article_id
stringlengths 9
15
| abstract_text
stringlengths 390
2.07k
| token_count
int64 100
300
|
|---|---|---|
1107.0571
|
a new , improved split - step backward euler ( ssbe ) method is introduced and analyzed for stochastic differential delay equations(sddes ) with generic variable delay . the method is proved to be convergent in mean - square sense under conditions ( assumption [ olc ] ) that the diffusion coefficient @xmath0 is globally lipschitz in both @xmath1 and @xmath2 , but the drift coefficient @xmath3 satisfies one - sided lipschitz condition in @xmath1 and globally lipschitz in @xmath2 . further , exponential mean - square stability of the proposed method is investigated for sddes that have a negative one - sided lipschitz constant . our results show that the method has the unconditional stability property in the sense that it can well reproduce stability of underlying system , without any restrictions on stepsize @xmath4 . numerical experiments and comparisons with existing methods for sddes illustrate the computational efficiency of our method . + * ams subject classification : * 60h35,65c20,65l20 . + * key words : * split - step backward euler method , strong convergence , one - sided lipschitz condition , exponential mean - square stability , mean - square linear stability
| 196
|
1702.07221
|
we develop an approach to liquid thermodynamics based on collective modes . we perform extensive molecular dynamics simulations of noble , molecular and metallic liquids and provide the direct evidence that liquid energy and specific heat are well - described by the temperature dependence of the frenkel ( hopping ) frequency . the agreement between predicted and calculated thermodynamic properties is seen in the notably wide range of temperature spanning tens of thousands of kelvin . the range includes both subcritical liquids and supercritical fluids . we discuss the structural crossover and inter - relationships between structure , dynamics and thermodynamics of liquids and supercritical fluids .
| 107
|
astro-ph0308293
|
there are several physical processes to remove gas from galaxies in clusters , with subsequent starvation and star formation quenching : tidal interactions between galaxies , or tidal stripping from the cluster potential itself , interactions with the hot intra - cluster medium ( icm ) through ram pressure , turbulent or viscous stripping , or also outflows from star formation of nuclear activity , we review the observational evidence for all processes , and numerical simulations of galaxies in clusters which support the respective mechanisms . this allows to compare their relative efficiencies , all along cluster formation .
| 100
|
1208.2403
|
ieee 802.15.4 standard is designed for low power and low data rate applications with high reliability . it operates in beacon enable and non - beacon enable modes . in this work , we analyze delay , throughput , load , and end - to - end delay of non - beacon enable mode . analysis of these parameters are performed at varying data rates . evaluation of non beacon enabled mode is done in a 10 node network . we limit our analysis to non beacon or unslotted version because , it performs better than other . protocol performance is examined by changing different medium access control ( mac ) parameters . we consider a full size mac packet with payload size of 114 bytes . in this paper we show that maximum throughput and lowest delay is achieved at highest data rate . ieee 802.15.4 , throughput , delay , end - to - end , load
| 159
|
1403.7867
|
we consider the problem of hypothesis testing in the situation when the first hypothesis is simple and the second one is local one - sided composite . we describe the choice of the thresholds and the power functions of the score function test , of the general likelihood ratio test , of the wald test and of two bayes tests in the situation when the intensity function of the observed inhomogeneous poisson process is smooth with respect to the parameter . it is shown that almost all these tests are asymptotically uniformly most powerful . the results of numerical simulations are presented . msc 2010 classification : 62m02 , 62f03 , 62f05 . _ key words : _ hypothesis testing , inhomogeneous poisson processes , asymptotic theory , composite alternatives , regular situation .
| 134
|
astro-ph0512031
|
we demonstrate that gravitationally lensed quasars are easily recognized using image subtraction methods as time variable sources that are spatially extended . for galactic latitudes @xmath0 , lensed quasars dominate the population of spatially extended variable sources , although there is some contamination from variable star pairs , variable star - quasar pairs and binary quasars that can be easily controlled using other information in the survey such as the object light curves and colors . this will allow planned large - scale synoptic surveys to find lensed quasars almost down to their detection limits without the need for extensive follow - up observations .
| 105
|
1403.7013
|
salkuyeh proposed the picard - hss iteration method to solve the absolute value equation ( ave ) , which is a class of non - differentiable np - hard problem . to further improve its performance , a nonlinear hss - like iteration method is proposed . compared to that the picard - hss method is an inner - outer double - layer iteration scheme , the hss - like iteration is only a monolayer and the iteration vector could be updated timely . some numerical experiments are used to demonstrate that the nonlinear hss - like method is feasible , robust and effective . absolute value equation , nonlinear hss - like iteration , fixed point iteration , positive definite 15a06,65f10,65h10
| 122
|
1002.0469
|
we numerically investigate the excitation and temporal evolution of oscillations in a two - dimensional coronal arcade by including the three - dimensional propagation of perturbations . the time evolution of impulsively generated perturbations is studied by solving the linear , ideal magnetohydrodynamic ( mhd ) equations in the zero-@xmath0 approximation . as we neglect gas pressure the slow mode is absent and therefore only coupled mhd fast and alfvn modes remain . two types of numerical experiments are performed . first , the resonant wave energy transfer between a fast normal mode of the system and local alfvn waves is analyzed . it is seen how , because of resonant coupling , the fast wave with global character transfers its energy to alfvnic oscillations localized around a particular magnetic surface within the arcade , thus producing the damping of the initial fast mhd mode . second , the time evolution of a localized impulsive excitation , trying to mimic a nearby coronal disturbance , is considered . in this case , the generated fast wavefront leaves its energy on several magnetic surfaces within the arcade . the system is therefore able to trap energy in the form of alfvnic oscillations , even in the absence of a density enhancement such as that of a coronal loop . these local oscillations are subsequently phase - mixed to smaller spatial scales . the amount of wave energy trapped by the system via wave energy conversion strongly depends on the wavelength of perturbations in the perpendicular direction , but is almost independent from the ratio of the magnetic to density scale heights .
| 271
|
1510.07090
|
the social connections people form online affect the quality of information they receive and their online experience . although a host of socioeconomic and cognitive factors were implicated in the formation of offline social ties , few of them have been empirically validated , particularly in an online setting . in this study , we analyze a large corpus of geo - referenced messages , or tweets , posted by social media users from a major us metropolitan area . we linked these tweets to us census data through their locations . this allowed us to measure emotions expressed in the tweets posted from an area , the structure of social connections , and also use that area s socioeconomic characteristics in analysis . we find that at an aggregate level , places where social media users engage more deeply with less diverse social contacts are those where they express more negative emotions , like sadness and anger . demographics also has an impact : these places have residents with lower household income and education levels . conversely , places where people engage less frequently but with diverse contacts have happier , more positive messages posted from them and also have better educated , younger , more affluent residents . results suggest that cognitive factors and offline characteristics affect the quality of online interactions . our work highlights the value of linking social media data to traditional data sources , such as us census , to drive novel analysis of online behavior .
| 253
|
astro-ph9709154
|
we present a detailed analysis of the ionisation state and heavy element abundances in the intergalactic medium ( igm ) . the civ doublet is shown by 30 % of the 182 selected optically thin clouds in 10 qso lines of sight . direct metallicy calculations have been performed on individual systems with detected civ and siiv ( 10% of the sample ) varying the uv photoionising source , cloud density and size and silicon relative abundance . the best solutions for carbon content in this subsample ( redshift coverage @xmath0 ) span between 1/6 and 1/300 of the solar value with no evidence of redshift evolution in both the metallicity and the ionising source . global properties of the whole sample indicate that the metallicity in clouds with civ and siiv is not typical of the igm . the redshift evolution of the uvb is one of the possible sources of the observed siiv / civ trend presented by cowie and collaborators during this meeting . future detection of heavy elements in lower hi column density ( @xmath1 ) clouds relies on the presence of ovi and nv at @xmath2 .
| 192
|
1606.00124
|
content delivery success in wireless caching helper networks depends mainly on cache - based channel selection diversity and network interference . for given channel fading and network geometry , both channel selection diversity and network interference dynamically vary according to what and how the caching helpers cache at their finite storage space . we study probabilistic content placement ( or caching placement ) to desirably control cache - based channel selection diversity and network interference in a stochastic wireless caching helper network , with sophisticated considerations of wireless fading channels , interactions among multiple users such as interference and loads at caching helpers , and arbitrary memory size . using stochastic geometry , we derive optimal caching probabilities in closed form to maximize the average success probability of content delivery and propose an efficient algorithm to find the solution in a noise - limited network . in an interference - limited network , based on a lower bound of the average success probability of content delivery , we find near - optimal caching probabilities in closed form to control the channel selection diversity and the network interference . we numerically verify that the proposed content placement is superior to other comparable content placement strategies . probabilistic content placement , caching probability , stochastic geometry , channel selection diversity
| 218
|
0706.3780
|
we first show that a large amount of metal - poor gas is stripped from the small magellanic cloud ( smc ) and fallen into the large magellanic cloud ( lmc ) during the tidal interaction between the smc , the lmc , and the galaxy over the last 2 gyrs . we propose that this metal - poor gas can closely be associated with the origin of lmc s young and intermediate - age stars and star clusters with distinctively low - metallicities with [ fe / h ] @xmath0 . we numerically investigate whether gas initially in the outer part of the smc s gas disk can be stripped during the lmc - smc - galaxy interaction and consequently can pass through the central region ( @xmath1 kpc ) of the lmc . we find that about 0.7 % and 18 % of the smc s gas can pass through the central region of the lmc about 1.3 gyr ago and 0.2 gyr ago , respectively . the possible mean metallicity of the replenished gas from the smc to lmc is about [ fe / h ] = -0.9 to -1.0 for the two interacting phases . these results imply that the lmc can temporarily replenish gas supplies through the sporadic accretion and infall of metal - poor gas from the smc . these furthermore imply that if these gas from the smc can collide with gas in the lmc to form new stars in the lmc , the metallicities of the stars can be significantly lower than those of stars formed from gas initially within the lmc . [ firstpage ] magellanic clouds galaxies : structure galaxies : kinematics and dynamics galaxies : halos galaxies : star clusters
| 291
|
astro-ph0505235
|
we present simulations of triton s post - capture orbit that confirm the importance of kozai - type oscillations in its orbital elements . in the context of the tidal orbital evolution model , these variations require average pericenter distances much higher than previously published , and the timescale for the tidal orbital evolution of triton becomes longer than the age of the solar system . recently - discovered irregular satellites present a new constraint on triton s orbital history . our numerical integrations of test particles indicate a timescale for triton s orbital evolution to be less than @xmath0 yrs for a reasonable number of distant satellites to survive triton s passage . this timescale is inconsistent with the exclusively tidal evolution ( time scale of @xmath1 yrs ) , but consistent with the interestion with the debris from satellite - satellite collisions . any major regular satellites will quickly collide among themselves after being perturbed by triton , and the resulting debris disk would eventually be swept up by triton ; given that the total mass of the uranian satellite system is 40% of that of triton , large scale evolution is possible . this scenario could have followed either collisional or the recently - discussed three - body - interaction - based capture .
