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9,400 | Suppose that you have an abstract for a scientific paper: this paper investigates the relationship between base station ( bs ) density and average spectral efficiency ( se ) in the downlink of a cellular network .
this relationship has been well known for sparse deployment , i.e. when the number of bss is small compared to the number of users . in this case
the se is independent of bs density .
as bs density grows , on the other hand , it has previously been shown that increasing the bs density increases the se , but no tractable form for the se - bs density relationship has yet been derived . in this paper
we derive such a closed - form result that reveals the se is asymptotically a logarithmic function of bs density as the density grows .
further , we study the impact of this result on the network operator s profit when user demand varies , and derive the profit maximizing bs density and the optimal amount of spectrum to be utilized in closed forms . in addition
, we provide deployment planning guidelines that will aid the operator in his decision if he should invest in densifying his network or in acquiring more spectrum . ultra - dense cellular network , base station density , average spectral efficiency , spectrum amount , profit maximization , stochastic geometry , network economics . .
And you have already written the first three sentences of the full article: deploying more cellular base stations ( bs ) has been the main remedy to cope with relentless traffic growth . to reach the highest capacities ,
interest has lately been turning toward ultra - dense bs deployment @xcite , @xcite , where the density of bs may even exceed the typical number of users in a given area .
the impact of such extreme bs densification , however , has still not been explicitly analyzed . to be more specific , in an engineering perspective , the preceding work @xcite provides an analytic average spectral efficiency ( se ) calculation that reveals the se is independent of bs density ..
Please generate the next two sentences of the article | the result is accurate only when bs density is low as it relies on an assumption that every bs has at least a single serving user . for densely deployed bs environment ,
the authors @xcite consider turned - off bss when having no serving users as in the third generation partnership project ( 3gpp ) release 12 specifications @xcite , and predict the se is a logarithmic function of bs density via its compatible performance metrics , service capacity , outage probability , and common ( worst user s ) rate respectively . |
9,401 | Suppose that you have an abstract for a scientific paper: this is a very brief summary of the techniques i used to analyze the ipta challenge 1 data sets .
i tried many things , and more failed than succeeded , but in the end i found two approaches that appear to work based on tests done using the open data sets .
one approach works directly with the time domain data , and the other works with a specially constructed fourier transform of the data .
the raw data was run through tempo2 to produce reduced timing residuals for the analysis .
standard markov chain monte carlo techniques were used to produce samples from the posterior distribution function for the model parameters .
the model parameters include the gravitational wave amplitude and spectral slope , and the white noise amplitude for each pulsar in the array .
while red timing noise was only included in dataset 3 , i found that it was necessary to include effective red noise in all the analyses to account for some of the spurious effects introduced by the tempo2 timing fit .
this added an additional amplitude and slope parameter for each pulsar , so my overall model for the 36 pulsars residuals has 110 parameters . as an alternative to using an effective red noise model , i also tried to simultaneously re - fit the timing model model while looking for the gravitational wave signal , but for reasons that are not yet clear , this approach was not very successful .
i comment briefly on ways in which the algorithms could be improved .
my best estimates for the gravitational wave amplitudes in the three closed ( blind ) data sets are : ( 1 ) @xmath0 ; ( 2 ) @xmath1 ; and ( 3 ) @xmath2 . .
And you have already written the first three sentences of the full article: a description of the ipta data challenge and the data sets can be found at _ http://www.ipta4gw.org/_. the first round consisted of three parts - datasets 1,2 , and 3 , each with one open data set for testing purposes and one closed data set as a blind challenge .
the datasets were arranged in increasing order of difficulty , starting with evenly sampled data with bright gravitational wave signals and moving on to unevenly sampled data with weak gravitational wave signals .
the ipta data challenges are similar to the mock lisa data challenges @xcite , the main difference being that the people that put this challenge together have real detectors to work with as well ..
Please generate the next two sentences of the article | my approach to the analysis was to use bayesian inference and markov chain monte carlo sampling to produce posterior distributions for the gravitational wave amplitude and the pulsar timing noise .
the bayesian approach requires a noise model - which fixes the form of the likelihood - a signal model , and priors on the model parameters . for stationary , gaussian noise |
9,402 | Suppose that you have an abstract for a scientific paper: this paper describes an approach for half - duplex cooperative transmission in a classical three - node relay channel . assuming availability of channel state information at nodes , the approach makes use of this information to optimize distinct flows through the direct link from the source to the destination and the path via the relay , respectively .
it is shown that such a design can effectively harness diversity advantage of the relay channel in both high - rate and low - rate scenarios .
when the rate requirement is low , the proposed design gives a second - order outage diversity performance approaching that of full - duplex relaying .
when the rate requirement becomes asymptotically large , the design still gives a close - to - second - order outage diversity performance .
the design also achieves the best diversity - multiplexing tradeoff possible for the relay channel . with optimal long - term power control over the fading relay channel ,
the proposed design achieves a delay - limited rate performance that is only @xmath0db ( @xmath1db ) worse than the capacity performance of the additive white gaussian channel in low- ( high- ) rate scenarios . .
And you have already written the first three sentences of the full article: it is well known that the performance of a wireless network can be significantly improved by cooperative transmission among nodes in the network .
many cooperative transmission designs aim to exploit cooperative diversity that is inherently present in the network .
such designs have been suggested in @xcite for cellular networks ..
Please generate the next two sentences of the article | recently there has been much interest in achieving cooperative diversity in a classical three - node relay channel @xcite , which represents the simplest wireless network that can derive advantages from cooperative transmission .
the relay channel has been thoroughly studied in @xcite . |
9,403 | Suppose that you have an abstract for a scientific paper: we discuss spectra calculated for the 2d hubbard model in the intermediate coupling regime with the dynamical cluster approximation , which is a non - perturbative approach .
we find a crossover from a normal fermi liquid with a fermi surface closed around the brillouin zone center at large doping to a non - fermi liquid for small doping .
the crossover is signalled by a splitting of the fermi surface around the @xmath0 point of the @xmath1 brillouin zone , which eventually leads to a hole - like fermi surface closed around the point @xmath2 .
the topology of the fermi surface at low doping indicates a violation of luttinger s theorem .
we discuss different ways of presenting the spectral data to extract information about the fermi surface .
a comparison to recent experiments will be presented . .
And you have already written the first three sentences of the full article: the rich phenomenology of high-@xmath3 superconductors @xcite has stimulated strong experimental and theoretical interest in the field of strongly correlated electron systems .
apart from the anomalously high transition temperatures , these compounds are also of interest due to their unusual normal state properties .
most of these anomalous properties are found in spectra and transport quantities , i.e. are intimately linked to the dynamics of the electronic degrees of freedom ..
Please generate the next two sentences of the article | thus , much of the experimental and theoretical effort has concentrated on the development of an understanding of the single - particle dynamics . among the fundamental and controversial questions are whether the cuprates can be described as a fermi liquid or not and what shape and volume a possible fermi surface will have . in this connection ,
one of the most informative experimental probes of the cuprates has become the angle - resolved photoemission spectroscopy(arpes ) . |
9,404 | Suppose that you have an abstract for a scientific paper: we consider a peak - power - limited single - antenna block - stationary gaussian fading channel where neither the transmitter nor the receiver knows the channel state information , but both know the channel statistics .
this model subsumes most previously studied gaussian fading models .
we first compute the asymptotic channel capacity in the high snr regime and show that the behavior of channel capacity depends critically on the channel model .
for the special case where the fading process is symbol - by - symbol stationary , we also reveal a fundamental interplay between the codeword length , communication rate , and decoding error probability .
specifically , we show that the codeword length must scale with snr in order to guarantee that the communication rate can grow logarithmically with snr with bounded decoding error probability , and we find a necessary condition for the growth rate of the codeword length .
we also derive an expression for the capacity per unit energy .
furthermore , we show that the capacity per unit energy is achievable using temporal on - off signaling with optimally allocated on symbols , where the optimal on - symbol allocation scheme may depend on the peak power constraint . wireless channels , noncoherent capacity , capacity per unit cost , block fading .
And you have already written the first three sentences of the full article: the capacity analysis of _ noncoherent _ fading channels has received considerable attention in recent years since it provides the ultimate limit on the rate of reliable communication on such channels .
proposed approaches to modeling noncoherent fading channels can be classified into two broad categories . the first is to model the fading process as a _ block - independent _ process . in the standard version of this model@xcite ,
the channel remains constant over blocks consisting of @xmath0 symbol periods , and changes independently from block to block ..
Please generate the next two sentences of the article | the second is to model the fading process as a symbol - by - symbol _ stationary _ process . in this model
, the independence assumption is removed , but the block structure is not allowed . somewhat surprisingly , these two models lead to very different capacity results . for the standard block fading model , |
9,405 | Suppose that you have an abstract for a scientific paper: we present a new fit to the lear data on @xmath0 differential cross sections and analyzing powers motivated by relativistic considerations . within a quark model describing this annihilation
we argue , since the pions are highly energetic , that relativistic effects can not be neglected .
the intrinsic pion wave functions are lorentz transformed to the center of mass frame .
this change in quark geometry gives rise to additional angular dependence in the transition operators and results in a relative enhancement of higher @xmath1 partial wave amplitudes .
the fit to the data is improved significantly . .
And you have already written the first three sentences of the full article: we recently studied effects of particle size and final - state interactions in the reaction @xmath0 within the framework of a constituent quark model @xcite .
the aim was to improve previous attempts @xcite to describe the lear data on @xmath0 differential cross sections @xmath2 and analyzing powers @xmath3 in the momentum range from 360 to 1550 mev/@xmath4 @xcite .
as of yet , theoretical approaches , whether using a baryonic or a quark picture @xcite , have not been successful in reproducing the characteristic double - dip structure of the @xmath3 observables nor the @xmath2 forward peaks at low momenta ..
Please generate the next two sentences of the article | the large variations of the lear observables as a function of the angle portends the presence of a substantial number of partial wave amplitudes already at low energies .
in fact , the experimental data on differential cross sections as well as those on asymmetries point to a significant @xmath5 , @xmath6 and even higher @xmath7 contributions @xcite . |
9,406 | Suppose that you have an abstract for a scientific paper: when a sinusoidal ( ac ) field is applied to a suspension containing nonlinear dielectric particles , the electrical response will generally consist of ac fields at frequencies of the higher - order harmonics .
the situation is further complicated by an intrinsic dielectric dispersion which often occurs due to the surface conductivity or inhomogeneous structure of the particles .
we perform a perturbation method to investigate the effect of intrinsic dielectric dispersion on the harmonics of local field as well as induced dipole moment .
the results showed , for weak intrinsic dispersion strength , the ratio of the third to first harmonics of the induced dipole moment decreases as the frequency increases , which is qualitatively in agreement with experimental result .
however , for a strong dispersion strength , the harmonics ratio increases as the frequency increases .
moreover , an increase in the intrinsic relaxation time may increase the strength of harmonics . .
And you have already written the first three sentences of the full article: when an intense electric field is applied to a suspension containing highly polarized particled embedded in a host fluid , the particles will form chains due to the induced dipole moments inside the particles , and hence complex anisotropic structures occur .
also , the apparent viscosity of the suspension will be enhanced greatly .
these structures can have anisotropic physical properties , such as the effective conductivity and permittivity @xcite . in this case ,.
Please generate the next two sentences of the article | optical nonlinearity enhancement was found as well @xcite .
a convenient method of probing the nonlinear characteristics of the field - induced structures is to measure the harmonics of the nonlinear polarization under the application of a sinusoidal ( ac ) electric field @xcite . |
9,407 | Suppose that you have an abstract for a scientific paper: we introduce a stability criterion for quantum statistical ensembles describing macroscopic systems .
an ensemble is called `` stable '' when a small number of local measurements can not significantly modify the probability distribution of the total energy of the system .
we apply this criterion to lattices of spins-1/2 , thereby showing that the canonical ensemble is nearly stable , whereas statistical ensembles with much broader energy distributions are not stable . in the context of the foundations of quantum statistical physics ,
this result justifies the use of statistical ensembles with narrow energy distributions such as canonical or microcanonical ensembles . .
And you have already written the first three sentences of the full article: an isolated classical system always has a fixed value of the total energy .
in contrast , an isolated quantum system can be in a superposition of states with different total energies @xcite .
this entails the following difficulty for the foundations of statistical physics : a typical isolated macroscopic quantum system is generally expected to thermalise under the action of its internal dynamics for the overwhelming majority of initial nonequilibrium states appearing in nature or created in a laboratory ..
Please generate the next two sentences of the article | thermalisation implies that the density matrix of any small subsystem within the large system approaches a form consistent with the canonical gibbs density matrix ( canonical ensemble ) for the large system . a necessary condition for an isolated many - particle quantum system to thermalise is a sufficiently narrow initial probability distribution of its total energy , as is , for example , the case for the canonical and the microcanonical statistical ensembles ( see below ) . at the same time , for an isolated quantum system , the probability of occupying an energy eigenstate remains unchanged with time .
thus , a large isolated quantum system with a broad initial distribution of the total energy thermalises not to a conventional equilibrium state with a well - defined temperature but rather to a mixture or superposition of states with different temperatures . |
9,408 | Suppose that you have an abstract for a scientific paper: i introduce a new type of continuous - time quantum walk on graphs called the quantum snake walk , the basis states of which are fixed - length paths ( snakes ) in the underlying graph .
first i analyze the quantum snake walk on the line , and i show that , even though most states stay localized throughout the evolution , there are specific states which most likely move on the line as wave packets with momentum inversely proportional to the length of the snake .
next i discuss how an algorithm based on the quantum snake walk might potentially be able to solve an extended version of the glued trees problem which asks to find a path connecting both roots of the glued trees graph .
no efficient quantum algorithm solving this problem is known yet . .
And you have already written the first three sentences of the full article: in 1994 , shor s ground - breaking paper presented an efficient quantum algorithm for integer factoring @xcite .
many other very important results have followed , but the true potential of quantum computers is still unknown .
one step towards understanding it is to consider what are the differences between quantum and classical computers in a setting where we are given the input via a black - box oracle . because we can not know the inner workings of the oracle , it is easier to prove lower bounds in this model and.
Please generate the next two sentences of the article | therefore in many cases it is easier to show a separation between the best quantum and classical algorithms .
ever since deutsch presented a simple oracle problem that can be solved on a quantum computer using fewer oracle queries than on any classical computer @xcite , scientists have tried to come up with more and more problems for which quantum computers outperform their classical counterparts ; some very artificial , some quite natural . |
9,409 | Suppose that you have an abstract for a scientific paper: we analyze numerically the critical behavior of an absorbing phase transition in the conserved transfer threshold process . we determined the steady state scaling behavior of the order parameter as a function of both , the control parameter and an external field , conjugated to the order parameter .
the external field is realized as a spontaneous creation of active particles which drives the system away from criticality .
the obtained results yields that the conserved transfers threshold process belongs to the universality class of absorbing phase transitions in a conserved field . .
And you have already written the first three sentences of the full article: the scaling behavior of directed percolation is recognized as the paradigm of the critical behavior of several non - equilibrium systems which exhibits a continuous phase transition from an active state to an absorbing non - active state ( see for instance @xcite ) .
the widespread occurrence of such systems in physics , biology , as well as catalytic chemical reactions is reflected by the well known universality hypothesis of janssen and grassberger that models which exhibit a continuous phase transition to a single absorbing state generally belong to the universality class of directed percolation @xcite . introducing additional symmetries
the critical behavior differs from directed percolation ..
Please generate the next two sentences of the article | in particular particle conservation leads to the different universality class of absorbing phase transitions with a conserved field as pointed out in @xcite . in that work the authors introduced two models , the conserved lattice gas ( clg ) and the conserved threshold transfer process ( cttp ) .
the latter one is a conserved modification of the threshold transfer process introduced in @xcite . |
9,410 | Suppose that you have an abstract for a scientific paper: shell galaxies are considered the debris of recent accretion / merging episodes . their high frequency in low density environments suggest that such episodes could drive the secular evolution for at least some fraction of the early - type galaxy population .
we present here the preliminary results of ultraviolet and x - ray data for a sample of three shell galaxies , namely ngc 474 , ngc 7070a and eso 2400100 .
the far uv morphology and photometry are derived using the observations obtained with the _ galaxy evolution explorer _ and the xmm-_newton _ optical monitor .
we aim at investigating the _ rejuvenation _ processes in the stellar population using the uv information as well as at gaining information about the possible evolution with time of the x - ray emission due interaction / merging processes . .
And you have already written the first three sentences of the full article: in a hierarchical evolutionary scenario , galaxies experience accretion / merging events during their lifetime . while early - type galaxies in nearby clusters appear ( homogeneously ) old , the field early - type galaxy population seems to contain genuinely , recently _ rejuvenated _ objects ( see e.g. * ? ? ? * ) .
early - type galaxies showing fine structure , like shells , occupy a special position since they are believed to fill the gap between ongoing mergers and normal elliptical galaxies .
shells are faint , sharp - edged stellar features characterizing @xmath0 16.5% of the field early - type galaxy population and avoiding cluster environments ( e.g. * ? ? ?.
Please generate the next two sentences of the article | * ; * ? ? ?
* ; * ? ? ? |
9,411 | Suppose that you have an abstract for a scientific paper: measurement of the @xmath0 oscillation frequency via @xmath0 mixing analyses provides a powerful constraint on the ckm matrix elements .
the study of @xmath1 oscillations is an important step towards @xmath0 mixing and a preliminary measurement of @xmath2 has been made with @xmath3 250 pb@xmath4 of data collected with the upgraded run ii d detector .
different flavor tagging algorithms have been developed and are being optimized for use on a large set of @xmath0 mesons that have been reconstructed in different semileptonic decay modes .
= 14.5pt .
And you have already written the first three sentences of the full article: first observed in the @xmath5 meson system at argus , the neutral b meson transition from the particle to anti - particle state , and vice versa , occurs through a second order weak transition or `` box diagram '' .
the frequency of the oscillation is proportional to the small difference in mass between the two eigenstates , @xmath6 , and for the @xmath5 system can be translated into a measurement of the ckm element @xmath7 .
@xmath7 can be used to constrain the unitarity triangle and thereby yield information on the _ cp _ violating phase @xcite ..
Please generate the next two sentences of the article | @xmath2 has been precisely measured ( the world average is @xmath8 @xcite ) but large theoretical uncertainties dominate the extraction of @xmath7 from @xmath2 . this problem can be reduced if the @xmath9 mass difference , @xmath10 , is also measured .
@xmath7 can then be extracted with better precision from the ratio : @xmath11 where @xmath12 is estimated from lattice qcd calculations to be @xmath13 @xcite . |
9,412 | Suppose that you have an abstract for a scientific paper: we investigate the possible origin of extended emissions ( ees ) of short gamma - ray bursts with an isotropic energy of @xmath0 and a duration of a few 10 s to @xmath1 , based on a compact binary ( neutron star ( ns)-ns or ns - black hole ( bh ) ) merger scenario .
we analyze the evolution of magnetized neutrino - dominated accretion disks of mass @xmath2 around bhs formed after the mergers , and estimate the power of relativistic outflows via the blandford - znajek ( bz ) process .
we show that a rotation energy of the bh up to @xmath3 can be extracted with an observed time scale of @xmath4 with a relatively small disk viscosity parameter of @xmath5 .
such a bz power dissipates by clashing with non - relativistic pre - ejected matter of mass @xmath6 , and forms a mildly relativistic fireball .
we show that the dissipative photospheric emissions from such fireballs are likely in the soft x - ray band ( @xmath7 ) for @xmath8 possibly in ns - ns mergers , and in the bat band ( @xmath9 ) for @xmath10 possibly in ns - bh mergers . in the former case
, such soft ees can provide a good chance of @xmath11 for simultaneous detections of the gravitational waves with a @xmath12 angular resolution by soft x - ray survey facilities like wide - field maxi . here
, @xmath13 is the beaming factor of the soft ees and @xmath14 is the ns - ns merger rate detectable by advanced ligo , advanced virgo , and kagra . .
And you have already written the first three sentences of the full article: short gamma - ray bursts ( sgrbs ) are usually defined by the prompt duration , i.e. , gamma - ray bursts ( grbs ) with @xmath15 @xcite .
a significant fraction of the sgrbs is accompanied by longer duration ( up to @xmath1 ) extended emissions ( ees ) @xcite .
the isotropic energy of the prompt spike is @xmath16 @xcite , while that of ee is @xmath17 @xcite ..
