from variations in sensitivity among our data or from a statistical fluctuation . the excess o i occurs over a redshift interval that also contains transmission in ly@xmath3 and ly@xmath5 . therefore , if these o i systems represent pockets of neutral gas , then they must occur within or near regions of the igm that are highly ionized . in contrast , no o i is detected towards sdss j1030 + 0524 ( @xmath6 ) , whose spectrum shows complete absorption in ly@xmath3 and ly@xmath5 over @xmath7 . assuming no ionization corrections , we measure mean abundance ratios @xmath8 \rangle = -0.04 \pm 0.06 $ ] , @xmath9 \rangle = -0.31 \pm 0.09 $ ] , and @xmath10 \rangle = -0.34 \pm 0.07 $ ] ( @xmath11 ) , which are consistent with enrichment dominated by type ii supernovae . the o / si ratio limits the fraction of silicon in these systems contributed by metal - free very massive stars to @xmath12 , a result which is insensitive to ionization corrections . the ionic comoving mass densities along the @xmath13 sightlines , including only the detected systems , are @xmath14 , @xmath15 , and @xmath16 .
| 258
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1611.06322
|
rumour detection is hard because the most accurate systems operate retrospectively , only recognising rumours once they have collected repeated signals . by then the rumours might have already spread and caused harm . we introduce a new category of features based on novelty , tailored to detect rumours early on . to compensate for the absence of repeated signals , we make use of news wire as an additional data source . unconfirmed ( novel ) information with respect to the news articles is considered as an indication of rumours . additionally we introduce pseudo feedback , which assumes that documents that are similar to previous rumours , are more likely to also be a rumour . comparison with other real - time approaches shows that novelty based features in conjunction with pseudo feedback perform significantly better , when detecting rumours instantly after their publication .
| 147
|
cond-mat9907009
|
static properties of a bose - fermi mixture of trapped potassium atoms are studied in terms of coupled gross - pitaevskii and thomas - fermi equations for both repulsive and attractive bose - fermi interatomic potentials . qualitative estimates are given for solutions of the coupled equations , and the parameter regions are obtained analytically for the boson - density profile change and for the boson / fermion phase separation . especially , the parameter ratio @xmath0 is found that discriminates the region of the large boson - profile change . these estimates are applied for numerical results for the potassium atoms and checked their consistency . it is suggested that a small fraction of fermions could be trapped without an external potential for the system with an attractive boson - fermion interaction . = -5 mm
| 137
|
1108.2732
|
after a short review of the recent developments in studies of neutrino - nucleus interactions , the predictions for double - differential and integrated charged current - induced quasielastic cross sections are presented within two different relativistic approaches : one is the so - called susa method , based on the superscaling behavior exhibited by electron scattering data ; the other is a microscopic model based on relativistic mean field theory , and incorporating final - state interactions . the role played by the meson - exchange currents in the two - particle two - hole sector is explored and the results are compared with the recent miniboone data .
| 110
|
gr-qc0512008
|
in this work , numerical simulations were used to investigate the gravitational stochastic background produced by coalescences occurring up to @xmath0 of double neutron star systems . the cosmic coalescence rate was derived from monte carlo methods using the probability distributions for forming a massive binary and to occur a coalescence in a given redshift . a truly continuous background is produced by events located only beyond the critical redshift @xmath1 . events occurring in the redshift interval @xmath2 give origin to a popcorn " noise , while those arising closer than @xmath3 produce a shot noise . the gravitational density parameter @xmath4 for the continuous background reaches a maximum around 670 hz with an amplitude of @xmath5 , while the popcorn " noise has an amplitude about one order of magnitude higher and the maximum occurs around a frequency of 1.2 khz . the signal is below the sensitivity of the first generation of detectors but could be detectable by the future generation of ground based interferometers . correlating two coincident advanced - ligo detectors or two ego interferometers , the expected s / n ratio are respectively 0.5 and 10 .
| 193
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0903.2362
|
we derive a formula describing the adiabatically pumped charge through an interacting quantum dot within the scattering matrix and green s function approach . we show that when the tunneling rates between the leads and the dot are varied adiabatically in time , both in modulus and phase , the current induced in the dot consists of two terms , the pumping current and a rectification - like term . the last contribution arises from the time - derivative of the tunneling phase and can have even or odd parity with respect to the pumping phase @xmath0 . the rectification - like term is also discussed in relation to some recent experiments in quantum - dots .