| 217
|
0904.3958
|
the akari and spitzer satellites provided an unique opportunity to observe a variety of stars , which are considered as departing from the asymptotic giant branch ( agb ) and have started their post - agb evolution recently . most of these stars are absent optically and are bright in the mid - ir wavelength range . spectra of close to 200 objects have been obtained . for all of them the @xmath0 m spectral energy distribution has been constructed using photometric data from various surveys . we report here on the results of spitzer observations of 88 iras selected post - agb candidates and discuss them in comparison to the results of the akari observations of post - agb candidates reported elsewhere in these proceedings . the dust compositions can be divided broadly in oxygen- and carbon - rich types , but a variety of intermediate types have been found . among the oxygen - rich stars amorphous dust prevails , but a few sources show emission features from crystalline dust . the spectra from carbon - rich shells may be completely featureless , may show emission features from pahs or a molecular absorption line from c@xmath1h@xmath1 . we found also sources with a neon emission line at @xmath2 m . more than a third of all sources show a near - infrared excess at @xmath3 m and almost all of them show evidence of c - rich dust in their shells . we postulate that the emerging post - agb wind after the end of agb evolution contains always carbon - rich dust irrespective of the chemistry of the former agb star .
| 275
|
1512.05240
|
this paper continues a study initiated in @xcite , on the localization transition of a lattice free field on @xmath0 interacting with a quenched disordered substrate that acts on the interface when its height is close to zero . the substrate has the tendency to localize or repel the interface at different sites . a transition takes place when the average pinning potential @xmath1 goes past a threshold @xmath2 : from a delocalized phase @xmath3 , where the field is macroscopically repelled by the substrate to a localized one @xmath4 where the field sticks to the substrate . our goal is to investigate the effect of the presence of disorder on this phase transition . we focus on the two dimensional case @xmath5 for which we had obtained so far only limited results . we prove that the value of @xmath6 is the same as for the annealed model , for all values of @xmath7 and that in a neighborhood of @xmath2 . moreover we prove that , in contrast with the case @xmath8 where the free energy has a quadratic behavior near the critical point , the phase transition is of infinite order @xmath9 + 2010 _ mathematics subject classification : 60k35 , 60k37 , 82b27 , 82b44 _ + _ keywords : lattice gaussian free field , disordered pinning model , localization transition , critical behavior , disorder relevance , co - membrane model _
| 237
|
1210.0174
|
we propose the concept of a terahertz ( thz ) uncooled bolometer based on n - type and p - type graphene layers ( gls ) , constituting the absorbing regions , connected by an array of undoped graphene nanoribbons ( gnrs ) . the gls absorb the thz radiation with the gnr array playing the role of the barrier region ( resulting in ngl - gnr - pgl bolometer ) . the absorption of the incident thz radiation in the gl n- and p- regions leads to variations of the effective temperature of electrons and holes and of their fermi energy resulting in the variation of the current through the gnrs . using the proposed device model , we calculate the dark current and the bolometer responsivity as functions of the gnr energy gap , applied voltage , and the thz frequency . we demonstrate that the proposed bolometer can surpass the hot - electron bolometers using traditional semiconductor heterostructures .
| 162
|
physics0304084
|
energies of @xmath0 ( @xmath1 ) and @xmath2 states in neutral ag and ag - like ions with nuclear charges @xmath3 are calculated using relativistic many - body perturbation theory . reduced matrix elements , oscillator strengths , transition rates and lifetimes are calculated for the 17 possible @xmath4 and @xmath5 electric - dipole transitions . third - order corrections to energies and dipole matrix elements are included for neutral ag and for ions with @xmath6 . second - order corrections are included for @xmath7 . comparisons are made with available experimental data for transition energies and lifetimes . correlation energies and transition rates are shown graphically as functions of nuclear charge @xmath8 for selected cases . these calculations provide a theoretical benchmark for comparison with experiment and theory .
| 130
|
astro-ph0510206
|
although some of the properties of the caustics in planetary microlensing have been known , our understanding of them is mostly from scattered information based on numerical approaches . in this paper , we conduct a comprehensive and analytic analysis of the properties of the planetary caustics , which are one of the two sets of caustics in planetary microlensing , those located away from the central star . under the perturbative approximation , we derive analytic expressions for the location , size , and shape of the planetary caustic as a function of the star - planet separation and the planet / star mass ratio . based on these expressions combined with those for the central caustic , which is the other set of caustics located close to the central star , we compare the similarities and differences between the planetary and central caustics . we also present the expressions for the size ratio between the two types of caustics and for the condition of the merging of the two types of caustics . these analytic expressions will be useful in understanding the dependence of the planetary lensing behavior on the planet parameters and thus in interpreting the planetary lensing signals .
| 203
|
1505.02096
|
we report on _ nustar _ , _ xmm - newton _ and _ swift _ observations of the gamma - ray binary 1fgl j1018.6@xmath05856 . we measure the orbital period to be @xmath1 days using _ swift _ data spanning 1900 days . the orbital period is different from the 2011 gamma - ray measurement which was used in the previous x - ray study of @xcite using @xmath2400days of _ swift _ data , but is consistent with a new gamma - ray solution reported in 2014 . the light curve folded on the new period is qualitatively similar to that reported previously , having a spike at phase 0 and broad sinusoidal modulation . the x - ray flux enhancement at phase 0 occurs more regularly in time than was previously suggested . a spiky structure at this phase seems to be a persistent feature , although there is some variability . furthermore , we find that the source flux clearly correlates with the spectral hardness throughout all orbital phases , and that the broadband x - ray spectra measured with _ nustar _ , _ xmm - newton _ , and _ swift _ are well fit with an unbroken power - law model . this spectrum suggests that the system may not be accretion - powered .
| 222
|
0905.4831
|
mesoscopic hydrodynamic equations are solved to investigate the dynamics of nanodroplets positioned near a topographic step of the supporting substrate . our results show that the dynamics depends on the characteristic length scales of the system given by the height of the step and the size of the nanodroplets as well as on the constituting substances of both the nanodroplets and the substrate . the lateral motion of nanodroplets far from the step can be described well in terms of a power law of the distance from the step . in general the direction of the motion depends on the details of the effective laterally varying intermolecular forces . but for nanodroplets positioned far from the step it is solely given by the sign of the hamaker constant of the system . moreover , our study reveals that the steps always act as a barrier for transporting liquid droplets from one side of the step to the other .
| 159
|
1010.5907
|
we investigate the use of the multiple optimised parameter estimation and data compression algorithm ( moped ) for data compression and faster evaluation of likelihood functions . since moped only guarantees maintaining the fisher matrix of the likelihood at a chosen point , multimodal and some degenerate distributions will present a problem . we present examples of scenarios in which moped does faithfully represent the true likelihood but also cases in which it does not . through these examples , we aim to define a set of criteria for which moped will accurately represent the likelihood and hence may be used to obtain a significant reduction in the time needed to calculate it . these criteria may involve the evaluation of the full likelihood function for comparison . [ firstpage ] methods : data analysis methods : statistical
| 138
|
1212.5640
|
due to its proximity , the mass of the supermassive black hole in the nucleus of andromeda galaxy ( m31 ) , the most massive black hole in the local group of galaxies , has been measured by several methods involving the kinematics of a stellar disk that surrounds it . we report here the discovery of an eccentric h@xmath0 emitting disk around the black hole at the center of m31 and show how modeling this disk can provide an independent determination of the mass of the black hole . our model implies a mass of @xmath1 for the central black hole , consistent with the average of determinations by methods involving stellar dynamics , and compatible ( at 1@xmath2 level ) with measurements obtained from the most detailed models of the stellar disk around the central black hole . this value is also consistent with the @xmath3 relation . in order to make a comparison , we applied our simulation on the stellar kinematics in the nucleus of m31 and concluded that the parameters obtained for the stellar disk are not formally compatible with the parameters obtained for the h@xmath0 emitting disk . this result suggests that the stellar and the h@xmath0 emitting disks are intrinsically different from each other . a plausible explanation is that the h@xmath0 emission is associated with a gaseous disk . this hypothesis is supported by the detection of traces of weaker nebular lines in the nuclear region of m31 . however , we can not exclude the possibility that the h@xmath0 emission is , at least partially , generated by stars .
| 269
|
1611.05304
|
recent literature on the aharonov - bohm effect has raised fundamental questions on the classical correspondence of this effect and the physical reality of the electromagnetic potentials in quantum mechanics . reappraisal on feynman s approach to the classical limit of ab effect is presented . the critique throws light on the significance of quantum interference and quantum phase shifts in any such classical correspondence . detailed analysis shows that feynman arguments are untenable on physical grounds and the claim made in the original ab paper that this effect had no classical analog seems valid . the importance of nonintegrable phase factor distinct from the ab phase factor , here termed as fock - london - weyl phase factor for the historical reasons , is underlined in connection with the classical aspects / limits . a topological approach incorporating the physical significance of the interaction field momentum is proposed . a new idea emerges from this approach that attributes the origin of the ab effect to the exchange of modular angular momentum .
| 173
|
1111.7174
|
motivated by recent scanning tunneling and photoemission spectroscopy measurements on self - organized gold chains on a germanium surface we reinvestigate the local single - particle spectral properties of luttinger liquids . in the first part we use the bosonization approach to exactly compute the local spectral function of a simplified field theoretical low - energy model and take a closer look at scaling properties as a function of the ratio of energy and temperature . translational invariant luttinger liquids as well as those with an open boundary ( cut chain geometry ) are considered . we explicitly show that the scaling functions of both setups have the same analytic form . the scaling behavior suggests a variety of consistency checks which can be performed on measured data to experimentally verify luttinger liquid behavior . in a second part we approximately compute the local spectral function of a microscopic lattice model the extended hubbard model close to an open boundary using the functional renormalization group . we show that as a function of energy and temperature it follows the field theoretical prediction in the low - energy regime and point out the importance of nonuniversal energy scales inherent to any microscopic model . the spatial dependence of this spectral function is characterized by oscillatory behavior and an envelope function which follows a power law both in accordance with the field theoretical continuum model . interestingly , for the lattice model we find a phase shift which is proportional to the two - particle interaction and not accounted for in the standard bosonization approach to luttinger liquids with an open boundary . we briefly comment on the effects of several one - dimensional branches cutting the fermi energy and rashba spin - orbit interaction .
