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3,800 | Suppose that you have an abstract for a scientific paper: basin - hopping ( bh ) or monte - carlo minimization ( mcm ) is so far the most reliable algorithms in chemical physics to search for the lowest - energy structure of atomic clusters and macromolecular systems .
bh transforms the complex energy landscape into a collection of basins , and explores them by hopping , which is achieved by random monte carlo moves and acceptance / rejection using the metropolis criterion . in this report
, we introduce the jumping process in addition to the hopping process in bh . jumping
are invoked when the hopping stagnates by reaching the local optima , and are achieved using the monte carlo move at the temperature @xmath0 without rejection .
our basin - hopping with occasional jumping ( bhoj ) algorithm is applied to the lennard - jones clusters of several notoriously difficult sizes .
it was found that the probability of locating the true global optima using bhoj is significantly higher than the original bh .
basin - hopping , lowest - energy structure , lennard - jones cluster 02.60.pn , 02.70.tt , 36.40.mr .
And you have already written the first three sentences of the full article: the monte carlo method based on the metropolis algorithm is the most successful and influential stochastic algorithm of the 20th century and has been used in variety of applications not limited to physics @xcite .
the method is powerful in an exhaustive search of highly multi - dimensional phase space , and , hence , has been routinely used to calculate the thermal averaging of statistical physics . aside from the applications to statistical physics , the metropolis algorithm has been used as a vehicle for global optimization , that is , a task to search for the lowest minimum point in a rugged landscapes in a high dimension .
in fact , the simulated annealing ( sa ) @xcite based on the metropolis algorithm is the oldest metaheuristics in global optimization . in global optimization.
Please generate the next two sentences of the article | , a good balance between a global search ( exploration ) and a local search ( exploitation ) is necessary .
since the metropolis algorithm has only the ability to perform a global search , it is usually necessary to augment sa using a more traditional local optimization method to handle realistic problems @xcite . |
3,801 | Suppose that you have an abstract for a scientific paper: the influence of the geometry of a thin superconducting sample on the penetration of the magnetic field lines and the arrangement of vortices are investigated theoretically .
we compare superconducting disks , squares and triangles with the same surface area having nonzero thickness .
the coupled nonlinear ginzburg - landau equations are solved self - consistently and the important demagnetization effects are taken into account .
we calculate and compare quantities like the free energy , the magnetization , the cooper - pair density , the magnetic field distribution and the superconducting current density for the three geometries . for given vorticity
the vortex lattice is different for the three geometries , i.e. it tries to adapt to the geometry of the sample .
this also influences the stability range of the different vortex states . for certain magnetic field
ranges we found a coexistence of a giant vortex placed in the center and single vortices toward the corners of the sample . also the @xmath0 phase diagram is obtained .
[ theorem]acknowledgement [ theorem]algorithm [ theorem]axiom [ theorem]claim [ theorem]conclusion [ theorem]condition [ theorem]conjecture [ theorem]corollary [ theorem]criterion [ theorem]definition [ theorem]example [ theorem]exercise [ theorem]lemma [ theorem]notation [ theorem]problem [ theorem]proposition [ theorem]remark [ theorem]solution [ theorem]summary .
And you have already written the first three sentences of the full article: in mesoscopic samples there is a competition between a triangle configuration of the vortex lattice as being the lowest energy configuration in bulk material ( and films ) and the boundary which tries to impose its geometry on the vortex lattice .
for example a circular geometry will favour vortices situated on a ring near the boundary and only far away from the boundary its influence diminishes and the triangular lattice may reappear .
therefore , it is expected that different geometries will favour different arrangements of vortices and will make certain vortex configurations more stable than others.
Please generate the next two sentences of the article | . in small systems vortices may overlap so strongly that it is more favourable to form one big giant vortex .
the latter will preferably have a circular geometry . as a consequence |
3,802 | Suppose that you have an abstract for a scientific paper: we consider a generalisation of the vicious walker problem in which @xmath0 random walkers in @xmath1 are grouped into @xmath2 families . using field - theoretic renormalisation group methods we calculate the asymptotic behaviour of the probability that no pairs of walkers from different families have met up to time @xmath3 . for @xmath4 ,
this is constant , but for @xmath5 it decays as a power @xmath6 , which we compute to @xmath7 in an expansion in @xmath8 .
the second order term depends on the ratios of the diffusivities of the different families . in two dimensions ,
we find a logarithmic decay @xmath9 , and compute @xmath10 exactly .
* families of vicious walkers * + 0.1 in john cardy + theoretical physics , 1 keble road , oxford ox1 3np , united kingdom + and all souls college , oxford + + department of physics , chuo university , kasuga , bunkyo - ku , tokyo 112 - 8551 , japan + .
And you have already written the first three sentences of the full article: [ sec1 ] consider the following problem : @xmath0 random walkers set off from the vicinity of the origin , in @xmath11-dimensional euclidean space , at time @xmath12 .
they are divided into @xmath2 different families : the number of walkers in the @xmath13th family is @xmath14 , so that @xmath15 . within a particular family ,
walkers are indifferent to each other : their paths may cross ..
Please generate the next two sentences of the article | however , each family behaves viciously towards all the others : if two walkers from different families meet , both are annihilated .
we may ask many different questions about this problem , but a fundamental quantity is the probability @xmath16 that all the walkers have still survived up to time @xmath3 . |
3,803 | Suppose that you have an abstract for a scientific paper: polarized inclusive deep - inelastic scattering is formulated in the light cone expansion .
the qcd evolution of the leading twist distribution functions is derived .
it is shown that the twist2 contribution to the structure functions @xmath0 is obtained via @xmath1 by a wandzura wilczek relation . .
And you have already written the first three sentences of the full article: inclusive unpolarized and polarized deeply inelastic diffractive scattering at high energies and momentum transfer is one of the important processes in lepton
nucleon scattering . as found by experiment , cf .
@xcite , there are interesting relations between the cross sections of these processes and those of inclusive deeply inelastic scattering : _ i ) _ the scaling violations of both processes are quite similar and _ ii ) _ the ratio of the differential cross sections in @xmath2 and @xmath3 are widely constant in the whole kinematic domain and are of @xmath4 . whereas the latter aspect can not be understood with perturbative methods the former calls for a rigorous analysis in perturbative qcd . in recent analyses @xcite.
Please generate the next two sentences of the article | this aspect has been investigated both for the unpolarized and the polarized case on the basis of the light cone expansion . by this method
the semi - exclusive processes of diffractive scattering could be related to forward scattering processes at short distances , for which similar evolution equations as in the deep inelastic case apply . |
3,804 | Suppose that you have an abstract for a scientific paper: in this fluid dynamics video , we demonstrate the first three circumferential modes of fast , large amplitude vibrations of compliant cylindrical shells carrying a fluid . .
And you have already written the first three sentences of the full article: we use shells made of vinylpolysiloxane ( a silicone - based elastomer ) with elastic moduli of @xmath0 , @xmath1 and @xmath2 mpa , as well as shells made of latex .
the shells range from @xmath3@xmath4 mm in diameter , @xmath3@xmath5 mm in length and approximately @xmath6@xmath0 mm in thickness .
we clamp one end of these shells onto a rigid nozzle and pass air through them at flow rates ranging from @xmath0@xmath7 liters per second ..
Please generate the next two sentences of the article | when the flow rate of air in the shells exceeds a certain critical value , dependent on the dimensions and material properties of each shell , the shell becomes unstable and begins to vibrate .
the mode of vibration corresponds to one of the circumferential normal modes of vibration of cantilevered cylindrical shells . |
3,805 | Suppose that you have an abstract for a scientific paper: we compute electromagnetic fields created by a relativistic charged spin - half particle in empty space at distances comparable to the particle compton wavelength .
the particle is described as a wave packet evolving according to the dirac equation .
it produces the electromagnetic field that is essentially different from the coulomb field due to the quantum diffusion effect . .
And you have already written the first three sentences of the full article: it has been known for a while that very intense electromagnetic fields are created in ultra - relativistic hadronic and nuclear collisions @xcite . however , no convincing experimental evidence of their impact on the scattering dynamics has been observed . in recent years , a renewed interest to this subject
was motivated by the relativistic heavy - ion collision experiments .
the electromagnetic fields are intense enough to modify the properties of the nuclear matter produced in these collisions . in order to evaluate the impact of these fields on the nuclear matter , it is crucial to know their space - time structure . in @xcite production of the electromagnetic fields.
Please generate the next two sentences of the article | was studied using the hadron transport models , neglecting the nuclear medium electric and magnetic response and flow . in @xcite
it was pointed out that the quantum nature of the nucleus wave function gives rise to strong field fluctuation , so that even in central collisions the r.m.s . |
3,806 | Suppose that you have an abstract for a scientific paper: the dynamical reaction of the particles accelerated at a shock front by the first order fermi process can be determined within kinetic models that account for both the hydrodynamics of the shocked fluid and the transport of the accelerated particles .
these models predict the appearance of multiple solutions , all physically allowed .
we discuss here the role of injection in selecting the _ real _ solution , in the framework of a simple phenomenological recipe , which is a variation of what is sometimes referred to as _ thermal leakage_. in this context we show that multiple solutions basically disappear and when they are present they are limited to rather peculiar values of the parameters .
we also provide a quantitative calculation of the efficiency of particle acceleration at cosmic ray modified shocks and we identify the fraction of energy which is advected downstream and that of particles escaping the system from upstream infinity at the maximum momentum .
the consequences of efficient particle acceleration for shock heating are also discussed .
cosmic rays ; high energy ; origin ; acceleration .
And you have already written the first three sentences of the full article: diffusive particle acceleration at non - relativistic shock fronts is an extensively studied phenomenon .
detailed discussions of the current status of the investigations can be found in some excellent reviews ( drury 1983 ; blandford & eichler 1987 ; berezhko & krimsky 1988 ; jones & ellison 1991 ; malkov & drury 2001 ) . while much is by
now well understood , some issues are still subjects of much debate , for the theoretical and phenomenological implications that they may have ..
Please generate the next two sentences of the article | one of the most important of these is the reaction of the accelerated particles on the shock : the violation of the _ test particle approximation _ occurs when the acceleration process becomes sufficiently efficient that the pressure of the accelerated particles is comparable with the incoming gas kinetic pressure .
both the spectrum of the particles and the structure of the shock are changed by this phenomenon , which is therefore intrinsically nonlinear . at present |
3,807 | Suppose that you have an abstract for a scientific paper: in a gauge invariant formulation of the molecular electric dipole - photon interaction , the rigorous coupling is strictly linear in the photon creation and photon annihilation operators .
the linear coupling allows for a super - radiant phase transition as in the hepp - lieb formulation .
a previous notion of a quadratic - coupling `` no - go theorem '' for super - radiance is incorrect . also incorrect
is a previous assertion that the dipole - photon coupling has absolutely no effect on the thermal equations of state .
these dubious assertions were based on incorrect canonical transformations which eliminated the electric field ( and thereby eliminated the dipole - photon interaction ) which is neither mathematically nor physically consistent .
the correct form of the canonical transformations are given in this work which allows for the physical reality of super - radiant condensed matter phases . .
And you have already written the first three sentences of the full article: in an early paper on the interaction between radiation and molecular dipole moments @xcite , dicke formulated a model which was later shown to exhibit a super - radiant phase transition@xcite .
the notion that such phase transitions should exist in condensed matter systems has been investigated in a series of papers by preparata and coworkers@xcite and others@xcite .
different workers have come to somewhat different conclusions concerning super - radiant phase transitions @xcite ..
Please generate the next two sentences of the article | some doubt has been expressed@xcite concerning the physical laboratory reality of super - radiant phase transition .
the mathematical issues are as follows : ( i ) it appears,_at first glance _ , that quadratic terms ( in photon creation and annihilation operators ) enter into the model via quadratic terms in the vector potential @xmath0 . |
3,808 | Suppose that you have an abstract for a scientific paper: the variability observed in many complex gamma - ray bursts ( grbs ) is inconsistent with causally connected variations in a single , symmetric , relativistic shell interacting with the ambient material ( `` external shocks '' ) .
rather , either the central site must produce @xmath0 erg s@xmath1 for hundreds of seconds ( `` internal shocks '' ) or the local spherical symmetry of the shell must be broken on an angular scale much smaller than @xmath2 where @xmath3 is the bulk lorentz factor for the shell . the observed variability in the external shock models arises from the number of causally connected regions that ( randomly ) become active .
we define the `` surface filling factor '' to be the ratio of the area of causally connected regions that become active to the observable area of the shell . from the observed variability in 52 batse bursts
, we estimate the surface filling factor to be typically @xmath4 although some values are near unity .
we find that the surface filling factor , @xmath5 , is @xmath6 in both the constant @xmath3 phase ( which probably produces the grb ) and the deaccelerating phase ( which probably produces the x - ray afterglows ) . here
, @xmath7 is a typical time scale of variability and @xmath8 is the time since the initial signal .
we analyze the 2 hr flare seen by asca 36 hr after the grb and conclude that the surface filling factor must be small ( @xmath9 ) in the x - ray afterglow phase as well .
compared to the energy required for an isotropic shell , @xmath10 , explanations for low surface filling factor can either require more energy ( @xmath11 erg ) or less energy ( @xmath12 erg ) .
thus , the low filling factor can not be used as a strong argument that grbs must be internal shocks .
= 1 # 1#2#1 .
And you have already written the first three sentences of the full article: gamma - ray burst ( grb ) spectra often extend to very high energies with no indication of attenuation by photon - photon interactions .
this implies substantial relativistic bulk motion of the radiating material with lorentz factors in the range of @xmath13 to @xmath14 . at cosmological distances ,
grbs require an energy reservoir on the order of @xmath15 erg ..
Please generate the next two sentences of the article | the likely sources of such a reservoir would be the rest mass of a compact object released during a merger ( e.g. , either neutron star
neutron star or neutron star black hole ) . |
3,809 | Suppose that you have an abstract for a scientific paper: we consider anisotropies in the cosmic microwave background ( cmb ) generated by spatially limited seeds ; these objects could correspond to relics of high energy symmetry breaking in the early universe .
it is shown how the cmb perturbation propagate beyond the size of the seed in the form of waves traveling with the cmb sound velocity . moreover , these waves are the substantial part of the signal , both for polarization and temperature .
the explanation of this phenomenology in terms of the cmb equations is given .
observationally , this effect is threefold promising .
first , it enlarges the signal from a seed intersecting the last scattering surface to the scale of the cmb sound horizon at decoupling , that is roughly one degree in the sky .
second , it offers cross correlation possibilities between the polarization and temperature signals .
third , it allows to unambiguously distinguish these structures from point - like astrophysical sources . .
And you have already written the first three sentences of the full article: there is now a lot of interest in the connection between high energy physics and cosmology .
it is motivated by the possibility that processes not reproducible here on the earth actually occurred in the early universe .
for this reason , a lot of work is currently in progress to predict in detail the traces that such processes could have left , in order to recognize them and gain insight into physics that is still unknown , or only theoretically approached ..
Please generate the next two sentences of the article | the unknown sector of physics extends from the energy scales presently explored by accelerators , described successfully by the standard model of the known elementary particles , up to the scales of more fundamental theories , perhaps supersymmetry and supergravity ; such regimes , as thought in the early universe , should have taken place at temperatures @xmath0 ( in energy units ) in the interval @xmath1 according to our hypotheses , two main classes of phenomena took place in the early universe : an era of accelerated expansion , the inflation , and the breaking of high energy symmetries , see @xcite .
the first process should leave traces in the form of gaussian and scale - invariant density fluctuations @xcite ; this visually corresponds to a completely disordered distribution of hills and wells in the density field , covering all the scales . |
3,810 | Suppose that you have an abstract for a scientific paper: violent variation of transit depths and an ingress - egress asymmetry of the transit light curve discovered in kic 12557548have been interpreted as evidences of a catastrophic evaporation of atmosphere with dust ( @xmath0 ) from a close - in small planet . to explore what drives the anomalous atmospheric escape , we perform time - series analysis of the transit depth variation of _ kepler _ archival data for @xmath1 3.5 yr . we find a @xmath2% periodic variation of the transit depth with @xmath3 days , which is within the error of the rotation period of the host star estimated using the light curve modulation , @xmath4 days .
we interpret the results as evidence that the atmospheric escape of kic 12557548bcorrelates with stellar activity .
we consider possible scenarios that account for both the mass loss rate and the correlation with stellar activity .
x - ray and ultraviolet ( xuv)-driven evaporation is possible if one accepts a relatively high xuv flux and a high efficiency for converting the input energy to the kinetic energy of the atmosphere .
star - planet magnetic interaction is another possible scenario though huge uncertainty remains for the mass loss rate . .
And you have already written the first three sentences of the full article: planetary evaporation is one of the most crucial factors that determines the evolution and fate of close - in planets .
the atmospheric escapes of hot jupiters have been extensively investigated from both the extreme ultraviolet observations and theory .
the impacts of evaporation on the evolution of even smaller planets , including super - earths and super - neptunes , has been also recognized ..
Please generate the next two sentences of the article | recently @xcite ( hereafter r12 ) found violent variation of transit depths and an ingress - egress asymmetry of kic 12557548 , which have been interpreted as evidences of a catastrophic evaporation of a small planet ( r12 , * ? ? ?
* hereafter pc13 ) . analyzing the intensity of forward scattering , and |
3,811 | Suppose that you have an abstract for a scientific paper: many stochastic processes are defined on special geometrical objects like spheres and cones .
we describe how tools from harmonic analysis , i.e. fourier analysis on groups , can be used to investigate probability density functions ( pdfs ) on groups and homogeneous spaces .
we consider the special case of the lorentz group su(1,1 ) and the unit disk with its hyperbolic geometry , but the procedure can be generalized to a much wider class of lie - groups .
we mainly concentrate on the mehler - fock transform which is the radial part of the fourier transform on the disk .
some of the characteristic features of this transform are the relation to group - convolutions , the isometry between signal and transform space , the relation to the laplace - beltrami operator and the relation to group representation theory .
we will give an overview over these properties and their applications in signal processing .
we will illustrate the theory with two examples from low - level vision and color image processing . .
And you have already written the first three sentences of the full article: in many applications we know that the data or measurement vectors do not fill the whole vector space but that they are confined to some special regions .
often the form of these regions is defined by problem specific constraints .
typical examples are color vectors ..
Please generate the next two sentences of the article | the values in these vectors represent photon counts and therefore they must be non - negative and color vectors are all constrained to lie in the positive part of the vector space . apart from the measurement vectors we are also interested in transformations acting on these measurements .
a typical example in the case of color is the multiplication of the vectors with a global constant . |
3,812 | Suppose that you have an abstract for a scientific paper: in the companion paper @xcite , we use classical measures based on force probability density functions ( pdfs ) , as well as betti numbers ( quantifying the number of components , related to force chains , and loops ) , to describe the force networks in tapped systems of disks and pentagons . in the present work ,
we focus on the use of persistence analysis , that allows to describe these networks in much more detail .
this approach allows not only to describe , but also to quantify the differences between the force networks in different realizations of a system , in different parts of the considered domain , or in different systems .
we show that persistence analysis clearly distinguishes the systems that are very difficult or impossible to differentiate using other means .
one important finding is that the differences in force networks between disks and pentagons are most apparent when loops are considered : the quantities describing properties of the loops may differ significantly even if other measures ( properties of components , betti numbers , or force pdfs ) do not distinguish clearly the investigated systems . .
And you have already written the first three sentences of the full article: in the companion paper @xcite we compare the force networks in tapped systems by using relatively simple measures : probability density functions ( pdfs ) for normal and tangential forces between the particles , correlation functions describing positional order of the considered particles , as well as possible correlations of the emerging force networks .
these classical measures are supplemented by analysis of cluster sizes and distributions at different force levels ( i.e. , by considering the part of the force network that only includes contacts involving forces exceeding a threshold ) .
these results have uncovered some differences between the force networks in the considered systems ..
Please generate the next two sentences of the article | for example , we have found that the number of clusters as a function of the force level is heterogeneous in the tapped systems under gravity , with different distributions deeper in the samples compared to the ones measured closer to the surface .
however , some of the differences remain unclear . |
3,813 | Suppose that you have an abstract for a scientific paper: ngc 2146 is a peculiar spiral galaxy which is currently undergoing a major burst of star formation and is immersed in a extended hi structure that has morphological and kinematical resemblence to a strong tidal interaction .
this paper reports aperture synthesis observations carried out in the 21 cm line with the very large array ( vla ) of two fields positioned to optimally cover the hi streams to the north and south of the galaxy , along with a 300 ft total power spectral mapping program to recover the low surface brightness extended emission .
the observations reveal elongated streams of neutral hydrogen towards both the north and the south of the optical galaxy extending out up to 6 holmberg radii .
the streams are not in the principle plane of rotation of the galaxy , but instead are suggestive of a tidal interaction between ngc 2146 and a lsb companion that was destroyed by the encounter and remains undetected at optical wavelengths .
part of the southern stream is turning back to fall into the main galaxy , where it will create a long - lived warp in the hi disk of ngc 2146 .
analysis of the trajectory of the outlying gas suggests that the closest encounter took place about 0.8 billion years ago and that infall of debris will continue for a similar time span . .
And you have already written the first three sentences of the full article: ngc 2146 is a peculiar spiral galaxy as seen from both the optical image and the hi line profile . although it is classified as sab by de vaucouleurs et al .