Please generate the next two sentences of the article | interestingly , in some cases , observed fluences of the ees are even larger than those of the prompt spikes , e.g. , @xmath18 for sgrb 050709 @xcite and @xmath19 for sgrb 080503 @xcite .
@xcite found that @xmath20 of _ swift _ bat sgrbs have ees in the x - ray band ( see their table . |
9,413 | Suppose that you have an abstract for a scientific paper: we investigate the quasinormal modes for gravitational perturbations of rotating black holes in four dimensional anti - de sitter ( ads ) spacetime .
the study of the quasinormal frequencies related to these modes is relevant to the ads / cft correspondence .
although results have been obtained for schwarzschild and reissner - nordstrom ads black holes , quasinormal frequencies of kerr - ads black holes are computed for the first time .
we solve the teukolsky equations in ads spacetime , providing a second order and a pade approximation for the angular eigenvalues associated to the teukolsky angular equation .
the transformation theory and the regge - wheeler - zerilli equations for kerr - ads are obtained . .
And you have already written the first three sentences of the full article: the holographic principle in field theory states that , in the presence of gravity , physics in a region of space - time can be encoded on a lower - dimensional surface .
the maldacena @xmath0 conjecture @xcite provides explicit examples for some of these holographic encodings .
for example , iib string theory on the background @xmath1 or @xmath2theory on the background @xmath3 are claimed to be mathematically equivalent ( dual ) to certain quantum field theories on the boundary at infinity of the relevant @xmath4 space ..
Please generate the next two sentences of the article | the isometry groups of the @xmath4 spaces become conformal groups acting on the boundary quantum theories . in the case of @xmath5 ,
the quantum field theory is @xmath6 super yang - mills gauge theory with gauge group @xmath7 and coupling constant @xmath8 . |
9,414 | Suppose that you have an abstract for a scientific paper: on the occasion of the last fifa world cup in brazil , _ the economist _ published a plot depicting how many goals have been scored in all world cup competitions until present , minute by minute .
the plot was followed by a naive and poorly grounded qualitative analysis . in the present article we use _ the economist _ dataset to check its conclusions , update previous results from literature and offer a new model .
in particular , it will be shown that first and second half game have different scoring rates . in the first half
the scoring rate can be considered constant . in the second it increases linearly with time .
* keywords .
* goal , distribution , football , soccer , fifa world cup , outlier , the economist .
And you have already written the first three sentences of the full article: _ the economist _ @xcite is a well known weekly newspaper of economics and economics related subjects .
frequently , it publishes interesting quantitative information in paper and on the web , especially in the _ daily chart _ section . in occasion of the 2014 world cup it collected the amount of goals scored during all the world cup competitions , from 1930 to 2014 , minute by minute .
all the data is presented as interactive plot on the web @xcite ..
Please generate the next two sentences of the article | we give in fig.[fig : economist - reduction ] a reduction of _ the economist _ original graphic . in our plot _ additional time _ ( called _ allowance for time lost _ in fifa documentation @xcite ) and _ extra time _ are not represented .
no distinction is made between _ goals _ , _ penalties _ and _ own goals_. in the original graphic it possible to see in which match each goal was scored and is possible to filter matches according to some categories . |
9,415 | Suppose that you have an abstract for a scientific paper: the mathisson equations under the frenkel - mathisson supplementary condition are studied in a schwarzschild field .
the choice of solutions , which describe the motions of the proper center of mass of a spinning test particle , is discussed , and the calculation procedure for highly relativistic motions is proposed .
the very motions are important for astrophysics while investigating possible effects of the gravitational spin - orbit interaction on the particle s world line and trajectory . .
And you have already written the first three sentences of the full article: 70 years ago myron mathisson has presented the equations describing the motions of a spinning test particle in a gravitational field @xcite
@xmath0 @xmath1 where @xmath2 is the 4-velocity of a spinning particle , @xmath3 is the antisymmetric tensor of spin , @xmath4 and @xmath5 are , respectively , the mass and the covariant derivative with respect to the proper time @xmath6 ; @xmath7 is the riemann curvature tensor of the spacetime .
( throughout this paper we use units @xmath8 ..
Please generate the next two sentences of the article | greek indices run 1 , 2 , 3 , 4 and latin indices 1 , 2 , 3 ; the signature of the metric ( ,,,+ ) is chosen . )
equations ( [ 1 ] ) , ( [ 2 ] ) were supplemented by the condition @xcite @xmath9 ( in special relativity condition ( [ 3 ] ) was introduced by j. frenkel @xcite . ) |
9,416 | Suppose that you have an abstract for a scientific paper: the vertical stratification of the magnetic field strength in sunspot penumbrae is investigated by means of spectropolarimetric observations at high spatial resolution from the hinode spacecraft . assuming that the magnetic field changes linearly with optical depth we find that , in those regions where the magnetic field is more inclined and the evershed flow is strongest ( penumbral intraspines ) , the magnetic field can either increase or decrease with depth . allowing more degrees of freedom to
the magnetic field stratification reveals that the magnetic field initially decreases from @xmath0 until @xmath1 , but increases again below that .
the presence of strong magnetic fields near the continuum is at odds with the existence of regions void of magnetic fields at , or right below , the @xmath2 level in the penumbra .
however , they are compatible with the presence of a horizontal flux - tube - like field embedded in a magnetic atmosphere . *l * .
And you have already written the first three sentences of the full article: it is now widely accepted that the horizontal structure of the sunspot penumbra is composed of two magnetic components ( solanki 2003 ; bellot rubio 2003 ) .
one of them possesses a somewhat inclined ( @xmath3 with respect to the vertical direction to the solar surface ) and strong ( @xmath4 g ) magnetic field , whereas the other is characterized by a weaker and more horizontal one ( lites et al .
1993 ; redi et al ..
Please generate the next two sentences of the article | 1998 ; bellot rubio et al . 2004
; borrero et al . |
9,417 | Suppose that you have an abstract for a scientific paper: observations of relativistic jets from black holes systems suggest that particle acceleration often occurs at fixed locations within the flow .
these sites could be associated with critical points that allow the formation of standing shock regions , such as the magnetosonic modified fast point . using the self - similar formulation of special relativistic magnetohydrodynamics by @xcite
, we derive a new class of flow solutions that are both relativistic and cross the modified fast point at a finite height .
our solutions span a range of lorentz factors up to at least 10 , appropriate for most jets in x - ray binaries and active galactic nuclei , and a range in injected particle internal energy . a broad range of solutions exists , which will allow the eventual matching of these scale - free models to physical boundary conditions in the analysis of observed sources . .
And you have already written the first three sentences of the full article: jets have been observed around a large variety of astrophysical objects , such as young stellar objects ( ysos ) , accreting white dwarfs , x - ray binaries ( xrbs ) , and active galactic nuclei ( agn ) , and are also thought to drive gamma - ray bursts ( grbs ) . in ysos jets facilitate angular momentum transport , allowing the central star to accrete more matter , and likely play a similar role in accreting black hole systems , where in agn they are thought to also affect the evolution of their host galaxy ( e.g. * ? ? ?
while there are enormous differences between the types and scales of objects around which jets can occur , the origins of jets seem to be remarkably similar , requiring the basic ingredients of infalling / collapsing , rotating matter , and magnetic fields . despite these seemingly simple initial conditions , there are currently many outstanding problems in our understanding of jets , from their creation to their matter content and internal physics .
one important facet of jets observationally is their hallmark synchrotron emission dominating the radio bands in particular , extending up to at least the near infrared ( nir ) in xrbs @xcite . at higher frequencies the typical power - law spectral energy distributions ( seds ).
Please generate the next two sentences of the article | are generally interpreted as optically thin synchrotron emission from accelerated particles , both in agn @xcite and in xrbs @xcite .
an effective way to accelerate radiating particles into a power - law distribution is via diffusive shock acceleration ( e.g. * ? ? ? |
9,418 | Suppose that you have an abstract for a scientific paper: this paper is devoted to minimizing the sum of a smooth function and a nonsmooth @xmath0-regularized term .
this problem as a special cases includes the @xmath0-regularized convex minimization problem in signal processing , compressive sensing , machine learning , data mining , etc .
however , the non - differentiability of the @xmath0-norm causes more challenging especially in large problems encountered in many practical applications .
this paper proposes , analyzes , and tests a barzilai - borwein gradient algorithm . at each iteration ,
the generated search direction enjoys descent property and can be easily derived by minimizing a local approximal quadratic model and simultaneously taking the favorable structure of the @xmath0-norm . moreover , a nonmonotone line search technique is incorporated to find a suitable stepsize along this direction .
the algorithm is easily performed , where the values of the objective function and the gradient of the smooth term are required at per - iteration . under some conditions ,
the proposed algorithm is shown to be globally convergent .
the limited experiments by using some nonconvex unconstrained problems from cuter library with additive @xmath0-regularization illustrate that the proposed algorithm performs quite well .
extensive experiments for @xmath0-regularized least squares problems in compressive sensing verify that our algorithm compares favorably with several state - of - the - art algorithms which are specifically designed in recent years .
nonsmooth optimization , nonconvex optimization , barzilai - borwein gradient algorithm , nonmonotone line search , @xmath0 regularization , compressive sensing 65l09 , 65k05 , 90c30 , 90c25 .
And you have already written the first three sentences of the full article: the focus of this paper is on the following structured minimization @xmath1 where @xmath2 is a continuously differentiable ( may be nonconvex ) function that is bounded below ; @xmath3 denotes the @xmath0-norm of a vector ; parameter @xmath4 is used to trade off both terms for minimization . due to its structure , problem ( [ probtype ] ) covers a wide range of apparently related formulations in different scientific fields including linear inverse problem , signal / image processing , compressive sensing , and machine learning .
a popular special case of model ( [ probtype ] ) is the @xmath0-norm regularized least square problem @xmath5 where @xmath6 @xmath7 is a linear operator , and @xmath8 is an observation . model ( [ onenorm ] ) mainly appears in compressive sensing an emerging methodology in digital signal processing , and has attracted intensive research activities over the past years @xcite .
compressive sensing is based on the fact that if the original signal is sparse or approximately sparse in some orthogonal basis , an exact restoration can be produced via solving problem ( [ onenorm ] ) ..
Please generate the next two sentences of the article | another prevalent case of ( [ probtype ] ) that has been achieved much interest in machine learning is the linear and logistic regression . given the training date @xmath9^\top\in\mathbb{r}^{m\times n}$ ] and class labels @xmath10 .
a linear classifier is a hyperplane @xmath11 , where @xmath12 is a set of weights and @xmath13 is the intercept . |
9,419 | Suppose that you have an abstract for a scientific paper: drell - yan dilepton pair production and inclusive direct photon production can be described within a unified framework in the color dipole approach .
the inclusion of non - perturbative primordial transverse momenta and dglap evolution is studied .
we successfully describe data for dilepton spectra from @xmath0-gev @xmath1 collisions , inclusive direct photon spectra for @xmath1 collisions at rhic energies @xmath2 gev , and for @xmath3 collisions at tevatron energies @xmath4 tev , in a formalism that is free from any extra parameters . .
And you have already written the first three sentences of the full article: massive lepton pair production and inclusive direct photon production in hadronic collisions have historically provided an important tool to gain access to parton distributions in hadrons . moreover , direct photons , i.e. photons not from hadronic decay , can be also a powerful probe of the initial state of matter created in heavy ion collisions , since they interact with the medium only electromagnetically and therefore provide a baseline for the interpretation of jet - quenching models . in the parton model ,
the feynman diagrams for partonic subprocesses that are present in drell - yan ( dy ) lepton pair production and in inclusive direct photon production are different , and the connection between both production mechanisms within a unique approximation scheme is not obvious .
since in the target rest frame the dy process looks like bremsstrahlung of a virtual photon decaying into a lepton pair , we will show that the color dipole formalism defined in this frame is well suited to describe both production processes in a unified framework free of parameters . as an illustrative example.
Please generate the next two sentences of the article | , we study dilepton spectra in @xmath0-gev @xmath1 collisions from the e866 experiment @xcite , inclusive direct - photon spectra in @xmath1 at @xmath2 gev from the phenix experiment @xcite , and @xmath3 collisions at @xmath4 tev from the cdf experiment @xcite .
there have been already some attempts to describe the dy transverse momentum distribution in the color dipole approach @xcite , but unfortunately the experimental data that was used for comparison is not fully kinematically in the range of validity of the model . |
9,420 | Suppose that you have an abstract for a scientific paper: we study distributed agreement in synchronous directed dynamic networks , where an omniscient message adversary controls the presence / absence of communication links .
we prove that consensus is impossible under a message adversary that guarantees weak connectivity only , and introduce vertex - stable root components ( vsrcs ) as a means for circumventing this impossibility : a @xmath0 message adversary guarantees that , eventually , there is an interval of @xmath1 consecutive rounds where every communication graph contains at most @xmath2 strongly connected components consisting of the same processes ( with possibly varying interconnect topology ) , which have at most out - going links to the remaining processes .
we present a consensus algorithm that works correctly under a @xmath3 message adversary , where @xmath4 is the dynamic causal network diameter .
our algorithm maintains local estimates of the communication graphs , and applies techniques for detecting network stability and univalent system configurations .
several related impossibility results and lower bounds , in particular , that neither a @xmath5 message adversary nor a @xmath6 one allow to solve consensus , reveal that there is not much hope to deal with ( much ) stronger message adversaries here . however , we show that gracefully degrading consensus , which degrades to general @xmath2-set agreement in case of unfavorable network conditions , allows to cope with stronger message adversaries : we provide a @xmath2-uniform @xmath2-set agreement algorithm , where the number of system - wide decision values @xmath2 is not encoded in the algorithm , but rather determined by the actual power of the message adversary in a run : our algorithm guarantees at most @xmath2 decision values under a @xmath7 message adversary , which combines @xmath8 ( with some small value of @xmath1 , ensuring termination ) with some information flow guarantee @xmath9 between certain vsrcs ( ensuring @xmath2-agreement ) . since related impossibility results....
And you have already written the first three sentences of the full article: [ sec : intro ] dynamic networks , instantiated , e.g. , by wireless sensor networks , mobile ad - hoc networks and vehicle area networks , are becoming ubiquitous nowadays .
the primary properties of such networks are sets of participants ( called processes in the sequel ) that are a priori unknown and potentially changing , time - varying connectivity between processes , and the absence of a central control .
dynamic networks is an important and very active area of research @xcite . accurately modeling dynamic networks is challenging , for several reasons : first , process mobility , process crashes / recoveries , deliberate joins / leaves , and peculiarities in the low - level system design like duty - cycling ( used to save energy in wireless sensor networks ) make static communication topologies , as typically used in classic network models , inadequate for dynamic networks ..
Please generate the next two sentences of the article | certain instances of dynamic networks , in particular , peer - to - peer networks @xcite and inter - vehicle area networks @xcite , even suffer from significant churn , i.e. , a large number of processes that can appear / disappear over time , possibly in the presence of faulty processes @xcite , and hence consist of a potentially unbounded total number of participants over time .
more classic applications like _ mobile ad - hoc networks _ ( manets ) |
9,421 | Suppose that you have an abstract for a scientific paper: we report diffusion monte carlo ( dmc ) calculations on mgo in the rock - salt and cscl structures .
the calculations are based on hartree - fock pseudopotentials , with the single - particle orbitals entering the correlated wave function being represented by a systematically convergeable cubic - spline basis .
systematic tests are presented on system - size errors using periodically repeating cells of up to over 600 atoms .
the equilibrium lattice parameter of the rock - salt structure obtained within dmc is almost identical to the hartree - fock result , which is close to the experimental value . the dmc result for
the bulk modulus is also in good agreement with the experimental value .
the b1-b2 transition pressure ( between the rock - salt and cscl structures ) is predicted to be just below 600 gpa , which is beyond the experimentally accessible range , in accord with other predictions based on hartree - fock and density functional theories . .
And you have already written the first three sentences of the full article: the quantum monte carlo ( qmc ) technique is becoming an increasingly important tool in the study of condensed matter @xcite .
competitive in accuracy with high - level quantum chemistry methods , it has the enormous advantage of being practicable for large systems containing hundreds of atoms .
the power of qmc in overcoming the deficiencies of density functional theory ( dft ) has been amply demonstrated by recent applications , including the energetics of point defects in silicon @xcite and carbon @xcite , the reconstruction of the si ( 001 ) surface @xcite and its interaction with h@xmath0 @xcite , and the calculation of optical excitation energies @xcite ..
Please generate the next two sentences of the article | nevertheless , the classes of materials to which qmc has been applied have so far been rather limited .
oxide materials are likely to be a very fruitful field for the application of qmc , but in exploring this field it is clearly important to study the capabilities of the techniques for the simplest possible oxides . |
9,422 | Suppose that you have an abstract for a scientific paper: we present a new method for calculating arrival distribution of ultra - high energy cosmic rays ( uhecrs ) including modifications by the galactic magnetic field .
we perform numerical simulations of uhe anti - protons , which are injected isotropically at the earth , in the galaxy and record the directions of velocities at the earth and outside the galaxy for all of the trajectories .
we then select some of them so that the resultant mapping of the velocity directions outside the galaxy of the selected trajectories corresponds to a given source location scenario , applying liouville s theorem .
we also consider energy loss processes of uhe protons in the intergalactic space . applying this method to our source location scenario which is adopted in our recent study and
can explain the agasa observation above @xmath0 ev , we calculate the arrival distribution of uhecrs including lower energy ( @xmath1 ) ones .
we find that our source model can reproduce the large - scale isotropy and the small - scale anisotropy on uhecr arrival distribution above @xmath2 ev observed by the agasa .
we also demonstrate the uhecr arrival distribution above @xmath2 ev with the event number expected by future experiments in the next few years .
the interesting feature of the resultant arrival distribution is the arrangement of the clustered events in the order of their energies , reflecting the directions of the galactic magnetic field .
this is also pointed out by @xcite .
this feature will allow us to obtain some kind of information about the composition of uhecrs and the magnetic field with increasing amount of data . .
And you have already written the first three sentences of the full article: there is no statistically significant large scale anisotropy in the observed arrival distribution of ultra - high energy cosmic rays ( uhecrs ) above @xmath2 ev @xcite .
this may imply an extragalactic origin of cosmic rays above @xmath2 ev , combined with the change of spectral slope of the observed energy spectrum at @xmath3 ev @xcite .
another important feature of the uhecr arrival distribution is the small scale clusterings of the arrival directions @xcite ..
Please generate the next two sentences of the article | the current agasa data set of 57 events above 4 @xmath4 ev contains four doublets and one triplet within a separation angle of 2.5@xmath5 .
chance probability to observe such clusters under an isotropic distribution is only about 1 @xmath6 @xcite . on the other hand |
9,423 | Suppose that you have an abstract for a scientific paper: moving target defense ( mtd ) can enhance the resilience of cyber systems against attacks .
although there have been many mtd techniques , there is no systematic understanding and _ quantitative _ characterization of the power of mtd . in this paper
, we propose to use a cyber epidemic dynamics approach to characterize the power of mtd .
we define and investigate two complementary measures that are applicable when the defender aims to deploy mtd to achieve a certain security goal .
one measure emphasizes the _ maximum _ portion of time during which the system can afford to stay in an undesired configuration ( or posture ) , without considering the cost of deploying mtd .
the other measure emphasizes the _ minimum _ cost of deploying mtd , while accommodating that the system has to stay in an undesired configuration ( or posture ) for a given portion of time .
our analytic studies lead to algorithms for optimally deploying mtd . .
And you have already written the first three sentences of the full article: moving target defense ( mtd ) is believed to be a game changer " for cyber defense .
although there have been many studies on specific mtd techniques , the power of mtd is often demonstrated via simulation . rigorously characterizing the power of mtd is an important problem and
is closely related to the well known hard problem of security metrics . in this paper.
