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12,100 |
Suppose that you have an abstract for a scientific paper: the behaviour of the topological susceptibility in qcd with two colours and 8 flavours of quarks is studied at nonzero temperature on the lattice across the finite density transition .
it is shown that its signal drops at a ( pseudo)critical chemical potential @xmath0 .
the polyakov loop and the chiral condensate undergo their transitions at the same value .
pauli blocking supervenes at a value of the chemical potential larger than @xmath0 . .
And you have already written the first three sentences of the full article: the phase space of qcd in the temperature and quark chemical potential @xmath1 plane is shown schematically in fig .
many of the transition lines and phases displayed in the figure are theoretical predictions with little experimental verification .
we have studied the transition as the chemical potential is varied ( dashed arrow in fig ..
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[ fig1 ] ) at a fixed temperature @xmath2 that is most likely above the region where a diquark condenses .
we wanted to understand the fate of the topological susceptibility @xmath3 across the transition and to decide whether its possible change occurs at the same value of @xmath1 where the vector chiral symmetry is restored and the polyakov loop signal rises @xcite .
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12,101 |
Suppose that you have an abstract for a scientific paper: the cl1604 supercluster at @xmath0 is one of a small handful of such structures discovered in the high redshift universe , and is the first target observed as part of the observations of redshift evolution in large scale environments ( orelse ) survey . to date ,
cl1604 is the largest structure mapped at @xmath1 , with the most constituent clusters and the largest number of spectroscopically confirmed member galaxies . in this paper
we present the results of a spectroscopic campaign to create a three - dimensional map of cl1604 and to understand the contamination by fore- and background large scale structures .
combining new deep imaging multi - object spectrograph observations with previous data yields high - quality redshifts for 1,138 extragalactic objects in a @xmath2deg@xmath3 region , 413 of which are supercluster members .
we examine the complex three dimensional structure of cl1604 , providing velocity dispersions for eight of the member clusters and groups .
our extensive spectroscopic dataset is used to examine potential biases in cluster velocity dispersion measurements in the presence of overlapping structures and filaments .
we also discuss other structures found along the line - of - sight , including a filament at @xmath4 and two serendipitously discovered groups at @xmath5 . .
And you have already written the first three sentences of the full article: superclusters are complex structures , consisting of multiple galaxy clusters and groups connected by chains of galaxies
. they can reach sizes of @xmath6 mpc , making them the largest structures in the universe .
as such , they can be used to provide an estimate of the baryonic mass fraction @xmath7 . their frequency and topology may be used to test the veracity of large scale cosmological simulations . because they contain structures spanning a wide range of projected and local densities , superclusters are ideal sites for studying the variety of physical processes affecting galaxy evolution , including ram pressure stripping , mergers , tidal encounters , harassment , etc ..
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they are also sites of cluster - cluster interactions , allowing us to probe how cluster - scale interactions effect their constituent galaxies , and to probe possible differences between the dark and baryonic matter distributions .
recent deep , wide - field imaging campaigns have begun to reveal an increasing number of superclusters at @xmath8 .
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12,102 |
Suppose that you have an abstract for a scientific paper: we consider the following problem of decentralized statistical inference : given i.i.d .
samples from an unknown distribution , estimate an arbitrary quantile subject to limits on the number of bits exchanged . we analyze a standard fusion - based architecture , in which each of @xmath0 sensors transmits a single bit to the fusion center , which in turn is permitted to send some number @xmath1 bits of feedback . supposing that each of @xmath0 sensors receives @xmath2 observations , the optimal centralized protocol yields mean - squared error decaying as @xmath3)$ ] .
we develop and analyze the performance of various decentralized protocols in comparison to this centralized gold - standard .
first , we describe a decentralized protocol based on @xmath4 bits of feedback that is strongly consistent , and achieves the same asymptotic mse as the centralized optimum .
second , we describe and analyze a decentralized protocol based on only a single bit ( @xmath5 ) of feedback . for step sizes independent of @xmath6 , it achieves an asymptotic mse of order @xmath7 $ ] , whereas for step sizes decaying as @xmath8 , it achieves the same @xmath3)$ ] decay in mse as the centralized optimum .
our theoretical results are complemented by simulations , illustrating the tradeoffs between these different protocols .
* keywords : * decentralized inference ; communication constraints ; distributed estimation ; non - parametric estimation ; quantiles ; sensor networks ; stochastic approximation . .
And you have already written the first three sentences of the full article: whereas classical statistical inference is performed in a centralized manner , many modern scientific problems and engineering systems are inherently _ decentralized _ : data are distributed , and can not be aggregated due to various forms of communication constraints .
an important example of such a decentralized system is a sensor network @xcite : a set of spatially - distributed sensors collect data about the environmental state ( e.g. , temperature , humidity or light ) .
typically , these networks are based on ad hoc deployments , in which the individual sensors are low - cost , and must operate under very severe power constraints ( e.g. , limited battery life ) . in statistical terms ,.
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such communication constraints imply that the individual sensors can not transmit the raw data ; rather , they must compress or quantize the data for instance , by reducing a continuous - valued observation to a single bit and can transmit only this compressed representation back to the fusion center . by now , there is a rich literature in both information theory and statistical signal processing on problems of decentralized statistical inference .
a number of researchers , dating back to the seminal paper of tenney and sandell @xcite , have studied the problem of hypothesis testing under communication - constraints ; see the survey papers @xcite and references therein for overviews of this line of work .
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12,103 |
Suppose that you have an abstract for a scientific paper: over the recent years , there has been a growing interest in developing new research evaluation methods that could go beyond the traditional citation - based metrics .
this interest is motivated on one side by the wider availability or even emergence of new information evidencing research performance , such as article downloads , views and twitter mentions , and on the other side by the continued frustrations and problems surrounding the application of purely citation - based metrics to evaluate research performance in practice .
semantometrics are a new class of research evaluation metrics which build on the premise that full - text is needed to assess the value of a publication .
this paper reports on the analysis carried out with the aim to investigate the properties of the semantometric _ contribution _ measure @xcite , which uses semantic similarity of publications to estimate research contribution , and provides a comparative study of the contribution measure with traditional bibliometric measures based on citation counting .
< ccs2012 > < concept >
< concept_id>10010147.10010178.10010179</concept_id > < concept_desc > computing methodologies natural language processing</concept_desc > < concept_significance>500</concept_significance >
< /concept > < concept > < concept_id>10002951.10003317</concept_id > < concept_desc > information systems information retrieval</concept_desc > < concept_significance>300</concept_significance > < /concept >
< /ccs2012 > .
And you have already written the first three sentences of the full article: this work was supported by jisc under contract no .
we have introduced the idea of semantometrics in @xcite as a new class of metrics for evaluating research . as opposed to existing bibliometrics , webometrics , altmetrics , etc .
, semantometrics are not based on measuring the number of interactions in the scholarly communication network , but build on the premise that full - text is needed to assess the value of a publication . in @xcite.
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we have attempted to create the first semantometric measure based on the idea of measuring the progress of scholarly discussion .
our hypothesis states that the added value of publication _
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12,104 |
Suppose that you have an abstract for a scientific paper: we show that all projective integral varieties which are not cones and have a cohen - macaulay coordinate ring are of wild cm type , except for a few cases which we completely classify . .
And you have already written the first three sentences of the full article: a classical result in representation theory of quivers is gabriel s theorem , stating that a connected quiver supports only finitely many irreducible representations ( i.e. , of indecomposable modules over the associated path algebra ) if and only if it is of type @xmath0 , @xmath1 , @xmath2 .
the classification of tame quivers as _ euclidean graphs _ , or _ extended dynkin diagrams _ , of type @xmath3 , @xmath4 , @xmath5 came shortly afterwards . remarkably , any other quiver supports arbitrarily large families of indecomposable representations , i.e. , to be of _ wild representation type_. in algebraic geometry , the relevant problem in representation theory of algebras concerns the complexity of the category of maximal cohen - macaulay modules over the coordinate ring @xmath6 $ ] of a closed subvariety @xmath7 defined over an algebraically closed field @xmath8 . for @xmath9 , assuming @xmath6 $ ] to be cohen - macaulay ( so @xmath10 is said to be arithmetically cohen - macaulay , briefly acm ) , these in turn correspond to acm sheaves , namely coherent sheaves @xmath11 on @xmath10 without intermediate cohomology i.e. satisfying @xmath12 for all @xmath13 and @xmath14 . for hypersurfaces , in view of @xcite these modules also correspond to matrix factorizations , which in turn are related to mirror symmetry , cf .
@xcite . in this sense , reduced projective acm varieties of finite cm type have been classified in @xcite , cf . also @xcite . their list ( for positive dimension ).
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consists of rational normal curves , projective spaces , smooth quadrics , the veronese surface in @xmath15 and the cubic scroll in @xmath16 .
this ties in with grothendieck s classical result on the splitting of vector bundles over @xmath17 , @xcite , in turn rooted in ideas of segre , @xcite . our goal here is to tell what happens to other varieties .
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12,105 |
Suppose that you have an abstract for a scientific paper: we present a study of the extent to which the sellwood & binney radial migration of stars is affected by their vertical motion about the midplane .
we use both controlled simulations in which only a single spiral mode is excited , as well as slightly more realistic cases with multiple spiral patterns and a bar .
we find that rms angular momentum changes are reduced by vertical motion , but rather gradually , and the maximum changes are almost as large for thick disc stars as for those in a thin disc .
we find that particles in simulations in which a bar forms suffer slightly larger angular momentum changes than in comparable cases with no bar , but the cumulative effect of multiple spiral events still dominates .
we have determined that vertical action , and not vertical energy , is conserved on average during radial migration .
[ firstpage ] galaxies : kinematics and dynamics galaxies : evolution galaxies : structure . .
And you have already written the first three sentences of the full article: it has recently become clear that galaxy discs evolve significantly over time due to both internal and external influences ( see * ? ? ?
* ; * ? ? ?
* for reviews ) . scattering by giant molecular clouds @xcite is now thought to play a minor role @xcite , while spirals @xcite and interactions @xcite are believed to cause more substantial changes . the milky way is believed to have both a thin and a thick disc @xcite , as do perhaps many disc galaxies @xcite ..
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relative to the thin disc , the thick disc has a higher velocity dispersion , lags in its net rotational velocity @xcite , contains older stars with lower metallicities @xcite and enhanced [ @xmath0/fe ] ratios @xcite .
a number of different criteria have been used to divide stars into the two disc populations , and some of these trends may depend somewhat on whether a spatial , kinematic , or chemical abundance criterion is applied @xcite . recently , @xcite suggest that there is no sharp distinction into two populations , but rather a continuous variation in these properties .
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12,106 |
Suppose that you have an abstract for a scientific paper: operator entanglement of two - qubit joint unitary operations is revisited .
schmidt number is an important attribute of a two - qubit unitary operation , and may have connection with the entanglement measure of the unitary operator .
we found the entanglement measure of two - qubit unitary operators is classified by the schmidt number of the unitary operators .
the exact relation between the operator entanglement and the parameters of the unitary operator is clarified too . .
And you have already written the first three sentences of the full article: unitary operations have been placed in a very important position in the quantum communication and entanglement manipulating , such as , quantum cryptography@xcite , teleportation@xcite , entanglement swapping@xcite , quantum states purification[4 ] , entanglement production@xcite and so on . in quantum teleportation , to transfer the unknown quantum state to the remote user , the sender must apply an joint unitary operator on the unknown state particle and one of the entangled particles . in quantum entanglement swapping , a joint unitary transformation on two particles(they
are from two different entangled pairs ) will let two remote particles entangled without direct interaction . in entanglement purification process , joint unitary operations and measurements can transfer the entanglement from many partially entangled pairs to few near perfect entangled pairs . in entanglement generation , the joint unitary operations and single qubit operations can let the initially product particles entangled . from the above applications we can see that , it is the nonlocal attribute of the bipartite joint unitary transformation that plays the most important role .
the nonlocal attribute of a bipartite joint unitary operator has been studied from different aspects , such as entangling power@xcite , operator entanglement@xcite , and entanglement - changing power@xcite ..
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entangling power is the mean entanglement(linear entropy ) produced by acting with u on a given distribution of pure product states@xcite . because a quantum operator belongs to a hilbert - schmidt space
, one can consider the entanglement of the operator itself , which is named as operator entanglement@xcite .