( @xcite ) , it shows a broad range of peculiarities .
measured by its far infrared flux , it is one of the 12 brightest galaxies in the sky and lies at a distance of 12.2 mpc ( @xmath0=75 km s@xmath1 mpc@xmath1 , and 1@xmath2 corresponds to 3.5 kpc ) . in optical images.
Please generate the next two sentences of the article | there are two well - defined arms which mark the principal plane of rotation . superimposed across part of the nucleus
is an absorption band having the form of a hand , with four talon - like fingers " ( pease @xcite ) , which de vaucouleurs ( @xcite ) interpreted as being a third arm inclined to the plane of rotation . |
3,814 | Suppose that you have an abstract for a scientific paper: we set up a new general coorbit space theory for reproducing representations of a locally compact second countable group @xmath0 that are not necessarily irreducible nor integrable .
our basic assumption is that the kernel associated with the voice transform belongs to a frchet space @xmath1 of functions on @xmath0 , which generalizes the classical choice @xmath2 .
our basic example is @xmath3 , or a weighted versions of it . by means of this choice it is possible to treat , for instance , paley - wiener spaces and coorbit spaces related to shannon wavelets and _ schrdingerlets_. .
And you have already written the first three sentences of the full article: one of the central problems in applied mathematics is the analysis of signals .
usually signals are modelled by functions in suitable functions spaces ( e.g. , @xmath4 or sobolev spaces ) and they might be given explicitly or implicitly as the solution of an operator equation .
in most applications , the signal is transformed via a mapping into a suitable parameter space where it is easier to extract the information of interest . by discretization ,.
Please generate the next two sentences of the article | one obtains suitable building blocks that give rise to a discrete representation of the signal and can be used to decompose , compress and process the signal . over the years , many different transforms have been derived in response to particular problems , including the wavelet and gabor transforms .
representation theory , however , gives a general approach to construct continuous transforms for @xmath4-functions , and coorbit space theory allows both to extend these transforms to more general function spaces and to provide discrete systems . |
3,815 | Suppose that you have an abstract for a scientific paper: in this paper we present an improved lattice boltzmann model for compressible navier - stokes system with high mach number .
the model is composed of three components : ( i ) the discrete - velocity - model by watari and tsutahara [ phys rev e * 67*,036306(2003 ) ] , ( ii ) a modified lax - wendroff finite difference scheme where reasonable dissipation and dispersion are naturally included , ( iii ) artificial viscosity .
the improved model is convenient to compromise the high accuracy and stability .
the included dispersion term can effectively reduce the numerical oscillation at discontinuity .
the added artificial viscosity helps the scheme to satisfy the von neumann stability condition .
shock tubes and shock reflections are used to validate the new scheme . in our numerical tests
the mach numbers are successfully increased up to 20 or higher .
the flexibility of the new model makes it suitable for tracking shock waves with high accuracy and for investigating nonlinear nonequilibrium complex systems .
lattice boltzmann method , compressible flows , von neumann analysis 47.11.-j , 51.10.+y , 05.20.dd .
And you have already written the first three sentences of the full article: recently , the lattice boltzmann(lb ) method got substantial progress and has been regarded as a promising alternative for simulating many complex phenomena in various fields@xcite . unlike the macroscopic computational fluid dynamics or the microscopic molecular dynamics , the lb uses a mesoscopic discrete boltzmann equation to describe the fluid system . because of its intrinsic kinetic nature , the lb contains more physical connotation than navier - stokes or euler equations based on the continuum hypothesis@xcite . from the chapmann - enskog analysis , the latter can be derived from the former under the hydrodynamic limit . although having achieved great success in simulating incompressible fluids , the application of lb to high - speed compressible flows still needs substantial effort .
high - speed compressible flows are ubiquitous in various fields , such as explosion physics , aeronautics and so on@xcite .
simulation of the compressible navier - stokes system , especially for the those containing shock waves or contact discontinuities , is an interesting and challenging work . along the line.
Please generate the next two sentences of the article | , extensive efforts have been made in the past years .
alexander , et al@xcite presented a model where the sound speed is selectable ; yan , et al@xcite proposed a compressible lb model with three - speed - three - energy - level for the euler system ; yu and zhao@xcite composed a model for compressible flows by introducing an attractive force to soften sound speed ; sunsch_pre_1998,sch_pre_2000,sch_pre_2003 contributed a locally adaptive semi - discrete lb model , where the set of particle speed is chosen according to the local fluid velocity and internal energy so that the fluid velocity is no longer limited by the particle speed set . in the development of lb for navier - stokes systems , another way is referred to as the finite difference lattice boltzmann method ( fdlbm)@xcite . |
3,816 | Suppose that you have an abstract for a scientific paper: the general low - energy theory of electrons interacting via repulsive short - range interactions on graphene s honeycomb lattice at half filling is presented .
the exact symmetry of the lagrangian with local quartic terms for the dirac four - component field dictated by the lattice is identified as @xmath0time reversal , where @xmath1 is the dihedral group , and @xmath2 is a subgroup of the @xmath3 `` chiral '' group of the non - interacting lagrangian , that represents translations in dirac language .
the lagrangian describing spinless particles respecting this symmetry is parameterized by six independent coupling constants .
we show how first imposing the rotational , then lorentz , and finally chiral symmetry to the quartic terms - in conjunction with the fierz transformations - eventually reduces the set of couplings to just two , in the `` maximally symmetric '' local interacting theory .
we identify the two critical points in such a lorentz and chirally symmetric theory as describing metal - insulator transitions into the states with either time - reversal or chiral symmetry being broken .
the latter is proposed to govern the continuous transition in both the thirring and nambu - jona - lasinio models in 2 + 1 dimensions and with a single dirac field . in the site - localized , `` atomic '' , limit of the interacting hamiltonian , under the assumption of emergent lorentz invariance
, the low - energy theory describes the continuous transitions into the insulator with either a finite haldane s ( circulating currents ) or semenoff s ( staggered density ) masses , both in the universality class of the gross - neveu model .
the simple picture of the metal - insulator transition on a honeycomb lattice emerges at which the residue of the quasiparticle pole at the metallic , and the mass - gap in the insulating phase both vanish continuously as the critical point is approached .
in contrast to these two critical quantities , we argue that the fermi velocity is non - critical as a consequence....
And you have already written the first three sentences of the full article: two - dimensional honeycomb lattice of carbon atoms may be viewed as the mother of all other forms of carbon .
its crucial electronic property , which arises as a consequence of the absence of the inversion symmetry around the lattice site , is that the usual fermi surface is reduced to just two points .
the electronic dispersion may be linearized around these two points , after which it becomes isotropic and dependent on the single dimensionful parameter , fermi velocity @xmath4 ..
Please generate the next two sentences of the article | the pseudo - relativistic nature of the electronic motion in graphene has since its synthesis placed this material at the center stage of condensed matter physics .
many qualitatively novel phenomena that take , or may take place in such a system of `` dirac '' electrons are actively discussed in the rapidly growing literature on the subject . |
3,817 | Suppose that you have an abstract for a scientific paper: nuclear structure observables usually most effectively probe the properties of nuclear matter at subsaturation densities rather than at saturation density . we demonstrate that the electric dipole polarizibility @xmath0 in @xmath1pb is sensitive to both the magnitude @xmath2 and density slope @xmath3 of the symmetry energy at the subsaturation cross density @xmath4 @xmath5 . using the experimental data of @xmath0 in @xmath1pb from rcnp and the recent accurate constraint of @xmath2 from the binding energy difference of heavy isotope pairs , we extract a value of @xmath6 mev .
the implication of the present constraint of @xmath3 to the symmetry energy at saturation density , the neutron skin thickness of @xmath1pb and the core - crust transition density in neutron stars is discussed . .
And you have already written the first three sentences of the full article: due to its multifaceted roles in nuclear physics and astrophysics @xcite as well as new physics beyond the standard model @xcite , the symmetry energy has become a hot topic in current research frontiers of nuclear physics and astrophysics @xcite . during the last decade , a lot of experimental , observational and theoretical efforts have been devoted to constraining the magnitude @xmath7 and density slope @xmath8 of the symmetry energy at nuclear saturation density @xmath9 ( @xmath10 @xmath5 ) , i.e. , @xmath11 and @xmath12 . although important progress has been made , large uncertainties on the values of @xmath11 and @xmath12 still exist ( see , e.g. , refs .
for instance , while the @xmath11 is determined to be around @xmath13 mev , the extracted @xmath12 varies significantly from about @xmath14 to @xmath15 mev , depending on the observables and analysis methods . to better understand the model dependence and narrow the uncertainties of the constraints is thus of extreme importance . while many studies on heavy ion collisions and neutron stars have significantly improved our knowledge on the symmetry energy , more and more constraints on the symmetry energy have been obtained in recent years from analyzing the properties of finite nuclei , such as the nuclear binding energy @xcite , the neutron skin thickness @xcite , and the resonances and excitations @xcite .
furthermore , it has been realized that the properties of finite nuclei usually provide more precise constraints on @xmath7 and @xmath8 at subsaturation densities rather than at saturation density @xmath9 ..
Please generate the next two sentences of the article | this feature is understandable since the characteristic ( average ) density of finite nuclei is less than @xmath9 . for example , the average density of heavy nuclei ( e.g. , @xmath1pb ) is about @xmath16 @xmath5 , and thus the properties of heavy nuclei most effectively probe the properties of nuclear matter around @xmath16 @xmath5 @xcite .
indeed , a quite accurate constraint on the symmetry energy at the subsaturation cross density @xmath4 @xmath5 , i.e. , @xmath17mev , has been recently obtained from analyzing the binding energy difference of heavy isotope pairs @xcite . |
3,818 | Suppose that you have an abstract for a scientific paper: we present measurements of the higher - order clustering of red and blue galaxies as a function of scale and luminosity made from the two - degree field galaxy redshift survey ( 2dfgrs ) .
we use a counts - in - cells analysis to estimate the volume averaged correlation functions , @xmath0 , as a function of scale up to order @xmath1 , and also the reduced void probability function .
hierarchical amplitudes are constructed using the estimates of the correlation functions : @xmath2 .
we find that : 1 ) red galaxies display stronger clustering than blue galaxies at all orders measured .
2 ) red galaxies show values of @xmath3 that are strongly dependent on luminosity , whereas blue galaxies show no segregation in @xmath3 within the errors ; this is remarkable given the segregation in the variance .
3 ) the linear relative bias shows the opposite trend to the hierarchical amplitudes , with little segregation for the red sequence and some segregation for the blue .
4 ) faint red galaxies deviate significantly from the `` universal '' negative binomial reduced void probabilities followed by all other galaxy populations .
our results show that the characteristic colour of a galaxy population reveals a unique signature in its spatial distribution .
such signatures will hopefully further elucidate the physics responsible for shaping the cosmological evolution of galaxies .
galaxies : statistics , cosmology : theory , large - scale structure . .
And you have already written the first three sentences of the full article: the study of the large scale structure of the universe is now entering a new phase . the two - degree field galaxy redshift survey ( hereafter 2dfgrs ;
colless et al .
2001 , 2003 ) and the sloan digital sky survey ( sdss ; york et al ..
Please generate the next two sentences of the article | 2000 ; adelman - mccarthy et al .
2006 ) have yielded high precision measurements of the power spectrum of galaxy clustering on large scales ( cole et al . 2005 ; tegmark et al . |
3,819 | Suppose that you have an abstract for a scientific paper: a 4-parameter polynomial family of equations generalizing the camassa - holm and novikov equations that describe breaking waves is introduced .
a classification of low - order conservation laws , peaked travelling wave solutions , and lie symmetries is presented for this family .
these classifications pick out a 1-parameter equation that has several interesting features : it reduces to the camassa - holm and novikov equations when the polynomial has degree two and three ; it has a conserved @xmath0 norm and it possesses @xmath1-peakon solutions , when the polynomial has any degree ; and it exhibits wave - breaking for certain solutions describing collisions between peakons and anti - peakons in the case @xmath2 . .
And you have already written the first three sentences of the full article: there is considerable interest in the study of equations of the form @xmath3 that describe breaking waves . in this paper
we consider the equation @xmath4 with parameters @xmath5 ( not all zero ) and @xmath6 .
this 4-parameter family contains several integrable equations . for @xmath7 and @xmath8 , equation reduces respectively to the camassa - holm equation @xcite @xmath9 and the degasperis - procesi equation @xcite @xmath10 while for @xmath11 , equation becomes the novikov equation @xcite @xmath12 the three equations , , are integrable in the sense of having a lax pair , a bi - hamiltonian structure , as well as hierarchies of local symmetries and local conservation laws , and they also possess peaked travelling wave solutions ..
Please generate the next two sentences of the article | in addition to these integrable equations , many other non - integrable equations that admit breaking waves are included in the 4-parameter family .
for instance , there is the @xmath13-equation @xmath14 which unifies the camassa - holm and degasperis - procesi equations @xcite . |
3,820 | Suppose that you have an abstract for a scientific paper: decay of the superdeformed bands have been studied mainly concentrating upon the decay - out spin , which is sensitive to the tunneling probability between the super- and normal - deformed wells .
although the basic features are well understood by the calculations , it is difficult to precisely reproduce the decay - out spins in some cases .
comparison of the systematic calculations with experimental data reveals that values of the calculated decay - out spins scatter more broadly around the average value in both the @xmath0 150 and 190 regions , which reflects the variety of calculated tunneling probability in each band . .
And you have already written the first three sentences of the full article: decay of superdeformed ( sd ) rotational bands out to normal deformed ( nd ) states is one of the most interesting nuclear structure problems .
it can be viewed as a shape - coexistence phenomena , and the mixing mechanism of two states having very different internal structures can be studied as functions of angular momenta and excitation energies . using the compound mixing model @xcite ,
we have investigated the decay - out phenomena in @xcite , where a consistent description was presented and the rapid decay - out was well understood ..
Please generate the next two sentences of the article | after the calculation of @xcite , more systematic and improved calculations have been performed @xcite , in which all the relevant quantities to the decay - out have been calculated without any adjustable parameters .
we have found , however , it is rather difficult to reproduce the decay - out spin for individual sd bands ( cf . figs . |
3,821 | Suppose that you have an abstract for a scientific paper: we review the structure of the moduli space of particular @xmath0 superconformal field theories .
we restrict attention to those of particular use in superstring compactification , namely those with central charge @xmath1 for some integer @xmath2 and whose ns fields have integer @xmath3 charge .
the cases @xmath4 , 2 and 3 are analyzed .
it is shown that in the case @xmath5 it is important to use techniques of algebraic geometry rather than rely on metric - based ideas .
the phase structure of these moduli spaces is discussed in some detail .
epsf # 1date_#1 _ # 1thefnmarkfootnotetext1991 _ mathematics subject classification .
_ # 1 # 1thefnmarkfootnotetext _ key words and phrases .
_ # 1 ps .
@firstpageps .
@empty oddhead evenheadoddhead ifundefinedreset@font@font footnotetext#1 # 1 o p # 1#1 # 1 # 1 # 1 # 1 # 1#2 # 1#2_#1f_#2 # 1#1 # 1#1 _ # 1@xmath6 0 1.5 cm .
And you have already written the first three sentences of the full article: as well as applications to statistical physics , conformal field theory has proved to be a very powerful tool in string theory . in particular , the ground state of a critical string corresponds to a conformal field theory with a specific central charge .
it is of particular interest to classify all such ground states which can therefore be done by finding the space of all conformal field theories of a given central charge .
this `` moduli space '' forms the space of string vacua and may be considered as the stringy analogue of the space of einstein metrics in general relativity ..
Please generate the next two sentences of the article | the moduli space of conformal field theories thus gives rise to two immediate applications .
firstly one may try to gain an understanding of stringy effects in quantum gravity by comparing the moduli space of conformal field theories with the space of einstein metrics for a given class of backgrounds . |
3,822 | Suppose that you have an abstract for a scientific paper: strong ( @xmath0 g ) and superstrong ( @xmath1 g ) magnetic fields profoundly affect many thermodynamic and kinetic characteristics of dense plasmas in neutron star envelopes .
in particular , they produce strongly anisotropic thermal conductivity in the neutron star crust and modify the equation of state and radiative opacities in the atmosphere , which are major ingredients of the cooling theory and spectral atmosphere models . as a result
, both the radiation spectrum and the thermal luminosity of a neutron star can be affected by the magnetic field .
we briefly review these effects and demonstrate the influence of magnetic field strength on the thermal structure of an isolated neutron star , putting emphasis on the differences brought about by the superstrong fields and high temperatures of magnetars .
for the latter objects , it is important to take proper account of a combined effect of the magnetic field on thermal conduction and neutrino emission at densities @xmath2 g @xmath3 .
we show that the neutrino emission puts a @xmath4-dependent upper limit on the effective surface temperature of a cooling neutron star . .
And you have already written the first three sentences of the full article: thermal emission from neutron stars can be used to measure the magnetic field , temperature , and composition of neutron - star envelopes , and to constrain the properties of matter under extreme conditions ( see , e.g. , @xcite , and references therein ) . to achieve these goals
, one should use reliable models of the atmosphere or condensed surface , where the thermal spectrum is formed , and of deeper layers , which provide thermal insulation of hot stellar interiors . in these layers , the effects of strong magnetic fields can be important . in recent years , significant progress has been achieved in the theoretical description of neutron - star envelopes with strong magnetic fields , but new challenges are put forward by observations of magnetars . in sect .
[ sect:1 ] we briefly overview recent work on the construction of models of neutron star atmospheres with strong magnetic fields and on the modeling of spectra of thermal radiation formed in an atmosphere or at a condensed surface ..
Please generate the next two sentences of the article | we list important unsolved theoretical problems which arise in this modeling . in sect .
[ sect:2 ] , after a brief review of the effects of strong magnetic fields on the thermal structure and effective temperature of neutron stars , we describe our new calculations of the thermal structure . |
3,823 | Suppose that you have an abstract for a scientific paper: we construct operators that describe power corrections in mixed collinear - ultrasoft processes in qcd .
we treat the ultrasoft - collinear lagrangian to @xmath0 , and heavy - to - light currents involving collinear quarks to @xmath1 including new three body currents .
a complete gauge invariant basis is derived which has a full reduction in dirac structures and is valid for matching at any order in @xmath2 .
the full set of reparameterization invariance ( rpi ) constraints are included , and are found to restrict the number of parameters appearing in wilson coefficients and rule out some classes of operators . the qcd ultrasoft - collinear lagrangian has two @xmath3 operators in its gauge invariant form . for the @xmath4 heavy - to - light currents there are @xmath5 subleading ( scalar , pseudo - scalar , vector , axial - vector , tensor ) currents , where @xmath6 have coefficients that are not determined by rpi .
in a frame where @xmath7 and @xmath8 the total number of currents reduces to @xmath9 , but the number of undetermined coefficients is the same .
the role of these operators and universality of jet functions in the factorization theorem for heavy - to - light form factors is discussed . .
And you have already written the first three sentences of the full article: the soft - collinear effective theory ( scet ) constructed in @xcite offers a systematic description of processes involving energetic particles .
it has an expansion in a small parameter @xmath10 , where @xmath11 is a typical transverse momenta and @xmath12 the large energy scale .
hard exclusive and inclusive processes in qcd are usually described using the powerful techniques of qcd factorization and light - cone expansions @xcite ..
Please generate the next two sentences of the article | scet encompasses and extends these frameworks , and in particular allows a model independent description of effects caused by the interplay between energetic collinear particles and soft particles beyond leading order in the power expansion .
these effects can be described in a rigorous way based solely on qcd , but are not included in purely collinear expansions . |
3,824 | Suppose that you have an abstract for a scientific paper: the monotonic increase of the radius of low mass stars during their ascent on the red giant branch halts when they suffer a temporary contraction .
this occurs when the hydrogen burning shell reaches the discontinuity in hydrogen content left from the maximum increase in the convective extension , at the time of the first dredge up , and produces a well known bump " in the luminosity function of the red giants of globular clusters .
if the giant is the mass losing component in a binary in which mass transfer occurs on the nuclear evolution time scale , this event produces a temporary stop in the mass transfer , which we will name bump related " detachment .
if the accreting companion is a neutron star , in which the previous mass transfer has spun up the pulsar down to millisecond periods , the subsequent mass transfer phase may be altered by the presence of the energetic pulsar .
in fact , the onset of a radio ejection phase produces loss of mass and angular momentum from the sytem .
we show that this sequence of events may be at the basis of the shortage of systems with periods between @xmath0 and @xmath1 days in the distribution of binaries containing millisecond pulsars .
we predict that systems which can be discovered at periods into the gap should have preferentially either magnetic moments smaller than @xmath2g@xmath3 , or larger than @xmath4g@xmath3 .
we further show that this period gap should not be present in population ii . .
And you have already written the first three sentences of the full article: the basic evolution of low mass x
ray binaries above the ` bifurcation period ' @xcite has been often described ( e.g. * ? ? ?
the endpoint of this evolution is a wide system ( orbital period from a few to hundreds of days ) containing a millisecond pulsar ( msp , the neutron star primary of initial mass m@xmath5 spun up by mass transfer from the secondary , of initial mass m@xmath6 ) and a low mass helium white dwarf , remnant helium core of the mass losing red giant ..