Please generate the next two sentences of the article | , we initiate the study of a novel approach for characterizing the power of mtd .
we propose to use the cyber epidemic dynamics approach to characterize the power of _ classes _ of mtd techniques . |
9,424 | Suppose that you have an abstract for a scientific paper: we report the discovery of a highly eccentric , double - lined spectroscopic binary star system ( tyc 3010 - 1494 - 1 ) , comprising two solar - type stars that we had initially identified as a single star with a brown dwarf companion . at the moderate resolving power of the marvels
spectrograph and the spectrographs used for subsequent radial - velocity ( rv ) measurements ( @xmath0 ) , this particular stellar binary mimics a single - lined binary with an rv signal that would be induced by a brown dwarf companion ( @xmath1 ) to a solar - type primary .
at least three properties of this system allow it to masquerade as a single star with a very low - mass companion : its large eccentricity ( @xmath2 ) , its relatively long period ( @xmath3 days ) , and the approximately perpendicular orientation of the semi - major axis with respect to the line of sight ( @xmath4 ) . as a result of these properties , for @xmath595% of the orbit the two sets of stellar spectral lines are completely blended , and the rv measurements based on centroiding on the apparently single - lined spectrum is very well fit by an orbit solution indicative of a brown dwarf companion on a more circular orbit ( @xmath6 ) . only during the @xmath55% of the orbit near periastron passage does the true , double - lined nature and large rv amplitude of @xmath515 km s@xmath7 reveal itself .
the discovery of this binary system is an important lesson for rv surveys searching for substellar companions ; at a given resolution and observing cadence , a survey will be susceptible to these kinds of astrophysical false positives for a range of orbital parameters . finally , for surveys like marvels that lack the resolution for a useful line bisector analysis , it is imperative to monitor the peak of the cross - correlation function for suspicious changes in width or shape , so that such false positives can be flagged during the candidate vetting process . .
And you have already written the first three sentences of the full article: as a part of the third phase of the sloan digital sky survey ( sdss - iii ; * ? ? ?
* ) , the marvels ( _ _ m__ulti - object _ _ a__po _ _ r__adial _ _ v__elocity _ _ e__xoplanet _ _ l__arge - area _ _ s__urvey ) project is searching for substellar companions by monitoring the radial velocities ( rvs ) of 3330 fgk stars @xcite .
this sample size is large enough for the project to find relatively rare objects , such as brown dwarf ( bd ) companions to solar - type stars ..
Please generate the next two sentences of the article | the paucity of observed bd companions to solar - type stars with separations of @xmath85 au is typically referred to as the bd desert @xcite . since the size of the marvels sample allows us to begin to quantify how arid the bd desert may be , any marvels discovery of a bd in the desert ( or lack thereof ) is a step toward increasing our understanding of bd formation .
in addition to its large homogeneous target sample , marvels differs from other surveys for substellar companions in two key ways . |
9,425 | Suppose that you have an abstract for a scientific paper: the lifetime and the sustainability of the wireless sensor networks ( wsns ) can be increased with energy harvesting transmitters utilizing optimum packet scheduling . on the other hand , wsns
are observed to collect spatially or temporally correlated data which should be taken into account for the optimum packet scheduling in an energy harvesting system .
however , the solutions available for 2-user multiple - access channel ( mac ) systems with energy harvesting transmitters do not consider the common data or the correlation among the data . in this paper , optimal packet scheduling for energy harvesting 2-user gaussian mac with common data
is achieved by assuming deterministic knowledge of the data and energy packets , i.e. , offline solution .
the optimum departure region is found by using karush - kuhn - tucker ( kkt ) conditions generalizing the solutions obtained for the mac without common data .
an efficient iterative backward water - filling algorithm is defined .
the optimum solution is numerically compared with the case of no scheduling , uniform power scheduling and the previous solutions defined for the mac without common data by showing the improvement obtained with the optimization .
submitted paper energy harvesting , mac , common data , correlation , packet scheduling . .
And you have already written the first three sentences of the full article: harvesting with optimum packet scheduling policy is significantly important for increasing the lifetime and sustainability of wireless sensor networks ( wsns ) and to achieve the demands of green communications @xcite .
the scarcity and sporadic availability of the energy make it necessary to store it and utilize optimally .
therefore , optimum power management and data transfer schemes are significantly important for wsns ..
Please generate the next two sentences of the article | the correlation of data observed in wsns is one of the most important factors to be taken into account for designing optimum power scheduling algorithms for the energy harvesting transmitters in order to consume the available resources more efficiently @xcite . in this article ,
previous optimal solutions defined for gaussian mac are extended to include common data observed at the energy harvesting transmitters . |
9,426 | Suppose that you have an abstract for a scientific paper: no more salient issue exists in contemporary astrophysics and cosmology than that of the elusive `` dark matter '' . for many years already milgrom s paradigm of modified newtonian dynamics ( mond ) has provided an alternative way to interpret observations without appeal to invisible dark matter .
mond had been successful in elucidating economically the dynamics of disk galaxies of all scales , while doing less well for clusters of galaxies ; in its original form it could not address gravitational lensing or cosmology . after reviewing some of the evidence in favor of mond , i recollect the development of relativistic formulations for it to cope with the last deficiency .
i comment on recent work by various groups in confronting t@xmath0v@xmath0s , a relativistic embodiment of mond , with observational data on gravitational lensing and cosmology . throughout
i ask what sort of physics can be responsible for the efficacy of mond , and conclude with an appraisal of what theoretical developments are still needed to reach a full description of the world involving no unobserved matter . .
And you have already written the first three sentences of the full article: newtonian gravity theory has served physics and technology faithfully for well over three centuries . nevertheless , it has long been known that it is only an approximation to a relativistic gravitation theory , usually identified with einstein s 1915 general relativity ( gr ) .
gr has correctly predicted subtle effects in the dynamics of the solar system , in the celebrated hulse - taylor double pulsar , and has anticipated the existence of those exotic denizens of the universe , black holes , now confirmed by myriad observations of galactic nuclei , compact galactic x - ray sources , etc .
the nonlinear aspects of gravitation in gr are crucial to these new settings : gravitation is more difficult than newton supposed . but up until a few decades ago astronomers took comfort in the belief that if one sidesteps situations with extremely strong gravitational fields , or with extremely rapid motions , then newtonian theory is a good approximation to the truth ..
Please generate the next two sentences of the article | but is that so ?
consider the situation in the realm of galaxies . |
9,427 | Suppose that you have an abstract for a scientific paper: in the framework of dielectric theory the static non - local self - energy of an electron near an ultra - thin polarizable layer has been calculated and applied to study binding energies of image - states near free - standing graphene .
the corresponding series of eigenvalues and eigenfunctions have been obtained by solving numerically the one - dimensional schrdinger equation .
image - potential - state wave functions accumulate most of their probability outside the slab .
we find that a random phase approximation ( rpa ) for the non - local dielectric function yields a superior description for the potential inside the slab , but a simple fermi - thomas theory can be used to get a reasonable quasi - analytical approximation to the full rpa result that can be computed very economically .
binding energies of the image - potential states follow a pattern close to the rydberg series for a perfect metal with the addition of intermediate states due to the added symmetry of the potential .
the formalism only requires a minimal set of free parameters ; the slab width and the electronic density .
the theoretical calculations are compared to experimental results for work function and image - potential states obtained by two - photon photoemission .
new journal of physics * 16 * ( 2014 ) 023012 ; doi : 10.1088/1367 - 2630/16/2/023012 _ keywords _ : graphene , ultra - thin slab , induced potential , self - energy , non - local dielectric response , random phase approximation , fermi - thomas approximation , image - potential states , binding energies , rydberg series , whittaker series , work function . .
And you have already written the first three sentences of the full article: graphene layers display a number of interesting properties and potential applications owing to the linearly - dispersing bands found near the @xmath0 point in the brillouin zone @xcite .
however , in order to get a complete characterization of graphene other regions in the brillouin zone need to be considered .
in particular , unoccupied states in the vicinity of the @xmath1 point can play a significant role in the transport of currents@xcite ..
Please generate the next two sentences of the article | indeed , it is well known the importance of conduction band minima valleys located around @xmath1 in ballistic electron emission processes , where currents are injected on a substrate under voltage - dependent matching restrictions ( e.g. @xmath2-conservation@xcite ) that are relevant to design field emission transistors@xcite . on the other hand ,
the transport of heat also involves other regions of the brillouin zone apart from the @xmath0 point . |
9,428 | Suppose that you have an abstract for a scientific paper: the influence of the low - frequency timing noise on the precision of measurements of the keplerian and post - keplerian orbital parameters in binary pulsars is studied .
fundamental limits on the accuracy of tests of alternative theories of gravity in the strong - field regime are established . the gravitational low - frequency timing noise formed by an ensemble of binary stars
is briefly discussed . .
And you have already written the first three sentences of the full article: the discovery of the first binary pulsar in 1974 by r. hulse and j.h .
taylor had opened fascinating new opportunities for testing alternative theories of gravitation in the radiative and in the strong - gravitational - field regimes outside the boundaries of the solar system . presently , two distinguished binary pulsars - psr b1913 + 16 and psr b1534 + 12 - serve as primary extra - solar astrophysical laboratories for gravitational physisists .
the radiative @xmath0 test of general relativity ( gr ) in the case of psr b1913 + 16 has been performed with a precision about 0.4% ( taylor & weisberg 1989 , damour & taylor 1991 ) ..
Please generate the next two sentences of the article | in addition , the binary pulsars psr b1534 + 12 strong - field @xmath1 test of gr has been done with the precision 1% ( stairs et al .
1998 ) . what is worth noting |
9,429 | Suppose that you have an abstract for a scientific paper: we report on a study of the thermal dust emission of the circumstellar envelopes of a sample of class0 sources .
the physical structure ( geometry , radial intensity profile , spatial temperature and spectral energy distribution ) and properties ( mass , size , bolometric luminosity ( @xmath0 ) and temperature ( @xmath1 ) , and age ) of class0 sources are derived here in an evolutionary context .
this is done by combining scuba imaging at 450 and 850 @xmath2 m of the thermal dust emission of envelopes of class0 sources in the perseus and orion molecular cloud complexes with a model of the envelope , with the implementation of techniques like the blackbody fitting and radiative transfer calculations of dusty envelopes , and with the smith evolutionary model for protostars .
the modelling results obtained here confirm the validity of a simple spherical symmetric model envelope , and the assumptions about density and dust distributions following the standard envelope model .
the spherically model reproduces reasonably well the observed seds and the radial profiles of the sources .
the implications of the derived properties for protostellar evolution are illustrated by analysis of the @xmath0 , the @xmath3 , and the power - law index @xmath4 of the density distribution for a sample of class0 sources . .
And you have already written the first three sentences of the full article: the earliest evolutionary phase of star formation , in which a deeply embedded protostar is known to exist , is the so - called class0 stage ( andr et al .
1993 ) . since protostars in this phase ( class0 sources )
are highly obscured by extended dusty envelopes , they can be observed mainly in the far - infrared to millimetre wavelength range ..
Please generate the next two sentences of the article | specifically , a class0 source consists of a central protostellar object surrounded by an infalling dusty envelope and a flattened accretion disk .
many ( presumably all ) class0 sources are associated with strong molecular flows , usually more energetic than those from class1 sources ( davis & eislffel 1995 ) . |
9,430 | Suppose that you have an abstract for a scientific paper: an extensive program for the calculation of galactic cosmic - ray propagation has been developed .
this is a continuation of the work described in @xcite . the main motivation for developing this code @xcite is the prediction of diffuse galactic gamma rays for comparison with data from the cgro instruments egret , comptel , and osse .
the basic spatial propagation mechanisms are ( momentum - dependent ) diffusion , convection , while in momentum space energy loss and diffusive reacceleration are treated .
primary and secondary nucleons , primary and secondary electrons , and secondary positrons are included .
fragmentation and energy losses are computed using realistic distributions for the interstellar gas and radiation fields . .
And you have already written the first three sentences of the full article: we are developing a model which aims to reproduce self - consistently observational data of many kinds related to cosmic - ray origin and propagation : direct measurements of nuclei , electrons and positrons , gamma rays , and synchrotron radiation .
these data provide many independent constraints on any model and our approach is able to take advantage of this since it must be consistent with all types of observation .
we emphasize also the use of realistic astrophysical input ( e.g. , for the gas distribution ) as well as theoretical developments ( e.g. , reacceleration ) ..
Please generate the next two sentences of the article | the code is sufficiently general that new physical effects can be introduced as required .
the basic procedure is first to obtain a set of propagation parameters which reproduce the cosmic ray b / c ratio , and the spectrum of secondary positrons ; the same propagation conditions are then applied to primary electrons . |
9,431 | Suppose that you have an abstract for a scientific paper: we apply the non - linear diffusive shock acceleration theory in order to describe the properties of two supernova remnants , sn 1572 ( tycho ) and sn 1604 ( kepler ) . by analyzing the multi - wavelength spectra
, we infer that both tycho s and kepler s forward shocks ( fs ) are accelerating protons up to @xmath0 tev , channeling into cosmic rays more than 10 per cent of their kinetic energy .
we find that the streaming instability induced by cosmic rays is consistent with the x - ray morphology of the remnants , indicating a very efficient magnetic field amplification ( up to @xmath1 g ) . in the case of tycho
we explain the @xmath2-ray spectrum from the gev up to the tev band as due to pion decay produced in nuclear collisions by accelerated nuclei scattering against the background gas . on the other hand , due to the larger distance
, the @xmath2-ray emission from kepler is not detected , being below the sensitivity of the present detectors , but it should be detectable by cta .
address = inaf - osservatorio astrofisico di arcetri , l.go e. fermi 5 , i - 50125 firenze , italia address = department of astrophysical sciences , princeton university , princeton , nj 08544 , usa .
And you have already written the first three sentences of the full article: modelling particle acceleration at snrs is one of the main goal to explain the origin of galactic cosmic rays ( crs ) in the context of the so - called _ supernova paradigm _ ( see e.g. * ? ? ?
this paradigm requires that snrs are able to accelerate nuclei up to energies as high as a few times @xmath3 gev , converting a fraction @xmath4 of the snr kinetic energy into crs .
there is an increasing amount of evidence that shocks in young snrs can indeed reach the required efficiency ..
Please generate the next two sentences of the article | unfortunately , all these evidence are indirect and when considered individually can be also explained by other mechanisms that do not require efficient acceleration .
a clear example of such an ambiguous situation is represented by @xmath2-ray emission . in the last few years |
9,432 | Suppose that you have an abstract for a scientific paper: we derive kramers formula as singular limit of the fokker - planck equation with double - well potential . the convergence proof is based on the rayleigh principle of the underlying wasserstein gradient structure and complements a recent result by peletier , savar and veneroni . + kramers formula , fokker - planck equation , wasserstein gradient flow , + rayleigh principle * 35q84 , 49s05 , 80a30 . * .
And you have already written the first three sentences of the full article: in 1940 kramers derived chemical reaction rates from certain limits in a fokker - planck equation that describes the probability density of a brownian particle in an energy landscape @xcite .
the limit of high activation energy has been revisited in a recent paper by peletier et al @xcite , where a spatially inhomogeneous extension of kramers formula is rigorously derived for unimolecular reactions between two chemical states @xmath0 and @xmath1 .
their derivation relies on passing to the limit in the @xmath2-gradient flow structure of the fokker - planck equation ..
Please generate the next two sentences of the article | it is well - known by now that the fokker - planck equation has also an interpretation as a wasserstein gradient flow @xcite and the question was raised in @xcite whether kramers formula can also be derived and interpreted within this wasserstein gradient flow structure .
this concept has also been investigated on a formal level for more complicated reaction - diffusion systems in @xcite . a further motivation for studying the fokker - planck equation within the wasserstein framework comes from applications that additionally prescribe the time evolution of a moment @xcite . |
9,433 | Suppose that you have an abstract for a scientific paper: in the framework of coulomb gauge qcd we explore dynamical breaking of chiral symmetry and screening of the confinement potential at finite density .
the screened potential is applied in study of charmonium dissociation . .
And you have already written the first three sentences of the full article: since the recent discovery of the strongly correlated qcd fluid , the phenomenology of quark - gluon plasma ( qgp ) has attracted a lot of attention @xcite .
many predictions have been made for the several possible phases of the qgp in which quarks and gluons are no longer confined to nucleons and pions @xcite . at extremely high temperature and low density , thermal excitations of the gluon field
are expected to screen interactions between color charges and ultimately , due to asymptotic freedom result in a weakly interacting quark gas @xcite . similarly , at low temperature but high density debye screening.
Please generate the next two sentences of the article | is expected to reduce the range of strong interactions .
novel phases that correlate quark color and flavor are predicted to occur at asymptotic densities due to the attractive nature of quark - quark interactions in certain color - flavor locked combinations @xcite . |
9,434 | Suppose that you have an abstract for a scientific paper: we derive simple difference formulas describing a small - signal absorption of thz field in a semiconductor superlattice driven by a microwave pump .
we give a transparent geometric interpretation of these formulas that allows a search of optimum conditions for the gain employing only a simple qualitative analysis .
our theoretical approach provides a powerful tool for finding the correspondence between quasistatic and dynamic regimes in ac - driven semiconductor superlattices . .
And you have already written the first three sentences of the full article: semiconductor superlattices ( ssl ) have attracted growing attention in view of their unique electronic properties , which can be used for generation , amplification and detection of a high - frequency electromagnetic radiation @xcite .
nonlinear transport properties of ssl allows a generation of thz radiation in conditions of negative differential conductance ( ndc ) @xcite .
however , the static ndc makes ssl unstable against formation of high - field electric domains @xcite ..
Please generate the next two sentences of the article | these electric domains are believed to be destructive for the thz gain in ssls .
currently the main focus is on the possibilities to overcome this drawback within the scheme of dc - biased ssl @xcite . |
9,435 | Suppose that you have an abstract for a scientific paper: we use multi - component decaying dark matter ( dm ) scenario to explain the possible cosmic ray excesses in the positron fraction recently confirmed by ams-02 and the total @xmath0 flux observed by fermi - lat . in the two - component dm models
, we find an interesting variation of the flavor structure along with the cutoff of the heavy dm .
for the three - component dm case , we focus on a particular parameter range in which the best fits prefer to open only 2 dm decay channels with a third dm contributing nothing to the electron and positron spectra .
we show that all models give the reasonable fits to both the ams-02 positron fraction and the fermi - lat total @xmath1 flux , which are also consistent with the measured diffuse @xmath2-ray flux by fermi - lat . .
And you have already written the first three sentences of the full article: despite an overwhelming evidence for the existence of dark matter ( dm ) in our universe @xcite , its real nature is still a great mystery as it has been only seen through gravitational interactions . from the particle physics point of view
, it is generally expected that dm is composed of some stable particles or the ones with the lifetime much longer than the age of the universe .
since these particles are distributed in our galaxy and the universe , it is widely believed that their annihilations and decays would give rise to the visible signals in terms of light stable particles , such as positrons / electrons , ( anti)protons , photons and neutrinos , which can be observed on the earth . as a result.
Please generate the next two sentences of the article | , such an indirect search for dm @xcite is regarded as one of the most promising ways to detect dm .
recently , there has been a great advance in the dm indirect detections . |
9,436 | Suppose that you have an abstract for a scientific paper: we have determined the magnetic phase diagram of the quasi - one - dimensional @xmath0 1 heisenberg antiferromagnet ni(c@xmath1h@xmath2n@xmath3)@xmath3n@xmath4(pf@xmath5 ) by specific heat measurements to 150 mk in temperature and 32 t in the magnetic field . when the field is applied along the spin - chain direction
, a new phase appears at @xmath6 t. for the previously known phases of field - induced order , an accurate determination is made of the power - law exponents of the ordering temperature near the zero - temperature critical field @xmath7 , owing to the four - fold improvement of the minimum temperature over the previous work .
the results are compared with the predictions based on the bose - einstein condensation of triplet excitations . substituting deuterium for hydrogen
is found to slightly reduce the interchain exchange . .
And you have already written the first three sentences of the full article: one - dimensional ( 1d ) integer - spin heisenberg antiferromagnets ( haf ) are well - known for the haldane energy gap @xcite between the singlet spin - liquid ground state and the lowest excited state , which is an @xmath8 triplet .
the application of a magnetic field leads to zeeman splitting of the triplet and eventual vanishing of the gap @xmath9 at @xmath10 , where the energy of the lowest branch of the split triplet reaches the ground - state level . at this critical field ,
the expected quantum transition is to the tomonaga - luttinger spin liquid , @xcite in which spin correlations decay with characteristic power laws ..
Please generate the next two sentences of the article | this scenario remains robust in an array of 1d integer - spin haf chains against the introduction of interchain exchange .
such a coupling reduces @xmath7 but , provided it is small , does not destroy the singlet ground state below @xmath7 . above @xmath7 , it leads to finite - temperature long - range order ( lro ) , which can be described as the three - dimensional bose - einstein condensation of the lower - branch triplets . |
9,437 | Suppose that you have an abstract for a scientific paper: a self - consistent system of interacting nonlinear spinor and scalar fields within the scope of a bianchi type - i cosmological model filled with perfect fluid is considered .
exact self - consistent solutions to the corresponding field equations are obtained .
the role of spinor field in the evolution of the universe is studied .
it is shown that the spinor field gives rise to an accelerated mode of expansion of the universe . at the early stage of evolution the spinor field nonlinearity
generates the acceleration while at the later stage it is done by the nonzero spinor mass . .