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12,107 |
Suppose that you have an abstract for a scientific paper: we report on our implementation of the rhmc algorithm for the simulation of lattice qcd with two staggered flavors on graphics processing units , using the nvidia cuda programming language .
the main feature of our code is that the gpu is not used just as an accelerator , but instead the whole molecular dynamics trajectory is performed on it . after pointing out the main bottlenecks and how to circumvent them ,
we discuss the obtained performances .
we present some preliminary results regarding opencl and multigpu extensions of our code and discuss future perspectives . lattice qcd , graphics processing units .
And you have already written the first three sentences of the full article: graphics processing units ( gpus ) have been developed originally as co - processors meant to fast deal with graphics tasks . in recent years
the video game market developments compelled gpus manufacturers to increase the floating point calculation performance of their products , by far exceeding the performance of standard cpus in floating point calculations .
the architecture evolved toward programmable many - core chips that are designed to process in parallel massive amounts of data ..
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these developments suggested the possibility of using gpus in the field of high - performance computing ( hpc ) as low - cost substitutes of more traditional cpu - based architectures : nowadays such possibility is being fully exploited and gpus represent an ongoing breakthrough for many computationally demanding scientific fields , providing consistent computing resources at relatively low cost , also in terms of power consumption ( watts / flops ) .
due to their many - core architectures , with fast access to the on - board memory , gpus are ideally suited for numerical tasks allowing for data parallelism , for simd ( single instruction multiple data ) parallelization .
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12,108 |
Suppose that you have an abstract for a scientific paper: we study several problems related to the construction and the use of effective lagrangians by considering an extension of the standard model that includes a heavy scalar singlet coupled to the leptonic doublet .
starting from the full renormalizable model , we build an effective field theory by integrating out the heavy scalar . a local effective lagrangian ( up to operators of dimension six )
is obtained by expanding the one - loop effective action in inverse powers of the heavy mass .
this is done by matching some green functions calculated with both the full and the effective theories . using this simple example we study the renormalization of effective lagrangians in general and
discuss how they can be used to bound new physics .
we also discuss the effective lagrangian after spontaneous symmetry breaking , and the use of the standard model classical equations of motion to rewrite it in different forms .
the final effective lagrangian in the physical basis is wel suited to the study of the phenomenology of the model , which we comment on briefly . finally ,
as an example of the use of our effective field theory , we consider the leptonic flavour - changing decay of the @xmath0 boson in the effective theory and compare the results obtained with the full model calculation .
-1 in -1 in 16.3 cm to to 0.3em department of physics + univ .
bielefeld , postfach 8640 + d-33615 bielefeld ,
germany0.5em 0.3em and0.5em 0.3em th division , cern , 1211 genve 23 , switzerland0.5em cern - th.7030/93 + october 1993 ) alexander von humboldt fellow . on leave of absence from the joint institute for nuclear research , dubna , russia . * ) on leave of absence from departament de fsica terica , universitat de valncia , and ific , valncia , spain . .
And you have already written the first three sentences of the full article: effective lagrangians @xcite have been used for a long time as a systematic method to incorporate the known symmetries of a problem into the quantum field theory language . however , with the advent of yang - mills theories and the higgs mechanism , which allowed the construction of physically interesting renormalizable theories , they were used only for those problems that could not be treated in any other way . particularly important have been its applications to low - energy strong interactions in the form of the so - called chiral perturbation theory @xcite and more recently the heavy quark effective field theory @xcite .
its application to weak interactions has been less intensive , since in the last decade the main effort has been in the direction of building complete renormalizable theories that could serve as alternatives or extensions of the standard model , by just enlarging the number of fermions , gauge bosons and scalars .
renormalizability was considered to be a main point and completely linked to predictability , because non - renormalizable models need an infinite number of parameters to be completely described ..
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the striking confirmation of many of the standard model predictions in lep experiments has started to change this point of view .
almost every one now thinks that the standard model correctly describes physics at present energies and perhaps also up to energies close to the tev range .
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12,109 |
Suppose that you have an abstract for a scientific paper: @xmath0prolog is known to be well - suited for expressing and implementing logics and inference systems .
we show that lemmas and definitions in such logics can be implemented with a great economy of expression .
we encode a higher - order logic using an encoding that maps both terms and types of the object logic ( higher - order logic ) to terms of the metalanguage ( @xmath0prolog ) .
we discuss both the terzo and teyjus implementations of @xmath0prolog .
we also encode the same logic in twelf and compare the features of these two metalanguages for our purposes . .
And you have already written the first three sentences of the full article: it has long been the goal of mathematicians to minimize the set of assumptions and axioms in their systems .
implementers of theorem provers use this principle : they use a logic with as few inference rules as possible , and prove lemmas outside the core logic in preference to adding new inference rules . in applications of logic to computer security such as _ proof - carrying code _
@xcite and distributed authentication frameworks @xcite the implementation of the core logic is inside the trusted code base ( tcb ) , while proofs need not be in the tcb because they can be checked ..
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two aspects of the core logic are in the tcb : a set of logical connectives and inference rules , and a program in some underlying programming language that implements proof checking that is , interpreting the inference rules and matching them against a theorem and its proof .
definitions and lemmas are essential in constructing proofs of reasonable size and clarity .
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12,110 |
Suppose that you have an abstract for a scientific paper: we report on the results of a theoretical study of the central exclusive production of scalar @xmath0 meson via @xmath1 decay in high - energy hadron collisions at the rhic , tevatron and lhc .
the corresponding amplitude for exclusive double - diffractive @xmath2 meson production was obtained within the @xmath3-factorization approach including virtualities of active gluons and the cross section is calculated with unintegrated gluon distribution functions ( ugdfs ) known from the literature .
the four - body @xmath4 reaction constitutes an irreducible background to the exclusive @xmath2 meson production .
we include the absorption effects due to proton - proton interaction and pion - pion rescattering .
several differential distributions for @xmath5 process , including the absorptive corrections , were calculated .
the influence of kinematical cuts on the signal - to - background ratio is investigated .
@xmath6 decay , diffractive processes , two - pion continuum .
And you have already written the first three sentences of the full article: the mechanism of exclusive production of mesons at high energies became recently a very active field of research ( see @xcite and refs . therein ) . these reactions @xmath7 ,
where @xmath8 , @xmath2 , provide a valuable tool to investigate in detail the properties of resonance states at high energies .
the recent works concentrated on the production of @xmath9 mesons ( see e.g. refs ..
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@xcite ) where the qcd mechanism is similar to the exclusive production of the higgs boson . furthermore
, the @xmath10 states are expected to annihilate via two - gluon processes into light mesons and may , therefore , allow the study of glueball production dynamics .
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12,111 |
Suppose that you have an abstract for a scientific paper: hyperuniform many - particle distributions possess a local number variance that grows more slowly than the volume of an observation window , implying that the local density is effectively homogeneous beyond a few characteristic length scales .
previous work on maximally random strictly jammed sphere packings in three dimensions has shown that these systems are hyperuniform and possess unusual quasi - long - range pair correlations decaying as @xmath0 , resulting in anomalous logarithmic growth in the number variance .
however , recent work on maximally random jammed sphere packings with a size distribution has suggested that such quasi - long - range correlations and hyperuniformity are not universal among jammed hard - particle systems . in this paper
we show that such systems are indeed hyperuniform with signature quasi - long - range correlations by characterizing the more general local - volume - fraction fluctuations .
we argue that the regularity of the void space induced by the constraints of saturation and strict jamming overcomes the local inhomogeneity of the disk centers to induce hyperuniformity in the medium with a linear small - wavenumber nonanalytic behavior in the spectral density , resulting in quasi - long - range spatial correlations scaling with @xmath1 in @xmath2 euclidean space dimensions .
a numerical and analytical analysis of the pore - size distribution for a binary mrj system in addition to a local characterization of the @xmath3-particle loops governing the void space surrounding the inclusions is presented in support of our argument .
this paper is the first part of a series of two papers considering the relationships among hyperuniformity , jamming , and regularity of the void space in hard - particle packings . .
And you have already written the first three sentences of the full article: maximally random jammed ( mrj ) packings of hard particles are the most disordered structures , according to some well - defined order metrics , that are rigorously incompressible and nonshearable @xcite .
these systems are prototypical `` glassy '' structures in the sense that they are structurally rigid yet lack bragg peaks in their scattering spectra @xcite . in this sense
, the idea of the mrj state has replaced the mathematically ill - defined notion of random close packing @xcite ..
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nearly half - a - century ago these systems were thought to describe the disordered structure of liquids @xcite , but it is now known that three - dimensional mrj monodisperse sphere packings possess unusual quasi - long - range ( qlr ) pair correlations decaying as @xmath0 @xcite .
this property is markedly different from typical liquids , in which pair correlations decay exponentially fast @xcite .
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12,112 |
Suppose that you have an abstract for a scientific paper: a summary of the present standard model higgs search and measurement of top quark mass at the tevatron are presented .
the sensitivity of the present higgs search at the tevatron is limited by statistics to a cross section approximately two orders of magnitude higher than the predicted cross section for standard model higgs production . with 30 fb@xmath0 of integrated luminosity , the tevatron offers an unique potential discovery window for the standard model higgs mass up to 130 gev / c@xmath1 before lhc era .
the study of top at the tevatron has moved from discovery phase to one of characterizing its properties .
the combined result of top quark mass is @xmath2 gev / c@xmath1 ( @xmath3 ) . .
And you have already written the first three sentences of the full article: for several decades , the standard model has been remarkably successful in explaining and predicting experimental data .
however , the mechanism of electroweak symmetry breaking is still not known .
the most popular mechanism to induce spontaneous symmetry breaking of a gauge theory , resulting in the gauge bosons and fermions acquiring masses , is the higgs mechanism @xcite , which predicts the existence of a higgs particle with unknown mass ..
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the current direct search limit @xcite for standard model higgs boson at lep-2 is @xmath4 gev / c@xmath1 at 95% c.l .
lep-2 will continue their run until the end of year 2000 , which will allow them to either exclude the higgs mass up to 110 gev / c@xmath1 or have a 5 @xmath5 higgs discovery for higgs mass below 106 gev / c@xmath1 .
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12,113 |
Suppose that you have an abstract for a scientific paper: zero - field specific heat of the single crystals @xmath0ni@xmath1b@xmath1c
( @xmath0= er , ho , dy , tb , gd ) was measured within the temperature range 0.1 k@xmath225 k. linearized spin wave analysis was successfully applied to account for and to rationalize the thermal evolution of the low temperature magnetic specific heats of all the studied compounds ( as well as the one reported for tmni@xmath3b@xmath1c ) in terms of only two parameters , namely an energy gap @xmath4 and a characteristic temperature @xmath5 .
the evolution of @xmath5 and @xmath4 across the studied compounds correlates very well with the known magnetic properties . @xmath6 as a measure of the effective @xmath7 exchange couplings , scales reasonably well with the de gennes factor .
@xmath8 on the other hand , reflects predominately the anisotropic properties : @xmath9 k for gdni@xmath1b@xmath1c , @xmath10 k for erni@xmath1b@xmath1c , @xmath11 k for tbni@xmath3b@xmath1c , and @xmath12 k for each of honi@xmath1b@xmath1c and dyni@xmath1b@xmath3c .
the equality in @xmath4 of honi@xmath1b@xmath1c and dyni@xmath1b@xmath1c , coupled with the similarity in their magnetic configurations , indicates that a variation of @xmath13 in the solid solution ho@xmath14dy@xmath15ni@xmath1b@xmath1c ( @xmath16 and @xmath17 ) would not lead to any softening of @xmath4 .
this supports the hypothesis of cho et al ( prl * 77*,163(1996 ) ) concerning the influence of the collective magnetic excitations on the superconducting state .
this work underlines the importance of spin - wave excitations for a valid description of low - temperature thermodynamics of borocarbides . .
And you have already written the first three sentences of the full article: wide varieties of magnetic ground structures are manifested in @xmath0ni@xmath3b@xmath1c series ( see e.g. refs.@xcite and tab.i ) : members with @xmath18ho , dy , nd , pr adopt commensurate antiferromagnetic ( af ) arrangements while those with @xmath18tm , er , tb , gd , assume squared - up spin - density wave ( sdw ) states .
these ground structures are stabilized by a fine balance of exchange , crystalline electric field ( cef ) , and magnetoelastic forces . under magnetic field or temperature variation ,
most of these structures undergo a cascade of phase transformations , yielding rich varieties of field - temperature ( @xmath19 ) phase diagrams ( see e.g. refs.@xcite ) ..