Please generate the next two sentences of the article | the simple relation connecting the giant stellar radius with the helium core mass of the star , which has a very slight dependence on the stellar mass and on the chemical composition , coupled with the kepler law , produces a relation between the final white dwarf mass and the final , which has been often studied ( e.g. * ? ? ? * ; * ? ? ? * ; * ? ? ? * ) and compared with the vs. distribution of the more than 60 known msps .
the sample of binary msp known up today shows a shortage of systems with orbital periods between 22 and 56 days . |
3,825 | Suppose that you have an abstract for a scientific paper: we perform the stastistics of temperature maxima and minima in cobe - dmr 2-year maps . for power - law
spectra the surface distribution of peaks implies an amplitude consistent with more conventional analyses of cobe data ( for instance , we get @xmath0k for a spectral index @xmath1 but not with the measured quadrupole @xmath2k .
this provides further support for the existence an infrared cutoff in the cosmic spectrum . .
And you have already written the first three sentences of the full article: the cobe experiment ( bennet et al . 1992 , 1994 ; smoot et al . 1992 ) has stimulated a considerable amount of work on cosmic structure .
current tests usually exploit the angular correlation function and several harmonic amplitudes of the sky temperature field ( see e.g , adams et al .
1992 ; kashlinsky 1992 ; efstathiou et al . 1992 ; kofmann et al . 1993 ; gorski et al . 1994 ) ..
Please generate the next two sentences of the article | however , several more tests have been suggested over the years for a thorough investigation of the properties of the anisotropy field of the cosmic background radiation .
these often involve the distribution and features of hot and cold spots , which can provide useful checks of the gaussian nature of the fluctuations ( sazhin 1985 ; bond & efstathiou 1987 ; coles & barrow 1987 ; coles 1988 ; martnez - gonzlez & sanz 1989 ; gott et al . |
3,826 | Suppose that you have an abstract for a scientific paper: photoexcitation of the nucleon is studied in the framework of the constituent quark model with nonrelativistic quark - quark interactions . utilizing the dominance of the pairwise structure of the relevant three - quark potential ,
the bound and excited state wave functions have been constructed using the faddeev - type integrodifferential equation approach .
the method is based on the hyperspherical harmonics expansion and takes two - body correlations exactly into account and therefore reliable wave functions , required in photo processes , can be obtained .
the integrated photoabsorption cross sections for the @xmath0 and @xmath1 transitions are calculated and compared with experimental values as well as with those of other theoretical calculations .
our results , in overall , are in good to very good agreement with the experimental values . .
And you have already written the first three sentences of the full article: in the nonrelativistic constituent quark model for mesons and baryons the quarks are bound by confining potentials . despite their limitations and concerns about their validity
, these potential models describe the properties of the various mesons and baryons surprisingly well ( see , for example , silvestre - brac @xcite and the two excellent review articles by lucha et al .
@xcite and richard @xcite on the matter ) ..
Please generate the next two sentences of the article | once the potential model approach is adopted , the three - quark problem can be solved using various approaches . among them
, the hyperspherical harmonics ( hh ) method is quite successful in applications as it is well suited to describe radial and orbital excitations @xcite . within the framework of the hh method |
3,827 | Suppose that you have an abstract for a scientific paper: we present a method to search for transient gws using a network of detectors with different spectral and directional sensitivities : the interferometer virgo and the bar detector auriga .
the data analysis method is based on the measurements of the correlated energy in the network by means of a weighted cross - correlation . to limit the computational load ,
this coherent analysis step is performed around time - frequency coincident triggers selected by an excess power event trigger generator tuned at low thresholds .
the final selection of gw candidates is performed by a combined cut on the correlated energy and on the significance as measured by the event trigger generator .
the method has been tested on one day of data of auriga and virgo during september 2005 .
the outcomes are compared to the results of a stand - alone time - frequency coincidence search .
we discuss the advantages and the limits of this approach , in view of a possible future joint search between auriga and one interferometric detector . .
And you have already written the first three sentences of the full article: we present a study on the performances of a gravitational wave ( gw ) observatory composed by a hybrid network of detectors .
in particular , we focus on the possibility to use a resonant detector to perform gw observations with one interferometric detector .
this could be an opportunity in the scenario after ligo s5 run and the first virgo science run , when most of the interferometers will be shut down for upgrading : current plans are that geo will be kept in operation till the start of the ligo s6 and the second virgo science runs , supported by ligo hanford 2k detector over weekends . in this sense , we present a case study on joint observations between auriga and virgo on a test period of 24 hrs . in the past years.
Please generate the next two sentences of the article | , various searches for gw signals have been independently performed by networks of resonant bars @xcite or interferometers @xcite .
there have been also some attempts to perform burst searches among detectors with different spectral sensitivity and orientation : by tama and the ligo scientific collaboration ( lsc ) @xcite , by auriga and the lsc @xcite and by the infn bars and the virgo collaboration @xcite . |
3,828 | Suppose that you have an abstract for a scientific paper: we present deep spectroscopic and imaging data of the host galaxies of mrk1014 , iras07598 + 6508 , and mrk231 .
these objects form part of both the qso and the ultraluminous infrared galaxy ( ulig ) families , and may represent a transition stage in an evolutionary scenario .
our imaging shows that all three objects have highly perturbed hosts with tidal tails and destroyed disks , and appear to be in the final stages of major mergers .
the host galaxies of the three objects have spectra typical of e+a galaxies , showing simultaneously features from an old and a young stellar component .
we model spectra from different regions of the host galaxies using @xcite spectral synthesis models using two component models including an old underlying population and recent superposed starbursts .
mrk1014 has intense star formation concentrated in a large knot @xmath0 kpc from the nucleus , along the leading edge of the tidal tail , and in several knots scattered around the host .
the starburst ages in these regions range from 180 to 290 myr .
iras 07598 + 6508 has multiple knots of star formation concentrated in two regions within 16 kpc of the qso nucleus , with ages ranging from 30 to 70 myr ; the host galaxy shows an older population in other regions .
mrk231 shows a wider range of starburst ages , ranging from 42 myr in the arc 3 kpc south of the nucleus , to @xmath1 myr spread on a `` plateau '' @xmath2 kpc across around the nucleus , as well as a uv bright region 12 kpc south of the nucleus , which is apparently a region of currently active star formation .
our results indicate a strong connection between interactions and vigorous bursts of star formation in these objects .
we propose that the starburst ages found are indicative of young ages for the qso activity .
the young starburst ages found are also consistent with the intermediate position of these objects in the far infrared color - color diagram . .
And you have already written the first three sentences of the full article: there has long been considerable circumstantial evidence that at least some luminous , low - redshift qsos are the result of strong interactions or mergers of galaxies ( _ e.g. , _ * ? ? ?
* ; * ? ? ?
* ; * ? ? ?.
Please generate the next two sentences of the article | * ; * ? ? ?
* ; * ? ? ? |
3,829 | Suppose that you have an abstract for a scientific paper: the eccentricity distribution of exoplanets is known from radial velocity surveys to be divergent from circular orbits beyond 0.1 au .
this is particularly the case for large planets where the radial velocity technique is most sensitive .
the eccentricity of planetary orbits can have a large effect on the transit probability and subsequently the planet yield of transit surveys .
the kepler mission is the first transit survey that probes deep enough into period - space to allow this effect to be seen via the variation in transit durations .
we use the kepler planet candidates to show that the eccentricity distribution is consistent with that found from radial velocity surveys to a high degree of confidence .
we further show that the mean eccentricity of the kepler candidates decreases with decreasing planet size indicating that smaller planets are preferentially found in low - eccentricity orbits .
planetary systems techniques : photometric radial velocities .
And you have already written the first three sentences of the full article: planets discovered using the radial velocity ( rv ) method have dominated the total exoplanet count until recently , when the transit method has made increasing contributions .
the long time baseline of rv surveys has allowed the detection more diverse orbital geometries than achievable by ground - based transit surveys .
the kepler mission , however , with its multi - year baseline , can begin to probe into parameter space previously reserved for rv studies . at longer periods ,.
Please generate the next two sentences of the article | orbits tend to diverge significantly from the circular case beyond a semi - major axis of @xmath0 au @xcite , although there may be small observational biases that skew this distribution @xcite .
this insight has led to numerous attempts to account for eccentricity in the context of planet formation and orbital stability @xcite and the influence of tidal circularization @xcite . |
3,830 | Suppose that you have an abstract for a scientific paper: in this paper we study the quantum cosmology of homogeneous and isotropic cosmology , via the weyl - wigner - groenewold - moyal formalism of phase space quantization , with perfect fluid as a matter source .
the corresponding quantum cosmology is described by the moyal - wheeler - dewitt equation which has exact solutions in moyal phase space , resulting in wigner quasiprobability distribution functions peaking around the classical paths for large values of scale factor .
we show that the wigner functions of these models are peaked around the non - singular universes with quantum modified density parameter of radiation .
+ + keywords : quantum cosmology , moyal - wheeler - dewitt equation , deformation quantization .
And you have already written the first three sentences of the full article: the main prediction of the quantum state of the universe is the emergence of classical universe that is a manifest fact of the observable universe .
therefore , predicting classical cosmology is a constraint on the theory of the state @xcite . in minisuperspace models of cosmology , the classical gravitational field equations are
often non - linear and the quantization procedure is not unique ..
Please generate the next two sentences of the article | there are infinite number of transformations that recast such equations into forms with different finite number of degree of freedom interpretations .
distinctly an appropriate transformation , state and quantization should be those that have some chance of yielding a classical limit not too far removed the original classical predictions @xcite . by canonical quantization of gravity , |
3,831 | Suppose that you have an abstract for a scientific paper: centrifugal acceleration of charged test particles at the base of a rotating jet magnetosphere is considered .
based on an analysis of forces we derive the equation for the radial accelerated motion and present an analytical solution . it is shown that for particles moving outwards along rotating magnetic field lines , the energy gain is in particular limited by the breakdown of the bead - on - the - wire approximation which occurs in the vicinity of the light cylinder @xmath0 .
the corresponding upper limit for the maximum lorentz factor @xmath1 for electrons scales @xmath2 , with @xmath3 the magnetic field strength at @xmath0 , and is at most of the order of a @xmath4 for the conditions regarded to be typical for bl lac objects .
such values suggest that this mechanism may provide pre - accelerated seed particles which are required for efficient fermi - type particle acceleration at larger scales in radio jets . .
And you have already written the first three sentences of the full article: rotating magnetospheres are widely believed to be responsible for the relativistic jet phenomenon in active galactic nuclei ( agn ) @xcite .
here we adress the question whether centrifugal acceleration of charged test particles at the base of such a jet magnetosphere may possibly produce a seed population of relativistic electrons which is required for efficient particle acceleration . for , in order to explain the origin of the nonthermal emission extending up to tev energies in some blazars ,
several acceleration processes have been proposed among which fermi - type particle acceleration mechanisms ( i.e. diffusive shock acceleration @xcite ) are quite promising ..
Please generate the next two sentences of the article | however such kind of mechanisms require a pre - accelerated seed population of electrons with lorentz factors of the order of @xmath5 @xcite .
it seems therefore quite interesting whether in the case of agn centrifugal acceleration by rotating jet magnetosphere may potentially fill this gap by providing pre - accelerated seed particles . for an analytical treatment , |
3,832 | Suppose that you have an abstract for a scientific paper: coherent optical phonons in bulk solid system play a crucial role in understanding and designing light - matter interactions and can be detected by the transient - reflectivity measurement . in this paper , we demonstrate spectrally resolved detection of coherent optical phonons in diamond from ultrashort infrared pump - probe measurements using optical band - pass filters .
we show that this enhances the sensitivity approximately @xmath0 times in measuring the coherent oscillations in the transient reflectivity compared with the commonly used spectrally integrated measurement .
to explain this observation , we discuss its mechanism . .
And you have already written the first three sentences of the full article: ultrashort optical pulses generate the coherent oscillation of the lattice , which modulates the macroscopic electric susceptibility .
these lattice oscillations are referred to as coherent phonons and can be detected with another ultrashort pulse via intensity modulations in reflectivity or transmissivity @xcite . using coherent phonons and a pump - probe type optical measurement
, we can directly observe the oscillation of the phonons and measure their dynamics for a wide variety of materials such as semimetals @xcite , semiconductors @xcite , superconductors @xcite and topological insulators @xcite ..
Please generate the next two sentences of the article | in addition , the coherent phonons in carbon materials , e.g. , graphite @xcite , graphene @xcite , and carbon nanotubes @xcite , have attracted much attention in studies of electron - phonon coupling . to excite and measure the coherent phonons , the pulse duration of the pump and probe pulse needs to be shorter than the vibrational period of the phonons .
this requirement corresponds to a spectral width of the optical pulse that is much bigger than the phonon energy . |
3,833 | Suppose that you have an abstract for a scientific paper: using a high - resolution cosmological @xmath0-body simulation , we identify the ejected population of subhalos , which are halos at redshift @xmath1 but were once contained in more massive ` host ' halos at high redshifts .
the fraction of the ejected subhalos in the total halo population of the same mass ranges from 9% to 4% for halo masses from @xmath2 to @xmath3 .
most of the ejected subhalos are distributed within 4 times the virial radius of their hosts .
these ejected subhalos have distinct velocity distribution around their hosts in comparison to normal halos . the number of subhalos ejected from a host of given mass increases with the assembly redshift of the host .
ejected subhalos in general reside in high - density regions , and have a much higher bias parameter than normal halos of the same mass .
they also have earlier assembly times , so that they contribute to the assembly bias of dark matter halos seen in cosmological simulations . however , the assembly bias is _ not _ dominated by the ejected population , indicating that large - scale environmental effects on normal halos are the main source for the assembly bias .
[ firstpage ] dark matter - large - scale structure of the universe - galaxies : haloes - methods : statistical .
And you have already written the first three sentences of the full article: in the standard cold dark matter ( cdm ) paradigm of structure formation , galaxies are supposed to form and evolve in dark matter halos .
the study of the clustering properties of dark matter halos and their relation to galaxy clustering can thus help us to understand the connection between halos and galaxies , and hence to understand how galaxies form and evolve in dark matter halos .
it is now well known that the correlation strength of dark matter halos depends strongly on halo mass ( e.g. , mo & white 1996 ; mo et al ..
Please generate the next two sentences of the article | 1997 ; jing 1998 ; sheth & tormen 1998 ; sheth , mo & tormen 2001 ; seljak & warren 2004 ) , and this dependence , which is referred to as the halo bias , has been widely used to understand the clustering of galaxies via the halo occupation model ( e.g. , jing , mo & brner 1998 ; peacock & smith 2000 ) , and the conditional luminosity function model ( e.g. , yang , mo & van den bosch 2003 ) .
more recently , a number of independent investigations have shown that the halo bias depends not only on the mass but also assembly time of dark matter halos , in the sense that halos of a given mass , particularly low - mass ones , are more strongly correlated if they assembled half of their masses earlier ( e.g. gao et al . |
3,834 | Suppose that you have an abstract for a scientific paper: dual supermassive black holes ( smbhs ) with kiloparsec scale separations in merger - remnant galaxies are informative tracers of galaxy evolution , but the avenue for identifying them in large numbers for such studies is not yet clear .
one promising approach is to target spectroscopic signatures of systems where both smbhs are fueled as dual active galactic nuclei ( agns ) , or where one smbh is fueled as an offset agn .
dual agns may produce double - peaked narrow agn emission lines , while offset agns may produce single - peaked narrow agn emission lines with line - of - sight velocity offsets relative to the host galaxy .
we search for such dual and offset systems among 173 type 2 agns at @xmath0 in the agn and galaxy evolution survey ( ages ) , and we find two double - peaked agns and five offset agn candidates .
when we compare these results to a similar search of the deep2 galaxy redshift survey and match the two samples in color , absolute magnitude , and minimum velocity offset , we find that the fraction of agns that are dual smbh candidates increases from @xmath1 to @xmath2 by a factor of @xmath3 ( from 2/70 to 16/91 , or @xmath4 to @xmath5 ) . this may be associated with the rise in the galaxy merger fraction over the same cosmic time . as further evidence for a link with galaxy mergers ,
the ages offset and dual agn candidates are tentatively @xmath6 times more likely than the overall agn population to reside in a host galaxy that has a companion galaxy ( from 16/173 to 2/7 , or @xmath7 to @xmath8 ) .
follow - up observations of the seven offset and dual agn candidates in ages will definitively distinguish velocity offsets produced by dual smbhs from those produced by narrow - line region kinematics , and will help sharpen our observational approach to detecting dual smbhs . .
And you have already written the first three sentences of the full article: a merger between two galaxies , each with its own central supermassive black hole ( smbh ) , results in a merger - remnant galaxy hosting two smbhs . as these smbhs orbit in the potential of the host galaxy , they are dragged closer together by dynamical friction from the surrounding stars , form a gravitationally - bound binary system , and ultimately merge @xcite . while the smbhs are at kiloparsec ( kpc ) scale separations , before they are bound as a binary system , they are known as dual smbhs .
gas churned up by the galaxy merger may accrete onto the dual smbhs , and cases where one or both of the smbhs fuel active galactic nuclei ( agns ) are known as offset agns and dual agns , respectively .
these offset and dual agns , which we refer to here as having separations @xmath9 kpc , have valuable potential as new observational tools for studies of galaxy evolution , including measurements of galaxy merger rates , smbh mass growth , and smbh merger rates . however ,.
Please generate the next two sentences of the article | because of their small spatial separations from the host galaxy centers , offset and dual agns are challenging to identify . as a consequence , early discoveries of offset agns and dual agns were serendipitous @xcite . while ultra - hard x - rays have been used to uncover a handful of dual agns @xcite , serendipitous discoveries of dual agn candidates continue today ( e.g. , @xcite ) . to accelerate the discovery rate of offset and dual agns , a new systematic approach was developed to identify candidates in spectroscopic surveys of galaxies .
this technique uses galaxy spectra to select offset and dual agn candidates as narrow agn emission lines with line - of - sight velocity offsets of a few hundred km s@xmath10 relative to the host galaxy stellar absorption features . |
3,835 | Suppose that you have an abstract for a scientific paper: we count the @xmath0-rational points of git quotients of quiver representations with relations .
we focus on two types of algebras
one is one - point extended from a quiver @xmath1 , and the other is the dynkin @xmath2 tensored with @xmath1 . for both
, we obtain explicit formulas .
we study when they are polynomial - count .
we follow the similar line as in the first paper but algebraic manipulations in hall algebra will be replaced by corresponding geometric constructions .
[ multiblock footnote omitted ] .
And you have already written the first three sentences of the full article: we continue our development on algorithms to count the points of various representation varieties of a quiver with relations . in @xcite
, we applied serval counting characters to the harder - narasimhan identity in the hall algebra of a quiver and obtained several interesting formulas .
all characters that we considered are originated from reineke s counting character @xmath3 from the hall algebra to certain quantum power series ring ..
Please generate the next two sentences of the article | unfortunately @xmath3 fails to be an algebra morphism for non - hereditary algebras , though harder - narasimhan identity exists quite generally .
however , applying the same map @xmath3 to the hn - identity can still generate effective counting formulas . |
3,836 | Suppose that you have an abstract for a scientific paper: grb 000926 has one of the best - studied afterglows to - date , with multiple x - ray observations , as well as extensive multi - frequency optical and radio coverage .
broadband afterglow observations , spanning from x - ray to radio frequencies , provide a probe of the density structure of the circumburst medium , as well as of the ejecta energetics , geometry , and the physical parameters of the relativistic blastwave resulting from the explosion .
we present an analysis of _ chandra x - ray observatory _ observations of this event , along with _
hubble space telescope _ and radio monitoring .
we combine these data with ground - based optical and ir observations and fit the synthesized afterglow lightcurve using models where collimated ejecta expand into a surrounding medium .
we find that we can explain the broadband lightcurve with reasonable physical parameters if the cooling is dominated by inverse compton scattering .
for this model , an excess due to inverse compton scattering appears above the best - fit synchrotron spectrum in the x - ray band .
no previous bursts have exhibited this component , and its observation would imply that the grb exploded in a moderately dense ( @xmath0 @xmath1 ) medium , consistent with a diffuse interstellar cloud environment . .
And you have already written the first three sentences of the full article: broadband observations of gamma - ray burst afterglows can in principle be used to constrain fundamental physical parameters of the explosion . in the fireball model
, a relativistic blast wave expands into the surrounding medium , its hydrodymanical evolution being strongly influenced by the density structure of the medium as well as by the energy content and geometry ( in particular collimation ) of the ejecta .
the temporal behavior of the afterglow emission which arises from the shocked gas depends on the shock evolution , and the partition of energy between the magnetic field and relativistic electrons , and can therefore probe these physical parameters given data of sufficient quality . in this paper , we report the synthesized results from our multi - frequency followup campaign on the relatively bright grb 000926 ..
Please generate the next two sentences of the article | this campaign was aimed at studying the evolution of the afterglow to constrain the model parameters described above .