| 294
|
1209.4105
|
transverse momentum integrated multiplicities in the central region of @xmath0 collisions at lhc energies satisfy koba - nielsen - olesen scaling . we attempt to relate this finding to multiplicity distributions of soft gluons . kno scaling emerges if the effective theory describing color charge fluctuations at a scale on the order of the saturation momentum is approximately gaussian . from an evolution equation for quantum corrections which includes both saturation as well as fluctuations we find that evolution with the qcd @xmath1-function satisfies kno scaling while fixed - coupling evolution does not . thus , non - linear saturation effects and running - coupling evolution are both required in order to reproduce geometric scaling of the dis cross section and kno scaling of virtual dipoles in a hadron wave function .
| 132
|
astro-ph0604332
|
we report on the detection in sloan digital sky survey data of a @xmath0-long tidal stream of stars , extending from ursa major to cancer . the stream has no obvious association with the orbit of any known cluster or galaxy . the contrast of the detected stream is greatest when using a star count filter that is matched to the color - magnitude distribution of stars in m 13 , which suggests that the stars making up the stream are old and metal poor . the visible portion of the stream is very narrow and about 8.5 kpc above the galactic disk , suggesting that the progenitor is or was a globular cluster . while the surface density of the stream varies considerably along its length , its path on the sky is very smooth and uniform , showing no evidence of perturbations by large mass concentrations in the nearby halo . while definitive constraints can not be established without radial velocity information , the stream s projected path and estimates of its distance suggest that we are observing the stream near the perigalacticon of its orbit .
| 189
|
1312.0303
|
we propose algorithms , based on the multi - scale entanglement renormalization ansatz , to obtain the ground state of quantum critical systems in the presence of boundaries , impurities , or interfaces . by exploiting the theory of minimal updates [ ref . : g. evenbly and g. vidal , arxiv:1307.0831 ] , the ground state is completely characterized in terms of a number of variational parameters that is independent of the system size , even though the presence of a boundary , an impurity , or an interface explicitly breaks the translation invariance of the host system . similarly , computational costs do not scale with the system size , allowing the thermodynamic limit to be studied directly and thus avoiding finite size effects e.g. when extracting the universal properties of the critical system .
| 137
|
0810.4605
|
we study the changes in the fermi surface with electron doping in the lafeaso@xmath0f@xmath1 superconductors with density - functional supercell calculations using the linearized augmented planewave ( lapw ) method . the supercell calculations with explicit f substitution are compared with those obtained from the virtual crystal approximation ( vca ) and from a simple rigid band shift . we find significant differences between the supercell results and those obtained from the rigid - band shift with electron doping , although quite remarkably the supercell results are in good agreement with the virtual crystal approximation ( vca ) where the nuclear charges of the o atoms are slightly increased to mimic the addition of the extra electrons . with electron doping , the two cylindrical hole pockets along @xmath2 shrink in size , and the third hole pocket around @xmath3 disappears for an electron doping concentration in excess of about 7 - 8% , while the two elliptical electron cylinders along @xmath4 expand in size . the spin - orbit coupling does not affect the fermi surface much except to somewhat reduce the size of the third hole pocket in the undoped case . we find that with the addition of the electrons the antiferromagnetic state becomes energetically less stable as compared to the nonmagnetic state , indicating that the electron doping may provide an extra degree of stability to the formation of the superconducting ground state .
| 238
|
nlin0503060
|
an adequate characterization of the dynamics of hamiltonian systems at physically relevant scales has been largely lacking . here we investigate this fundamental problem and we show that the finite - scale hamiltonian dynamics is governed by effective dynamical invariants , which are significantly different from the dynamical invariants that describe the asymptotic hamiltonian dynamics . the effective invariants depend both on the scale of resolution and the region of the phase space under consideration , and they are naturally interpreted within a framework in which the nonhyperbolic dynamics of the hamiltonian system is modeled as a chain of hyperbolic systems . [ phys . rev . e * 71 * , 036215 ( 2005 ) ]
| 117
|
1410.3080
|
a bayesian compressive sensing framework is developed for video reconstruction based on the color coded aperture compressive temporal imaging ( cacti ) system . by exploiting the three dimension ( 3d ) tree structure of the wavelet and discrete cosine transformation ( dct ) coefficients , a bayesian compressive sensing inversion algorithm is derived to reconstruct ( up to 22 ) color video frames from a _ single _ monochromatic compressive measurement . both simulated and real datasets are adopted to verify the performance of the proposed algorithm . compressive sensing , video , bayesian , tree structure , wavelet
| 100
|
0908.3900
|
we introduce the class of intermediate mass binaries named double periodic variables ( dpvs ) , characterized by orbital photometric variability ( ellipsoidal or eclipsing ) in time scales of few days and a long photometric cycle lasting roughly 33 times the orbital period . after a search conducted in the ogle and asas catalogues , we identified 114 of these systems in the magellanic clouds and 11 in the galaxy . we present results of our photometric and spectroscopic campaigns on dpvs conducted during the last years , outlining their main observational characteristics . we present convincing evidence supporting the view that dpvs are semidetached interacting binaries with optically thick discs around the gainer , that experience regular cycles of mass loss into the interstellar medium . the mechanism regulating this long - term process still is unknown but probably is related to relaxation cycles of the circumprimary disc . a key observational fact is the modulation of the @xmath0 of hei 5875 with the long cycle in v393sco . the dpv evolution stage is investigated along with their relationship to algols and w serpentid stars . we conclude that dpvs can be used to test models of non - conservative binary evolution including the formation of circumbinary discs .
| 211
|
cond-mat0104532
|
we study nonlinear random resistor diode networks at the transition from the non percolating to the directed percolating phase . the resistor - like bonds and the diode - like bonds under forward bias voltage obey a generalized ohm s law , @xmath0 . based on general grounds as symmetries and relevance we develop a field theoretic model . we focus on the average two - port resistance , which is governed at the transition by the resistance exponent @xmath1 . by employing renormalization group methods we calculate @xmath1 for arbitrary @xmath2 to one - loop order . then we address the fractal dimensions characterizing directed percolation clusters . via considering distinct values of the nonlinearity @xmath2 , we determine the dimension of the red bonds , the chemical path and the backbone to two - loop order . # 1@xmath3#1
| 141
|
astro-ph0208026
|
we investigate the environments of quasars such as number distribution of galaxies using a semi - analytic model which includes both galaxy and quasar formations based on the hierarchical clustering scenario . we assume that a supermassive black hole is fueled by accretion of cold gas and that it is a source of quasar activity during a major merger of the quasar host galaxy with another galaxy . this major merger causes spheroid formation of the host galaxy . our model can reproduce not only general form of the galaxy luminosity functions in the local universe but also the observed relation between a supermassive black hole mass and a spheroid luminosity , the present black hole mass function and the quasar luminosity functions at different redshifts . using this model , we predict the mean number of quasars per halo , bias parameter of quasars and the probability distribution of the number of galaxies around quasars . in our model , analysis of the mean number of quasars per halo shows that the spatial distribution of galaxies is different from that of quasars . furthermore , we found from calculation of the probability distribution of galaxy numbers that at @xmath0 , most quasars are likely to reside in galaxy groups . on the other hand , at @xmath1 most quasars seem to reside in more varied environments than at a lower redshift ; quasars reside in environments ranging from small groups of galaxies to clusters of galaxies . comparing these predictions with observations in future will enable us to constrain our quasar formation model .
| 265
|
1610.03021
|
we explore the spectral properties of the time - dependent maxwell s equations for a plane interface between a metamaterial represented by the drude model and the vacuum , which fill respectively complementary half - spaces . we construct explicitly a generalized fourier transform which diagonalizes the hamiltonian that describes the propagation of transverse electric waves . this transform appears as an operator of decomposition on a family of generalized eigenfunctions of the problem . it will be used in a forthcoming paper to prove both limiting absorption and limiting amplitude principles . * keywords : * negative index materials ( nims ) , drude model , maxwell equations , generalized eigenfunctions .
| 113
|
astro-ph0602520
|
when integrals in the standard tremaine - weinberg method are evaluated for the case of a realistic model of a doubly barred galaxy , their modifications introduced by the second rotating pattern are in accord with what can be derived from a simple extension of that method , based on separation of tracer s density . this extension yields a qualitative argument that discriminates between prograde and retrograde inner bars . however , the estimate of the value of inner bar s pattern speed requires further assumptions . when this extension of the tremaine - weinberg method is applied to the recent observation of the doubly barred galaxy ngc 2950 , it indicates that the inner bar there is counter - rotating , possibly with the pattern speed of @xmath0 km s@xmath1 arcsec@xmath1 . the occurrence of counter - rotating inner bars can constrain theories of galaxy formation . galaxies : individual ( ngc 2950 ) galaxies : kinematics and dynamics galaxies : structure
| 164
|
1204.2471
|
the numerical convergence of smoothed particle hydrodynamics ( sph ) can be severely restricted by random force errors induced by particle disorder , especially in shear flows , which are ubiquitous in astrophysics . the increase in the number @xmath0 of neighbours when switching to more extended smoothing kernels _ at fixed resolution _ ( using an appropriate definition for the sph resolution scale ) is insufficient to combat these errors . consequently , trading resolution for better convergence is necessary , but for traditional smoothing kernels this option is limited by the pairing ( or clumping ) instability . therefore , we investigate the suitability of the wendland functions as smoothing kernels and compare them with the traditional b - splines . linear stability analysis in three dimensions and test simulations demonstrate that the wendland kernels avoid the pairing instability for _ all _ @xmath0 , despite having vanishing derivative at the origin ( disproving traditional ideas about the origin of this instability ; instead , we uncover a relation with the kernel fourier transform and give an explanation in terms of the sph density estimator ) . the wendland kernels are computationally more convenient than the higher - order b - splines , allowing large @xmath0 and hence better numerical convergence ( note that computational costs rise sub - linear with @xmath0 ) . our analysis also shows that at low @xmath0 the quartic spline kernel with @xmath1 obtains much better convergence then the standard cubic spline . [ firstpage ] hydrodynamics methods : numerical methods : @xmath2-body simulations
| 261
|
1301.6244
|
we report a detailed examination of the fine structure inside flare ribbons and the temporal evolution of this fine structure during the x2.5 solar flare that occurred on 2004 november 10 . we examine elementary bursts of the @xmath0 ( @xmath11550 ) emission lines seen as local transient brightenings inside the flare ribbons in the ultraviolet ( 1600 ) images taken with transition region and coronal explorer , and we call them @xmath0 kernels . this flare was also observed in h@xmath2 with the sartorius 18 cm refractor telescope at kwasan observatory , kyoto university , in hard x - rays ( hxr ) with reuven ramaty high energy solar spectroscopic imager . many @xmath0 kernels , whose sizes were comparable to or less than 2 , were found to brighten successively during the evolution of the flare ribbon . the majority of them were well correlated with the h@xmath2 kernels in both space and time , while some of them were associated with the hxr emission . these kernels were thought to be caused by the precipitation of nonthermal particles at the foot points of the reconnecting flare loops . the time profiles of the @xmath0 kernels showed intermittent bursts , whose peak intensity , duration and time interval were well described by power - law distribution functions . this result is interpreted as an avalanching system of `` self - organized criticality '' of a single event or by fractal current sheets in the impulsive reconnection region .
