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4,100 | Suppose that you have an abstract for a scientific paper: we discuss the dynamics of intersecting @xmath0-branes with cosmological constants in the higher - dimensional gravity theories . for the delocalized brane case , these solutions describe an asymptotically de sitter or power - law expanding universe , while for the partially localized intersecting branes , they describe homogeneous and isotropic universes at each position of the overall transverse space .
we then apply these time - dependent branes to the study on the collision of two 0-branes and show that the 0@xmath18-brane system or the smeared @xmath2-brane system can provide an example of colliding branes if they have the same brane charges and only one overall transverse space .
finally , we argue some applications of the solutions in supergravity models . .
And you have already written the first three sentences of the full article: in many recent developments involving cosmological models and brane collisions in higher - dimensional gravity theories @xcite , the dynamical @xmath0-branes carrying charges have played important roles . in the classical solution of a single @xmath0-brane , the coupling of the dilaton to the field strength includes the parameter @xmath3 .
since these brane solutions with @xmath4 are related to well - known d - branes and m - branes in supergravity theories , they certainly exhibit many attractive properties in the higher - dimensional spacetime .
some static solutions with @xmath5 also have supersymmetry after dimensional reductions to lower - dimensional theory @xcite ..
Please generate the next two sentences of the article | the time - dependent generalizations of these solutions are thus important examples of higher - dimensional gravity theories .
the dynamical brane solution with the cosmological constant can be obtained by choosing the coupling constant appropriately @xcite . for a single 2-form field strength and a nontrivial dilaton |
4,101 | Suppose that you have an abstract for a scientific paper: three - dimensional ( 3d ) hydrodynamic simulations of shell oxygen burning @xcite exhibit bursty , recurrent fluctuations in turbulent kinetic energy .
these are shown to be due to a general instability of the convective cell , requiring only a localized source of heating or cooling .
such fluctuations are shown to be suppressed in simulations of stellar evolution which use mixing - length theory ( mlt ) .
quantitatively similar behavior occurs in the model of a convective roll ( cell ) of @xcite , which is known to have a strange attractor that gives rise to chaotic fluctuations in time of velocity and , as we show , luminosity .
study of simulations suggests that the behavior of a lorenz convective roll may resemble that of a cell in convective flow .
we examine some implications of this simplest approximation , and suggest paths for improvement .
using the lorenz model as representative of a convective cell , a multiple - cell model of a convective layer gives total luminosity fluctuations which are suggestive of irregular variables ( red giants and supergiants @xcite ) , and of the long secondary period feature in semiregular agb variables @xcite .
this @xmath0-mechanism " is a new source for stellar variability , which is inherently non - linear ( unseen in linear stability analysis ) , and one closely related to intermittency in turbulence .
it was already implicit in the 3d global simulations of @xcite .
this fluctuating behavior is seen in extended 2d simulations of cneosi burning shells @xcite , and may cause instability which leads to eruptions in progenitors of core collapse supernovae _ prior _ to collapse . .
And you have already written the first three sentences of the full article: three - dimensional fluid dynamic simulations of turbulent convection in an oxygen - burning shell of a presupernova star show bursty fluctuations which are not seen in one - dimensional stellar evolutionary calculations ( which use various versions of mixing - length theory , mlt , @xcite ) .
this paper explores the underlying physics of this new phenomena . since the formulation of mlt @xcite ,
there have been a number of significant developments in the theoretical understanding of turbulent convective flow ..
Please generate the next two sentences of the article | first , @xcite and @xcite developed the modern version of the turbulent cascade , and published in journals easily accessible in the west ; the original theory @xcite was not used in mlt although it pre - dated it . this explicit expression for dissipation of turbulent velocities ,
@xmath1 where @xmath2 is the root - mean - square of the turbulent velocity and @xmath3 is the dissipation length . |
4,102 | Suppose that you have an abstract for a scientific paper: existence of amplitude independent frequencies of oscillation is an unusual property for a nonlinear oscillator .
we find that a class of n coupled nonlinear linard type oscillators exhibit this interesting property .
we show that a specific subset can be explicitly solved from which we demonstrate the existence of periodic and quasiperiodic solutions .
another set of @xmath0-coupled nonlinear oscillators , possessing the amplitude independent nature of frequencies , is almost integrable in the sense that the system can be reduced to a single nonautonomous first order scalar differential equation which can be easily integrated numerically .
nonlinear oscillators , coupled ordinary differential equations , complete integrability , isochronous systems .
And you have already written the first three sentences of the full article: let us consider the following nonlinear oscillator described by the so called modified emden equation with linear forcing term @xcite , @xmath1 here @xmath2 is a parameter . equation ( 1 ) can be considered as the cubic anharmonic oscillator with additional position dependent damping type nonlinear force @xmath3 .
this type of equation has been well studied in the literature .
for example , eq ..
Please generate the next two sentences of the article | ( 1 ) with @xmath4 arises in a wide range of physical problems : it occurs in the study of equilibrium configurations of a spherical gas cloud acting under the mutual attraction of its molecules and subject to the laws of thermodynamics @xcite and in the modelling of the fusion of pellets @xcite .
it also governs spherically symmetric expansion or collapse of a relativistically gravitating mass @xcite . |
4,103 | Suppose that you have an abstract for a scientific paper: by using a previously developed phenomenological kernel for the study of the light quark qcd sector and dynamical chiral symmetry breaking effects we will examine the relative infrared and ultraviolet qcd dynamics for j=0,1 meson properties . for the same reasons we extend and explore a quark mass depended generalization of the kernel in the heavy quark region and we also compare with the original model .
the relation between the dynamics of the quark propagator and the effective kernel with the j=0,1 qq and qq mesons and quarks compton size is also discussed . .
And you have already written the first three sentences of the full article: a lot of effort has been focused on studying the spectrum and the properties of light quark mesons ( see @xcite-@xcite ) and references therein ) . in these systems
non - perturbative effects are dominant , therefore they are the best candidates for understanding the mechanisms underlying confinement and dynamical chiral symmetry breaking which are fundamental elements and of crucial importance for the theory . in some of these studies
the quark propagator equation has provide useful insights in the light quark sector of qcd @xcite , @xcite ..
Please generate the next two sentences of the article | it is also interesting to explore , using that fundamental block of the theory and the quarks bound state equation , the transition to heavy quark physics .
we plan to canvass , by using an effective kernel for the gap equation , how the quark mass affects the infrared and ultraviolet dressing of the propagator and how that in turn will alter the dynamics of the bound state of quarks . |
4,104 | Suppose that you have an abstract for a scientific paper: recent searches conducted at the fermilab tevatron for the higgs boson in the diphoton decay channel are reported using 7.0 fb@xmath0 and 8.2 fb@xmath0 of data collected at the cdf and d0 experiments , respectively .
although the standard model ( sm ) branching fraction is small , the diphoton final state is appealing due to better diphoton mass resolution compared with dijet final states .
in addition , other models such as fermiophobic models where the higgs does not couple to fermions predict much larger branching fractions for the diphoton decay . here , results are presented for both a sm and fermiophobic higgs boson as well as a sm search based on a combination of the cdf and d0 analyses . .
And you have already written the first three sentences of the full article: the standard model ( sm ) of particle physics has proven to be a robust theoretical model that very accurately describes the properties of elementary particles observed in nature and the forces of interaction between them . in this model , the electromagnetic and weak forces
are unified into a single electroweak theory .
the measured masses of the particles that mediate the electroweak force , however , are vastly different the photon has zero mass while the @xmath1 and @xmath2 bosons have masses almost 100 times heavier than the mass of a proton ..
Please generate the next two sentences of the article | to explain this difference , the theory predicts the existence of a higgs field which interacts with the elecroweak field via electroweak symmetry breaking to produce masses for the @xmath1 and @xmath2 bosons while leaving the photon massless .
interaction with the higgs field would also explain how other fundamental particles acquire mass . |
4,105 | Suppose that you have an abstract for a scientific paper: this paper is a continuation of the previous study [ amaj , l. : j. stat .
phys . * 137 * , 1 - 17 ( 2009 ) ] , where a sequence of sum rules for the equilibrium charge and current density correlation functions in an infinite ( bulk ) quantum media coupled to the radiation was derived by using rytov s fluctuational electrodynamics . here
, we extend the previous results to inhomogeneous situations , in particular to the three - dimensional interface geometry of two joint semi - infinite media .
the sum rules derived for the charge - charge density correlations represent a generalization of the previous ones , related to the interface dipole moment and to the long - ranged tail of the surface charge density correlation function along the interface of a conductor in contact with an inert ( not fluctuating ) dielectric wall , to two fluctuating semi - infinite media of any kind .
the charge - current and current - current sum rules obtained here are , to our knowledge , new .
the current - current sum rules indicate a breaking of the directional invariance of the diagonal current - current correlations by the interface .
the sum rules are expressed explicitly in the classical high - temperature limit ( the static case ) and for the jellium model ( the time - dependent case ) . .
And you have already written the first three sentences of the full article: the models studied in this paper are composed of spinless charged particles , classical or quantum , which are non - relativistic , i.e. they behave according to schrdinger and not dirac . on the other hand ,
the interaction of charged particles via the radiated electromagnetic ( em ) field can be considered either non - relativistic ( nonretarded ) or relativistic ( retarded ) . in the nonretarded regime ,
magnetic forces are ignored by taking the speed of light @xmath0 , so that the particles interact only via instantaneous coulomb potentials . in the retarded regime , @xmath1 is assumed finite and the particles are fully coupled to both electric ( longitudinal ) and magnetic ( transverse ) parts of the radiated field ..
Please generate the next two sentences of the article | one of the tasks in the equilibrium statistical mechanics of charged systems is to determine how fluctuations of microscopic quantities like charge and current densities , induced electric and magnetic fields , etc .
, around their mean values are correlated in time and space . |
4,106 | Suppose that you have an abstract for a scientific paper: we apply the generalized second law of thermodynamics to discriminate among quantum corrections ( whether logarithmic or power - law ) to the entropy of the apparent horizon in spatially friedmann - robertson - walker universes .
we use the corresponding modified friedmann equations along with either clausius relation or the principle of equipartition of the energy to set limits on the value of a characteristic parameter entering the said corrections . .
And you have already written the first three sentences of the full article: as is well known , event horizons , whether black holes or cosmologicals , mimic black bodies and possess a nonvanishing temperature and entropy , the latter obeying the bekenstein - hawking formula , @xcite @xmath0 this expression , in which @xmath1 stands for the boltzmann constant , @xmath2 the area of the horizon , and @xmath3 the planck s length , points to a deep connection between gravitation , thermodynamics , and quantum mechanics , still far from being fully unveiled though progress in that direction are being made -see , e.g. , @xcite and references therein .
recently it was demonstrated that cosmological apparent horizons are also endowed with thermodynamical properties , formally identical to those of event horizons @xcite .
the connection between gravity and thermodynamics was reinforced by jacobson , who associated einstein equations with clausius relation @xcite , and later on by padmanabhan who linked the macroscopic description of spacetime , given by einstein equations , to microscopic degrees of freedom , @xmath4 , through the principle of equipartition of energy , i.e. , @xmath5 in particular , padmanabhan , starting from the field equations arrived to the equipartition law @xcite and indicated how to obtain the field equations of any diffeormorphism invariant theory of gravity from an entropy extremising principle @xcite , the entropy of spacetime being proportional to @xmath4 ..
Please generate the next two sentences of the article | + on the other hand , quantum corrections to the semi - classical entropy - law ( [ entropy ] ) have been introduced in recent years , namely , logarithmic and power - law corrections .
logarithmic corrections , arises from loop quantum gravity due to thermal equilibrium fluctuations and quantum fluctuations @xcite , @xmath6 \ , .\ ] ] on its part , power - law corrections appear in dealing with the entanglement of quantum fields in and out the horizon @xcite , @xmath7 \ , .\ ] ] in the last two expressions , @xmath8 denotes a dimensionless parameter whose value ( in both cases ) is currently under debate . |
4,107 | Suppose that you have an abstract for a scientific paper: the analysis of hard x - ray features in _ xmm - newton _ data of the bright sy 1 galaxy mrk 335 is reported here .
the presence of a broad , ionised iron k@xmath0 emission line in the spectrum , first found by gondoin et al.(2002 ) , is confirmed .
the broad line can be modeled successfully by relativistic accretion disc reflection models .
regardless of the underlying continuum we report , for the first time in this source , the detection of a narrow absorption feature at the rest frame energy of 5.9 kev .
if the feature is identified with a resonance absorption line of iron in a highly ionised medium , the redshift of the line corresponds to an inflow velocity of 0.11 - 0.15 c. preliminary results from a longer ( 100ks ) exposure are also presented . .
And you have already written the first three sentences of the full article: the analysis of the epic data from a 30 ks observation of the seyfert 1 mrk 335 ( longinotti et al . 2006 ) shows that the 2 - 10 kev spectrum can be phenomenologically fitted with a power law , a broad gaussian line with [email protected] kev , @[email protected] kev , ew 490 ev , and a narrow ( @xmath2 = 1ev ) absorption line with [email protected] kev and ew=50 ev .
these features are visible in the residuals of the spectrum plotted in fig.1 .
the significance of the absorption line estimated through monte carlo simulations is 99.7% ..
Please generate the next two sentences of the article | the most obvious identification for the absorption feature is with redshifted iron k@xmath0 resonance absorption .
the identification with iron is favoured since the observed energy of the line is too high to be readily explained by k@xmath0 absorption in any of the other astrophysically abundant elements . |
4,108 | Suppose that you have an abstract for a scientific paper: using data obtained during the _ rats - kepler _ project we identified one short duration flare in a 1 hour sequence of ground based photometry of the dwarf star kic 5474065 .
observations made using gtc show it is a star with a m4 v spectral type . _
kepler _ observations made using 1 min sampling show that kic 5474065 exhibits large amplitude ( @xmath0f / [email protected] ) optical flares which have a duration as short as 10 mins .
we compare the energy distribution of flares from kic 5474065 with that of kic 9726699 , which has also been observed using 1 min sampling , and ground based observations of other m dwarf stars in the literature .
we discuss the possible implications of these short duration , relatively low energy flares would have on the atmosphere of exo - planets orbiting in the habitable zone of these flare stars . physical data and processes : magnetic reconnection astrobiology stars : activity stars : flares stars : late - type stars : individual : kic 5474065 , kic 9726699 .
And you have already written the first three sentences of the full article: flares with duration of a few to tens of minutes and energies of @xmath2 ergs have been observed on low mass dwarf stars for many decades ( eg bopp & moffett 1973 , gershberg & shakhovskaia 1983 ) .
the origin of these flares is thought to be similar to solar flares in that they are produced during magnetic reconnection events ( eg haisch , strong & rodono 1991 ) .
studying stellar flares from a wide range of stars can give important insight to how magnetic activity varies as a function of stellar mass and age ..
Please generate the next two sentences of the article | in more recent years , the affects of flares on the atmosphere of exo - planets around dwarf stars has been the subject of much interest ( eg segura et al 2010 ) .
historically the study of stellar flares was performed on known m dwarf stars . however , with the advent of large scale surveys such as sdss it has become possible to identify events from many previously unknown flare stars ( eg davenport et al 2012 ) . whilst this will no doubt prove a goldmine for stellar flare researchers , the issue of separating extra - galactic transient events and flares from m dwarfs will become increasingly difficult in future surveys such as that made using lsst . |
4,109 | Suppose that you have an abstract for a scientific paper: we prove an existence theorem for the cauchy problem on a characteristic cone for the vacuum einstein equations . .
And you have already written the first three sentences of the full article: in recent work @xcite ( see also @xcite ) we have analysed some aspects of the cauchy problem for the einstein equations with data on a characteristic cone in all dimensions @xmath0 , see @xcite and references therein for previous work on the subject . in this note
we apply the results derived in @xcite to present an existence theorem for this problem , with initial data which approach rapidly the flat metric near the tip of the light cone , see theorem [ t23vii.1 ] below .
the reader s attention is drawn to @xcite , where sets of unconstrained data on a light - cone centered at past timelike infinity are given in dimension @xmath1 ..
Please generate the next two sentences of the article | it is well known that by using normal coordinates centred at @xmath2 the characteristic cone @xmath3 of a given lorentzian metric can be written , at least in a neighbourhood of @xmath2 , as a cone in minkowski spacetime whose generators represent the null rays .
it is therefore no geometric restriction to assume that the characteristic cone of the spacetime we are looking for is represented in some coordinates @xmath4 , @xmath5 , @xmath6 of @xmath7 by the equation of a minkowskian cone with vertex @xmath2 , @xmath8 the parameter @xmath9 is an affine parameter when normal coordinates are used , and it is also going to be an affine parameter in the solutions that we are going to construct . |
4,110 | Suppose that you have an abstract for a scientific paper: the increasing number of crimes in areas with large concentrations of people have made cities one of the main sources of violence .
understanding characteristics of how crime rate expands and its relations with the cities size goes beyond an academic question , being a central issue for contemporary society . here , we characterize and analyze quantitative aspects of murders in the period from 1980 to 2009 in brazilian cities .
we find that the distribution of the annual , biannual and triannual logarithmic homicide growth rates exhibit the same functional form for distinct scales , that is , a scale invariant behavior .
we also identify asymptotic power - law decay relations between the standard deviations of these three growth rates and the initial size .
further , we discuss similarities with complex organizations . .
And you have already written the first three sentences of the full article: methods and techniques inspired by statistical physics have been shown to be useful in the search for hidden features in social systems @xcite . particularly , it has been remarked that social systems can exhibit universal properties similarly to thermodynamical systems at the criticality .
for example , scaling laws have been reported in scientific research @xcite , biological systems @xcite , economics @xcite and religious @xcite activities .
in addition , there is some evidence about the relation between urban metrics and the population size , where non - linearities are explicitly manifested by power - laws @xcite ..
Please generate the next two sentences of the article | more recently , phase transition was also found in a model for criminality @xcite .
crime is one of the major concerns of contemporary society and , therefore , there is a great interest in understanding features of its organization and dynamics . |
4,111 | Suppose that you have an abstract for a scientific paper: the path integral monte carlo method is used to simulate dilute trapped bose gases and to investigate the equilibrium properties at finite temperatures .
the quantum particles have a long - range dipole - dipole interaction and a short - range @xmath0-wave interaction . using an anisotropic pseudopotential for the long - range dipolar interaction and a hard - sphere potential for the short - range @xmath0-wave interaction , we calculate the energetics and structural properties as a function of temperature and the number of particles . also ,
in order to determine the effects of dipole - dipole forces and the influence of the trapping field on the dipolar condensate , we use two cylindrically symmetric harmonic confinements ( a cigar - shaped trap and a disk - shaped trap ) . we find that the net effect of dipole - dipole interactions is governed by the trapping geometry . for a cigar - shaped trap ,
the net contribution of dipolar interactions is attractive and the shrinking of the density profiles is observed . for a disk - shaped trap ,
the net effect of long - range dipolar forces is repulsive and the density profiles expand . .
And you have already written the first three sentences of the full article: the experimental observation of bose - einstein condensation ( bec ) in dilute trapped and supercooled atomic vapors @xcite has stimulated enormous experimental and theoretical interest in the physics of the weakly interacting bose gas ( see @xcite for a review ) .
especially intriguing is the role of dimensionality and two - body interactions .
lower dimensional atomic gases have been realized with strong quantum confinement in one or more directions ..
Please generate the next two sentences of the article | these systems exhibit very peculiar properties , such as the exact mapping between interacting bosons and noninteracting fermions ( tonks - girardeau gas ) @xcite , because the role of quantum fluctuations and strong correlations is enhanced .
although these gases are very dilute , bec of trapped atomic gases is strongly influenced by two - body interactions . within a mean - field approximation , |
4,112 | Suppose that you have an abstract for a scientific paper: observations of the c iv and mg ii absorption lines in the seyfert 1 galaxy ngc 4151 obtained with the ghrs in october 1994 are presented .
the data from the stsci archive show multiple broad and narrow components in both species .
in addition to galactic absorption , four narrow and four broad systems associated with ngc 4151 are identified .
two broad systems dominate the total equivalent width , and their mean blueshift and width are comparable to the broad lyman line and continuum absorption seen in far - uv spectra from the hopkins ultraviolet telescope . narrow - line c iv emission is present on the red side of the broadest absorption trough , and narrow absorption at the systemic velocity of ngc 4151 , presumably in its own ism , absorbs the core of the narrow emission line .
strong mg ii absorption is present in all but two velocity systems .
ratios relative to the corresponding c iv components suggest a low ionization parameter for the absorbing gas : @xmath0 .
this makes none of the identified uv absorption systems a good candidate for association with the warm x - ray absorbing gas . .
And you have already written the first three sentences of the full article: a persistent problem in understanding the absorbing material in ngc 4151 has been reconciling the vastly different gas columns inferred for the x - ray absorption and for the uv absorption .
the x - ray absorbing column varies between @xmath1 and @xmath2 .
bromage et al ..
Please generate the next two sentences of the article | ( 1985 ) estimated a total column for the uv - absorbing material of no more than @xmath3 .
the neutral hydrogen column is variable ( kriss et al . |
4,113 | Suppose that you have an abstract for a scientific paper: galaxies arrive on the red sequences of clusters at high redshift ( @xmath0 ) once their star formation is quenched and evolve passively thereafter .
however , we have previously found that cluster red sequence galaxies ( crsgs ) undergo significant morphological evolution subsequent to the cessation of star formation , at some point in the past 9 - 10 gyr . through a detailed study of a large sample of cluster red sequence galaxies spanning @xmath1
we elucidate the details of this evolution . below @xmath2 ( in the last 5 - 6 gyr )
there is little or no morphological evolution in the population as a whole , unlike in the previous 4 - 5 gyrs . over this earlier time
( i ) disk - like systems with srsic @xmath3 progressively disappear , as ( ii ) the range of their axial ratios similarly decreases , removing the most elongated systems ( those consistent with thin disks seen at an appreciable inclination angle ) , and ( iii ) radial colour gradients ( bluer outwards ) decrease in an absolute sense from significant age - related gradients to a residual level consistent with the metallicity - induced gradients seen in low redshift cluster members .
the distribution of their effective radii shows some evidence of evolution , consistent with growth of _ at most _
a factor @xmath4 between @xmath5 and @xmath6 , significantly less than for comparable field galaxies , while the distribution of their central ( @xmath7kpc ) bulge surface densities shows no evolution at least at @xmath8 .
a simple model involving the fading and thickening of a disk component after comparatively recent quenching ( after @xmath9 ) around an otherwise passively evolving older spheroid component is consistent with all of these findings .