And you have already written the first three sentences of the full article: the accelerated mode of expansion of the present day universe encourages many researchers to introduce different kind of sources that is able to explain this . among them
most popular is the dark energy given by a @xmath0 term @xcite , quintessence @xcite , chaplygin gas @xcite .
recently cosmological models with spinor field have been extensively studied by a number of authors in a series of papers @xcite ..
Please generate the next two sentences of the article | the principal motive of the papers @xcite was to find out the regular solutions of the corresponding field equations . in some special cases ,
namely with a cosmological constant ( @xmath0 term ) that plays the role of an additional gravitation field , we indeed find singularity - free solutions . |
9,438 | Suppose that you have an abstract for a scientific paper: we combine several numerical and semi - analytical methods to study the @xmath0 double perovskites and which were recently proposed to exhibit excitonic magnetism . starting from the density functional theory and constrained random phase approximation we construct effective multi - band hubbard models .
these are analyzed by means of static and dynamical mean - field theories and strong coupling expansion .
we find both materials to be insulators , but , contrary to the experimental claims , with a large spin gap of several hundreds mev preventing formation of an ordered state at low temperature . .
And you have already written the first three sentences of the full article: the discovery of new spin - orbit related phenomena and states of matter lead to an immense increase of interest in materials containing @xmath0 elements , ir and os in particular .
@xcite among the new effects , @xcite recently proposed a possibility of excitonic condensation in @xmath1 materials with cubic local symmetry .
the singlet atomic ground state promises no interesting low - energy physics ..
Please generate the next two sentences of the article | however , if the energy of the lowest excitation , a magnetic moment carrying triplet , is sufficiently small , the inter - atomic exchange due to electron hopping may lead to formation of an ordered state - excitonic magnet .
thanks to the singlet - triplet exchange processes , the excitations can be viewed as mobile quasi - particles propagating on the singlet background with a non - trivial dispersion . |
9,439 | Suppose that you have an abstract for a scientific paper: we investigate the competition between the superconducting and the excitonic phases on dirac electrons on a bipartite planar lattice .
the conditions for the appearance of superconductivity or excitonic condensate are given by the minima of the free energy and our results are explained .
address = departamento de cincias naturais , universidade federal de so joo del rei , 36301 - 000 so joo del rei , mg , brazil address = departamento de cincias naturais , universidade federal de so joo del rei , 36301 - 000 so joo del rei , mg , brazil address = instituto de fsica , universidade federal do rio de janeiro , caixa postal 68528 , rio de janeiro , rj , 21941 - 972 , brazil .
And you have already written the first three sentences of the full article: several condensed matter systems have been discovered in recent years whose active electrons have their kinematics governed by the dirac equation @xcite , rather than by the schrdinger equation .
their dispersion relation , accordingly , has the same form as that of a relativistic particle .
the reason for this unusual behavior of electrons whose speed is at least two orders of magnitude less than the speed of light can be ascribed to a particular influence of the lattice background on the electronic properties . for many technological applications.
Please generate the next two sentences of the article | , it would be interesting if those systems were a semiconductor , instead of a semimetal .
therefore , the possibility of an insulator state or the appearance of an excitonic gap due to short range electronic interactions in a system of massless dirac fermions has been the object of intense investigation @xcite . |
9,440 | Suppose that you have an abstract for a scientific paper: in two previous papers a semi - analytical model was presented for the hierarchical clustering of halos via gravitational instability from peaks in a random gaussian field of density fluctuations .
this model is better founded than the extended press - schechter model , which is known to agree with numerical simulations and to make similar predictions . the specific merger rate , however , shows a significant departure at intermediate captured masses .
the origin of this was suspected as being the rather crude approximation used for the density of nested peaks . here , we seek to verify this suspicion by implementing a more accurate expression for the latter quantity which accounts for the correlation among peaks .
we confirm that the inclusion of the peak - peak correlation improves the specific merger rate , while the good behavior of the remaining quantities is preserved .
# 1*#1 * .
And you have already written the first three sentences of the full article: today it is widely accepted that the formation of cosmic relaxed objects proceeds via gravitational instability from small to large scales .
this clustering process can be studied in detail , following accurately the dynamics of collapse by means of n - body simulations , and statistically , by approximate semi - analytical models which enable a swifter and more efficient exploration of the parameter space .
the most complete semi - analytical models developed to date are those by lacey & cole ( 1993 , 1994 , hereafter lc93 and lc94 ) , and by manrique & salvador - sol ( 1995 , 1996 , papers i and ii ) ..
Please generate the next two sentences of the article | all the quantities in both models are derived from the statistics of the filtered random gaussian density field , @xmath0/\langle\rho\rangle$ ] , of cold matter encountered at an arbitrary initial epoch , @xmath1 , after recombination when fluctuations are still linear .
similarly , in each model the dynamics of dissipationless collapse is approximated by the simple spherical model . |
9,441 | Suppose that you have an abstract for a scientific paper: we study the evolution of globular clusters with mass spectra under the influence of the steady galactic tidal field , including the effects of velocity anisotropy . similar to single - mass models , velocity anisotropy develops as the cluster evolves , but the degree of anisotropy is much smaller than isolated clusters . except for very early epochs of the cluster evolution ,
nearly all mass components become tangentially anisotropic at the outer parts .
we have compared our results with multi - mass , king - michie models . the isotropic king model better fits to the fokker - planck results because of tangential anisotropy . however , it is almost impossible to fit the computed density profiles to the multi - mass king models for all mass components
. thus if one attempts to derive global mass function based on the observed mass function in limited radial range using multi - mass king models , one may get somewhat erratic results , especially for low mass stars .
we have examined how the mass function changes in time . specifically , we find that the power - law index of the mass function decreases monotonically with the total mass of the cluster .
this appears to be consistent with the behaviour of the observed slopes of mass functions for a limited number of clusters , although it is premature to compare quantitatively because there are other mechanisms in contributing the evaporation of stars from the clusters .
the projected velocity profiles for anisotropic models with the apocenter criterion for evaporation show significant flattening toward the tidal radius compared to isotropic model or anisotropic model with the energy criterion .
such a behaviour of velocity profile appears to be consistent with the observed profiles of collapsed cluster m15 . #
1to 0pt#1 # 1to 0pt#1 [ firstpage ] celestial mechanics , stellar dynamics
globular clusters : general .
And you have already written the first three sentences of the full article: the study of evolution of globular clusters has a long history
. it would be most desirable to use direct @xmath0-body calculations in order to follow the evolution of realistic globular clusters realistically , but we do not have enough computing power to do that for @xmath0 comparable to the number of stars in real globular clusters at this moment .
therefore we have to rely on approximate techniques to understand the dynamics of star clusters ..
Please generate the next two sentences of the article | the fokker - planck equation has been widely used for the study of globular clusters , but it requires many simplifying assumptions .
the assumption of velocity isotropy is usually employed because it allows fast and accurate integration of the fokker - planck equation ( cohn 1980 ) . however , high degree of velocity anisotropy is known to be generated by two - body relaxation in the outer parts of isolated clusters ( e.g. , spitzer 1987 ) . |
9,442 | Suppose that you have an abstract for a scientific paper: recent data from the cdf collaboration on the production of spin - triplet bottomonium states at the tevatron @xmath0 collider are analyzed within the nrqcd factorization formalism .
the color - singlet matrix elements are determined from electromagnetic decays and from potential models .
the color - octet matrix elements are determined by fitting the cdf data on the cross sections for @xmath1 , @xmath2 , and @xmath3 at large @xmath4 and the fractions of @xmath1 coming from @xmath5 and @xmath6 .
we use the resulting matrix elements to predict the cross sections at the tevatron for the spin - singlet states @xmath7 and @xmath8 .
we argue that @xmath9 should be observable in run ii through the decay @xmath10 . .
And you have already written the first three sentences of the full article: the nrqcd factorization formalism provides a systematic framework for analyzing the inclusive production of heavy quarkonium @xcite .
long - distance effects involving the binding of a heavy quark - antiquark pair into quarkonium are factored into parameters called nrqcd matrix elements .
these nonperturbative parameters are universal , so values extracted from one high energy physics experiment can be used to predict the production rate in others ..
Please generate the next two sentences of the article | the nrqcd matrix elements scale as definite powers of @xmath11 , where @xmath11 is the typical relative velocity of the heavy quark .
the nrqcd factorization approach becomes phenomenologically useful upon truncating the expansion in @xmath11 so as to reduce the independent nrqcd matrix elements to a manageable number . |
9,443 | Suppose that you have an abstract for a scientific paper: inspired by the string axiverse idea , it has been suggested that the recent transition from decelerated to accelerated cosmic expansion is driven by an axion - like quintessence field with a sub - planckian decay constant .
the scenario requires that the axion field be rather near the maximum of its potential , but is less finely tuned than other explanations of cosmic acceleration .
the model is parametrized by an axion decay constant @xmath0 , the axion mass @xmath1 , and an initial misalignment angle @xmath2 which is close to @xmath3 . in order to determine the @xmath1 and @xmath4 values consistent with observations ,
these parameters are mapped onto observables : the hubble parameter @xmath5 at an angular diameter distance @xmath6 to redshift @xmath7 , as well as the angular sound horizon of the cosmic microwave background ( cmb ) .
measurements of the baryon acoustic oscillation ( bao ) scale at @xmath8 by the boss survey and planck measurements of cmb temperature anisotropies are then used to probe the @xmath9 parameter space . with current data ,
cmb constraints are the most powerful , allowing a fraction of only @xmath10 of the parameter - space volume .
measurements of the bao scale made using the spherex or ska experiments could go further , observationally distinguishing all but @xmath11 or @xmath12 of the parameter - space volume ( allowed by simple priors ) from the @xmath13cdm model . .
And you have already written the first three sentences of the full article: the cause of the accelerated cosmic expansion @xcite remains elusive .
one possibility is quintessence , in which the acceleration is driven by the potential energy of a scalar field displaced from the minimum of its potential .
the idea that late - time acceleration could be connected to a new fundamental scalar was suggested in refs ..
Please generate the next two sentences of the article | @xcite ( see ref .
@xcite for a comprehensive review ) and developed into viable models in refs . |
9,444 | Suppose that you have an abstract for a scientific paper: we will consider two special families of polynomial perturbations of the linear center .
for the resulting perturbed systems , which are generalized linard systems , we provide the exact upper bound for the number of limit cycles that bifurcate from the periodic orbits of the linear center .
limit cycle , linard system , periodic orbit .
And you have already written the first three sentences of the full article: the bifurcation of limit cycles by perturbing a planar system which has a continuous family of _ cycles _ , i.e. periodic orbits , has been an intensively studied phenomenon ; see for instance @xcite and references therein .
the simplest planar system having a continuous family of cycles is the linear center , and a special family of its perturbations is given by the generalized polynomial linard systems : @xmath0 where @xmath1 , @xmath2 , @xmath3 , @xmath4 and @xmath5 are polynomials for @xmath6 , and @xmath7 is a small parameter .
the classical and generalized linard systems appear very often in several branches of science and engineering , as biology , chemistry , mechanics , electronics , etc ..
Please generate the next two sentences of the article | see for instance @xcite and references therein .
in particular linard systems are frequent specially in physiological processes , see for instance @xcite . |
9,445 | Suppose that you have an abstract for a scientific paper: we develop a new method for simultaneous timing and spectral studies of gamma ray burst ( grb ) prompt emission and apply it to make a pulse - wise description of the prompt emission of grb 090618 , the brightest grb detected in the fermi era .
we exploit the large area ( and sensitivity ) of _ swift_/bat and the wide band width of _ fermi_/gbm to derive the parameters for a complete spectral and timing description of the individual pulses of this grb , based on the various empirical relations suggested in the literature .
we demonstrate that this empirical model correctly describes the other observed properties of the burst like the variation of the lag with energy and the pulse width with energy .
the measurements also show an indication of an _ increase _ in pulse width as a function of energy at low energies for some of the pulses , which is naturally explained as an off - shoot of some particular combination of the model parameters .
we argue that these model parameters , particularly the peak energy at the beginning of the pulse , are the natural choices to be used for correlation with luminosity .
the implications of these results for the use of grbs as standard candles are briefly described . .
And you have already written the first three sentences of the full article: the phenomenon of gamma ray burst ( grb ) has raised many unresolved issues .
for example , the nature of the compact object in the progenitor responsible for the jet emission is not yet understood .
the widely accepted scenario for the grb emission , supported by strong observational evidences ( van paradijs et al ..
Please generate the next two sentences of the article | 2000 ) , is that of a catastrophic energy release from a highly massive , rapidly rotating , low metallicity star towards the end of its life .
this catastrophic process for the long grb class ( t@xmath0 @xmath1 2 s , where t@xmath0 is the time taken by the burst to accumulate between 5% to 95% of its prompt emission |
9,446 | Suppose that you have an abstract for a scientific paper: quantum lithography proposes to adopt entangled quantum states in order to increase resolution in interferometry . in the present paper
we experimentally demonstrate that the output of a high - gain optical parametric amplifier can be intense yet exhibits quantum features , namely , sub - rayleigh fringes , as proposed by agarwal et al .
( phys .
rev .
lett . * 86 * , 1389 ( 2001 ) ) .
we investigate multiphoton states generated by a high - gain optical parametric amplifier operating with a quantum vacuum input for a gain values up to 2.5 .
the visibility has then been increased by means of three - photon absorption .
the present article opens interesting perspectives for the implementation of such an advanced interferometrical setup .
pacs : 03.67.-a , 03.67.hk , 42.65.lm .
And you have already written the first three sentences of the full article: since the early days of quantum electronics , non - linear optics has played a basic role both for its relevance as a fundamental chapter of modern science and for its technological applications @xcite .
nonlinear parametric processes , due to the peculiar correlation properties of the generated photons , have been adopted to investigate the quantum properties of electromagnetic fields . in the last few years
it has been proposed to exploit entangled quantum states in order to increase the resolution in quantum interferometry , specifically , for quantum lithography @xcite and to achieve heisenberg limited resolution @xcite . in such framework , particular attention has been devoted to the generation of noon states , path entangled states of the form @xmath0 , of fundamental relevance since a single - photon phase shift @xmath1 induces a relative shift between the two components equal to @xmath2 ..
Please generate the next two sentences of the article | this feature can be exploited to enhance phase resolution in interferometric measurements , leading to a sub - rayleigh resolution scaling as @xmath3 ; @xmath4 being the wavelength of the field @xcite .
the generation of photonic noon states has been the subject of intense theoretical research @xcite , but up to now the actual experimental implementation has been limited to a posteriori generation of two , three and four photons states @xcite and to the conditional generation of a noon state with @xmath5 @xcite . |
9,447 | Suppose that you have an abstract for a scientific paper: the cross section of neutron - deuteron radiative capture @xmath0 is calculated at energies relevant to big - bang nucleosynthesis ( @xmath1 kev ) with pionless effective field theory . at these energies ,
magnetic transition m1 gives the dominant contribution .
the m1 amplitude is calculated up to next - to - next - to leading order(n@xmath2lo ) with insertion of three - body force .
results are in good agreement within few percent theoretical uncertainty in comparison with available calculated data below e=200 kev . * h. sadeghi * and * s. bayegan * + _ department of physics , university of tehran , p.o.box 14395 - 547 , tehran , iran . _ + 1.0 cm 26.35.+c , 21.30.fe , 25.40.lw , 11.80.jy , 27.10.+h [ cols= " > , < " , ] at lo and nlo , this is the only three - body force entering , but at n@xmath2lo , where we saw that @xmath3 is required , it is determined by the triton binding energy @xmath4 .
we solve integral equation by expansion in order of @xmath5 and properly iterating the kernel .
then , the resulted @xmath6 will be folded to electromagnetic interaction order by order and properly integrated on the involving momentum . in kev .
the short dashed , long dashed and solid line correspond to the error up to lo , nlo and n@xmath2lo , respectively . ] for our calculation source of error due to low cutoffs and low momentums for very low energy calculation is neglected .
the cutoff variation decreases steadily as we increase the order of the calculation and is of the order of @xmath7 , where @xmath8 is the order of the calculation .
we used @xmath9 mev , for the smallest cutoff .
the cross section calculation for neutron radiative capture by deuteron as function of the center - of - mass energy at lo , nlo and n@xmath2lo is shown in fig . [ crosssection ] .
table 1 shows numerical results for the eft @xmath10 cross section for various nucleon center of mass energies e up to n@xmath2lo and errors estimate at every order in comparison with the last column....
And you have already written the first three sentences of the full article: we have calculated the cross section of radiative capture process @xmath10 .
we applied pionless eft to find numerical results for the m1 contributions for this capture process for incident neutron energies relevant for bbn , @xmath12 mev . at these energy our calculation is dominated by s - wave state and magnetic transition m1 contribution .
the error estimate in the cross section in comparison with evaluated nuclear data file endf @xcite is shown in fig ..
Please generate the next two sentences of the article | [ error ] and table 1 .
errors estimate are 20 - 30 percent at leading order , below 10 percent up to nlo and by insertion of three - body force at n@xmath2lo , this error is reduced to below 1@xmath13 percent . |
9,448 | Suppose that you have an abstract for a scientific paper: searches for gravitational wave signals which do not have a precise model describing the shape of their waveforms are often performed using power detectors based on a quadratic form of the data .
a new , optimal method of generalizing these power detectors so that they operate coherently over a network of interferometers is presented .
such a mode of operation is useful in obtaining better detection efficiencies , and better estimates of the position of the source of the gravitational wave signal .
numerical simulations based on a realistic , computationally efficient hierarchical implementation of the method are used to characterize its efficiency , for detection and for position estimation .
the method is shown to be more efficient at detecting signals than an incoherent approach based on coincidences between lists of events .
it is also shown to be capable of locating the position of the source . .
And you have already written the first three sentences of the full article: six kilometer - scale laser interferometers designed to observe gravitational waves ( gw ) with unprecedented sensitivities should complete or approach the end of their commissioning in the year 2003 .
three are operated in north america by the ligo laboratory @xcite , two in europe by the virgo @xcite and the geo600 @xcite projects , on one in asia by the tama300 @xcite project .
a collaborative analysis of the data collected by these instruments provides the best prospects for detecting and analyzing gw events of astronomical origin ..
Please generate the next two sentences of the article | the focus of this article will be on `` bursts '' of gravitational radiation , loosely defined as gw of duration of the order of a few seconds at most , and present in a frequency range overlapping at least partially with the bandwidth of the interferometers ( 10 hz @xmath0 1 khz ) .
other types of signals that will not be discussed here include continuous gw from rotating neutron stars , and a stochastic background of gw of cosmological origin . |
9,449 | Suppose that you have an abstract for a scientific paper: the second - largest eigenvalue and second - smallest laplacian eigenvalue of a graph are measures of the graph s connectivity .
these parameters can be used to analyze the robustness , resilience , and synchronizability of networks , and are related to other connectivity attributes such as the vertex- and edge - connectivity , isoperimetric number , and characteristic path length . in this paper
, we give upper bounds for the second - largest eigenvalues of regular graphs and multigraphs which guarantee a desired vertex- or edge - connectivity .
the given bounds are in terms of the order and degree of the graphs , and hold with equality for infinite families of graphs .
second - largest eigenvalue ; vertex - connectivity ; edge - connectivity ; regular multigraph ; algebraic connectivity .
+ 05c50 , 05c40 . .
And you have already written the first three sentences of the full article: determining how well a particular graph is connected is a problem that arises often in various applications .
for example , as defined in @xcite , _ resilience _ is the ability of a network to provide and maintain an acceptable level of service in the face of various faults and challenges to normal operation .
examples of such networks include telecommunication networks , electrical grids , and commodity supply networks ..