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interestingly , most of the zero - field magnetic states of @xmath0=tm , er , ho , dy coexist with superconductivity , presenting model compounds wherein the interplay between superconductivity and magnetism can be investigated .
such investigations revealed that the superconductivity , though much influenced by , has a very weak influence on the prevailing magnetic order:@xcite the energy gain due to the onset of magnetic order dominates by two order of magnitudes over that due to the onset of superconductivity .
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12,114 |
Suppose that you have an abstract for a scientific paper: the dynamics and the thermodynamics of particles / spins interacting via long - range forces display several unusual features with respect to systems with short - range interactions . the hamiltonian mean field ( hmf ) model , a hamiltonian system of n classical inertial spins with infinite - range interactions represents a paradigmatic example of this class of systems .
the equilibrium properties of the model can be derived analytically in the canonical ensemble : in particular the model shows a second order phase transition from a ferromagnetic to a paramagnetic phase .
strong anomalies are observed in the process of relaxation towards equilibrium for a particular class of out - of - equilibrium initial conditions .
in fact the numerical simulations show the presence of quasi - stationary state ( qss ) , i.e. metastable states which become stable if the thermodynamic limit is taken before the infinite time limit .
the qss differ strongly from boltzmann - gibbs equilibrium states : they exhibit negative specific heat , vanishing lyapunov exponents and weak mixing , non - gaussian velocity distributions and anomalous diffusion , slowly - decaying correlations and aging .
such a scenario provides strong hints for the possible application of tsallis generalized thermostatistics .
the qss have been recently interpreted as a spin - glass phase of the model .
this link indicates another promising line of research , which is not alternative to the previous one .
leer.eps gsave 72 31 moveto 72 342 lineto 601 342 lineto 601 31 lineto 72 31 lineto showpage grestore .
And you have already written the first three sentences of the full article: since the original paper by ising @xcite , magnetic models on a lattice have been extensively used over the years to investigate the statistical physics of interacting many - body systems . in particular , many generalizations of the ising model have been proposed . among them , also models with long - range interactions .
the thermodynamics and the dynamics of systems of particles interacting with long - range forces are particularly interesting because display a series of anomalies with respect to systems with short - range interactions@xcite . by long - range interaction
it is usually intended that the modulus of the potential energy decays , at large distance , not faster than the inverse of the distance to the power of the spatial dimension ..
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the main reason of the observed anomalies is that systems with long - range forces in general violate _
extensivity _ and _ additivity _ , two basic properties to derive the thermodynamics of a system .
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12,115 |
Suppose that you have an abstract for a scientific paper: multi - antenna or multiple - input multiple - output ( mimo ) technique can significantly improve the efficiency of radio frequency ( rf ) signal enabled wireless energy transfer ( wet ) . to fully exploit the energy beamforming gain at the energy transmitter ( et ) ,
the knowledge of channel state information ( csi ) is essential , which , however , is difficult to be obtained in practice due to the energy and hardware limitation of the energy receiver ( er ) . to overcome this difficulty , under a point - to - point mimo wet setup , this paper proposes a general design framework for a new type of channel learning method based on the er s energy measurement feedback . specifically , the er measures and encodes the harvested energy levels over different training intervals into bits , and sends them to the et via a feedback link of limited rate . based on the energy - level feedback , the et adjusts transmit beamforming in subsequent training intervals and obtains refined estimates of the mimo channel by leveraging the technique of analytic center cutting plane method ( accpm ) in convex optimization . under this general design framework
, we further propose two specific feedback schemes based on energy quantization and energy comparison , where the feedback bits at each interval are generated at the er by quantizing the measured energy level at the current interval and comparing it with those in previous intervals , respectively .
numerical results are provided to compare the performance of the two feedback schemes .
it is shown that energy quantization performs better when the number of feedback bits per interval is large , while energy comparison is more effective vice versa .
wireless energy transfer ( wet ) , energy beamforming , channel learning , limited feedback , analytic center cutting plane method ( accpm )
. [ section ] [ section ] [ section ] [ section ] [ section ] [ section ] [ section ] [ section ] .
And you have already written the first three sentences of the full article: radio frequency ( rf ) signal enabled wireless energy transfer ( wet ) has become a promising technology to provide perpetual , cost - effective , and convenient energy supply to low - power wireless devices such as rf identification ( rfid ) tags and sensor nodes for various low - power applications in future smart commercial and industrial systems with wireless internet - of - things ( iot ) @xcite . in rf - based wet systems , dedicated energy transmitters ( ets )
are deployed to control and coordinate the transfer of wireless energy via rf signals to a set of distributed energy receivers ( ers ) , and each er uses the rectifier at each of its receive antennas ( also known as rectennas as a whole ) to convert the received rf signals to direct current ( dc ) signals , which are combined to charge the battery at the er @xcite ( see , e.g. , a point - to - point wet system in fig .
[ fig : system ] ) ..
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examples of commercial ers include the p2110 and p2210 powerharvester receivers developed by the powercast company @xcite .
due to the long operating range ( say , tens of meters ) and flexibility to charge multiple devices at the same time ( thanks to the broadcast property of radio signal ) , rf - based far - field wet has competitive advantages over existing near - field wet techniques such as induction coupling , which generally operates with much shorter distance ( say , centimeters ) and for point - to - point power transfer only @xcite .
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Suppose that you have an abstract for a scientific paper: complex 1-variable polynomials with connected julia sets and only repelling periodic points are called _ dendritic_. by results of kiwi , any dendritic polynomial is semi - conjugate to a topological polynomial whose topological julia set is a dendrite .
we construct a continuous map of the space of all cubic dendritic polynomials onto a laminational model that is a quotient space of a subset of the closed bidisk .
this construction generalizes the `` pinched disk '' model of the mandelbrot set due to douady and thurston .
it can be viewed as a step towards constructing a model of the cubic connectedness locus . .
And you have already written the first three sentences of the full article: the _ parameter space _ of complex degree @xmath0 polynomials is by definition the space of affine conjugacy classes of these polynomials .
equivalently , one can talk about the space of all _ monic central polynomials _ of degree @xmath0 , i.e. polynomials of the form @xmath1 .
any polynomial is affinely conjugate to a monic central polynomial ..
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an important set is the _ connectedness locus _ @xmath2 consisting of classes of all degree @xmath0 polynomials @xmath3 , whose julia sets @xmath4 ( equivalently , whose _ filled julia sets _
@xmath5 ) are connected .
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Suppose that you have an abstract for a scientific paper: two measurements related to the proton and anti - proton production near midrapidity in @xmath0 = 7.7 , 11.5 , 19.6 , 27 , 39 , 62.4 and 200 gev au+au collisions using the star detector at the relativistic heavy ion collider ( rhic ) are discussed . at intermediate impact parameters
the slope parameter of the directed flow versus rapidity ( @xmath1 ) for the net - protons shows a non - monotonic variation as a function of the beam energy .
this non - monotonic variation is characterized by the presence of a minimum in @xmath1 between @xmath0 = 11.5 and 19.6 gev and a change in the sign of @xmath1 twice between @xmath2 = 7.7 and 39 gev . at small impact parameters the product of the moments of net - proton distribution , kurtosis @xmath3 variance ( @xmath4 ) and skewness @xmath3 standard deviation ( @xmath5 )
are observed to be significantly below the corresponding measurements at large impact parameter collisions for @xmath2 = 19.6 and 27 gev .
the @xmath4 and @xmath5 values at these beam energies deviate from the expectations from poisson statistics and that from a hadron resonance gas model .
both these measurements have implications towards the understanding of the qcd phase structures , the first order phase transition and the critical point in the high baryonic chemical potential region of the phase diagram . .
And you have already written the first three sentences of the full article: the formation of a hot and dense medium of deconfined quarks and gluons ( qgp ) has been established in high energy heavy ion collisions at the relativistic heavy ion collider ( rhic ) facility at brookhaven national laboratory and the large hadron collider ( lhc ) facility at cern @xcite .
the transition from qgp to a hadron gas has been shown to be a cross over @xcite .
the focus of research in this field has now shifted towards two aspects , ( a ) characterizing the transport properties of qgp and ( b ) establishing the qcd phase structures at high baryonic chemical potential ( @xmath6 ) region of the qcd phase diagram ..
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a rigorous phenomenological analysis of the precision data from relativistic heavy - ion collisions and theoretical advances over 14 years has led to quantitative estimates for some of the transport properties of a strongly interacting de - confined state of quarks and gluons .
the estimated shear viscosity to entropy density ratio ( @xmath7 ) is found to reflect the inviscid liquid property of the qgp and has a value between ( 1 - 2)/4@xmath8 @xcite . that reflecting the stopping power or the opacity of qgp has been estimated by obtaining the square of the momentum transferred by the parton to the qgp per unity length ( @xmath9 ) and
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Suppose that you have an abstract for a scientific paper: several early universe scenarios predict a direction - dependent spectrum of primordial curvature perturbations .
this translates into the violation of the statistical isotropy of cosmic microwave background radiation .
previous searches for statistical anisotropy mainly focussed on a quadrupolar direction - dependence characterised by a _
single _ multipole vector and an overall amplitude @xmath0 .
generically , however , the quadrupole has a more complicated geometry described by _ two _ multipole vectors and @xmath0 .
this is the subject of the present work . in particular , we limit the amplitude @xmath0 for different shapes of the quadrupole by making use of planck 2015 maps . we also constrain certain inflationary scenarios which predict this kind of more general quadrupolar statistical anisotropy .
inr - th/2016 - 047 .
And you have already written the first three sentences of the full article: with the release of the cosmic microwave background ( cmb ) maps obtained with the planck satellite , a string of properties of primordial scalar perturbations has been established with unprecedented accuracy . in particular , possible deviations from gaussianity and adiabaticity are now subject to quite severe constraints , while exact scale - invariance of the primordial power spectrum is excluded at more than @xmath1 c.l .
these observations show no departure from the simplest idea of single scalar slow roll inflation , while narrowing the window for many alternative scenarios . along with gaussianity and adiabaticity ,
large - scale statistical isotropy ( si ) of the universe is a basic prediction of standard inflationary cosmology ..
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this stems from the spin-0 nature of the inflaton and the isotropy of the ( quasi)de sitter space - time @xcite resulting in the rotational invariance of the inflaton field s correlation functions ; together with the isotropy of the background metric during radiation- and matter - dominated stages , this implies the si of cmb temperature fluctuations @xmath2 .
in particular , this means that the variance @xmath3 is independent of the direction @xmath4 in the sky .
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Suppose that you have an abstract for a scientific paper: brown dwarfs may have such low masses because they are prematurely ejected from small unstable multiple systems , while the members are still actively building up their masses .
we demonstrate that this scenario is consistent with all currently existing observations of brown dwarfs , and propose further observational tests .
we review the status of the latest realistic numerical simulations of disintegrating small n clusters , which show that many of the ejected members end up with masses that are substellar , drifting away from their birth region with velocities rarely exceeding 2 km s@xmath0 . .
And you have already written the first three sentences of the full article: it is commonly assumed that brown dwarfs are formed the same way as stars , except under conditions that lead to stellar objects with very small masses , i.e. from clouds that are very small , very dense , and very cold .
however , with the growing realization that brown dwarfs may be as common as stars , it is becoming disturbing that such special physical conditions are not readily found in the molecular clouds of our galaxy ( although they may exist elsewhere , see elmegreen 1999 ) .
alternatively , lin et al ..
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( 1998 ) suggested that the encounter between two protostars with massive disks could fling out tidal filaments with lengths of about 1000 au , out of which a brown dwarf might form .
however , the fact that brown dwarfs are increasingly discovered also in loose t tauri associations like taurus , where such encounters should be extremely rare , suggests that this mechanism is unlikely to be a major source of brown dwarfs . taking another approach ,
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Suppose that you have an abstract for a scientific paper: the computation of the correction @xmath0 in the w - z mass correlation , derived from muon decay , is described at the two - loop level in the standard model .
technical aspects which become relevant at this level are studied , e.g. gauge - parameter independent mass renormalization , ghost - sector renormalization and the treatment of @xmath1 .
exact results for @xmath0 and the w mass prediction including @xmath2 corrections with fermion loops are presented and compared with previous results of a next - to - leading order expansion in the top - quark mass . .
And you have already written the first three sentences of the full article: the electroweak standard model ( sm ) , together with the theory of strong interactions ( quantum chromodynamics , qcd ) , provides a comprehensive description of experimental data with remarkable consistency . in order to further test the validity of the sm predictions and restrict its only missing parameter , the higgs boson mass
, precision measurements play a key role .
the analysis of precision observables is sensitive to quantum corrections in the theoretical predictions , which depend on all the parameters of the model . in this way.