[ firstpage ] galaxies : formation and evolution galaxies : interactions .
And you have already written the first three sentences of the full article: an advantage of studying the cluster galaxy population to test theories of galaxy formation is that , once a galaxy has entered a cluster , it will likely remain within a high density environment .
we can therefore trace a more direct evolutionary connection between high redshift and local systems without needing to appeal to abundance matching to link populations at different epochs ( e.g. , @xcite _ et seq . _ ) , where the large intrinsic scatter in galaxy growth rates in simulations implies that one can not unambiguously identify galaxy progenitors and descendants between different observational epochs in the field @xcite .
the homogeneity of cluster samples offers a snapshot of galaxy properties at each epoch , providing a more direct link between galaxy progenitors and descendants . for this reason.
Please generate the next two sentences of the article | , cluster galaxies may serve as an important benchmark for models of galaxy formation and evolution , as well as being useful cosmological probes .
the most distinctive and characteristic population of cluster galaxies at @xmath8 are the cluster red sequence galaxies ( crsgs ) . |
4,114 | Suppose that you have an abstract for a scientific paper: we investigate the privacy amplification problem in which eve can observe the uniform binary source through a binary erasure channel ( bec ) or a binary symmetric channel ( bsc ) . for this problem
, we derive the so - called expurgation exponent of the information leaked to eve .
the exponent is derived by relating the leaked information to the error probability of the linear code that is generated by the linear hash function used in the privacy amplification , which is also interesting in its own right .
the derived exponent is larger than state - of - the - art exponent recently derived by hayashi at low rate . .
And you have already written the first three sentences of the full article: in information theoretic key agreement problem @xcite , legitimate parties need to distill a secret key from a random variable in the situation such that an eavesdropper can access to a random variable that is correlated to the legitimate parties random variable .
the privacy amplification is a technique to distill a secret key under the situation by using a ( possibly random ) function @xcite .
the security of distilled key is evaluated by various kinds of measures . in this paper , we focus on the leaked information , which is the mutual information between the distilled key and eavesdropper s random variable ( the so - called strong security @xcite ) , because it is the strongest notion among security criterion @xcite ( see also ( * ? ? ?.
Please generate the next two sentences of the article | * appendix 3 ) ) .
the privacy amplification is usually conducted by using a family of universal 2 hash functions @xcite . in @xcite , |
4,115 | Suppose that you have an abstract for a scientific paper: we study the lift - and - project procedures of lovsz and schrijver for 0 - 1 integer programming problems .
we prove that the procedure using the positive semidefiniteness constraint is not better than the one without it , in the worst case .
various examples are considered .
we also provide geometric conditions characterizing when the positive semidefiniteness constraint does not help .
* keywords : * semidefinite lifting , semidefinite programming , lift - and - project , integer programming * ams subject classification : * 90c10 , 90c27 , 47d20 .
And you have already written the first three sentences of the full article: lovsz and schrijver ( 1991 ) have proposed a very intriguing successive convex relaxation procedure for 0 - 1 integer programming problems .
the procedure called @xmath0 , to be defined shortly , when applied to a classical linear programming ( lp ) relaxation of the stable set problem ( with only the edge and nonnegativity constraints ) produces a relaxation for which many well - known inequalities are valid , including the odd hole , odd antihole , odd wheel , clique , and even the orthonormal representation inequalities of grtschel , lovsz and schrijver ( 1981 ) .
this implies that for many classes of graphs , including perfect ( for which clique inequalities are sufficient ) or t - perfect graphs ( for which odd hole inequalities are sufficient ) , one can find the maximum stable set by using the @xmath0 procedure ..
Please generate the next two sentences of the article | the @xmath0 procedure is a strengthening of another procedure , called @xmath1 , also introduced by lovsz and schrijver .
the main difference between the two procedures is that @xmath0 involves a positive semidefinite constraint . |
4,116 | Suppose that you have an abstract for a scientific paper: the evolution of resistivity versus temperature ( @xmath0 ) curve for different doping elements , and in the presence of various defects and clustering are explained for both diluted magnetic semiconductors ( dms ) and manganites .
here , we provide unambiguous evidence that the concept of ionization energy ( @xmath1 ) , which is explicitly associated with the atomic energy levels , can be related quantitatively to transport measurements .
the proposed ionization energy model is used to understand how the valence states of ions affect the evolution of @xmath0 curves for different doping elements .
we also explain how the @xmath0 curves evolve in the presence of , and in the absence of defects and clustering .
the model also complements the results obtained from first - principles calculations . .
And you have already written the first three sentences of the full article: ferromagnets have the tremendous potential for the development of spintronics and subsequently will lay the foundation to realize quantum computing .
the field of spintronics require the incorporation of the spin - property of the electrons into the existing charge transport devices @xcite .
parallel to this , the technological potential of dms ( ref ..
Please generate the next two sentences of the article | @xcite ) is associated to spintronics - device development , whereas manganites that show a large drop of resistance below @xmath2 lead to the colossal magnetoresistance effect ( cmr ) , which is also important in the new technologies such as read / write heads for high - capacity magnetic storage and spintronics @xcite . as such
, applications involving both dms and manganites very much depend on our understanding of their transport properties at various doping levels and temperatures ( @xmath3 ) . |
4,117 | Suppose that you have an abstract for a scientific paper: we describe deep , new , wide - field radio continuum observations of the great observatories origins deep survey north ( goods - n ) field .
the resulting map has a synthesized beamsize of @xmath01.7 and an r.m.s .
noise level of @xmath03.9@xmath1jybeam@xmath2 near its center and @xmath08@xmath1jybeam@xmath2 at 15 from phase center .
we have cataloged 1,230 discrete radio emitters , within a 40@xmath340region , above a 5-@xmath4 detection threshold of @xmath020@xmath1jy at the field center .
new techniques , pioneered by @xcite , have enabled us to achieve a dynamic range of 6800:1 in a field that has significantly strong confusing sources .
we compare the 1.4-ghz ( 20-cm ) source counts with those from other published radio surveys .
our differential counts are nearly euclidean below 100@xmath1jy with a median source diameter of @xmath01.2 .
this adds to the evidence presented by @xcite that the natural confusion limit may lie near 1@xmath1jy .
if the euclidean slope of the counts continues down to the natural confusion limit as an extrapolation of our log n - log s , this indicates that the cutoff must be fairly sharp below 1 @xmath1jy else the cosmic microwave background temperature would increase above 2.7k at 1.4 ghz . .
And you have already written the first three sentences of the full article: the goods - n field @xcite covers @xmath5arcmin@xmath6 centered on the hubble deep field north @xcite and is unrivaled in terms of its ancillary data .
these include extremely deep _ chandra _ , _ hubble space telescope _ and _ spitzer _ observations , deep @xmath7 ground - based imaging and @xmath03,500 spectroscopic redshifts from 810-m telescopes .
previous radio observations of this region , however , fell short of complementing this unique dataset ..
Please generate the next two sentences of the article | cccc nov - dec 1996 & 42 & ar368 & a + feb 2005 & 28 & am825 & b + aug 2005 & 7 & am825 & c + dec 2005 & 2 & am825 & d + feb - apr 2006 & 86 & am857 & a + radio emission is a relatively unbiased tracer of star formation and can probe heavily obscured active galactic nuclei ( agn ) objects that are missed by even the deepest x - ray surveys .
radio observations thus allow us to fully exploit the wealth of data taken at x - ray through millimeter wavelengths , providing a unique extinction - free probe of galaxy growth and evolution through the detection of starbursts and agn . |
4,118 | Suppose that you have an abstract for a scientific paper: in many real applications that use and analyze networked data , the links in the network graph may be erroneous , or derived from probabilistic techniques . in such cases , the node classification problem can be challenging , since the unreliability of the links may affect the final results of the classification process .
if the information about link reliability is not used explicitly , the classification accuracy in the underlying network may be affected adversely . in this paper , we focus on situations that require the analysis of the uncertainty that is present in the graph structure .
we study the novel problem of node classification in uncertain graphs , by treating uncertainty as a first - class citizen .
we propose two techniques based on a bayes model and automatic parameter selection , and show that the incorporation of uncertainty in the classification process as a first - class citizen is beneficial .
we experimentally evaluate the proposed approach using different real data sets , and study the behavior of the algorithms under different conditions .
the results demonstrate the effectiveness and efficiency of our approach .
= 1 .
And you have already written the first three sentences of the full article: the problem of collective classification is a widely studied one in the context of graph mining and social networking applications . in this problem
, we have a network containing nodes and edges , which can be represented as a graph .
nodes in this network may be labeled , but it is not necessary that all nodes have a label . typically , such labels may represent some properties of interest in the underlying network ..
Please generate the next two sentences of the article | this is a setting that appears in several situations in practice .
some examples of such labeled networks in real scenarios are listed below : * in a bibliographic network , nodes correspond to authors , and the edges between them correspond to co - authorship links . |
4,119 | Suppose that you have an abstract for a scientific paper: we examine the large - network , low - loading behaviour of an attractor neural network , the so - called bistable gradient network ( bgn ) .
we use analytical and numerical methods to characterize the attractor states of the network and their basins of attraction .
the energy landscape is more complex than that of the hopfield network and depends on the strength of the coupling among units . at weak coupling ,
the bgn acts as a highly selective associative memory ; the input must be close to the one of the stored patterns in order to be recognized .
a category of spurious attractors occurs which is not present in the hopfield network .
stronger coupling results in a transition to a more hopfield - like regime with large basins of attraction .
the basins of attraction for spurious attractors are noticeably suppressed compared to the hopfield case , even though the hebbian synaptic structure is the same and there is no stochastic noise . .
And you have already written the first three sentences of the full article: many neural network models@xcite@xcite , in addition to their potential applications to computation , robotics and artificial intelligence , constitute intriguing dynamical systems in their own right , showing unusual manifestations of the statistical mechanics phenomena of order , disorder and frustration .
the connection between neural networks and statistical mechanics became especially clear with the introduction of the hopfield @xcite@xcite model , which furnishes a model of associative memory , or the recall of a memorized pattern from an incomplete stimulus .
this model has a well - defined energy function and is closely related to the sherrington - kirkpatrick spin glass model @xcite@xcite . in this paper.
Please generate the next two sentences of the article | we consider a hopfield - like network of @xmath0 bistable elements , the bistable gradient network or bgn , previously introduced in @xcite .
a closely related model was also discussed in @xcite and suggested as a model for the so - called `` bistability of perception '' in the interpretation of ambiguous visual stimuli @xcite . |
4,120 | Suppose that you have an abstract for a scientific paper: we present a novel method for solving canonical correlation analysis ( cca ) in a sparse convex framework using a least squares approach .
the presented method focuses on the scenario when one is interested in ( or limited to ) a primal representation for the first view while having a dual representation for the second view .
sparse cca ( scca ) minimises the number of features used in both the primal and dual projections while maximising the correlation between the two views .
the method is demonstrated on two paired corpuses of english - french and english - spanish for mate - retrieval .
we are able to observe , in the mate - retreival , that when the number of the original features is large scca outperforms kernel cca ( kcca ) , learning the common semantic space from a sparse set of features . .
And you have already written the first three sentences of the full article: proposed by @xcite , cca is a technique for finding pairs of vectors that maximises the correlation between a set of paired variables .
the set of paired variables can be considered as two views of the same object , a perspective we adopt throughout the paper . since the debut of cca , a multitude of analyses , adaptations and applications have been proposed @xcite . + +
the potential disadvantage of cca and similar statistical methods , such as principle component analysis ( pca ) and partial least squares ( pls ) , is that the learned projections are a linear combination of all the features in the primal and dual representations respectively . this makes the interpretation of the solutions difficult ..
Please generate the next two sentences of the article | studies by @xcite and the more recent @xcite have addressed this issue for pca and pls by learning only the relevant features that maximise the variance for pca and covariance for pls . a previous application of sparse cca has been proposed in @xcite where the authors imposed sparsity on the semantic space by penalising the cardinality of the solution vector @xcite . the scca presented in this paper is novel to the extent that instead of working with covariance matrices @xcite , which may be computationally intensive to compute when the dimensionality of the data is large , it deals directly with the training data .
+ + in the machine learning ( ml ) community it is common practice to refer to the input space as the primal - representation and the kernel space as the dual - representation . in order to avoid confusion with the meanings of the terms primal and dual commonly used in the optimisation literature , we will use ml - primal to refer to the input space and ml - dual to refer to the kernel space for the remainder of the paper , though note that the references to primal and dual in the abstract refer to ml - primal and ml - dual . |
4,121 | Suppose that you have an abstract for a scientific paper: we study the effect of a dc magnetic field on the phase sensitivity of a double - lambda system coupled by two laser fields , a probe and a pump .
it is demonstrated that the gain and the refractive index of the probe can be controlled by either the magnetic field or the relative phase between the two laser fields .
more interestingly , when the system reduces to a single - lambda system , turning on the magnetic field transforms the system from a phase - insensitive process to a phase - sensitive one . in the pulsed - probe regime , we observed switching between slow and fast light when the magnetic field or the relative phase was adjusted .
experiments using a coated @xmath0rb vapor cell produced results in good agreement with our numerical simulation .
this work provides a novel and simple means to manipulate phase sensitive electromagnetically - induced - transparency or four - wave mixing , and could be useful for applications in quantum optics , nonlinear optics and magnetometery based on such systems .
99 k. j. boiler , a. imamoglu , and s. e. harris , `` observation of electromagnetically induced transparency , '' 25932596 ( 1991 ) .
m. d. lukin , `` _ colloquium _ : trapping and manipulating photon states in atomic ensembles , '' 457472 ( 2003 ) .
m. fleischhauer , a. imamoglu , and j. p. marangos , `` electromagnetically induced transparency : optics in coherent media , '' 633673 ( 2005 ) .
y. zhang and m. xiao , _ multi - wave mixing processes _
( springer , berlin , 2009 ) .
s. j. buckle , s. m. barnett , p. l. knigt , m. a. lauder , and d. t. pegg , `` atomic interferometers : phase - dependence in multilevel atomic transitions , '' opt .
acta * 33 , * 11291140 ( 1986 ) .
s. p. krinitzky and d. t. pegg , `` coherent irradiation of multilevel atoms in branched and cyclic configurations , '' 403406 ( 1986 ) .
e. a. korsunsky , n. leinfellner , a. huss , s. baluschev , and l. windholz , `` phase - dependent electromagnetically induced transparency , ''....
And you have already written the first three sentences of the full article: quantum interference between different excitation path ways is an intriguing phenomenon in quantum optics , laser and atomic physics .
notable examples are electromagnetically induced transparency ( eit ) @xcite , multi - wave mixing @xcite etc . among these ,
an interesting category is the phase - sensitive process formed by closed - loop interactions , where the phases of the optical fields can dramatically change the steady state of the atoms and the optical susceptibility ..
Please generate the next two sentences of the article | there has been a large amount of work in this field since the 1980s @xcite , and the interests boosted after the experimental demonstration of phase - sensitive eit @xcite .
applications of phase sensitive processes include large nonlinearity @xcite , slow and fast light @xcite , and optical switch @xcite etc . to the best of our knowledge , |
4,122 | Suppose that you have an abstract for a scientific paper: we study fractality of unbounded sets of finite lebesgue measure at infinity by introducing the notions of minkowski dimension and content at infinity .
we also introduce the lapidus zeta function at infinity , study its properties and demonstrate its use in analysis of fractal properties of unbounded sets at infinity . .
And you have already written the first three sentences of the full article: in this paper we are interested in relative fractal drums @xmath0 in which the set @xmath1 has degenerated to the point at infinity . in short ,
a relative fractal drum @xmath0 generalizes the notion of a bounded subset of @xmath2 and is defined as an ordered pair of subsets of @xmath2 where @xmath1 is nonempty and @xmath3 is of finite @xmath4-dimensional lebesgue measure satisfying a mild technical condition .
the lapidus ( or distance ) zeta function of @xmath0 is then defined as the lebesgue integral @xmath5 for all @xmath6 such that @xmath7 is sufficiently large , where @xmath8 denotes the euclidean distance from @xmath9 to @xmath1 ..
Please generate the next two sentences of the article | its main property is that the _ abscissa of convergence _ @xmath10 of @xmath11 coincides with the upper box dimension of @xmath0 , i.e. , @xmath12 . in other words ,
the integral converges absolutely and defines a holomorphic function in the open half - plane @xmath13 . for the study of relative fractal drums , their corresponding fractal zeta functions and the general higher - dimensional theory of complex dimensions |
4,123 | Suppose that you have an abstract for a scientific paper: we introduce and study a family of simplicial complexes associated to an arbitrary finite root system and a nonnegative integer parameter @xmath0 . for @xmath1 ,
our construction specializes to the ( simplicial ) generalized associahedra or , equivalently , to the cluster complexes for the cluster algebras of finite type .
our computation of the face numbers and @xmath2-vectors of these complexes produces the enumerative invariants defined in other contexts by c. a. athanasiadis , suggesting links to a host of well studied problems in algebraic combinatorics of finite coxeter groups , root systems , and hyperplane arrangements .
recurrences satisfied by the face numbers of our complexes lead to combinatorial algorithms for determining coxeter - theoretic invariants .
that is , starting with a coxeter diagram of a finite coxeter group , one can compute the coxeter number , the exponents , and other classical invariants by a recursive procedure that only uses most basic graph - theoretic concepts applied to the input diagram . .
And you have already written the first three sentences of the full article: in the first part of this paper ( sections [ sec : cluster - complexes][sec : recip ] ) , we introduce and study a simplicial complex @xmath3 associated to a finite root system @xmath4 and a nonnegative integer parameter @xmath0 . for @xmath5 ,
our construction specializes to the ( simplicial ) generalized associahedra @xmath6 introduced in @xcite and identified in @xcite as the underlying complexes for the cluster algebras of finite type .
we enumerate the faces of the complexes @xmath3 and determine their euler characteristics ..
Please generate the next two sentences of the article | for the classical types in the cartan - killing classification , we provide explicit combinatorial descriptions of these complexes in terms of dissections of a convex polygon into smaller polygons . in types
@xmath7 and @xmath8 , we rediscover the constructions given by e. tzanaki @xcite . |
4,124 | Suppose that you have an abstract for a scientific paper: in this paper a measure of non - convexity for a simple polygonal region in the plane is introduced .
it is proved that for `` not far from convex '' regions this measure does not decrease under the minkowski sum operation , and guarantees that the minkowski sum has no `` holes '' . .
And you have already written the first three sentences of the full article: let us state the definition of the minkowski sum of two sets @xmath0 .
the _ minkowski sum _ is @xmath1 in this paper we consider minkowski sums in the plane .
it is well - known , that the minkowski sum of two convex sets is again convex . in the case of convex polygons.
Please generate the next two sentences of the article | it is computed by a simple `` edge merging and slope sorting '' algorithm .
if we consider non - convex polygons , the computation of the minkowski sum may require more complicated algorithms , see @xcite for example . in the cited papers the problem of finding the minkowski sum arised from packing or motion planning problems . |
4,125 | Suppose that you have an abstract for a scientific paper: the potentials of spin - weighted wave equations in various kerr - newman black holes are analyzed .
they all form singular potential barriers at the event horizon . applying the wkb approximation it is shown that no particle can tunnel out of the interior of a static black hole .
however , photons inside a non - extremely rotating kerr black hole may tunnel out into the outer space , whereas neutrinos , electrons , and gravitons may not .
if the rotation is extremal , any particle may tunnel out , under restrictive conditions .
it is unknown whether photons and gravitons may tunnel out if the black hole is charged and rotating . .
And you have already written the first three sentences of the full article: in classical general relativity a causal particle inside the event horizon is inevitably pulled towards the center of the black hole , at least until it reaches the cauchy horizon representing a barrier to predictability @xcite . in particular , no classically relativistic particle , be it of positive or vanishing rest - mass , can escape from the black hole interior .
however , hawking @xcite has shown that photons in effect can leave the black hole if a quantized photon field in the curved spacetime is supposed , cf .
@xcite . in general , quantization of spin - weighted waves in a curved spacetime.
Please generate the next two sentences of the article | yields the notion of spin particles in a gravitational field . as such
, spin - weighted waves are the basis for semiclassical quantum gravity . |
4,126 | Suppose that you have an abstract for a scientific paper: it is known that a semi - classical analysis is not always adequate for atomtronics devices , but that a fully quantum analysis is often necessary to make reliable predictions . while small numbers of atoms at a small number of sites are tractable using the density matrix , a fully quantum analysis is often not straightforward as the system becomes larger .
we show that the fully quantum positive - p representation is then a viable calculational tool .
we postulate an atomtronic phase - gate consisting of four wells in a bose - hubbard configuration , for which the semi - classical dynamics are controllable using the phase of the atomic mode in one of the wells .
we show that the quantum predictions of the positive - p representation for the performance of this device have little relation to those found semi - classically , and that the performance depends markedly on the actual quantum states of the initially occupied modes .
we find that initial coherent states lead to closest to classical dynamics , but that initial fock states give results that are quite different .
a fully quantum analysis also opens the door for deeply quantum atomtronics , in which properties such as entanglement and epr ( einstein - podolsky - rosen ) steering become valuable technical properties of a device . .