| 117
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astro-ph0310507
|
particles crossing repeatedly the surface of a shock wave can be energized by first order fermi acceleration . the linear theory is successful in describing the acceleration process as long as the pressure of the accelerated particles remains negligible compared to the kinetic pressure of the incoming gas ( the so - called test particle approximation ) . when this condition is no longer fulfilled , the shock is modified by the pressure of the accelerated particles in a nonlinear way , namely the spectrum of accelerated particles and the shock structure determine each other . in this paper we present the first description of the nonlinear regime of shock acceleration when the shock propagates in a medium where seed particles are already present . this case may apply for instance to supernova shocks propagating into the interstellar medium , where cosmic rays are in equipartition with the gas pressure . we find that the appearance of multiple solutions , previously found in alternative descriptions of the nonlinear regime , occurs also for the case of reacceleration of seed particles . moreover , for parameters of concern for supernova shocks , the shock is likely to turn nonlinear mainly due to the presence of the pre - existing cosmic rays , rather than due to the acceleration of new particles from the thermal pool . we investigate here the onset of the nonlinear regime for the three following cases : 1 ) seed particles in equipartition with the gas pressure ; 2 ) particles accelerated from the thermal pool ; 3 ) combination of 1 ) and 2 ) . cosmic rays , high energy , acceleration
| 277
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nucl-ex0401028
|
i start by reviewing existing @xmath0 measurements with particular emphasis on the recent 221 mev @xmath0 measurement at triumf which permitted the weak meson - nucleon coupling constants @xmath1 and @xmath2 to be determined separately for the first time . i then review @xmath3 experiments , with specific details of the @xmath4 experiment now under preparation at los alamos national laboratory . this experiment will provide a clean measurement of the weak pion nucleon coupling , @xmath5 . finally , i discuss @xmath6 parity violation experiments , particularly the gzero experiment under way at jefferson lab in virginia . this experiment will measure the weak form factors @xmath7 and @xmath8 , allowing the distribution of strange quarks in the quark sea to be determined .
| 125
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1107.2405
|
we present a new x - ray analysis of the dwarf seyfert galaxy ngc 4395 , based on two archival _ xmm - newton _ and _ suzaku _ observations . this source is well known for a series of remarkable properties : one of the smallest estimated black hole masses among active galactic nuclei ( of the order of @xmath010@xmath1 ) , intense flux variability on very short time - scales ( a few tens of seconds ) , an unusually flat x - ray continuum ( @xmath2 over the 210 kev energy range ) . ngc 4395 is also characterized by significant variations of the x - ray spectral shape , and here we show that such behaviour can be explained through the partial occultation by circumnuclear cold absorbers with column densities of @xmath010@xmath310@xmath4 @xmath5 . in this scenario , the primary x - ray emission is best reproduced by means of a power law with a standard @xmath6 photon index , consistent with both the spectral slope observed at higher energies and the values typical of local agn . [ firstpage ] galaxies : active galaxies : individual : ngc 4395 x - rays : galaxies .
| 200
|
cond-mat0201263
|
we propose and study a simplified model for the surface and bulk structures of crosslinked polymer gels , into which voids are introduced through templating by surfactant micelles . such systems were recently studied by atomic force microscopy [ m. chakrapani _ et al . _ , e - print cond - mat/0112255 ] . the gel is represented by a frustrated , triangular network of nodes connected by springs of random equilibrium lengths . the nodes represent crosslinkers , and the springs correspond to polymer chains . the boundaries are fixed at the bottom , free at the top , and periodic in the lateral direction . voids are introduced by deleting a proportion of the nodes and their associated springs . the model is numerically relaxed to a representative local energy minimum , resulting in an inhomogeneous , `` clumpy '' bulk structure . the free top surface is defined at evenly spaced points in the lateral ( @xmath0 ) direction by the height of the topmost spring , measured from the bottom layer , @xmath1 . its scaling properties are studied by calculating the root - mean - square surface width and the generalized increment correlation functions @xmath2 . the surface is found to have a nontrivial scaling behavior on small length scales , with a crossover to scale - independent behavior on large scales . as the vacancy concentration approaches the site - percolation limit , both the crossover length and the saturation value of the surface width diverge in a manner that appears to be proportional to the bulk connectivity length . this suggests that a percolation transition in the bulk also drives a similar divergence observed in surfactant templated polyacrylamide gels at high surfactant concentrations .