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, the top - quark mass , @xmath3 , had been predicted in the region where it was experimentally found .
the constraints on the higgs mass , @xmath4 , are still rather weak since @xmath4 appears only logarithmically in the leading order sm predictions .
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Suppose that you have an abstract for a scientific paper: dynamic behaviors of the penetrated jet and the departure of the bubble of wrapping gas at the tip of the collapsing jet observed by use of a high - speed camera are included in this fluid dynamics video . .
And you have already written the first three sentences of the full article: we conduct a series of experiments with a special interest on a penetration process and instabilities arisen on a liquid jet impinged to a liquid of the same kind flowing in a channel .
the impinged jet penetrates into the flowing bath accompanying with entrainment of the ambient immiscible gas , which results in the impinged jet wrapped by the entrained gas as a sheath. this sheath formation enables the impinged jet to survive in the fluid in the channel without coalescing until the entrained - air sheath breaks down .
occasionally a cap of the entrained air is formed at the tip of the penetrated jet , and the jet elongates like a long balloon ..
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Suppose that you have an abstract for a scientific paper: inspiraling compact binaries are expected to be the strongest sources of gravitational waves for virgo , ligo and other laser interferometers .
we present the first computations of quasi - equilibrium sequences of compact binaries containing two strange quark stars ( which are currently considered as a possible alternative to neutron stars ) .
we study a precoalescing stage in the conformal flatness approximation of general relativity using a multidomain spectral method .
a hydrodynamical treatment is performed under the assumption that the flow is irrotational . .
And you have already written the first three sentences of the full article: one of the most important prediction of einstein theory of relativity is gravitational radiation . since the very precise measurement of the orbital decay in the binary pulsar b1913 + 16 system by hulse and taylor ,
the existence of gravitational waves ( gw ) has been indirectly proved and general relativity has passed another quite constraining test . due to
the emission of gw , binary neutron stars ( ns ) decrease their orbital separation and finally merge ..
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the evolution of a binary system can be separated into three phases : point - like inspiral where orbital separation is much larger than the ns radius , hydrodynamical inspiral where orbital separation is just a few times larger than the radius of the ns so that hydrodynamics play an important role , and merger in which the two stars coalesce dynamically .
the gw signal of the terminal phases ( the hydrodynamical phase or the merger phase ) of inspiraling binary can bring the information about the stellar structure .
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Suppose that you have an abstract for a scientific paper: . pleijel has proved that in the case of the laplacian on the square with neumann condition , the equality in the courant nodal theorem ( courant sharp situation ) can only be true for a finite number of eigenvalues .
we identify five courant sharp eigenvalues for the neumann laplacian in the square , and prove that there are no other cases . .
And you have already written the first three sentences of the full article: for an eigenfunction @xmath0 corresponding to the @xmath1-th eigenvalue @xmath2 ( counted with multiplicity ) of the laplace operator in a bounded regular domain @xmath3 , we denote by @xmath4 the number of nodal domains of @xmath0 .
a famous result by courant ( see @xcite ) states that @xmath5 .
if @xmath6 , then we say that the eigenpair @xmath7 ( or just the eigenvalue @xmath2 ) is courant sharp ..
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it is proved in @xcite that , for general planar domains , and with dirichlet or neumann boundary conditions , the courant sharp situation occurs for a finite number of eigenvalues only .
note that in the case of neumann the additional assumption that the boundary is piecewise analytic should be imposed due the use of a theorem by toth
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Suppose that you have an abstract for a scientific paper: the dependence of the transmission coefficient on the deformation , the collective rotation and excitation energy of the compound nucleus emitting light particles is introduced in the framework of weikopf s evaporation theory . the competition between fission and particle evaporation is treated by a langevin equation for the fission variable coupled to the emission process .
detailed calculations are presented on the decay of different gd and yb isotopes at an excitation energy of about 250 mev .
these calculations demonstrate the importance of the effects of nuclear deformation and of the initial spin distribution on the evaporation . .
And you have already written the first three sentences of the full article: the properties of excited nuclei in thermal equilibrium are of great physical interest .
we are interested in excitation energies below some ( 400500 ) mev , where we may still describe the nucleus as a system of neutrons and protons which interact by effective forces .
all the information on the physical state of hot nuclei is then to be obtained from a careful study of their decay by emission of neutrons , protons , and @xmath0particles and their decay by fission ..
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the emission of photons will be neglected , as we consider energies far above the thresholds for particle emission .
the basis of our approach @xcite is a description of the particle emission as a purely statistical process , as given by the weikopf theory @xcite , and the nuclear fission as a transport process @xcite .
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Suppose that you have an abstract for a scientific paper: we explore two possible models which might give rise to bright x - ray flares in grbs afterglows .
one is an external forward - reverse shock model , in which the shock parameters of forward / reverse shocks are taken to be quite different .
the other is a so called late internal shock model " , which requires a refreshed unsteady relativistic outflow generated after the prompt @xmath0ray emission . in the forward - reverse shock model , after the time @xmath1
at which the rs crosses the ejecta , the flux declines more slowly than @xmath2 , where @xmath3 denotes the observer s time and @xmath4 is the spectral index of the x - ray emission . in the late internal shock model " , decaying slopes much steeper than @xmath5 are possible
if the central engine shuts down after @xmath6 and the observed variability timescale of the x - ray flare is much shorter than @xmath7 .
the sharp decline of the x - ray flares detected in grb 011121 , xrf 050406 , grb 050502b , and grb 050730 rules out the external forward - reverse shock model directly and favors the late internal shock model " .
these x - ray flares could thus hint that the central engine operates again and a new unsteady relativistic outflow is generated just a few minutes after the intrinsic hard burst .
gamma rays : bursts@xmath8ism : jets and outflows radiation mechanisms : nonthermal@xmath8x - rays : general .
And you have already written the first three sentences of the full article: grb 011121 was simultaneously detected by _ bepposax _
grbm and wfc ( piro 2001 ) , and the fluence in the 2 - 700 kev range corresponds to an isotropic energy of @xmath9ergs at the redshift of @xmath10 ( infante et al .
this burst was born in a stellar wind ( price et al ..
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2002 ; greiner et al . 2003 ) and a supernova bump was detected in the late optical afterglow ( bloom et al . 2002 ; garnavich et al .
its very early x - ray light curve , which has not been published until quite recently , is characterized by the presence of two flares ( prio 2005 , hereafter p05 ) . in the first one , which is also the strongest of the two ,
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Suppose that you have an abstract for a scientific paper: the empirical scaling law , wherein the total photoabsorption cross section depends on the single variable @xmath0 , provides empirical evidence for saturation in the sense of @xmath1 for @xmath2 at fixed @xmath3 .
the total photoabsorption cross section is related to elastic diffraction in terms of a sum rule .
the excess of diffractive production over the elastic component is due to inelastic diffraction that contains the production of hadronic states of higher spins .
motivated by the diffractive mass spectrum , the generalized vector dominance / color dipole picture ( gvd / cdp ) is extended to successfully describe the dis data in the full region of @xmath4 , all @xmath5 , where the diffractive two - gluon - exchange mechanism dominates . in the present talk ,
i wish to concentrate on the relation between the total photoabsorption cross section , @xmath6 , at low @xmath7 and diffractive production , @xmath8 @xcite .
the experimental data @xcite on @xmath6 at @xmath4 and all @xmath5 , including photoproduction @xmath9 , lie on a single curve @xcite , _ ^
* p ( w^2 , q^2 ) = _ ^*p ( ( w^2 , q^2 ) ) , [ ( 1 ) ] if plotted against the low - x scaling variable ( w^2 , q^2 ) = , [ ( 2 ) ] where @xmath10 is a slowly increasing function of @xmath11 and @xmath12 .
compare fig . 1 for a plot of @xmath6 against @xmath13 .
the function @xmath14 may be represented , alternatively , by a power law or by a logarithm , ^2 ( w^2 ) = \ { .
[ ( 3 ) ] as a function of @xmath15 compared with the predictions from the gvd / cdp.,width=245 ] we refer to refs.@xcite for the numerical values of the fit parameters in @xmath14 . the empirical model - independent finding ( [ ( 1 ) ] )
is interpreted in the generalized vector dominance / color dipole picture ( gvd / cdp ) @xcite that rests on the generic structure of the two - gluon - exchange virtual - photon - forward - compton - scattering amplitude .
evaluation of this amplitude in the @xmath16 limit and transition to transverse position....
And you have already written the first three sentences of the full article: it is a pleasure to thank masaaki kuroda , bernd surrow and mikhael tentyukov for a fruitful collaboration on the subject matter of the present talk .
zeus 96/97 : s. chekanov et al .
, zeus collab ..
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, desy-01 - 014 , submitted to eur . phys .
j. c ; m. derrick et al .
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Suppose that you have an abstract for a scientific paper: this paper develops a simplified set of models describing asexual and sexual replication in unicellular diploid organisms .
the models assume organisms whose genomes consist of two chromosomes , where each chromosome is assumed to be functional if it is equal to some master sequence @xmath0 , and non - functional otherwise .
the first - order growth rate constant , or fitness , of an organism , is determined by whether it has zero , one , or two functional chromosomes in its genome .
we assume that an organism with no functional chromosomes has zero fitness . for a population replicating asexually
, a given cell replicates both of its chromosomes , and then the cell divides and splits its genetic material evenly between the two cells . for a population replicating sexually , a given cell first divides into two haploids , which enter a haploid pool . within the haploid pool , haploids fuse into diploids , which then divide via the normal mitotic process .
haploid fusion is modeled as a second - order rate process .
we review the previously studied case of selective mating , where it is assumed that only haploids with functional chromosomes can fuse , and also consider the case of random haploid fusion .
when the cost for sex is small , as measured by the ratio of the characteristic haploid fusion time to the characteristic growth time , we find that sexual replication with random haploid fusion leads to a greater mean fitness for the population than a purely asexual strategy
. however , independently of the cost for sex , we find that sexual replication with a selective mating strategy leads to a higher mean fitness than the random mating strategy .
this result is based on the assumption that a selective mating strategy does not have any additional time or energy costs over the random mating strategy , an assumption that is discussed in the paper .
the results of this paper are consistent with previous studies suggesting that sex is favored at intermediate mutation rates , for slowly....
And you have already written the first three sentences of the full article: the evolution and maintenance of sexual replication is one of the central questions in modern evolutionary biology @xcite .
the theories with the broadest acceptance are that sex allows for the removal of deleterious mutations from a population @xcite , or that sex allows for faster adaptation in dynamic environments @xcite .
as has been noted in previous studies @xcite , the various theories for the existence of sex are incomplete , in that they do not explain why some organisms are obligately sexual , while other organisms either alternate between asexual and sexual replication , or are asexual replicators with some ability for recombination with other organisms . in a recent set of papers @xcite , tannenbaum , fontanari , and lee studied the competition between asexual and sexual replicators in various regimes ..
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two of the models consider single - celled organisms , that replicate by dividing into haploids .
these haploids then enter a haploid pool , where they fuse with other haploids .
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Suppose that you have an abstract for a scientific paper: the westervelt equation is a model for the propagation of finite amplitude ultrasound .
the method of discrete exterior calculus can be used to solve this equation numerically .
a significant advantage of this method is that it can be used to find numerical solutions in the discrete space manifold and the time , and therefore is a generation of finite difference time domain method .
this algorithm has been implemented in c++
. 0.2 cm * keywords : * westervelt equation , laplacian operator , discrete exterior calculus , manifold , numerical simulation . 0.2 cm * msc(2010 ) : * 35j05 , 65m12 , 65m08 , 53a25 . .
And you have already written the first three sentences of the full article: the nonlinear effects are important in medical ultrasound and also plays a role in diagnostic program .
some of diagnostic ultrasound instruments have implemented harmonic imaging into their devices by receiving the harmonics in the reflected ultrasound caused by nonlinear distortion of the signal propagating through the biological tissue .
meanwhile , we should pay attention to observing hygienic limits of ultrasound exposition to avoid heating the unwanted tissue ..
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the ability to predict the effects of nonlinear ultrasound propagation therefore becomes important .
numerical simulations are currently the best means of making predictions of nonlinear ultrasound propagation .