And you have already written the first three sentences of the full article: atomtronics is an emerging area of investigation in which analogues of electronic circuits and devices are constructed using ultra - cold bosonic atoms rather than electrons as in conventional electronics @xcite .
the conventional way to construct an atomtronic device is to use cold atoms trapped in an optical lattice , which has a description in terms of either the mott - hubbard model transferred from condensed matter physics @xcite for fermionic atoms , and the bose - hubbard model for bosonic atoms @xcite .
these models can represent either insulating behaviour , in the mott insulator regime , or conducting behaviour , in the superfluid regime . in this work we consider only bosonic atoms . shortly after the realisation of trapped bose - einstein condensates ( bec ) , jaksch _ et al . _.
Please generate the next two sentences of the article | @xcite showed that the bose - hubbard model can provide an accurate description of bosonic atoms trapped in a deep optical lattice .
the basics of this model have been used to investigate a wide variety of atomtronic devices @xcite , including one with diode - like behaviour @xcite , a single - atom switching transistor @xcite , and one which uses a triple well configuration to mimic a field effect transistor @xcite . |
4,127 | Suppose that you have an abstract for a scientific paper: motivated by recent experiments and models of biological segmentation , we analyze the excitation of pattern - forming instabilities in convectively unstable reaction - diffusion - advection systems , occuring by constant or periodic forcing at the upstream boundary .
such boundary - controlled pattern selection is a generalization of the flow - distributed - oscillation ( fdo ) mechanism that can be modified to include differential diffusion ( turing ) and differential flow ( difi ) modes .
our goal is to clarify the relationships among these mechanisms in the general case where there is differential flow as well as differential diffusion .
we do so by analyzing the dispersion relation for linear perturbations and showing how its solutions are affected by differential transport .
we find a close relationship between difi and fdo modes , while the turing mechanism gives rise to a distinct set of unstable modes .
finally , we illustrate the relevance of the dispersion relations using nonlinear simulations and we discuss experimental implications of our results . .
And you have already written the first three sentences of the full article: recently , theoretical @xcite-@xcite and experimental @xcite,@xcite-@xcite attention has been focused on spatiotemporal instabilities in one - dimensional reactive flows . among these pattern - forming instabilities
are the differential flow ( difi)@xcite@xcite@xcite@xcite , turing@xcite@xcite , and the physically distinct flow - distributed oscillation ( fdo)@xcite@xcite@xcite@xcite@xcite mechanisms .
two of these , difi and fdo , necessarily involve a flow , while turing and difi necessarily involve the differential transport of activator and inhibitor species ..
Please generate the next two sentences of the article | instabilities in a flowing medium may be absolute or convective.@xcite@xcite@xcite@xcite . in the first case
, a localized disturbance grows with time and spreads both upstream and downstream . in the convective case , |
4,128 | Suppose that you have an abstract for a scientific paper: we propose a mechanism for the early generation of the mean intracluster magnetic field in terms of magnetized galactic winds .
these winds are the result of starburst phases of the cluster galaxies , assumed to produce the predominant population of early type galaxies in mergers of gas - rich progenitors . after further cluster contraction
typical field strengths are @xmath0 gauss .
this estimate may increase to the level of @xmath1 gauss if more extreme galactic parameters , and subsequent shear amplification of the field are considered .
the topology of the field is one of almost unconnected wind bubbles with parker - type spiral field configurations over scales of the distance between galaxies .
further cluster accretion , that continues chaotically in space and time up to the present , will perturb these `` large - scale '' mean fields on smaller or at best comparable spatial scales .
the small scale fields in the resulting turbulent fluctuation spectrum should be able to confine relativistic particles over times longer than the age of the universe .
the nonthermal particle content of galaxy clusters should therefore also have a `` cosmological '' hadronic component generated during the early starburst phase of the member galaxies . already by itself
it implies a nonthermal energy fraction of about 10 percent for the intracluster gas which should then be detectable by future gamma - ray telescopes . .
And you have already written the first three sentences of the full article: rich clusters of galaxies are the largest gravitationally bound structures in the universe and should confine a representative fraction of its mass .
therefore the study of their dynamical properties and radiation content should allow , amongst other things , interesting cosmological conclusions on the relative amounts of visible and dark baryonic matter , and of nonbaryonic matter ( @xcite ) .
another basic characteristic , due to energetic particle confinement , is the ratio of nonthermal to thermal energy in these objects . to a significant extent.
Please generate the next two sentences of the article | that ratio should be pre - determined during the epoch of early starburst activity and thus preserve the energetic history of cluster formation .
the necessary confinement of the nonthermal particle components is intimately related to the existence of strong and chaotic magnetic fields in the intracluster medium ( icm ) , and we shall propose physical mechanisms for their early generation as well as for their present fluctuations . in principle , |
4,129 | Suppose that you have an abstract for a scientific paper: we study two - player security games which can be viewed as sequences of nonzero - sum matrix games played by an attacker and a defender .
the evolution of the game is based on a stochastic fictitious play process , where players do not have access to each other s payoff matrix .
each has to observe the other s actions up to present and plays the action generated based on the best response to these observations . in a regular fictitious play process , each player makes a maximum likelihood estimate of her opponent s mixed strategy , which results in a time - varying update based on the previous estimate and current action . in this paper
, we explore an alternative scheme for frequency update , whose mean dynamic is instead time - invariant . we examine convergence properties of the mean dynamic of the fictitious play process with such an update scheme , and establish local stability of the equilibrium point when both players are restricted to two actions .
we also propose an adaptive algorithm based on this time - invariant frequency update . .
And you have already written the first three sentences of the full article: game theory has recently been used as an effective tool to model and solve many security problems in computer and communication networks . in a noncooperative matrix game between an attacker and a defender ,
if the payoff matrices are assumed to be known to both players , each player can compute the set of nash equilibria of the game and play one of these strategies to maximize her expected gain ( or minimize its expected loss ) .
however , in practice , the players do not necessarily have full knowledge of each other s payoff matrix ..
Please generate the next two sentences of the article | for repeated games , a mechanism called fictitious play ( fp ) can be used for each player to learn her opponent s motivations . in a fp process
, each player observes all the actions and makes estimates of the mixed strategy of her opponent . at each stage , she updates this estimate and plays the pure strategy that is the best response ( or generated based on the best response ) to the current estimate of the other s mixed strategy . |
4,130 | Suppose that you have an abstract for a scientific paper: it is numerically demonstrated that effectively strong diamagnetic resonance emerges at visible frequencies in stratified metal - dielectric metamaterials .
the effective optical constants are extracted by two - complex reflectivity method .
it is clarified that the effective diamagnetic response originates from local diamagnetism at stratified thin metals .
the effective diamagnetism is crucially sensitive to the sturucture of unitcell .
the effective diamagnetic response is always associated with effective plasma frequency and is therefore regarded as a magnetic component of the collective excitation . .
And you have already written the first three sentences of the full article: photonic metamaterials are trials to invent and produce novel electromagnetic ( em ) states by modifying periodic structures in which constituents have the same optical constants with the bulk materials .
the trials started at gigahertz , and has proceeded to terahertz and optical frequencies .
the rapid progress was reviewed in @xcite ..
Please generate the next two sentences of the article | the strategy is significantly different from nano - scale materials science in which quantum size effect on electronic states is a key . in metamaterials ,
novel effective em states are explored by controlling the geometrical structures . |
4,131 | Suppose that you have an abstract for a scientific paper: we present 21 cm observations of arp 158 .
we have performed a study of the neutral hydrogen ( h@xmath0i ) to help us understand the overall formation and evolution of this system .
this is a disturbed system with distinct optical knots connected by a linear structure embedded in luminous material .
there is also a diffuse spray to the southeast .
the h@xmath0i seems to be made up of three distinct , kinematically separate systems .
arp 158 bears a certain optical resemblance to ngc 520 ( arp 157 ) , which has been identified as a mid - stage merger . from our 21 cm observations of arp 158
, we also see a comparable h@xmath0i content with ngc 520 .
these similarities suggest that arp 158 is also an intermediate stage merger . .
And you have already written the first three sentences of the full article: in the early seventies , toomre ( 1970 ) and toomre & toomre ( 1972 ) , presented numerical models which demonstrated that strong tidal forces between interacting galaxies could result in features like plumes , shells , rings , tidal tails , and bridges .
they also proposed that such strong collisions between galaxies would lead to orbital decay and eventual merging . in 1977 , toomre identified a series of galaxies that he believed represented galaxies at different stages of merging ( `` the toomre sequence '' ) and proposed that the end product of such merging could be an elliptical galaxy .
this hypothesis came to be known as the `` merger hypothesis . ''.
Please generate the next two sentences of the article | hibbard & van gorkom ( 1996 ) presented h-@xmath1 , r - band , and 21 cm observations of several galaxy systems from the toomre sequence and showed that these galaxies most likely do form an evolutionary chain .
three stages in the merging sequence were identified : ( i ) the early stage , in which the disks are well separated and only marginally disrupted , ( ii ) the intermediate stage , which exhibits distinct nuclei embedded in luminous material , and ( iii ) the late stage , in which tidal appendages are seen to emerge from a single nucleus . the purpose of this study is to better understand and interpret the evolutionary sequence as described by hibbard & van gorkom ( 1996 ) . |
4,132 | Suppose that you have an abstract for a scientific paper: continuing the project described by @xcite , we collected times of superhump maxima for 102 su uma - type dwarf novae observed mainly during the 20142015 season and characterized these objects .
our project has greatly improved the statistics of the distribution of orbital periods , which is a good approximation of the distribution of cataclysmic variables at the terminal evolutionary stage , and confirmed the presence of a period minimum at a period of 0.053 d and a period spike just above this period .
the number density monotonically decreased toward the longer period and there was no strong indication of a period gap .
we detected possible negative superhumps in z cha .
it is possible that normal outbursts are also suppressed by the presence of a disk tilt in this system .
there was no indication of enhanced orbital humps just preceding the superoutburst , and this result favors the thermal - tidal disk instability as the origin of superoutbursts .
we detected superhumpsin three am cvn - type dwarf novae .
our observations and recent other detections suggest that 8% of objects showing dwarf nova - type outbursts are am cvn - type objects .
am cvn - type objects and ei psc - type object may be more abundant than previously recognized . ot j213806 , a wz sge - type object , exhibited a remarkably different feature between the 2010 and 2014 superoutbursts .
although the 2014 superoutburst was much fainter the plateau phase was shorter than the 2010 one , the course of the rebrightening phase was similar .
this object indicates that the @xmath0 diagrams of superhumps can be indeed variable at least in wz sge - type objects .
four deeply eclipsing su uma - type dwarf novae ( asassn-13cx , asassn-14ag , asassn-15bu , nsv 4618 ) were identified .
we studied long - term trends in supercycles in mm hya and cy uma and found systematic variations of supercycles of @xmath120% . .
And you have already written the first three sentences of the full article: cataclysmic variables ( cvs ) are close binary systems transferring matter from a low - mass dwarf secondary to a white dwarf .
the transferred matter forms an accretion disk . thermal instability od the disk caused by partial ionization of hydrogen results outbursts in dwarf novae ( dne ) , a subclass of cvs .
tidal instability of the disk caused by the 3:1 resonance with the orbiting secondary is considered to develop an eccentric ( or flexing ) disk in su uma - type dwarf novae , a subclass of dne ..
Please generate the next two sentences of the article | this eccentric disk is responsible for superhumps , which have periods a few percent longer than the orbital period [ see e.g. @xcite ; @xcite ; @xcite ] .
the enhanced mass accretion by tidal instability causes long - lasting superoutbursts [ thermal tidal instability ( tti ) model : @xcite ; @xcite ] . |
4,133 | Suppose that you have an abstract for a scientific paper: we follow our general model in ref . @xcite and analyze the formation of retinotopic projections for the biologically relevant situation of _ spherical _ geometries . to this end
we elaborate both a linear and a nonlinear synergetic analysis which results in order parameter equations for the dynamics of connection weights between two spherical cell sheets .
we show that these equations of evolution provide stable stationary solutions which correspond to retinotopic modes
. a further analysis of higher modes furnishes proof that our model describes the emergence of a perfect one - to - one retinotopy between two spheres . .
And you have already written the first three sentences of the full article: an essential precondition for a correct operation of the nervous system consists in well - ordered neural connections between different cell sheets .
an example , which has been explored both experimentally and theoretically in detail , is the formation of ordered projections between retina and tectum , a part of the brain which plays an important role in processing optical information @xcite . at an initial stage of ontogenesis , retinal ganglion cells have random synaptic contacts with the tectum . in the adult animal , however , a so - called _ retinotopic _ projection is realized : neighboring cells of the retina project onto neighboring cells of the tectum . a detailed analytical treatment of hussler and von der malsburg described these ontogenetic processes in terms of self - organization @xcite .
in that work retina and tectum were treated as one - dimensional discrete cell arrays ..
Please generate the next two sentences of the article | the dynamics of the connection weights between retina and tectum were assumed to be governed by the so - called hussler equations . in ref . @xcite we generalized these equations of evolution to _ continuous _ manifolds of _ arbitrary geometry _ and _ dimension_. furthermore , we performed an extensive synergetic analysis @xcite near the instability of stationary uniform connection weights between retina and tectum .
the resulting generic order parameter equations served as a starting point for analyzing retinotopic projections between euclidean manifolds in ref . |
4,134 | Suppose that you have an abstract for a scientific paper: there have been two distinct formalisms of thermodynamics of information : one is the measurement - feedback formalism , which concerns bipartite systems with measurement and feedback processes , and the other is the information reservoir formalism , which considers bit sequences as a thermodynamic fuel . in this paper , we derive a second - law - like inequality by applying the measurement - feedback formalism to information reservoirs , which provides a stronger bound of extractable work than any other known inequality in the same setup . in addition , we demonstrate that the mandal - jarzynski model , which is a prominent model of the information reservoir formalism , is equivalent to a model obtained by the contraction of a bipartite system with autonomous measurement and feedback .
our results provide a unified view on the measurement - feedback and the information - reservoir formalisms . // .
And you have already written the first three sentences of the full article: evaluating the amount of work extraction from reservoirs is an important issue in thermodynamics and nonequilibrium statistical mechanics . here , we focus on the work extraction by using information , where two distinct formalisms exist .
one formalism concerns the measurement - feedback processes between two systems : a celebrated example is maxwell s demon . in this case , the generalizations of the second law and the fluctuation theorem have been obtained by including the _ mutual information _
@xcite between the system and the controller ( demon ) @xcite , and it has been applied to biochemical sensing @xcite ..
Please generate the next two sentences of the article | we call this avenue of research as the measurement - feedback ( mf ) formalism . the other formalism concerns the work extraction from bit sequences called _ information reservoirs _ , where the shannon entropy of a long bit sequence is consumed to extract work ( see also fig .
[ f : f : mjrevisit](a ) ) . |
4,135 | Suppose that you have an abstract for a scientific paper: in this article we consider bayesian parameter inference associated to partially - observed stochastic processes that start from a set @xmath0 and are stopped or killed at the first hitting time of a known set @xmath1 .
such processes occur naturally within the context of a wide variety of applications .
the associated posterior distributions are highly complex and posterior parameter inference requires the use of advanced markov chain monte carlo ( mcmc ) techniques .
our approach uses a recently introduced simulation methodology , particle markov chain monte carlo ( pmcmc ) @xcite , where sequential monte carlo ( smc ) @xcite approximations are embedded within mcmc .
however , when the parameter of interest is fixed , standard smc algorithms are not always appropriate for many stopped processes . in @xcite the authors introduce smc approximations of multi - level feynman - kac formulae , which can lead to more efficient algorithms .
this is achieved by devising a sequence of nested sets from @xmath0 to @xmath1 and then perform the resampling step only when the samples of the process reach intermediate level sets in the sequence .
naturally , the choice of the intermediate level sets is critical to the performance of such a scheme . in this paper
, we demonstrate that multi - level smc algorithms can be used as a proposal in pmcmc .
in addition , we propose a flexible strategy that adapts the level sets for different parameter proposals .
our methodology is illustrated on the coalescent model with migration .
+ * key - words * : stopped processes , sequential monte carlo , markov chain monte carlo @xmath2department of statistics & applied probability , national university of singapore , singapore , 117546 , sg .
+ e-mail:`[email protected] ` + @xmath3department of electrical engineering , imperial college london , london , sw7 2az , uk .
+ e-mail:`[email protected] ` .
And you have already written the first three sentences of the full article: in this article we consider markov processes that are stopped when reaching the boundary of a given set @xmath1 .
these processes appear in a wide range of applications , such as population genetics @xcite , finance @xcite , neuroscience @xcite , physics @xcite and engineering @xcite .
the vast majority of the papers in the literature deal with fully observed stopped processes and assume the parameters of the model are known . in this paper.
Please generate the next two sentences of the article | we address problems when this is not the case .
in particular , bayesian inference for the model parameters is considered , when the stopped process is observed indirectly via data . |
4,136 | Suppose that you have an abstract for a scientific paper: we establish exponential mixing for the geodesic flow @xmath0 of an incomplete , negatively curved surface @xmath1 with cusp - like singularities of a prescribed order . as a consequence
, we obtain that the weil - petersson flows for the moduli spaces @xmath2 and @xmath3 are exponentially mixing , in sharp contrast to the flows for @xmath4 with @xmath5 , which fail to be rapidly mixing . in the proof
, we present a new method of analyzing invariant foliations for hyperbolic flows with singularities , based on changing the riemannian metric on the phase space @xmath6 and rescaling the flow @xmath7 . .
And you have already written the first three sentences of the full article: let @xmath1 be an oriented surface with finitely many punctures .
suppose that @xmath1 is endowed with a negatively curved riemannian metric and that in a neighborhood of each puncture the metric is asymptotically modeled " on a surface of revolution obtained by rotating the curve @xmath8 , for some @xmath9 , about the @xmath10-axis in @xmath11 ( where @xmath12 may depend on the puncture ) .
the results in this paper allow us to conclude that the geodesic flow on @xmath6 mixes exponentially fast . before stating the hypotheses precisely , we recall some facts about the metric on a surface @xmath13 of revolution for the function @xmath14 ..
Please generate the next two sentences of the article | this surface is negatively curved , incomplete and the curvature can be expressed as a function of the distance to the cusp point @xmath15 where @xmath16 .
denote by @xmath17 the induced riemannian path metric and @xmath18 the riemannian distance to the cusp : @xmath19 then for @xmath20 , the gaussian curvature on @xmath13 has the following asymptotic expansion in @xmath21 , as @xmath22 : @xmath23 our main theorem applies to any incomplete , negatively curved surface with singularities of this form . |
4,137 | Suppose that you have an abstract for a scientific paper: in 2005 , junhao shen introduced a new invariant , @xmath0 , of a diffuse von neumann algebra @xmath1 with a fixed faithful trace , and he used this invariant to give a unified approach to showing that large classes of @xmath2 factors @xmath3 are singly generated .
this paper focuses on properties of this invariant .
we relate @xmath4 to the number of self - adjoint generators of a @xmath2 factor @xmath3 : if @xmath5 , then @xmath3 is generated by @xmath6 self - adjoint operators , whereas if @xmath3 is generated by @xmath6 self - adjoint operators , then @xmath7 .
the invariant @xmath8 is well - behaved under amplification , satisfying @xmath9 for all @xmath10 .
in particular , if @xmath11 for any particular @xmath12 , then the free group factors are pairwise non - isomorphic and are not singly generated for sufficiently large values of @xmath13 .
estimates are given for forming free products and passing to finite index subfactors and the basic construction .
we also examine a version of the invariant @xmath14 defined only using self - adjoint operators ; this is proved to satisfy @xmath15 .
finally we give inequalities relating a quantity involved in the calculation of @xmath16 to the free - entropy dimension @xmath17 of a collection of generators for @xmath3 . .
And you have already written the first three sentences of the full article: an old problem in von neumann algebra theory is the question of whether each separable von neumann algebra @xmath1 is singly generated .
a single generator @xmath18 leads to two self - adjoint generators @xmath19 and any pair @xmath20 of self - adjoint generators yields a single generator @xmath21 .
thus the single generation problem has an equivalent formulation as the existence of two self - adjoint generators ..
Please generate the next two sentences of the article | earlier work in this area solved all cases except for the finite von neumann algebras , @xcite .
here there has been progress in special situations , @xcite , but a general solution is still unavailable . |
4,138 | Suppose that you have an abstract for a scientific paper: we show how the existence of a relation between the star formation rate and the gas density , i.e. the kennicutt - schmidt law , implies a continuous accretion of fresh gas from the environment into the discs of spiral galaxies .
we present a method to derive the gas infall rate in a galaxy disc as a function of time and radius , and we apply it to the disc of the milky way and 21 galaxies from the things sample . for the milky way , we found that the ratio between the past and current star formation rates is about @xmath0 , averaged over the disc , but it varies substantially with radius . in the other disc galaxies there is a clear dependency of this ratio with galaxy stellar mass and hubble type , with more constant star formation histories for small galaxies of later type .
the gas accretion rate follows very closely the sfr for every galaxy and it dominates the evolution of these systems .
the milky way has formed two thirds of its stars after @xmath1 , whilst the mass of cold gas in the disc has remained fairly constant with time . in general , all discs have accreted a significant fraction of their gas after @xmath1 .
accretion moves from the inner regions of the disc to the outer parts , and as a consequence star formation moves inside - out as well . at @xmath2
the peak of gas accretion in the galaxy is at about @xmath3 from the centre .
[ firstpage ] galaxy : evolution galaxies : star formation galaxies : ism galaxies : evolution .