@xcite have reported the results from our multi - band ( @xmath2 ) optical monitoring . |
3,837 | Suppose that you have an abstract for a scientific paper: in this paper , we propose two important measures , quantile correlation ( qcor ) and quantile partial correlation ( qpcor ) .
we then apply them to quantile autoregressive ( qar ) models , and introduce two valuable quantities , the quantile autocorrelation function ( qacf ) and the quantile partial autocorrelation function ( qpacf ) .
this allows us to extend the classical box - jenkins approach to quantile autoregressive models .
specifically , the qpacf of an observed time series can be employed to identify the autoregressive order , while the qacf of residuals obtained from the fitted model can be used to assess the model adequacy .
we not only demonstrate the asymptotic properties of qcor , qpcor , qacf , and pqacf , but also show the large sample results of the qar estimates and the quantile version of the ljung - box test .
simulation studies indicate that the proposed methods perform well in finite samples , and an empirical example is presented to illustrate usefulness
. _ keywords and phrases : _ autocorrelation function ; box - jenkins method ; quantile correlation ; quantile partial correlation ; quantile autoregressive model .
And you have already written the first three sentences of the full article: in the last decade , quantile regression has attracted considerable attention .
there are two major reasons for such popularity .
the first is that quantile regression estimation @xcite can be robust to non - gaussian or heavy - tailed data ..
Please generate the next two sentences of the article | in addition , it includes the commonly used least absolute deviation ( lad ) method as a special case .
the second is that the quantile regression model allows practitioners to provide more easily interpretable regression estimates obtained via various quantiles @xmath0 $ ] . |
3,838 | Suppose that you have an abstract for a scientific paper: recent studies regarding the habitability , observability , and possible orbital evolution of the indirectly detected exoplanet proxima b have mostly assumed a planet with @xmath0 @xmath1 , a rocky composition , and an earth - like atmosphere or none at all . in order to assess these assumptions , we use previous studies of the radii , masses , and compositions of super - earth exoplanets to probabilistically constrain the mass and radius of proxima b , assuming an isotropic inclination probability distribution .
we find it is @xmath2 likely that the planet s density is consistent with a rocky composition ; conversely , it is at least @xmath3 likely that the planet has a significant amount of ice or an h / he envelope .
if the planet does have a rocky composition , then we find expectation values and 95% confidence intervals of @xmath4 @xmath1 for its mass and @xmath5 @xmath6 for its radius . .
And you have already written the first three sentences of the full article: the recent radial velocity detection of a planet in the habitable zone of the nearby m dwarf proxima centauri ( hereafter proxima b and proxima ) @xcite has spurred over a dozen theoretical papers speculating on the planet s atmosphere ( e.g. , * ? ? ?
* ; * ? ? ?
* ) , habitability ( e.g. , * ? ? ?.
Please generate the next two sentences of the article | * ; * ? ? ?
* ) , and orbital and formation histories ( e.g. , * ? ? ? |
3,839 | Suppose that you have an abstract for a scientific paper: we consider continuous time random walks ( ctrw ) for open systems that exchange energy and matter with multiple reservoirs . each waiting time distribution ( wtd ) for times between steps
is characterized by a positive parameter @xmath0 , which is set to @xmath1 if it decays at least as fast as @xmath2 at long times and therefore has a finite first moment .
a wtd with @xmath3 decays as @xmath4 .
a fluctuation theorem for the trajectory quantity @xmath5 , defined as the logarithm of the ratio of the probability of a trajectory and the probability of the time reversed trajectory , holds for any ctrw .
however , @xmath5 can be identified as a trajectory entropy change only if the wtds have @xmath1 and satisfy separability ( also called direction time independence " ) . for nonseparable wtds with @xmath1 , @xmath5
can only be identified as a trajectory entropy change at long times , and a fluctuation theorem for the entropy change then only holds at long times . for wtds with @xmath6
no meaningful fluctuation theorem can be derived .
we also show that the ( experimentally accessible ) @xmath7th moments of the energy and matter transfers between the system and a given reservoir grow as @xmath8 at long times . .
And you have already written the first three sentences of the full article: it has long been clearly understood that the statement of the second law of thermodynamics concerning the increase in entropy in an isolated system as it goes to equilibrium refers only to the average behavior , but this was sufficient as long as one dealt only with macroscopic systems characterized by extremely narrow ensemble distributions with fluctuations that were essentially never observed .
more recently , with the ability to quantitatively monitor systems on the extremely small scales of single molecules and quantum dots , it is possible to study fluctuations around the average behavior . _ fluctuation theorems _ that hold arbitrarily far from equilibrium have thus become subject to experimental verification @xcite .
these theorems in general deal with the ratio of the probabilities of a given system trajectory and that of its time reversed trajectory , either as the system goes to equilibrium or as it evolves to a steady state under the action of nonequilibrium constraints imposed on the system . from this one can calculate , for example , the relative probabilities that the entropy of an isolated system away from thermodynamic equilibrium will spontaneously increase or decrease over a given period of time ..
Please generate the next two sentences of the article | the ratio is essentially infinite in a macroscopic system away from equilibrium and is unity due to fluctuations in equilibrium , but in sufficiently small systems away from equilibrium it is merely large ( and experimentally accessible ) rather than infinite .
fluctuation theorems can take different forms depending on the specific problem under consideration , but they are all ultimately connected to the probabilistic asymmetry of system trajectories and time reversed trajectories . |
3,840 | Suppose that you have an abstract for a scientific paper: we present a simultaneous detection of gravitational magnification and dust reddening effects due to galactic halos and large - scale structure .
the measurement is based on correlating the brightness of @xmath085,000 quasars at @xmath1 with the position of 20 million galaxies at @xmath2 derived from the sloan digital sky survey and is used to constrain the galaxy - mass and galaxy - dust correlation functions up to cosmological scales .
the presence of dust is detected from 20 kpc to several mpc , and we find its projected density to follow : @xmath3 , a distribution similar to mass .
the amount of dust in galactic halos is found to be comparable to that in disks . on large scales
its wavelength dependence is described by @xmath4 , consistent with interstellar dust .
we estimate the resulting opacity of the universe as a function of redshift and find @xmath5 mag up to @xmath6 .
this , in turn , implies a cosmic dust density of @xmath7 , roughly half of which comes from dust in halos of @xmath8 galaxies .
we present magnification measurements , corrected for dust extinction , from which the galaxy - mass correlation function is inferred . the mean mass profile around galaxies is found to be @xmath9 up to a radius of 10 mpc , in agreement with gravitational shear estimates .
dust extinction , reddening
dark matter magnification large - scale structures quasars galaxies .
And you have already written the first three sentences of the full article: light rays from distant sources carry unique information about the matter and gravitational potential along the line - of - sight .
a well - known example is the signature of intervening gas clouds imprinted into spectra of background sources via absorption lines .
mass concentrations located along the path of photons can also induce gravitational lensing effects ..
Please generate the next two sentences of the article | background sources can be magnified , as detected by @xcite , and galaxy shapes can be distorted as measured through galaxy - galaxy lensing ( cf .
@xcite , @xcite , @xcite , @xcite ) and cosmic shear ( e.g. ) . |
3,841 | Suppose that you have an abstract for a scientific paper: new bandwidth selectors for kernel density estimation with directional data are presented in this work .
these selectors are based on asymptotic and exact error expressions for the kernel density estimator combined with mixtures of von mises distributions .
the performance of the proposed selectors is investigated in a simulation study and compared with other existing rules for a large variety of directional scenarios , sample sizes and dimensions .
the selector based on the exact error expression turns out to have the best behaviour of the studied selectors for almost all the situations .
this selector is illustrated with real data for the circular and spherical cases .
* keywords : * bandwidth selection ; directional data ; mixtures ; kernel density estimator ; von mises . .
And you have already written the first three sentences of the full article: bandwidth selection is a key issue in kernel density estimation that has deserved considerable attention during the last decades .
the problem of selecting the most suitable bandwidth for the nonparametric kernel density estimator introduced by @xcite and @xcite is the main topic of the reviews of @xcite , @xcite and @xcite , among others .
comprehensive references on kernel smoothing and bandwidth selection include the books by @xcite , @xcite and @xcite ..
Please generate the next two sentences of the article | bandwidth selection is still an active research field in density estimation , with some recent contributions like @xcite and @xcite in the last years . + kernel density estimation has been also adapted to directional data , that is , data in the unit hypersphere of dimension @xmath0 .
due to the particular nature of directional data ( periodicity for @xmath1 and manifold structure for any @xmath0 ) , the usual multivariate techniques are not appropriate and specific methodology that accounts for their characteristics has to be considered . |
3,842 | Suppose that you have an abstract for a scientific paper: we derive the frequency shifts and the broadening of @xmath0 point longitudinal optical ( lo ) and transverse optical ( to ) phonon modes , due to electron - phonon interaction , in graphene under uniaxial strain as a function of the electron density and the disorder amount .
we show that , in the absence of a shear strain component , such interaction gives rise to a lifting of the degeneracy of the lo and to modes which contributes to the splitting of the g raman band .
the anisotropy of the electronic spectrum , induced by the strain , results in a polarization dependence of the lo and to modes .
this dependence is in agreement with the experimental results showing a periodic modulation of the raman intensity of the splitted g peak .
moreover , the anomalous behavior of the frequency shift reported in undeformed graphene is found to be robust under strain . .
And you have already written the first three sentences of the full article: since its discovery in 2004 @xcite , graphene continues to be the subject of intense interest regarding its exotic properties @xcite .
these intriguing properties , such as the anomalous quantum hall effect , are ascribed to dirac type electrons described by the weyl s equation for massless particles @xcite .
the electronic properties in graphene are significantly affected by applying a strain @xcite ..
Please generate the next two sentences of the article | the latter can also , accidentally , occur during the fabrication process as in exfoliation or chemical vapor deposition of graphene samples @xcite .
theoretical and first principle calculations revealed the substantial effect of the strain on the electronic and lattice spectra of graphene @xcite . to bring out the signature of strain induced modified electronic and vibrational properties , raman spectroscopy has emerged as a powerfull probe . |
3,843 | Suppose that you have an abstract for a scientific paper: in this paper we review several approaches to mathematical modeling of simple battery cells and develop these ideas further with emphasis on charge recovery and the response behavior of batteries to given external load .
we focus on models which use few parameters and basic battery data , rather than detailed reaction and material characteristics of a specific battery cell chemistry , starting with the coupled ode linear dynamics of the kinetic battery model .
we show that a related system of pde with robin type boundary conditions arises in the limiting regime of a spatial kinetic battery model , and provide a new probabilistic representation of the solution in terms of brownian motion with drift reflected at the boundaries on both sides of a finite interval . to compare linear and nonlinear dynamics in kinetic and stochastic battery models we study markov chains with states representing available and remaining capacities of the battery .
a natural scaling limit leads to a class of nonlinear ode , which can be solved explicitly and compared with the capacities obtained for the linear models . to indicate the potential use of the modeling we discuss briefly comparison of discharge profiles and effects on battery performance .
battery lifetime ; state - of - charge ; charge recovery ; probabilistic solution of pde ; robin boundary condition ; nonlinear ode s h .
And you have already written the first three sentences of the full article: the subject of this work is mathematical modeling of state - of - charge in simple battery cells , such as a non - rechargeable 3 volts lithium coin battery .
the goal is to understand the response of the battery , and ultimately to predict battery lifetime , as energy is consumed under a given discharge usage pattern .
the main incentive for our work is the battery usage in wireless sensor networks and similar internet - of - things systems ..
Please generate the next two sentences of the article | these networks consist of inter - connected low - cost nodes , equipped with basal sensors , computer , radio and a battery , expected to run for many years under very low intensity loads and short dutycycles . within the tight cost restrictions typical of such systems , methods or techniques providing `` battery - charge indicators ''
do not seem to be within reach currently . to make progress in this direction |
3,844 | Suppose that you have an abstract for a scientific paper: = 0.6 cm * abstract * we study the greybody factor and hawking radiation for a scalar field coupling to einstein s tensor in the background of reissner - nordstrm black hole in the low - energy approximation .
we find that the presence of the coupling terms modifies the standard results in the greybody factor and hawking radiation .
our results show that both the absorption probability and hawking radiation increase with the coupling constant .
moreover , we also find that for the stronger coupling , the charge of black hole enhances the absorption probability and hawking radiation of the scalar field , which is different from those of ones without coupling to einstein s tensor in the black hole spacetime .
= 0.8 cm .
And you have already written the first three sentences of the full article: scalar field , associated with spin-@xmath0 particles in quantum field theory , has been an object of great interest for physicists in the latest years .
one of the main reasons is that the models with scalar fields are relatively simple , which allows us to probe the detailed features of the more complicated physical system . in cosmology ,
scalar fields can be considered as candidate to explain the inflation of the early universe @xcite and the accelerated expansion of the current universe @xcite . in the standard model of particle physics.
Please generate the next two sentences of the article | , the scalar field presents as the higgs boson @xcite , which would help to explain the origin of mass in the universe .
moreover , it has been found that scalar field plays the important roles in other fundamental physical theories , such as , jordan - brans - dicke theory @xcite , kaluza - klein compactification theory @xcite and superstring theory @xcite , and so on . |
3,845 | Suppose that you have an abstract for a scientific paper: we study the lattice reaction diffusion model @xmath0 , @xmath1 ( triplet creation " ) using numerical simulations and @xmath2-site approximations .
the simulation results suggest that the phase transition is discontinuous at high diffusion rates . in this regime
the order parameter appears to be a discontinuous function of the creation rate ; no evidence of a stable interface between active and absorbing phases is found .
based on an effective mapping to a modified compact directed percolation process , we shall nevertheless argue that the transition is _ continuous _ , despite the seemingly discontinuous phase transition suggested by studies of finite systems . .
And you have already written the first three sentences of the full article: the exploration of phase transitions in simple , one component nonequilibrium models has attracted considerable interest @xcite , and important steps towards identifying the related universality classes have been achieved @xcite . in nonequilibrium models phase transitions may occur even in one - dimensional systems : the well known arguments , due to landau and to van hove @xcite , against phase transitions in one - dimensional systems with short - range interactions , do not apply in the absence of detailed balance . however in low dimensions the effect of fluctuations is stronger , making continuous phase transitions more common .
( a familiar example is the three - state potts model , which exhibits a continuous transition in two dimensions , and a discontinuous one for @xmath3 . ) in one dimension , discontinuous phase transitions have been found in models with long - range interactions @xcite , or a conserved density @xcite , and in multi - component systems @xcite .
compact directed percolation ( cdp ) has a discontinuous transition between a pair of absorbing states ( all sites full or all empty ) @xcite ; a similar transition between absorbing states is found in the one - dimensional ziff - gulari - barshad model @xcite ..
Please generate the next two sentences of the article | a discontinuous transition between and active phase and an absorbing one in a single - component model was claimed for the triplet creation model ( tcm ) @xcite , which does not possess a conservation law or long - range interactions .
this model features particle reactions @xmath0 , @xmath1 and explicit diffusion ( hopping ) @xcite . on increasing the diffusion probability , a crossover from a continuous to a discontinuous phase transition |
3,846 | Suppose that you have an abstract for a scientific paper: we study thermal transport in a chain of coupled atoms , which can vibrate in longitudinal as well as transverse directions .
the particles interact through anharmonic potentials upto cubic order .
the problem is treated quantum mechanically .
we first calculate the phonon frequencies self - consistently taking into account the anharmonic interactions .
we show that for all the modes , frequencies must have linear dispersion with wave - vector @xmath0 for small @xmath0 irrespective of their bare dispersions .
we then calculate the phonon relaxation rates @xmath1 , where @xmath2 is the polarization index of the mode , in a self - consistent approximation based on second order perturbation diagrams .
we find that the relaxation rate for the longitudinal phonon , @xmath3 , while that for the transverse phonon @xmath4 .
the consequence of these results on the thermal conductivity @xmath5 of a chain of @xmath6 particles is that @xmath7 .
v#1 # 1#1^ .
And you have already written the first three sentences of the full article: in low dimensional systems , the description of transport in terms of linear phenomenological laws , that works well in three dimensions , may not be possible .
one example is the fourier law which relates the thermal current density @xmath8 to the thermal gradient @xmath9 by @xmath10 , where the @xmath11 is the thermal conductivity of the material .
theoretical investigations of a number of translation invariant one - dimensional systems show that the fourier law is not followed in these systems @xcite ..
Please generate the next two sentences of the article | the ratio of the current density to the thermal gradient is no longer independent of the system size .
nevertheless this ratio , again called ` thermal conductivity ' , is still useful in characterizing anomalous transport . |
3,847 | Suppose that you have an abstract for a scientific paper: we use a single ion as an movable electric field sensor with accuracies on the order of a few v / m . for this , we compensate undesired static electric fields in a planar rf trap and characterize the static fields over an extended region along the trap axis .
we observe a strong buildup of stray charges around the loading region on the trap resulting in an electric field of up to 1.3 kv / m at the ion position .
we also find that the profile of the stray field remains constant over a time span of a few months . .
And you have already written the first three sentences of the full article: laser cooled trapped ions offer a very high level of control , both of their motional and internal quantum states . at the same time , the large charge - to - mass ratio of ions makes their motion very sensitive to electric fields , both static and oscillatory .
thus , trapped ions recently emerged as a tool in small - force sensing@xcite .
more common applications of trapped ions are in quantum information science @xcite and frequency metrology @xcite ..
Please generate the next two sentences of the article | all these applications can benefit from scalable ion - trap architectures based on microfabricated ion traps . in particular , a promising route to achieve scalable quantum information processing uses complex electrode structures@xcite .
considerable effort is made in developing microfabricated trap architectures on which all trap electrodes lie within one plane @xcite . |
3,848 | Suppose that you have an abstract for a scientific paper: the suppression of high transverse momentum ( @xmath0 ) inclusive hadron spectra in heavy - ion collisions as compared to the scaled expectation of high @xmath0 hadron production in p - p collisions is the most direct manifestation of the interaction of hard partons with the soft bulk medium produced in heavy - ion collisions which is absent in p - p collisions . yet
the measured nuclear suppression factor @xmath1 is a very averaged quantity and hence only a limited amount of information about the medium evolution and the nature of the interaction with the medium can be deduced from @xmath1 .
measurements of hard back - to - back hadron correlations in 200 agev au - au collisions at rhic have opened a new window to study the energy loss of partons in a medium in a more differential way and for a different distribution of in - medium pathlengths than in the case of @xmath1 . in this work
, we present an extrapolation of our results for back - to - back yields at rhic energies to 5.5 tev pb - pb collisions at the cern lhc .
we also discuss differences and similarities between the measurement at rhic . .
And you have already written the first three sentences of the full article: the suppression of single inclusive high @xmath0 hadrons in heavy - ion collisions as compared to the scaled expectation from p - p collision has long been regarded as caused by energy loss of high @xmath2 partons into a dense partonic environment @xcite . at rhic ,
the nuclear suppression factor @xmath1 for pions in central au - au collisions has been measured out to 20 gev @xcite and a factor @xmath3 suppression observed .
the hope of using hard probes such as the single hadron suppression in the context of heavy - ion collisions is to infer properties of the medium and its density evolution from induced changes relative to the corresponding known hard process in p - p collisions ..
Please generate the next two sentences of the article | there is , however , growing evidence that single hadron suppression is not enough to unambiguously determine even the distribution of energy / momentum shifts of partons traversing the medium @xcite .
however , if energy loss can not be determined reliably in momentum space , there is little hope to try to infer the qcd matter density distribution in position space . |
3,849 | Suppose that you have an abstract for a scientific paper: after a brief look at the well - known standard approaches to determine the angle @xmath0 of the unitarity triangle , we focus on two kinds of strategies , employing @xmath1 modes , and @xmath2-spin - related @xmath3 decays .
interesting `` puzzles '' , which may already be indicated by the present @xmath3-factory data , are pointed out , and the importance of the extraction of hadronic parameters , which are provided by these strategies as by - products , is emphasized .
[ cols= " < " , ] in fig . [ fig1 ] , we show the dependence of ( [ const1 ] ) and ( [ const2 ] ) on @xmath0 for the neutral @xmath1 system ; the charged @xmath1 curves look very similar @xcite . here
the crossed region below the @xmath4 curve , which is described by ( [ const2 ] ) , is excluded . on the other hand ,
the shaded region is the allowed range ( [ const1 ] ) for @xmath5 , arising in the case of @xmath6 .
this figure allows us to read off immediately the allowed range for @xmath0 for a given value of @xmath5 . in order to illustrate this feature ,
let us assume that @xmath7 has been measured , which would be in accordance with the central values of cleo and belle in table [ tab1 ] . in this case , the @xmath4 curve implies @xmath8 .
if we use additional information on @xmath9 , we may put even stronger constraints on @xmath0 . for @xmath6 ,
we obtain , for instance , the allowed range @xmath10 .
it is interesting to note that the @xmath4 curve is only effective for @xmath11 .
assuming @xmath12 to illustrate implications of the cp - averaged charged @xmath1 branching ratios , ( [ const2 ] ) is not effective and @xmath13 has to be fixed in order to constrain @xmath0 .
using @xmath14 , we obtain @xmath15 .
although it is too early to draw definite conclusions , it is important to emphasize that the second quadrant for @xmath0 , i.e. @xmath16 , would be preferred in these cases .
interestingly , such a situation would be in conflict with the standard analysis of the unitarity triangle @xcite ,....