| 250
|
0902.0219
|
we study the quantum phase transition between abelian and non - abelian phases in an extended kitaev spin model on the honeycomb lattice , where the periodic boundary condition is applied by placing the lattice on a torus . our analytical results show that this spin model exhibits a continuous quantum phase transition . also , we reveal the relationship between bipartite entanglement and the ground - state energy . our approach directly shows that both the entanglement and the ground - state energy can be used to characterize the topological quantum phase transition in the extended kitaev spin model .
| 101
|
0704.1804
|
dilute fermi systems with large @xmath0-wave scattering length @xmath1 exhibit universal properties if the interparticle spacing @xmath2 greatly exceeds the range of the underlying two - body interaction potential . in this regime , @xmath2 is the only relevant length scale and observables such as the energy per particle depend only on @xmath2 ( or , equivalently , the energy @xmath3 of the free fermi gas ) . this paper investigates bose and fermi systems with non - vanishing angular momentum @xmath4 using the lowest order constrained variational method . we focus on the regime where the generalized scattering length becomes large and determine the relevant length scales . for bose gases with large generalized scattering lengths , we obtain simple expressions for the energy per particle in terms of a @xmath4-dependent length scale @xmath5 , which depends on the range of the underlying two - body potential and the average interparticle spacing . we discuss possible implications for dilute two - component fermi systems with finite @xmath4 . furthermore , we determine the equation of state of liquid and gaseous bosonic helium .
| 184
|
1202.0648
|
scattering of two baryons in the large-@xmath0 gross - neveu model via the time - dependent dirac - hartree - fock approach has recently been solved in closed analytical form . here , we generalize this result to scattering processes involving any number and complexity of the scatterers . the result is extrapolated from the solution of few baryon problems , found via a joint ansatz for the scalar mean field and the dirac spinors , and presented in analytical form . it has been verified numerically for up to 8-baryon problems so far , but a full mathematical proof is still missing . examples shown include the analogue of proton - nucleus and nucleus - nucleus scattering in this toy model . all the parameters of the general result can be fixed by one- and two - baryon input only . we take this finding as evidence for factorized scattering , but on the level of composite multi - fermion states rather than elementary fermions .
| 167
|
1402.7236
|
the sign change of the slope of the directed flow of baryons has been predicted as a signal for a first order phase transition within fluid dynamical calculations . recently , the directed flow of identified particles has been measured by the star collaboration in the beam energy scan ( bes ) program . in this article , we examine the collision energy dependence of directed flow @xmath0 in fluid dynamical model descriptions of heavy ion collisions for @xmath1 gev . the first step is to reproduce the existing predictions within pure fluid dynamical calculations . as a second step we investigate the influence of the order of the phase transition on the anisotropic flow within a state - of - the - art hybrid approach that describes other global observables reasonably well . we find that , in the hybrid approach , there seems to be no sensitivity of the directed flow on the equation of state and in particular on the existence of a first order phase transition . in addition , we explore more subtle sensitivities like e.g. the cooper - frye transition criterion and discuss how momentum conservation and the definition of the event plane affects the results . at this point , none of our calculations matches qualitatively the behavior of the star data , the values of the slopes are always larger than in the data .
| 233
|
1109.2600
|
we present a phenomenological theory of the interplay between nematic order and superconductivity in the vicinity of a vortex induced by an applied magnetic field . nematic order can be strongly enhanced in the vortex core . as a result , the vortex cores become elliptical in shape . for the case where there is weak bulk nematic order at zero magnetic field , the field - induced eccentricity of the vortex core has a slow power - law decay away from the core . conversely , if the nematic order is field - induced , then the eccentricity is confined to the vortex core . we discuss the relevance of our results to recent scanning tunneling microscopy experiments on fese ( song _ et al . _ , science * 332 * , 1410 ( 2011 ) ) .
| 140
|
hep-ph0308070
|
within the borel qcd sum rule approach at finite baryon density we study the role of the four - quark condensates for the modifications of the vector mesons @xmath0 , @xmath1 and @xmath2 in nuclear matter . we find that in - medium modifications of the @xmath0 and @xmath1 mesons are essentially dominated by the dependence of the 4-quark condensate on the nucleon density . in particular , the numerical value of a parameter ( @xmath3 ) , which describes the strength of the density dependence of the 4-quark condensate beyond the mean - field approximation , governs the decrease of the @xmath0 mass as a function of the density . for the @xmath1 meson the sign of the in - medium mass shift is changed by variations of @xmath3 . to study consistently the in - medium broadening of the light vector mesons we employ @xmath4 and @xmath5 scattering amplitudes derived recently from a covariant unitary coupled channel approach adjusted to pion- and photo - induced reactions . in contrast to the @xmath0 and @xmath1 mesons , the in - medium mass of the @xmath2 meson is directly related to the chiral ( strange ) quark condensate . measurements of the vector meson spectral change in heavy - ion collisions with hades can shed light on the yet unknown density dependence of the 4-quark condensate .
| 227
|
astro-ph0204322
|
we use galaxies detected in a deep ultraviolet xmm - newton optical monitor image and a model that predicts uv galaxy counts based on local counts and evolution parameters to constrain galaxy evolution to z=1.2 . the 17 square 2000 ( uvw2 filter ) image was taken as part of the xmm - om team s guaranteed time program . we detect sources in this image to a flux limit of 2.7 @xmath0 10@xmath1 ergs @xmath2 s@xmath3 @xmath3 ( ab magnitude = 22 ) . since some of the sources may be stars , we perform a number of checks , including shape , color and implied distance to remove stars from the detected counts . we find galaxy number counts as a function of magnitude roughly in agreement @xcite , but again find these counts are in excess of evolution models . the excess counts at faint magnitudes may provide evidence for either a new population of galaxies emerging around z=0.7 or more dramatic evolution than some earlier predictions . the integrated light from the detected galaxies totals 3236 ph @xmath2 s@xmath3 @xmath3 sr@xmath3 , placing a firm lower limit on the integrated uv light from galaxies .
| 199
|
0904.1245
|
the main purpose of this article is to extend some of the ideas from schubert calculus to the more general setting of hamiltonian torus actions on compact symplectic manifolds with isolated fixed points . given a generic component @xmath0 of the moment map , which is a morse function , we define a canonical class @xmath1 in the equivariant cohomology of the manifold @xmath2 for each fixed point @xmath3 . when they exist , canonical classes form a natural basis of the equivariant cohomology of @xmath2 ; in particular , when @xmath2 is a flag variety , these classes are the equivariant schubert classes . we show that the restriction of a canonical class @xmath1 to a fixed point @xmath4 can be calculated by a rational function which depends only on the value of the moment map , and the restriction of other canonical classes to points of index exactly two higher . therefore , the structure constants can be calculated by a similar rational function . our restriction formula is _ manifestly positive _ in many cases , including when @xmath2 is a flag manifold . finally , we prove the existence of integral canonical classes in the case that @xmath2 is a gkm manifold and @xmath0 is _ index increasing_. in this case , our restriction formula specializes to an easily computable rational sum which depends only on the gkm graph .
| 234
|
1603.07434
|
we study physics concerning the cosmological constant problem in the framework of effective field theory and suggest that a dominant part of dark energy can originate from gravitational corrections of vacuum energy , under the assumption that the classical gravitational fields do not couple to a large portion of the vacuum energy effectively , in spite of the coupling between graviton and matters at a microscopic level . our speculation is excellent with terascale supersymmetry . dark energy from gravitational corrections .45em 1.5 cm yugo abe@xmath0 , masaatsu horikoshi@xmath1 and yoshiharu kawamura@xmath1 1.5em @xmath2_graduate school of science and engineering , shimane university , _ + matsue 690 - 8504 , japan + @xmath3_department of physics , shinshu university , _ + matsumoto 390 - 8621 , japan 4.5em = 1.0em = 1.0em = 0.5em = 0.5em
| 136
|
astro-ph0608034
|
we consider the hypothesis of a limiting minimal curvature in gravity as a way to construct a class of theories exhibiting late - time cosmic acceleration . guided by the minimal curvature conjecture ( mcc ) we are naturally lead to a set of scalar tensor theories in which the scalar is non - minimally coupled both to gravity and to the matter lagrangian . the model is compared to the lambda cold dark matter concordance model and to the observational data using the gold " sneia sample of riess et . al . ( 2004 ) . an excellent fit to the data is achieved . we present a toy model designed to demonstrate that such a new , possibly fundamental , principle may be responsible for the recent period of cosmological acceleration . observational constraints remain to be imposed on these models . dcpt-06/17 s l h
| 149
|
nucl-th0005076
|
most nuclear physics ranges from insensitive to relatively insensitive to many - nucleon forces . the dominant ingredient in calculations of nuclear properties is the nucleon - nucleon potential . three - nucleon forces nevertheless play an important role in nuclear physics because of the great precision of modern calculational methods for systems of relatively few nucleons . we explore the reasons why many - body forces are weak in nuclei by using a classification scheme for such forces that is based on dimensional power counting , which is used to organize chiral perturbation theory . an assessment will be made of how close we are to a `` standard '' three - nucleon force . recent advances in determining the significance of three - nucleon forces will also be discussed .
| 132
|
0707.2764
|
the measurement of doppler velocity shifts in spectra is a ubiquitous theme in astronomy , usually handled by computing the cross - correlation of the signals , and finding the location of its maximum . this paper addresses the problem of the determination of wavelength or velocity shifts among multiple spectra of the same , or very similar , objects . we implement the classical cross - correlation method and experiment with several simple models to determine the location of the maximum of the cross - correlation function . we propose a new technique , _ self - improvement _ , to refine the derived solutions by requiring that the relative velocity for any given pair of spectra is consistent with all others . by exploiting all available information , spectroscopic surveys involving large numbers of similar objects may improve their precision significantly . as an example , we simulate the analysis of a survey of g - type stars with the sdss instrumentation . applying _ self - improvement _ refines relative radial velocities by more than 50% at low signal - to - noise ratio . the concept is equally applicable to the problem of combining a series of spectroscopic observations of the same object , each with a different doppler velocity or instrument - related offset , into a single spectrum with an enhanced signal - to - noise ratio .