Please generate the next two sentences of the article | one of the scientific disciplines that forms the basis of resilience is _ disruption tolerance _ the ability of a system to tolerate disruptions in connectivity among its components ; such disruptions could consist of environmental challenges such as weak and episodic channel connectivity , mobility , and unpredictably - long delay , as well as tolerance of energy challenges @xcite . the most common way to interpret such networks is as connected graphs , where the resilience of a network as a function of its disruption tolerance can be studied by analyzing the connectivity properties of the associated graph .
graph connectivity has also been shown to play an important role in data security ; see @xcite and the references therein for more information . in 1973 , fiedler related the vertex - connectivity of a graph to the second - smallest eigenvalue of its laplacian matrix in the following way ( see section [ preliminaries ] for relevant definitions ) : [ thm1.1 ] @xcite if @xmath0 is a simple , non - complete graph , then @xmath1 . |
9,450 | Suppose that you have an abstract for a scientific paper: we combine two complete , x - ray flux - limited surveys , the _ rosat _ bright survey ( rbs ) and the _ rosat _ north ecliptic pole ( nep ) survey , to measure the space density ( @xmath0 ) and x - ray luminosity function ( @xmath1 ) of non - magnetic cvs .
the combined survey has a flux limit of @xmath2 over most of its solid angle of just over @xmath3 , but is as deep as @xmath4 over a small area .
the cv sample that we construct from these two surveys contains 20 non - magnetic systems .
we carefully include all sources of statistical error in calculating @xmath0 and @xmath1 by using monte carlo simulations ; the most important uncertainty proves to be the often large errors in distances estimates .
if we assume that the 20 cvs in the combined rbs and nep survey sample are representative of the intrinsic population , the space density of non - magnetic cvs is @xmath5 .
we discuss the difficulty in measuring @xmath1 in some detail in order to account for biases in the measurement , we have to adopt a functional form for @xmath1 . assuming that the x - ray luminosity function of non - magnetic cvs is a truncated power law , we constrain the power law index to @xmath6 .
it seems likely that the two surveys have failed to detect a large , faint population of short - period cvs , and that the true space density may well be a factor of 2 or 3 larger than what we have measured ; this is possible , even if we only allow for undetected cvs to have x - ray luminosities in the narrow range @xmath7 .
however , @xmath0 as high as @xmath8 would require that the majority of cvs has x - ray luminosities below @xmath9 in the 0.52.0 kev band .
[ firstpage ] binaries stars : dwarf novae novae , cataclysmic variables x - rays : binaries methods : observational , statistical . .
And you have already written the first three sentences of the full article: cataclysmic variables ( cvs ) are interacting binary stars consisting of white dwarfs accreting from low - mass , roche lobe filling companions ( see @xcite for a review ) .
angular momentum is continuously lost from the binary orbit , driving mass transfer , as well as evolution in orbital period ( @xmath10 ) .
there are still many uncertainties in the theoretical description of cv formation and evolution ( e.g. @xcite ; @xcite ; @xcite ; @xcite ) , as well as several serious discrepancies between the predictions of theory and the properties of the observed cv population ( e.g. @xcite ; @xcite ; @xcite ; pretorius & knigge 2008a , b ; @xcite ; @xcite ) . in order to constrain evolution models , more and better observational constraints on the properties of the galactic cv population are needed ..
Please generate the next two sentences of the article | a fundamental parameter predicted by cv evolution theory , that is expected to be more easily measured than most properties of the intrinsic cv population , is the space density , @xmath0 . the luminosity function ( @xmath1 )
is a closely related property ; although more challenging to constrain than @xmath0 , @xmath1 contains information on the mass transfer rate ( @xmath11 ) distribution of cvs and is therefore potentially much more valuable than the space density alone . |
9,451 | Suppose that you have an abstract for a scientific paper: there are many proposed prediction methods for solar cycles behavior . in a previous paper
we updated the full - shape curve prediction of the current solar cycle 24 using a non - linear dynamics method and we compared the results with the predictions collected by the noaa / sec prediction panel , using observed data up to october 2010 .
the aim of the present paper is to give a quantitative evaluation , a posteriori , of the performances of these prediction methods using a specific global error , updated on a monthly basis , which is a measure of the global performance on the predicted shape ( both amplitude and phase ) of the solar cycle .
we suggest also the use of a percent cycle similarity degree , to better evaluate the predicted shape of the solar cycle curve . .
And you have already written the first three sentences of the full article: solar cycle full - shape prediction methods aim to determine the approximate whole cycle curve , not only its peak magnitude and timing .
this task is particularly useful for numerous scientific and technological applications .
the main involved areas are the electric power transmission systems , airline and satellite communications , gps signals , and extra - vehicular - activities of astronauts during space missions and , more in general , all the solar - terrestrial interactions ..
Please generate the next two sentences of the article | numerous techniques for time series forecasting are developed to accurately predict phase and amplitude of future solar cycles , but with limited success .
depending on the nature of the prediction methods we can distinguish five principal classes : 1 ) curve fitting ; 2 ) precursor ; 3 ) spectral ; 4 ) neural networks ; 5 ) climatology . |
9,452 | Suppose that you have an abstract for a scientific paper: we show that the recently introduced 0 - 1 test can successfully distinguish between strange nonchaotic attractors(snas ) and periodic / quasiperiodic / chaotic attractors , by suitably choosing the arbitrary parameter associated with the translation variables in terms of the golden mean number which avoids resonance with the quasiperiodic force .
we further characterize the transition from quasiperiodic to chaotic motion via snas in terms of the 0 - 1 test .
we demonstrate that the test helps to detect different dynamical transitions to snas from quasiperiodic attractor or the transitions from snas to chaos .
we illustrate the performance of the 0 - 1 test in detecting transitions to snas in quasiperiodically forced logistic map , cubic map , and duffing oscillator .
* a strange nonchaotic attractor(sna ) is considered as a complicated structure in phase space .
such a complex structure is a typical property usually associated with a chaotic attractor .
however , snas are nonchaotic in a dynamical sense because they do not exhibit sensitive dependence on initial conditions ( as evidenced by negative lyapunov exponents )
. these attractors are ubiquitous in different quasiperiodically driven nonlinear systems . while the existence of snas has been firmly established , a question of intense interest is how do these attractors morphologically differ from other attractors and how they can be characterized and quantified . two specific characterizations , namely finite time lyapunov exponents and recurrence plots were proposed earlier in the literature .
however , in the present work we show that the recently introduced measure of 0 - 1 test clearly distinguishes quasiperiodic motion , snas and chaotic attractors and also allows one to detect different dynamical transitions from quasiperiodic motion to snas and snas to chaotic attractors . * .
And you have already written the first three sentences of the full article: a central problem in the study of deterministic dynamical systems is to identify different types of asymptotic behavior of a given system and to understand how the behavior changes as the system parameter changes @xcite .
the asymptotic behavior can be , for instance , a periodic oscillation , a quasiperiodic motion , a sna , or a random or a chaotic motion @xcite .
there has been considerable work in the past addressing how dynamical systems develop chaos from periodic or quasiperiodic motions and how they can be characterized by various diagnostic tools such as lyapunov exponents , fractal dimemsion and recurrence analysis ..
Please generate the next two sentences of the article | some among these like the lyapunov exponents and fractal dimension also require substantial amounts of data , free of noise , in order to perform well .
recently , a much simpler test for the presence of deterministic chaos was proposed by gottwald and melbourne @xcite . |
9,453 | Suppose that you have an abstract for a scientific paper: we demonstrate that the peculiar line profiles observed in da white dwarfs in the temperature range of the zz ceti variables can be explained by the surface velocity fields associated with the pulsations . .
And you have already written the first three sentences of the full article: during the spectroscopic search for rotation in white dwarfs we noticed that all known zz ceti stars showed peculiar h@xmath0 line profiles ( koester et al .
the lines could be fitted using a rotationally broadened profile , but the derived rotation rates were incompatible with other data , e.g. from asteroseismology . using the caii k line for such a study , berger et al .
( 2005 ) found rotation velocities varying from 11 - 28 km / s from seven high - resolution keck and vlt spectra of the variable g29 - 38 a clear indication that the broadening could not be due to rotation ..
Please generate the next two sentences of the article | while the spectra of almost all stars could be fitted with zero rotation , for g29 - 38 this was not true .
the observed spectra ( fig . |
9,454 | Suppose that you have an abstract for a scientific paper: we present a measurement of the hadronic invariant mass squared ( @xmath0 ) spectrum in charmed semileptonic @xmath1 meson decays @xmath2 based on 140 fb@xmath3 of belle data collected near the @xmath4 resonance .
we determine the first , the second central and the second non - central moments of this spectrum for lepton energy thresholds ranging between 0.7 and 1.9 gev .
full correlations between these measurements are evaluated . .
And you have already written the first three sentences of the full article: inclusive semileptonic decays of @xmath1 mesons to charmed final states provide an avenue for measuring the cabibbo - kobayashi - maskawa ( ckm ) matrix element @xmath5 @xcite and for determining non - perturbative hadronic properties of the @xmath1 meson . in particular ,
the moments of the hadronic mass in @xmath6 decays calculated in the framework of the operator product expansion ( ope ) and the heavy quark effective theory ( hqet ) @xcite depend on the @xmath7-quark mass ( @xmath8 ) and a few non - perturbative matrix elements that also appear in the expression of the total semileptonic width .
thus , measurements of the hadronic invariant mass moments @xcite allow the determination of these non - perturbative parameters from the data and reduce the theoretical uncertainty in the extraction of @xmath5 from measurements of the semileptonic branching fraction ..
Please generate the next two sentences of the article | an improved knowledge of @xmath8 also results in a more precise determination of @xmath9 from inclusive charmless semileptonic @xmath1 decays .
this analysis uses @xmath10 events in which the hadronic decay of one @xmath1 meson is fully reconstructed . |
9,455 | Suppose that you have an abstract for a scientific paper: the sample @xmath0-median is a robust estimator of the central tendency or location of an interval - valued random variable .
while the interval - valued sample mean can be highly influenced by outliers , this spatial - type interval - valued median remains much more reliable . in this paper , we show that under general conditions the sample @xmath0-median is a strongly consistent estimator of the @xmath0-median of an interval - valued random variable . .
And you have already written the first three sentences of the full article: in this data driven area , the amount and complexity of the available data grows at an almost incredible speed .
therefore , there is a high need to develop novel tools to cope with such complex data structures .
whereas the first statistical techniques were designed only to manage either quantitative or qualitative data , we can now find statistical procedures to handle functional data ( see for instance arribas - gil and mller @xcite ; febrero - bande and gonzlez - manteiga @xcite ; jacques and preda @xcite ) , fuzzy - valued data ( see , for instance , ferraro and giordani @xcite ; gonzlez - rodrguez _ et al . _.
Please generate the next two sentences of the article | @xcite ; coppi _ et al . _
@xcite ) ; incomplete / missing data ( see , for instance , bianco _ et al . _ |
9,456 | Suppose that you have an abstract for a scientific paper: in the present work we consider a boundary value problem with gluing conditions of integral form for parabolic - hyperbolic type equation . we prove that the considered problem has the volterra property .
the main tools used in the work are related to the method of the integral equations and functional analysis .
[ 1995/12/01 ] .
And you have already written the first three sentences of the full article: the theory of mixed type equations is one the principal parts of the general theory of partial differential equations .
the interest for these kinds of equations arises intensively because of both theoretical and practical of their applications .
many mathematical models of applied problems require investigations of this type of equations ..
Please generate the next two sentences of the article | the actuality of the consideration of mixed type equations has been mentioned , for the first time , by s. a. chaplygin in 1902 in his famous work `` on gas streams '' @xcite .
the first fundamental results in this direction was obtained in 1920 - 1930 by f. tricomi @xcite and s. gellerstedt @xcite . |
9,457 | Suppose that you have an abstract for a scientific paper: an unknown quantum state can not be copied on demand and broadcast freely due to the famous no - cloning theorem .
approximate cloning schemes have been proposed to achieve the optimal cloning characterized by the maximal fidelity between the original and its copies . here , from the perspective of quantum fisher information ( qfi ) , we investigate the distribution of qfi in asymmetric cloning machines which produce two nonidentical copies . as one might expect , improving the qfi of one copy results in decreasing the qfi of the other copy , roughly the same as that of fidelity .
it is perhaps also unsurprising that asymmetric phase - covariant cloning machine outperforms universal cloning machine in distributing qfi since a priori information of the input state has been utilized .
however , interesting results appear when we compare the distributabilities of fidelity ( which quantifies the full information of quantum states ) , and qfi ( which only captures the information of relevant parameters ) in asymmetric cloning machines .
in contrast to the results of fidelity , where the distributability of symmetric cloning is always optimal for any @xmath0-dimensional cloning , we find that asymmetric cloning performs always better than symmetric cloning on the distribution of qfi for @xmath1 , but this conclusion becomes invalid when @xmath2 .
classical information can be replicated perfectly and broadcast without fundamental limitations .
however , information encoded in quantum states is subject to several intrinsic restrictions of quantum mechanics , such as heisenberg s uncertainty relations^@xcite^ and quantum no - cloning theorem^@xcite^. the no - cloning theorem tells us that an unknown quantum state can not be perfectly replicated because of the linearity of the time evolution in quantum physics , which is the essential prerequisite for the absolute security of quantum cryptography^@xcite^. nevertheless , it is still possible to clone a quantum state approximately , or instead , clone it....
And you have already written the first three sentences of the full article: * quantum fisher information . *
we start with a brief introduction of qfi and give a useful form of qfi for a special kind of mixed qudit states , which usually represents the output states of qudit cloning .
recall that qfi of parameter @xmath3 encoded in @xmath0-dimensional quantum state @xmath4 is generally defined as^@xcite^ @xmath5 where @xmath6 is the so - called symmetric logarithmic derivative , which is defined by @xmath7 with @xmath8 . by diagonalizing the matrix as @xmath9.
Please generate the next two sentences of the article | , one can rewritten the qfi as^@xcite^ @xmath10 where @xmath11 is the qfi for pure state @xmath12 with the form @xmath13.\ ] ] note that eq .
( [ e2 ] ) suggests the qfi of a non - full - rank state is only determined by the subset of @xmath14 with nonzero eigenvalues . |
9,458 | Suppose that you have an abstract for a scientific paper: consider a coaction @xmath0 of a locally compact group @xmath1 on a @xmath2-algebra @xmath3 , and a closed normal subgroup @xmath4 of @xmath1 .
we prove , following results of echterhoff for abelian @xmath1 , that mansfield s imprimitivity between @xmath5 and @xmath6 implements equivalences between mansfield induction of representations from @xmath7 to @xmath8 and restriction of representations from @xmath9 to @xmath8 , and between restriction of representations from @xmath8 to @xmath7 and green induction of representations from @xmath8 to @xmath9 .
this allows us to deduce properties of mansfield induction from the known theory of ordinary crossed products . .
And you have already written the first three sentences of the full article: in applications of duality theory for crossed products one often has to know how common constructions such as induction and restriction of representations behave under duality .
thus , after piecemeal results by several authors , echterhoff was led to prove that , for systems involving abelian groups , induction and restriction are dual to one another @xcite .
he later used these results to great effect in his analysis of crossed products with continuous trace @xcite . to state echterhoff s theorem precisely , we fix an action @xmath10 of a locally compact abelian group @xmath1 on a @xmath2-algebra @xmath3 , and a closed subgroup @xmath4 of @xmath1 ..
Please generate the next two sentences of the article | green s imprimitivity theorem gives an imprimitivity bimodule @xmath11 implementing a morita equivalence between @xmath12 and the imprimitivity algebra @xmath13 ; the latter algebra is naturally isomorphic to the crossed product @xmath14 by the dual action @xmath15 of the subgroup @xmath16 of @xmath17 .
let @xmath18 denote the map on equivalence classes of representations given by induction of representations in the sense of green : if @xmath19 is a representation of @xmath12 on @xmath20 , then @xmath21 is by definition the natural left action on ( a completion of ) @xmath22 . |
9,459 | Suppose that you have an abstract for a scientific paper: we have investigated the @xmath0 reaction theoretically for the formation of the @xmath1 mesic nucleus .
we have reported the numerical results in this article . .
And you have already written the first three sentences of the full article: the mesic nuclear bound states have been considered to be interesting systems and studied both theoretically and experimentally @xcite .
so far , one - nucleon transfer reactions have been mainly considered and successfully used to produce the nuclear bound states of meson which is lighter than nucleon in the recoilless kinematics @xcite .
recently , ikeno _ et al ..
Please generate the next two sentences of the article | studied the two nucleon pick - up reaction on the @xmath2 target for the formation of heavy meson bound states with the @xmath3 particle @xcite .
we develop this study in this article and improve the theoretical method in the following four points ; + ( i ) the distortion effects of the projectile and ejectile are taken into account , + ( ii ) the elementary cross section is evaluated phenomenologically and the absolute value of the formation cross section is reported , + ( iii ) the realistic @xmath3 density distribution is used to calculate the meson-@xmath3 bound states @xcite , + ( iv ) the recoil effects of the formation reaction are considered . + we show some of the numerical results here . _ |
9,460 | Suppose that you have an abstract for a scientific paper: we consider a system interacting with a chaotic thermodynamic bath .
we derive an explicit and exact kraus operator sum representation ( osr ) for the open system reduced density .
the osr preserves the hermiticity , complete positivity and norm .
we show that it is useful as a numerical tool by testing it against exact results for a qubit interacting with an isolated flawed quantum computer .
we also discuss some interesting qualitative aspects of the osr . , kraus decomposition , decoherence , coherent shift , chaotic baths 03.65.@xmath0w , 05.30.@xmath0d , 03.67.lx , 03.65.yz , 05.45.mt .
And you have already written the first three sentences of the full article: efforts to design scalable quantum computers ( qcs ) @xcite and other new quantum technologies @xcite are rekindling interest in the phenomenology of open quantum system dynamics .
while effects of atom - radiation field interactions @xcite have been extensively studied , the consequences of interaction with a complex environment are just beginning to be explored .
solid and condensed phase environments bequeath a diversity of controllable interactions for scalable implementation of new quantum technologies , and thus understanding the open system dynamics induced by such complex environments is of particular interest ..
Please generate the next two sentences of the article | recent studies have reported a number of interesting effects such as suppression of decoherence with increasing bath chaos @xcite and large coherent shifting @xcite .
manifestation of chaos @xcite , or at least non - integrability , is a defining and unavoidable feature of complex environments . |
9,461 | Suppose that you have an abstract for a scientific paper: we present an estimate of the partial width of @xmath0 into @xmath1 under the assumption that it is a weakly - bound hadronic molecule whose constituents are a superposition of the charm mesons @xmath2 and @xmath3 . the @xmath1 partial width of @xmath4 is therefore related to the cross section for @xmath5 near the threshold . that cross section at an energy well above the threshold is estimated by scaling the measured cross section for @xmath6 .
it is extrapolated to the @xmath2 threshold by taking into account the threshold resonance in the @xmath7 channel .
the resulting prediction for the @xmath1 partial width of @xmath0 is proportional to the square root of its binding energy . for the current central value of the binding energy ,
the estimated partial width into @xmath1 is comparable to that of the p - wave charmonium state @xmath8 . .
And you have already written the first three sentences of the full article: since the surprising discovery of the @xmath0 in 2003 @xcite , there has been a steadily growing list of new @xmath9 mesons discovered at the @xmath10 factories @xcite .
these discoveries have revealed that the spectrum of @xmath9 mesons is richer than the charmonium states predicted by quark potential models .
the candidates for some of the new @xmath9 mesons include charm meson molecules , tetraquark states , and charmonium hybrid states @xcite ..
Please generate the next two sentences of the article | an ideal experiment for studying some of the new @xmath9 mesons would be @xmath1 collisions at resonance .
the effectiveness of resonant @xmath1 collisions for studying conventional charmonium states was demonstrated by the e760 and e835 experiments at fermilab @xcite . |
9,462 | Suppose that you have an abstract for a scientific paper: we show that the presence of a temporal electromagnetic field on cosmological scales generates an effective cosmological constant which can account for the accelerated expansion of the universe .
primordial electromagnetic quantum fluctuations produced during electroweak scale inflation could naturally explain the presence of this field and also the measured value of the dark energy density .
the behavior of the electromagnetic field on cosmological scales is found to differ from the well studied short - distance behavior and , in fact , the presence of a non - vanishing cosmological constant could be signalling the breakdown of gauge invariance on cosmological scales .
the theory is compatible with all the local gravity tests , and is free from classical or quantum instabilities .
thus we see that , not only the true nature of dark energy can be established without resorting to new physics , but also the value of the cosmological constant finds a natural explanation in the context of standard inflationary cosmology .
this mechanism could be discriminated from a true cosmological constant by upcoming observations of cmb anisotropies and large scale structure . .
And you have already written the first three sentences of the full article: the nature of dark energy , which is believed to be responsible for the present phase of accelerated expansion of the universe @xcite , still remains unknown . despite its phenomenological success ,
the simplest description in terms of a cosmological constant ( @xmath0cdm model ) suffers from an important naturalness problem , since the measured value of @xmath0 , corresponding to @xmath1 ev)@xmath2 , finds no natural explanation in the context of known physics .
moreover , the fact that today matter and dark energy have comparable contributions to the energy density , turns out to be difficult to understand if dark energy is a true cosmological constant ..