And you have already written the first three sentences of the full article: let us now focus on strategies to extract @xmath0 from pairs of @xmath3-meson decays , which are related to each other through the @xmath2-spin flavor symmetry of strong interactions . in order to deal with non - leptonic
@xmath3 decays , @xmath2-spin offers an important tool , and first approaches to extract ckm phases were already pointed out in 1993 @xcite .
however , the great power of the @xmath2-spin symmtery to determine weak phases and hadronic parameters was noticed just recently in the strategies proposed in @xcite@xcite ..
Please generate the next two sentences of the article | since these methods involve also decays of @xmath34-mesons , @xmath3 experiments at hadron colliders are required to implement them in practice . at tevatron - ii , we will have first access to the corresponding modes and interesting results are expected @xcite . in the era of btev and the lhc , the @xmath2-spin strategies can then be fully exploited @xcite , as emphasized by stone at this symposium . in the following discussion , we shall focus on two particularly promising approaches , using the @xmath35 , @xmath36 @xcite and @xmath37 , @xmath38 @xcite systems .
looking at the corresponding feynman diagrams , we observe that @xmath36 is obtained from @xmath40 by interchanging all down and strange quarks . |
3,850 | Suppose that you have an abstract for a scientific paper: in the orbitally ordered , quasi - one dimensional heisenberg antiferromagnet kcuf@xmath0 the low - energy @xmath1 and @xmath2 phonon modes show an anomalous softening ( @xmath325@xmath4 and @xmath313@xmath4 ) between room temperature and the characteristic temperature @xmath5 = 50 k. in this temperature range a freezing - in of f ion dynamic displacements is proposed to occur .
in addition , the @xmath1 mode at about 260 @xmath6 clearly splits below @xmath5 .
the width of the phonon lines above @xmath5 follows an activated behavior with an activation energy of about 50 k. our observations clearly evidence a reduction of the structural symmetry below @xmath5 and indicate a strong coupling of lattice and spin fluctuations for @xmath7 . .
And you have already written the first three sentences of the full article: the system kcuf@xmath0 has long been known as a paradigm for an orbitally ordered system where a cooperative jahn - teller ( jt ) distortion is strongly competing with the electronic degrees of freedom as the driving force behind the orbital order.@xcite this system was investigated recently by realistic band structure calculations as a benchmark system for modeling structural relaxation effects due to electronic correlations @xcite and for revealing the influence of electronic superexchange on the orbital ordering.@xcite the compound seems to be orbitally ordered throughout its solid phase , but shows long - range a - type antiferromagnetic ( afm ) ordering only below @xmath8 = 39 k. in literature an orbital ordering temperature of about 800 k is often evoked in this system , but astonishingly experimental evidence for a transition at this temperature seems to be evasive .
early on , however , it was reported that between 670 k and 720 k an irreversible transition takes place.@xcite recently , the melting of the cooperative jt - transition has been studied in kcu@xmath9mg@xmath10f@xmath0 and from the extrapolation to undoped kcuf@xmath0 a jt transition temperature of 1350 k has been estimated.@xcite the paramagnetic ( pm ) susceptibility has been described by a bonner - fisher law with an exchange constant j = 190 k,@xcite indicating that the compound is a good realization of a one - dimensional ( 1d ) spin chain in the pm regime .
inelastic neutron scattering studies did reveal a spinon - excitation continuum , a clearly 1d quantum phenomenon , existing also below the nel temperature.@xcite from a structural point of view the reported relatively high tetragonal symmetry @xcite ( @xmath11 @xmath124@xmath13 ) makes kcuf@xmath0 one of the simplest systems to study ..
Please generate the next two sentences of the article | however , the established symmetry assignment has been questioned by an x - ray diffraction investigation @xcite which suggested the existence of orthorhombic distortions in kcuf@xmath0 at room temperature with @xmath14 symmetry .
a low - temperature raman scattering study @xcite revealed a difference of spectra measured in @xmath15 and @xmath16 polarization and anomalously broad linewidths of the stretching modes , which was interpreted as evidence of a symmetry lower than @xmath11 also below the nel temperature . |
3,851 | Suppose that you have an abstract for a scientific paper: we study the structural stability and dynamical properties of ar(h@xmath0)@xmath0 under pressure using first - principles and _ ab initio _ molecular dynamics techniques . at low temperatures
, ar(h@xmath0)@xmath0 is found to stabilize in the cubic c15 laves structure ( mgcu@xmath0 ) and not in the hexagonal c14 laves structure ( mgzn@xmath0 ) as it has been assumed previously . based on enthalpy
energy and phonon calculations , we propose a temperature - induced mgcu@xmath0 @xmath1 mgzn@xmath0 phase transition that may rationalize the existing discrepancies between the sets of raman and infrared vibron measurements .
our aimd simulations suggest that the melting line of ar(h@xmath0)@xmath0 presents negative slope in the interval @xmath2 gpa .
we explain the origin of this intriguing physical phenomenon in terms of decoupling of the ar and h@xmath0 degrees of freedom and effective thermal - like excitations arising from coexisting liquid h@xmath0 and solid ar phases . .
And you have already written the first three sentences of the full article: solid hydrogen h@xmath0 is expected to become metallic at compressions higher than @xmath3 gpa [ ] . in fact , experimental signatures of the long - sought insulator - to - metal phase transition remain elusive up to pressures of @xmath4 gpa [ ] .
accepted pressure - induced mechanisms by which the metallicity of hydrogen can be enhanced involve atomization of h@xmath0 molecules and partial filling of electronic @xmath5 molecular levels due to charge transfer from or band hybridization with other chemical species [ ] .
already in the earlier 90 s loubeyre _.
Please generate the next two sentences of the article | et al . _ , based on the disappearance of the raman ( r ) vibron mode and the darkening of the material , claimed to observe metallization of the ar(h@xmath0)@xmath0 compound when compressed in the diamond - anvil - cell ( dac ) up to @xmath6 gpa [ ] .
the stable room - temperature ( rt ) phase structure of this compound was identified with the hexagonal c14 laves structure typified by the mgzn@xmath0 crystal ( space group : @xmath7 ) . |
3,852 | Suppose that you have an abstract for a scientific paper: we have obtained spectra through small apertures centered on the nuclear region and major axis of m32 , with the faint object spectrograph ( fos ) on the hubble space telescope ( hst ) . a detailed analysis and reduction of the data
is presented , including : ( i ) new calibrations and modeling of the fos aperture sizes , point - spread - function and line - spread - functions ; ( ii ) determination of the aperture positioning for each observation from the observed count rate ; and ( iii ) accurate wavelength calibration , template matching , and kinematical analysis of the spectra .
this yields measurements of the stellar rotation velocities and velocity dispersions near the center of m32 , with five times higher spatial resolution than the best available ground - based data .
the inferred velocities provide the highest angular resolution stellar kinematical data obtained to date for any stellar system .
the hst observations show a steeper rotation curve and higher central velocity dispersion than the ground - based data .
the rotation velocity is observed to be @xmath0 at @xmath1 from the nucleus .
this is roughly twice the value measured from the ground at this distance .
the nuclear dispersion measured through the smallest fos aperture ( @xmath2 square ) is @xmath3 .
the average of four independent dispersion measurements at various positions inside the central @xmath1 is @xmath4 , with a rms scatter of @xmath5 .
the nuclear dispersion measured from the ground is only 8595@xmath6 , whereas the dispersion outside the central arcsec is only @xmath7@xmath8 .
these results significantly strengthen previous arguments for the presence of a massive nuclear black hole in m32 .
detailed dynamical models are presented in a series of companion papers .
# 1#2 .
And you have already written the first three sentences of the full article: astronomers have sought for two decades for dynamical evidence for the presence of massive black holes in galaxies by studying the dynamics of gas and stars in their nuclei .
rapid motions provide the main signature of a black hole .
if these are indeed observed , the main difficulty is to rule out alternative interpretations ..
Please generate the next two sentences of the article | gas motions can be due to hydrodynamical processes ( inflow , outflow , turbulence , etc . ) in addition to gravity .
large stellar velocities in galactic nuclei can be the result of an overabundance of stars on radial orbits . |
3,853 | Suppose that you have an abstract for a scientific paper: we illustrate a theoretical procedure determining necessary conditions for which simultaneous pure rolling kinetic constraints acting on a mechanical system can be fulfilled .
we also analyze the sufficiency of these conditions by generalizing to this case a well known and usually accepted assumption on the behavior of pure rolling constraint .
we present in detail the application of the procedure to some significative mechanical systems .
0.5truecm * pacs : * 45.40.-f , 45.50.-j * 2000 mathematical subject classification : * 70e18 70f25 70e60 * keywords : * rolling constraint linear and angular momenta equations .
And you have already written the first three sentences of the full article: mechanical systems subject to rolling kinetic constraints are one of the most studied argument of classical mechanics , especially for its wideness of applicability in several branches of mechanical sciences : contact mechanics , tribology , wear , robotics , ball bearing theory and control theory applied to moving engines and vehicles are only some of the important fields where the results about pure rolling constraint can be fruitfully used .
it is well known that , when a mechanical system moves in contact with an assigned rough surface , the effective fulfilment of the kinetic conditions determined by the rolling without sliding requirement of the system on the surface depends on the behavior , with respect to the considered law of friction , of the reaction forces acting on the system in the contact points .
for example , the roll of a disk on a rough straight line , considering the coulomb s law of friction , can happen only if the contact force lie inside the friction cone ( see example 1 below ) ..
Please generate the next two sentences of the article | however , even in the simplest case of a mechanical system formed by a single rigid body , in the case of multiple contact points between the rigid body and the rough surface , it could be an hard task to obtain sufficient information about the contact reactions in order to determine if the laws of friction are satisfied or not during the motion .
in fact the most common methods to determine information about the reactions , starting from the simple application of linear and angular momenta equations ( see e.g. @xcite ) to most refined techniques such as lagrangian multipliers in lagrangian mechanics ( see e.g. @xcite ) or deep analyses of the contact between the system and the surface ( see e.g. @xcite ) , have a global character . |
3,854 | Suppose that you have an abstract for a scientific paper: in the framework of soft - collinear effective theory with glauber gluons , results and predictions for inclusive hadron suppression , based upon in - medium parton shower evolution , are presented for au+au and pb+pb collisions at rhic and lhc energies @xmath0 agev and @xmath1 atev , respectively . the @xmath2 medium - induced splitting kernels are further implemented to evaluate the attenuation of reconstructed jet cross in such reactions and to examine their centrality and radius @xmath3 dependence . building upon a previously developed method to systematically resum the jet shape at next - to - leading logarithmic accuracy , a quantitative understanding of the jet shape modification measurement in pb+pb collisions at @xmath4 atev at the lhc can be achieved .
predictions for photon - tagged jet cross sections and shapes , that can shed light on the parton flavor dependence of in - medium parton shower modification , are also given .
% @xmath5 , inclusive hadron suppression , qcd evolution , reconstructed jet quenching , jet shapes , @xmath6-tagged jets .
And you have already written the first three sentences of the full article: effective field theory ( eft ) is a powerful framework based on exploiting symmetries and controlled expansions for problems with a natural separation of energy or distance scales .
efts are particularly important in qcd and nuclear physics .
an effective theory of qcd , ideally suited to jet applications , is soft - collinear effective theory ( scet ) @xcite ..
Please generate the next two sentences of the article | recently , first steps were taken to extend scet and describe jet evolution in strongly - interacting matter @xcite by introducing a transverse momentum exchange glauber gluon mode between the collinear partons and the medium quasi - particles .
the newly constructed theory , called soft - collinear effective theory with glauber gluons ( @xmath2 ) , was used to derive all @xmath7 @xmath8 medium - induced splitting kernels and discuss higher order @xmath9 corrections to the medium - modified jet substructure @xcite . |
3,855 | Suppose that you have an abstract for a scientific paper: a numerical method of determining the wire sag in a multiwire proportional chamber used in rich @xcite by solving the second order differential equation which governs the wire stability has been presented .
the three point finite difference method ( fdm ) has generated a tridiagonal matrix equation relating the deflection of wire segments to the force acting on it .
the precise estimates of electrostatic force has been obtained from accurate field computation using a nearly exact boundary element method ( nebem ) solver @xcite . .
And you have already written the first three sentences of the full article: the dimension of the multiwire chambers deployed in modern high energy physics experiments is usually large conforming to the scale of experimental setup .
the electrostatic instability in such chambers may be crucial when the amplitude of the oscillation caused by the action of electrostatic force alone or combined with the gravity becomes comparable to the electrode spacings .
the study of the wire deflection in such a geometry is usually a complex affair since an interplay between several physical forces determines the wire stability ..
Please generate the next two sentences of the article | the approximation of constant or linear dependence of the force on the wire deflection is not adequate to solve for the differential equation governing the wire dynamics because all the wires in the chamber move in a collective way influencing each other giving rise to a nonlinear effect .
since the exact solutions for the differential equation involving the nonlinear force are no longer known , it has to be solved numerically . of various methods of estimating the electrostatic sag from the differential equation , |
3,856 | Suppose that you have an abstract for a scientific paper: we introduce an alternative approach to the polarization theory of light .
this is based on a set of quantum operators , constructed from two independent bosons , being three of them the @xmath0 lie algebra generators , and the other one , the casimir operator of this algebra . by taking the expectation value of these generators in a two - mode coherent state
, their classical limit is obtained .
we use these classical quantities to define the new stokes - like parameters .
we show that the light polarization ellipse can be written in terms of the stokes - like parameters .
also , we write these parameters in terms of other two quantities , and show that they define a one - sheet ( poincar hyperboloid ) of a two - sheet hyperboloid . our study is restricted to the case of a monochromatic plane electromagnetic wave which propagates along the @xmath1 axis .
@xmath2 escuela superior de ingeniera mecnica y elctrica , unidad culhuacn , instituto politcnico nacional , av .
santa ana no .
1000 , col .
san francisco culhuacn , delegacin coyoacn , c.p .
04430 , mxico d. f. , mexico .
+ @xmath3 escuela superior de cmputo , instituto politcnico nacional , av . juan de dios batiz , esq .
av .
miguel othon de mendizbal , col .
lindavista , del .
gustavo a. madero , c.p .
07738 , mxico d. f. , mexico .
+ @xmath4 escuela superior de fsica y matemticas , instituto politcnico nacional , ed .
9 , unidad profesional adolfo lpez mateos , c.p .
07738 , mxico d. f. , mexico .
+ keywords : @xmath5 lie algebra , light polarization , poincar hyperboloid .
And you have already written the first three sentences of the full article: g. stokes studied the polarization properties of a quasi - monochromatic plane wave of light in an arbitrary polarization state by introducing four quantities , known since then as the stokes parameters @xcite .
the stokes parameters are a set of four quantities which provide intuitive and practical tools to describe the polarization of light @xcite .
the stokes parameters give a direct relation between the light ( photons ) polarization and the polarization of elementary particles @xcite ..
Please generate the next two sentences of the article | this fact was widely exploited to study many features of radiation of particles and to the scattering problems @xcite .
the stokes parameters are formulated in terms of the observables of the electromagnetic field , namely , the amplitudes and the relative phase difference between the orthogonal components of the field @xcite . |
3,857 | Suppose that you have an abstract for a scientific paper: systems of solitary - waves in the 1d gross - pitaevskii equation , which models a trapped atomic bose - einstein condensate , are investigated theoretically . to analyse the soliton - like nature of these solitary - waves , a particle analogy for the solitary - waves
is formulated .
exact soliton solutions exist in the absence of an external trapping potential , which behave in a particle - like manner , and we find the particle analogy we employ to be a good model also when a harmonic trapping potential is present . in the case of two solitons ,
the particle model is integrable , and the dynamics are completely regular .
the extension to three particles supports chaotic regimes .
the agreement between the particle model and the wave dynamics remains good even in chaotic regimes . in the case of a system of two solitary waves of equal norm ,
the solitons are shown to retain their phase difference for repeated collisions .
this implies that soliton - like regimes may be found in 3d geometries where solitary waves can be made to repeatedly collide out of phase , stabilising the condensate against collapse . .
And you have already written the first three sentences of the full article: solitary - waves may be found in solutions to nonlinear wave equations where the nonlinearity counteracts the dispersion of a wave - packet such that it retains its form as it propagates .
solitons are solitary - waves that emerge unscathed from collisions with each other , up to shifts in position and phase ; this behaviour is reminiscent of particle behaviour , motivating the particle - like name soliton .
this distinction is an important one , although in practice the names soliton and solitary - wave are commonly interchanged ..
Please generate the next two sentences of the article | `` classic '' solitons , in this sense , are to be found in integrable nonlinear wave - equations , such as the korteweg - de vries equation , the sine - gordon equation , and the one - dimensional nonlinear schrdinger equation .
the solitons ability to re - emerge after collisions is due to the fact that their dynamics are strongly constrained by conservation laws associated with the wave - equations integrability @xcite . |
3,858 | Suppose that you have an abstract for a scientific paper: we describe hst imaging of recent star formation complexes located in the extended uv disk ( xuv - disk ) component of ngc 5236 ( m 83 ) , ngc 5055 ( m 63 ) , and ngc 2090 .
photometry in four fuv
visible bands permits us to constrain the type of resolved stars and effective age of clusters , in addition to extinction .
the preliminary results given herein focus on cmd analysis and clustering properties in this unique star - forming environment . .
And you have already written the first three sentences of the full article: a decade ago , deep h@xmath0 observations indicated that some disk galaxies can support limited star formation at their extreme outer edge ( e.g. ferguson et al .
galex imaging then surprisingly revealed that m 83 ( thilker et al . 2005 ) and ngc 4625 ( gil de paz et al .
2005 ) have extended uv disks ( xuv - disks ) unapparent in the distribution of hii regions ..
Please generate the next two sentences of the article | we have since demonstrated that outer disk sf activity is commonplace , with @xmath1 1/3 of nearby s0-sm galaxies having discernible xuv - disk structure ( thilker et al .
2007 ) . for detailed information , see the review by gil de paz ( this volume ) or thilker et al . |
3,859 | Suppose that you have an abstract for a scientific paper: we present a simple and robust strategy for the selection of sampling points in uncertainty quantification .
the goal is to achieve the fastest possible convergence in the cumulative distribution function of a stochastic output of interest .
we assume that the output of interest is the outcome of a computationally expensive nonlinear mapping of an input random variable , whose probability density function is known .
we use a radial function basis to construct an accurate interpolant of the mapping .
this strategy enables adding new sampling points one at a time , _
adaptively_. this takes into full account the previous evaluations of the target nonlinear function .
we present comparisons with a stochastic collocation method based on the clenshaw - curtis quadrature rule , and with an adaptive method based on hierarchical surplus , showing that the new method often results in a large computational saving . .
And you have already written the first three sentences of the full article: we address one of the fundamental problems in uncertainty quantification ( uq ) : the mapping of the probability distribution of a random variable through a nonlinear function .
let us assume that we are concerned with a specific physical or engineering model which is computationally expensive .
the model is defined by the map @xmath0 ..
Please generate the next two sentences of the article | it takes a parameter @xmath1 as input , and produces an output @xmath2 , @xmath3 . in this paper
we restrict ourselves to a proof - of - principle one - dimensional case . |
3,860 | Suppose that you have an abstract for a scientific paper: we present a general scheme to realize a cold - atom quantum simulator of bi - dimensional atomic crystals .
our model is based on the use of two independently trapped atomic species : a first one , subject to a strong in - plane confinement , constitutes a 2d matter wave which interacts only with atoms of a second species , deeply trapped around the nodes of a 2d optical lattice . by introducing a general analytic approach
we show that the system green function can be exactly determined , allowing for the investigation of the matter - wave transport properties .
we propose some illustrative applications to both bravais ( square , triangular ) and non - bravais ( graphene , kagom ) lattices , studying both ideal periodic systems and experimental - size and disordered ones .
some remarkable spectral properties of these atomic artificial lattices are pointed out , such as the emergence of single and multiple gaps , flat bands and dirac cones .
all these features can be manipulated via the inter - species interaction , which results widely tunable due to the interplay between scattering length and confinements . .
And you have already written the first three sentences of the full article: in spite of the development of supercomputers and cutting - edge numerical methods , the simulation of experimental size many - body systems is still a hard task . following feynman s conjecture of a quantum simulator , it results useful to analyze manipulable systems able to reproduce , in a controllable way , the physical scenario that one wants to investigate .
the theoretical and experimental progresses of the last decades , boosted by nano - technological needs , made possible to combine the properties of cold gases and optical lattices to build - up artificial crystals able to mimic condensed - matter systems @xcite .
a crucial role in the success of these models is due to their experimental versatility ..
Please generate the next two sentences of the article | interactions between cold atoms can indeed be tuned via feshbach @xcite , dipolar @xcite or confinement - induced @xcite resonances . on the other hand
optical lattices offer a full control of the potential landscape felt by cold atoms , allowing for the exploration of quantum phase transitions @xcite . |
3,861 | Suppose that you have an abstract for a scientific paper: we show theoretically that nonrelativistic nearly - free electrons in solids should experience a trembling motion ( zitterbewegung , zb ) in absence of external fields , similarly to relativistic electrons in vacuum .
the zitterbewegung is directly related to the influence of periodic potential on the free electron motion .
the frequency of zb is @xmath0 , where @xmath1 is the energy gap .
the amplitude of zb is determined by the strength of periodic potential and the lattice period and it can be of the order of nanometers .
we show that the amplitude of zb does not depend much on the width of the wave packet representing an electron in real space .
an analogue of the foldy - wouthuysen transformation , known from relativistic quantum mechanics , is introduced in order to decouple electron states in various bands .
we demonstrate that , after the bands are decoupled , electrons should be treated as particles of a finite size .
in contrast to nearly - free electrons we consider a two - band model of tightly bound electrons .
we show that also in this case the electrons should experience the trembling motion .
it is concluded that the phenomenon of zitterbewegung of electrons in crystalline solids is a rule rather than an exception . .