| 234
|
hep-ex9812030
|
recent experimental results on the partonic structure of the photon and on the color singlet exchange in strong interaction processes are reviewed . at the lep @xmath0 and hera @xmath1 colliders , complementary and consistent measurements have been achieved on the quark - gluon structure of quasi - real and virtual photons . at the hera @xmath1 and tevatron @xmath2 colliders , the quark - gluon configuration of the diffractive exchange is consistently found to have a large gluon component . the rate of diffractive interactions observed by the hera and tevatron experiments , however , is largely different and challenges explanation . # 1#2#3#4#1 * # 2 * ( # 3 ) # 4 @xmath3 @xmath4 desy-98 - 209b issn 0418 - 9833 + december 1998 * diffraction and low-@xmath5 physics + including two - photon physics * martin erdmann + universitt karlsruhe , engesserstr . 7 , d-76128 karlsruhe + e - mail : martin.erdmann@desy.de _ invited plenary talk at the xxix international conference on high energy physics , vancouver , b.c . canada ( 1998 ) _
| 180
|
astro-ph9811161
|
we present a new scheme for modeling the broad line region in active galactic nuclei . it involves photoionization calculations applied to a number of variable emission lines at _ all times_. we demonstrate how fitting all lines simultaneously provide strong constraints on several of the more important parameters , such as the density and column density , and the radial distribution of the emission line clouds . when applying the model to the seyfert 1 galaxy ngc 5548 , we are able to reconstruct the light curves of four emission - lines , in time and in absolute flux . we argue that the balmer line light curves , and possibly also the mgii@xmath02798 light curve , do not fit this scheme because of the limitations of present - day photoionization codes . we rule out models where the particle density scales as @xmath1 and favor models where it scales as @xmath2 . we can place lower limits on the column density at a distance of 10 ld , of @xmath3=10)@xmath4 @xmath5 , and limit the particle density to be in the range of 10@xmath6@xmath7@xmath8=10)@xmath710@xmath9 @xmath10 .
| 188
|
0809.1189
|
we define a volume limited sample of over 14,000 early - type galaxies ( etgs ) selected from data release six of the sloan digital sky survey . the density of environment of each galaxy is robustly measured . by comparing narrow band spectral line indices with recent models of simple stellar populations ( ssps ) we investigate trends in the star formation history as a function of galaxy mass ( velocity dispersion ) , density of environment and galactic radius . we find that age , metallicity and @xmath0-enhancement all increase with galaxy mass and that field etgs are younger than their cluster counterparts by @xmath1 . we find negative radial metallicity gradients for all masses and environments , and positive radial age gradients for etgs with velocity dispersion over @xmath2 . our results are qualitatively consistent with a relatively simple picture for etg evolution in which the low - mass halos accreted by a proto - etg contained not only gas but also a stellar population . this fossil population is preferentially found at large radii in massive etgs because the stellar accretions were dissipationless . we estimate that the typical , massive etg should have been assembled at @xmath3 . the process is similar in the cluster and the field but occurred earlier in dense environments . [ firstpage ] galaxies : elliptical and lenticular , cd , galaxies : formation , galaxies : abundances
| 238
|
1611.09872
|
the recently proposed effective potential theory [ phys . rev . lett . 110 , 235001 ( 2013 ) ] allows evaluating transport in coupled plasmas with the well - developed formalisms for systems with binary collisions . to facilitate practical implementation of this concept in fluid models of multi - component plasmas , compact expressions for the transport coefficients in terms the generalized coulomb logarithms are summarized from existing prescriptions . for weakly coupled plasmas , characterized by debye - shielded coulomb interaction potential , expressions become fully analytical . in coupled plasmas the generalized coulomb logarithms need to be evaluated numerically . routines implementing the described formalisms are included as supplemental material .
| 115
|
cond-mat9708021
|
we discuss the effect of disorder on the coherent propagation of the bound state of two attracting particles . it is shown that a result analogous to the anderson theorem for dirty superconductors is also valid for the cooper problem , namely , that the pair wave function is extended beyond the single - particle localization length if the latter is large . a physical justification is given in terms of the thouless block - scaling picture of localization . these arguments are supplemented by numerical simulations . with increasing disorder we find a transition from a regime in which the interaction delocalizes the pair to a regime in which the interaction enhances localization .
| 115
|
1610.03369
|
based on a lie symmetry analysis , we construct a closed form solution to the kinematic part of the ( partial differential ) cosserat equations describing the mechanical behavior of elastic rods . the solution depends on two arbitrary analytical vector functions and is analytical everywhere except a certain domain of the independent variables in which one of the arbitrary vector functions satisfies a simple explicitly given algebraic relation . as our main theoretical result , in addition to the construction of the solution , we proof its generality . based on this observation , a hybrid semi - analytical solver for highly viscous two - way coupled fluid - rod problems is developed which allows for the interactive high - fidelity simulations of flagellated microswimmers as a result of a substantial reduction of the numerical stiffness . rods , differential thomas decomposition , flagellated microswimmers , general analytical solution , kinematic equations , lie symmetry analysis , stokes flow , symbolic computation .
| 164
|
astro-ph0005374
|
we present the results of a 2-d , two fluid ( ions and neutrals ) simulation of the ambipolar filamentation process , in which a magnetized , weakly ionized plasma is stirred by turbulence in the ambipolar frequency range . the higher turbulent velocity of the neutrals in the most ionized regions gives rise to a non - linear force driving them out of these regions , so that the initial ionization inhomogeneities are strongly amplified . this effect , the ambipolar filamentation , causes the ions and the magnetic flux to condense and separate from the neutrals , resulting in a filamentary structure . # 1 # 1 0.5 cm
| 111
|
0812.1386
|
we present two - color modulation transfer spectroscopy as a tool for precision studies of atomic properties of excited states . the bi - colored technique addresses a narrow set of velocity groups of a thermal atomic vapour using a two - step transition to burn a hole " in the velocity distribution . the resulting spectrum presents sub - doppler linewidths , good signal to noise ratio and the trademark sidebands that work as an _ in situ _ ruler for the energy spacing between atomic resonances . the spectra obtained can be used for different applications such as measurements of energy splittings or stabilization of laser frequencies to excited atomic transitions . = 10000
| 116
|
astro-ph0006457
|
high resolution spectra of the active binary capella ( g8 iii + g1 iii ) covering the energy range 0.4 - 8.0 kev ( 1.5 - 30 ) show a large number of emission lines , demonstrating the performance of the hetgs . a preliminary application of plasma diagnostics provides information on coronal temperatures and densities . lines arising from different elements in a range of ionization states indicate that capella has plasma with a broad range of temperatures , from @xmath0 , generally consistent with recent results from observations with the extreme ultraviolet explorer ( euve ) and the advanced satellite for cosmology and astrophysics ( asca ) . the electron density is determined from he - like o vii lines , giving the value @xmath1 at @xmath2 ; he - like lines formed at higher temperatures give only upper limits to the electron density . the density and emission measure from o vii lines together indicate that the coronal loops are significantly smaller than the stellar radius .
| 170
|
physics0510237
|
the time dependence of the survival probability of an opinion in a closed community has been investigated in accordance with social temperature by using the kawasaki - exchange dynamics based on previous study in ref . [ 1 ] . it is shown that the survival probability of opinion decays with stretched exponential law consistent with previous static model . however , the crossover regime in the decay of the survival probability has been observed in this dynamic model unlike previous model . the decay characteristics of both two regimes obey to stretched exponential . * keywords : * ising model ; politics ; random walk ; sociophysics ; sznajd model .
| 112
|
1304.5541
|
as the title suggests , the purpose of this chapter is to review the current status of numerical simulations of black hole accretion disks . this chapter focuses exclusively on _ global _ simulations of the accretion process within a few tens of gravitational radii of the black hole . most of the simulations discussed are performed using general relativistic magnetohydrodynamic ( mhd ) schemes , although some mention is made of newtonian radiation mhd simulations and smoothed particle hydrodynamics . the goal is to convey some of the exciting work that has been going on in the past few years and provide some speculation on future directions . = 1
| 111
|
1001.4250
|
we present a theoretical study of time - dependent quantum transport in a resonant tunnel junction coupled to a nanomechanical oscillator within the non - equilibrium green s function technique . an arbitrary voltage is applied to the tunnel junction and electrons in the leads are considered to be at zero temperature . the transient and the steady state behavior of the system is considered here in order to explore the quantum dynamics of the oscillator as a function of time . the properties of the phonon distribution of the nanomechnical oscillator strongly coupled to the electrons on the dot are investigated using a non - perturbative approach . we consider both the energy transferred from the electrons to the oscillator and the fano factor as a function of time . we discuss the quantum dynamics of the nanomechanical oscillator in terms of pure and mixed states . we have found a significant difference between a quantum and a classical oscillator . in particular , the energy of a classical oscillator will always be dissipated by the electrons whereas the quantum oscillator remains in an excited state . this will provide useful insight for the design of experiments aimed at studying the quantum behavior of an oscillator .
| 208
|
1210.8149
|
the m82 ` cap ' is a gas cloud at a projected radius of 11.6 kpc along the minor axis of this well known superwind source . the cap has been detected in optical line emission and x - ray emission and therefore provides an important probe of the wind energetics . in order to investigate the ionization source of the cap , we observed it with the kyoto3dii fabry - perot instrument mounted on the subaru telescope . deep continuum , h@xmath0 , [ ] @xmath16583/h@xmath0 , and [ ] @xmath26716,6731/h@xmath0 maps were obtained with sub - arcsecond resolution . the superior spatial resolution compared to earlier studies reveals a number of bright h@xmath0 emitting clouds within the cap . the emission line widths ( @xmath3 km s@xmath4 fwhm ) and line ratios in the newly identified knots are most reasonably explained by slow to moderate shocks velocities ( @xmath5 = 4080 km s@xmath4 ) driven by a fast wind into dense clouds . the momentum input from the m82 nuclear starburst region is enough to produce the observed shock . consequently , earlier claims of photoionization by the central starburst are ruled out because they can not explain the observed fluxes of the densest knots unless the uv escape fraction is very high ( @xmath6 60% ) , i.e. , an order of magnitude higher than observed in dwarf galaxies to date . using these results , we discuss the evolutionary history of the m82 superwind . future uv / x - ray surveys are expected to confirm that the temperature of the gas is consistent with our moderate shock model .
| 274
|
0901.0617
|
we exploit the recent observations of extremely metal - poor ( emp ) stars in the galactic halo and investigate the constraints on the initial mass function ( imf ) of the stellar population that left these low - mass survivors of @xmath0}\lesssim -2.5 $ ] and the chemical evolution that took part in . a high - mass nature of imf with the typical mass @xmath1 and the overwhelming contribution of low - mass members of binaries to the emp survivors are derived from the statistics of carbon - enriched emp stars with and without the enhancement of s - process elements ( komiya et al . 2007 , ) . that the same constraints are placed on the imf from the surface density of emp stars estimated from the surveys and the chemical evolution consistent with the metal yields of theoretical supernova models . apply the derived high - mass imf with the binary contribution metallicity distribution function ( mdf ) of emp stars not only for the shape but also for the number of emp stars . in particular , the scarcity of stars below @xmath0}\simeq -4 $ ] is naturally explained in terms of the hierarchical structure formation , and there is no indication of significant changes in the imf for the emp population . the present study indicates that 3 hmp / ump stars of @xmath0 } < -4 $ ] are the primordial stars that were born as the low - mass members of binaries before the host clouds were polluted by their own supernovae .