Please generate the next two sentences of the article | thus , the energy density of a cosmological constant remains constant throughout the history of the universe , whereas those of the rest of components ( matter or radiation ) grow as we go back in time .
then the question arises as to whether it is a _ coincidence _ ( or not ) that they have comparable values today when they have differed by many orders of magnitude in the past . |
9,463 | Suppose that you have an abstract for a scientific paper: a method is proposed for combining multi - frequency maps in order to produce a catalogue of extragalactic point sources using data from future high - precision satellite experiments .
we have found the optimal way for combining maps at different frequencies in order to maximize the signal ( point sources ) to noise ( rest of the signal ) ratio . our approach is a natural multi - frequency generalization of the band - pass filter introduced by tegmark and de oliveira - costa ( 1998 ) .
we show that combination of different frequency maps gives us the possibility of creating a more complete catalogue of point sources . .
And you have already written the first three sentences of the full article: in the next few years , the new generation of cmb experiments ( map and planck ) will provide all - sky maps of the cosmic microwave background ( cmb ) with high resolutions and sensitivities .
theoretical investigations of different kinds of foregrounds , instrumental noise properties , scan strategies and related topics for the future planck mission are now in progress .
the planck lfi and hfi instruments will be able to measure the cmb anisotropy and polarization using 10 frequency channels that cover the frequency range 30 - 857 ghz ( mandolesi et al.,1998 ; maino et al.,1999 ) ..
Please generate the next two sentences of the article | the maps provided by planck will contain contributions from various physical components , including the primary and secondary cmb signals and foregrounds such as free - free and synchrotron emission , the sunyaev - zeldovich effect , galactic dust and extragalactic point sources .
one of the important goals of this experiment , apart from the separation of the cmb from the remaining parts of the signal , is the creation of a point source catalogue . |
9,464 | Suppose that you have an abstract for a scientific paper: we present the results of irs low - resolution spectroscopy of 51 seyfert galaxies , part of a large _ spitzer _ observing program to determine the mid - to - far infrared spectral energy distributions of a well - defined sample of 87 nearby , 12 -selected seyferts .
we find that the spectra clearly divide into groups based on their continuum shapes and spectral features .
the infrared spectral types appear to be related to the seyfert types .
some features are clearly related to a starburst contribution to the ir spectrum , while the observed power - law continuum shapes , attributed to the agn , may be dust or non - thermal emission .
principal component analysis results suggest that the relative contribution of starburst emission is the dominant cause of variance in the spectra .
we find that the sy 2 s show on average stronger starburst contributions than the sy 1 s . .
And you have already written the first three sentences of the full article: understanding the inner workings of active galactic nuclei ( agns ) is important for understanding the role of supermassive black holes in galaxy evolution .
the mid - to - far infrared ( mfir ) is a key wavelength regime for testing the agn unified scheme and probing the nature of the nuclear obscuring medium .
the _ spitzer space telescope _ allows studies to be made at higher sensitivity and spatial resolution that previous ir missions ..
Please generate the next two sentences of the article | we are conducting a large observing program with all three _ spitzer _ instruments to determine the mfir spectral energy distributions ( seds ) of 87 seyfert galaxies ( pi : j. gallimore , pid : 3269 ) . the sample of seyfert galaxies used for this study comprises all seyfert galaxies from the extended 12 sample of @xcite that have @xmath0 kms@xmath1 . here
we discuss the 51 objects in the sample for which the low - resolution , 5 35 irs spectra are currently available . |
9,465 | Suppose that you have an abstract for a scientific paper: this paper provides a study and discussion of earlier as well as novel more efficient schemes for the precise evaluation of finite - temperature response functions of strongly correlated quantum systems in the framework of the time - dependent density matrix renormalization group ( tdmrg ) .
the computational costs and bond dimensions as functions of time and temperature are examined for the example of the spin-@xmath0 xxz heisenberg chain in the critical xy phase and the gapped nel phase .
the matrix product state purifications occurring in the algorithms are in one - to - one relation with corresponding matrix product operators .
this notational simplification elucidates implications of quasi - locality on the computational costs . based on the observation that there is considerable freedom in designing efficient tdmrg schemes for the calculation of dynamical correlators at finite temperatures , a new class of optimizable schemes , as recently suggested in arxiv:1212.3570 ,
is explained and analyzed numerically . a specific novel near - optimal scheme that requires no additional optimization reaches maximum times that are typically increased by a factor of two , when compared against earlier approaches .
these increased reachable times make many more physical applications accessible . for each of the described tdmrg schemes
, one can devise a corresponding transfer matrix renormalization group ( tmrg ) variant . 0.4 .
And you have already written the first three sentences of the full article: this paper addresses the efficient evaluation of finite - temperature response functions @xmath1 for quantum many - particle systems on one - dimensional ( 1d ) lattices in the framework of the _ density matrix renormalization group _ ( dmrg ) @xcite . from the theoretical perspective
, such quantities occur for example in the context of linear response theory @xcite and characterize the effect of a perturbation @xmath2 of the system at time zero on the expectation value of an observable @xmath3 at time @xmath4 .
initially , the system is in thermal equilibrium , where @xmath5 is the inverse temperature and @xmath6 ..
Please generate the next two sentences of the article | the units are chosen such that boltzmann s and planck s constants are @xmath7 and @xmath8 .
such response functions contain important information on the many - body physics and are addressed in many experimental setups . |
9,466 | Suppose that you have an abstract for a scientific paper: the pion - baryon triangle diagram is inspected for the special kinematic region in which the squared momentum transfer is close to @xmath0 .
the pion propagators can have very small energies , as opposed to @xmath1 in the physical region , which allows the nucleon propagator to be near its mass shell .
this observation leads us to conclude that in this particular domain the triangle diagram is augmented by @xmath2 compared with the standard counting of chiral perturbation theory , hence an infrared enhancement in the single - baryon sector . .
And you have already written the first three sentences of the full article: as far as one - baryon processes are concerned , baryons have always been approximated as static objects at leading order in heavy - baryon chiral perturbation theory ( hbchpt ) , and recoil corrections are treated as subleading perturbations @xcite .
however , the phenomenological successes of covariant approaches , in which recoil corrections are in effect resummed to all orders , challenged this point of view @xcite .
the initial theoretical rationale for covariant treatment of baryons comes from ref ..
Please generate the next two sentences of the article | @xcite ( also touched upon in refs .
@xcite ) , in which the pion - baryon triangle diagram was examined . figure [ fig_trangle ] shows the said diagram , where @xmath3 is the incoming 4-momentum of the baryon and @xmath4 the momentum transfer . with different vertexes |
9,467 | Suppose that you have an abstract for a scientific paper: chaotic properties of symmetrical two - dimensional stadium - like billiards with elliptical arcs are studied numerically and analytically . for the two - parameter truncated elliptical billiard the existence and linear stability of several lowest - order periodic orbits are investigated in the full parameter space .
poincar ' e plots are computed and used for evaluation of the degree of chaoticity with the box - counting method .
the limit of the fully chaotic behavior is identified with circular arcs . above this limit , for flattened elliptical arcs , mixed dynamics with numerous stable elliptic islands
is present , similarly as in the elliptical stadium billiards . below this limit
the full chaos extends over the whole region of elongated shapes and the existing orbits are either unstable or neutral .
this is conspicuously different from the behavior in the elliptical stadium billiards , where the chaotic region is strictly bounded from both sides . to examine the mechanism of this difference , a generalization to a novel three - parameter family of boundary shapes
is proposed and suggested for further evaluation . .
And you have already written the first three sentences of the full article: two - dimensional planar billiards are nonlinear systems with rich and interesting dynamical properties .
a point particle , moving with constant velocity within a closed boundary and exhibiting specular reflections on the walls , can have regular , mixed or fully chaotic dynamics , in strong dependence on details of the boundary shape . in physics ,
two - dimensional billiards offer good examples of coexistence of regular , mixed and chaotic dynamics in hamiltonian systems ..
Please generate the next two sentences of the article | this type of behavior , illustrated by the standard map and explained by means of the kam - theorem , is present in many realistic phenomena , such as planetary systems and various types of coupled oscillators@xcite .
chaotic billiards were first introduced by sinai@xcite who considered the defocusing effects of circular scatterers in the two - dimensional lorentz gas . |
9,468 | Suppose that you have an abstract for a scientific paper: the _ capacitated vehicle routing problem _ ( cvrp ) @xcite involves distributing ( identical ) items from a depot to a set of demand locations , using a single capacitated vehicle .
we study a generalization of this problem to the setting of multiple vehicles having non - uniform speeds ( that we call _ heterogenous cvrp _ ) , and present a constant - factor approximation algorithm .
the technical heart of our result lies in achieving a constant approximation to the following tsp variant ( called _ heterogenous tsp _ ) .
given a metric denoting distances between vertices , a depot @xmath0 containing @xmath1 vehicles having respective speeds @xmath2 , the goal is to find a tour for each vehicle ( starting and ending at @xmath0 ) , so that every vertex is covered in some tour and the maximum completion time is minimized .
this problem is precisely heterogenous cvrp when vehicles are uncapacitated .
the presence of non - uniform speeds introduces difficulties for employing standard tour - splitting techniques . in order to get a better understanding of this technique in our context
, we appeal to ideas from the 2-approximation for scheduling in parallel machine of lenstra et al .
@xcite .
this motivates the introduction of a new approximate mst construction called _ level - prim _ , which is related to _
light approximate shortest - path trees _ @xcite .
the last component of our algorithm involves partitioning the level - prim tree and matching the resulting parts to vehicles .
this decomposition is more subtle than usual since now we need to enforce correlation between the size of the parts and their distances to the depot . .
And you have already written the first three sentences of the full article: the capacitated vehicle routing problem ( @xmath3 ) is an extensively studied combinatorial optimization problem ( see e.g. , the book @xcite and references therein ) . @xmath3is defined on a metric space @xmath4 , where @xmath5 is a finite set of locations / vertices and @xmath6 a distance function that is symmetric and satisfies triangle inequality .
there is a depot vertex @xmath7 that contains an infinite supply of an identical item , and each vertex @xmath8 demands some units @xmath9 of this item .
a single vehicle of capacity @xmath10 is used to distribute the items ..
Please generate the next two sentences of the article | the objective is to find a minimum length tour of the vehicle that satisfies all demands subject to the constraint that the vehicle carries at most @xmath11 units at any time .
@xmath3is closely related to the traveling salesman problem ( @xmath12 ) . |
9,469 | Suppose that you have an abstract for a scientific paper: we study the influence of the symmetry energy of the equation of state on the thermal evolution of protoneutron stars and the properties of supernova neutrinos by the numerical simulations after the protoneutron stars are formed .
as for the equation of state ( eos ) of nuclear matter , we take two eos s with different symmetry energies obtained by the relativistic mean field theory .
we find the symmetry energy plays the essential role on the evolution of lepton profiles and the neutrino fluxes .
@referee = 1.0 in .
And you have already written the first three sentences of the full article: the recent advance in radioactive nuclear beam experiments provides us with novel information on unstable nuclei far away from the stability line ( tanihata et al . 1985 ) .
the symmetry energy becomes more essential to understand the nuclear structure as we go further away from stability .
the symmetry energy is also important to provide the equation of state ( eos ) for neutron stars and supernovae ..
Please generate the next two sentences of the article | the properties of dense matter under neutron rich environment determine the structure and chemical composition of stars and may change their evolution drastically .
therefore , it is very interesting to study the influence of the symmetry energy on astrophysical problems . |
9,470 | Suppose that you have an abstract for a scientific paper: we discuss the relationship between the fractional quantum hall effect in the vicinity of the thin - torus , a.k.a .
tao - thouless ( tt ) , limit and quantum spin chains .
we argue that the energetics of fractional quantum hall states in jain sequence at filling fraction @xmath0 ( and @xmath1 ) in the lowest landau level is captured by @xmath2 spin chains with @xmath3 spins in the unit cell .
these spin chains naturally arise at sub - leading order in @xmath4 which serves as an expansion parameter away from the tt limit ( @xmath5 ) .
we also corroborate earlier results on the smooth fermi surface deformation of the gapless state at @xmath6 , interpolating between a state described by a critical @xmath7 chain and the bulk . .
And you have already written the first three sentences of the full article: ultra cold electrons in two dimensions in a strong perpendicular magnetic field , the quantum hall ( qh ) system @xcite , exhibits a fascinating phase diagram including phases with fractionalized excitations and topological order @xcite . ever since its discovery three decades ago , the qh system has inspired a huge amount of experimental and theoretical effort , not least due to its richness in phenomenology and mathematical structure .
new developments include the observation of the fractional quantum hall effect in graphene @xcite and ideas of applications in the context of topological quantum computing @xcite .
moreover , it has been realized that the theoretical description of a system of rapidly rotating bosons is formally very similar to that of an electron gas in a magnetic field @xcite ..
Please generate the next two sentences of the article | a key property of fractional quantum hall ( fqh ) states is their topological order @xcite .
one consequence thereof is that their physical properties are insensitive to smooth deformations of the manifold on which we choose to study them . |
9,471 | Suppose that you have an abstract for a scientific paper: we have used composite spectra generated from more than 22000 qsos observed in the course of the 2df and 6df qso redshift surveys to investigate the relationship between the velocity width of emission lines and qso luminosity .
we find that the velocity width of the broad emission lines , , , and are correlated with the continuum luminosity , with a significance of more than 99 per cent .
of the major narrow emission lines ( 5007 , 3727 , 3870 and 3426 ) only exhibits a significant correlation between line width and luminosity . assuming
that the gas is moving in keplerian orbits and that the radius of the broad line region is related to the qso continuum luminosity , we use the velocity widths of the broad lines to derive average black hole masses for the qsos contributing to the composite spectra .
the resultant qso mass - luminosity relationship is consistent with @xmath0 .
we find that the correlation between line width and redshift , if present , must be weak , and only shows significant evidence of evolution .
this enables us to constrain the redshift evolution of the black hole mass - luminosity ratio to be @xmath1 with @xmath2 , much less than the @xmath3 evolution seen in qso luminosity evolution . assuming that the motion of the broad line region gas is keplerian and that its radius depends on the qso luminosity , our models indicate that the observed weak redshift dependence is too small for the observed qso luminosity function to be due to the evolution of a single long - lived population of sources . = = = = = = = = # 1 # 1 # 1 # 1 @mathgroup@group @mathgroup@normal@groupeurmn @mathgroup@bold@groupeurbn @mathgroup@group
@mathgroup@normal@groupmsamn @mathgroup@bold@groupmsamn = `` 019 = ' ' 016 = `` 040 = ' ' 336 = " 33e = = = = = = = = # 1 # 1 # 1 # 1 = = = = = = = = galaxies : active quasars : general quasars : emission lines galaxies : stellar content .
And you have already written the first three sentences of the full article: the vast energy budget required by active galactic nuclei ( agn ) is probably provided by the accretion of matter onto a supermassive black hole ( bh ) . evidence that such objects can be found in agn is provided by the keplerian motions of the mega - masers observed in some sources ( e.g. miyoshi et al .
1995 ) , the broad fek@xmath4 emission line observed in the x - ray spectrum of some sources ( e.g. mcg-6 - 30 - 15 ; see tanaka et al .
1995 ; wilms et al ..
Please generate the next two sentences of the article | 2001 ) and the reverberation mapping experiments ( e.g. blanford & mckee 1982 ; netzer & peterson 1997 ; wandel , peterson & malkan 1999 ; kaspi et al .
2000 , hereafter k00 ; peterson et al . |
9,472 | Suppose that you have an abstract for a scientific paper: in the atomic force microscope , the nanoscale force topography of even complex surface superstructures is extracted by the changing vibration frequency of a scanning tip . an alternative dissipation topography with similar or even better
contrast has been demonstrated recently by mapping the @xmath0-dependent tip _ damping _ : but the detailed damping mechanism is still unknown . here
we identify two different tip dissipation mechanisms : local mechanical softness , and hysteresis .
motivated by recent data , we describe both of them in a one - dimensional model of moir superstructures of incommensurate overlayers .
local softness at `` soliton '' defects yields a dissipation contrast that can be much larger than the corresponding density or corrugation contrast . at realistically low vibration frequencies ,
however , a much stronger and more effective dissipation is caused by the tip - induced nonlinear jumping of the soliton , naturally developing bi - stability and hysteresis .
signatures of this mechanism are proposed for experimental identification . .
And you have already written the first three sentences of the full article: the tip - based scanning force microscopes of the atomic force microscope ( afm ) family constitute perhaps the single most important tool bag in nanotechnology .
the substrate topography is extracted from a map of the oscillation frequency of a tip , hovering a short distance above the surface . besides the frequency shift however , the tip also develops a damping , reflecting a position dependent mechanical dissipation .
et al . _.
Please generate the next two sentences of the article | @xcite showed recently that afm dissipation whose general occurrence has been widely discussed by several groups a decade ago @xcite but whose potential importance was still underestimated is able to map exquisitely delicate features such as the moir superstructure pattern formed by misfit dislocations ( `` solitons '' ) of incommensurate kbr adsorbate islands ( fig .
[ model : fig]a ) on nacl(100 ) . |
9,473 | Suppose that you have an abstract for a scientific paper: this proceedings contribution summarizes first results obtained from a systematic study of 2011 nls1 galaxies , as presented in zhou et al .
( 2006 , apjs 166 , 128 ) .
the sample was compiled by examining the spectral parameters of galaxies and qsos derived from sdss dr3 data .
we discuss some preliminary results on the statistic properties of the sample , such as the fraction of nls1 , the properties of broad and narrow emission lines , and emission in other wavebands .
the black hole mass velocity dispersion relation for nls1s was re - examined using the velocity dispersion values estimated from the stellar absorption spectra of the host galaxies .
preliminary result from an x - ray study for a small subset using data obtained by xmm - newton is briefly discussed . .
And you have already written the first three sentences of the full article: narrow line seyfert 1 galaxies ( nls1s ) are a special type of active galactic nuclei ( agn ) whose optical spectra are similar to seyfert1 type , but with much narrower balmer line width ; they also show weak [ oiii ] lines and strong feii emission in optical and uv ( osterbrock & pogge 1985 ) .
the importance of nls1s lies in that their properties are at the extremity among seyfert1 family , including steep soft x - ray spectra ( @xmath0 ) and rapid x - ray variability , strong blue wings of emission lines ( e.g. boroson & green 1992 ; laor et al . 1994 ; wang 1996 , boller et al .
1996 , grupe et al . 1999 , 2001 , xu , et al ..
Please generate the next two sentences of the article | observational data show that nls1 tend to have small black hole masses and the high eddington ratios @xmath1 ( e.g. boroson 2002 ) .
in fact , they were found to locate at one extreme end of eigenvector1 of the correlation matrix ( boroson & green 1992 , sulentic et al . |
9,474 | Suppose that you have an abstract for a scientific paper: we consider the cauchy problem for nonlinear schrdinger equations in the presence of a smooth , possibly unbounded , potential .
no assumption is made on the sign of the potential .
if the potential grows at most linearly at infinity , we construct solutions in sobolev spaces ( without weight ) , locally in time . under some natural assumptions , we prove that the @xmath0-solutions are global in time . on the other hand ,
if the potential has a super - linear growth , then the sobolev regularity of positive order is lost instantly , not matter how large it is , unless the initial datum decays sufficiently fast at infinity . .
And you have already written the first three sentences of the full article: we consider the cauchy problem for the ( nonlinear ) schrdinger equation @xmath1 where the potential @xmath2 is smooth and sub - quadratic ( see below ) , the nonlinearity @xmath3 is sufficiently smooth , and the initial data @xmath4 may or may not belong to weighted @xmath5 spaces @xmath6 ( sometimes denoted @xmath7 ) , where @xmath8 stands for the fourier transform .
note that we consider only propagation in the future ; this choice is made only to simplify some statements .
we show that if the potential @xmath2 is sub - linear , then is locally well - posed in @xmath9 , upon suitable assumptions on @xmath3 . on the other hand ,.