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Suppose that you have an abstract for a scientific paper: we present spectroscopic observations of the central star clusters in ngc 5253 the aim of which is to search for wc stars . our observations show the presence of wolf - rayet ( wr ) stars not only of wn but also of wc subtype in two star forming regions corresponding to the maximum optical and uv emission .
the massive star population we derive is consistent with young bursts of @xmath0 3 and 4 myr .
the region of maximum optical emission is found to provide the dominant contribution of the ionizing flux as opposed to the less extinguished region of maximum uv brightness .
the presence of wr stars near the n - enriched regions found by walsh & roy ( 1987 , 1989 ) and kobulnicky et al .
( 1997 ) suggests they are a possible source of n. it is presently unclear whether or not our detection of wc stars is compatible with the normal observed he / o and c / o abundance ratios .
_ apj letter , in press ( received : 2 november 1996 , accepted : 13 march 1997 ) _
# 1#2@xmath1 2c16o@xmath2 .
And you have already written the first three sentences of the full article: we have initiated a systematic search program to find wolf - rayet ( wr ) stars of the carbon series ( wc subtypes ) in the so - called wr galaxies ( conti 1991 ) .
indeed , among the @xmath0 70 wr galaxies known today only few cases show the broad @xmath35808 emission originating from wc stars ( e.g. mrk 724 , ngc 4861 , ngc 4214 , he 2 - 10 , ngc 2363 ; cf .
references in meynet 1995 ) ..
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however , as meynet ( 1995 ) pointed out , a natural result of stellar evolution ( or our current knowledge of it ) is that one expects that in a large fraction of wr galaxies ( typically 30 % for metallicities @xmath4 ; cf .
schaerer & vacca 1996 ) the wr population should be dominated by stars of the wc subtype if star formation occurs on timescales short compared to the lifetimes of massive stars .
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Suppose that you have an abstract for a scientific paper: dimensionality is a major concern in analyzing large data sets .
some well known dimension reduction methods are for example principal component analysis ( pca ) , invariant coordinate selection ( ics ) , sliced inverse regression ( sir ) , sliced average variance estimate ( save ) , principal hessian directions ( phd ) and inverse regression estimator ( ire ) .
however , these methods are usually adequate of finding only certain types of structures or dependencies within the data .
this calls the need to combine information coming from several different dimension reduction methods .
we propose a generalization of the crone and crosby distance , a weighted distance that allows to combine subspaces of different dimensions .
some natural choices of weights are considered in detail .
based on the weighted distance metric we discuss the concept of averages of subspaces as well to combine various dimension reduction methods .
the performance of the weighted distances and the combining approach is illustrated via simulations .
keywords : dimension reduction ; distance ; metric ; principal component analysis ; projection pursuit ; subspace . .
And you have already written the first three sentences of the full article: dimension reduction plays an important role in high dimensional data analysis .
one then wishes to reduce the dimension of a @xmath0-variate random vector @xmath1 using a transformation @xmath2 where the transformation matrix @xmath3 is a @xmath4 matrix with linearly independent columns , @xmath5 .
the column vectors of @xmath3 then span the @xmath6-dimensional subspace of interest ..
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the transformation to the subspace can also be done using the corresponding @xmath7 orthogonal projector @xmath8 .
the transformation @xmath9 projects the observations to a linear @xmath6-variate subspace .
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Suppose that you have an abstract for a scientific paper: quantum chromodynamics ( qcd ) phase diagram is usually plotted as temperature ( @xmath0 ) versus the chemical potential associated with the conserved baryon number ( @xmath1 ) .
two fundamental properties of qcd , related to confinement and chiral symmetry , allows for two corresponding phase transitions when @xmath0 and @xmath1 are varied .
theoretically the phase diagram is explored through non - perturbative qcd calculations on lattice .
the energy scale for the phase diagram ( @xmath2 @xmath3 200 mev ) is such that it can be explored experimentally by colliding nuclei at varying beam energies in the laboratory . in this paper
we review some aspects of the qcd phase structure as explored through the experimental studies using high energy nuclear collisions . specifically , we discuss three observations related to the formation of a strongly coupled plasma of quarks and gluons in the collisions , experimental search for the qcd critical point on the phase diagram and freeze - out properties of the hadronic phase
. _ keywords _ : quark gluon plasma , strangeness enhancement , jet quenching , elliptic flow , chemical and kinetic freeze - out , qcd phase digram and qcd critical point . .
And you have already written the first three sentences of the full article: physical systems undergo phase transitions when external parameters such as the temperature ( @xmath0 ) or a chemical potential ( @xmath4 ) are changed .
a phase diagram provides intrinsic knowledge on the structure of the matter under study . in other words , it tells us how matter organizes itself under external conditions at a given degrees of freedom .
the theory of strong interactions , qcd , predicts that nuclear matter at high temperature and/or density makes a transition from a state where quarks and gluons are confined and chiral symmetry is broken to a state where quarks and gluons are de - confined and chiral symmetry is restored @xcite ..
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qcd has several conserved quantities : baryon number ( @xmath5 ) , electric charge ( @xmath6 ) , and strangeness ( @xmath7 ) .
each of these is associated with a chemical potential . as a result ,
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Suppose that you have an abstract for a scientific paper: in this paper , we present a theoretical study of a bose - einstein condensate of interacting bosons in a quartic trap in one , two , and three dimensions . using thomas - fermi approximation , suitably complemented by numerical solutions of the gross - pitaevskii equation
, we study the ground sate condensate density profiles , the chemical potential , the effects of cross - terms in the quartic potential , temporal evolution of various energy components of the condensate , and width oscillations of the condensate .
results obtained are compared with corresponding results for a bose condensate in a harmonic confinement . .
And you have already written the first three sentences of the full article: since the first experimental observation of bose - einstein ( be ) condensation@xcite in bose atom clouds in a harmonic trap , both experimental and theoretical studies of this phenomenon and various properties of the condensate has grown up to a fast expanding field of research @xcite .
while studies of bose condensation in a harmonic potential is of great interest , investigations of the be condensation of lattice - bosons and free - bosons in _ anharmonic _ potentials , in particular in a quartic potential , have received considerable attention in recent times@xcite ( see also the note in ref .
@xcite ) . all the previous works@xcite , except two@xcite , deals with _ lattice - bosons _ in anharmonic confinements ..
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the previous works on free - bosons in power law traps and quartic traps in three and lower dimensions@xcite dealt with the calculations of bose condensation temperature for _ non - interacting _ bosons in those environments . in this paper , we consider _ interacting _ bosons in a quartic potential .
the study of _ interacting _ bosons in a quartic potential may have important implications for fields ranging from chaotic dynamics to high energy physics@xcite .
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Suppose that you have an abstract for a scientific paper: in this paper we propose a novel definition of the bosonic spectral action using zeta function regularization , in order to address the issues of renormalizability and spectral dimensions .
we compare the zeta spectral action with the usual ( cutoff based ) spectral action and discuss its origin , predictive power , stressing the importance of the issue of the three dimensionful fundamental constants , namely the cosmological constant , the higgs vacuum expectation value , and the gravitational constant .
we emphasize the fundamental role of the neutrino majorana mass term for the structure of the bosonic action . iccub-14 - 068 + kcl - ph - th/2014 - 51 * spectral action with zeta function regularization * maxim a. kurkov@xmath0 , fedele lizzi@xmath1 , mairi sakellariadou@xmath2 , apimook watcharangkool@xmath2 + @xmath3_dipartimento di matematica e applicazioni renato caccioppoli " , + universit di napoli _ federico ii _
_ + @xmath4_infn , sezione di napoli _ + @xmath5_dipartimento di fisica , universit di napoli _ federico
ii _ _ + _ monte s. angelo , via cintia , 80126 napoli , italy _ + @xmath6 _ departament de estructura i constituents de la matria , + institut de cincies del cosmos , universitat de barcelona , + barcelona , catalonia , spain _
+ @xmath7 _ physics department , king s college london , university of london + strand , london wc2 2rls , u.k .
_ 2 cm .
And you have already written the first three sentences of the full article: the standard model of particle interactions is very successful , and the recent discovery of the higgs boson seals its validity . yet there are unanswered questions which on one side suggest to go `` beyond the standard model '' , perhaps connecting with a theory of quantum gravity , and on the other side beg for an `` explanation '' of the loose conceptual aspects , such as the hierarchy problem or the nature of symmetries . the spectral approach to noncommutative geometry @xcite provides a framework for the description of the standard model encoding it in a general view of geometry based on an algebraic description .
in particular , the action of a field theory is encoded in such a description , and one can construct a natural action for fermions and bosons based on the spectral properties of the ( generalized ) dirac operator .
such a _ spectral action _ has been introduced in ref ..
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@xcite and applied to the standard model in various forms ( for a recent review see ref .
this action is immediately applicable to the phenomenology and has been presently refined to confront itself with experimental results .
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Suppose that you have an abstract for a scientific paper: image compression has been a frequent topic of presentations at adass .
compression is often viewed as just a technique to fit more data into a smaller space .
rather , the packing of data its `` density '' affects every facet of local data handling , long distance data transport , and the end - to - end throughput of workflows . in short ,
compression is one aspect of proper data structuring .
for example , with fits tile compression the efficient representation of data is combined with an expressive logistical paradigm for its manipulation .
a deeper question remains . not just how best to represent the data , but which data to represent .
ccds are linear devices .
what does this mean ?
one thing it does not mean is that the analog - to - digital conversion of pixels must be stored using linear data numbers ( dn ) .
an alternative strategy of using non - linear representations is presented , with one motivation being to magnify the efficiency of numerical compression algorithms such as rice . .
And you have already written the first three sentences of the full article: the rice compression algorithm ( rice _ et al .
_ 1993 ) is particularly familiar to astronomers in combination with the fits tiled image convention ( white _ et al .
_ 2006 , seaman _.
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it has been informally paired in the past with non - linear data representations ( nieto - santisteban _
_ 1999 , nicula _
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Suppose that you have an abstract for a scientific paper: the lpn ( learning parity with noise ) problem has recently proved to be of great importance in cryptology .
a special and very useful case is the ring - lpn problem , which typically provides improved efficiency in the constructed cryptographic primitive .
we present a new algorithm for solving the ring - lpn problem in the case when the polynomial used is reducible .
it greatly outperforms previous algorithms for solving this problem . using the algorithm
, we can break the lapin authentication protocol for the proposed instance using a reducible polynomial , in about @xmath0 bit operations .
birthday attacks , fast walsh - hadamard transform , lapin , lpn , ring - lpn . .
And you have already written the first three sentences of the full article: cryptography is a field of cryptography inclined towards efficient cryptographic implementations , as a response to the demands when using highly constrained hardware in low - cost devices , such as passive rfid - tags and smart cards .
there are trade - offs to consider , e.g. , security , memory and performance .
different constructions appear in different ends in the trade - offs ; for instance , aes and stream ciphers can be implemented efficiently in hardware but do not offer _.
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provable security_. quite recently , a new trend arose in this area , building cryptographic primitives from problems in learning theory .
problems based on learning theory provide a complexity theoretical foundation , on which the security of the cryptosystem can be based upon .
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Suppose that you have an abstract for a scientific paper: we show how the magneto - phonon resonance , particularly pronounced in sp@xmath0 carbon allotropes , can be used as a tool to probe the band structure of multilayer graphene specimens . even when electronic excitations can not be directly observed , their coupling to the e@xmath1 phonon leads to pronounced oscillations of the phonon feature observed through raman scattering experiments with multiple periods and amplitudes detemined by the electronic excitation spectrum .
such experiment and analysis have been performed up to 28 t on an exfoliated 4-layer graphene specimen deposited on sio@xmath2 , and the observed oscillations correspond to the specific ab stacked 4-layer graphene electronic excitation spectrum . .
And you have already written the first three sentences of the full article: since the theoretical prediction of magneto - phonon resonance in graphene and bilayer graphene @xcite , the resonant interaction between inter - landau level electronic excitations and @xmath3-point optical phonon in graphene , this effect has been widely explored experimentally in neutral graphene - like systems such as multi layer epitaxial graphene on c - face sic @xcite , graphene like inclusions on the surface of bulk graphite @xcite , and in bulk graphite @xcite .
magneto - phonon resonance in these systems are pronounced because ( i ) they are gapless and low energy direct ( @xmath4 ) electronic excitations exist , and ( ii ) because of the kohn anomaly @xcite at the @xmath3 point of the phonon brillouin zone which makes phonon energies _ ultra sensitive _ to modifications of the electronic excitation spectrum .
such modifications can be achieved by tuning the fermi energy or by applying a magnetic field perpendicular to the plane of the quasi-2d crystal . performed in systems with a well - known electronic excitation spectrum ,.