| 292
|
1206.1843
|
the three - gluon vertex is a basic object of interest in nonabelian gauge theory . it contains important structural information , in particular on infrared divergences , and also figures prominently in the schwinger - dyson equations . at the one - loop level , it has been calculated and analyzed by a number of authors . here we use the worldline formalism to unify the calculations of the scalar , spinor and gluon loop contributions to the one - loop vertex , leading to an extremely compact representation . the susy - related sum rule found by binger and brodsky follows from an off - shell extension of the bern - kosower replacement rules . we explain the relation of the structure of our representation to the low - energy effective action . = 11.6pt
| 137
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hep-ph0603141
|
we introduce a new index of the leptonic cp phase dependence @xmath0 and derive the maximal condition for this index in a simple and general form . @xmath1 may be realized even in the jparc experiment . in the case that the 1 - 3 mixing angle can be observed in the next generation reactor experiments , namely @xmath2 , and nevertheless @xmath3 appearance signal can not be observed in the jparc experiment , we conclude that the cp phase @xmath4 becomes a value around @xmath5 @xmath6 for @xmath7 @xmath8 without depending the uncertainties of solar and atmospheric parameters .
| 100
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0710.0938
|
a latin bitrade @xmath0 is a pair of partial latin squares that define the difference between two arbitrary latin squares @xmath1 and @xmath2 of the same order . a @xmath3-homogeneous bitrade @xmath0 has three entries in each row , three entries in each column , and each symbol appears three times in @xmath4 . cavenagh @xcite showed that any @xmath3-homogeneous bitrade may be partitioned into three transversals . in this paper we provide an independent proof of cavenagh s result using geometric methods . in doing so we provide a framework for studying bitrades as tessellations in spherical , euclidean or hyperbolic space . additionally , we show how latin bitrades are related to finite representations of certain triangle groups .
| 121
|
cs0309029
|
adding small code snippets at key points to existing code fragments is called instrumentation . it is an established technique to debug certain otherwise hard to solve faults , such as memory management issues and data races . dynamic instrumentation can already be used to analyse code which is loaded or even generated at run time . with the advent of environments such as the java virtual machine with optimizing just - in - time compilers , a new obstacle arises : self - modifying code . in order to instrument this kind of code correctly , one must be able to detect modifications and adapt the instrumentation code accordingly , preferably without incurring a high penalty speedwise . in this paper we propose an innovative technique that uses the hardware page protection mechanism of modern processors to detect such modifications . we also show how an instrumentor can adapt the instrumented version depending on the kind of modificiations as well as an experimental evaluation of said techniques . elis , ghent university , sint - pietersnieuwstraat 41 , 9000 gent , belgium @ifundefined
| 184
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1403.1346
|
we report short - time variations in the plasma tail of c/2013 r1(lovejoy ) . a series of short ( two to three minutes ) exposure images with the 8.2-m subaru telescope shows faint details of filaments and their motions over 24 minutes observing duration . we identified rapid movements of two knots in the plasma tail near the nucleus ( @xmath0 3@xmath1 km ) . their speeds are 20 and 25 km s@xmath2 along the tail and 3.8 and 2.2 km s@xmath2 across it , respectively . these measurements set a constraint on an acceleration model of plasma tail and knots as they set the initial speed just after their formation . we also found a rapid narrowing of the tail . after correcting the motion along the tail , the narrowing speed is estimated to be @xmath0 8 km s@xmath2 . these rapid motions suggest the need for high time - resolution studies of comet plasma tails with a large telescope .
| 164
|
1102.0130
|
in this paper we investigate the effect of terminal substituents on the dynamics of spin and charge transport in donor - acceptor substituted polyenes ( @xmath0 ) chains , also known as push - pull polyenes . we employ a long - range correlated model hamiltonian for the @xmath0 system , and time - dependent density matrix renormalization group technique for time propagating the wave packet obtained by injecting a hole at a terminal site , in the ground state of the system . our studies reveal that the end groups do not affect spin and charge velocities in any significant way , but change the amount of charge transported . we have compared these push - pull systems with donor - acceptor substituted polymethine imine ( pmi ) , @xmath1 , systems in which besides electron affinities , the nature of @xmath2 orbitals in conjugation also alternate from site to site . we note that spin and charge dynamics in the pmis are very different from that observed in the case of push - pull polyenes , and within the time scale of our studies , transport of spin and charge leads to the formation of a `` quasi - static '' state .