Please generate the next two sentences of the article | if @xmath2 is super - linear ( e.g. harmonic potential ) , then is ill - posed in all sobolev spaces of positive order ; this is not a nonlinear result , since it holds even when @xmath10 .
this is heuristically reasonable , at least in the case of the harmonic oscillator : the potential rotates the phase space , so the natural space for the initial data is of the form @xmath11 . if @xmath12 , for @xmath13 , then @xmath14 for arbitrarily small @xmath15 . for the linear equation , this can be seen via the fourier integral representation ( mehler s formula in the case of the harmonic potential ) . |
9,475 | Suppose that you have an abstract for a scientific paper: we study the correspondence between phase - space localization of quantum ( quasi-)energy eigenstates and classical correlation decay , given by ruelle - pollicott resonances of the frobenius - perron operator .
it will be shown that scarred energy eigenstates are correlated : pairs of eigenstates strongly overlap in phase space ( scar in same phase - space regions ) if the difference of their eigenenergies is close to the phase of a leading classical resonance .
phase - space localization of quantum states will be measured by @xmath0 norms of their husimi functions . .
And you have already written the first three sentences of the full article: schnirelman s theorem @xcite as well as berry s physical reasoning predict that quantum energy eigenfunctions ( wigner or husimi representation @xcite ) of systems whose classical counterpart is chaotic are uniformly distributed on the energy shell .
heller , however , has shown that there exist quantum eigenfunctions which are strongly localized ( scarred ) on hyperbolic periodic orbits @xcite . at present , the general opinion is that scars are exceptional , while the majority consits of uniformly ( phase - space ) distributed eigenstates @xcite . on the other hand
, it is well known that there also exist weakly localized eigenfunctions , which continuously fill the `` gap '' between uniformly distributed and strongly localized eigenfunctions ..
Please generate the next two sentences of the article | conveniently , instead of single exceptions we here consider localization properties of the whole set of eigenfunctions of the system ; restricting our studies on finite dimensional hilbert spaces . to that purpose ,
we introduce squared @xmath0 norms of husimi eigenfunctions as a measure for phase - space localization @xcite . |
9,476 | Suppose that you have an abstract for a scientific paper: we evaluate the forward compton scattering off the proton , based on kramers - kronig kind of relations which express the compton amplitudes in terms of integrals of total photoabsorption cross sections .
we obtain two distinct fits to the world data on the unpolarized total photoabsorption cross section , and evaluate the various spin - independent sum rules using these fits . for the sum of proton electric and magnetic dipole polarizabilities , governed by the baldin sum rule
, we obtain the following average ( between the two fits ) : @xmath0 .
an analogous sum rule involving the quadrupole polarizabilities of the proton is evaluated too .
the spin - independent forward amplitude of proton compton scattering is evaluated in a broad energy range .
the results are compared with previous evaluations and the only experimental data point for this amplitude ( at 2.2 gev ) .
we remark on sum rules for the elastic component of polarizabilities . .
And you have already written the first three sentences of the full article: it is long known that the forward compton scattering ( cs ) amplitudes can , by unitarity , causality and crossing , be expressed through integrals of the photoabsorption cross sections @xcite .
the low - energy expansions of these expressions lead to a number of useful sum rules , most notably those of baldin @xcite , and gerasimov , drell and hearn ( gdh ) @xcite . given the photoabsorption cross sections
, one can thus provide a reliable assessment of some of the static electromagnetic properties of the nucleon and nuclei , as well as of the forward cs amplitudes in general ..
Please generate the next two sentences of the article | for the proton , the first such assessments was performed in the early 1970s @xcite . since then
, the knowledge of the photoabsorption cross sections appreciably improved , and yet for the unpolarized case only the baldin sum rule has been updated @xcite . in this work , we provide a re - assessment of the forward spin - independent amplitude of proton cs , and evaluate the associated sum rules involving the _ dipole and quadrupole polarizabilities of the proton_. sum rules are essentially the only way to gain empirical knowledge of the forward cs amplitudes . |
9,477 | Suppose that you have an abstract for a scientific paper: we experimentally study the energy - temperature relationship of a harmonically trapped bose - einstein condensate by transferring a known quantity of energy to the condensate and measuring the resulting temperature change .
we consider two methods of heat transfer , the first using a free expansion under gravity and the second using an optical standing wave to diffract the atoms in the potential .
we investigate the effect of interactions on the thermodynamics and compare our results to various finite temperature theories . .
And you have already written the first three sentences of the full article: calorimetric studies have long been valuable tools for rigorous tests of physical law , ranging from joseph black s early work on latent heat , to measurements of the metallic specific heat showing the inadequacy of drude s classical model .
more recently , the high degree of control available in cold atomic gases has opened up exciting avenues for experimental verification of finite temperature theories of bose and fermi gases @xcite . to date
, however , there have been few works experimentally investigating the energy - temperature relationship of a harmonically trapped bose gas . pioneering work performed by ensher _ et al . _.
Please generate the next two sentences of the article | relied on extracting both release energy and temperature information from time - of - flight images at different evaporation points @xcite .
this work was extended by gerbier _ et al . |
9,478 | Suppose that you have an abstract for a scientific paper: we show how a qubit can be fault - tolerantly encoded in the infinite - dimensional hilbert space of an optical mode .
the scheme is efficient and realizable with present technologies .
in fact , it involves two travelling optical modes coupled by a cross - kerr interaction , initially prepared in coherent states , one of which is much more intense than the other . at the exit of the kerr medium ,
the weak mode is subject to a homodyne measurement and a quantum codeword is conditionally generated in the quantum fluctuations of the intense mode . .
And you have already written the first three sentences of the full article: quantum information has recently entered the domain of continuous variable ( cv ) systems @xcite and quantum error correction theory in particular has been extended to the cv framework @xcite .
in such a framework , the main damage induced by decoherence is typically a small diffusion in the two canonical coordinates characterizing the cv system , which may represent the position and momentum of a particle or two orthogonal field quadratures of an optical mode .
et al . _ have shown that these effects are best fought by encoding quantum information within appropriate _ shift - resistant _ quantum codes of the cv system @xcite . the relevant aspect of the proposal of ref ..
Please generate the next two sentences of the article | @xcite is that , using qubits encoded in such a way , a universal set of fault - tolerant quantum gates can be implemented using only `` cheap '' standard devices which , in the case of a cv optical mode , correspond to beam splitters , phase shifters , squeezers , homodyne and photodetectors . in such a proposal ,
all the difficulties are confined to the preparation of the encoded states which , in the ideal limit , are superpositions of an infinite number of infinitely squeezed states and require the use of particular nonlinear interactions for their generation . |
9,479 | Suppose that you have an abstract for a scientific paper: we present a first - principles method for deriving effective low - energy models of electrons in solids having entangled band structure .
the procedure starts with dividing the hilbert space into two subspaces , the low - energy part ( `` @xmath0 space '' ) and the rest of the space ( `` @xmath1 space '' ) . the low - energy model is constructed for the @xmath0 space by eliminating the degrees of freedom of the @xmath1 space .
the thus derived model contains the strength of electron correlation expressed by a partially screened coulomb interaction , calculated in the constrained random - phase - approximation ( crpa ) where screening channels within the @xmath0 space , @xmath2 , are subtracted .
one conceptual problem of this established downfolding method is that for entangled bands it is not clear how to cut out the @xmath0 space and how to distinguish @xmath2 from the total polarization .
here , we propose a simple procedure to overcome this difficulty . in our scheme , the @xmath0 subspace is cut out from the hilbert space of the kohn sham eigenfunctions with the help of a procedure to construct a localized wannier basis .
the @xmath1 subspace is constructed as the complementary space orthogonal to the @xmath0 subspace .
after this disentanglement , @xmath2 becomes well defined . using the disentangled bands , the effective parameters are uniquely determined in the crpa .
the method is successfully applied to 3@xmath0 transition metals . .
And you have already written the first three sentences of the full article: in the last several decades many new materials with intriguing properties were discovered and synthesized .
these materials range from the high - temperature superconductors to magnetic materials , and the latter have already found real applications in electronic industry .
typically , most of these materials contain elements from the 3@xmath0 or 4@xmath3 rows and their electronic structure is characterized by the presence of a partially filled narrow band across the fermi level ..
Please generate the next two sentences of the article | the fact that the narrow band is partially filled implies that there are many configurations with approximately equal weight rendering a one - particle description of the electronic structure problematic .
indeed , it has been recognized for a long time that many of the intriguing properties of these materials originate from correlations among the electrons residing in the partially filled narrow band . |
9,480 | Suppose that you have an abstract for a scientific paper: nucleation in the two - dimensional @xmath0-state potts model has been studied by means of monte - carlo simulations using the heat - bath dynamics .
the initial metastable state has been prepared by magnetic quench of the ordered low - temperature phase .
the magnetic field dependence of the nucleation time has been measured as the function of the magnetic field for different @xmath0 and lattice sizes at @xmath1 . a size - dependent crossover from the coalescence to nucleation region
is observed at all @xmath0 .
the magnetic field dependence of the nucleation time is roughly described by the classical nucleation theory .
our data show increase of the anisotropy in the shape of the critical droplets with increase of @xmath0 .
* key words : * potts model , nucleation , metastable state , critical droplet , monte - carlo simulations . .
And you have already written the first three sentences of the full article: nucleation of bubbles or droplets of the stable phase is a very common phenomenon which initiates relaxation of metastable states near the first order phase transition in many systems of condensed matter physics @xcite , quantum fields @xcite , and cosmology @xcite .
the main quantity of interest for the theory and applications is the nucleation time , which characterizes the time required by the system to leave the metastable state . in lack of a consistent theory of the metastability
, the nucleation problem has been subjected to extensive study in computer simulations ..
Please generate the next two sentences of the article | numerical data are usually interpreted in terms of the phenomenological classical nucleation theory , or in terms of its field - theoretical version proposed by langer @xcite .
a great deal of this work has been carried out on the ising model supplied with some appropriate dynamics . |
9,481 | Suppose that you have an abstract for a scientific paper: the atlas muon spectrometer is designed to measure muon momenta with a resolution of 4% @ 100 gev / c rising to 10% @ 1 tev / c track momentum .
the spectrometer consists of precision tracking and trigger chambers embedded in a 2 t magnetic field generated by three large air - core superconducting toroids .
the precision detectors provide 50 @xmath0 m tracking resolution to a pseudo - rapidity of 2.7 .
the system also includes an optical monitoring system which measures detector positions with 40 @xmath0 m precision .
this paper reports on the calibration and performance of the atlas muon spectrometer . .
And you have already written the first three sentences of the full article: the atlas experiment@xcite is one of two general purpose collider detectors for the large hadron collider ( lhc ) at cern .
the atlas detector consists of an inner detector employing silicon pixel , strip , and transition radiation tracking detectors , all in a solenoidal magnetic field of 2 tesla ; electromagnetic and hadronic calorimeters using liquid argon and scintillator tile detectors ; and a muon spectrometer .
the muon spectrometer consists of a large air - core barrel and endcap toroid magnets with a @xmath1 between 2 - 6 @xmath2 , and four types of trigger and precision tracking detectors , described below ..
Please generate the next two sentences of the article | the muon spectrometer is designed to measure the transverse momentum ( @xmath3 ) of muons with @xmath4 gev with a resolution of 4% up to @xmath3 of 100 gev and increasing to 10% @ 1 tev .
the atlas muon spectrometer consists of monitored drift tubes ( mdts ) for precision tracking in the spectrometer bending plane , resistive plate chambers ( rpcs ) and thin gap chambers ( tgcs ) for triggering in barrel and endcap , respectively , and cathode strip chambers ( cscs ) for precision measurements in the high - rate endcap inner layer where mdts would have occupancy problems . |
9,482 | Suppose that you have an abstract for a scientific paper: we review properties of the most metal - deficient globular clusters and halo stars in the local universe as of march 2001 , with goals of examining present evidence for the duration of the initial burst of massive cluster formation in the milky way , determining when that burst occurred , and elucidating what appears to be limiting our present understanding .
such issues bear upon many topics to arise later in the symposium .
# 1_#1 _ # 1_#1 _ = # 1 1.25 in .125 in .25 in _ `` he aqu@xmath0 los astros plidos todos llenos de enigma '' _ + pablo neruda , _ el hondero entusiasta _ + .
And you have already written the first three sentences of the full article: the most metal - deficient stars of the local universe provide an unparallelled opportunity to study material representative of a much earlier epoch , perhaps predating the formation of the prominent components of the highest redshift galaxies being discovered today .
while the massive globular star clusters ( gcs ) offer distinct , well - known advantages in such research , individual stellar chemistry is a powerful tool in the quest to understand early galactic history .
unusually comprehensive recent review volumes are those of martnez roger , prez fournn & snchez ( 1999 ) , carney ( 2001 ) and harris ( 2001 ) ..
Please generate the next two sentences of the article | as is well known , the metallicity distribution of the 137 milky way gcs with [ fe / h ] determinations is well described by two gaussian curves centered on [ fe / h]@xmath1@xmath2 and @xmath3 ( harris 2001 ) on the popular zinn & west ( 1984 ) metallicity scale . of particular interest in this context
is that the most metal - deficient clusters have [ fe / h]@xmath4@xmath5 whereas the most metal - deficient halo stars extend to metallicity values more than an order of magnitude lower ( c.f . |
9,483 | Suppose that you have an abstract for a scientific paper: single crystals of pure and cd@xmath0 doped potassium sulfate were grown from aqueous solutions by the slow evaporation technique . from nutrient solutions with a cdso@xmath1 concentration of 4wt.% crystals containing 0.014wt.%
dopant concentration could be obtained .
the x - ray diffraction patterns of powdered crystals confirmed their crystal structures for both cases .
thermal analysis of pure crystals shows that the @xmath2 phase transformation peak around @xmath3c is superimposed with spurious effects , while for cd@xmath0 doped crystals this is not the case .
the thermal hysteresis of the phase transition is 8k for undoped k@xmath4so@xmath1 and is reduced to 3.5k for k@xmath4so@xmath1:cd@xmath0 .
compared to undoped crystals , the optical transmittance of cd@xmath0 doped crystals is higher . , , , , and a. inorganic compounds , b. crystal growth , c. differential scanning calorimetry ( dsc ) , c. thermogravimetric analysis ( tga ) , d. phase transitions 61.10.nz , 61.50.ah , 67.80.gb .
And you have already written the first three sentences of the full article: potassium sulfate k@xmath4so@xmath1 crystallizes at room temperature in the orthorhombic olivine type structure and has four formula units per d@xmath5 unit cell , with lattice constants @xmath6 , @xmath7 , and @xmath8 @xcite . the mineral olivine ( mg , fe)@xmath4sio@xmath1 is a major component of the earth s crust .
( mg , fe)@xmath4sio@xmath1 and its isomorphs a@xmath4bo@xmath1 ( where a = k , nh@xmath1 , rb , cs , b = s , se ) exhibit many interesting physical properties and phase equilibria that were studied repeatedly @xcite . upon heating k@xmath4so@xmath1 undergoes a first order transformation at @xmath9c to a hexagonal structure d@xmath10 with @xmath11 and @xmath12 ( measured at @xmath13c @xcite ) . in this high-@xmath14 structure the oxygen positions of the so@xmath15 tetrahedra are only partially occupied as a result of rotational disorder .
k@xmath4so@xmath1 crystals that are grown at room temperature from aqueous solution incorporate oh@xmath16 ions ..
Please generate the next two sentences of the article | the oh@xmath16 concentration decays in the temperature region from @xmath17c to @xmath18c and usually crystals are destroyed by this process @xcite .
el - kabbany @xcite has reported a thermal hysteresis for the solid phase transformation with @xmath19c at heating and @xmath20c at cooling . |
9,484 | Suppose that you have an abstract for a scientific paper: koi-152 is among the first known systems of multiple transiting planetary candidates @xcite ranging in size from 3.5 to 7 times the size of the earth , in a compact configuration with orbital periods near a 1:2:4:6 chain of commensurability , from 13.5 days to 81.1 days .
all four planets exhibit transit timing variations with periods that are consistent with the distance of each planet to resonance with its neighbors .
we perform a dynamical analysis of the system based on transit timing measurements over 1282 days of _ kepler _ photometry .
stellar parameters are obtained with a combination of spectral classification and the stellar density constraints provided by light curve analysis and orbital eccentricity solutions from our dynamical study .
our models provide tight constraints on the masses of all four transiting bodies , demonstrating that they are planets and that they orbit the same star .
all four of koi-152 s transiting planets have low densities given their sizes , consistent with other studies of compact multiplanet transiting systems .
the largest of the four , koi-152.01 , has the lowest bulk density yet determined amongst sub - saturn mass planets . .
And you have already written the first three sentences of the full article: within our solar system , earth and smaller bodies are primarily mixtures of refractories , rock and metals . in the outer solar system ,
bodies that are too small to retain deep atmospheres contain rock and ices . in the larger planets , including uranus and neptune , the light elements h and he dominate the volume .
there no local examples of bodies intermediate in size or mass between earth ( @xmath0 , @xmath1 ) and uranus / neptune , both of which are larger than 3.8 @xmath2 and more massive than 14 m@xmath3 . mass determinations of transiting exoplanets are beginning to allow the characterization of planets in this size range . as more planetary masses and radii.
Please generate the next two sentences of the article | are measured , their bulk densities will provide more constraints on their compositions . to derive meaningful planetary densities
requires both accurate mass and radius determinations . |
9,485 | Suppose that you have an abstract for a scientific paper: we model the effects of repeated supernova explosions from starbursts in dwarf galaxies on the interstellar medium of these galaxies , taking into account the gravitational potential of their dominant dark matter haloes .
we explore supernova rates from one every 30,000 yr to one every 3 million yr , equivalent to steady mechanical luminosities of @xmath0 ergs s@xmath1 , occurring in dwarf galaxies with gas masses @xmath2 .
we address in detail , both analytically and numerically , the following three questions : 1 .
when do the supernova ejecta blow out of the disk of the galaxy ? 2 .
when blowout occurs , what fraction of the interstellar gas is blown away , escaping the potential of the galactic halo ?
3 . what happens to the metals ejected from the massive stars of the starburst ?
are they retained or blown away ?
we give quantitative results for when blowout will or will not occur in galaxies with @xmath3 .
surprisingly , we find that the mass ejection efficiency is very low for galaxies with mass @xmath4
. only galaxies with @xmath5 have their interstellar gas blown away , and then virtually independently of @xmath6 . on the other hand , metals from the supernova ejecta
are accelerated to velocities larger than the escape speed from the galaxy far more easily than the gas .
we find that for @xmath7 , only about 30% of the metals are retained by a @xmath8 galaxy , and virtually none by smaller galaxies .
we discuss the implications of our results for the evolution , metallicity and observational properties of dwarf galaxies . .
And you have already written the first three sentences of the full article: hierarchical models of structure formation suggest that dwarf galaxies are the building blocks of larger galaxies , merging at high redshift to form the distribution of galaxies we see today .
dwarfs , and even smaller stellar systems , are also responsible for the origin of some of the lyman @xmath9 forest absorption features observed in the spectra of distant quasars ( fransson & epstein 1982 , wang 1995 , ciardi & ferrara 1997 ) .
it is therefore crucial to understand both their formation and evolution . in turn , it has recently become clear that supernova - driven winds play a crucial role in the evolution of such objects since they regulate the mass , metal enrichment , and energy balance of the interstellar medium ( ism ) in these galaxies ..
Please generate the next two sentences of the article | these aspects have been investigated in a number of theoretical papers ( larson 1974 ; dekel & silk 1986 ; silk 1987 ; vader 1986 , 1987 ; and ferrara & tolstoy 1998 , hereafter ft ) both in local and cosmological contexts .
the observational evidence in support of the existence of outflows from dwarf galaxies has grown rapidly in recent years . |
9,486 | Suppose that you have an abstract for a scientific paper: quasiparticle tunneling between two counter - propagating edges through point contacts could provide information on the statistics of the quasiparticles .
previous study on a disk found a scaling behavior by varying the tunneling distance .
it was found that in the limit with zero tunneling distance , the abelian quasiparticles tunneling obey the scaling analysis while the non - abelian quasiparticles exhibit some non - trivial behaviors on the scaling exponents .
because of the limitation of disk geometry , we put the fractional quantum hall ( fqh ) state on the surface of a cylinder which has a larger tunable tunneling distance than that on disk by varying the aspect ratio @xmath0 .
we analyze the scaling behavior of the quasiholes , especially the non - abelian quasiholes in the read - rezayi @xmath1 parafermion states .
we aim to address the existance of the anomalous correction of the scaling parameter in the long tunneling distance . .