And you have already written the first three sentences of the full article: zitterbewegung ( the trembling motion ) was theoretically devised by schroedinger @xcite after dirac had proposed his equation describing free relativistic electrons in vacuum .
schroedinger showed that , due to a non - commutativity of the quantum velocity @xmath2 with the dirac hamiltonian @xmath3 , relativistic electrons experience the zitterbewegung ( zb ) even in absence of external fields .
the frequency of zb is about @xmath4 and its amplitude is about the compton wavelength @xmath5 ..
Please generate the next two sentences of the article | it was later understood that the phenomenon of zb is due to an interference of electron states with positive electron energies ( @xmath6 ) and those with negative energies ( @xmath7 ) , see @xcite . in other words , the zb results from the structure of the dirac hamiltonian , which contains both positive and negative electron energies , and it is a purely quantum effect as it goes beyond newton s first law .
an important step in the understanding of zb was made by foldy and wouthuysen @xcite , ( see also @xcite ) , who showed that in absence of external fields there exists a unitary transformation that transforms the dirac hamiltonian into a hamiltonian in which positive and negative electron energies are decoupled . |
3,862 | Suppose that you have an abstract for a scientific paper: a global evolution picture of protoplanetary disks ( ppds ) is key to understanding almost every aspect of planet formation , where standard alpha - disk models have been constantly employed for its simplicity . in the mean time
, disk mass loss has been conventionally attributed to photoevaporation which controls disk dispersal .
however , a paradigm shift towards accretion driven by magnetized disk winds has been realized in the recent years , thanks to studies of non - ideal magneto - hydrodynamic effects in ppds .
i present a framework of global ppd evolution aiming to incorporate these advances , highlighting the role of wind - driven accretion and wind mass loss .
disk evolution is found to be largely dominated by wind - driven processes , and viscous spreading is suppressed .
the timescale of disk evolution is controlled primarily by the amount of external magnetic flux threading the disks , and how rapidly the disk loses the flux .
rapid disk dispersal can be achieved if the disk is able to hold most of its magnetic flux during the evolution .
in addition , because wind launching requires sufficient level of ionization at disk surface ( mainly via external far - uv radiation ) , wind kinematics is also affected by far - uv penetration depth and disk geometry . for typical disk lifetime of a few myrs ,
the disk loses approximately the same amount of mass through the wind as through accretion onto the protostar , and most of the wind mass loss proceeds from the outer disk via a slow wind .
fractional wind mass loss increases with increasing disk lifetime .
significant wind mass loss likely substantially enhances the dust to gas mass ratio , and promotes planet formation . .
And you have already written the first three sentences of the full article: global evolution of protoplanetary disks ( ppds ) is governed by the processes of angular momentum transport and outflow mass loss .
these processes directly control disk structure and evolution , which set the timescales of disk dispersal and hence planet formation ( e.g. , see @xcite and @xcite for reviews )
. they also strongly affect the evolution of dust grains , which are building blocks of planets , and feedback to disk thermal and chemical structures ( e.g. , see @xcite and @xcite for reviews ) ..
Please generate the next two sentences of the article | if planets are formed within the disk lifetime , planet - disk interaction leads to planet migration , which is also sensitive to global disk structure and evolution ( e.g. , see @xcite for a review ) . in brief
, a reliable global evolutionary picture of ppd is key to understanding most processes of planet formation . |
3,863 | Suppose that you have an abstract for a scientific paper: the general phenomena associated with sustained resonance are studied in this paper in connection with relativistic binary pulsars .
we represent such a system by two point masses in a keplerian binary system that evolves via gravitational radiation damping as well as an external tidal perturbation . for further simplification ,
we assume that the external tidal perturbation is caused by a normally incident circularly polarized monochromatic gravitational wave . in this case , the second - order partially averaged equations are studied and a theorem of c. robinson is employed to prove that for certain values of the physical parameters resonance capture followed by sustained resonance is possible in the averaged system .
we conjecture that sustained resonance can occur in the physical system when the perturbing influences nearly balance each other . .
And you have already written the first three sentences of the full article: imagine a stable hamiltonian system that is subjected to an external periodic perturbation as well as a frictional force that continuously takes energy out of the system .
if the driving force vanishes on the average , then in general the average behavior of the system is characterized by damped motion . under favorable conditions ,
however , the system could get captured into a prolonged resonance if the driving frequency is commensurate with an internal frequency of the system . in this paper , we study the dynamics of this phenomenon in the context of a simple model of certain relativistic binary systems that are of current interest ..
Please generate the next two sentences of the article | relativistic binary pulsars are generally expected to occur in some astrophysical environment and the gravitational effect of the surroundings on the binary orbit would be tidal in the first order of approximation . the evolution of the binary orbit under the combined influence of gravitational radiation reaction and the external tidal perturbation can lead to resonance under appropriate conditions [ 16 ] .
once we average over the external periodic tidal perturbation , the binary pulsar is expected to lose energy to gravitational radiation damping so that the relative orbit would spiral inward unless there is resonance capture . |
3,864 | Suppose that you have an abstract for a scientific paper: magnetization process and adiabatic demagnetization of the antiferromagnetic ising spin clusters with the shape of regular polyhedra ( platonic solids ) are exactly examined within the framework of a simple graph - theoretical approach .
while the ising cube as the only unfrustrated ( bipartite ) spin cluster shows just one trivial plateau at zero magnetization , the other regular ising polyhedra ( tetrahedron , octahedron , icosahedron and dodecahedron ) additionally display either one or two intermediate plateaux at fractional values of the saturation magnetization .
the nature of highly degenerate ground states emergent at intermediate plateaux owing to a geometric frustration is clarified .
it is evidenced that the regular ising polyhedra exhibit a giant magnetocaloric effect in a vicinity of magnetization jumps , whereas the ising octahedron and dodecahedron belong to the most prominent geometrically frustrated spin clusters that enable an efficient low - temperature refrigeration by the process of adiabatic demagnetization .
ising spin clusters , regular polyhedra , magnetization plateaux , giant magnetocaloric effect , exact results 05.50.+q , 75.10.hk , 75.10.jm , 75.30.sg , 75.40.cx , 75.60.ej .
And you have already written the first three sentences of the full article: a recent progress in a targeted design of molecular nanomagnets , which afford paradigmatic examples of assemblies of a finite number of interacting spin centers , has triggered a considerable interest to explore a magnetic behavior of small spin clusters magnetically isolated from the environment @xcite . despite their simplicity , small spin clusters may still exhibit favorable magnetic properties such as the quantum tunneling of magnetization and slow spin relaxation observable in single - molecule magnets , which have an immense application potential in a development of new resources suitable for quantum information processing and/or novel generation of high - density storage devices @xcite .
in addition , the molecular nanomagnets being composed of small spin clusters are ideal for an experimental testing of the limitations of physical theories especially when physical properties of relevant model systems can be calculated without any uncontrolled approximation .
magnetic properties of small spin clusters are predominantly determined by the nature of magnetic interactions between the spin centers in a cluster , whereas the heisenberg superexchange coupling is usually the most dominant interaction term that basically influences characteristic features of molecular nanomagnets @xcite ..
Please generate the next two sentences of the article | a lot of attention has been therefore paid to the study of antiferromagnetic heisenberg spin clusters , which may exhibit striking intermediate plateaux in low - temperature magnetization curves that often macroscopically manifest highly non - trivial quantum ground states @xcite .
an influence of the exchange , dipolar and single - ion anisotropy on the low - temperature magnetization process of the antiferromagnetic heisenberg spin clusters has attracted much less attention so far @xcite . |
3,865 | Suppose that you have an abstract for a scientific paper: we find static spherically symmetric monopoles in einstein - born - infeld - higgs model in @xmath0 dimensions .
the solutions exist only when a parameter @xmath1 ( related to the strength of gravitational interaction ) does not exceed certain critical value .
we also discuss magnetically charged non abelian black holes in this model .
we analyse these solutions numerically . 9.0 in 6.0 in .
And you have already written the first three sentences of the full article: some time ago monopoles in einstein - yang - mills - higgs(eymh ) model , for @xmath2 gauge group with higgs field in adjoint representation , were studied as a generalization of the t hooft - ployakov monopole to see the effect of gravity on it . in particular , it was found that solutions exist up to some critical value of a dimensionless parameter @xmath1 , characterising the strength of the gravitational interaction , above which there is no regular solution .
the existance of these solutions were also proved analytically for the case of infinite higgs mass .
also , non abelian magnetically charged black hole solutions were shown to exist in this model for both finite as well as infinite value of the coupling constant for higgs field ..
Please generate the next two sentences of the article | the abelian black holes exists for @xmath3 and non abelian black holes exist in a limited region of the @xmath4 plane .
recently born - infeld theory has received wide publicity , especially in the context of string theory . |
3,866 | Suppose that you have an abstract for a scientific paper: the split silicon - vacancy defect ( siv ) in diamond is an electrically and optically active color center .
recently , it has been shown that this color center is bright and can be detected at the single defect level .
in addition , the siv defect shows a non - zero electronic spin ground state that potentially makes this defect an alternative candidate for quantum optics and metrology applications beside the well - known nitrogen - vacancy color center in diamond .
however , the electronic structure of the defect , the nature of optical excitations and other related properties are not well - understood . here
we present advanced _
ab initio
_ study on siv defect in diamond .
we determine the formation energies , charge transition levels and the nature of excitations of the defect .
our study unravel the origin of the dark or shelving state for the negatively charged siv defect associated with the 1.68-ev photoluminescence center . .
And you have already written the first three sentences of the full article: the 1.68-ev photoluminescence ( pl ) center was reported many decades ago in diamond@xcite and where later it was assumed @xcite that silicon impurities were involved in this center .
this was confirmed by pl measurements at cryogenic temperature on si - doped chemical vapor deposition ( cvd ) polycrystalline diamond samples where the fine structure of the 1.68-ev pl center could be detected.@xcite a 12-line fine structure is observed close to 1.68 ev , and this can be divided into three similar groups each containing four components .
the relative strengths of the optical absorption for the three groups of lines are found to be the same as the ratio of the abundancies of the natural isotopes of silicon , @xmath0si , @xmath1si , and @xmath2si@xcite ..
Please generate the next two sentences of the article | the 4-line fine structure for an individual si - isotope is assigned to doublet levels both in the ground and excited states which split by about 48 and 242 ghz , respectively.@xcite it has been assumed that this small splitting might be explained by dynamic jahn - teller effect@xcite and/or by spin - orbit effect.@xcite recently , single photon - emission from 1.68-ev pl center has been demonstrated @xcite .
its zero - phonon - line ( zpl ) with 5 nm width even at room temperature and the near infrared emission makes this pl center very attractive candidate for quantum optics@xcite and biomarker@xcite applications . |
3,867 | Suppose that you have an abstract for a scientific paper: the threshold between classical and nonclassical two - qubit states is drawn at the place when these states can no longer be described by classical correlations , i.e. , quantum discord or entanglement appear .
however , to check if the correlations are classical ( in terms of quantum discord and entanglement ) it is sufficient to witness the lack of quantum discord because its zero value implies the lack of entanglement .
we explain how the indicator of quantum discord introduced by girolami and adesso [ phys .
rev .
lett . * 108 * , 150403 ( 2012 ) ] can be practically measured in linear - optical systems using standard beam splitters and photon detectors .
we study the efficiency of the setup assuming both ideal and real components and show that the efficiency of the proposed implementation is better than the full two - photon quantum tomography .
thus , we demonstrate that a class of experiments previously available on nmr platform can be implemented in optical systems . .
And you have already written the first three sentences of the full article: the threshold between the classical and quantum world has fascinated physicists since the discovery of quantum phenomena and realizing how different they are from our everyday experience .
one of the prominent examples of quantum behavior is the nonlocality leading to violation of bell s inequalities @xcite . for two - level systems
there is no nonlocality without quantum entanglement , but the opposite can be true @xcite ..
Please generate the next two sentences of the article | quantum entanglement plays an important role in quantum information processing @xcite .
however , the entanglement is not the only type of non - classical correlations . as described by ollivier and zurek @xcite |
3,868 | Suppose that you have an abstract for a scientific paper: we consider two independent quantum walks on separate lines augmented by partial or full swapping of coins after each step . for classical random walks , swapping or not swapping coins makes little difference to the random walk characteristics , but we show that quantum walks with partial swapping of coins have complicated yet elegant inter - walker correlations .
specifically we study the joint position distribution of the reduced two - walker state after tracing out the coins and analyze total , classical and quantum correlations in terms of mutual information , quantum mutual information , and measurement - induced disturbance .
our analysis shows intriguing quantum features without classical analogues . .
And you have already written the first three sentences of the full article: quantum walks ( qws ) @xcite are especially interesting because of their importance in quantum algorithms research @xcite and also because they represent an intriguing quantum version of the ubiquitous classical phenomenon of random walks ( rws ) .
originally conceived as a single walker whose left or right step on a line is entangled with the outcome of flipping a single two - sided quantum coin , the qw has been extended to more general cases of higher - dimensional walks @xcite , multiple walkers and/or multiple coins @xcite .
these generalizations enable exploration of qws in complex settings , which could connect with real - world phenomena such as transport in photosynthetic protein complexes @xcite ..
Please generate the next two sentences of the article | additionally the inclusion of more walkers and/or coins can efficiently enlarge the hilbert space being explored because a linear increase in degrees of freedom exponentially enlarges the hilbert space . here
we explore the complex case of two walkers each carrying and ( quantumly ) flipping separate coins but with the freedom to swap partially the coins between flips . |
3,869 | Suppose that you have an abstract for a scientific paper: we present ubvi photometry for the old open cluster collinder 261 . from comparison of the observed colour - magnitude diagrams with simulations based on stellar evolutionary models we derive in a self consistent way reddening , distance , and age of the cluster : = [email protected] , ( m - m)@xmath1=11.7 - 12.0 , and age=7@xmath08 gyr or 9@xmath011 gyr , depending on the adopted stellar tracks .
the models in better agreement with the data turn out to have metallicity at most solar .
= -1 cm hertzsprung - russel ( hr ) diagram open clusters and associations : individual : collinder 261 age metallicity .
And you have already written the first three sentences of the full article: galactic open clusters are excellent tools to study the evolution of our galaxy from the chemical and structural points of view .
they provide information on the chemical abundances in the disk and relative radial gradients ( e.g. janes 1979 , panagia and tosi 1981 , friel and janes 1993 ) , on the interactions between thin and thick disks ( e.g. sandage 1988 ) , on the average radial velocities and stellar ages at different galactic locations ( e.g. janes and phelps 1994 ) , on the absolute age of the disk .
this latter could also be obtained from isolated field stars , e.g. studying the white dwarfs luminosity function at its cool end ; the actual value is still uncertain , varying from about 6.5 to 13 gyr due to different models for the white dwarfs cores and to different treatments of the cooling and crystallization processes ( see for example winget et al ..
Please generate the next two sentences of the article | 1987 , isern et al .
1995 , wood 1995 ) , but the oldest ages ( more than about 9 gyr ) seem to be preferred . |
3,870 | Suppose that you have an abstract for a scientific paper: in recent work @xcite , boltzmann and fokker - planck equations were derived for the `` yard - sale model '' of asset exchange . for the version of the model without redistribution ,
it was conjectured , based on numerical evidence , that the time - asymptotic state of the model was oligarchy
complete concentration of wealth by a single individual . in this work
, we prove that conjecture by demonstrating that the gini coefficient , a measure of inequality commonly used by economists , is an @xmath0 function of both the boltzmann and fokker - planck equations for the model . .
And you have already written the first three sentences of the full article: over one hundred years ago , the italian economist vilfredo pareto @xcite made one of the first empirical studies of the distribution of wealth by undertaking a careful study of land ownership in italy , switzerland and germany .
in the course of this study , he plotted the fraction of economic agents with land holdings worth more than @xmath1 as a function of @xmath1 .
his studies led him to believe that this function , which we shall denote by @xmath2 has a universal form . by its definition , it is clear that @xmath3 is monotone non - increasing , and that @xmath4 and @xmath5 ..
Please generate the next two sentences of the article | what pareto observed is that @xmath2 is approximately equal to one for all @xmath1 less than a certain cutoff value denoted by @xmath6 , and decays as a power law for @xmath7 .
that is , pareto s empirical observations led him to conclude that it is approximately true that @xmath8 the power @xmath9 is usually called the pareto exponent . to put pareto s observations in modern terms , we may note that @xmath10 is the cumulative distribution function ( cdf ) of economic agents , ordered by wealth . |
3,871 | Suppose that you have an abstract for a scientific paper: we investigate the collisional stability of magnetically trapped ultracold molecules , taking into account the influence of magnetic fields .
we compute elastic and spin - state - changing inelastic rate constants for collisions of the prototype molecule @xmath0o@xmath1 with a @xmath2he buffer gas as a function of the magnetic field and the translational collision energy .
we find that spin - state - changing collisions are suppressed by wigner s threshold laws as long as the asymptotic zeeman splitting between incident and final states does not exceed the height of the centrifugal barrier in the exit channel .
in addition , we propose a useful one - parameter fitting formula that describes the threshold behavior of the inelastic rates as a function of the field and collision energy .
results show a semi - quantitative agreement of this formula with the full quantum calculations , and suggest useful applications also to different systems . as an example , we predict the low - energy rate constants relevant to evaporative cooling of molecular oxygen . # 1@xmath3#1 .
And you have already written the first three sentences of the full article: the probable success of experiments aimed at producing magnetically trapped ultracold molecular samples depends heavily on the effects of collisional processes .
for example , paramagnetic alkali dimers can be produced via photassociation of ultracold atoms @xcite , but the resulting molecules , typically in high - lying vibrational states , are subject to vibrational quenching collisions @xcite which can release a large amount of energy and dramatically affect the efficiency of the cooling .
alternatively , cold molecules in their vibrational ground states can be produced either by thermal contact with a cold helium buffer gas @xcite or by stark slowing , for species that possess an electric dipole moment @xcite ..
Please generate the next two sentences of the article | collisions are of obvious importance to buffer - gas cooling ( bgc ) , as well as to forced evaporative cooling ( ec ) that will be required to lower the temperature of these gases further and achieve for instance bose - einstein condensation ( bec ) .
both processes require large elastic collision rates to thermalize the gas . |
3,872 | Suppose that you have an abstract for a scientific paper: we present calculations of the upper critical field @xmath0 in superconducting films as a function of increasing disorder ( as measured by the normal state resistance per square @xmath1 ) . in contradiction to previous work , we find that there is no anomalous low temperature positive curvature in @xmath2 vs @xmath3 as disorder is increased .
we show that the previous prediction of this effect is due to an unjustified analytical approximation of sums occuring in the perturbative calculation .
our treatment includes both a careful analysis of first - order perturbation theory , and a non - perturbative resummation technique .
no anomalous curvature is found in either case .
we present our results in graphical form .
psfig # 1#2 .
And you have already written the first three sentences of the full article: increasing disorder is known to suppress superconductivity in low - dimensional systems such as thin films and narrow wires@xcite .
this occurs because the disorder causes electrons to move diffusively rather than ballistically , making them less efficient at screening the coulomb repulsion between electrons .
the increased coulomb repulsion decreases both the electron - electron attraction needed for superconductivity , and the density of states of electrons available for pairing at the fermi surface@xcite ..
Please generate the next two sentences of the article | typical types of experimental data are : ( i ) @xmath4 , the transition temperature as a function of normal state resistance per square@xcite ; ( ii ) @xmath5 , the order parameter at zero temperature , as a function of normal state resistance per square@xcite ; ( iii ) @xmath6 , the upper critical field as a function of temperature and normal state resistance per square@xcite ; ( iv ) @xmath7 , transition temperature as a function of resistance per square and spin - flip scattering rate in films with magnetic impurities.@xcite it is found experimentally that @xmath4 curves from a wide variety of materials fit a universal curve with a single fitting parameter , whilst the few experimental measurements of @xmath8 , seem to have @xmath9 roughly constant@xcite .
this fitting to a single curve , whilst pleasing in showing that the basic ingredients of our theories are correct , does not allow detailed analysis of the theory . |
3,873 | Suppose that you have an abstract for a scientific paper: the question we address in this paper is the determination of the correlation properties of the dark matter halos appearing in cosmic density fields once they underwent a strongly nonlinear evolution induced by gravitational dynamics .
a series of previous works have given indications of what non - gaussian features are induced by nonlinear evolution in term of the high - order correlation functions . assuming such patterns for the matter field , that is that the high - order correlation functions behave as products of two - body correlation functions , we derive the correlation properties of the halos , that are assumed to represent the correlation properties of galaxies or clusters .
the hierarchical pattern originally induced by gravity is shown to be conserved for the halos .
the strength of their correlations at any order varies , however , but is found to depend only on their internal properties , namely on the parameter @xmath0 where @xmath1 is the mass of the halo , @xmath2 its size and @xmath3 is the power law index of the two - body correlation function .
this internal parameter is seen to be close to the depth of the internal potential well of virialized objects .
we were able to derive the explicit form of the generating function of the moments of the halo counts probability distribution function .
in particular we show explicitely that , generically , @xmath4 in the rare halo limit .
various illustrations of our general results are presented . as a function of the properties of the underlying matter field
, we construct the count probabilities for halos and in particular discuss the halo void probability .
we evaluate the dependence of the halo mass function on the environment : within clusters , hierarchical clustering implies the higher masses are favored .
these properties solely arise from what is a natural bias ( , naturally induced by gravity ) between the observed objects and the unseen matter field , and how it manifests itself depending on which selection....