And you have already written the first three sentences of the full article: star formation is the fundamental process that shapes galaxies into different classes .
although the majority of stars in the local universe are found in spheroidal systems , most of the star formation is contributed by disc galaxies of the later types ( beyond sb ) .
the key ingredient for star formation is cold ( _ star - forming _ ) gas , which is present almost exclusively in disc galaxies ..
Please generate the next two sentences of the article | however , the amount of cold gas currently available in galaxy discs appears rather scant .
@xcite estimated that disc galaxies have current star formation rates ranging from a few to about @xmath4 . |
4,139 | Suppose that you have an abstract for a scientific paper: the in - medium modification of nucleon - nucleon ( nn ) cross sections is investigated by means of particle production in heavy ion collisions ( hic ) at intermediate energies .
in particular , the density dependence of the _ inelastic _ cross sections considerably affects the pion and kaon yields and their rapidity distributions .
however , the @xmath0- and @xmath1-ratios depend only moderately on the in - medium behavior of the inelastic cross sections .
it turns out that particle ratios seem to be robust observables in determining the nuclear equation of state ( eos ) and , particularly , its isovector sector . .
And you have already written the first three sentences of the full article: the knowledge of the properties of highly compressed and heated hadronic matter is an important issue for the understanding of astrophysics such as the physical mechanism of supernovae explosions and the physics of neutron stars @xcite .
hic provide the unique opportunity to explore highly excited hadronic matter , i.e. the high density behavior of the nuclear eos , under controlled conditions ( high baryon energy densities and temperatures ) in the laboratory @xcite .
important observables have been the nucleon collective dynamics @xcite and the dynamics of produced particles such as pions and kaons @xcite.
Please generate the next two sentences of the article | . however , the reaction dynamics is a rather complex process which involves the nuclear mean field ( eos ) and binary @xmath2-body collisions . in the presence of the nuclear medium the treatment of binary collisions represents a non - trivial topic .
the nn cross sections for elastic and inelastic processes , which are the crucial physical parameters here , are experimentally accessible only for the free space and not for @xmath2-body scattering at finite baryon density . |
4,140 | Suppose that you have an abstract for a scientific paper: in the ads / cft correspondence , an @xmath0 d3-brane with electric flux in @xmath1 spacetime corresponds to a circular wilson loop in the symmetric representation or a multiply wound one in @xmath2 super yang - mills theory . in order to distinguish the symmetric loop and the multiply wound loop , one should see an exponentially small correction in large t hooft coupling .
we study semi - classically the disk open string attached to the d3-brane .
we obtain the exponent of the term and it agrees with the result of the matrix model calculation of the symmetric wilson loop .
[ cols=
" < " , ] however , what we really want to do is to take the limit @xmath3 with @xmath4 kept finite . in this case , @xmath5 and @xmath6 are in the same order in @xmath7 ( linear in @xmath7 ) .
therefore we can not ignore the term @xmath6 when searching the saddle point in large @xmath7 .
the function @xmath8 looks like figure [ vy ] ( b ) .
this function is not flat at all in the region @xmath9 .
thus the expression is not valid in this case .
we find the minimum at a certain point @xmath10 instead .
let us evaluate the integral by the point @xmath11 .
@xmath12 is the solution of the equation @xmath13 then eq .
is solved as @xmath14 here we add the argument to @xmath15 in order to remember that it depends on @xmath16 . as a result
, we can approximate the integral in the large @xmath7 limit as @xmath17=\exp[2n(\kappa\sqrt{1+\kappa^2}+\sinh^{-1}\kappa ) ] .
\label{mk}\end{aligned}\ ] ] this is the same result as in @xcite . for later convenience , we define the quantity @xmath18 as @xmath19 next , we turn to the calculation of @xmath20 . this expectation value is written as @xmath21+(k-1)y_1+y_2\right).\label{int2}\end{aligned}\ ] ] as the same way as above , let us define the effective potential @xmath22 by @xmath23\right ) .
\label{eff2}\end{aligned}\ ] ] then eq . is written as @xmath24 actually , in the large @xmath7 limit , eq . leads to the following expression of @xmath25 .
....
And you have already written the first three sentences of the full article: in this section , we will consider the disk open string whose boundary is attached to the @xmath0 d3-brane , and compute the disk open string amplitudes by using the semi - classical technique .
we concentrate on the exponent of the correction in the large @xmath33 limit .
we postpone the integral on the moduli space and the one - loop determinant to future works ..
Please generate the next two sentences of the article | we find that the exponent of the correction agree with the matrix model result .
actually , there are perturbative corrections to the expression . |
4,141 | Suppose that you have an abstract for a scientific paper: hr 4049 is a peculiar evolved binary which is surrounded by a circumbinary disk .
mid - infrared observations show that the disk is rich in molecular gas and radially extended . to study the properties of this disk , we re - analyzed a set of near - infrared observations at high spectral resolution obtained with gemini - phoenix .
these data cover absorption lines originating from the first overtone of co and from h@xmath0oin the 2.3 @xmath1 m region as well as more complex emission - absorption profiles from h@xmath0oand the fundamental mode of co near 4.6 @xmath1 m . by using an excitation diagram and from modeling the spectrum
, we find that most of the co overtone and h@xmath0oabsorption originates from hot gas ( @xmath2 k ) with high column densities , consistent with the mid - infrared data .
the strong emission in the wavelength range of the co fundamental furthermore suggests that there is a significant quantity of gas in the inner cavity of the disk .
in addition , there is a much colder component in the line of sight to the disk .
a detailed analysis of the overtone line profiles reveals variations in the line widths which are consistent with a radially extended disk in keplerian rotation with hotter gas closer to the central star .
we estimate the mass of the primary to be @xmath3 m@xmath4 and discuss the implications for its evolutionary status . .
And you have already written the first three sentences of the full article: is considered the prototype for a class of evolved binaries with peculiar properties .
the effective temperatures and luminosities of the members of this class suggest that they are in the post - asymptotic giant branch ( post - agb ) phase of their evolution , but their evolutionary path is thought to be severely affected by the presence of a close companion ( see * ? ? ? * for a review ) .
like the other members of its class , hr 4049 shows a significant infrared ( ir ) excess and a time - variable optical and ultraviolet ( uv ) deficit @xcite , which suggests the presence of a massive circumbinary disk ..
Please generate the next two sentences of the article | in addition , its photosphere shows a severe depletion in refractory elements , but it has roughly solar abundances in volatiles .
this unusual depletion pattern is generally attributed to the formation of dust ( incorporating refractory elements ) in a circumbinary disk , followed by the re - accretion of the depleted gas onto the star @xcite . |
4,142 | Suppose that you have an abstract for a scientific paper: we have carried out a comprehensive investigation of magnetic properties of lufe@xmath0o@xmath1 , using ac susceptibility , dc magnetization and specific heat .
a magnetic phase transition around @xmath2236 k was observed with dc magnetization and specific heat measurements , which is identified as a paramagnetic to ferrimagnetic transition based on the nonlinear susceptibility data . upon further cooling below this temperature
, we also observed highly relaxational magnetic behavior : the dc magnetization exhibits history and time dependence , and the real and imaginary part of the ac susceptibility shows large frequency dependence .
dynamic scaling of the ac susceptibility data suggests that this low temperature phase can be described as a reentrant spin glass phase .
we also discuss magnetic field dependence of the spin glass transition and aging , memory and rejuvenation effect below the glass transition temperature around 228 k. .
And you have already written the first three sentences of the full article: geometrical frustration plays an important role in determining ground states and phase transitions in magnetic systems .
a triangular lattice in two - dimension in particular is one of the simplest systems to study the effect of geometrical frustration .
lufe@xmath0o@xmath1 is a member of rfe@xmath0o@xmath1 family of compounds , where r can be y , ho , er , tm , yb , and lu . @xcite these materials all have hexagonal layered structure , in which fe ions form a triangular lattice within each bilayer ..
Please generate the next two sentences of the article | @xcite since the average charge valence of fe in this compound is + 2.5 , this system is expected to exhibit charge order behavior similar to fe@xmath3o@xmath1 @xcite or half doped manganites .
@xcite however , due to the geometrical frustration introduced by the triangular lattice , understanding charge order in this material is not straightforward . |
4,143 | Suppose that you have an abstract for a scientific paper: the high redshifts of the most distant known quasars , and the best estimates of their black hole masses , require that supermassive black holes ( smbhs ) must have formed very early in history .
several mechanisms for creating and growing these holes have been proposed . here
we present an evaluation of the timescales needed for various critical processes in order to discriminate between the proposed scenarios .
we find in particular that mergers alone are not able to grow the black holes at a sufficient rate .
accretion models offer a solution and we use accretion timescales to constrain the manner in which the black hole was first formed .
this analysis implies , but does not require , the action of some unconventional process . .
And you have already written the first three sentences of the full article: central supermassive black holes are a common feature to galaxies today , but which came first , the black hole or the galaxy ?
conventional thinking would suggest that the the first generation of stars evolved into black holes , which have subsequently settled to the centers of their host galaxies , merged , and accreted gas .
but this idea , in which central black holes form inside pre - existing galaxies , has recently earned some scrutiny ..
Please generate the next two sentences of the article | first , the discovery of increasingly high redshift quasars requires a surprisingly early formation of the black holes ( see , for example , @xcite and @xcite ) .
second , a large quasar sample shows no evidence of black holes growing in mass with decreasing redshift @xcite . |
4,144 | Suppose that you have an abstract for a scientific paper: we consider a toy model for glassy dynamics of colloidal suspensions : a single brownian particle diffusing among immobile obstacles .
if gaussian factorization of _ static _ density fluctuations is assumed , this model can be solved without factorization approximation for any _ dynamic _ correlation function .
the solution differs from that obtained from the ideal mode coupling theory ( mct ) .
the latter is equivalent to including only some , positive definite terms in an expression for the memory function .
an approximate re - summation of the complete expression suggests that , under the assumption of gaussian factorization of static fluctuations , mobile particle s motion is always diffusive .
in contrast , mct predicts that the mobile particle becomes localized at a high enough obstacle density .
we discuss the implications of these results for models for glassy dynamics . .
And you have already written the first three sentences of the full article: during the last decade considerable effort has been devoted to simulational and experimental verification of the mode coupling theory ( mct ) of glassy dynamics and the glass transition @xcite .
the consensus that emerged from this work is that mct describes in a satisfactory way `` weakly '' supercooled liquids ( _ i.e. _ it describes the first few decades of slowing down on approaching the glass transition ) . in particular , mct has been quite successful when applied to concentrated colloidal suspensions @xcite , the colloidal glass @xcite , and gelation @xcite transitions .
notably , less effort has been devoted to the foundations of the mode coupling theory ( see , however , refs ..
Please generate the next two sentences of the article | this is somewhat surprising in view of mct s several well - known problems .
the most important , fundamental problem is the uncontrolled nature of the basic mct approximation : factorization of a complicated _ time - dependent _ pair - density ( _ i.e. _ four - particle ) correlation function . |
4,145 | Suppose that you have an abstract for a scientific paper: we present an experimental study of electron transport in inversion layers of high - mobility si(001 ) samples with occupied excited subbands .
the second series of oscillations , observed in addition to the main series of shubnikov - de hass oscillations , is tentatively attributed to the occupation of a subband associated with the @xmath0 level . besides
, a strong negative magnetoresistance and nonlinear field dependence of the hall resistance accompany the novel oscillations at high carrier concentrations .
the heating of the 2d electron layers leads to suppression of the observed anomalies . , , , , and si mosfet , magnetoresistance , hall effect 73.40.qv , 73.50.jt .
And you have already written the first three sentences of the full article: silicon is an indirect gap semiconductor with six minima ( valleys ) in the conduction band . in the case of ( 001)-oriented wafers , the long axes of two of the fermi ellipsoids are perpendicular to the @xmath1 plane of a @xmath2 interface ( with @xmath3 ) , while the long axes of the other four have an in - plane orientation ( @xmath4 ) .
a quantum well is formed at the interface by applying a positive voltage @xmath5 to the gate , and the electron motion in @xmath6 direction is quantized .
the difference in @xmath7 causes a splitting of the energy spectrum of bound states into two independent ladders of levels : the twofold - degenerate ladder of eigenenergies @xmath8 and a fourfold - degenerate ladder @xmath9 . due to the higher effective mass in the @xmath6-direction , the lowest energy level in the potential.
Please generate the next two sentences of the article | well is @xmath10 .
the self - consistent calculations ( see e.g @xcite ) predicts that the excited levels @xmath0 and @xmath11 are very close on energy scale and become occupied ( cross the fermi energy @xmath12 ) at the carrier concentration @xmath13 . while @xmath14 increases linearly with @xmath5 , the fourfold - degenerate @xmath0 stays `` pinned '' to the fermi energy and @xmath15 is almost constant even for the highest possible gate voltages . in both cases |
4,146 | Suppose that you have an abstract for a scientific paper: in this paper we analyze the canonical forms into which any pure three - qubit state can be cast .
the minimal forms , i.e. the ones with the minimal number of product states built from local bases , are also presented and lead to a complete classification of pure three - qubit states . this classification is related to the values of the polynomial invariants under local unitary transformations by a one - to - one correspondence . .
And you have already written the first three sentences of the full article: non - local quantum correlations or entanglement between space - separated parties is one of the most fertile and thought - generating properties of quantum mechanics .
recently it has become a very useful resource for many of the applications in quantum information theory and this has led to a lot of work devoted to understanding how it can be quantified and manipulated .
bipartite pure state entanglement is almost completely understood , while many questions are still open for the mixed state case . for pure states ,.
Please generate the next two sentences of the article | the schmidt decomposition @xcite has proven to be a very useful tool , since it allows to write any pure state shared by two parties a and b in a canonical form , where all the information about the non - local properties of the state is contained in the positive schmidt coefficients .
the non - local properties of quantum states can be also specified by means of other quantities invariant under the action of local unitary transformations . |
4,147 | Suppose that you have an abstract for a scientific paper: we investigate the validity of the cosmological principle by constraining the cosmological parameters @xmath0 and @xmath1 through the celestial sphere .
our analyses are performed in a low - redshift regime in order to follow a model independent approach , using both union2.1 and jla type ia supernovae ( sne ) compilations .
we find that the preferred direction of the @xmath0 parameter in the sky is consistent with the bulk flow motion of our local universe in the union2.1 case , while the @xmath1 directional analysis seem to be anti - correlated with the @xmath0 for both data sets .
furthermore , we test the consistency of these results with monte carlo ( mc ) realisations , finding that the anisotropy on both parameters are significant within @xmath2 confidence level , albeit we find a significant correlation between the @xmath0 and @xmath1 mapping with the angular distribution of sne from the jla compilation .
therefore , we conclude that the detected anisotropies are either of local origin , or induced by the non - uniform celestial coverage of the sne data set . .
And you have already written the first three sentences of the full article: the cosmological principle ( cp ) is one the most fundamental hypothesis upon which the concordance model based . in this work ,
we discuss the validity of the cosmological isotropy with different compilations of type ia supernovae ( sne ) , namely the union2.1 @xcite ) and jla data sets @xcite , using a hemispherical comparison method , hence determining whether the cosmological isotropy actually holds in large angular scales , and whether such hypothesis is not only a mathematical simplification , but a valid assumption .
we test the isotropy of the universe expansion by mapping the @xmath0 and @xmath1 parameters through the celestial sphere , so that an opposite hemisphere comparison is performed following ref ..
Please generate the next two sentences of the article | ( see also ref . ) .
each pair of these hemispheres is well defined by the healpix pixelization scheme @xcite , such that we fit @xmath0 and @xmath1 by minimising the following quantity @xmath3 where the set @xmath4 contains the observational information of the sne data , i.e. , redshift , distance moduli and associated uncertainty of the _ i - th _ object , respectively , where @xmath5 is the distance modulus given by a specific cosmological model according to @xmath6 } + 42.38 - 5\log_{10}(h ) \;,\ ] ] where @xmath7 , @xmath8 , and @xmath9 is the adimensional luminosity distance , whose arguments are the redshift @xmath10 , in addition to the set of cosmological parameters @xmath11 which describe the underlying cosmological model , @xmath9 is given by a cosmographic expansion up to second order , where @xmath12 . ] . |
4,148 | Suppose that you have an abstract for a scientific paper: we follow the sinking of two massive black holes in a spherical stellar system where the black holes become bound under the influence of dynamical friction .
once bound , the binary hardens by three - body encounters with surrounding stars .
we find that the binary wanders inside the core , providing an enhanced supply of reaction partners for the hardening .
the binary evolves into a highly eccentric orbit leading to coalescence well beyond a hubble time .
these are the first results from a hybrid `` self consistent field '' ( scf ) and direct aarseth @xmath0-body integrator ( nbody6 ) , which combines the advantages of the direct force calculation with the efficiency of the field method . the code is designed for use on parallel architectures and is therefore applicable to collisional @xmath0-body integrations with extraordinarily large particle numbers ( @xmath1 ) .
this creates the possibility of simulating the dynamics of both globular clusters with realistic collisional relaxation and stellar systems surrounding supermassive black holes in galactic nuclei . .
And you have already written the first three sentences of the full article: currently the standard picture of galaxy formation involves the collapse of baryonic matter in hierarchically clustering dark matter halos and the subsequent building of big galaxies from small ones via merging processes e.g. , @xcite .
while recent cosmological simulations can adequately reproduce many global properties of galaxies and their correlations , the details are still very much dependent on the gas physics and stellar feedback involved ( see e.g. , @xcite ) . additionally , most , if not all , galaxies harbor supermassive black holes in their center @xcite .
correlations have been recently detected between black hole masses , galaxy masses , and central velocity dispersions in galaxies @xcite ..
Please generate the next two sentences of the article | these correlations are strong evidence that black holes in galactic nuclei are linked to the dynamical history of their host galaxies . @xcite and @xcite
demonstrate how this is consistent with the framework of semi - analytic models that follow the formation and evolution of galaxies in a cold dark matter - dominated universe . |
4,149 | Suppose that you have an abstract for a scientific paper: we study the effect of globalization on the korean market , one of the emerging markets .
some characteristics of the korean market are different from those of the mature market according to the latest market data , and this is due to the influence of foreign markets or investors .
we concentrate on the market network structures over the past two decades with knowledge of the history of the market , and determine the globalization effect and market integration as a function of time . .
And you have already written the first three sentences of the full article: ` the world to seoul , seoul to the world . '
this was the slogan of the 1988 seoul olympics games , and is also the slogan of the korean stock market .
the globalization means that foreign traders have an influence on the korean market and its synchronization with world markets ..
Please generate the next two sentences of the article | interdisciplinary study has received much attention , with considerable interest in applying physics to economics and finances @xcite . since
a financial market is a complex system , many researchers have developed network theory to analyze such systems . |
4,150 | Suppose that you have an abstract for a scientific paper: the fact that fast oscillating homogeneous scalar fields behave as perfect fluids in average and their intrinsic isotropy have made these models very fruitful in cosmology . in this work
we will analyse the perturbations dynamics in these theories assuming general power law potentials @xmath0 . at leading order in the wavenumber expansion , a simple expression for the effective sound speed of perturbations
is obtained @xmath1 with @xmath2 the effective equation of state .
we also obtain the first order correction in @xmath3 , when the wavenumber @xmath4 of the perturbations is much smaller than the background oscillation frequency , @xmath5 .
for the standard massive case we have also analysed general anharmonic contributions to the effective sound speed .
these results are reached through a perturbed version of the generalized virial theorem and also studying the exact system both in the super - hubble limit , deriving the natural ansatz for @xmath6 ; and for sub - hubble modes , exploiting floquet s theorem . .
And you have already written the first three sentences of the full article: rapidly evolving coherent scalar fields have been widely studied in cosmology .
their dynamics is not only important during the reheating epoch after inflation , but they can also support periods of accelerated expansion in both the early universe @xcite or at late times @xcite . concerning the dark matter problem , non - thermal candidates like the axion @xcite or other massive scalar @xcite or pseudoscalar fields @xcite also fall in this class .
these models can be interpreted as bose - einstein condensates , where the scalar particles occupy the lowest quantum state of the potential @xcite . finally , the possibility of ultra - light scalar fields as dark matter candidates has been explored in different works @xcite by tuning appropriately the potential and initial conditions @xcite ..
Please generate the next two sentences of the article | the general analysis of a homogeneous oscillating scalar field in an expanding universe was performed by turner in @xcite . for a power - law potential @xmath0 , the rapid scalar oscillations around the minimum of such a potential behave as a perfect fluid with an effective equation of state @xmath7 .
his results can be recovered by means of a generalization of the virial theorem @xcite . |
4,151 | Suppose that you have an abstract for a scientific paper: in this paper we consider instability of nuclear matter which takes place when the frequencies of the collective excitations turn to zero . we investigate collective excitations with pion quantum numbers @xmath0 .
we study the dependence of zero - frequency solutions of the pion dispersion equation on the value of the spin - isospin quasiparticle interaction @xmath1 .
the solutions of the pion dispersion equation describe the different types of the excitations in the matter , @xmath2 . at the critical density @xmath3 one of solutions of
the definite type turns to zero : @xmath4=0 . when @xmath5 , the excitations @xmath6 become amplified .
it is shown that there is such a transitional " value of @xmath7 that for @xmath8 the zero - frequency solutions belong to the type @xmath9 while for @xmath10 they pertain to the type @xmath11 .
the solutions of the type @xmath9 correspond to instability to small density fluctuations of the nuclear matter at @xmath12 . on the other hand , @xmath11 is responsible for the pion condensation " at @xmath13 . for the stable nuclear matter
the branches of solutions @xmath14 and @xmath15 are located on the unphysical sheets of the complex plane of frequency . .