| 262
|
1005.1705
|
integration of the form @xmath0 , where @xmath1 is either @xmath2 or @xmath3 , is widely encountered in many engineering and scientific applications , such as those involving fourier or laplace transforms . often such integrals are approximated by a numerical integration over a finite domain @xmath4 , leaving a truncation error equal to the tail integration @xmath5 in addition to the discretization error . this paper describes a very simple , perhaps the simplest , end - point correction to approximate the tail integration , which significantly reduces the truncation error and thus increases the overall accuracy of the numerical integration , with virtually no extra computational effort . higher order correction terms and error estimates for the end - point correction formula are also derived . the effectiveness of this one - point correction formula is demonstrated through several examples . * keywords : * numerical integration , fourier transform , laplace transform , truncation error .
| 159
|
cond-mat0006244
|
we present a detailed study of the transport and energetics of a brownian particle moving in a periodic potential in the presence of an adiabatic external periodic drive . the particle is considered to move in a medium with periodic space dependent friction with the same periodicity as that of the potential but with a phase lag . we obtain several results , most of them arising due to the medium being inhomogeneous and are sensitive to the phase lag . when the potential is symmetric we show that efficiency of energy transduction can be maximised as a function of noise strength or temperature . however , in the case of asymmtertic potential the temperature may or may not facilitate the energy conversion but current reversals can be obtained as a function of temperature and the amplitude of the periodic drive . the reentrant behaviour of current can also be seen as a function of phase lag . + pacs number(s ) : 05.40+j , 05.60+w , 82.20mj = 0.3 in = 0.6 in
| 174
|
cond-mat0106220
|
a zero temperature dynamics of ising spin glasses and ferromagnets on random graphs of finite connectivity is considered , like granular media these systems have an extensive entropy of metastable states . we consider the problem of what energy a randomly prepared spin system falls to before becoming stuck in a metastable state . we then introduce a tapping mechanism , analogous to that of real experiments on granular media , this tapping , corresponding to flipping simultaneously any spin with probability @xmath0 , leads to stationary regime with a steady state energy @xmath1 . we explicitly solve this problem for the one dimensional ferromagnet and @xmath2 spin glass and carry out extensive numerical simulations for spin systems of higher connectivity . the link with the density of metastable states at fixed energy and the idea of edwards that one may construct a thermodynamics with a flat measure over metastable states is discussed . in addition our simulations on the ferromagnetic systems reveal a novel first order transition , whereas the usual thermodynamic transition on these graphs is second order . 0.5 cm pacs numbers : 05.20 , 75.10 nr , 81.05 rm . 2
| 195
|
1212.4426
|
the attenuation of atmospheric cherenkov photons is dominated by two processes : rayleigh scattering from the molecular component and mie scattering from the aerosol component . aerosols are expected to contribute up to 30 wm@xmath0 to the emission profile of the atmosphere , equivalent to a difference of @xmath1c to the clear sky brightness temperature under normal conditions . here we investigate the aerosol contribution of the measured sky brightness temperature at the h.e.s.s . site ; compare it to effective changes in the telescope trigger rates ; and discuss how it can be used to provide an assessment of sky clarity that is unambiguously free of telescope systematics . address = department of physics , university of durham , durham , dh1 3le . u.k . address = lupm , un . montpellier ii cc-072 , place eugenie bataillon , 34095 montpellier , france .
| 146
|
1212.1336
|
we report measurements of the exclusive electroproduction of @xmath0 and @xmath1 final states from an unpolarized proton target using the clas detector at the thomas jefferson national accelerator facility . the separated structure functions @xmath2 , @xmath3 , @xmath4 , and @xmath5 were extracted from the @xmath6-dependent differential cross sections acquired with a longitudinally polarized 5.499 gev electron beam . the data span a broad range of momentum transfers @xmath7 from 1.4 to 3.9 gev@xmath8 , invariant energy @xmath9 from threshold to 2.6 gev , and nearly the full center - of - mass angular range of the kaon . the separated structure functions provide an unprecedented data sample , which in conjunction with other meson photo- and electroproduction data , will help to constrain the higher - level analyses being performed to search for missing baryon resonances .
| 139
|
nucl-th0403041
|
to elucidate the mechanism by which chaos is generated in the shell model , we compare three random matrix ensembles : the gaussian orthogonal ensemble , french s two body embedded ensemble , and the two body random ensemble ( tbre ) of the shell model . of these , the last two take account of the two body nature of the residual interaction , and only the last , of the existence of conserved quantum numbers like spin , isospin , and parity . while the number of independent random variables decreases drastically as we follow this sequence , the complexity of the ( fixed ) matrices which support the random variables , increases even more . in that sense we can say that in the tbre , chaos is largely due to the existence of ( an incomplete set of ) symmetries . shell model , symmetry , complexity 21.10.-k , 05.45.mt , 24.60.-k
| 156
|
0905.4423
|
we apply a recently proposed density functional for mixtures of parallel hard cylinders , based on rosenfeld s fundamental measure theory , to study the effect of length - polydispersity on the relative stability between the smectic and columnar liquid crystal phases . to this purpose we derive from this functional an expression for the direct correlation function and use it to perform a bifurcation analysis . we compare the results with those obtained with a second and a third virial approximation of this function . all three approximations lead to the same conclusion : there is a terminal polydispersity beyond which the smectic phase is less stable than the columnar phase . this result is in agreement with previous monte carlo simulations conducted on a freely rotating length - polydisperse hard spherocylinder fluid , although the theories always overestimate the terminal polydispersity because the nematic - columnar phase transition is first order and exhibits a wide coexistence gap . both , the fundamental - measure functional and the third virial approximation , predict a metastable nematic - nematic demixing . conversely , according to second virial approximation this demixing might be stable at high values of the polydispersity , something that is observed neither in simulations nor in experiments . the results of the fundamental - measure functional are quantitatively superior to those obtained from the other two approximations . thus this functional provides a promising route to map out the full phase diagram of this system .
| 249
|
astro-ph9702016
|
we report results of rxte observations of psr b1951 + 32 using the pca instrument for 19k seconds during 1996 march 24th . we applied the contemporaneous radio ephemeris and various statistical tests to search for evidence of pulsation . these analyses yield intriguing yet inconclusive evidence for the presence of the pulsation in the time series : confidence level for the presence of pulsation is 94.5% in the 2.0 - 4.8 kev band and 97.6% in the 4.8 - 6.3 kev band based on the @xmath0-test . under the premise of non - detection of pulsation , we derive estimated 2-@xmath1 upper limits for the pulsed flux to be @xmath2 in the 2.0 - 4.8 kev band , @xmath3 in the 4.8 - 8.5 kev band , and @xmath4 in the 8.5 - 13.0 kev band . these upper limits are consistent with the trend of spectral turn - over from high - energy gamma - ray emission as suggested by the osse upper limit . such turn - over strongly suggests the outer magnetosphere as the emission site for pulsed gamma - rays . these rxte upper limits for x - ray pulsation are , on the other hand , not consistent with the extrapolation of reported power - law spectra from the point source observed by rosat in the 0.1 - 2.4 kev band , assuming a constant pulse fraction : the pulsed soft x - ray emission detected by rosat must follow a much softer spectrum than that of the overall point source .
| 258
|
0709.3035
|
a detailed study is presented of the search for higgs bosons in the b - decay channel in the central exclusive production process at the lhc . we present results for proton tagging detectors at both 220 m and 420 m around atlas or cms . we consider two benchmark scenarios ; a standard model ( sm ) higgs boson and the @xmath0 scenario of the minimal supersymmetric standard model ( mssm ) . detector acceptance , smearing and event trigger strategies are considered . we find that the sm higgs will be challenging to observe in the b - jet channel without improvements to the currently proposed experimental configuration , but a neutral scalar mssm higgs boson could be observable in the b - jet channel with a significance of @xmath1 or greater within three years of data taking at all luminosities between @xmath2 @xmath3 s@xmath4 and @xmath5 @xmath3 s@xmath4 , and at @xmath6 or greater after three years in certain scenarios .
| 164
|
1304.2076
|
a bound - state field theory approach to muonic hydrogen is set up using a variant of the furry representation in which the lowest - order hamiltonian describes a muon in the presence of a point coulomb field , but the origin of the binding field is taken to be three charged quarks in the proton which are modeled as dirac particles that move freely within a spherical well . bound - state field theory techniques are used to evaluate one- and two - photon effects . particular attention is paid to two - photon exchange diagrams , which include the effect of proton polarizability . in addition the modification of the electromagnetic self energy of the proton by the electric field of the muon is examined . finally , the model is used to carry out a calculation of the static electric polarizability of the proton . # 1#2 # 1#2 # 1
| 154
|
astro-ph9909505
|
2 is a second generation microlensing experiment operating since mid-1996 at the european southern observatory ( eso ) at la silla ( chile ) . we present the two year analysis from our microlensing search towards the small magellanic cloud ( ) , and report on the intensive observation of the caustic crossing event -98 - 1 and the limit derived on the location of the lens . we also give preliminary results from our search towards the large magellanic cloud ( ) ; 25 square degrees are being analyzed and two candidates have been found . this allows us to set another limit on the halo mass fraction comprised of compact objects .
| 114
|
1303.3678
|
we discuss hall effect and power dissipation in chiral @xmath0-wave superconductors near kosterlitz - thouless transition in the absence of applied magnetic field . in bound pair dynamics picture , nonzero hall conductivity emerges when vortex - antivortex bound pair polarization has a component transverse to the direction of external perturbation . such effect arises from the broken time reversal symmetry nature of a chiral @xmath0-wave superconducting state and does not require an applied magnetic field . a frequency - dependent matrix dielectric function @xmath1 is derived to describe the screening effect due to the pair polarization . quantities related to the hall conductivity and power dissipation , denoted as @xmath2 and @xmath3 , are investigated in frequency and temperature domain . the imaginary part of the former can show peak structure and sign reversal as a function of frequency close to transition temperature , as well as in the temperature domain at various fixed frequencies . the latter shows peak structure near transition temperature . these features are attributed to pair - size - dependent longitudinal and transverse response function of bound pairs . consequences due to free vortex dynamics and the resulting total conductivity tensor @xmath4 are also discussed .