| 205
|
1312.2352
|
for the better understanding of the astrophysical @xmath0-process the experimental determination of low energy proton- and @xmath1-capture cross sections on heavy isotopes is required . the existing data for the @xmath2mo(p,@xmath0)@xmath3tc reaction are contradictory and strong fluctuation of the cross section is observed which can not be explained by the statistical model . in this paper a new determination of the @xmath2mo(p,@xmath0)@xmath3tc and @xmath4mo(p,@xmath0)@xmath5tc cross sections based on thick target yield measurements are presented and the results are compared with existing data and model calculations . reaction rates of @xmath2mo(p,@xmath0)@xmath3tc at temperatures relevant for the @xmath0-process are derived directly from the measured thick target yields . the obtained rates are a factor of 2 lower than the ones used in astrophysical network calculations . it is argued that in the case of fluctuating cross sections the thick target yield measurement can be more suited for a reliable reaction rate determination . astrophysical gamma - process , reaction cross section , thick target yield , gamma - spectroscopy 24.60.dr , 25.40.lw , 26.30.-k , 27.60.+j
| 174
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astro-ph0008523
|
hst observations have contributed significantly to our knowledge on the behaviour of isolated neutron stars ( inss ) as optical emitters . first , hst has been instrumental both to discover new optical counterparts ( psr b1055 - 52 , psr b1929 + 10 , psr b0950 + 08 ) and to confirm proposed identifications ( psr b0656 + 14 ) . second , hst multicolor photometry provided useful information to characterize the optical emission mechanism(s ) at work in middle - aged inss like psr b0656 + 14 and geminga . last , but not least , the superior angular resolution of the hst allowed both to perform a very accurate morphological study of the plerionic environments of young pulsars ( e.g. the crab and psr b0540 - 69 ) and to perform very accurate astrometric measurements yielding proper motions ( crab , vela , geminga , psr b0656 + 14 ) and parallaxes ( geminga ) . psfig.sty @xmath0 ifc - cnr , via bassini 15 , i-20133 milan , italy @xmath1 st - ecf , karl schwarzschild str.2 , d8574o garching b. munchen , germany @xmath2 pennsylvania state univ . , 525 davey lab , university park , pa 16802 , usa @xmath3 asi , via liegi 26 , i-00198 rome , italy
| 216
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hep-ph9712305
|
in the minimal supergravity model ( msugra ) , as the parameter @xmath0 increases , the charged higgs boson and light bottom squark masses decrease , which can potentially increase contributions from @xmath1 , @xmath2 and @xmath3 loops in the decay @xmath4 . we update a previous qcd improved @xmath4 decay calculation to include in addition the effects of gluino and neutralino loops . we find that in the msugra model , loops involving charginos also increase , and dominate over @xmath5 , @xmath1 , @xmath6 and @xmath7 contributions for @xmath8 . we find for large values of @xmath9 that most of the parameter space of the msugra model for @xmath10 is ruled out due to too large a value of branching ratio @xmath11 . for @xmath12 and large @xmath0 , most of parameter space is allowed , although the regions with the least fine - tuning ( low @xmath13 and @xmath14 ) are ruled out due to too _ low _ a value of @xmath11 . we compare the constraints from @xmath4 to constraints from the neutralino relic density , and to expectations for sparticle discovery at lep2 and the fermilab tevatron @xmath15 colliders . finally , we show that non - universal gut scale soft breaking squark mass terms can enhance gluino loop contributions to @xmath4 decay rate even if these are diagonal .
| 226
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1702.07952
|
we use bbn observational data on primordial abundance of @xmath0 to constrain @xmath1 gravity . the three most studied viable @xmath1 models , namely the power law , the exponential and the square - root exponential are considered , and the bbn bounds are adopted in order to extract constraints on their free parameters . for the power - law model , we find that the constraints are in agreement with those acquired using late - time cosmological data . for the exponential and the square - root exponential models , we show that for realiable regions of parameters space they always satisfy the bbn bounds . we conclude that viable @xmath1 models can successfully satisfy the bbn constraints .
| 120
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astro-ph0408152
|
einstein ( 1936 ) predicted the phenomenon presently known as gravitational lensing ( gl ) . a prime feature of gl is the magnification , because of the gravitational field , of the star visible surface as seen from a distant observer . we show here that nonlinear electrodynamics ( nled ) modifies in a fundamental basis einstein s general relativistic ( gr ) original derivation . the effect becomes apparent by studying the light propagation from a strongly magnetic ( @xmath0 ) pulsar ( smp ) . unlike its gr counterpart , the photon dynamics in nled leads to a new effective gl , which depends also on the @xmath0-field permeating the pulsar . the apparent radius of a smp appears then unexpectedly diminished , by a large factor , as compared to the classical einstein s prediction . this may prove very crucial in determining physical properties of high @xmath0-field stars from their x - ray emission . 0.5 truecm received(07/04/2004 ) revised(16/05/2005 )
| 166
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1509.05721
|
paramagnetic impurities in a quantum spin - liquid can result in kondo effects with highly unusual properties . we have studied the effect of locally exchange - coupling a paramagnetic impurity with the spin-@xmath0 honeycomb kitaev model in its gapless spin - liquid phase . the ( impurity ) scaling equations are found to be insensitive to the sign of the coupling . the weak and strong coupling fixed points are stable , with the latter corresponding to a noninteracting vacancy and an interacting , spin-@xmath1 defect for the antiferromagnetic and ferromagnetic cases respectively . the ground state in the strong coupling limit in both cases has a nontrivial topology associated with a finite @xmath2 flux at the impurity site . for the antiferromagnetic case , this result can be obtained straightforwardly owing to the integrability of the kitaev model with a vacancy . the strong - coupling limit of the ferromagnetic case is however nonintegrable , and we address this problem through exact - diagonalization calculations with finite kitaev fragments . our exact diagonalization calculations indicate that that the weak to strong coupling transition and the topological phase transition occur rather close to each other and are possibly coincident . we also find an intriguing similarity between the magnetic response of the defect and the impurity susceptibility in the two - channel kondo problem .