And you have already written the first three sentences of the full article: in this paper we investigate the excitations of nuclear matter with the pion quantum numbers . our analysis is based on studies the in - medium pion dispersion equation .
interactions of pions with baryons in nuclear matter is included in framework of migdal model @xcite .
solutions of the pion dispersion equation in this model were considered on the physical sheet of the complex plane of pion frequency @xmath16 ..
Please generate the next two sentences of the article | we expand this analysis to the unphysical sheets of the riemann surfaces .
we have included first the unphysical sheets to the analysis in our earlier papers @xcite . in @xcite |
4,152 | Suppose that you have an abstract for a scientific paper: fourier microscopy is becoming an increasingly important tool for the analysis of optical nanostructures and quantum emitters .
however , achieving quantitative fourier space measurements requires a thorough understanding of the impact of aberrations introduced by optical microscopes , which have been optimized for conventional real - space imaging . here , we present a detailed framework for analyzing the performance of microscope objectives for several common fourier imaging configurations . to this end , we model objectives from nikon , olympus , and zeiss using parameters that were inferred from patent literature and confirmed , where possible , by physical disassembly .
we then examine the aberrations most relevant to fourier microscopy , including the alignment tolerances of apodization factors for different objective classes , the effect of magnification on the modulation transfer function , and vignetting - induced reductions of the effective numerical aperture for wide - field measurements .
based on this analysis , we identify an optimal objective class and imaging configuration for fourier microscopy .
in addition , as a resource for future studies , the zemax files for the objectives and setups used in this analysis have been made publicly available . .
And you have already written the first three sentences of the full article: since the work of lieb _ et al .
_ @xcite , fourier microscopy has become an increasingly important experimental technique for nano - optics .
it is now commonly used to study quantum emitters @xcite , optical nanostructures @xcite , and the interactions of these two systems @xcite ..
Please generate the next two sentences of the article | for example , fourier microscopy has been used to characterize the orientation of single molecules @xcite and luminescent excitons in layered materials @xcite , the radiation pattern and directivity of optical antennas @xcite , and the multipolar origin of quantum transitions @xcite .
these fourier microscopy studies all share a common goal , namely to measure quantitative information about the angular spectrum radiated by a microscopic sample . |
4,153 | Suppose that you have an abstract for a scientific paper: the thermodynamic parameters of the superconducting state in calcium under the pressure at @xmath0 gpa have been calculated within the framework of the eliashberg approach .
it has been shown that the value of the coulomb pseudopotential is high ( @xmath1 ) and the critical temperature ( @xmath2 k ) should be determined from the modified allen - dynes formula .
in addition , it has been found that the basic dimensionless ratios of the thermodynamic parameters significantly diverge from the bcs predictions , and take the following values : ( i ) the zero temperature energy gap to the critical temperature ( @xmath3 ) is equal to 4.01 .
( ii ) the ratio @xmath4 equals @xmath5 , where @xmath6 and @xmath7 denote the specific heats for the superconducting and normal state , respectively . (
iii ) the quantity @xmath8 , where @xmath9 indicates the thermodynamic critical field .
finally , it has been proven that the electron effective mass is large and takes the maximum of @xmath10 at @xmath11 .
# 1([#1 ) ] # 1[#1 ] * keywords : * ca - superconductor , high - pressure effects , thermodynamic properties . .
And you have already written the first three sentences of the full article: under the influence of the high pressure , the elemental calcium undergoes a series of structural phase transitions . in particular , one can distinguish seven phases in the range of pressure ( @xmath12 ) from @xmath13 to @xmath14 gpa @xcite , @xcite , @xcite ( please see figure ( a ) for the details ) .
the two first phases , namely ca - i and ca - ii , have been classified as a fcc and bcc structures , respectively @xcite , @xcite .
the third phase ( ca - iii ) has been primarily linked with the sc structure , however the recent reports suggest other assignments ..
Please generate the next two sentences of the article | on the basis of the theoretical studies , teweldeberhan _ et al .
_ proposed the _ |
4,154 | Suppose that you have an abstract for a scientific paper: we present an analysis of the deepest pure - uv observations with the highest angular resolution ever performed , a set of 12 exposures with the hst wfpc2 and f160bw filter obtained in parallel observing mode , which cover @xmath012 square arcminutes in the lmc , north of the bar and in the `` general field '' regime of the lmc .
the 341 independent measurements of 198 objects represent an accumulated exposure of @xmath12 10@xmath2 sec and reveal stars as faint as m@xmath322 mag .
the observations show that @xmath02/3 of the uv emission from the lmc is emitted by our hst - detected uv stars in the field , _
i.e. , not _ in clusters or associations .
we identified optical counterparts in the roe / nrl photometric catalog for @xmath0 1/3 of the objects .
the results are used to discuss the nature of these uv sources , to estimate the diffuse uv emission from the lmc as a prototype of dwarf galaxies , and to evaluate the contamination by field stars of uv observations of globular and open clusters in the lmc .
we find that the projected density of uv stars in the general field of the lmc is a few times higher than in the galactic disk close to the sun .
combining our data with observations by uit allows us to define the stellar uv luminosity function from m@xmath4=8 to 18 mag , and to confirm that the field regions in the lmc have been forming stars at a steady rate during the last 1 gyr , with an imf close to the salpeter law . #
1#2#3#4#5#6#7 to#2 ' '' '' .
And you have already written the first three sentences of the full article: the large magellanic cloud ( lmc ) is the nearest galaxy to the milky way ( with the exception of a merging dwarf galaxy ) , one in which individual stars can be distinguished and studied fairly easily with instruments of the highest angular resolution such as the hubble space telescope ( hst ) .
the lmc is different from the milky way ( mw ) in that it shows more intense star formation ( sf ) , at least when compared with the solar neighborhood , _
i.e. , _ the mw region within @xmath02 kpc of the sun where the interstellar extinction is reasonably small and individual stars can be easily studied in the visible region of the spectrum ..
Please generate the next two sentences of the article | the difference in sf , coupled with the much smaller size of the lmc compared with the mw , implies that this is a dwarf irregular or a tidally truncated small spiral , in which the sf processes are probably different from those in the mw .
feitzinger ( 1987 ) argued that the lmc is a good example of a galaxy in which the sf proceeds primarily via the stochastic self - propagating sf mechanism ( sspsf : gerola & seiden 1978 ) , whereas the conventional view ( _ e.g. , _ kaufman 1979 ) is that the sf in the mw is driven mainly by spiral density waves . |
4,155 | Suppose that you have an abstract for a scientific paper: we review some recent progresses on the study of ultracold fermi gases with synthetic spin - orbit coupling . in particular , we focus on the pairing superfluidity in these systems at zero temperature .
recent studies have shown that different forms of spin - orbit coupling in various spatial dimensions can lead to a wealth of novel pairing superfluidity .
a common theme of these variations is the emergence of new pairing mechanisms which are direct results of spin - orbit - coupling - modified single - particle dispersion spectra . as different configurations
can give rise to single - particle dispersion spectra with drastic differences in symmetry , spin dependence and low - energy density of states , spin - orbit coupling is potentially a powerful tool of quantum control , which , when combined with other available control schemes in ultracold atomic gases , will enable us to engineer novel states of matter . .
And you have already written the first three sentences of the full article: the recent experimental realization of synthetic gauge field in ultracold atomics gases has greatly extended the horizon of quantum simulation in these systems @xcite .
a particularly important case is the implementation of synthetic spin - orbit coupling ( soc ) , a non - abelian gauge field , in these systems , where the internal degrees of freedom of the atoms are coupled to the atomic center - of - mass motional degrees of freedom @xcite . in condensed - matter materials
, soc plays a key role in many interesting phenomena , such as the quantum spin hall effects , topological insulators , and topological superconductors @xcite . although the form of the synthetic soc currently realized in cold atoms differs crucially from those in condensed - matter systems , there exist various theoretical proposals on realizing synthetic soc which can induce topologically nontrivial phases @xcite ..
Please generate the next two sentences of the article | thus , the hope of simulating the various topological phases , the topological superfluid state in particular , in the highly controllable environment of an ultracold atomic gas stimulated intensive theoretical studies on spin - orbit coupled fermi gases @xcite .
furthermore , recent studies suggest that other exotic superfluid phases and novel phenomena can be engineered with carefully designed configurations @xcite . as such , soc has a great potential of becoming a powerful tool of quantum control in ultracold atomic gases . in this review , |
4,156 | Suppose that you have an abstract for a scientific paper: the scattering of kinks and low - frequency breathers of the nonlinear sine - gordon ( sg ) equation on a spatially localized @xmath0-symmetric perturbation ( defect ) with a balanced gain and loss is investigated numerically .
it is demonstrated that if a kink passes the defect , it always restores its initial momentum and energy and the only effect of the interaction with the defect is a phase shift of the kink .
a kink approaching the defect from the gain side always passes , while in the opposite case it must have sufficiently large initial momentum to pass through the defect instead of being trapped in the loss region . the kink phase shift and critical velocity
are calculated with the use of the collective variable method .
kink - kink ( kink - antikink ) collisions at the defect are also briefly considered , showing how their pairwise repulsive ( respectively , attractive ) interaction can modify the collisional outcome of a single kink within the pair with the defect . for the breather
, the result of its interaction with the defect strongly depends on the breather parameters ( velocity , frequency and initial phase ) and on the defect parameters .
the breather can gain some energy from the defect and as a result potentially even split into a kink - antikink pair or it can lose a part of its energy .
interestingly , the breather translational mode is very weakly affected by the dissipative perturbation , so that a breather penetrates more easily through the defect when it comes from the lossy side , than a kink . in all studied soliton - defect interactions the energy loss to radiation of small - amplitude extended waves is negligible . .
And you have already written the first three sentences of the full article: the last 15 years have seen a significant series of developments in quantum theory , stemming from the realization by bender and co - authors that a class of non - hermitian hamiltonians possess real spectra under the parity - time ( @xmath0 ) symmetry condition , where parity - time means spatial reflection and time reversal , @xmath1 and @xmath2 @xcite .
this mathematical discovery has initiated numerous studies of open systems with balanced gain and loss even though the generality of this construction is under discussion @xcite .
experimental setups have been offered to create @xmath0-symmetric physical systems in optics @xcite , electronic circuits @xcite , as well as in mechanical systems @xcite . in a number of theoretical studies.
Please generate the next two sentences of the article | it has been demonstrated that @xmath0-symmetric systems often demonstrate unusual and counterintuitive properties .
these include , among others , unconventional beam refraction @xcite , bragg scattering @xcite , symmetry - breaking transitions @xcite and associated ghost states @xcite , a loss - induced optical transparency @xcite , conical diffraction @xcite , a new type of fano resonance @xcite , chaos @xcite , nonlocal boundary effects @xcite , optical switches @xcite and diodes @xcite , phase sensitivity of light dynamics @xcite , and the possibility of linear and nonlinear wave amplification and filtering @xcite . |
4,157 | Suppose that you have an abstract for a scientific paper: we present updated results of the cp - pacs calculation of the light hadron spectrum in @xmath0 full qcd .
simulations are made with an rg - improved gauge action and a tadpole - improved clover quark action for sea quark masses corresponding to @xmath10.6 and the lattice spacing @xmath20.09 fm .
a comparison of the @xmath0 qcd spectrum with new quenched results , obtained with the same improved action , shows clearly the existence of sea quark effects in vector meson masses .
results for light quark masses are also presented . .
And you have already written the first three sentences of the full article: understanding sea quark effects in the light hadron spectrum is an important issue , sharpened by the recent finding of a systematic deviation of the quenched spectrum from experiment@xcite . to this end , we have been pursuing @xmath0 qcd simulations using an rg - improved gauge action and a tadpole - improved clover quark action @xcite , to be called * rc * simulations in this article .
the parameters of these simulations are listed in table [ tab : param ] .
the statistics at @xmath3 have been increased since lattice98 , and the runs at @xmath4 are new ..
Please generate the next two sentences of the article | in addition we have carried out quenched simulations with the same improved action , referred to as * qrc * , for a direct comparison of the full and quenched spectrum .
the @xmath5 values of these runs , given in table [ tab : param ] , are chosen so that the lattice spacing fixed by the string tension matches that of full qcd for each value of sea quark mass at @xmath6 and 2.1 . |
4,158 | Suppose that you have an abstract for a scientific paper: we introduce _ orbitopes _ as the convex hulls of @xmath0-matrices that are lexicographically maximal subject to a group acting on the columns .
special cases are packing and partitioning orbitopes , which arise from restrictions to matrices with at most or exactly one @xmath1-entry in each row , respectively .
the goal of investigating these polytopes is to gain insight into ways of breaking certain symmetries in integer programs by adding constraints , e.g. , for a well - known formulation of the graph coloring problem .
we provide a thorough polyhedral investigation of packing and partitioning orbitopes for the cases in which the group acting on the columns is the cyclic group or the symmetric group .
our main results are complete linear inequality descriptions of these polytopes by facet - defining inequalities . for the cyclic group case ,
the descriptions turn out to be totally unimodular , while for the symmetric group case , both the description and the proof are more involved .
the associated separation problems can be solved in linear time . .
And you have already written the first three sentences of the full article: symmetries are ubiquitous in discrete mathematics and geometry .
they are often responsible for the tractability of algorithmic problems and for the beauty of both the investigated structures and the developed methods .
it is common knowledge , however , that the presence of symmetries in integer programs may severely harm the ability to solve them ..
Please generate the next two sentences of the article | the reasons for this are twofold .
first , the use of branch - and - bound methods usually leads to an unnecessarily large search tree , because equivalent solutions are found again and again . |
4,159 | Suppose that you have an abstract for a scientific paper: in this work controlled phase shift gates are implemented on a qaudrupolar system , by using non - adiabatic geometric phases .
a general procedure is given , for implementing controlled phase shift gates in an n level system .
the utility of such controlled phase shift gates , is demonstrated here by implementing 3-qubit deutsch - jozsa algorithm on a 7/2 quadrupolar nucleus oriented in a liquid crystal matrix . . .
And you have already written the first three sentences of the full article: the use of quantum systems for information processing was first introduced by benioff @xcite . in 1985
deutsch described quantum computers which exploit the superposition of multi particle states , thereby achieving massive parallelism @xcite .
researchers have also studied the possibility of solving certain types of problems more efficiently than can be done on conventional computers @xcite ..
Please generate the next two sentences of the article | these theoretical possibilities have generated significant interest for experimental realization of quantum computers @xcite .
several techniques are being exploited for quantum computing and quantum information processing , including nuclear magnetic resonance ( nmr ) @xcite . |
4,160 | Suppose that you have an abstract for a scientific paper: whether gamma - ray bursts are highly beamed or not is a very difficult but important problem that we are confronted with .
some theorists suggest that beaming effect usually leads to a sharp break in the afterglow light curve during the ultra - relativistic phase , with the breaking point determined by @xmath0 , where @xmath1 is the lorentz factor of the blastwave and @xmath2 is the initial half opening angle of the ejecta , but numerical studies tend to reject the suggestion .
we note that previous studies are uniformly based on dynamics that is not proper for non - relativistic blastwaves . here
we investigate the problem in more detail , paying special attention to the transition from the ultra - relativistic phase to the non - relativistic phase .
due to some crucial refinements in the dynamics , we can follow the overall evolution of a realistic jet till its velocity is as small as @xmath3 .
we find no obvious break in the optical light curve during the relativistic phase itself .
however , an obvious break does appear at the transition from the relativistic phase to the newtonian phase if the physical parameters involved are properly assumed . generally speaking ,
the newtonian phase is characterized by a sharp decay of optical afterglows , with the power law timing index @xmath4 2.1 .
this is due to the quick lateral expansion at this stage .
the quick decay of optical afterglows from grb 970228 , 980326 , and 980519 , and the breaks in the optical light curves of grb 990123 and 990510 may indicate the presence of highly collimated @xmath1-ray burst ejecta . .
And you have already written the first three sentences of the full article: till the end of august 1999 , x - ray , optical , and radio afterglows have been observed from about 16 , 11 , and 5 gamma - ray bursts ( grbs ) respectively ( costa et al .
1997 ; bloom et al .
1998 ; groot et al ..
Please generate the next two sentences of the article | 1998 ; kulkarni et al . 1998 , 1999 ; harrison et al . 1999 ; stanek et al . 1999 ; fruchter et al .
1999 ; galama et al . |
4,161 | Suppose that you have an abstract for a scientific paper: we study the geodesic motion of test particles in the space - time of non - compact boson stars .
these objects are made of a self - interacting scalar field and depending on the scalar field s mass can be as dense as neutron stars or even black holes .
in contrast to the former these objects do not contain a well - defined surface , while in contrast to the latter the space - time of boson stars is globally regular , can however only be given numerically .
hence , the geodesic equation also has to be studied numerically .
we discuss the possible orbits for massive and massless test particles and classify them according to the particle s energy and angular momentum .
the space - time of a boson star approaches the schwarzschild space - time asymptotically , however deviates strongly from it close to the center of the star . as a consequence ,
we find additional bound orbits of massive test particles close to the center of the star that are not present in the schwarzschild case .
our results can be used to make predictions about extreme - mass - ratio inspirals ( emris ) and we hence compare our results to recent observational data of the stars orbiting _
sagittarius a@xmath0 _ - the radiosource at the center of our own galaxy . .
And you have already written the first three sentences of the full article: solitons play an important rle in many areas of physics . as classical solutions of non - linear field theories
, they are localized structures with finite energy , which are globally regular . in general
, one can distinguish between topological and non - topological solitons ..
Please generate the next two sentences of the article | while topological solitons @xcite possess a conserved quantity , the topological charge , that stems ( in most cases ) from the spontaneous symmetry breaking of the theory , non - topological solitons @xcite have a conserved noether charge that results from a symmetry of the lagrangian .
the standard example of non - topological solitons are @xmath1-balls @xcite , which are solutions of theories with self - interacting complex scalar fields . |
4,162 | Suppose that you have an abstract for a scientific paper: to better understand wolf - rayet stars as progenitors of gamma - ray bursts , an understanding of the effect metallicity has on wolf - rayet mass loss is needed . using simple analytic models , we study the @xmath0 relation of a wn star and compare the results to similar models .
we find that @xmath1 roughly follows a power law in @xmath2 with index 0.88 from @xmath3 and appears to flatten by @xmath4 . .
And you have already written the first three sentences of the full article: as a complement to detailed simulations of wolf - rayet ( wr ) winds ( e.g. , * ? ? ?
* ; * ? ? ?
* ) , we have developed a set of simple analytic models using diffusive cak - type line driving with frequency redistribution @xcite . in this paper.
Please generate the next two sentences of the article | , we apply these models to a preliminary study of the @xmath0 relation for wr stars , which is important for the study of wr stars as progenitors of long - duration gamma - ray bursts @xcite .
the details of the basic model are discussed in @xcite . |
4,163 | Suppose that you have an abstract for a scientific paper: we show that empirical risk minimization procedures and regularized empirical risk minimization procedures satisfy nonexact oracle inequalities in an unbounded framework , under the assumption that the class has a subexponential envelope function .
the main novelty , in addition to the boundedness assumption free setup , is that those inequalities can yield fast rates even in situations in which exact oracle inequalities only hold with slower rates .
we apply these results to show that procedures based on @xmath0 and nuclear norms regularization functions satisfy oracle inequalities with a residual term that decreases like @xmath1 for every @xmath2-loss functions ( ) , while only assuming that the tail behavior of the input and output variables are well behaved .
in particular , no rip type of assumption or `` incoherence condition '' are needed to obtain fast residual terms in those setups .
we also apply these results to the problems of convex aggregation and model selection . . .
And you have already written the first three sentences of the full article: let @xmath3 be a space endowed with a probability measure @xmath4 , and let @xmath5 and @xmath6 be @xmath7 independent random variables with values in @xmath3 , distributed according to @xmath4 ; from the statistical point of view , @xmath8 is the set of given data .
let @xmath9 be a loss function which associates a real number @xmath10 to any real - valued measurable function @xmath11 defined on @xmath3 and any point @xmath12 .
denote by @xmath13 the loss function @xmath14 associated with @xmath11 and set @xmath15 to be the associated risk ..
Please generate the next two sentences of the article | the risk of any statistic @xmath16 is defined by @xmath17 $ ] .
let @xmath18 be a class ( usually called the _ model _ ) of real - valued measurable functions defined on @xmath3 . |
4,164 | Suppose that you have an abstract for a scientific paper: we present randomized algorithms to compute the sumset ( minkowski sum ) of two integer sets , and to multiply two univariate integer polynomials given by sparse representations .
our algorithm for sumset has cost softly linear in the combined size of the inputs and output .
this is used as part of our sparse multiplication algorithm , whose cost is softly linear in the combined size of the inputs , output , and the sumset of the supports of the inputs . as a subroutine , we present a new method for computing the coefficients of a sparse polynomial , given a set containing its support .
our multiplication algorithm extends to multivariate laurent polynomials over finite fields and rational numbers .
our techniques are based on sparse interpolation algorithms and results from analytic number theory . .
And you have already written the first three sentences of the full article: sparse polynomials are a fundamental object in computer algebra .
computer algebra programs including maple , mathematica , sage , and singular use a sparse representation by default for multivariate polynomials , and there has been considerable recent work on how to efficiently store and compute with sparse polynomials @xcite .
however , despite the memory advantage of sparse polynomials , the alternative dense representation is still widely used for an obvious reason : speed ..