| 202
|
1301.6983
|
motivated by questions about square - free monomial ideals in polynomial rings , in 2010 francisco et al . conjectured that for every positive integer @xmath0 and every @xmath0-critical ( i.e. , critically @xmath0-chromatic ) graph , there is a set of vertices whose replication produces a @xmath1-critical graph . ( the replication of a set @xmath2 of vertices of a graph is the operation that adds a copy of each vertex @xmath3 in @xmath2 , one at a time , and connects it to @xmath3 and all its neighbours . ) we disprove the conjecture by providing an infinite family of counterexamples . furthermore , the smallest member of the family answers a question of herzog and hibi concerning the depth functions of square - free monomial ideals in polynomial rings , and a related question on the persistence property of such ideals .
| 145
|
nucl-th9609037
|
the universal curve @xmath0 of nuclear photoabsorption is investigated within a fermi gas model of nuclear matter . an energy range from pion threshold up to 400 mev is considered . the interactions between nucleon , pion , @xmath1-isobar and photon are considered in the non - relativistic approximation with corrections of the order @xmath2 taken into account with respect to proton mass . analytical expressions are obtained , in which the influence of nuclear correlations , two - nucleon contributions and relativistic corrections is studied explicitely . an extension of the model calculation to nucleon knock - out reactions is discussed . contribution of real and virtual pions to nuclear photoabsorption at intermediate energies + m .- th.htt@xmath3 , a.i.milstein@xmath4 and m.schumacher@xmath3 + ( a ) ii . institut der universitt gttingen , gttingen , germany \(b ) budker institute of nuclear physics , 630090 novosibirsk , russia 0em 1.5ex plus 0.5ex minus 0.5ex _ pacs code : _ 25.20.-x _ keywords : _ photoabsorption , mesonic exchange currents , nuclear correlation functions
| 174
|
1206.0314
|
dwarf galaxies are good candidates to investigate the nature of dark matter , because their kinematics are dominated by this component down to small galactocentric radii . we present here the results of detailed kinematic analysis and mass modelling of the orion dwarf galaxy , for which we derive a high quality and high resolution rotation curve that contains negligible non - circular motions and we correct it for the asymmetric drift . moreover , we leverage the proximity ( d @xmath0 5.4 kpc ) and convenient inclination ( 47@xmath1 ) to produce reliable mass models of this system . we find that the universal rotation curve mass model ( freeman disk @xmath2 burkert halo @xmath2 gas disk ) fits the observational data accurately . in contrast , the nfw halo + freeman disk @xmath2 gas disk mass model is unable to reproduce the observed rotation curve , a common outcome in dwarf galaxies . finally , we attempt to fit the data with a modified newtonian dynamics ( mond ) prescription . with the present data and with the present assumptions on distance , stellar mass , constant inclination and reliability of the gaseous mass , the mond `` amplification '' of the baryonic component appears to be too small to mimic the required `` dark component '' . the orion dwarf reveals a cored dm density distribution and a possible tension between observations and the canonical mond formalism . [ firstpage ] dark matter ; galaxy : orion dwarf ; mass profiles
| 254
|
0910.2984
|
results are reported from a joint analysis of phase i and phase ii data from the sudbury neutrino observatory . the effective electron kinetic energy threshold used is @xmath0 mev , the lowest analysis threshold yet achieved with water cherenkov detector data . in units of @xmath1 @xmath2 s@xmath3 , the total flux of active - flavor neutrinos from @xmath4b decay in the sun measured using the neutral current ( nc ) reaction of neutrinos on deuterons , with no constraint on the @xmath4b neutrino energy spectrum , is found to be @xmath5 these uncertainties are more than a factor of two smaller than previously published results . also presented are the spectra of recoil electrons from the charged current reaction of neutrinos on deuterons and the elastic scattering of electrons . a fit to the sno data in which the free parameters directly describe the total @xmath4b neutrino flux and the energy - dependent @xmath6 survival probability provides a measure of the total @xmath4b neutrino flux @xmath7 . combining these new results with results of all other solar experiments and the kamland reactor experiment yields best - fit values of the mixing parameters of @xmath8 degrees and @xmath9 ev@xmath10 . the global value of @xmath11 is extracted to a precision of @xmath12% . in a three - flavor analysis the best fit value of @xmath13 is @xmath14 . this implies an upper bound of @xmath15 ( 95% c.l . ) .
| 242
|
1001.3152
|
in this paper we present the results of @xmath0-body simulations with a scalar field coupled differently to cold dark matter ( cdm ) and baryons . the scalar field potential and coupling function are chosen such that the scalar field acquires a heavy mass in regions with high cdm density and thus behaves like a chameleon . we focus on how the existence of the scalar field affects the formation of nonlinear large - scale structure , and how the different couplings of the scalar field to baryons and cdm particles lead to different distributions and evolutions for these two matter species , both on large scales and inside virialized halos . as expected , the baryon - cdm segregation increases in regions where the fifth force is strong , and little segregation in dense regions . we also introduce an approximation method to identify the virialized halos in coupled scalar field models which takes into account the scalar field coupling and which is easy to implement numerically . it is find that the chameleon nature of the scalar field makes the internal density profiles of halos dependent on the environment in a very nontrivial way .
| 197
|
1611.05854
|
global , population - wide oscillations in models of cyclic dominance may result in the collapse of biodiversity due to the accidental extinction of one species in the loop . previous research has shown that such oscillations can emerge if the interaction network has small - world properties , and more generally , because of long - range interactions among individuals or because of mobility . but although these features are all common in nature , global oscillations are rarely observed in actual biological systems . this begets the question what is the missing ingredient that would prevent local oscillations to synchronize across the population to form global oscillations . here we show that , although heterogeneous species - specific invasion rates fail to have a noticeable impact on species coexistence , randomness in site - specific invasion rates successfully hinders the emergence of global oscillations and thus preserves biodiversity . our model takes into account that the environment is often not uniform but rather spatially heterogeneous , which may influence the success of microscopic dynamics locally . this prevents the synchronization of locally emerging oscillations , and ultimately results in a phenomenon where one type of randomness is used to mitigate the adverse effects of other types of randomness in the system .
| 214
|
0809.3330
|
this paper studies infinite graphs produced from a natural unfolding operation applied to finite graphs . graphs produced via such operations are of finite degree and automatic over the unary alphabet ( that is , they can be described by finite automata over unary alphabet ) . we investigate algorithmic properties of such unfolded graphs given their finite presentations . in particular , we ask whether a given node belongs to an infinite component , whether two given nodes in the graph are reachable from one another , and whether the graph is connected . we give polynomial - time algorithms for each of these questions . for a fixed input graph , the algorithm for the first question is in constant time and the second question is decided using an automaton that recognizes reachability relation in a uniform way . hence , we improve on previous work , in which non - elementary or non - uniform algorithms were found .
| 162
|
0805.1796
|
it is shown that the molecular ion @xmath0 does not exist in a form of the equilateral triangle . to this end , a compact variational method is presented which is based on a linear superposition of six specially tailored trial functions containing non - linear parameters . careful optimization of a total of fifteen parameters gives consistently lower variational results for the electronic energy than can be obtained with standard methods of quantum chemistry even with huge basis sets as large as mcc - pv7z . _ dedicated to professor rudolf zahradnik on the occasion of his 80th birthday _
| 101
|
1307.7838
|
we study bidding and pricing competition between two spiteful mobile network operators ( mnos ) with considering their existing spectrum holdings . given asymmetric - valued spectrum blocks are auctioned off to them via a first - price sealed - bid auction , we investigate the interactions between two spiteful mnos and users as a three - stage dynamic game and characterize the dynamic game s equilibria . we show an asymmetric pricing structure and different market share between two spiteful mnos . perhaps counter - intuitively , our results show that the mno who acquires the less - valued spectrum block always lowers his service price despite providing double - speed lte service to users . we also show that the mno who acquires the high - valued spectrum block , despite charing a higher price , still achieves more market share than the other mno . we further show that the competition between two mnos leads to some loss of their revenues . by investigating a cross - over point at which the mnos profits are switched , it serves as the benchmark of practical auction designs .
| 190
|
cond-mat0502213
|
we study channelization and slope destabilization driven by subsurface ( groundwater ) flow in a laboratory experiment . the pressure of the water entering the sandpile from below as well as the slope of the sandpile are varied . we present quantitative understanding of the three modes of sediment mobilization in this experiment : surface erosion , fluidization , and slumping . the onset of erosion is controlled not only by shear stresses caused by surfical flows , but also hydrodynamic stresses deriving from subsurface flows . these additional forces require modification of the critical shields criterion . whereas surface flows alone can mobilize surface grains only when the water flux exceeds a threshold , subsurface flows cause this threshold to vanish at slopes steeper than a critical angle substantially smaller than the maximum angle of stability . slopes above this critical angle are unstable to channelization by any amount of fluid reaching the surface .
| 156
|
hep-ph9802301
|
the _ rhic _ facility at _ bnl _ will be operating soon , part of the year , as a polarized proton - proton collider . this will allow the undertaking of a vast spin physics programme , mainly by the two large detectors _ phenix _ and _ star_. we review some theoretical aspects of this research programme which will allow , firstly to improve our present knowledge on polarized quark , gluon and sea distributions in a nucleon , secondly to perform novel _ qcd _ spin tests and finally , perhaps , to uncover some new physics .
| 102
|
0812.4794
|
propagation of extremely short electromagnetic pulses in a homogeneous doubly - resonant medium is considered in the framework of the total maxwell - duffing - lorentz model , where the duffing oscillators ( anharmonic oscillators with cubic nonlinearities ) represent the dielectric response of the medium , and the lorentz harmonic oscillators represent the magnetic response . the wave propagation is governed by the one - dimensional maxwell equations . it is shown that the model possesses a one - parameter family of traveling - wave solutions with the structure of single or multiple humps . solutions are parametrized by the velocity of propagation . the spectrum of possible velocities is shown to be continuous on a small interval at the lower end of the spectrum ; elsewhere the velocities form a discrete set . a correlation between the number of humps and the velocity is established . the traveling - wave solutions are found to be stable with respect to weak perturbations . numerical simulations demonstrate that the traveling - wave pulses collide in a nearly elastic fashion .