And you have already written the first three sentences of the full article: according to the experimentally realizable phases that support topological objects , the fractional quantum hall ( fqh ) effect , since its discovery @xcite , has appealed to tremendous theoretical and experimental attractions and achieved us a collection of methods to study the strongly correlated electron systems .
the quasiparticle excitations in the fqh liquids can have fractional charges and obey fractional statistics @xcite . within a serious of filling factors of fqh states ,
some of them may support more exotic excitations with non - abelian statistics , which have potential applications in the topological protected quantum computation @xcite ..
Please generate the next two sentences of the article | the fqh with an even denominator on the first landau level at filling factor @xmath2 @xcite is the most studied state that belongs to the family of non - abelian fqh states .
since the seminal work of moore and read @xcite , a connection between the wavefunction of the fqh state and the conformal field theory ( cft ) has been established . |
9,487 | Suppose that you have an abstract for a scientific paper: we propose a model equation for the dynamics of tree density in mesic savannas .
it considers long - range competition among trees and the effect of fire acting as a local facilitation mechanism . despite short - range facilitation
is taken to the local - range limit , the standard full spectrum of spatial structures obtained in general vegetation models is recovered .
long - range competition is thus the key ingredient for the development of patterns .
the long time coexistence between trees and grass , and how fires affect the survival of trees as well as the maintenance of the patterns is studied .
the influence of demographic noise is analyzed .
the stochastic system , under the parameter constraints typical of mesic savannas , shows irregular patterns characteristics of realistic situations .
the coexistence of trees and grass still remains at reasonable noise intensities . .
And you have already written the first three sentences of the full article: savannas ecosystems are characterized by the long - term coexistence between a continuous grass layer and scattered or clustered trees @xcite .
occurring in many regions of the world , in areas with very different climatic and ecological conditions , the spatial structure , persistence , and resilience of savannas have long intrigued ecologists @xcite . however , despite substantial research , the origin and nature of savannas have not yet been fully resolved and much remains to be learned .
savanna tree populations often exhibit pronounced , non - random spatial structures @xcite ..
Please generate the next two sentences of the article | much research has therefore focused on explaining how spatial patterning in savannas arises @xcite . in most natural plant systems
both facilitative and competitive processes are simultaneously present @xcite and hard to disentangle @xcite . |
9,488 | Suppose that you have an abstract for a scientific paper: systems of @xmath0 identical phase oscillators with global sinusoidal coupling are known to display low - dimensional dynamics .
although this phenomenon was first observed about 20 years ago , its underlying cause has remained a puzzle .
here we expose the structure working behind the scenes of these systems , by proving that the governing equations are generated by the action of the mbius group , a three - parameter subgroup of fractional linear transformations that map the unit disc to itself . when there are no auxiliary state variables , the group action partitions the @xmath0-dimensional state space into three - dimensional invariant manifolds ( the group orbits ) .
the @xmath1 constants of motion associated with this foliation are the @xmath1 functionally independent cross ratios of the oscillator phases .
no further reduction is possible , in general ; numerical experiments on models of josephson junction arrays suggest that the invariant manifolds often contain three - dimensional regions of neutrally stable chaos .
* large arrays of coupled limit - cycle oscillators have been used to model diverse systems in physics , biology , chemistry , engineering and social science . the special case of phase oscillators coupled all - to - all through sinusoidal interactions has attracted mathematical interest because of its analytical tractability .
about 20 years ago , numerical experiments revealed that these systems display an exceptionally simple form of collective behavior : for all @xmath2 , where @xmath0 is the number of oscillators , all trajectories are confined to manifolds with @xmath3 fewer dimensions than the state space itself .
several insights have been obtained over the past two decades , but it has remained an open problem to pinpoint the symmetry or other structure that causes this non - generic behavior . here we show that group theory provides the explanation : the governing equations for these systems arise naturally from the action of the group of conformal mappings of....
And you have already written the first three sentences of the full article: when a nonlinear system shows unexpectedly simple behavior , it may be a clue that some hidden structure awaits discovery .
for example , recall the classic detective story @xcite that began in the 1950s with the work of fermi , pasta , and ulam @xcite . in their numerical simulations of a chain of anharmonic oscillators ,
fermi et al ..
Please generate the next two sentences of the article | were surprised to find the chain returning almost perfectly , again and again , to its initial state .
the struggle to understand these recurrences led zabusky and kruskal @xcite to the discovery of solitons in the korteweg |
9,489 | Suppose that you have an abstract for a scientific paper: small - angle x - ray scattering and phase - contrast microscopy experiments were performed to investigate the effect of the osmotic pressure on vesicle formation in a dioleoylphosphatidylcholine ( dopc)/water / nai system .
multi - lamellar vesicles were formed when a pure lipid film was hydrated with an aqueous solution of nai . on the other hand , uni - lamellar vesicles ( ulvs )
were formed when a lipid film mixed with an enough amount of nai was hydrated . to confirm the effect of the osmotic pressure due to nai , a free - energy calculation was performed .
this result showed that the osmotic pressure induced an unbinding transition on the hydration process , which resulted in ulv formation . .
And you have already written the first three sentences of the full article: all biomembranes mainly consist of lipid bilayers , and functional proteins float on them .
such bilayers also appear in aqueous solutions of synthesized phospholipids .
therefore , bilayers in such solutions are intensively studied to understand the physical properties of biomembranes . moreover ,.
Please generate the next two sentences of the article | these bilayers form vesicles that attract attention for studying model cells .
such vesicles can be effectively obtained by hydrating dry lipid films on substrates or test tubes . |
9,490 | Suppose that you have an abstract for a scientific paper: an @xmath0-graph is an @xmath0-regular graph where every odd set of vertices is connected by at least @xmath0 edges to the rest of the graph .
seymour conjectured that any @xmath0-graph is @xmath1-edge - colorable , and also that any @xmath0-graph contains @xmath2 perfect matchings such that each edge belongs to two of them .
we show that the minimum counter - example to either of these conjectures is a brick .
furthermore we disprove a variant of a conjecture of fan , raspaud . .
And you have already written the first three sentences of the full article: we consider finite graphs @xmath3 with vertex set @xmath4 and edge set @xmath5 .
the graphs might have multiple edges but no loops , and throughout this paper we assume that the graphs under consideration are connected ( otherwise we will mention this explicitely ) . terms and concepts that we do not define can be found in chapter 3 of @xcite . a perfect matching of a graph @xmath6 is a matching covering all vertices of @xmath6 , and @xmath7 denotes the number of odd components of @xmath6 .
tutte characterized the graphs with perfect matching ..
Please generate the next two sentences of the article | [ tutte](tutte ) a graph @xmath6 has a perfect matching if and only if @xmath8 , for each @xmath9 . a class of graphs possessing a perfect matching is the class of @xmath0-graphs @xcite , which are @xmath0-regular graphs with @xmath10 for every odd @xmath9 , where @xmath11 is the set of edges of @xmath6 with precisely one end in @xmath12 .
the following conjectures are due to seymour @xcite . |
9,491 | Suppose that you have an abstract for a scientific paper: we show that the set @xmath0 of reduced expressions for the longest element in the hyperoctahedral group exhibits the cyclic sieving phenomenon .
more specifically , @xmath0 possesses a natural cyclic action given by moving the first letter of a word to the end , and we show that the orbit structure of this action is encoded by the generating function for the major index on @xmath0 . .
And you have already written the first three sentences of the full article: suppose we are given a finite set @xmath1 , a finite cyclic group @xmath2 acting on @xmath1 , and a polynomial @xmath3 $ ] with integer coefficients .
following reiner , stanton , and white @xcite , we say that the triple @xmath4 exhibits the _
cyclic sieving phenomenon _ ( csp ) if for every integer @xmath5 , we have that @xmath6 where @xmath7 is a root of unity of multiplicitive order @xmath8 and @xmath9 is the fixed point set of the action of the power @xmath10 . the sizes of the fixed point sets determine the cycle structure of the canonical image of @xmath11 in the group of permutations of @xmath1 , @xmath12 ..
Please generate the next two sentences of the article | therefore , to find the cycle structure of the image of any bijection @xmath13 , it is enough to determine the order of the action of @xmath11 on @xmath1 and find a polynomial @xmath14 such that @xmath15 exhibits the csp . the cyclic sieving phenomenon has been demonstrated in a variety of contexts .
the paper of reiner , stanton , and white @xcite itself includes examples involving noncrossing partitions , triangulations of polygons , and cosets of parabolic subgroups of coxeter groups . |
9,492 | Suppose that you have an abstract for a scientific paper: in this paper we present optimization problems with biconvex objective function and linear constraints such that the set of global minima of the optimization problems is the same as the set of nash eqilibria of a n - player general - sum normal form game .
we further show that the objective function is an invex function and consider a projected gradient descent algorithm .
we prove that the projected gradient descent scheme converges to a partial optimum of the objective function .
we also present simulation results on certain test cases showing convergence to a nash equilibrium strategy . .
And you have already written the first three sentences of the full article: a general theory of games first introduced in @xcite has found several applications in the field of economics and engineering .
a solution concept or a notion of equilibrium was proposed by nash ( known as nash equilibrium ) in @xcite and was shown to exist in every finite normal - form game .
further generalizations of nash equilibrium such as correlated equilibrium and coarse correlated equilibrium were also introduced and studied ..
Please generate the next two sentences of the article | it is well known that for every game the set correlated and coarse - correlated equilibria are convex subsets of the strategy space .
but in general the set of nash equilibria is not convex . |
9,493 | Suppose that you have an abstract for a scientific paper: we estimate the contributions to the cosmic microwave background radiation ( cmbr ) power spectrum from the static and kinematic sunyaev - zeldovich ( sz ) effects , and from the moving cluster of galaxies ( mcg ) effect .
we conclude , in agreement with other studies , that at sufficiently small scales secondary fluctuations caused by clusters provide important contributions to the cmbr . at @xmath0 ,
these secondary fluctuations become important relative to lensed primordial fluctuations .
gravitational lensing at small angular scales has been proposed as a way to break the `` geometric degeneracy '' in determining fundamental cosmological parameters .
we show that this method requires the separation of the static sz effect , but the kinematic sz effect and the mcg effect are less important .
the power spectrum of secondary fluctuations caused by clusters of galaxies , if separated from the spectrum of lensed primordial fluctuations , might provide an independent constraint on several important cosmological parameters .
@xmath1 subject headings : cosmic microwave background galaxies : clusters : general methods : numerical .
And you have already written the first three sentences of the full article: the power spectrum of the cosmic microwave radiation ( cmbr ) carries much cosmological information about primordial density fluctuations in the early universe .
as photons leave the last scattering surface and travel across the universe , however , these brightness fluctuations are modified by intervening structures , causing secondary fluctuations , which we would expect to become more important on small angular scales .
the power spectrum of the cmbr alone can be used to determine cosmological parameters ..
Please generate the next two sentences of the article | recently it has been shown , however , that a geometrical degeneracy effect prevents some combinations of cosmological parameters from being disentangled by the power spectrum alone ( @xcite ; @xcite ; @xcite ) .
the primordial density fluctuations and matter content determine the positions and magnitudes of the doppler peaks at the last scattering surface . |
9,494 | Suppose that you have an abstract for a scientific paper: we present a new approach for the analysis of bose - einstein condensates in a few mode approximation . this method has already been used to successfully analyze the vibrational modes in various molecular systems and offers a new perspective on the dynamics in many particle bosonic systems .
we discuss a system consisting of a bose - einstein condensate in a triple well potential .
such systems correspond to classical hamiltonian systems with three degrees of freedom .
the semiclassical approach allows a simple visualization of the eigenstates of the quantum system referring to the underlying classical dynamics . from this classification
we can read off the dynamical properties of the eigenstates such as particle exchange between the wells and entanglement without further calculations .
in addition , this approach offers new insights into the validity of the mean - field description of the many particle system by the gross - pitaevskii equation , since we make use of exactly this correspondence in our semiclassical analysis .
we choose a three mode system in order to visualize it easily and , moreover , to have a sufficiently interesting structure , although the method can also be extended to higher dimensional systems . .
And you have already written the first three sentences of the full article: bose - einstein condensates form one of the main topics of research at the moment .
one reason for this enormous interest is the fact that they combine concepts and techniques from different areas of physics , such as quantum optics , condensed matter physics , molecular physics and quantum chaos . on the experimental side ,
there has been a remarkable progress in confining and manipulating bose - einstein condensates @xcite , which has stimulated the theoretical research in the area ..
Please generate the next two sentences of the article | there has been a large number of previous studies analyzing the dynamics of bose - einstein condensates in a double well potential using a mean - field approach , the gross - pitaevskii equation . in @xcite smerzi _
et al . _ |
9,495 | Suppose that you have an abstract for a scientific paper: in this study we address the question under which conditions a saturated velocity field stemming from geodynamo simulations leads to an exponential growth of the magnetic field in a corresponding kinematic calculation .
we perform global self - consistent geodynamo simulations and calculate the evolution of a kinematically advanced tracer field .
the self - consistent velocity field enters the induction equation in each time step , but the tracer field does not contribute to the lorentz force .
this experiment has been performed by @xcite and is closely related to the test field method by schrinner et al .
( 2005 , 2007 ) .
we find two dynamo regimes in which the tracer field either grows exponentially or approaches a state aligned with the actual self - consistent magnetic field after an initial transition period .
both regimes can be distinguished by the rossby number and coincide with the dipolar and multipolar dynamo regimes identified by @xcite .
dipolar dynamos with low rossby number are kinematically stable whereas the tracer field grows exponentially in the multipolar dynamo regime .
this difference in the saturation process for dynamos in both regimes comes along with differences in their time variability . within our sample of 20 models ,
solely kinematically unstable dynamos show dipole reversals and large excursions .
the complicated time behaviour of these dynamos presumably relates to the alternating growth of several competing dynamo modes .
on the other hand , dynamos in the low rossby number regime exhibit a rather simple time dependence and their saturation merely results in a fluctuation of the fundamental dynamo mode about its critical state .
[ firstpage ] dynamo : theories and simulations ; earth s core ; geomagnetic field ; magnetohydrodynamics . .
And you have already written the first three sentences of the full article: the time variability of cosmic magnetic fields has always been an argument in favour of hydromagnetic dynamo action .
its understanding is crucial for insights in the interior dynamics of stars and planets .
the time dependence of convective dynamos is attributable to a non - stationary buoyancy flux as well as to a time dependent equilibration of the magnetic field ..
Please generate the next two sentences of the article | the latter is subject of the study presented here .
how do dynamos saturate and in particular in which way is the saturation reflected in their time dependence ? in a general description , |
9,496 | Suppose that you have an abstract for a scientific paper: the old exosat medium energy measurements of high frequency ( hf ) agn power spectral normalisation are re - examined in the light of accurate black hole mass determinations which were not available when these data were first published @xcite .
it is found that the normalised variability amplitude ( nva ) , measured directly from the power spectrum , is proportional to @xmath0 where @xmath1 .
as nva is the square root of the power , these observations show that the normalisation of the hf power spectrum for this sample of agn varies very close to inversely with black hole mass .
almost the same value of @xmath2 is obtained whether the quasar 3c273 is included in the sample or not , suggesting that the same process that drives x - ray variability in seyfert galaxies applies also to 3c273 .
these observations support the work of @xcite who show that an almost exactly linear anticorrelation is required if the normalisations of the hf power spectra of agn and x - ray binary systems are to scale similarly .
these observations are also consistent with a number of studies showing that the short timescale variance of agn x - ray lightcurves varies approximately inversely with mass . .
And you have already written the first three sentences of the full article: it is now generally agreed that the x - ray variability properties of @xmath3few solar mass black holes in x - ray binary systems ( xrbs ) and supermassive black holes in active galactic nuclei ( agn ) are similar . with a view to providing an independent method for determining physical parameters such as black hole mass and accretion rate
, there is considerable interest in determining how these parameters might scale with characteristic observable x - ray variability parameters .
x - ray variability can be quantified via the power spectral density ( psd ) and , to first order , the x - ray psds of agn are similar to those of xrbs @xcite , particularly to xrbs in the high - soft state ( e.g. * ? ? ?.
Please generate the next two sentences of the article | * ; * ? ? ?
* ) . in this state the power , @xmath4 , at frequency , @xmath5 , |
9,497 | Suppose that you have an abstract for a scientific paper: a description of photoassociation by cw laser is formulated in the framework of grid methods .
the hamiltonian describing one or several bound states coupled to a multiple of continuum manifolds via a radiative field is written in the energy representation and diagonalized .
the generality of the treatment allows to compute accurately and efficiently physical properties such as non - linear high - intensity energy shifts , line shapes , and photoassociation rates both for isolated and non - isolated resonances .
application is given to sodium photoassociation in the experimental conditions of mc kenzie _ et al _ [ phys .
. lett . * 88 * , 090403 ( 2002 ) ] .
inverted region for the dependency of the rate vs. the intensity and non - symmetric lineshapes were predicted to occur above the saturation limit .
comparison with the model of bohn and julienne [ phys .
rev .
a * 60 * , 414 ( 1999 ) ] is discussed . .
And you have already written the first three sentences of the full article: many experimental groups are presently working on the formation of ultracold molecules and molecular quantum gases .
a very efficient scheme is the photoassociation reaction , where two colliding atoms absorb a photon to make a molecule @xcite ; moreover ultracold photoassociation spectroscopy @xcite is capable of providing deep insight into the properties of long range molecules , cold atomic collisions , or pair correlations in a condensate .
theoretical two - body scattering models have been developed to compute the photoassociation rates @xcite , in the framework of a perturbative treatment , adapted to situations where low - intensity cw lasers are employed and many - body effects are negligible . a linear variation of the photoassociation rate as a function of intensity is then predicted . in the work of bohn and julienne @xcite , which develops a semi - analytic theory yielding laser - induced energy shifts and l ine broadening ,.
Please generate the next two sentences of the article | the departure from this linear behavior is described , the saturation limit at larger laser intensities being evaluated . in a condensate , the two - body model should fail and javanainen and mackie @xcite have developed a many - body theory which predicts a saturation limit occurring at lower intensities and attributed to rogue photodissociation .
the search for saturation effects has stimulated several experiments . |
9,498 | Suppose that you have an abstract for a scientific paper: models of galactic chemical evolution ( cems ) show that the shape of the stellar initial mass function ( imf ) and other assumptions regarding star formation affect the resultant abundance gradients in models of late - type galaxies . furthermore ,
intermediate mass ( i m ) stars undeniably play an important role in the buildup of nitrogen abundances in galaxies . here
i specifically discuss the nitrogen contribution from im / agb stars and how it affects the n / o - gradient . for this purpose
i have modelled the chemical evolution of a few nearby disc galaxies using different imfs and star formation prescriptions .
it is demonstrated that n / o - gradients may be used to constrain the nitrogen contribution from im / agb - stars . .
And you have already written the first three sentences of the full article: much progress has been made in modelling nucleosynthesis in stars in general , but the origin of nitrogen still remains somewhat uncertain . in the classical picture , the apparent increase in nitrogen production with metallicity , as inferred from spectroscopy of galactic and extragalactic hii - regions , is a manifestation of nitrogen being either primary or secondary ( produced from primordial elements or with heavier elements as `` seeds '' ) .
however , reality often turns out to be more complex than our simplest models of it .
the origin of nitrogen is probably no exception . during the last few years.
Please generate the next two sentences of the article | , reasonably accurate stellar nitrogen abundances have become available also for population ii stars ( see , e.g. , @xcite ) .
the rather large nitrogen abundances relative to iron seen in halo stars in the milky way suggest that a relatively large fraction of the nitrogen should come from type ii supernovae , especially at low metallicity . |
9,499 | Suppose that you have an abstract for a scientific paper: an ultrametric topology formalizes the notion of hierarchical structure .
an ultrametric embedding , referred to here as ultrametricity , is implied by a natural hierarchical embedding .
such hierarchical structure can be global in the data set , or local . by quantifying extent or degree of ultrametricity in a data set ,
we show that ultrametricity becomes pervasive as dimensionality and/or spatial sparsity increases .
this leads us to assert that very high dimensional data are of simple structure .
we exemplify this finding through a range of simulated data cases .
we discuss also application to very high frequency time series segmentation and modeling .
pacs : 02.50.-r , 05.45.tp , 89.65.gh , 89.20.-a .
And you have already written the first three sentences of the full article: the topology or inherent shape and form of an object is important . in data analysis ,
the inherent form and structure of data clouds are important .
quite a few models of data form and structure are used in data analysis ..
Please generate the next two sentences of the article | one of them is a hierarchically embedded set of clusters , a hierarchy .
it is traditional ( since at least the 1960s ) to impose such a form on data , and if useful to assess the goodness of fit . rather than fitting a hierarchical structure to data ( e.g. , @xcite ) , |
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