| 226
|
1008.3893
|
* we model the spreading of a crisis by constructing a global economic network and applying the susceptible - infected - recovered ( sir ) epidemic model with a variable probability of infection . the probability of infection depends on the strength of economic relations between the pair of countries , and the strength of the target country . it is expected that a crisis which originates in a large country , such as the usa , has the potential to spread globally , like the recent crisis . surprisingly we show that also countries with much lower gdp , such as belgium , are able to initiate a global crisis . using the _ k_-shell decomposition method to quantify the spreading power ( of a node ) , we obtain a measure of `` centrality '' as a spreader of each country in the economic network . we thus rank the different countries according to the shell they belong to , and find the 12 most central countries . these countries are the most likely to spread a crisis globally . of these 12 only six are large economies , while the other six are medium / small ones , a result that could not have been otherwise anticipated . furthermore , we use our model to predict the crisis spreading potential of countries belonging to different shells according to the crisis magnitude . *
| 236
|
cond-mat0303169
|
we perform a many - body investigation of the spin dephasing in @xmath0-typed inas quantum wells under moderate magnetic fields in the voigt configuration by constructing and numerically solving the kinetic bloch equations . we obtain the spin dephasing time due to the rashba effect together with the spin conserving scattering such as the electron - phonon , the electron - nonmagnetic impurity as well as the electron - electron coulomb scattering . by varying the initial spin polarization , temperature , impurity density , applied magnetic field and the interface electric field , we are able to study the spin dephasing time under various conditions . for the electron density and quantum well width we study , the many - body effect dominates the spin dephasing . moreover , we find an anomalous resonance peak in the spin dephasing time for high initial spin polarization under moderate magnetic fields .
| 151
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astro-ph0609421
|
we present berkeley illinois maryland association ( bima ) millimeter interferometer observations of giant molecular clouds ( gmcs ) along a spiral arm in m31 . the observations consist of a survey using the compact configuration of the interferometer and follow - up , higher - resolution observations on a subset of the detections in the survey . the data are processed using an analysis algorithm designed to extract gmcs and correct their derived properties for observational biases thereby facilitating comparison with milky way data . the algorithm identifies 67 gmcs of which 19 have sufficient signal - to - noise to accurately measure their properties . the gmcs in this portion of m31 are indistinguishable from those found in the milky way , having a similar size - line width relationship and distribution of virial parameters , confirming the results of previous , smaller studies . the velocity gradients and angular momenta of the gmcs are comparable to the values measured in m33 and the milky way ; and , in all cases , are below expected values based on the local galactic shear . the studied region of m31 has a similar interstellar radiation field , metallicity , toomre @xmath0 parameter , and midplane volume density as the inner milky way , so the similarity of gmc populations between the two systems is not surprising .
| 228
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1301.7536
|
we show that decaying axino dark matter with r - parity violation can explain the observed excess of the 130gev gamma - ray line from the galactic center in the fermi data . the branching fraction of the axino decay into monochromatic photons can be @xmath0 , and constraints from continuum gamma - rays and the anti - proton flux are ameliorated . the peccei - quinn scale of @xmath1gev and the r - parity violation parameter of @xmath2 are cosmologically favored . .5 in ut-13 - 03 + ipmu 13 - 0024 * axino dark matter with r - parity violation and + 130 gev gamma - ray line * .5 in motoi endo@xmath3 , koichi hamaguchi@xmath3 , seng pei liew@xmath4 , + kyohei mukaida@xmath4 and kazunori nakayama@xmath3 .3 in _ @xmath5department of physics , university of tokyo , bunkyo - ku , tokyo 113 - 0033 , japan + @xmath6kavli institute for the physics and mathematics of the universe , university of tokyo , kashiwa 277 - 8583 , japan + _ .5 in
| 176
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astro-ph9711326
|
linear state space modeling determines the hidden autoregressive ( ar ) process in a noisy time series ; for an ar process the time series current value is the sum of current stochastic `` noise '' and a linear combination of previous values . we present preliminary results from modeling a sample of 4 channel batse lad lightcurves . we determine the order of the ar process necessary to model the bursts . the comparison of decay constants for different energy bands shows that structure decays more rapidly at high energy . the resulting models can be interpreted physically ; for example , they may reveal the response of the burst emission region to the injection of energy .