And you have already written the first three sentences of the full article: one of the major pending cosmological problem for the formation of galaxies and clusters , their distribution and evolution , is the relation of the latter with the initial conditions prevailing in the early universe . to this sake ,
most of the observational constraints are relative to the luminous part of the universe . on the other hand , theoretical model of primordial fluctuations
are for the matter distribution . whether light traces matter , so that the former can be used to constrain the latter , has been a long debate over the past decade ..
Please generate the next two sentences of the article | it was clear that from the constraint on the small - scale peculiar velocity dispersion of galaxies ( davis & peebles 1983 ) , matter can not trace light ( kaiser 1984 , davis et al .
1985 , schaeffer & silk 1985 ) if the density of the universe is to be equal to the critical density . that galaxies might be biased with respect to the matter field |
3,874 | Suppose that you have an abstract for a scientific paper: quantum telescope is a recent idea aimed at beating the diffraction limit of spaceborne telescopes and possibly also other distant target imaging systems .
there is no agreement yet on the best setup of such devices , but some configurations have been already proposed .
+ in this letter we characterize the predicted performance of quantum telescopes and their possible limitations .
our extensive simulations confirm that the presented model of such instruments is feasible and the device can provide considerable gains in the angular resolution of imaging in the uv , optical and infrared bands . we argue that it is generally possible to construct and manufacture such instruments using the latest or soon to be available technology .
we refer to the latest literature to discuss the feasibility of the proposed qt system design .
copyright : the optical society ( osa publishing ) 2016 . published in optics letters vol .
41 no . 6 ( 2016 ) + .
And you have already written the first three sentences of the full article: astronomical images obtained form the ground suffer from serious degradation of resolution , because the light passes through a turbulent medium ( the atmosphere ) @xcite before reaching the detector .
a number of methods was developed to alleviate this phenomenon @xcite and multiple special - case solutions were implemented as well ( e.g. @xcite ) , but none of them is able to provide a perfect correction and restore the diffraction - limited ( dl ) image .
therefore , the best observatories , in terms of angular resolution , are the spaceborne ones , since they are limited only by the dl ..
Please generate the next two sentences of the article | recently , there is an increasing interest in the attempts to overcome the dl boundary .
devices which can give such possibility are called the quantum telescopes ( qt ) . |
3,875 | Suppose that you have an abstract for a scientific paper: a stochastic cellular automaton exhibiting parity conserving class transition has been investigated in the presence of quenched spatial disorder by large scale simulations .
numerical evidence has been found that weak disorder causes irrelevant perturbation for the universal behavior of the transition and the absorbing phase of this model .
this opens up the possibility for experimental observation of the critical behavior of a nonequilibrium phase transition to absorbing state .
for very strong disorder the model breaks up to blocks with exponential size distribution and continuously changing critical exponents are observed . for strong disorder
the randomly distributed diffusion walls introduce another transition within the inactive phase of the model , in which residual particles survive the extinction .
the critical dynamical behavior of this transition has been explored . .
And you have already written the first three sentences of the full article: the classification of the universality classes of nonequilibrium phase transitions to absorbing states is still an open problem of statistical physics @xcite .
reaction - diffusion ( rd ) models exhibiting phase transitions to absorbing states bear with a particular interest since many other types of systems like surface growth , spin systems or stochastic cellular automata can be mapped on them . unfortunately there hasnt been experimental verification of such classes except the coagulating random walk : @xmath0 ( crw ) in one dimension @xcite .
this is mainly due to the fact that the most well known , robust directed percolation ( dp ) class @xcite is sensitive to disorder @xcite , which occurs in real systems naturally ..
Please generate the next two sentences of the article | it would be very important to find some other nonequilibrium class , which proves to be less sensitive to disorder , hence would provide a candidate for experimental verification .
the study of disordered systems is a hot topic of current research of statistical physics @xcite . |
3,876 | Suppose that you have an abstract for a scientific paper: we develop a multi - scale theory for group of diffeomorphisms based on previous works @xcite .
the purpose of the paper is to develop in details a variational approach for multi - scale on diffeomorphisms and to generalize to several scales the semi - direct product of group representation .
we also show that the approaches presented in @xcite and the mixture of kernels of [ rvw+11 ] are equivalent . .
And you have already written the first three sentences of the full article: in this paper , we develop a multi - scale theory for groups of diffeomorphisms in the context of image registration .
the setting of _ large deformation diffeomorphic matching _ has been introduced in seminal papers @xcite and this approach has been applied in the field of computational anatomy @xcite .
the initial problem deals with the diffeomorphic registration of two given biomedical images or shapes ..
Please generate the next two sentences of the article | an important aspect of this model is the use of reproducing kernel hilbert spaces ( rkhs ) of vector valued functions to define the lie algebra of the group of diffeomorphisms .
although our context is very different from kernel based methods for machine learning @xcite , some analogies may be worth noticing . |
3,877 | Suppose that you have an abstract for a scientific paper: projective geometry provides the preferred framework for most implementations of euclidean space in graphics applications .
translations and rotations are both linear transformations in projective geometry , which helps when it comes to programming complicated geometrical operations .
but there is a fundamental weakness in this approach the euclidean distance between points is not handled in a straightforward manner . here
we discuss a solution to this problem , based on conformal geometry .
the language of geometric algebra is best suited to exploiting this geometry , as it handles the interior and exterior products in a single , unified framework .
a number of applications are discussed , including a compact formula for reflecting a line off a general spherical surface . * conformal geometry , euclidean space + and geometric algebra * chris doran , anthony lasenby and joan lasenby cambridge university , uk keywords : geometric algebra , clifford algebra , conformal geometry , projective geometry , homogeneous coordinates , sphere geometry , stereographic projection .
And you have already written the first three sentences of the full article: in computer graphics programming the standard framework for modeling points in space is via a projective representation .
so , for handling problems in three - dimensional geometry , points in euclidean space @xmath0 are represented projectively as rays or vectors in a four - dimensional space , @xmath1 the additional vector @xmath2 is orthogonal to @xmath0 , @xmath3 , and is normalised to 1 , @xmath4 . from the definition of @xmath5 it is apparent that @xmath2 is the projective representation of the origin in euclidean space .
the projective representation is _ homogeneous _.
Please generate the next two sentences of the article | , so both @xmath5 and @xmath6 represent the same point .
projective space is also not a linear space , as the zero vector is excluded . given a vector @xmath7 in projective space , the euclidean point @xmath8 is then recovered from @xmath9 the components of @xmath7 define a set of homogeneous coordinates for the position @xmath8 . |
3,878 | Suppose that you have an abstract for a scientific paper: consider the voter model on a box of side length @xmath0 ( in the triangular lattice ) with boundary votes fixed forever as type 0 or type 1 on two different halves of the boundary .
motivated by analogous questions in percolation , we study several geometric objects at stationarity , as @xmath1 .
one is the interface between the ( large i.e. , boundary connected ) 0-cluster and 1-cluster .
another is the set of large `` coalescing classes '' determined by the coalescing walk process dual to the voter model . .
And you have already written the first three sentences of the full article: in this section we motivate our study of the ( two - dimensional ) voter model and its dual coalescing walks through their connection with a number of percolation models . in section 2
, we report on numerical results for the dimension of a natural `` chordal interface '' of the voter model . in section 3
we give rigorous ( and a few numerical ) results on the large coalescing classes for coalescing walks ( where vertices @xmath2 and @xmath3 in a box are in the same class if their walks coalesce before hitting the boundary ) . in the appendix ,.
Please generate the next two sentences of the article | more details about our numerical results are provided . among the most important breakthroughs in statistical physics and probability in the last two decades
is the work by schramm and coauthors @xcite and smirnov @xcite identifying ( or conjecturing ) members of the schramm - loewner evolution family of random curves as the scaling limits of various random walks and interfaces in two - dimensional spin systems . |
3,879 | Suppose that you have an abstract for a scientific paper: delay is an important and ubiquitous aspect of many biochemical processes . for example
, delay plays a central role in the dynamics of genetic regulatory networks as it stems from the sequential assembly of first mrna and then protein .
genetic regulatory networks are therefore frequently modeled as stochastic birth - death processes with delay . here
we examine the relationship between delay birth - death processes and their appropriate approximating delay chemical langevin equations .
we prove that the distance between these two descriptions , as measured by expectations of functionals of the processes , converges to zero with increasing system size .
further , we prove that the delay birth - death process converges to the thermodynamic limit as system size tends to infinity .
our results hold for both fixed delay and distributed delay .
simulations demonstrate that the delay chemical langevin approximation is accurate even at moderate system sizes .
it captures dynamical features such as the spatial and temporal distributions of transition pathways in metastable systems , oscillatory behavior in negative feedback circuits , and cross - correlations between nodes in a network .
overall , these results provide a foundation for using delay stochastic differential equations to approximate the dynamics of birth - death processes with delay . .
And you have already written the first three sentences of the full article: gene regulatory networks play a central role in cellular function by translating genotype into phenotype . by dynamically controlling gene expression ,
gene regulatory networks provide cells with a mechanism for responding to environmental challenges .
therefore , creating accurate mathematical models of gene regulation is a central goal of mathematical biology ..
Please generate the next two sentences of the article | delay in protein production can significantly affect the dynamics of gene regulatory networks .
for example , delay can induce oscillations in systems with negative feedback @xcite , and has been implicated in the production of robust , tunable oscillations in synthetic gene circuits containing linked positive and negative feedback @xcite . |
3,880 | Suppose that you have an abstract for a scientific paper: the symmetry energy at sub- and supra - saturation densities has great importance for understanding the exact nature of asymmetric nuclear matter as well as neutron stars , but it is poorly known , especially at supra - saturation densities .
we will demonstrate here whether or not the neutron - to - proton ratios from different kinds of fragments can determine the supra - saturation behavior of the symmetry energy .
for this purpose , a series of sn isotopes were simulated at different incident energies using the isospin quantum molecular dynamics ( iqmd ) model with either a soft or a stiff symmetry energy .
it is found that the single neutron - to - proton ratio from free nucleons as well as light charged particles ( lcps ) is sensitive to the symmetry energy , incident energy , and isospin asymmetry of the system .
however , with the double neutron - to - proton ratio , this is true only for the free nucleons .
it is possible to study the high - density behavior of symmetry energy by using the neutron - to - proton ratio from free nucleons . .
And you have already written the first three sentences of the full article: from the bethe - weizsacker mass formula , it is well understood that the symmetry energy from bulk matter is the difference between the energy of pure neutron matter and pure symmetric matter .
mathematically , it can we written as @xmath0 where @xmath1 and @xmath2 .
@xmath3 , @xmath4 , and @xmath5 are the neutron , proton , and nuclear matter densities , respectively ..
Please generate the next two sentences of the article | the symmetry energy has great importance in the dense matter existing in the neutron stars , but only indirect information can be extracted from astrophysical observations @xcite .
it is also important in the quark gluon plasma ( qgp ) and hadron gas ( hg ) phase @xcite . |
3,881 | Suppose that you have an abstract for a scientific paper: in recent years , wide - field sky surveys providing deep multi - band imaging have presented a new path for indirectly characterizing the progenitor populations of core - collapse supernovae ( sn ) : systematic light curve studies .
we assemble a set of 76 @xmath0-band type iip sn light curves from , obtained over a constant survey program of 4 years and classified using both spectroscopy and machine learning - based photometric techniques .
we develop and apply a new bayesian model for the full multi - band evolution of each light curve in the sample .
we find no evidence of a sub - population of fast - declining explosions ( historically referred to as `` type iil '' sne ) .
however , we identify a highly significant relation between the plateau phase decay rate and peak luminosity among our sne iip .
these results argue in favor of a single parameter , likely determined by initial stellar mass , predominantly controlling the explosions of red supergiants . this relation could also be applied for supernova cosmology , offering a standardizable candle good to an intrinsic scatter of @xmath1 mag .
we compare each light curve to physical models from hydrodynamic simulations to estimate progenitor initial masses and other properties of the type iip sn sample .
we show that correction of systematic discrepancies between modeled and observed sn iip light curve properties and an expanded grid of progenitor properties , are needed to enable robust progenitor inferences from multi - band light curve samples of this kind .
this work will serve as a pathfinder for photometric studies of core - collapse sne to be conducted through future wide field transient searches . .
And you have already written the first three sentences of the full article: core - collapse supernovae ( sne ) mark the explosive deaths of massive stars .
several independent lines of evidence including explosion modeling @xcite , progenitor star photometry @xcite , rate statistics @xcite , and theory @xcite combine to suggest a lower main sequence initial mass ( @xmath2 ) limit for achieving core collapse of @xmath3 .
red supergiant progenitor stars in this mass range are known to produce type iip ( hydrogen rich ) sn explosions , the most common form of core - collapse sn ..
Please generate the next two sentences of the article | the upper mass limit for sne iip progenitors is more uncertain , with stars of @xmath4 realizing significant mass loss depending on their mass , metallicity , rotation rate , binarity , and other properties ; and even more massive stars ending their lives through more exotic explosion mechanisms .
these mass limits for cc - sn progenitor stars have profound implications throughout stellar and galactic astrophysics and cosmology , including as an input to and constraint on models of stellar evolution for massive stars @xcite , chemical evolution @xcite , supernova feedback in the interstellar medium and galaxy formation @xcite , and astrobiological planetary sterilization rates @xcite . |
3,882 | Suppose that you have an abstract for a scientific paper: we discuss the quasiclassical green function method for a two - dimensional electron gas in the presence of spin - orbit coupling , with emphasis on the meaning of the @xmath0-integration procedure . as an application of our approach ,
we demonstrate how the spin - hall conductivity , in the presence of spin - flip scattering , can be easily obtained from the spin - density continuity equation .
ep2ds-17 , manuscript , latex-2e , style files 72.25.ba , 72.25.dc .
And you have already written the first three sentences of the full article: the quasiclassical technique is one of the most powerful methods to tackle transport problems .
its main virtue relies in the fact that starting from a microscopic quantum formulation of the problem at hand it aims at deriving a simpler kinetic equation resembling the semiclassical boltzmann one . in deriving such an equation
some of the information at microscopic level is suitably incorporated in a set of parameters characterizing the physical system at macroscopic level ..
Please generate the next two sentences of the article | since the first application to superconductivity , this equation is known as the eilenberger equation ( for a review see for instance @xcite ) .
we have recently derived@xcite such an equation for a two - dimensional electron gas in the presence of spin orbit coupling with hamiltonian @xmath1 where @xmath2 is a momentum dependent internal magnetic field . in the case of rashba spin - orbit coupling @xmath3 . in ref . |
3,883 | Suppose that you have an abstract for a scientific paper: there are now strong hints suggesting that neutrinos do have a mass after all .
if they do have a mass , it would have to be tiny .
why is it so ?
is it dirac or majorana ?
can one build a model in which a teeny , tiny dirac neutrino mass arises in a natural way ?
can one learn something else other than just neutrino masses ?
what are the extra phenomenological consequences of such a model ? these are the questions that i will try to focus on in this talk . .
And you have already written the first three sentences of the full article: a subtitle to this talk should perhaps go like `` a see - saw - like mechanism without a majorana mass '' . here , i shall try to present arguments as to why it is interesting and worthwhile to study scenarios in which neutrinos possess a mass which is _ pure dirac _ in nature . along the way , i shall try to argue that one should perhaps try to separate the issue of a see - saw like mechanism from that of a majorana mass . by see - saw - like mechanism
, it is meant that a `` tiny '' mass arises due to the presence of a very large scale .
the suggestions that neutrinos do indeed possess a mass came from three different sources , all of which involve oscillations of one type of neutrino into another type ..
Please generate the next two sentences of the article | they are the superkamiokande atmospheric neutrino oscillation , the solar neutrino results , and the lsnd result @xcite . the present status of these three oscillation experiments is well presented in this workshop .
the future confirmation of all three will certainly have a profound impact on the understanding of the origin of neutrino masses . |
3,884 | Suppose that you have an abstract for a scientific paper: in this paper we report the long - term optical observation of the faint soft x - ray transient sax j1810.8 - 2609 from ogle and moa .
we have focused on the 2007 outburst , and also did the cross - correlate between its optical light curves and the quasi - simultaneous x - ray observations from _ rxte / swift_. both the optical and x - ray light curves of 2007 outburst show multi - peak features .
quasi - simultaneous optical / x - ray luminosity shows that both the x - ray reprocessing and viscously thermal emission can explain the observed optical flux .
there is a slightly x - ray delay of @xmath0 days during the first peak , while the x - ray emission lags the optical emission by @xmath1 days during the rebrightening stage , which suggests that x - ray reprocessing emission contributes significantly to the optical flux in the first peak , but the viscously - heated - disk origin dominates the optical flux during rebrightening .
it implies variation of the physical environment of the outer disk , even the source stayed in low - hard state during the whole outburst .
the @xmath1-day x - ray lag indicates a small accretion disk of the system , and the optical counterpart was not detected by ogle and moa during quiescence , which constrained it to be fainter than m@xmath2 = 7.5 mag . there is a suspected short - time optical flare detected at mjd = 52583.5 without x - ray counterpart detected
, this single flux increase may imply a magnetic loop reconnection in the outer disk as proposed by zurita et al ( 2003 ) .
the observations cover all stages of the outburst , however , due to the low sensitivity of _
rxte_/asm , we can not conclude whether it is an optical precursor at the initial rise of the outburst . .
And you have already written the first three sentences of the full article: neutron star low mass x - ray binaries ( lmxb ) were believed to behavior similarly to the black hole lmxbs ( lin et al . 2007 ) .
they spend most of the time in quiescence , and occasionally show an outburst with accretion rate dramatically increased . during the outburst
, the neutron star lmxbs will evolve at the similar track of the state transition as black hole lmxbs do , basically from a low / hard state to a high / soft state ( remillard & mcclintock 2006 ) ..
Please generate the next two sentences of the article | the optical emission of lmxbs was often contributed to thermal emission of the companion star and outer accretion disk , and sometimes synchrotron emission of a jet .
the disk can be heated by mainly two physical processes , one is the friction between adjacent layers of the disk when the materials were accreted ( shakura & sunyaev 1973 ) , the other is the x - ray irradiation from the inner disk ( van paradijs & mcclintock 1994 ) . with the evolution of disk structure and other physical properties , the radiation mechanism of the optical flux will vary , which will be different for neutron star lmxbs and black hole lmxbs . for black hole lmxbs , |
3,885 | Suppose that you have an abstract for a scientific paper: we discuss the tracing of star formation histories with esa s space astrometry mission gaia , emphasizing the advantages of agb stars for this purpose .
gaia s microarcsecond - level astrometry , multi - band photometry and spectroscopy will provide individual distances , motions , @xmath0 , @xmath1 and @xmath2 $ ] for vast numbers of agb stars in the galaxy and beyond .
reliable ages of agb stars can be determined to distances of @xmath3200 kpc in a wide range of ages and metallicities , allowing star formation histories to be studied in a diversity of astrophysical environments . -20pt
-20pt -20pt -10pt .
And you have already written the first three sentences of the full article: the european space agency s gaia mission , approved for launch in 201012 , aims at surveying the galaxy to 20th visual magnitude , using a combination of astrometric measurements ( for trigonometric parallaxes and proper motions ) , multiband photometry ( for basic stellar parameters like temperature and metallicity ) , and radial - velocity measurements .
targeted accuracies versus magnitude allow direct distances and motions to be obtained for large samples of intrinsically bright stars across the galaxy and in some nearby local group galaxies .
expected typical accuracies are shown in table 1 . in total more than 1 billion stars will be observed , of which 50100 million will obtain individual parallax distances to better than 5 per cent ..
Please generate the next two sentences of the article | a primary science goal is to study formation , evolution and structure of the galaxy , for which large - scale mappings of star formation histories are essential . for a full description of the very broad range of science goals
see perryman et al . |
3,886 | Suppose that you have an abstract for a scientific paper: we present bepposax observations of the two fr i type radio galaxies hercules a ( 3c 348 ) and mrc 0625 - 536 in the energy range @xmath0 kev .
data analysis shows that the x - ray flux from hercules a is consistent with a diffuse thermal plasma emitting at @xmath1 kev with a possible , but somewhat uncertain , contribution of a softer component at @xmath2 kev
. the non thermal emission from the active nucleus must be significantly smaller than the thermal one , and no indication of relevant core obscuration by a surrounding torus was detected .
the flux from mrc 0625 - 536 originates form an extended region and has been fitted to a thermal law with @xmath3 kev and with a column density consistent with the galactic absorption .
a spatially resolved spectral analysis does not show a relevant variation of the temperature and the metallicity across the diffuse emission zone .
a non thermal spectral component , related to the nuclear activity , may be present in the innermost region with some possible amount of local obscuration , contributing @xmath4 to the total luminosity .
hard x - ray emission from mrc 0625 - 536 has been detected in the pds ( 15 - 200 kev ) that may be related either to its galactic core or to the intracluster region .