Please generate the next two sentences of the article | it is now classical @xcite that two degree-@xmath0 dense polynomials can be multiplied in softly linear time : @xmath1 ring operations , and even better in many cases @xcite . by contrast , two size-@xmath2 sparse polynomials require @xmath3 operations , and this excludes the potentially significant cost of exponent arithmetic .
much of the recent work on sparse arithmetic has focused on `` somewhat dense '' or structured cases , where the sparsity of the product is sub - quadratic @xcite . at the same time , sparse interpolation algorithms , which in the fastest case can learn an unknown @xmath2-sparse polynomial from @xmath4 evaluations , have gained renewed interest @xcite . |
4,165 | Suppose that you have an abstract for a scientific paper: we study the accelerated expansion of the universe through its consequences on a congruence of geodesics .
we make use of the raychaudhuri equation which describes the evolution of the expansion rate for a congruence of timelike or null geodesics . in particular , we focus on the space - time geometry contribution to this equation . by straightforward calculation from the metric of a robertson - walker cosmological model , it follows that in an accelerated expanding universe the space - time contribution to the raychaudhuri equation is positive for the fundamental congruence , favoring a non - focusing of the congruence of geodesics .
however , the accelerated expansion of the present universe does not imply a tendency of the fundamental congruence to diverge .
it is shown that this is in fact the case for certain congruences of timelike geodesics without vorticity .
therefore , the focusing of geodesics remains feasible in an accelerated expanding universe .
furthermore , a negative contribution to the raychaudhuri equation from space - time geometry which is usually interpreted as the manifestation of the attractive character of gravity is restored in an accelerated expanding robertson - walker space - time at high speeds . .
And you have already written the first three sentences of the full article: general relativity ( gr ) as a theory that describes the geometrical structure of space - time and its connection with the energy content of the universe has been highly successful in the last one hundred years .
gr is not only able to give explanation of some discrepancies that had been arisen with newtonian theory in the solar system , but also provides a satisfactory description of the cosmological evolution of the space - time .
however , gr is not able to account for the latest cosmological and astrophysical observations with standard matter sources . among these observations.
Please generate the next two sentences of the article | are the anomalous rotational velocities of objects near the edge of the galaxies , the dynamics of galaxies in clusters , formation of large scale structures or gravitational lensing of background objects by galaxy clusters , such as the bullet cluster . for the explanation of these observations ,
more matter than the standard one is required , the so - called dark matter ( dm ) which has an attractive gravitational character that decelerates the expansion of the universe . |
4,166 | Suppose that you have an abstract for a scientific paper: two of the major obstacles to achieve quantum computing ( qc ) are ( i ) scalability to many qubits and ( ii ) controlled connectivity between any selected qubits . using josephson charge qubits , here we propose an experimentally realizable method to efficiently solve these two central problems . since any two charge qubits can be effectively coupled by an experimentally accessible inductance ,
the proposed qc architecture is _
scalable_. in addition , we formulate an efficient and realizable qc scheme that requires _ only one _ ( instead of two or more ) two - bit operation to implement conditional gates . .
And you have already written the first three sentences of the full article: josephson - qubit devices @xcite are based on the charge and phase degrees of freedom .
the charge qubit is achieved in a cooper - pair box @xcite , where two dominant charge states are coupled through coherent cooper - pair tunneling @xcite . using cooper - pair tunneling in josephson charge devices @xcite and via spectroscopic measurements for the josephson phase device @xcite , it has been possible to experimentally observe energy - level splitting and related properties for state superpositions . in addition , using josephson charge devices prepared in a superposition of two charge states @xcite ,
coherent oscillations were observed ..
Please generate the next two sentences of the article | while operating at the degeneracy point , the charge - qubit states are highly coherent @xcite ( @xmath0 ) , with a decoherence time of @xmath1 ns . these important experimental results indicate that the josephson charge and phase devices are potentially useful for solid - state qubits in quantum information processing .
important open problems would now include implementing a _ two - bit coupling _ and then _ scaling up _ the architecture to many qubits . here , we propose a new quantum - computing ( qc ) scheme based on scalable charge - qubit structures . |
4,167 | Suppose that you have an abstract for a scientific paper: we study the persistent current and the drude weight of a system of spinless fermions , with repulsive interactions and a hopping impurity , on a mesoscopic ring pierced by a magnetic flux , using a density matrix renormalization group algorithm for complex fields .
both the luttinger liquid ( ll ) and the charge density wave ( cdw ) phases of the system are considered . under a jordan - wigner transformation ,
the system is equivalent to a spin-1/2 xxz chain with a weakened exchange coupling .
we find that the persistent current changes from an algebraic to an exponential decay with the system size , as the system crosses from the ll to the cdw phase with increasing interaction @xmath0 .
we also find that in the interacting system the persistent current is invariant under the impurity transformation @xmath1 , for large system sizes , where @xmath2 is the defect strength .
the persistent current exhibits a decay that is in agreement with the behavior obtained for the drude weight .
we find that in the ll phase the drude weight decreases algebraically with the number of lattice sites @xmath3 , due to the interplay of the electron interaction with the impurity , while in the cdw phase it decreases exponentially , defining a localization length which decreases with increasing interaction and impurity strength .
our results show that the impurity and the interactions always decrease the persistent current , and imply that the drude weight vanishes in the limit @xmath4 , in both phases .
pacs : 71.10.pm , 73.23.ra , 73.63.-b .
And you have already written the first three sentences of the full article: the experimental discovery of persistent currents in mesoscopic rings pierced by a magnetic flux,@xmath5 earlier proposed theoretically,@xmath6 has revealed interesting new effects .
the currents measured in metallic and semiconducting rings , either in a single ring or an array of many rings , generally exhibit an unexpectedly large amplitude , i.e. , larger by at least one order of magnitude , than predicted by theoretical studies of electron models with either disorder or electron - electron interaction treated perturbatively.@xmath7 it has been suggested that the interactions and their interplay with disorder are possibly responsible for the large currents observed , expecting that the effect of the interactions could counteract the disorder effect . however , no consensus has yet been reached on the role of the interactions . in order to gain theoretical insight , it is desirable to perform numerical calculations which allow to consider both interactions and disorder directly in systems with sizes varying from small to large .
analytical calculations usually involve approximations which mainly provide the leading behavior of the properties for large system sizes ..
Please generate the next two sentences of the article | persistent currents in mesoscopic rings strongly depend on the system size , since they emerge from the coherence of the electrons across the entire system .
hence , it is most important to study the size dependence of the current beyond leading order in microscopic models , for a complete understanding of the experimental results . |
4,168 | Suppose that you have an abstract for a scientific paper: our knowledge and ignorance concerning the geometry of quantum states are discussed . .
And you have already written the first three sentences of the full article: physical theories are usually created by accumulating some fragments of information which at the beginning do not allow to predict the final structures .
the classical mechanics was formulated by isaac newton in terms of mass , force , acceleration and the three dynamical laws .
it was not immediate to see the lagrangians , hamilton equations and the simplectic geometry behind ..
Please generate the next two sentences of the article | we can not guess the reaction of newton if he were informed that he was just describing the classical phase spaces defined by the simplectic manifolds quite similarly , max planck , niels bohr , louis de broglie , erwin schrdinger and werner heisenberg could not see from the very beginning that the physical facts which they described would be reduced by born s statistical interpretation to the hilbert space geometry ( as it seems , neither hilbert could predict that ) . yet , once accepted that the pure states of a quantum system can be represented by vectors of a complex linear space and the expectation values are just quadratic forms , the hilbert spaces entered irremediably into the quantum theories .
together appeared the `` density matrices '' as the mathematical tools representing either pure or mixed quantum ensembles . |
4,169 | Suppose that you have an abstract for a scientific paper: new mid - infrared period - luminosity ( pl ) relations are presented for rr lyr variables in the globular cluster m4 ( ngc 6121 ) .
accurate photometry was obtained for 37 rr lyr variables using observations from the infrared array camera onboard the spitzer space telescope .
the dispersion of m4 s pl relations is 0.056 , and the uncertainty in the slope is 0.11 mag .
additionally , we established calibrated pl relations at 3.6 and 4.5 using published hubble space telescope geometric parallaxes of five galactic rr lyr stars .
the resulting band - averaged distance modulus for m4 is @xmath0 .
the systematic uncertainty will be greatly reduced when parallaxes of more stars become available from the gaia mission .
optical and infrared period - color ( pc ) relations are also presented , and the lack of a mir pc relation suggests that rr lyr stars are not affected by co absorption in the 4.5 band . .
And you have already written the first three sentences of the full article: rr lyr variables are important tools in the investigation of many fundamental astrophysical problems
. they provide crucial constraints on the physical mechanisms driving radial oscillations and their interplay with stellar evolution @xcite .
furthermore , rr lyr stars offer the opportunity to study the morphology of the horizontal branch and the oosterhoff dichotomy @xcite ..
Please generate the next two sentences of the article | current empirical evidence indicates that the mean period of fundamental mode ( rrab or fu ) rr lyr stars in galactic globular clusters ( ggcs hereafter ) shows a dichotomous distribution at 0.55 ( ooi ) and 0.65 ( ooii ) days @xcite , where the latter group is more metal - poor .
there is also evidence that the dichotomy is the aftermath of the hysteresis mechanism suggested by @xcite , i.e. that the pulsation mode depends on the direction of the evolution inside the instability strip @xcite . @xcite |
4,170 | Suppose that you have an abstract for a scientific paper: in the paper phys . rev . * d83 * , 054008 ( 2011 ) we constructed the @xmath0 scattering amplitude @xmath1 with regular analytical properties in the @xmath2 complex plane , describing both experimental data and the results based on chiral expansion and roy equations .
now the results obtained during development of our work are presented .
we dwell on questions dealing with the low @xmath3 mixing , inelasticity description and the kaon loop model for @xmath4 reaction , and show a number of new fits .
in particular , we show that the minimization of the @xmath3 mixing results in the four - quark scenario for light scalars : the @xmath5(600 ) coupling with the @xmath6 channel is suppressed relatively to the coupling with the @xmath0 channel , and the @xmath7(980 ) coupling with the @xmath0 channel is suppressed relatively to the coupling with the @xmath6 channel .
the correct analytical properties of the @xmath0 scattering amplitude are reached with the help of rather complicated background function .
we also suggest much more simple background parameterization , practically preserving the resonance features , which is comfortable for experimental data analysis , but allows to describe the results based on chiral expansion and roy equations only on the real @xmath2 axis . .
And you have already written the first three sentences of the full article: study of light scalar resonances is one of the central problems of nonperturbative qcd , it is important for understanding the chiral symmetry realization way resulting from the confinement physics . in refs .
@xcite we described the high - statistical kloe data on the @xmath8 decay @xcite in the frame of the kaon loop model @xmath9 @xcite simultaneously with the data on the @xmath0 scattering and the @xmath10 reaction .
the description was carried out taking into account the chiral shielding of the @xmath11 meson @xcite and its mixing with the @xmath12 meson , the data yielded evidence in favor of the four - quark nature of the @xmath11 and @xmath12 mesons ..
Please generate the next two sentences of the article | at the same time it was calculated in ref .
@xcite the @xmath0 scattering amplitude in the @xmath2 complex plane , basing on chiral expansion , dispersion relations , and roy equations . in particular , the pole was obtained at @xmath13 , where @xmath14 which was assigned to the @xmath5 resonance . aiming the comparison of the results of refs . @xcite and @xcite , we built up the s - wave @xmath0 scattering amplitude @xmath1 with @xmath15 with correct analytical properties in the complex @xmath2 plane @xcite . |
4,171 | Suppose that you have an abstract for a scientific paper: we present results of spectral and timing analysis of the fast x - ray transient xte j1901 + 014 based on data of the rxte and integral observatories . with the integral / isgri
the source was detected at a significance level of 20@xmath0 with the persistent flux of @xmath12.7 mcrab in a 17 - 100 kev energy band in 2003 - 2004 ( during long observations of the sagittarius arm region ) .
we added the rxte / pca ( 3 - 20 kev ) data obtained in 1998 to the integral / isgri data to build the broadband spectrum of the source in a quiescent state .
it was found that the spectrum can be well approximated by a simple powerlaw with a photon index of @xmath12.15 . from timing analysis
we found short time scale aperiodic variations which can be connected with instabilities in the accretion flow .
[ 2001/04/25 1.1 ( pwd ) ] .
And you have already written the first three sentences of the full article: the fast x - ray transient source xte j1901 + 014 was discovered [ 4 ] by the all - sky monitor asm on board the rxte observatory during the powerful outburst on april 6 , 2002 lasted from 3 min to 3.15 hours and reached the peak flux @xmath10.9 crab in the 1.5 - 12 kev energy band ( fig.1 , right panel ) .
the source position was determined as ra = 19@xmath2 01@xmath3 [email protected] , dec = + 1 2415.7(j2000 ; 3uncertainty ) .
the analysis of the archival asm data [ 5 ] revealed a previous outburst from the same position on june 21 , 1997 ..
Please generate the next two sentences of the article | this outburst was longer than 6 min and shorter than 8 hr , with a peak flux of @xmath10.4 crab ( fig . 1 , left panel ) .
the obtained information about xte j1901 + 014 was not enough to make any confident conclusions about its nature , but it was noted that the time scale of this flare is similar to those of such events observed from the black hole binary v4641 sgr . in this report |
4,172 | Suppose that you have an abstract for a scientific paper: in this work we study the behaviour of wigner phase delay time for tunneling in the reflection mode .
our system consists of a circular loop connected to a single wire of semi - infinite length in the presence of aharonov - bohm flux .
we calculate the analytical expression for the saturated delay time .
this saturated delay time is independent of aharonov- bohm flux and the width of the opaque barrier thereby generalizing the hartman effect .
this effect implies superluminal group velocities as a consequence .
we also briefly discuss the concept called space collapse or space destroyer "
. 0.5 cm .
And you have already written the first three sentences of the full article: quantum tunneling is one of the most important phenomenon with wide range of applications in modern technology . in spite of its remarkable success in various applications , there still remains the fundamental question , namely , how much time does a particle take to traverse the barrier ?
( so called tunneling time problem ) .
this problem has been approached from many different viewpoints , but still there is a lack of consensus about the existence of simple expression for this time @xcite ..
Please generate the next two sentences of the article | this is due to the fact that there is no hermitian operator associated with this time .
the various time scales proposed in the literature are based on different operational definitions and physical interpretations . |
4,173 | Suppose that you have an abstract for a scientific paper: in this paper we study the symmetries of the dual taub - nut metrics . _
generic _ and _ non - generic _ symmetries of dual taub - nut metrics are investigated .
the existence of the runge - lenz type symmetry is analyzed for dual taub - nut metrics .
we find that in some cases the symmetries of the dual metrics are the same with the symmetries of taub - nut metric .
.3 in .3 in -1.5 cm 0.5 cm _ joint institute for nuclear research _
+ _ bogoliubov laboratory of theoretical physics _ , + _ 141 980 dubna , moscow region , russia _ + 0.8 cm 1 cm .
And you have already written the first three sentences of the full article: in a geometrical setting , symmetries are connected with isometries associated with killing vectors and , more generally , killing tensors on the configurations space of the system .
an example is the motion of a point particle in a space with isometries @xcite , which is a physicist s way of studying the geodesic structure of a manifold . in @xcite
such studies were extended to spinning space - times described by supersymmetric extensions of the geodesic motion , and in@xcite it was shown that this can give rise to interesting new types of supersymmetry as well ..
Please generate the next two sentences of the article | the geometric duality between a metric @xmath0 and its non - degenerate killing tensor @xmath1 was discussed in @xcite .
the relation was generalized to spinning spaces , but only at the expense of introducing torsion . |
4,174 | Suppose that you have an abstract for a scientific paper: we have searched for neutron - antineutron oscillations using the 5.56 fiducial kiloton - year exposure of the soudan 2 iron tracking calorimeter .
we require candidate @xmath0occurrences to have @xmath1 4 prongs ( tracks and showers ) and to have kinematics compatible with annihilation within a nucleus .
we observe five candidate events , with an estimated background from atmospheric neutrino and cosmic ray induced events of 4.5 @xmath2 1.2 events .
previous experiments with smaller exposures observed no candidates , with estimated background rates similar to this experiment .
we set a lifetime lower limit at 90% cl for the @xmath0oscillation time in iron : @xmath3 years .
the corresponding lower limit for oscillation of free neutrons is @xmath4 seconds .
pacs numbers : 11.30.fs , 12.20.fv , 12.60.jv , 14.20.dh 6.5 in 8.25 in 0.0 in 0.0 in .
And you have already written the first three sentences of the full article: an intriguing variation on the grand unification theme that nucleons are likely to be unstable is the proposal that neutrons can oscillate into antineutrons .
neutron - antineutron oscillations were first predicted in 1970 by v. a. kuzmin in a model intended as a realization of requirements given earlier by a.d .
sakharov for evolution of the universe to net baryon asymmetry ..
Please generate the next two sentences of the article | subsequently @xmath0oscillations emerged as a predicted reaction in certain grand unification theories @xcite .
more recently it has been shown that @xmath0oscillations can occur in a large class of supersymmetric @xmath5 models @xcite . |
4,175 | Suppose that you have an abstract for a scientific paper: many theoretical approaches find @xmath0-wave superconductivity in the prototypical one - band hubbard model for high - temperature superconductors . at strong - coupling ( @xmath1 , where @xmath2 is the on - site repulsion and @xmath3 the bandwidth ) pairing
is controlled by the exchange energy @xmath4 .
one may then surmise , ignoring retardation effects , that near - neighbor coulomb repulsion @xmath5 will destroy superconductivity when it becomes larger than @xmath6 , a condition that is easily satisfied in cuprates for example . using cellular dynamical mean - field theory with an exact diagonalization solver for the extended hubbard model ,
we show that pairing _ at strong coupling _ is preserved , even when @xmath7 , as long as @xmath8 .
while at weak coupling @xmath5 always reduces the spin fluctuations and hence @xmath0-wave pairing , at strong coupling , in the underdoped regime , the increase of @xmath9 caused by @xmath5 increases binding at low frequency while the pair - breaking effect of @xmath5 is pushed to high frequency .
these two effects compensate in the underdoped regime , in the presence of a pseudogap . while the pseudogap competes with superconductivity , the proximity to the mott transition that leads to the pseudogap , and retardation effects , protect @xmath0-wave superconductivity from @xmath5 . .
And you have already written the first three sentences of the full article: the existence of @xmath0-wave superconductivity in the one - band two - dimensional hubbard model has been established through a variety of theoretical methods at both weak @xcite and strong coupling @xcite , in other words for one - site interaction @xmath2
either much smaller or much larger than the bandwidth @xmath10 . generalizations of dynamical mean - field theory are particularly suited for the strong coupling limit , but they are also an excellent guide to the physics at weak to intermediate coupling .
@xcite , these calculations suggest that pairing is maximized at intermediate coupling , where the on - site interaction @xmath2 is of order the bandwidth @xmath3 ..
Please generate the next two sentences of the article | some non - perturbative calculations based on weak coupling ideas even agree at intermediate coupling @xcite with strong - coupling based approaches . in all these approaches , spin fluctuations with either an antiferromagnetic or a singlet character @xcite
have been argued to drive the pairing . |
4,176 | Suppose that you have an abstract for a scientific paper: simulations of magnetization dynamics in a multiscale environment enable rapid evaluation of the landau - lifshitz - gilbert equation in a mesoscopic sample with nanoscopic accuracy in areas where such accuracy is required .
we have developed a multiscale magnetization dynamics simulation approach that can be applied to large systems with spin structures that vary locally on small length scales . to implement this ,
the conventional micromagnetic simulation framework has been expanded to include a multiscale solving routine .
the software selectively simulates different regions of a ferromagnetic sample according to the spin structures located within in order to employ a suitable discretization and use either a micromagnetic or an atomistic model . to demonstrate the validity of the multiscale approach , we simulate the spin wave transmission across the regions simulated with the two different models and different discretizations .
we find that the interface between the regions is fully transparent for spin waves with frequency lower than a certain threshold set by the coarse scale micromagnetic model with no noticeable attenuation due to the interface between the models . as a comparison to exact analytical theory ,
we show that in a system with dzyaloshinskii - moriya interaction leading to spin spiral , the simulated multiscale result is in good quantitative agreement with the analytical calculation . .
And you have already written the first three sentences of the full article: to model magnetization dynamics , currently two paradigms are commonly used in the field : the micromagnetic model and the heisenberg spin model .
the micromagnetic model @xcite is ideal when simulating systems with linear dimensions of the order of a few nanometers or larger ; since it is a continuous model that is discretized for computational application , its reliability decreases dramatically when simulating magnetic structures exhibiting a large gradient that can not be resolved by the finite size cells . a textbook example for this scenario
is offered by bloch points @xcite ( see fig . [.
Please generate the next two sentences of the article | fig : bloch ] ) , domain walls and spin waves also belong to this category for particular values of the material parameters .
the heisenberg model @xcite is a discrete description , where with every atom in the lattice of the ferromagnet a magnetic moment is associated . since this is a discrete model , its capability to simulate any magnetic structure is not limited by computational artifacts originating from the discretization of a continuum model , which makes it distinct from micromagnetism . on the other hand |
4,177 | Suppose that you have an abstract for a scientific paper: we study the current - phase relation of a bose - einstein condensate flowing through a repulsive square barrier by solving analytically the one dimensional gross - pitaevskii equation .
the barrier height and width fix the current - phase relation @xmath0 , which tends to @xmath1 for weak barriers and to the josephson sinusoidal relation @xmath2 for strong barriers . between these two limits ,
the current - phase relation depends on the barrier width .
in particular , for wide enough barriers , we observe two families of multivalued current - phase relations .
diagrams belonging to the first family , already known in the literature , can have two different positive values of the current at the same phase difference .
the second family , new to our knowledge , can instead allow for three different positive currents still corresponding to the same phase difference .
finally , we show that the multivalued behavior arises from the competition between hydrodynamic and nonlinear - dispersive components of the flow , the latter due to the presence of a soliton inside the barrier region . .
And you have already written the first three sentences of the full article: the current - phase relation characterizes the flow of a superfluid / superconductor through a weak link @xcite .
the latter is a constricted flow configuration that can be realized in different ways : i ) apertures in impenetrable walls mostly for helium , ii ) sandwich or bridge structures for superconductors , and iii ) penetrable barriers created by laser beams for ultracold dilute gases .
much information about such systems can be extracted from the current - phase relation , which , given a fluid , depends only on the link properties ..