| 119
|
astro-ph0309445
|
we report on the _ xmm - newton _ observations of the young , 102 ms pulsar psr b1706 - 44 . we have found that both a blackbody plus power - law and a magnetized atmospheric model plus power - law provide an excellent fit to the epic spectra . the two scenarios are therefore indistinguishable on a statistical basis , although we are inclined to prefer the latter on physical grounds . in this case , assuming a source distance of @xmath0 kpc , the size of the region responsible for the thermal emission is @xmath1 km , compatible with the surface of a neutron star . a comparison of the surface temperature of psr b1706 - 44 obtained from this fit with cooling curves favor a medium mass neutron star with @xmath2 or @xmath3 , depending on two different models of proton superfluidity in the interior . the large collecting area of _ xmm - newton _ allows us to resolve a substructure in the broad soft x - ray modulation detected by _ chandra _ , revealing the presence of two separate peaks with pulsed fractions of @xmath4 and @xmath5 , respectively .
| 197
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astro-ph9812148
|
models that seek to unify bl lacs and low - power radio galaxies predict that the two types of object should show similar isotropically emitted x - ray emission . testing this is usually limited by difficulties in separating strong x - ray emission from a bl lac nucleus and surrounding low - surface brightness emission . in this paper we report rosat hri observations of the @xmath0 bl lac object pks 0521@xmath1365 . we are able to separate a luminous extended x - ray component from the bright nucleus . using a new radio map , we show that it is unlikely that the extended emission is due to inverse - compton scattering of photons from the active nucleus , and instead interpret it as thermal emission from dense , rapidly cooling gas . this is a more extreme environment than is found in typical fri radio galaxies , and may pose a problem for unified models . x - rays : galaxies galaxies : individual : pks 0521@xmath1365 galaxies : active
| 173
|
0903.4088
|
we present the results from a multi - epoch survey of two regions of m33 using the 3.5 m wiyn telescope . the inner field is located close to the centre of the galaxy , with the outer region situated about @xmath0 kpc away in the southern spiral arm , allowing us to sample a large metallicity range . we have data for 167 fundamental mode cepheids in the two regions . the reddening - free wesenheit magnitude @xmath1 period - luminosity relations were used to establish the distance modulus of each region , with @xmath2 and @xmath3 . the apparent discrepancy between these two results can be explained by the significant metallicity gradient of the galaxy . we determine a value for the metallicity parameter of the period luminosity relation @xmath4 = @xmath5 , consistent with previous measurements . this leads to a metallicity corrected distance modulus to m33 of @xmath6 mag . catalogues cepheids galaxies : individual : m33 galaxies : distances and redshifts
| 166
|
0712.1640
|
a new path - integral theory is developed to calculate the photoemission spectra ( pes ) of correlated many - electron systems . the application to the study on bi@xmath0sr@xmath0cacu@xmath0o@xmath1 ( bi2212 ) and boron - doped diamond ( bdd ) is discussed in details . it is found that the isotopic shift in the angle - resolved photoemission spectra of bi2212 is due to the off - diagonal quadratic electron - phonon ( @xmath2-ph ) coupling , whereas the presence of electron - electron repulsion partially suppresses this effect . for the bdd , a semiconductor - metal phase transition , which is induced by increasing the @xmath2-ph coupling and dopant concentration , is reproduced by our theory . additionally , the presence of fermi edge and phonon step - like structure in pes is found to be due to a co - existence of itinerant and localized electronic states in bdd .
| 154
|
1006.3228
|
we calculate the phase , the temperature and the junction length dependence of the supercurrent for ballistic graphene josephson - junctions . for low temperatures we find non - sinusoidal dependence of the supercurrent on the superconductor phase difference for both short and long junctions . the skewness , which characterizes the deviation of the current - phase relation from a simple sinusoidal one , shows a linear dependence on the critical current for small currents . we discuss the similarities and differences with respect to the classical theory of josephson junctions , where the weak link is formed by a diffusive or ballistic metal . the relation to other recent theoretical results on graphene josephson junctions is pointed out and the possible experimental relevance of our work is considered as well .