1.5 cm .
And you have already written the first three sentences of the full article: the two sources hercules a ( 3c 348 ) and mrc 0625 - 536 are radio galaxies classified as
fanaroff - riley i ( fr i ) type objects , although hercules a has indeed the morphology of a fr i radio galaxy , but with a much higher radio luminosity , typical of a fr ii object .
the galaxy associated with mrc 0625 - 536 is the main member of the cluster a 3391 , while hercules a lies in a group ..
Please generate the next two sentences of the article | recent spectral and morphological analyses of x - ray data , collected by rosat and asca ( otani et al .
1998 , siebert et al . 1999 , |
3,887 | Suppose that you have an abstract for a scientific paper: the position - dependent exact - exchange energy per particle @xmath0 ( defined as the interaction between a given electron at @xmath1 and its exact - exchange hole ) at metal surfaces is investigated , by using either jellium slabs or the semi - infinite ( si ) jellium model . for jellium slabs ,
we prove analytically and numerically that in the vacuum region far away from the surface @xmath2 , _ independent _ of the bulk electron density , which is exactly half the corresponding exact - exchange potential @xmath3 [ phys .
rev .
lett . * 97 * , 026802 ( 2006 ) ] of density - functional theory , as occurs in the case of finite systems .
the fitting of @xmath4 to a physically motivated image - like expression is feasible , but the resulting location of the image plane shows strong finite - size oscillations every time a slab discrete energy level becomes occupied . for a semi - infinite jellium , the asymptotic behavior of @xmath5 is somehow different . as in the case of jellium slabs
@xmath6 has an image - like behavior of the form @xmath7 , but now with a density - dependent coefficient that in general differs from the slab universal coefficient @xmath8 . our numerical estimates for this coefficient agree with two previous analytical estimates for the same .
for an arbitrary finite thickness of a jellium slab , we find that the asymptotic limits of @xmath4 and @xmath5 only coincide in the low - density limit ( @xmath9 ) , where the density - dependent coefficient of the semi - infinite jellium approaches the slab _ universal _ coefficient 1/2 . .
And you have already written the first three sentences of the full article: the jellium model of a metal surface , introduced by bardeen in 1936 , @xcite is the simplest model which reproduces qualitatively , and sometimes quantitatively , the physical properties of real metal surfaces .
@xcite while in his work bardeen applied an approximated hartree - fock ( hf ) theory for the study of the electronic structure , since the seminal work of lang and kohn ( lk ) @xcite the standard theoretical tool applied to the study of the electronic structure of metal surfaces has been density - functional theory ( dft ) .
@xcite as in the original work of lang and kohn , most of the subsequent investigations have applied the local - density approximation ( lda ) of dft , or some of its semi - local variants ( gga , meta - gga , etc . ) ..
Please generate the next two sentences of the article | this approach has been highly successful , and routinely yields good results for global surface properties such as work functions , surface energies , crystal - structure relaxation and reconstruction , etc .
@xcite at a more basic level , however , some problems still remain to be solved , concerning for instance the asymptotic behavior of the exchange - correlation ( _ xc _ ) potential of the widely used kohn - sham ( ks ) approach to dft . in the lda |
3,888 | Suppose that you have an abstract for a scientific paper: i review constraints on the radial density profiles and ellipticities of the dark matter obtained from recent x - ray observations with _
chandra _ and _ xmm _ of elliptical galaxies and galaxy clusters and discuss their implications , especially for the self - interacting dark matter model .
# 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: for many years x - ray astronomers have promised to obtain accurate constraints on dark matter in clusters of galaxies and elliptical galaxies .
but because of the frustrating limitations of previous x - ray telescopes , only for a very few objects notably m87 have precise measurements been possible .
it is really a great pleasure to give this review because the promises made many years ago are finally being realized in this wonderful era of x - ray astronomy , where the _ chandra _ and _ xmm _ observatories are operating so successfully ..
Please generate the next two sentences of the article | _ chandra _ and _ xmm _ have provided for the first time high quality , spatially resolved spectra of the diffuse hot gas of galaxies and clusters because their ccds combine moderate resolution spectra with very much improved spatial resolution and sensitivity .
_ chandra _ provides a more significant jump in spatial resolution while xmm provides a more substantial boost in sensitivity . as a result of these improved capabilities , accurate measurements of the gas temperature as |
3,889 | Suppose that you have an abstract for a scientific paper: the schechter - valle theorem states that a positive observation of neutrinoless double - beta ( @xmath0 ) decays implies a finite majorana mass term for neutrinos when any unlikely fine - tuning or cancellation is absent . in this note , we reexamine the quantitative impact of the schechter - valle theorem , and find that current experimental lower limits on the half - lives of @xmath0-decaying nuclei have placed a restrictive upper bound on the majorana neutrino mass @xmath1 radiatively generated at the four - loop level . furthermore , we generalize this quantitative analysis of @xmath0 decays to that of the lepton - number - violating ( lnv ) meson decays @xmath2 ( for @xmath3 , @xmath4 = @xmath5 or @xmath6 ) .
given the present upper limits on these rare lnv decays , we have derived the loop - induced majorana neutrino masses @xmath7 , @xmath8 and @xmath9 from @xmath10 , @xmath11 and @xmath12 , respectively .
a partial list of radiative neutrino masses from the lnv decays of @xmath13 , @xmath14 and @xmath15 mesons is also given .
* majorana neutrino masses from neutrinoless double - beta decays and lepton - number - violating meson decays * * jun - hao liu @xmath16 * + @xmath17institute of high energy physics , chinese academy of sciences , beijing 100049 , china + @xmath18center for high energy physics , peking university , beijing 100871 , china pacs number(s ) : 11.30.fs , 12.15.lk , 14.60.lm .
And you have already written the first three sentences of the full article: it remains an open question whether massive neutrinos are majorana particles , whose antiparticles are themselves @xcite . the final answer to this fundamental question will tell us whether the lepton number is conserved or not in nature , and help us explore the origin of neutrino masses .
currently , the most promising way to answer if massive neutrinos are their own antiparticles is to observe the @xmath0 decays @xmath19 , where @xmath20 and @xmath21 stand respectively for the atomic and mass numbers of a nuclear isotope @xmath22 @xcite . over the last few decades
, a great number of dedicated experiments have been carried out to search for this kind of decays @xcite ..
Please generate the next two sentences of the article | so far , we have not observed any positive signals , and a lower bound on the half - life of the implemented nuclear isotope can be drawn from experimental data .
the gerda phase - i experiment @xcite has disproved the signals of @xmath23 decays claimed by the heidelberg - moscow experiment @xcite , and the joint lower bound from all the previous @xmath24-based experiments on the half - life turns out to be @xmath25 at the @xmath26 confidence level @xcite . for @xmath27-based experiments , |
3,890 | Suppose that you have an abstract for a scientific paper: the strongly - coupled phase of the quark - gluon plasma ( qgp ) is studied here by resorting to a @xmath0-matrix formulation in which the medium is seen as a non - ideal gas of quasiparticles ( quarks , antiquarks and gluons ) interacting nonpertubatively . in the temperature range under study , ( 1 - 5 ) @xmath1 , where @xmath1 is the temperature of deconfinement , the interactions are expected to be strong enough to generate bound states .
the dissociation temperature of such binary bound states is thus computed here .
the more the quasiparticles involved in the binary system are heavy , the more the bound state is likely to survive significantly above @xmath1 .
then , the qgp equations of state at zero and small baryonic potential are computed for @xmath2 and @xmath3 by resorting to the dashen , ma and bernstein formulation of statistical mechanics .
comparisons with current lattice qcd data are presented . .
And you have already written the first three sentences of the full article: the phenomenology related to the qcd confinement / deconfinement phase transition is nowadays a fascinating subject in the center of intense investigations , both experimentally and theoretically ( see _ e.g. _
@xcite for a review of the topic ) . during the last two decades , a new state of matter
, the quark - gluon plasma ( qgp ) , has been intensively studied through heavy - ion collisions ( sps , rhic or lhc ) and is still carefully analysed ..
Please generate the next two sentences of the article | the experiments seem to conclude that the qgp behaves like a perfect fluid with a low ratio viscosity over entropy around the critical temperature of deconfinement @xmath1 .
therefore , this observation suggests that a strongly - coupled phase ( called sqgp ) is present in this temperature range and that the qcd confinement / deconfinement phase transition is much more driven by screening effects of the strong interaction . in order to correctly describe the different mechanisms at work during this phase transition , or more exactly during this crossover , |
3,891 | Suppose that you have an abstract for a scientific paper: we propose a phantom crossing dvali gabadadze porrati ( dgp ) model . in our model ,
the effective equation of state of the dgp gravity crosses the phantom divide line .
we demonstrate crossing of the phantom divide does not occur within the framework of the original dgp model or the dgp model developed by dvali and turner . by extending their model , we construct a model that realizes crossing of the phantom divide .
we find that the smaller the value of the new introduced parameter @xmath0 is , the older epoch crossing of the phantom divide occurs in .
our model can account for late - time acceleration of the universe without dark energy .
we investigate and show the property of phantom crossing dgp model .
example.eps gsave newpath 20 20 moveto 20 220 lineto 220 220 lineto 220 20 lineto closepath 2 setlinewidth gsave .4 setgray fill grestore stroke grestore .
And you have already written the first three sentences of the full article: late time accelerated expansion of the universe was indicated by measurements of distant type ia supernovae ( sne ia ) @xcite . this was confirmed by observations of cosmic microwave background ( cmb ) anisotropies by the wilkinson microwave anisotropy probe ( wmap ) @xcite , and the large - scale structure in the distribution of galaxies observed in the sloan digital sky survey ( sdss ) @xcite .
it is not possible to account for this phenomenon within the framework of general relativity containing only matter .
therefore , a number of models containing `` dark energy '' have been proposed as the mechanism for the acceleration ..
Please generate the next two sentences of the article | there are currently many dark energy models , including cosmological constant , scalar field , quintessence , and phantom models @xcite .
however , dark energy , the nature of which remains unknown , has not been detected yet . |
3,892 | Suppose that you have an abstract for a scientific paper: massive black holes appear to be present in the nuclei of almost all galaxies , but their genesis and evolution are not well understood . as astrophysical black holes
are completely characterized by their masses and spins , the observed joint distribution of these quantities contains important clues to their history .
we examine the coevolution of mass and spin in binary merger growth scenarios .
we find that holes are typically spun _ down _ by mergers .
rapid rotation results only if the binary s larger member already spins quickly and the merger with the smaller hole is consistently near prograde ; or , if the binary s mass ratio approaches unity .
if , as some observations have suggested , observed black holes spin rapidly , then this limits the importance of merger scenarios for the growth of black holes . .
And you have already written the first three sentences of the full article: black holes span a wide spectrum of masses : the case for stellar mass holes ( @xmath0 ) in the field [ e.g. , @xcite ] and supermassive holes ( @xmath1 ) in galactic bulges [ e.g. , @xcite ] is extremely strong ; tantalizing evidence suggests middleweight holes ( @xmath2 ) as well @xcite .
stellar mass holes likely form in stellar collapse ; the origins of more massive holes remains mysterious .
such holes could form in the collapse of massive gas accumulations ; they could grow from smaller holes by accretion ; they could grow by capturing stellar mass bodies ; and they could grow by repeatedly merging with holes of comparable mass ..
Please generate the next two sentences of the article | any or indeed all of these mechanisms could contribute to the growth of a given hole .
a black hole s spin may help identify which scenario most strongly impacted its recent history . since spin likely drives outflows and jets in active galaxies , and since jets are presumed to align with black hole spin @xcite , spin may provide an observational probe of a hole s recent growth @xcite . |
3,893 | Suppose that you have an abstract for a scientific paper: this paper shows an optimal spreading sequence in the weyl sequence class belonging to the extended frank - zadoff - chu ( fzc ) sequence family .
the sequences in this class have the desired property that the order of crosscorrelation is low .
we evaluate the upper bound of crosscorrelation in the class and construct the optimization problem .
then , we derive the optimal spreading sequences as the global solution of the problem and show their snr in a special case . from this result , we propose how the initial elements are assigned , that is , how spreading sequences are assigned to each users .
we also numerically compare our spreading sequences with other ones , the gold codes , the sequences of the fzc sequence families , the optimal chebyshev spreading sequences and the sp sequences in bit error rate .
submitted paper spread spectrum communication , nonlinear programming , spreading sequence , signal to noise ratio , bit error rate .
And you have already written the first three sentences of the full article: ( snr ) is an important index for wireless communication systems . in wireless communication systems , it is the most significant to achieve high capacity @xcite . in general , it is necessary and sufficient for achieving high capacity to increase snr under the condition that the width of the frequency band is constant @xcite .
similary , the performance of wireless communication is evaluated in bit error rate ( ber ) .
however , these two are not independent , and it is known that ber decreases as snr increases . as a wireless communication system ,.
Please generate the next two sentences of the article | we focus on a code division multiple access ( cdma ) system @xcite , in particular , an asynchronous cdma system .
it is one of the multiple access systems with which many people can communicate each other at the same time @xcite . in cdma systems , spreading sequences are utilized as codes to multiplex . each user is assigned a different code and uses it to modulate and demodulate his signal . in cdma systems , |
3,894 | Suppose that you have an abstract for a scientific paper: isolation of a single atomic particle and monitoring its resonance fluorescence is a powerful tool for studies of quantum effects in radiation - matter interaction . here
we present observations of quantum dynamics of an isolated neutral atom stored in a magneto - optical trap . by means of photon correlations in the atom s resonance fluorescence we demonstrate the well - known phenomenon of photon antibunching which corresponds to transient rabi oscillations in the atom . through polarization - sensitive photon correlations
we show a novel example of resolved quantum fluctuations : spontaneous magnetic orientation of an atom .
these effects can only be observed with a single atom .
keywords : laser cooling and trapping , single atoms , photon correlations , quantum fluctuations .
And you have already written the first three sentences of the full article: radiation matter interaction has been studied for a long time with atomic samples .
it is known that density matrix theory is well suited to exhaustively describe the properties of fluorescence from macroscopic atomic ensembles , and that in this limit semiclassical theory gives excellent approximations , since phenomena related to the quantum nature of the light field are often hidden . on the other hand ,
it has also been realized since more than two decades now that isolation of a single atom provides an opportunity to directly observe pure quantum properties of the interacting radiation - matter system ..
Please generate the next two sentences of the article | a celebrated example is the observation of photon antibunching , where initial experiments @xcite were carried out with extremely diluted atomic beams , and more precise investigations became possible when ion traps were employed to achieve long - term confinement of a single atomic particle @xcite . for neutral atoms
the confinement strength is reduced since trapping has to rely on forces derived from electric or magnetic dipole interaction . |
3,895 | Suppose that you have an abstract for a scientific paper: the study of the inelastic scattering of hadrons has progressed in the last decade . with the availability of high - statistics data sets from hera and the tevatron ,
our understanding of high energy and high jet multiplicity events has become rather precise . in this proceedings ,
i present an overview of recent jet - only results , as well as measurements of events which combine both jets and a @xmath0 or @xmath1 boson . .
And you have already written the first three sentences of the full article: the study of the interactions between the quark and gluon constituents of hadrons has evolved over the past several decades .
experiments once had large systematic and statistical uncertainties and theoretical predictions used only leading - order perturbation theory .
however our understanding has considerably improved and precise measurements and calculations are now available ..
Please generate the next two sentences of the article | the theory of the strong interactions , called quantum chromodynamics or qcd @xcite , is a very interesting one in its own right . in addition , because these kinds of interactions dominate at a hadron collider , they form a substantial background for other interesting possible physical processes , including top quark and higgs boson production , as well as other potential new pheneomena , such as models incorporating the principle of supersymmetry . in these proceedings
, we present recent qcd results , focusing predominantly on data taken at the fermilab tevatron . |
3,896 | Suppose that you have an abstract for a scientific paper: i describe scalar glueballs in the soft wall model of holographic qcd ( ads / qcd ) .
[ 1999/12/01 v1.4c il nuovo cimento ] .
And you have already written the first three sentences of the full article: recently , a lot of interest has grown around the possibility of applying string inspired techniques to the non - perturbative regime of qcd .
the starting point is the ads / cft correspondence @xcite , a conjectured duality between a maximally supersymmetric strongly coupled conformal field theory and the supergravity limit of type iib string theory , which involves theories different from qcd .
further developments @xcite have tried to apply the correspondence to qcd , induced by the evidence of the existence of a window of energy in which qcd shows an approximate conformal behaviour @xcite ..
Please generate the next two sentences of the article | these developments have taken different directions .
the framework through which i move here is the so - called soft wall model of ads / qcd @xcite , a phenomenological model originally built to holographically describe chiral symmetry breaking and then adapted to several strong interaction processes . for a list of other approaches the reader can refer to @xcite . in the following , |
3,897 | Suppose that you have an abstract for a scientific paper: _ spitzer space telescope _ spectra reveal 10 @xmath0 m silicate emission from circumstellar dust orbiting six externally - polluted white dwarfs . micron - size glasses with an olivine stoichiometry can account for the distinctively broad wings that extend to 12 @xmath0 m ;
these particles likely are produced by tidal - disruption of asteroids .
the absence of infrared pah features is consistent with a scenario where extrasolar rocky planets are assembled from carbon - poor solids . .
And you have already written the first three sentences of the full article: approximately 1 - 3% of single white dwarfs with cooling ages less than 0.5 gyr possess an infrared excess resulting from a circumstellar disk ( farihi et al .
these same stars also have distinctively high atmospheric calcium abundances ( kilic et al . 2006 , jura et al .
2007a ) even though photospheric metals normally are absent in white dwarfs in this temperature range ( zuckerman et al ..
Please generate the next two sentences of the article | the disks likely are caused by the tidal disruption of asteroids , and there is subsequent metal accretion onto the white dwarfs ( see jura 2008 ) .
polluted white dwarfs and their disks are powerful tools to investigate extrasolar asteroids the building blocks of extrasolar rocky planets . |
3,898 | Suppose that you have an abstract for a scientific paper: we propose two new methods for estimating the number of clusters in a hierarchical clustering framework in the hopes of creating a fully automated process with no human intervention .
the methods are completely data - driven and require no input from the researcher , and as such are fully automated .
they are quite easy to implement and not computationally intensive in the least .
we analyze performance on several simulated data sets and the biobase gene expression set , comparing our methods to the established gap statistic and elbow methods and outperforming both in multi - cluster scenarios . shell : bare demo of ieeetran.cls for journals clustering , hierarchy , dendrogram , gene expression , empirical . .
And you have already written the first three sentences of the full article: clustering analysis ( or hca ) is an extensively studied field of unsupervised learning . very useful in dimensionality reduction problems , we will study ways of using this clustering method with the aim of reducing ( or removing ) the need for human intervention .
this problem of human intervention stems from the fact that hca is used when we do not know the correct number of clusters in our data ( otherwise we might use , say , k - means ) .
while the ability to cluster data with an unknown number of clusters is a powerful one , we often need a researcher to interpret the results - or cutoff the algorithm - to recover a meaningful cluster number ..
Please generate the next two sentences of the article | while our motivation stems from dna micro - array data and gene expression problems , these methods can apply to any similarly structured scenario . specifically
, we will analyze different existing automated methods for cutting off hca and propose two new ones . in section ii we will discuss background material on hca and the existing methods and in section iii we will present some technical details on these methods and introduce our own . |
3,899 | Suppose that you have an abstract for a scientific paper: recently it has been proposed that dark matter axions from the galactic halo can produce a small shapiro step - like signal in josephson junctions whose josephson frequency resonates with the axion mass [ c. beck , prl 111 , 231801 ( 2013 ) ] . here
we show that the axion field equations in a voltage - driven josephson junction environment allow for a nontrivial solution where the axion - induced electrical current manifests itself as an oscillating supercurrent .
the linear change of phase associated with this nontrivial solution implies the formal existence of a large magnetic field in a tiny surface area of the weak link region of the junction which makes incoming axions decay into microwave photons .
we derive a condition for the design of josephson junction experiments so that they can act as optimum axion detectors .
four independent recent experiments are discussed in this context .
the observed shapiro step anomalies of all four experiments consistently point towards an axion mass of @xmath0ev .
this mass value is compatible with the recent bicep2 results and implies that peccei - quinn symmetry breaking was taking place after inflation . .
And you have already written the first three sentences of the full article: about 95% of the energy contents of the universe appears to be of unknown origin , in the form of dark matter and dark energy . while there is a lot of astrophysical evidence for the existence of dark matter and dark energy , a deeper understanding of the physical nature of these main ingredients of the universe is still lacking .
clearly it is important to design new experiments on earth that could have the potential to unravel some of the unknown physics underlying dark matter and dark energy . at the particle physics level
, there are two main candidates what dark matter could be ..
Please generate the next two sentences of the article | these are wimps ( weakly interacting massive particles ) @xcite and axions @xcite .
wimps are motivated by supersymmetry , whereas axions are motivated by the solution of the strong cp problem in qcd . |
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