Please generate the next two sentences of the article | for instance , with @xmath3he , the transition from the usual ac josephson effect to a quantized phase slippage regime @xcite corresponds to the switching from a sine - like current phase relation to a multivalued one @xcite .
a weak link configuration can be modelled very generally upon taking a portion of a superfluid / superconductor to have `` different conduction properties '' with respect to the rest of the system . |
4,178 | Suppose that you have an abstract for a scientific paper: we apply a utility based method to obtain the value of a finite time investment opportunity when the underlying real asset is not perfectly correlated to a traded financial asset . using a discrete time algorithm to calculate the indifference price for this type of real option , we present numerical examples for the corresponding investment thresholds , in particular highlighting their dependence with respect to correlation and risk aversion .
* key words : * real options , incomplete markets , exponential utility , optimal exercise policy . .
And you have already written the first three sentences of the full article: most of the standard literature in real options is based on one or both of the following unrealistic assumptions : ( 1 ) that the time horizon for the problem at hand is infinite and ( 2 ) that the real asset under consideration is perfectly correlated to a traded financial asset .
the _ infinite maturity _
hypothesis helps to reduce the dimensionality of the problem by removing its dependence on time , therefore concentrating on stationary solutions only , while the _ spanning asset _ hypothesis allows the introduction of useful replication arguments developed for derivative pricing in complete markets ..
Please generate the next two sentences of the article | together they led to the development of a coherent and intuitive approach for investment under uncertainty , well
represented for instance in dixit and pindyck ( 1994 ) , where the decisions to start , abandon , reactive and mothball a given project were reduced to the solution of systems of linear equations . since then , several authors have dropped the artifice of an infinite maturity time , therefore resourcing to numerical methods for dealing with the non - stationary valuation problem . |
4,179 | Suppose that you have an abstract for a scientific paper: the agn - host co - evolution issue is investigated here by focusing on the evolution of the [ ] @xmath0 emission - line profile . in order to simultaneously measure both [ ] line profile and circumnuclear stellar population in individual spectrum ,
a large sample of narrow emission - line galaxies is selected from the mpa / jhu sdss dr7 catalog . by requiring
that 1 ) the [ ] line signal - to - noise ratio is larger than 30 , 2 ) the [ ] line width is larger than the instrumental resolution by a factor of 2 , our sample finally contains 2,333 seyfert galaxies / liners ( agns ) , 793 transition galaxies , and 190 starforming galaxies . in additional to the commonly used profile parameters ( i.e. , line centroid , relative velocity shift and velocity dispersion ) , two dimensionless shape parameters , skewness and kurtosis , are used to quantify the line shape deviation from a pure gaussian function .
we show that the transition galaxies are systematically associated with narrower line widths and weaker [ ] broad wings than the agns , which implies that the kinematics of the emission - line gas is different in the two kinds of objects . by combining the measured host properties and line shape parameters , we find that the agns with stronger blue asymmetries tend to be associated with younger stellar populations
. however , the similar trend is not identified in the transition galaxies .
the failure is likely resulted from a selection effect in which the transition galaxies are systematically associated with younger stellar populations than the agns .
the evolutionary significance revealed here suggests that both nlr kinematics and outflow feedback in agns co - evolve with their host galaxies . .
And you have already written the first three sentences of the full article: the emission from narrow - line region ( nlr ) of active galactic nucleus ( agn ) is an important tool to study the relation between the activity of the central supermassive black hole ( smbh ) and the growth of its host galaxy in which the smbh resides , both because the nlr emission is mainly resulted from the illumination by the central agn and because the nlr kinematics is believed to be mainly dominated by the gravity of the bulge ( see review in wilson & heckman 1985 and references therein , whittle 1992a , b ; nelson & white 1996 ) . the gravity dominated kinematics motivates a number of previous studies to demonstrate that the line width of the agn s strong [ ] @xmath15007 emission line can be used as a proxy for the stellar velocity dispersion of the bugle ( e.g. , nelson & white 1996 ; nelson 2000 ; boroson 2003 ; komossa & xu 2007 ) . basing upon the tight @xmath2 relationship ( e.g. , tremaine et al . 2002 ; ferrarese & merritt 2000 ; magorrian et al .
1998 ; gebhardt et al .
2000 ; haring & rix 2004 ) , the proxy therefore allows one to easily estimate @xmath3 in a large sample of agns ( e.g. , grupe & mathur 2004 ; wang & lu 2001 ; komossa & xu 2007 ) ..
Please generate the next two sentences of the article | it is well known for a long time that the line profiles of the [ ] doublelets show a blue asymmetry with an extended blue wing and a sharp red falloff in a large fraction of agns ( e.g. , heckman et al .
1981 ; whittle 1985 ; wilson & heckman 1985 ; grupe et al 1999 ; tadhunter et al . |
4,180 | Suppose that you have an abstract for a scientific paper: collapse models explain the absence of quantum superpositions at the macroscopic scale , while giving practically the same predictions as quantum mechanics for microscopic systems . the continuous spontaneous localization ( csl ) model is the most refined and studied among collapse models .
a well - known problem of this model , and of similar ones , is the steady and unlimited increase of the energy induced by the collapse noise . here
we present the dissipative version of the csl model , which guarantees a finite energy during the entire system s evolution , thus making a crucial step toward a realistic energy - conserving collapse model .
this is achieved by introducing a non - linear stochastic modification of the schrdinger equation , which represents the action of a dissipative finite - temperature collapse noise .
the possibility to introduce dissipation within collapse models in a consistent way will have relevant impact on the experimental investigations of the csl model , and therefore also on the testability of the quantum superposition principle .
the superposition principle lies at the core of quantum mechanics .
the last years have experienced a huge progress in the theoretical and experimental investigation aimed at preparing and observing quantum superpositions of large systems @xcite .
such a progress promises a crucial insight into a question which was born with quantum mechanics itself @xcite .
can quantum mechanics be applied at all scales , including the macroscopic ones , or is there an intrinsic limit , above which its description of reality is not appropriate ?
collapse models @xcite show explicitly how the second point of view can be assumed without the need to introduce an ad - hoc separation between the microscopic and the macroscopic world within the theory @xcite . through a non - linear stochastic modification of the schrdinger equation ,
collapse models predict a behavior of microscopic systems which follows almost strictly that of standard quantum....
And you have already written the first three sentences of the full article: using the language of non - relativistic quantum field theory , the csl model is formulated in terms of a stochastic differential equation in the fock space associated with the system @xcite .
given different types of particles , where the type @xmath2 has mass @xmath3 , the mass - proportional csl model @xcite is defined by @xmath4 { \mathrm{d}}w_t({\bf y } ) \right .
\nonumber \\ & & \left.- \frac{\gamma}{2 m^2_0 } \int { \mathrm{d}}{\bf y } [ \hat{m}({\bf y})-\langle m({\bf y } ) \rangle_t ] ^2 { \mathrm{d}}t \right ] { \vert \varphi_t \rangle},\end{aligned}\ ] ] where @xmath5 is the standard quantum hamiltonian , @xmath6 , @xmath7 is a reference mass ( usually the mass of a nucleon ) and @xmath8 is a smeared mass density operator : @xmath9 here , @xmath10 and @xmath11 are , respectively , the creation and the annihilation operator of a particle of type @xmath2 in the point @xmath12 , while @xmath13 is an ensemble of independent wiener processes , one for each point in space ..
Please generate the next two sentences of the article | the model is characterized by two parameters : @xmath14 , which sets the strength of the collapse process , and @xmath15 , which determines the threshold above which spatial superpositions are suppressed .
the choice of the numerical values for these parameters is of course ultimately dictated by the agreement with the experimental data ; the originally proposed values are @xcite @xmath16 and @xmath17 . |
4,181 | Suppose that you have an abstract for a scientific paper: we consider the reconstruction of optical parameters in a domain of interest from photoacoustic data .
photoacoustic tomography ( pat ) radiates high frequency electromagnetic waves into the domain and measures acoustic signals emitted by the resulting thermal expansion .
acoustic signals are then used to construct the deposited thermal energy map .
the latter depends on the constitutive optical parameters in a nontrivial manner . in this paper , we develop and use an inverse transport theory with internal measurements to extract information on the optical coefficients from knowledge of the deposited thermal energy map .
we consider the multi - measurement setting in which many electromagnetic radiation patterns are used to probe the domain of interest . by developing an expansion of the measurement operator into singular components ,
we show that the spatial variations of the intrinsic attenuation and the scattering coefficients may be reconstructed .
we also reconstruct coefficients describing anisotropic scattering of photons , such as the anisotropy coefficient @xmath0 in a henyey - greenstein phase function model . finally , we derive stability estimates for the reconstructions
. * keywords . * photoacoustics , optoacoustics , transport equation , inverse problems , stability estimates , internal measurements . .
And you have already written the first three sentences of the full article: photoacoustic imaging is a recent medical imaging technique combining the large contrast between healthy and unhealthy tissues of their optical parameters with the high spatial resolution of acoustic ( ultrasonic ) waves .
electromagnetic radiation , sent through a domain of interest , generates some heating and a resulting thermal expansion of the underlying tissues .
the mechanical displacement of the tissues generates acoustic waves , which then propagate through the medium and are recorded by an array of detectors ( ultrasound transducers ) ..
Please generate the next two sentences of the article | the photoacoustic effect is now being actively investigated for its promising applications in medical imaging .
we refer the reader to e.g. @xcite for recent reviews on the practical and theoretical aspects of the method . in an idealized setting revisited below |
4,182 | Suppose that you have an abstract for a scientific paper: exploring the use of single - mode fibers ( smfs ) in high precision doppler spectrometers has become increasingly attractive since the advent of diffraction - limited adaptive optics systems on large - aperture telescopes .
spectrometers fed with these fibers can be made significantly smaller than typical seeing - limited instruments , greatly reducing cost and overall complexity .
importantly , classical mode interference and speckle issues associated with multi - mode fibers , also known as modal noise , are mitigated when using smfs , which also provide perfect radial and azimuthal image scrambling .
however , these fibers do support multiple polarization modes , an issue that is generally ignored for larger - core fibers given the large number of propagation modes . since diffraction gratings used in most high resolution astronomical instruments have dispersive properties that are sensitive to incident polarization changes , any birefringence variations in the fiber can cause variations in the efficiency profile , degrading illumination stability . here
we present a cautionary note outlining how the polarization properties of smfs can affect the radial velocity measurement precision of high resolution spectrographs .
this work is immediately relevant to the rapidly expanding field of diffraction - limited , extreme precision rv spectrographs that are currently being designed and built by a number of groups . .
And you have already written the first three sentences of the full article: detection of terrestrial - mass extra - solar planets ( exoplanets ) requires extremely stable and precise instruments . in the strive to reach extreme levels of doppler precision
, a number of previously uncharacterized instrumental effects will begin to dominate instrument error budgets .
dedicated doppler radial velocity ( rv ) instruments must be able to measure shifts in stellar spectra at precisions approaching 10 cm s@xmath0 in order to detect true earth twins orbiting nearby stars . in the pursuit of reaching this bold precision goal ,.
Please generate the next two sentences of the article | a number of previously uncharacterized instrument noise sources must be studied and mitigated at unprecedented levels . in the past decade , much attention has been paid to maximizing detection sensitivity by using optical fibers to deliver light from the telescope to the spectrograph .
typical multi - mode fibers ( mmfs ) used in current generation seeing - limited doppler instruments have the convenient ability to scramble light , producing an output illumination that is significantly , though not perfectly , decoupled from the incident flux distribution @xcite . |
4,183 | Suppose that you have an abstract for a scientific paper: while it is usually known that the mean value of a single observable is enough to detect entanglement or its distillability , the counterpart of such an approach in the case of quatum privacy has been missing .
here we develop the concept of a privacy witness , i.e. a single observable that may detect presence of the secure key even in the case of bound entanglement .
then we develop the notion of secret key estimation based on few observables and discuss the witness decomposition into local measurements .
the surprising property of the witness is that with the help of a low number of product mesurements involved it may still report the key values that are _ strictly above _
distillable entanglement of the state . for an exemplary four - qubit state studied in a recent experiment [ k. dobek _ et al .
_ , phys .
rev .
lett . * 106 * , 030501 ( 2011 ) ] this means @xmath0 pauli operator product measurements versus @xmath1 needed to carry out the complete quantum state tomography .
the present approach may be viewed as a paradigm for the general program of experimentally friendly detection and estimation of task - dedicated quantum entanglement . .
And you have already written the first three sentences of the full article: entanglement based cryptography @xcite , equivalent formally to the bb84 scheme @xcite , is the one that uses the power of quantum entanglement monogamy obeyed by a maximally entangled pure quantum state . if the state is noisy then in some cases it is possible to run an entanglement distillation process @xcite which may be interpreted as quantum privacy amplification @xcite .
since the final output is maximally entangled , it may be used directly for secret key generation .
the efficiency of this procedure is quantified with distillable entanglement @xmath2 , which defines how many singlet states can be obtained in the asymptotic regime per one input . still it was known that certain states which can not be prepared by local operations and classical communication ( locc ) are not distillable , exhibiting the phenomenon of bound entanglement @xcite . for a long time.
Please generate the next two sentences of the article | bound entanglement was believed to be useless for cryptography , but several years ago it was shown @xcite , that at least some bound entangled states may be useful in quantum cryptography .
this is one extreme instance of the general fact that the amount of distillable secure key @xmath3 may exceed the amount of distillable singlets @xmath4 . |
4,184 | Suppose that you have an abstract for a scientific paper: this paper develops maximum score estimation of preference parameters in the binary choice model under uncertainty in which the decision rule is affected by conditional expectations .
the preference parameters are estimated in two stages : we estimate conditional expectations nonparametrically in the first stage and then the preference parameters in the second stage based on manski ( 1975,1985 ) s maximum score estimator using the choice data and first stage estimates . the paper establishes consistency and derives rate of convergence of the two - stage maximum score estimator .
moreover , the paper also provides sufficient conditions under which the two - stage estimator is asymptotically equivalent in distribution to the corresponding single - stage estimator that assumes the first stage input is known .
these results are of independent interest for maximum score estimation with nonparametrically generated regressors .
the paper also presents some monte carlo simulation results for finite - sample behavior of the two - stage estimator .
* keywords : * _ discrete choice , maximum score estimation , generated regressor , preference parameters , m - estimation , cube root asymptotics _ * jel codes : * c12 , c13 , c14 . .
And you have already written the first three sentences of the full article: this paper develops a semiparametric two - stage estimator of preference parameters in the binary choice model where the agent s decision rule is affected by conditional expectations of outcomes which are uncertain at the choice - making stage and the preference shocks are nonparametrically distributed with unknown form of heteroskedasticity .
the pioneering papers of manski(1991,1993 ) established nonparametric identification of agents expectations in the discrete choice model under uncertainty when the expectations are fulfilled and conditioned only on observable variables . utilizing this result , ahn and manski(1993 ) proposed a two - stage estimator for a binary choice model under uncertainty where agent s utility was linear in parameter and the unobserved preference shock had a known distribution .
specifically , they estimated the agent s expectations nonparametrically in the first stage and then the preference parameters in the second stage by maximum likelihood estimation using the choice data and the expectation estimates ..
Please generate the next two sentences of the article | ahn(1995,1997 ) extended the two - step approach further . on one hand , ahn ( 1995 ) considered nonparametric estimation of conditional choice probabilities in the second stage . on the other hand , ahn ( 1997 ) retained the linear index structure of the ahn - manski model but estimated the preference parameters in the second stage using average derivative method hence allowing for unknown distribution of the unobservable . in principle , alternative approaches accounting for nonparametric unobserved preference shock can also be applied in the second step estimation of this framework .
well known methods include cosslett ( 1983 ) , powell et al.(1989 ) , ichimura ( 1993 ) , klein and spady ( 1993 ) , and coppejans ( 2001 ) , among many others . |
4,185 | Suppose that you have an abstract for a scientific paper: in the first paper of this series it was found that the @xmath0-spin @xmath1 holons , spin @xmath1 spinons , and @xmath2 pseudoparticles whose occupancy configurations describe the energy eigenstates of the one - dimensional hubbard model emerge from the electron - rotated - electron unitary transformation .
an important breakthrough is that the theory provides relevant information about the relationship of the original electrons to these quantum objects . in this second paper
we discuss and clarify how such a relation can be used in a program for evaluation of finite - energy few - electron spectral functions . as a first step , here we characterize the dominant holon and spinon microscopic physical processes that originate more than 99% of the few - electron spectral weight .
these dominant processes are related to exact selection rules for the values of the number of holons and spinons generated or annihilated by application onto a ground state of rotated - electron operators .
while our theory also describes the higher - order microscopic processes associated with the remaining less than 1% few - electron spectral weight , the clarification and study of the above dominant processes is valuable and useful for the further understanding and description of the few - electron spectral properties observed in real low - dimensional materials .
moreover , in this paper generalize the concepts of a lower hubbard band and upper hubbard bands to all values of on - site coulombian repulsion . .
And you have already written the first three sentences of the full article: in this paper and its two companion papers @xcite the relation of the electrons of the one - dimensional ( 1d ) hubbard model to the quantum objects whose occupancy configurations describe its energy eigenstates is investigated for the whole hilbert space .
the study of such a non - perturbative relation is a necessary step for the description of the finite - energy few - electron spectral properties of the many - electron quantum problem .
the study of the one - dimensional ( 1d ) hubbard model @xcite for interacting electrons is of general importance because the understanding of correlated systems and of their finite - energy excitations is still far from complete ..
Please generate the next two sentences of the article | the problem of the 1d hubbard model in the limit of large and infinite on - site coulomb repulsion was previously studied in the literature by many authors @xcite .
our studies of the model for finite values of the on - site repulsion @xmath3 are motivated by the anomalous one - electron and two - electron spectral properties observed in metallic and insulating phases of quasi - one - dimensional materials , which can not be described by the usual fermi - liquid theory @xcite . |
4,186 | Suppose that you have an abstract for a scientific paper: we investigate the change in ionizing photons in galaxies between @xmath0 using the f2 field of the shels complete galaxy redshift survey .
we show , for the first time , that while the [ ] /h@xmath1 and [ ] / [ ] ratios rise , the [ ] /h@xmath2 and [ ] /h@xmath2 ratios fall significantly over the @xmath3 redshift range for stellar masses between @xmath4 . the [ ] /h@xmath1 and [ ] / [ ] ratios continue to rise across the full @xmath0 redshift range for stellar masses between @xmath5 .
we conclusively rule out agn contamination , a changing ism pressure , and a change in the hardness of the euv radiation field as the cause of the change in the line ratios between @xmath3 .
we find that the ionization parameter rises significantly with redshift ( by 0.1 to 0.25 dex depending on the stellar mass of the sample ) .
we show that the ionization parameter is strongly correlated with the fraction of young - to - old stars , as traced by the h@xmath1 equivalent width .
we discuss the implications of this result on higher redshift studies , and we consider the implications on the use of standard optical metallicity diagnostics at high redshift . .
And you have already written the first three sentences of the full article: an understanding of the conditions under which stars formed at all epochs is critical in constraining theoretical models of galaxy evolution .
recent observations of @xmath6 star - forming galaxies suggest that the ism state and/or the hardness of the euv radiation field was more extreme in the past than in the present day .
galaxies at high redshift display larger line ratios ( [ ] /h@xmath1 and/or [ ] /h@xmath2 ) than local galaxies ( e.g. , * ? ? ?.
Please generate the next two sentences of the article | * ; * ? ? ?
* ; * ? ? ? |
4,187 | Suppose that you have an abstract for a scientific paper: clustered regularly interspaced short palindromic repeats ( crispr ) , linked with crispr associated ( cas ) genes , play a profound role in the interactions between phage and their bacterial hosts .
it is now well understood that crispr - cas systems can confer adaptive immunity against bacteriophage infections .
however , the possibility of failure of crispr immunity may lead to a productive infection by the phage ( cell lysis ) or lysogeny .
recently , crispr - cas genes have been implicated in changes to group behaviour , including biofilm formation , of the bacterium _ pseudomonas aeruginosa _ when lysogenized . for lysogens with a crispr system
, another recent experimental study suggests that bacteriophage re - infection of previously lysogenized bacteria may lead to cell death .
thus crispr immunity can have complex effects on phage - host - lysogen interactions , particularly in a biofilm . in this contribution
, we develop and analyse a series of models to elucidate and disentangle these interactions . from a therapeutic standpoint ,
crispr immunity increases biofilm resistance to phage therapy .
our models predict that lysogens may be able to displace crispr - immune bacteria in a biofilm , and thus suggest strategies to eliminate phage - resistant biofilms .
+ + keywords : bacteria , bacteriophage , biofilm , crispr - cas system , lysogens .
1.5 1.5 [ cols="^,<,^",options="header " , ] 1.5 in figure [ fig : fig2 ] , the population dynamics of each of these models are illustrated for the same baseline parameter values and initial conditions .
the simulations are run over long times to illustrate stable equilibrium states , and in each case the numerical results were validated by comparison with the analytical expressions .
we plot both population densities and time on a log axis , such that initial transients are visible . in the first model ,
the baseline scenario produces a stable lysogenic equilibrium ( without crispr ) , in which the phage....
And you have already written the first three sentences of the full article: we explore the dynamics of lysogenic phage in a bacterial biofilm , for bacterial hosts both with and without crispr immunity .
classical models of phage - bacteria interactions have previously demonstrated that lysogeny can promote the stable co - existence of bacteria and phage @xcite . in agreement with these findings ,
model 1 explores the baseline conditions under which lysogeny exists in a biofilm , and provides conditions for the stability of a lysogenic equilibrium ..