| 180
|
cond-mat0512145
|
we propose a general geometric growth model for pseudofractal scale - free web , which is controlled by two tunable parameters . we derive exactly the main characteristics of the networks : degree distribution , second moment of degree distribution , degree correlations , distribution of clustering coefficient , as well as the diameter , which are partially determined by the parameters . analytical results show that the resulting networks are disassortative and follow power - law degree distributions , with a more general degree exponent tuned from 2 to @xmath0 ; the clustering coefficient of each individual node is inversely proportional to its degree and the average clustering coefficient of all nodes approaches to a large nonzero value in the infinite network order ; the diameter grows logarithmically with the number of network nodes . all these reveal that the networks described by our model have small - world effect and scale - free topology . complex networks , scale - free networks , disordered systems , networks
| 169
|
astro-ph0411037
|
we investigate the relationship between the colors , luminosities , and environments of galaxies in the sloan digital sky survey spectroscopic sample , using environmental measurements on scales ranging from @xmath0 to @xmath1 @xmath2 mpc . we find : ( 1 ) that the relationship between color and environment persists even to the lowest luminosities we probe ( @xmath3 ) ; ( 2 ) at luminosities and colors for which the galaxy correlation function has a large amplitude , it also has a steep slope ; and ( 3 ) in regions of a given overdensity on small scales ( 1 @xmath2 mpc ) , the overdensity on large scales ( 6 @xmath2 mpc ) does not appear to relate to the recent star formation history of the galaxies . of these results , the last has the most immediate application to galaxy formation theory . in particular , it lends support to the notion that a galaxy s properties are related only to the mass of its host dark matter halo , and not to the larger scale environment .
| 181
|
1502.01311
|
global magnetic field extrapolations are now revealing the huge complexity of the sun s corona , and in particular the structure of the boundary between open and closed magnetic flux . moreover , recent developments indicate that magnetic reconnection in the corona likely occurs in highly fragmented current layers , and that this typically leads to a dramatic increase in the topological complexity beyond that of the equilibrium field . in this paper we use static models to investigate the consequences of reconnection at the open - closed flux boundary ( interchange reconnection " ) in a fragmented current layer . we demonstrate that it leads to efficient mixing of magnetic flux ( and therefore plasma ) from open and closed field regions . this corresponds to an increase in the length and complexity of the open - closed boundary . thus , whenever reconnection occurs at a null point or separator of this open - closed boundary , the associated separatrix arc of the so - called _ s - web _ in the high corona becomes not a single line but a band of finite thickness within which the open - closed boundary is highly structured . this has significant implications for the acceleration of the slow solar wind , for which the interaction of open and closed field is thought to be important , and may also explain the coronal origins of certain solar energetic particles . the topological structures examined contain magnetic null points , separatrices and separators , and include a model for a pseudo - streamer . the potential for understanding both the large scale morphology and fine structure observed in flare ribbons associated with coronal nulls is also discussed .
| 287
|
cond-mat9802049
|
a numerical method is described for evaluating transverse spin correlations in the random phase approximation . quantum spin - fluctuation corrections to sublattice magnetization are evaluated for the antiferromagnetic ground state of the half - filled hubbard model in two and three dimensions in the whole @xmath0 range . extension to the case of defects in the af is also discussed for spin vacancies and low@xmath1 impurities . in the @xmath2 limit , the vacancy - induced enhancement in the spin fluctuation correction is obtained for the spin - vacancy problem in two dimensions , for vacancy concentration up to the percolation threshold . for low-@xmath3 impurities , the overall spin fluctuation correction is found to be strongly suppressed , although surprisingly spin fluctuations are locally enhanced at the low@xmath1 sites . 2
| 133
|
hep-ph0105236
|
coupled , multi - field models of inflation can provide several attractive features unavailable in the case of a single inflaton field . these models have a rich dynamical structure resulting from the interaction of the fields and their associated fluctuations . we present a formalism to study the nonequilibrium dynamics of coupled scalar fields . this formalism solves the problem of renormalizing interacting models in a transparent way using dimensional regularization . the evolution is generated by a renormalized effective lagrangian which incorporates the dynamics of the mean fields and their associated fluctuations at one - loop order . we apply our method to two problems of physical interest : ( i ) a simple two - field model which exemplifies applications to reheating in inflation , and ( ii ) a supersymmetric hybrid inflation model . this second case is interesting because inflation terminates via a smooth phase transition which gives rise to a spinodal instability in one of the fields . we study the evolution of the zero mode of the fields and the energy density transfer to the fluctuations from the mean fields . we conclude that back reaction effects can be significant over a wide parameter range . in particular for the supersymmetric hybrid model we find that particle production can be suppressed due to these effects .
| 223
|
1203.1169
|
high - brightness electron beams with low energy spread at existing and future x - ray free - electron lasers are affected by various collective beam self - interactions and microbunching instabilities . the corresponding coherent optical radiation effects , e.g. , coherent optical transition radiation , impede electron beam profile imaging and become a serious issue for all kinds of electron beam diagnostics using imaging screens . furthermore , coherent optical radiation effects can also be related to intrinsically ultrashort electron bunches or the existence of ultrashort spikes inside the electron bunches . in this paper , we discuss methods to suppress coherent optical radiation effects both by electron beam profile imaging in dispersive beamlines and by using scintillation imaging screens in combination with separation techniques . the suppression of coherent optical emission in dispersive beamlines is shown by analytical calculations , numerical simulations , and measurements . transverse and longitudinal electron beam profile measurements in the presence of coherent optical radiation effects in non - dispersive beamlines are demonstrated by applying a temporal separation technique .
| 178
|
astro-ph0404085
|
we measure the angular power spectrum @xmath0 of radio galaxies in the nrao vla sky survey ( nvss ) using two independent methods : direct spherical harmonic analysis and maximum likelihood estimation . the results are consistent and can be understood using models for the spatial matter power spectrum and for the redshift distribution of radio galaxies at mjy flux - density levels . a good fit to the angular power spectrum can only be achieved if radio galaxies possess high bias with respect to mass fluctuations ; by marginalizing over the other parameters of the model we derive a @xmath1 confidence interval @xmath2 , where @xmath3 is the linear bias factor for radio galaxies and @xmath4 describes the normalization of the matter power spectrum . our models indicate that the majority of the signal in the nvss @xmath0 spectrum is generated at low redshifts @xmath5 . individual redshifts for the nvss sources are thus required to alleviate projection effects and probe directly the matter power spectrum on large scales . large - scale structure of universe galaxies : active surveys
| 181
|
astro-ph0510257
|
we report the results of our _ chandra _ observations of six qsos at @xmath0 from the palomer transit grism survey . our primary goal is to investigate the possible systematic change of @xmath1 between @xmath2 and @xmath0 , between which a rapid rise of luminous qso number density with cosmic time is observed . the summed spectrum showed a power - law spectrum with photon index of @xmath3 , which is similar to other unabsorbed agns . combining our @xmath0 qsos with x - ray observations of qsos at @xmath2 from literaure / archive , we find a correlation of @xmath1 with optical luminosity . this is consistent with the fact that the luminosity function slope of the luminous end of the x - ray selected qsos is steeper than that of optically - selected qsos . we discuss an upper limit to the redshift dependence of @xmath1 using a monte - carlo simulation . within the current statistical errors including the derived limits on the redshift dependence of @xmath1 , we found that the behaviors of the x - ray and optically - selected qso number densities are consistent with each other .
| 195
|
cond-mat0502583
|
the increasing scientific and technological interest in nanoparticles has raised the need for fast , efficient and precise characterization techniques . powder diffraction is a very efficient experimental method , as it is straightforward and non - destructive . however , its use for extracting information regarding very small particles brings some common crystallographic approximations to and beyond their limits of validity . powder pattern diffraction calculation methods are critically discussed , with special focus on spherical particles with log - normal distribution , with the target of determining size distribution parameters . a 20-nm ceo@xmath0 sample is analyzed as example .
| 102
|
1202.5231
|
we extend the higgs triplet model so as to include dark matter candidates and a simple suppression mechanism for the vacuum expectation value ( @xmath0 ) of the triplet scalar field . the smallness of neutrino masses can be naturally explained with the suppressed value of @xmath0 even when the triplet fields are at the tev scale . the higgs sector is extended by introducing @xmath1-odd scalars ( an @xmath2 doublet @xmath3 and a real singlet @xmath4 ) in addition to a @xmath1-even complex singlet scalar @xmath5 whose vacuum expectation value violates the lepton number conservation by a unit . in our model , @xmath0 is generated by the one - loop diagram to which @xmath1-odd particles contribute . the lightest @xmath1-odd scalar boson can be a candidate for the dark matter . we briefly discuss a characteristic signal of our model at the lhc .
| 146
|
astro-ph0605158
|
we present new observations of the cepa - east region of massive star formation and describe an extended and dynamically distinct feature not previously recognised . this feature is present in emission from h@xmath0cs , ocs , ch@xmath1oh , and hdo at 5.5 km s@xmath2 , but is not traced by conventional tracers of star forming regions h@xmath0s , so@xmath0 , so , cs . the feature is extended up to at least 0.1 pc . we show that the feature is neither a hot core nor a shocked outflow . however , the chemistry of the feature is consistent with predictions of a model of an eroding interface between a fast wind and a dense core ; mixing between the two media occurs in the interface on a timescale of 10 - 50 years . if these observations are confirmed by detailed maps and by detections in species also predicted to be abundant ( e.g. hco@xmath3 , h@xmath0co , and nh@xmath1 ) this feature would be the first detection of such an interface in regions of massive star formation . an important implication of the model is that a significant reservoir of sulfur in grain mantles is required to be in the form of ocs .
| 207
|
1504.02703
|
a _ primitive hole _ of a graph @xmath0 is a cycle of length @xmath1 in @xmath0 . the number of primitive holes in a given graph @xmath0 is called the primitive hole number of that graph @xmath0 . the primitive degree of a vertex @xmath2 of a given graph @xmath0 is the number of primitive holes incident on the vertex @xmath2 . in this paper , we introduce the notion of set - graphs and study the properties and characteristics of set - graphs . we also check the primitive hole number and primitive degree of set - graphs . interesting introductory results on the nature of order of set - graphs , degree of the vertices corresponding to subsets of equal cardinality , the number of largest complete subgraphs in a set - graph etc . are discussed in this study . a recursive formula to determine the primitive hole number of a set - graph is also derived in this paper . * key words : * set - graphs , primitive hole , primitive degree . * ms classification * : 05c07 , 05c38 , 05c78 .
| 191
|
1105.3165
|
we investigate particle production in an expanding universe under the assumption that the lagrangian contains the einstein term @xmath0 plus a modified gravity term of the form @xmath1 , where @xmath2 is a constant . dark fluid is considered as the main content of the universe and the big rip singularity appears . quantum effects due to particle creation is analysed near the singularity and we find that for @xmath3\frac{1}{2 } , 1[$ ] , quantum effects are dominant and the big rip may be avoided whereas for @xmath4 the dark fluid is dominant and the singularity remains . the cardy - verlinde formula is also introduced and its equivalence with the total entropy of the universe is checked . it is found that this can always occur in einstein gravity while in f(r ) gravity , it holds only for @xmath5 , @xmath6 being the space dimension , corresponding to the situation in which the big rip can not be avoided . * quantum effects from particle production on background evolution and cardy - verlinde formula in f(r ) gravity + * m. j. s. houndjo , a . v. monwanouand jean b. chabi orou + pacs numbers : 04.50.kd , 98.80.cq , 02.40.xx , 05 .
| 208
|
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.