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magneto - phonon resonance experiments provide precise information concerning the electron - phonon interaction through the amplitude of the observed oscillations of the energy and of the line width of the phonon feature observed in raman scattering experiments , as a function of the applied magnetic field . on the other hand , since electronic excitations which couple to the e@xmath1 optical phonons are well identified by symmetry arguments ( optical - like excitations characterized by a change of angular momentum @xmath5
@xcite , where @xmath6 is the landau level index ) , this effect can be used to determine the electronic excitation spectrum . the evolution of optical - like excitations , calculated in the frame of ref .
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Suppose that you have an abstract for a scientific paper: we describe the excited @xmath0 state of @xmath1c at 7.654 mev , often called the hoyle state , in terms of a local potential @xmath2be+@xmath3 cluster model .
we use a previously published prescription for the cluster - core potential to solve the schrdinger equation to obtain wave functions for this state , and also for higher angular momentum states of the same system .
we calculate energies , widths and charge radii for the resulting band of states , with particular emphasis on the recently discovered @xmath4 state .
we examine various choices of the global quantum number @xmath5 for the cluster - core relative motion , and find that @xmath6 leads to the most coherent description of the properties of the states and is consistent with recent experimental data on the @xmath7 state . .
And you have already written the first three sentences of the full article: when considering how carbon could be produced in stellar nucleosynthesis , hoyle @xcite famously predicted that the @xmath1c nucleus must have an excited @xmath0 state in the vicinity of the 3-@xmath3 breakup threshold .
such a state was duly found @xcite in short order on the basis of hoyle s suggestion .
its existence was essential for @xmath1c to be produced at an adequate rate to open up the pathways to the synthesis of still heavier nuclei @xcite ..
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not only had this state escaped both experimental detection and theoretical prediction up to that point , but it has continued to pose severe challenges to nuclear structure models ever since .
the shell model struggles to describe any low - lying excited @xmath0 states in p - shell and sd - shell nuclei . to this day
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Suppose that you have an abstract for a scientific paper: cloud service providers offer various facilities to their clients .
the clients with limited resources opt for some of these facilities
. they can outsource their bulk data to the cloud server .
the cloud server maintains these data in lieu of monetary benefits .
however , a malicious cloud server might delete some of these data to save some space and offer this extra amount of storage to another client .
therefore , the client might not retrieve her file ( or some portions of it ) as often as needed .
proofs of retrievability ( por ) provide an assurance to the client that the server is actually storing all of her data appropriately and they can be retrieved at any point of time . in a dynamic por scheme , the client can update her data after she uploads them to the cloud server .
moreover , in publicly verifiable por schemes , the client can delegate her auditing task to some third party specialized for this purpose . in this work ,
we design a publicly verifiable dynamic por scheme that is more efficient ( in terms of bandwidth required between the client and the server ) than the `` state - of - the - art '' publicly verifiable dynamic por scheme .
we also analyze security and performance of our scheme . .
And you have already written the first three sentences of the full article: in the age of cloud computing , cloud servers with adequate resources help their clients by performing huge amount of computation or by storing large amount of data ( say , in the order of terabytes ) on their behalf . in this
setting , a client only has to download the result of the computation or has to read ( or update ) the required portion of the outsourced data .
several storage service providers like amazon simple storage service ( s3 ) , dropbox , google drive and microsoft azure provide storage outsourcing facility to their clients ( data owners ).
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. however , a cloud storage server can be malicious and delete some ( less frequently accessed ) part of the client s data in order to save space .
secure cloud storage protocols ( two - party protocols between the client and the server ) provide a cryptographic solution to this problem by ensuring that the client s data are stored untampered in the cloud server . in a secure cloud storage scheme , a client can remotely check the integrity of her data file outsourced to the cloud server . a possible way to do this
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Suppose that you have an abstract for a scientific paper: we study the phase diagram of one - dimensional quantum ferrimagnets by using a numerical exact diagonalization of a finite size system along with a field - theoretical non - linear @xmath0 model of the quantum ferrimagnets at zero temperature and its effective description in the presence of the external magnetic field in terms of the quantum xy - model .
the low- and the high - field phases correspond respectively to the classical nel and the fully polarized ferromagnetic states where in the intermediate magnetic field ( @xmath1 ) , it is an xxz+h model with easy plane anisotropy , which possess the spiral ( superfluid ) states that carry the dissipationless spin - supercurrent .
we derive the critical exponents , and then will study the stability of the xy spiral state against these spin - supercurrents and the hard axis fluctuations .
we will show a first order phase transition from the easy plane spiral state to a saturated ferromagnetic state occurs at @xmath2 if the spin - supercurrent reaches to its critical value . 2 .
And you have already written the first three sentences of the full article: recently , antiferromagnetically coupled mixed - spin chains with an alternating array of two kinds of spins have attracted interest among researchers @xcite .
integrable models of mixed - spin antiferromagnetic chains were constructed by de vega and woynarovich @xcite and the simplest case of such chains with spins @xmath3 and @xmath4 were subsequently studied @xcite .
since these integrable models are exactly solvable , they are very useful for studying ( quantum ) statistical mechanical properties . although ferrimagnetic spin chains exhibit both ferromagnetic and antiferromagnetic features , they show some peculiar , and sometimes surprising , features uncharacteristic of either the ferromagnet or the antiferromagnet .
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an example being the existence of gapless excitations with very small correlation length .
it is important to understand these features more clearly . in this paper
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Suppose that you have an abstract for a scientific paper: transiting planet discoveries have yielded a plethora of information regarding the internal structure and atmospheres of extra - solar planets .
these discoveries have been restricted to the low - periastron distance regime due to the bias inherent in the geometric transit probability .
monitoring known radial velocity planets at predicted transit times is a proven method of detecting transits , and presents an avenue through which to explore the mass - radius relationship of exoplanets in new regions of period / periastron space . here
we describe transit window calculations for known radial velocity planets , techniques for refining their transit ephemerides , target selection criteria , and observational methods for obtaining maximum coverage of transit windows .
these methods are currently being implemented by the transit ephemeris refinement and monitoring survey ( terms ) . .
And you have already written the first three sentences of the full article: planet formation theories thus far extract much of their information from the known transiting exoplanets which are largely in the short - period regime .
this is because transit surveys which have provided the bulk of the transiting planet discoveries , such as superwasp @xcite and hatnet @xcite , are biased towards this region .
the two planets which contribute to the sample of intermediate to long - period transiting exoplanets are : hd 17156b @xcite and hd 80606b @xcite , the latter of which exhibits both a primary transit and secondary eclipse . in both of these cases ,.
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the detection was largely due to the inflated transit / eclipse probability caused by their extreme orbital eccentricities .
both of these were observed to transit through predictions based upon their radial velocity data .
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Suppose that you have an abstract for a scientific paper: we present abundance ratios for 23 elements with respect to fe in a sample of stars with a wide range in luminosity from luminous giants to stars near the turnoff in a globular cluster .
our sample of 25 stars in m71 includes 10 giant stars more luminous than the red horizontal branch ( rhb ) , 3 hb stars , 9 giant stars less luminous than the rhb , and 3 stars near the turnoff .
the analyzed spectra , obtained with hires at the keck observatory , are of high dispersion ( r=@xmath0=35,000 ) .
we find that the neutron capture , the iron peak and the @xmath1element abundance ratios show no trend with @xmath2 , and low scatter around the mean between the top of the rgb and near the main sequence turnoff .
the @xmath1elements mg , ca , si and ti are overabundant relative to fe . the anti - correlation between o and na abundances , observed in other metal poor globular clusters , is detected in our sample and extends to the main sequence . a statistically significant correlation between al and na abundances
is observed among the m71 stars in our sample , extending to @xmath3 , fainter than the luminosity of the rgb bump in m5 .
lithium is varying , as expected , and zr may be varying from star to star as well .
m71 appears to have abundance ratios very similar to m5 whose bright giants were studied by @xcite , but seems to have a smaller amplitude of star - to - star variations at a given luminosity , as might be expected from its higher metallicity .
both extremely o poor , na rich stars and extremely o rich , na poor stars such as are observed in m5 and in m13 are not present in our sample of m71 stars .
the results of our abundance analysis of 25 stars in m71 provide sufficient evidence of abundance variations at unexpectedly low luminosities to rule out the mixing scenario . either alone or ,
even more powerfully , combined with other recent studies of c and n abundances in m71 stars , the existence of such abundance variations can not be reproduced within the context of our current....
And you have already written the first three sentences of the full article: abundance determinations of stars in galactic globular clusters can provide valuable information about important astrophysical processes such as stellar evolution , stellar structure , galactic chemical evolution and the formation of the milky way .
surface stellar abundances of c , n , o , and often na , mg , and al are found to be variable among red giants within a globular cluster .
the physical process responsible for these star - to - star element variations is still uncertain ( see the reviews of kraft 1994 and pinsonneault 1997 , as well as cohen _.
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et al . _
2001 , paper i ) . in order to study the origin of the star - to - star abundance variations
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Suppose that you have an abstract for a scientific paper: the decuplet baryons , @xmath0 , @xmath1 , @xmath2 and @xmath3 , are studied in nuclear matter by using the in - medium qcd sum rules . by fixing the three momentum of the particles under consideration at the rest frame of the medium ,
the negative energy contributions are removed .
it is obtained that the parameters of the @xmath0 baryon are more affected by the medium against the @xmath3 state , containing three strange quarks , whose mass and residue do not affected by the medium , considerably .
we also find the vector and scalar self energies of these baryons in nuclear matter . by the recent progresses at @xmath4anda experiment at fair and nica facility it may be possible to study the in - medium properties of such states even the multi - strange @xmath2 and @xmath3 systems in near future . .
And you have already written the first three sentences of the full article: the investigations of the properties of hadrons under extreme conditions have been in the focus of much attention for many years .
such investigations are very important in the study of the internal structure of the dense astrophysical objects like neutron stars .
the formation of neutron stars is influenced by all four known fundamental interactions ..
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hence , understanding of their nature can help us in the course of unification of all fundamental forces within a common theoretical framework , which is one of the biggest challenges for physics .
the recent observation of massive neutron stars with roughly twice the solar mass @xcite has stimulated the focuses on the equation of state of the dense nuclear matter ( see for instance @xcite ) .
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Suppose that you have an abstract for a scientific paper: we show that a family of quantum authentication protocols introduced in [ barnum et al . ,
focs 2002 ] can be used to construct a secure quantum channel and additionally recycle all of the secret key if the message is successfully authenticated , and recycle part of the key if tampering is detected .
we give a full security proof that constructs the secure channel given only insecure noisy channels and a shared secret key .
we also prove that the number of recycled key bits is optimal for this family of protocols , i.e. , there exists an adversarial strategy to obtain all non - recycled bits .
previous works recycled less key and only gave partial security proofs , since they did not consider all possible distinguishers ( environments ) that may be used to distinguish the real setting from the ideal secure quantum channel . .
And you have already written the first three sentences of the full article: a one - time pad can famously be used only once @xcite , i.e. , a secret key as long as the message is needed to encrypt it with information / theoretic security .
but this does not hold anymore if the honest players can use quantum technologies to communicate .
a quantum key distribution ( qkd ) protocol @xcite allows players to expand an initial short secret key , and thus encrypt messages that are longer than the length of the original key . instead of first expanding a key , and then using it for encryption , one can also swap the order if the initial key is long enough : one first encrypts a message , then recycles the key ..
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this is possible due to the same physical principles as qkd : quantum states can not be cloned , so if the receiver holds the exact cipher that was sent , the adversary can not have a copy , and thus does not have any information about the key either , so it may be reused .
this requires the receiver to verify the authenticity of the message received , and if this process fails , a net key loss occurs the same happens in qkd : if an adversary tampers with the communication , the players have to abort and also lose some of the initial secret key .
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Suppose that you have an abstract for a scientific paper: data from the pamela satellite experiment were used to measure the geomagnetic cutoff for high - energy ( @xmath0 80 mev ) protons during the solar particle events on 2006 december 13 and 14 .
the variations of the cutoff latitude as a function of rigidity were studied on relatively short timescales , corresponding to single spacecraft orbits ( about 94 minutes ) . estimated
cutoff values were cross - checked with those obtained by means of a trajectory tracing approach based on dynamical empirical modeling of the earth s magnetosphere .
we find significant variations in the cutoff latitude , with a maximum suppression of about 6 deg for @xmath180 mev protons during the main phase of the storm .
the observed reduction in the geomagnetic shielding and its temporal evolution were compared with the changes in the magnetosphere configuration , investigating the role of imf , solar wind and geomagnetic ( kp , dst and sym - h indexes ) variables and their correlation with pamela cutoff results . .