Please generate the next two sentences of the article | the second and third models demonstrate the powerful effect of the crispr - cas system in comparison with the non - crispr bacterial population in the first model .
the second model predicts that at realistic parameter values , only prophage - free crispr - immune bacteria stably survive in a bacterial biofilm . in rare cases , |
4,188 | Suppose that you have an abstract for a scientific paper: gravitational - wave observations of compact binaries have the potential to uncover the distribution of masses and spins of black holes and neutron stars in the universe .
the binary components physical parameters can be inferred from their effect on the phasing of the gravitational - wave signal , but a partial degeneracy between the components mass ratio and their spins limits our ability to measure the individual component masses . at the typical signal amplitudes expected by the advanced laser interferometer gravitational - wave observatory ( signal - to - noise ratios between 10 and 20 ) ,
we show that it will in many cases be difficult to distinguish whether the components are neutron stars or black holes .
we identify when the masses of the binary components could be unambiguously measured outside the range of current observations : a system with a chirp mass @xmath0 m@xmath1 would unambiguously contain the smallest - mass neutron star observed , and a system with @xmath2 must contain a black hole .
however , additional information would be needed to distinguish between a binary containing two @xmath3 m@xmath1 neutron stars and an exotic neutron - star black - hole binary .
we also identify those configurations that could be unambiguously identified as black - hole binaries , and show how the observation of an electromagnetic counterpart to a neutron - star black - hole binary could be used to constrain the black - hole spin . .
And you have already written the first three sentences of the full article: the first observing runs of the advanced laser interferometer gravitational - wave observatory ( aligo ) are expected in @xmath4 , with advanced virgo following on a similar schedule @xcite .
the primary source for these observatories is the coalescence of binaries containing black holes and/or neutron stars , with predicted rates between a few and several hundred per year at detector design sensitivity @xcite .
the components of these binaries are formed in supernovae when the core of a massive star collapses to a compact remnant , although the exact collapse mechanism remains unknown ..
Please generate the next two sentences of the article | detailed knowledge of the mass distribution of black holes and neutron stars will provide vital clues to their formation as well as explore the equation of state ( eos ) of nuclear matter at high densities .
measuring the upper and lower limits of neutron - star masses allows us to constrain the supernova engine and the nuclear physics of neutron - star remnants @xcite . |
4,189 | Suppose that you have an abstract for a scientific paper: we consider the orbital evolution of the s - stars , the young main - sequence stars near the supermassive black hole ( sbh ) at the galactic center ( gc ) , and put constraints on competing models for their origin .
our analysis includes for the first time the joint effects of newtonian and relativistic perturbations to the motion , including the dragging of inertial frames by a spinning sbh as well as torques due to finite-@xmath0 asymmetries in the field - star distribution ( resonant relaxation , rr ) .
the evolution of the s - star orbits is strongly influenced by the schwarzschild barrier ( sb ) , the locus in the ( @xmath1 ) plane where rr is ineffective at driving orbits to higher eccentricities .
formation models that invoke tidal disruption of binary stars by the sbhtend to place stars below ( i.e. , at higher eccentricities than ) the sb ; some stars remain below the barrier , but most stars are able to penetrate it , after which they are subject to rr and achieve a nearly thermal distribution of eccentricities .
this process requires roughly @xmath2myr in nuclear models with relaxed stellar cusps , or @xmath3myr , regardless of the initial distribution of eccentricities , in nuclear models that include a dense cluster of @xmath4 black holes .
we find a probability of @xmath5 for any s - star to be tidally disrupted by the sbh over its lifetime . .
And you have already written the first three sentences of the full article: observations of the galactic center ( gc ) reveal a cluster of about 20 stars , mainly main - sequence b stars , that extends outward to about a tenth of a parsec from the central supermassive black hole ( sbh ; * ? ? ?
these stars , usually referred to as `` s - stars , '' follow orbits that are randomly oriented and have a nearly `` thermal '' distribution of eccentricities , @xmath6 @xcite .
the existence of such young stars so close to the gc sbh challenges our understanding of star formation since the strong tidal field of the sbh should inhibit the collapse and fragmentation of molecular clouds @xcite . for this reason.
Please generate the next two sentences of the article | , it is usually assumed that the s - stars formed elsewhere and migrated to their current locations . however , the migration mechanisms proposed in the literature result in orbital distributions that differ substantially from what is observed .
post - migration dynamical evolution due to gravitational interactions with other stars or stellar black holes ( bhs ) has been invoked to bring the predicted orbital distributions more in line with observations ( e.g. , * ? ? ? |
4,190 | Suppose that you have an abstract for a scientific paper: x - ray observations have revealed in other galaxies a class of extra - nuclear x - ray point sources with x - ray luminosities of @xmath0@xmath1 erg / sec , exceeding the eddington luminosity for stellar mass x - ray binaries . these ultra - luminous x - ray sources ( ulxs ) may be powered by intermediate mass black hole of a few thousand @xmath2 or stellar mass black holes with special radiation processes . in this paper , we present a survey of ulxs in 313 nearby galaxies with @xmath3@xmath4@xmath5 within 40 mpc with 467 rosat hri archival observations .
the hri observations are reduced with uniform procedures , refined by simulations that help define the point source detection algorithm employed in this survey .
a sample of 562 extragalactic x - ray point sources with @xmath6@xmath7 erg / sec is extracted from 173 survey galaxies , including 106 ulx candidates within the @xmath3 isophotes of 63 galaxies and 110 ulx candidates between 12@xmath8 of 64 galaxies , from which a clean sample of 109 ulxs is constructed to minimize the contamination from foreground or background objects .
the strong connection between ulxs and star formation is confirmed based on the striking preference of ulxs to occur in late - type galaxies , especially in star forming regions such as spiral arms .
ulxs are variable on time scales over days to years , and exhibit a variety of long term variability patterns .
the identifications of ulxs in the clean sample show some ulxs identified as supernovae ( remnants ) , hii regions / nebulae , or young massive stars in star forming regions , and a few other ulxs identified as old globular clusters . in a subsequent paper ,
the statistic properties of the survey will be studied to calculate the occurrence frequencies and luminosity functions for ulxs in different types of galaxies to shed light on the nature of these enigmatic sources . .
And you have already written the first three sentences of the full article: ultra - luminous x - ray sources ( ulxs ) are extra - nuclear sources with luminosities in the range of @xmath9 erg / sec in other galaxies , and have been observed by rosat , asca , recently by xmm - newton and chandra observatory in large numbers . as compared to the cases of the x - ray binaries in our galaxy , which are powered by accretion onto neutron stars or stellar mass black holes and
have luminosities of @xmath10 erg / sec , the luminosities of ulxs require accreting compact objects of masses @xmath11
@xmath12 @xmath2 if they emit at @xmath13 of the eddington luminosity , typical of galactic x - ray binaries . while the required masses could be much larger if they emit at much less than @xmath13 of the eddington luminosity , as in the cases of some low luminosity active galactic nuclei ( agn ) , the masses can not be much greater than @xmath14 @xmath2 for these extra - nuclear sources to survive the dynamic friction over a few gigayears ( colbert 1999 ) ..
Please generate the next two sentences of the article | such intermediate mass compact objects can only be black holes , and if they exist , are the missing links between stellar mass black holes and super - massive black holes in the nuclei of galaxies . while the explanation with intermediate mass black holes is simple , intriguing and astrophysically interesting , such black holes are not predicted by ordinary stellar evolution theories . it is suggested that black holes of a few hundred @xmath2 can form from the death of pop iii stars , and more massive ones might form from multiple stellar interactions in some dense clusters , hencing manifest as ultra - luminous x - ray sources ( portegies zwart et al .
alternatively , these x - ray sources could be stellar mass black holes or neutron stars whose apparent super - eddington luminosities are due to some special processes . |
4,191 | Suppose that you have an abstract for a scientific paper: a recently performed _
xmm - newton _ observation of the ulirg ngc 6240 clearly indicates the presence of an agn contribution to its x - ray spectrum . in the 5.0 - 7.0 kev energy range
there is a clear signature of the fluorescent fe k @xmath0 lines at 6.4 , 6.7 and 6.9 kev , respectively .
the line strength of the 6.4 kev line can not be produced by a thermal component .
the 0.3 - 10.0 kev spectral energy distribution is characterized by the following components : ( i ) two hot thermal components ( the starburst ) , ( ii ) one direct component ( heavily absorbed ; agn is hidden ) , ( iii ) one reflection component ( the agn ) , ( iv ) three narrow fe lines
. the model parameters for the broad - band spectral energy distribution are consistent with the results of previously works .
# 1_#1 _ # 1_#1 _ = # 1 1.25 in .125 in .25 in .
And you have already written the first three sentences of the full article: many if not all high - luminous infrared galaxies ( ulirgs , @xmath1 ) possess regions hidden by huge amounts of dust .
this makes it difficult to ascertain whether this enormous energy output is due to a starburst activity or an accretion process onto a supermassive black hole .
one of the best known objects to study this relationship is the nearby ulirg ngc 6240 ( assuming @xmath2 ) ..
Please generate the next two sentences of the article | infrared observations favour an energy source dominated by starburst processes , whereas observations in the x - ray range point to an agn as the central engine ( @xmath3 ) .
we have analyzed the data of ngc 6240 taken from an 24 ksec observation with _ xmm - newton _ using the epic - pn and epic - mos instruments . in order to investigate the fe line complex around 6.4 kev and the 0.3 - 10.0 kev spectrum as a whole the high sensitivity and |
4,192 | Suppose that you have an abstract for a scientific paper: the kinetic energy of supernovae ( sne ) accompanied by gamma - ray bursts ( grbs ) tends to cluster near @xmath0erg , with @xmath1erg an upper limit to which no compelling exceptions are found ( assuming a certain degree of asphericity ) , and it is always significantly larger than the intrinsic energy of the grb themselves ( corrected for jet collimation ) .
this energy is strikingly similar to the maximum rotational energy of a neutron star rotating with period 1 ms .
it is therefore proposed that all grbs associated with luminous sne are produced by magnetars .
grbs that result from black hole formation ( collapsars ) may not produce luminous sne .
x - ray flashes ( xrfs ) , which are associated with less energetic sne , are produced by neutron stars with weaker magnetic field or lower spin .
[ firstpage ] supernovae : general stars : magnetars gamma - ray bursts : general .
And you have already written the first three sentences of the full article: the connection between long - duration gamma - ray bursts ( grbs ) and sne is well established in the local universe .
following the first cases of coincidences @xcite , now for almost every grb at redshift @xmath2 a corresponding sn has been identified @xcite . despite the diverse properties of their associated grbs , all grb / sne observed so far are luminous , broad - lined type ic sne ( no h , no he , * ? ? ?
the very broad lines indicate a high expansion velocity of the ejecta , and point to a high explosion kinetic energy ( @xmath3 ) @xcite ..
Please generate the next two sentences of the article | detailed models of grb / sne yield a typical sn @xmath3 of a few @xmath0erg ( depending on the asphericity of the sn ) , an ejected mass @xmath4@xmath5 , and a @xmath6ni mass of @xmath7 .
this places grb / sne at the luminous , energetic and massive end of sneic ( e.g. * ? ? ? |
4,193 | Suppose that you have an abstract for a scientific paper: one limit to the fidelity of quantum logic operations on trapped ions arises from heating of the ions collective modes of motion .
sympathetic cooling of the ions during the logic operations may eliminate this source of errors .
we discuss benefits and drawbacks of this proposal , and describe possible experimental implementations .
we also present an overview of trapped - ion dynamics in this scheme . .
And you have already written the first three sentences of the full article: one of the most attractive physical systems for generating large entangled states and realizing a quantum computer @xcite is a collection of cold trapped atomic ions @xcite .
the ion trap quantum computer stores one or more quantum bits ( qubits ) in the internal states of each trapped ion , and quantum logic gates ( implemented by interactions with externally applied laser beams ) can couple qubits through a collective quantized mode of motion of the ion coulomb crystal .
loss of coherence of the internal states of trapped ions is negligible under proper conditions but heating of the motion of the ion crystal may ultimately limit the fidelity of logic gates of this type ..
Please generate the next two sentences of the article | in fact , such heating is currently a limiting factor in the nist ion - trap quantum logic experiments @xcite .
+ + electric fields from the environment readily couple to the motion of the ions , heating the ion crystal @xcite . |
4,194 | Suppose that you have an abstract for a scientific paper: let @xmath0 be the davis complex for a coxeter system @xmath1 .
the automorphism group @xmath2 of @xmath0 is naturally a locally compact group , and a simple combinatorial condition due to haglund
paulin determines when @xmath2 is nondiscrete .
the coxeter group @xmath3 may be regarded as a uniform lattice in @xmath2 .
we show that many such @xmath2 also admit a nonuniform lattice @xmath4 , and an infinite family of uniform lattices with covolumes converging to that of @xmath4 .
it follows that the set of covolumes of lattices in @xmath2 is nondiscrete .
we also show that the nonuniform lattice @xmath4 is not finitely generated .
examples of @xmath0 to which our results apply include buildings and non - buildings , and many complexes of dimension greater than @xmath5 .
to prove these results , we introduce a new tool , that of group actions on complexes of groups " , and use this to construct our lattices as fundamental groups of complexes of groups with universal cover @xmath0 . .
And you have already written the first three sentences of the full article: let @xmath2 be a locally compact topological group , with haar measure @xmath6 .
a discrete subgroup @xmath7 is a _ lattice _ if @xmath8 carries a finite @xmath2invariant measure , and is _ uniform _ if @xmath8 is compact .
some basic questions are : 1 ..
Please generate the next two sentences of the article | [ q : existence ] does @xmath2 admit a ( uniform or nonuniform ) lattice ? 2 .
[ q : covolumes ] what is the set of _ covolumes _ of lattices in @xmath2 , that is , the set of positive reals @xmath9 3 . |
4,195 | Suppose that you have an abstract for a scientific paper: a universe described by braneworlds is studied in a cyclic scenario .
as expected such an oscillating universe will undergo turnarounds , whenever the phantom energy density reaches a critical value from either side .
it is found that a universe described by rsii brane model will readily undergo oscillations if , either the brane tension , @xmath0 or the bulk cosmological constant , @xmath1 is negative .
the dgp brane model does not readily undergo cyclic turnarounds .
hence for this model a modified equation is proposed to incorporate the cyclic nature .
it is found that there is always a remanent mass of a black hole at the verge of a turnaround . hence contrary to known results in literature , it is found that the destruction of black holes at the turnaround is completely out of question . finally to alleviate ,
if not solve , the problem posed by the black holes , it is argued that the remanent masses of the black holes do not act as a serious defect of the model because of hawking evaporation
. 0.2 cm .
And you have already written the first three sentences of the full article: cyclic universe has always been a burning topic in the field of theoretical cosmology , since it is expected to avoid the initial singularity by providing an infinitely oscillating universe .
however cyclic universe confront a serious problem of black holes(bhs ) .
if the bhs formed during the expanding phase survives into the next cycle they will grow even larger from one cycle to the next and act as a serious defect in an otherwise nearly uniform universe . with the passage of time the bhs will occupy the entire horizon and then the cyclic models will break away . in this paper.
Please generate the next two sentences of the article | we investigate the possibility of an oscillating universe in two of the well known models of brane - world gravity , namely , rsii brane and dgp brane models .
randall and sundrum @xcite proposed a bulk - brane model to explain the higher dimensional theory , popularly known as rs ii brane model . according to this model we live in a four dimensional world ( called 3-brane , a domain wall ) which is embedded in a 5d space time ( bulk ) . |
4,196 | Suppose that you have an abstract for a scientific paper: in this fluid dynamics video we show how a drop of water ( @xmath0 ) freezes into a singular shape when deposited on a cold surface ( @xmath1 ) .
the process of solidification can be observed very clearly due to the change in refraction when water turns into ice .
the drop remains approximately spherical during most of the process , with a freezing front moving upwards and smoothly following the interface .
however , at the final stage of freezing , when the last cap of liquid turns into ice , a singular tip develops spontaneously .
interestingly , the sharp tip of the ice drop acts as a preferential site for deposition of water vapour , and a beautiful `` tree '' of ice crystals develops right at the tip .
the tip singularity attracts the vapour in analogy to a sharp lightning rod attracting lightning . .
And you have already written the first three sentences of the full article: the experimental setup ( fig . [ fig1 ] ) consisted of a brass container filled with solid carbon dioxide ( dry ice ) .
a clean glass slide was placed over the brass container , where a drop ( @xmath2 ) of deionized and degassed water was deposited using a syringe pump . to increase contrast and observe the freezing front
, red food dye was added to the water ..
Please generate the next two sentences of the article | the process was recorded from the side using a long distance microscope ( vzm1000 edmund optics ) mounted on a color camera , at a frame rate of 50 frames per second .
we used both backlight and bottom light illumination provided by optic fiber lamps . |
4,197 | Suppose that you have an abstract for a scientific paper: in this work we describe a non - parametric disease model that links the temporal change of the prevalence of an infectious disease to the incidence and the recovery rates .
the model is only based on the common epidemiological measures incidence and recovery rate . as an application ,
the model is used to calculate the prevalence of influenza in germany for a hypothetical birth cohort during 2001 and 2013 . .
And you have already written the first three sentences of the full article: in mathematically modelling infectious diseases , often compartment models are used .
compartment models divide the population under consideration into disjunct sets of individuals with the same biological characteristics .
prominent examples in infectious disease modelling are the _.
Please generate the next two sentences of the article | si _ , _ sis _ and _ sirs _ models , see for example @xcite .
the models have in common that they depend on one or more parameters . |
4,198 | Suppose that you have an abstract for a scientific paper: for planets other than earth , particularly exoplanets , interpretation of the composition and structure depends largely on comparing the mass and radius with the composition expected given their distance from the parent star .
the composition implies a mass - radius relation which relies heavily on equations of state calculated from electronic structure theory and measured experimentally on earth .
we lay out a method for deriving and testing equations of state , and deduce mass - radius and mass - pressure relations for key , relevant materials whose equation of state is reasonably well established , and for differentiated fe / rock .
we find that variations in the equation of state , such as may arise when extrapolating from low pressure data , can have significant effects on predicted mass - radius relations , and on planetary pressure profiles .
the relations are compared with the observed masses and radii of planets and exoplanets , broadly supporting recent inferences about exoplanet structures .
kepler-10b is apparently ` earth - like , ' likely with a proportionately larger core than earth s , nominally 2/3 of the mass of the planet .
corot-7b is consistent with a rocky mantle over an fe - based core which is likely to be proportionately smaller than earth s .
gj 1214b lies between the mass - radius curves for h@xmath0o and ch@xmath1 , suggesting an ` icy ' composition with a relatively large core or a relatively large proportion of h@xmath0o .
corot-2b is less dense than the hydrogen relation , which could be explained by an anomalously high degree of heating or by higher than assumed atmospheric opacity .
hat - p-2b is slightly denser than the mass - radius relation for hydrogen , suggesting the presence of a significant amount of matter of higher atomic number .
corot-3b lies close to the hydrogen relation .
the pressure at the center of kepler-10b is @xmath2tpa .
the central pressure in corot-7b is probably close to 0.8tpa , though may be up to 2tpa .
these pressures....
And you have already written the first three sentences of the full article: planets outside the solar system have been detected since 1992 @xcite from the doppler shift of spectral features in emission from the star , which determines the orbital period and places a constraint on the mass of the planet @xcite . since 1999 , the presence of exoplanets has also been deduced from their transit across the face of the parent star @xcite .
the fraction of light blocked by the planet allows the radius of the planet to be deduced as a function of the radius of the star @xcite .
subsequently , several hundred exoplanets have been detected at different distances from their stars , and the precision with which mass and radius have been deduced has increased for some exoplanets to better than 10% in both mass and radius @xcite . in 2001 , light from an exoplanet was detected directly @xcite , opening the window to studies of exoplanet structure through the composition and temperature of the surface or atmosphere ..
Please generate the next two sentences of the article | however , inferences about the composition and structure rely on the comparison of mass and radius with planets within the solar system . with the exception of earth , which is currently the only planet for which seismic data exist , interpretations of the internal structure of the planets
rely in turn on assumptions about the composition and temperature profiles through the planet |
4,199 | Suppose that you have an abstract for a scientific paper: * we consider cosmological scenarios based on @xmath0 theories of gravity ( @xmath1 is the ricci scalar and @xmath2 is the trace of the energy - momentum tensor ) and numerically reconstruct the function @xmath0 which is able to reproduce the same expansion history generated , in the standard general relativity theory , by dark matter and holographic dark energy .
we consider two special @xmath0 models : in the first instance , we investigate the modification @xmath3 , i.e. the usual einstein - hilbert term plus a @xmath4 correction . in the second instance
, we consider a @xmath5 theory , i.e. a @xmath2 correction to the renown @xmath6 theory of gravity . * .
And you have already written the first three sentences of the full article: the nature of dark matter and dark energy is one of the most important issues today in physics
. there are strong observational evidences in astrophysics and cosmology for the existence of these two components of the cosmic energy budget , indicating that about @xmath7 of the universe is composed by dark matter ( about @xmath8 ) and by dark energy ( about @xmath9 ) , but no direct detection has been reported until now .
the usual candidates * for * dark matter ( neutralinos and axions , for example ) and dark energy ( cosmological constant , quintessence , etc . ) lead to very robust scenarios , but at same time they must face theoretical and observational issues . for recent reviews on the subject ,.
Please generate the next two sentences of the article | see for example @xcite .
the strongest issue is perhaps the one regarding dark energy as the vacuum expectation value of some quantum field , which would be a natural candidate , but whose correct theoretical value could be predicted only in the framework of a complete theory of quantum gravity , which still we do not possess . nevertheless , it is possible , at least , to guess some of the features of this theory . |
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