| 133
|
0908.1930
|
several interesting correlations among gamma ray bursts ( grb ) prompt and afterglow properties have been found in the recent years . some of these correlations have been proposed also to standardize grb energetics to use them as standard candles in constraining the expansion history of the universe up to @xmath0 . however , given the still unexplained nature of most of these correlations , only the less scattered correlations can be used for constraining the cosmological parameters . the updated correlation is presented . caveats of alternative methods of standardizing grb energetics are discussed . address = inaf - osservatorio astronomico di brera . via e. bianchi 46 , i-23807 merate ( lc ) , italy
| 117
|
1601.06098
|
combining insights from the study of type refinement systems and of monoidal closed chiralities , we show how to reconstruct lawvere s hyperdoctrine of presheaves using a full and faithful embedding into a monoidal closed bifibration living now over the compact closed category of small categories and distributors . besides revealing dualities which are not immediately apparent in the traditional presentation of the presheaf hyperdoctrine , this reconstruction leads us to an axiomatic treatment of directed equality predicates ( modelled by @xmath0 presheaves ) , realizing a vision initially set out by lawvere ( 1970 ) . it also leads to a simple calculus of string diagrams ( representing presheaves ) that is highly reminiscent of c. s. peirce s existential graphs for predicate logic , refining an earlier interpretation of existential graphs in terms of boolean hyperdoctrines by brady and trimble . finally , we illustrate how this work extends to a bifibrational setting a number of fundamental ideas of linear logic .
| 164
|
1702.02541
|
in human societies , people s willingness to compete and strive for better social status as well as being envious of those perceived in some way superior lead to social structures that are intrinsically hierarchical . here we propose an agent - based , network model to mimic the ranking behaviour of individuals and its possible repercussions in human society . the main ingredient of the model is the assumption that the relevant feature of social interactions is each individual s keenness to maximise his or her status relative to others . the social networks produced by the model are homophilous and assortative , as frequently observed in human communities and most of the network properties seem quite independent of its size . however , it is seen that for small number of agents the resulting network consists of disjoint weakly connected communities while being highly assortative and homophilic . on the other hand larger networks turn out to be more cohesive with larger communities but less homophilic . we find that the reason for these changes is that larger network size allows agents to use new strategies for maximizing their social status allowing for more diverse links between them . community formation , opinion formation , social hierarchy
| 209
|
0910.5680
|
electrons and holes in clean , charge - neutral graphene behave like a strongly coupled relativistic liquid . the thermo - electric transport properties of the interacting dirac quasiparticles are rather special , being constrained by an emergent lorentz covariance at hydrodynamic frequency scales . at small carrier density and high temperatures , graphene exhibits signatures of a quantum critical system with an inelastic scattering rate set only by temperature , a conductivity with a nearly universal value , solely due to electron - hole friction , and a very low viscosity . in this regime one finds pronounced deviations from standard fermi liquid behavior . these results , obtained by boltzmann transport theory at weak electron - electron coupling , are fully consistent with the predictions of relativistic hydrodynamics . interestingly , very analogous behavior is found in certain strongly coupled relativistic liquids , which can be analyzed exactly via the ads - cft correspondence , and which had helped identifying and establishing the peculiar properties of graphene .
| 170
|
1611.09097
|
we fitted the @xmath0-kev spectrum of all the observations of the neutron - star low - mass x - ray binary 4u 1636@xmath153 taken with the _ rossi x - ray timing explorer _ using a model that includes a thermal comptonisation component . we found that in the low - hard state the power - law index of this component , @xmath2 , gradually increases as the source moves in the colour - colour diagram . when the source undergoes a transition from the hard to the soft state @xmath2 drops abruptly ; once the source is in the soft state @xmath2 increases again and then decreases gradually as the source spectrum softens further . the changes in @xmath2 , together with changes of the electron temperature , reflect changes of the optical depth in the corona . the lower kilohertz quasi - periodic oscillation ( khz qpo ) in this source appears only in observations during the transition from the hard to the soft state , when the optical depth of the corona is high and changes depends strongly upon the position of the source in the colour - colour diagram . our results are consistent with a scenario in which the lower khz qpo reflects a global mode in the system that results from the resonance between , the disc and/or the neutron - star surface , and the comptonising corona . [ firstpage ] accretion , accretion discs stars : neutron x - rays : binaries stars : individual : 4u 163653
| 256
|
0711.4933
|
in our recent paper @xcite we described a fast cubic ( bispectrum ) estimator of the amplitude of primordial non - gaussianity of local type , @xmath0 , from a combined analysis of the cosmic microwave background ( cmb ) temperature and e - polarization observations . in this paper we generalize the estimator to deal with a partial sky coverage as well as inhomogeneous noise . our generalized estimator is still computationally efficient , scaling as @xmath1 compared to the @xmath2 scaling of the brute force bispectrum calculation for sky maps with @xmath3 pixels . upcoming cmb experiments are expected to yield high - sensitivity temperature and e - polarization data . our generalized estimator will allow us to optimally utilize the combined cmb temperature and e - polarization information from these realistic experiments , and to constrain primordial non - gaussianity .