And you have already written the first three sentences of the full article: solar energetic particle ( sep ) events are major space weather phenomena associated with explosive processes occurring in the solar atmosphere , such solar flares and coronal mass ejections ( cmes ) .
seps can produce hazardous effects to manned and robotic flight missions in the near - earth space environment , and influence the atmospheric chemistry and dynamics .
large sep events can strongly perturb the earth s magnetic field , inducing geomagnetic storms and modifying the cosmic - ray ( cr ) access to the inner magnetosphere ..
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the consequent reduction in the geomagnetic shielding can significantly increase the potential radiation exposure compared with geomagnetically quiet times .
estimates of geomagnetic cutoffs have been provided by satellite observations and theoretical calculations @xcite mainly based on tracing particles through models of the earth s magnetic field @xcite . in this work we present pamela s measurements of the variability of the geomagnetic cutoff during the sep events on 2006 december 13 and 14 , with the focus on the strong magnetic storm on december 14 and 15 .
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Suppose that you have an abstract for a scientific paper: recent results of the hectic research activity about gamma ray bursts will be reviewed , with emphasis about the emission processes at the origin of the observed @xmath0rays .
the conventional synchrotron shock scenario is found to have problems , due to the very short cooling times of the emitting electrons , which implies a predicted spectrum , @xmath1 , much steeper than what is observed .
it is therefore compelling to look for alternative emission processes , such as quasi thermal comptonization , implying the presence of mildly or sub relativistic electrons , producing , through multiple compton scatterings , a spectrum @xmath2 ending with a wien peak where photons and electron energies balance .
the afterglow light , instead , can be indeed due to synchrotron radiation , and a confirmation of this is the recently detected optical linear polarization of the afterglow of grb 990510 .
some consequences of this discovery will be outlined . a quantum leap in our understanding of the physics of gamma
ray bursts is expected to come with swift , a nasa midex dedicated satellite .
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And you have already written the first three sentences of the full article: after 30 years since their detection by the vela satellites , we just now start to understand the physics of gamma ray bursts ( grb ) .
this has been made possible by the precise location of the wide field camera ( wfc ) of @xmath3sax , which allowed the detection of their x ray afterglow emission ( costa et al .
1997 ) and the optical follow up observations , leading to the discovery that they are cosmological sources ( van paradijs et al . 1997 ) ..
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the huge energy and power releases required by their cosmological distances support the fireball scenario ( cavallo & rees 1978 ; rees & mszros 1992 ; mszros & rees 1993 ) , even if we do not know yet which kind of progenitor makes the grb phenomenon .
the most accepted picture for the burst and afterglow emission is the internal / external shock scenario ( rees & mszros 1992 ; rees & mszros 1994 ; sari & piran 1997 ) . according to this scenario , the burst emission is due to collisions of pairs of relativistic shells ( internal shocks ) , while the afterglow is generated by the collisionless shocks produced by shells interacting with the interstellar medium ( external shocks ) .
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Suppose that you have an abstract for a scientific paper: we present a systematic theory - motivated study of the thermodynamic stability condition as an explanation for the observed accretion disk wind signatures in different states of low mass black hole binaries ( bhb ) .
the variability in observed ions is conventionally explained either by variations in the driving mechanisms or the changes in the ionizing flux or due to density effects , whilst thermodynamic stability considerations have been largely ignored .
it would appear that the observability of particular ions in different bhb states can be accounted for through simple thermodynamic considerations in the static limit .
our calculations predict that in the disk dominated soft thermal and intermediate states , the wind should be thermodynamically stable and hence observable . on the other hand , in the powerlaw dominated spectrally hard state the wind is found to be thermodynamically unstable for a certain range of @xmath0 . in the spectrally hard state , a large number of the he - like and h - like ions ( including e.g. fe xxv , ar xviii and s xv have peak ion fractions in the unstable ionization parameter ( @xmath1 ) range , making these ions undetectable .
our theoretical predictions have clear corroboration in the literature reporting differences in wind ion observability as the bhbs transition through the accretion states @xcite . while this effect may not be the only one responsible for the observed gradient in the wind properties as a function of the accretion state in bhbs , it is clear that its inclusion in the calculations is crucial to understanding the link between the environment of the compact object and its accretion processes .
physical data and processes - accretion , accretion discs , black hole physics , sources as a function of wavelength - x - rays : binaries , stars - ( stars : ) binaries : spectroscopic , stars : winds , outflows .
And you have already written the first three sentences of the full article: most stellar mass black hole binaries ( bhbs ) show common behaviour patterns centered around a few states of accretion .
the different accretion states are signified by different spectral energy distributions ( among other things ) having varying degree of contribution from the accretion disk and the non - thermal powerlaw components .
in addition , since _.
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chandra _ and xmm - newton , there has been increased interest in winds from the accretion disk , as a result of detections of blueshifted absorption lines of varying velocities and temperatures , seen in high resolution x - ray spectra . in order to get a consolidated picture of these systems ,
it is necessary to understand the relation between the accretion states of the bhbs and the properties of the accretion disk winds .
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Suppose that you have an abstract for a scientific paper: the energies of different angular momentum states of a heavy - light meson were measured on a lattice in @xcite . we have now continued this study using several different lattices , quenched and unquenched , that have different physical lattice sizes , clover coefficients , hopping parameters and quark gluon couplings .
the heavy quark is taken to be infinitely heavy , whereas the light quark mass is approximately that of the strange quark . by interpolating in the heavy and light quark masses
we can thus compare the lattice results with the @xmath0 meson .
most interesting is the lowest p - wave @xmath0 state , since it is possible that it lies below the @xmath1 threshold and hence is very narrow .
unfortunately , there are no experimental results on p - wave @xmath0 mesons available at present .
in addition to the energy spectrum , we measured earlier also vector ( charge ) and scalar ( matter ) radial distributions of the light quark in the s - wave states of a heavy - light meson on a lattice @xcite .
now we are extending the study of radial distributions to p - wave states . .
And you have already written the first three sentences of the full article: for simplicity we consider a system that consists of one infinitely heavy quark ( or anti - quark ) and one light anti - quark ( quark ) .
the basic quantity for evaluating the energies of this heavy - light system on a lattice is the 2-point correlation function @xmath2 see fig .
[ fig_c2c3 ] a ) ..
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it is defined as @xmath3 where @xmath4 is the heavy quark propagator and @xmath5 the light anti - quark propagator .
@xmath6 is a linear combination of products of gauge links at time @xmath7 along paths @xmath8 and @xmath9 defines the spin structure of the operator . the @xmath10 means the average over the whole lattice .
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Suppose that you have an abstract for a scientific paper: we analyze diffusion equations in strongly coupled coulomb mixtures of ions in dense stellar matter . strong coupling of ions in the presence of gravitational forces and electric fields ( induced by plasma polarization in the presence of gravity ) produces a specific diffusion current which can separate ions with the same @xmath0 ( mass to charge number ) ratios but different @xmath1 .
this coulomb separation of ions can be important for the evolution of white dwarfs and neutron stars . .
And you have already written the first three sentences of the full article: in this letter we consider diffusion in a multicomponent plasma of ions in dense stellar matter .
this diffusion can greatly affect the composition of matter particularly in cores of white dwarfs and envelopes of neutron stars .
it produces redistribution of ions ( heavier ions move to the star s center ) and extra energy release that reheats the star and affects its thermal evolution . for example , we can mention gravitational settling of @xmath2ne in carbon - oxygen ( @xmath3c@xmath4o ) cores of white dwarfs ( see , e.g. , refs.@xcite)which is thought to reheat old white dwarfs and helps explain observational data ..
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diffusion of ions affects also chemical evolution and nuclear burning in envelopes of neutron stars ( e.g. , refs .
transport properties are important also in dusty plasmas with their numerous applications ( e.g. , ref.@xcite ) .
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Suppose that you have an abstract for a scientific paper: we review selected measurements of the galaxy luminosity function including the global field , the local group , the local sphere , nearby clusters ( virgo , coma and fornax ) and clusters in general .
we conclude that the overall cluster luminosity function is consistent with the global luminosity function over the magnitude range in common ( @xmath0 ) .
we find that only in the core regions of clusters ( @xmath1 kpc ) does the overall form of the luminosity function show significant variation .
however when the luminosity function is subdivided by spectral type some further variations are seen .
we argue that these results imply : substantial late infall , efficient star - formation suppression , and the confinement of mass - changing evolutionary processes to the core regions only . .
And you have already written the first three sentences of the full article: the schechter luminosity function @xcite has been the standard expression for representing the space density of galaxies over the past 25 years .
it has strengths and weaknesses .
the strengths are : its connection to the fundamental theory of the growth of initial mass perturbations @xcite , its overall simplicity ( with three free parameters : the characteristic luminosity @xmath2 ; the normalisation @xmath3 ; and the faint - end parameter @xmath4 ) , and its simple analytical connection to the luminosity - density ( and ultimately via a mass - to - light ratio to the galaxian matter - densities ) ..
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its weaknesses are : the correlation of the three parameters , the critical dependence of all three parameters upon the `` turn - over '' region , and its inability to reflect deviations of the space - density from a simple power - law at faint luminosities . over the past two decades
numerous attempts have been made to constrain the three defining schechter function parameters in both field and cluster environments producing a range of conclusions from a ubiquitous luminosity function to strong environmental dependencies .
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Suppose that you have an abstract for a scientific paper: we analyze the spatial correlation structure of the spin density of an electron gas in the vicinity of an antiferromagnetically - coupled kondo impurity .
our analysis extends to the regime of spin - anisotropic couplings , where there are no quantitative results for spatial correlations in the literature .
we use an original and numerically exact method , based on a systematic coherent - state expansion of the ground state of the underlying spin - boson hamiltonian .
it has not yet been applied to the computation of observables that are specific to the fermionic kondo model .
we also present an important technical improvement to the method , that obviates the need to discretize modes of the fermi sea , and allows one to tackle the problem in the thermodynamic limit . as a result , one can obtain excellent spatial resolution over arbitrary length scales , for a relatively low computational cost , a feature that gives the method an advantage over popular techniques such as the numerical and density - matrix renormalization groups .
we find that the anisotropic kondo model shows rich universal scaling behavior in the spatial structure of the entanglement cloud .
first , su(2 ) spin - symmetry is dynamically restored in a finite domain in parameter space in vicinity of the isotropic line , as expected from poor man s scaling .
more surprisingly , we are able to obtain in closed analytical form a set of different , yet universal , scaling curves for strong exchange asymmetry , which are parametrized by the longitudinal exchange coupling . deep inside the cloud ,
i.e. for distances smaller than the kondo length , the correlation between the electron spin density and the impurity spin oscillates between ferromagnetic and antiferromagnetic values at the scale of the fermi wavelength , an effect that is drastically enhanced at strongly anisotropic couplings . our results also provide further numerical checks and alternative analytical approximations for the kondo overlaps that were recently computed....
And you have already written the first three sentences of the full article: the spin @xmath0 kondo model describes a localized magnetic moment interacting with an electron gas , via an antiferromagnetic exchange coupling.@xcite despite a long history , and even an exact solution , it has not yet surrendered all its secrets .
it is well established that the ground state is a spin singlet in which the impurity spin is quenched by the electron gas , and the spatial region where the electron gas is correlated with the impurity is referred to as the kondo screening cloud.@xcite even for an isotropic system , its precise spatial profile is not known analytically , except asymptotically,@xcite and it is only in the past few years that it has been calculated numerically.@xcite despite wide - ranging proposals,@xcite it has eluded direct measurement , partly because of the difficulty in measuring spin correlations . in the isotropic case ,
the screening cloud is characterized by the ground state correlation function @xmath1 where @xmath2 is the impurity spin operator , and @xmath3 is the electron spin density at @xmath4 ..