| 144
|
hep-th0201198
|
the @xmath0superconformal algebra is a @xmath1 algebra with two free parameters . it consists of 3 superconformal currents of spins @xmath2 , @xmath2 and 2 . the algebra is proved to be the symmetry algebra of the coset @xmath3 . at the central charge @xmath4 the algebra coincides with the superconformal algebra associated to manifolds of @xmath5 holonomy . the unitary minimal models of the @xmath0algebra and their fusion structure are found . the spectrum of unitary representations of the @xmath5 holonomy algebra is obtained . * unitary minimal models of @xmath6 + superconformal algebra and + manifolds of @xmath5 holonomy + *
| 103
|
1207.0230
|
we present a model for cosmological inflation which has a natural turn on " and a natural turn off " mechanism . in our model inflation is driven by the hawking - like radiation that occurs in friedman - robertson - walker ( frw ) space - time . this hawking - like radiation results in an effective negative pressure fluid " which leads to a rapid period of expansion in the very early universe . as the universe expands the frw hawking temperature decreases and the inflationary expansion turns off and makes a natural transition to the power law expansion of a radiation dominated universe . the turn on " mechanism is more speculative , but is based on the common hypothesis that in a quantum theory of gravity at very high temperatures / high densities hawking radiation will stop . applying this speculation to the very early universe implies that the hawking - like radiation of the frw space - time will be turned off and therefore the inflation driven by this radiation will turn off .
| 179
|
astro-ph0407539
|
we discuss the systematic uncertainties in the recovery of dark energy properties from the use of baryon acoustic oscillations as a standard ruler . we demonstrate that while unknown relativistic components in the universe prior to recombination would alter the sound speed , the inferences for dark energy from low - redshift surveys are unchanged so long as the microwave background anisotropies can measure the redshift of matter - radiation equality , which they can do to sufficient accuracy . the mismeasurement of the radiation and matter densities themselves ( as opposed to their ratio ) would manifest as an incorrect prediction for the hubble constant at low redshift . in addition , these anomalies do produce subtle but detectable features in the microwave anisotropies .
| 126
|
1308.1188
|
the cohesive energies of solids calculated using mglj eos proposed by sun jiuxun ( sun jiuxun , j. phys . : condens . matter 17 , l103 ( 2005 ) ) are seen to be erroneous . also we observed that the thermodynamic properties calculated using the mglj potential diverge for materials whose pressure derivative of bulk modulus at equilibrium is less than @xmath0 . thus the mglj potential can not be used in liquid state theories and molecular simulations to obtain thermodynamic properties . sun jiuxun @xcite recently suggested an equation of state(eos ) based on modified generalized lennard - jones ( mglj ) potential . the mglj eos is obtained by modifying the generalized lennard - jones potential in such a way that the eos obtained is volume analytic and satisfies spinodal condition . the mglj eos has three parameters and are related to lattice parameter , bulk modulus and derivative of the bulk modulus at equilibrium . in the paper@xcite it was shown that the pressure ( p ) vs compression ratio curve obtained using the mglj eos is quite accurate . the idea of generating an eos starting from a potential is interesting and has the advantage that the potential of the material also can be known in addition to the eos . however , we found some problems with the mglj eos and the potential so obtained from it . they are , ( a ) the cohesive energy calculated from the mglj eos is quite erroneous and ( b ) the thermodynamic properties calculated using the mglj potential with parameters of sun diverge for most of the materials . details about each problem are as follows :
| 283
|
hep-ph9903304
|
based on the self - consistent scheme beyond mean - field approximation in the large @xmath0 expansion , including current quark mass explicitly , a general scheme of su(2 ) njl model is developed . to ensure the quark self - energy expanded in the proper order of @xmath0 , an approximate internal meson propagator is deduced , which is in order of @xmath1 . in our scheme , adopting the method of external momentum expansion , all the feynman diagrams are calculated in a unified way by only expanding the quark propagator . our numerical results show , that different from the mean field approximation in which the explicitly chiral symmetry breaking is invisible , the effect of finite pion mass can be seen clearly when beyond mean - field approximation .
| 133
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