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when the kondo temperature is much lower than the fermi energy , the screening cloud can be decomposed into a forward scattering contribution @xmath5 and a backscattering contribution @xmath6 , so that @xmath7 , where the two functions @xmath5 and @xmath6 vary slowly on the scale of the fermi wavelength @xmath8 . in the scaling regime and for spin - isotropic kondo exchange ,
the profile of the screening cloud displays a universal line shape,@xcite which is dependent on the value of kondo coupling @xmath9 only through an emergent length @xmath10 that is inversely proportional to the kondo temperature.@xcite to be specific , if @xmath11 and @xmath12 , with @xmath13 , are correlation functions corresponding to different values @xmath9 and @xmath14 of the kondo coupling , and @xmath10 and @xmath15 are the corresponding kondo lengths , then @xmath16 for all @xmath17 . recently , we have realized that it may be possible to measure the longitudinal forward scattering ( @xmath18 ) component of the screening cloud ( a precise definition is given below ) in a chain of tunnel - coupled superconducting islands.@xcite it turns out that the hamiltonian describing the charge and phase degrees of freedom in this system is equivalent to the _ spin - anisotropic _ kondo model in one dimension,@xcite described by two coupling constants : the @xmath19-components of the impurity and electron spins couple with a strength @xmath20 , while the components perpendicular to the @xmath19-axis couple with a different strength @xmath21 .
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Suppose that you have an abstract for a scientific paper: procedure and results of computations of stellar model atmospheres and spectral energy distributions are discussed .
model atmospheres of some chemically peculiar stars are computed taking into account detailed information about their abundances : r crb - like stars of teff @xmath0 7000 k , sakurai s object ( v4334 sgr ) of 4000 @xmath1 t@xmath2 @xmath1 7000 k przybylski s star of teff @xmath0 6500 k. we show that our self - consistent approach provides a unique possibility to investigate the temporal changes of physical parameters of chemically peculiar stars . some issues of computation of model atmospheres of m and c - giants are also considered . .
And you have already written the first three sentences of the full article: in many aspects , the existence of the irregular hydrogen - deficient ( hd ) variables remains puzzling so far .
r crb is the most known member of the post - agb group .
sakurai s object ( so , v4334 sge ) provides another , extreme case of stellar evolution ..
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it has been firmly established that the most abundant elements in atmospheres of r crb - like stars are helium and carbon .
determination of abundances in their atmospheres is possible only in the frame of self - consistent approach ( asplund et al .
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Suppose that you have an abstract for a scientific paper: using the `` break - junction '' technique we prepared and studied superconductor - constriction - superconductor nanocontacts in polycrystalline samples of fe - based superconductors ceo@xmath0f@xmath1feas ( ce-1111 ; @xmath2k ) , lao@xmath3f@xmath4feas ( la-1111 ; @xmath5k ) , and fese ( @xmath6k ) .
we detected two subharmonic gap structures related with multiple andreev reflections , indicating the presence of two superconducting gaps with the bcs - ratios @xmath7 and @xmath8 , respectively .
temperature dependences of the two gaps @xmath9 in fese indicate a @xmath10-space proximity effect between two superconducting condensates . for the studied iron - based superconductors we found a linear relation between the gap @xmath11 and magnetic resonance energy , @xmath12 .
example.eps gsave newpath 20 20 moveto 20 220 lineto 220 220 lineto 220 20 lineto closepath 2 setlinewidth gsave .4 setgray fill grestore stroke grestore .
And you have already written the first three sentences of the full article: andreev spectroscopy @xcite is a powerful instrument to measure superconducting gap in a wide temperature range , up to @xmath13 @xcite .
a number of such measurements have been performed earlier with oxypnictides of the rfeaso@xmath14f@xmath15 family and with fese @xcite . here
we present systematic studies of the current - voltage characteristics ( cvcs ) and dynamic conductance @xmath16 for superconductor - constriction - superconductor ( scs ) contacts in ce-1111 , la-1111 and fese . using the intrinsic multiple andreev reflections effect ( imare ) spectroscopy , we measured the two superconducting gap values in all three fe - based materials and determined temperature dependences of the two gaps for fese ..
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the compounds under study belong to the class of iron - based superconductors discovered in 2008 @xcite .
these materials are characterized by a layered crystal structure ; their electron energy spectrum in the normal state contains electron and hole quasi - two - dimensional fermi surface sheets , where two superconducting condensates are supposed to be formed at @xmath17 @xcite .
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Suppose that you have an abstract for a scientific paper: the gas at the surfaces of molecular clouds in galaxies is heated and dissociated by photons from young stars both near and far .
resulting from the dissociation of molecular hydrogen emits hyperfine line emission at @xmath0 cm , and warmed co emits dipole rotational lines such as the @xmath1 mm line of co(10 ) .
we use previously developed models for photodissociation regions ( pdrs ) to compute the intensities of these and co(10 ) lines as a function of the total volume density @xmath2 in the cloud and the far ultraviolet flux @xmath3 incident upon it and present the results in units familiar to observers .
the intensities of these two lines behave differently with changing physical conditions in the pdr , and , taken together , the two lines can provide a ground based radio astronomy diagnostic for determining @xmath2 and @xmath3 separately in distant molecular clouds .
this diagnostic is particularly useful in the range @xmath3 @xmath4 , 10 @xmath5 , which applies to a large fraction of the volume of the interstellar medium in galaxies . if the molecular cloud is located near discrete sources of far uv ( fuv ) emission , the pdr
generated and co(10 ) emission on the cloud surface can be more easily identified , appearing as layered `` blankets '' or `` blisters '' on the side of the cloud nearest to the fuv source .
as an illustration , we consider the galactic object g216 -2.5 , i.e. `` maddalena s cloud '' , which has been previously identified as a large pdr in the galaxy .
we determine that this cloud has @xmath6 and @xmath3 @xmath7 , consistent with other data . .
And you have already written the first three sentences of the full article: the interstellar medium ( ism ) in galaxies is excited , dissociated , and ionized by far - ultraviolet ( fuv ) photons produced by young o and b stars .
atomic gas in the ism recombines into molecular form mainly through the catalytic action of dust grain surfaces . in particular , hydrogen nuclei in the ism cycle
repeatedly from the molecular ( ) to the atomic ( ) phase and back again , at rates depending on the incident fuv flux @xmath3 , the total volume density @xmath2 of the gas , and the dust - to - gas ratio @xmath8 ..
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regions in the ism where the physics is dominated by fuv photons are called photodissociation regions ( pdrs ) .
the surfaces of giant molecular clouds ( gmcs ) are important ( and ubiquitous ) examples of pdrs in galaxies .
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Suppose that you have an abstract for a scientific paper: in the context of hrushovski constructions we take a language @xmath0 with a ternary relation @xmath1 and consider the theory of the generic models @xmath2 of the class of finite @xmath3-structures equipped with predimension functions @xmath4 for @xmath5\cap\mathbb{q } $ ] .
the theory of generic structures of non - ac smooth classes have been investigated from different points of view , including decidability and their power in interpreting known structures and theories . for a rational @xmath5 , $ ]
first we prove that the theory of @xmath6 admits a quantifier elimination down to a meaningful class of formulas , called _ closure formulas _ ; and on the other hand we prove that @xmath7 does not have the finite model property . .
And you have already written the first three sentences of the full article: our main contribution in this paper is to further investigate the model theory of non - algebraic generic structures . in a language @xmath0 with a ternary relation , for each @xmath5 $ ] one can associate to the class of finite @xmath0-structures some certain function @xmath4 called a _ predimension _ ( ) . in the present work we mainly focus on understanding particular _ generic _ structures ( ) , @xmath6 which were introduced by hrushovski in @xcite and were later studied by various authors in @xcite , , and . for a rational @xmath8
it has been proved by evans and wong that all finite graphs are interpretable in @xmath9 and as a consequence , @xmath10 has the strict order property and is undecidable .
later , brody and laskowski gave another source of undecidability for @xmath11 by interpreting robinson arithmetic in a subtheory of @xmath12 these results suggest that @xmath10 should be assumed to be quite wild " ..
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however , the starting point for investigating theory of generic structures is to determine whether the type of tuples can be fully determined in terms of their corresponding closures .
this happens in particular within the theory of tame " generic structures , where the type of a tuple is given completely by ( boolean combinations of ) certain @xmath13-formulas which indicate the existence of certain diagrams in the closure of that specific tuple .
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Suppose that you have an abstract for a scientific paper: the explore project is a series of searches for transiting extrasolar planets using large - format mosaic ccd cameras on 4-m class telescopes .
radial velocity follow - up is done on transiting planet candidates with 810 m class telescopes .
we present a summary of transit candidates from the explore project for which we have radial velocity data .
# 1_#1 _ # 1_#1 _ = # 1 1.25 in .125 in .25 in .
And you have already written the first three sentences of the full article: the explore ( extrasolar planet occultation research ) project is a series of searches for transiting extrasolar planets orbiting galactic plane stars using 4-m class telescopes . as an integral part of the search strategy , radial velocity ( rv )
follow - up observations for mass confirmation are done on 810 m class telescopes . in june 2001
, we used the ctio 4-m telescope for 11 nights ( 6 clear ) to observe the explore i field , located at @xmath0 ( malln - ornelas et al.2002 ) ..
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the best 37,000 light curves were examined , and rv follow - up of three planet candidates was done on the vlt in september 2001 ( malln - ornelas et al . , in prep . ) . in december 2001
we used the 3.6-m cfht for 16 nights ( 14 clear ) to observe the explore ii field , located at @xmath1 ( yee et al .
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Suppose that you have an abstract for a scientific paper: we describe a new high precision measurement of the production cross - section for the @xmath0 meson in proton - proton collisions @xmath1 for five beam momenta at low access energy region @xmath2 conducted at the detection system together with an updated results of all other previous measurements of @xmath1 at . .
And you have already written the first three sentences of the full article: recently the increased interest in the properties of the @xmath3 and @xmath0 meson can be observed due to extensive experimental search of the @xmath3 and @xmath0 bound states performed e.g. at cosy @xcite , elsa @xcite , gsi @xcite , jinr @xcite , jparc @xcite , lpi @xcite , and mami @xcite as well as intensive theoretical investigations e.g. @xcite .
properties of @xmath0 in nuclear medium are related with the effects of @xmath4 anomaly at finite density @xcite , which is reflected in the large mass of the @xmath0 meson compared to the masses of the other members of the pseudoscalar meson nonet @xcite , and with the @xmath3-@xmath0 mixing @xcite .
experiment @xcite has provided already an important data for these studies @xcite , with the most precise direct measurement of the total width of the @xmath0 meson @xmath5@xcite , and the first rough estimation of the @xmath0-n interaction from the excitation function of the cross section for the @xmath6 reaction @xcite . here.
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we describe an analysis of the data used earlier for @xmath7 determination in view of the extraction of the production cross - section for the @xmath0 meson @xmath1 in proton - proton collisions and an update of the @xmath1 values presented previously @xcite .
in the reported measurement the @xmath0 meson was produced in proton - proton collisions reaction and its mass was reconstructed based on the momentum vectors of protons taking part in the @xmath8 reaction which was measured at five different beam momenta using the detector setup @xcite installed at the cooler synchrotron cosy @xcite in research centre jlich .
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Suppose that you have an abstract for a scientific paper: the screen mapping " introduced by susskind to implement t hooft s holographic hypothesis is studied . for a single screen time , there are an infinite number of images of a black hole event horizon , almost all of which have smaller area on the screen than the horizon area .
this is consistent with the focusing equation because of the existence of focal points .
however , the _ boundary _ of the past ( or future ) of the screen obeys the area theorem , and so always gives an expanding map to the screen , as required by the holographic hypothesis .
these considerations are illustrated with several axisymmetric static black hole spacetimes .
@xmath0 utrecht - thu-96/11 + gr - qc/9602043 + * focusing and the holographic hypothesis * + .5 cm _
institute for theoretical physics , university of utrecht + p.o .
box 80.006 , 3508 ta utrecht , the netherlands _ + and + _ department of physics , university of maryland + college park , md 20742 - 4111 , usa _
+ corley , [email protected] .
And you have already written the first three sentences of the full article: the generalized second law of thermodynamics@xcite is the statement that the entropy outside event horizons plus the bekenstein - hawking entropy @xmath1 ( in planck units ) of all event horizons can not decrease .
the law seems to be correct , at least in quasistationary processes@xcite .
if it is true , it must be that @xmath1 is the most entropy that could possibly be contained in a region bounded by an area @xmath2@xcite ..
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there has been much debate over the past 20 years about whether or not this bound really holds , and part of the problem in proving it is that it is not precisely clear what the statement means .
nevertheless , there are many reasonable arguments in support of it .
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Suppose that you have an abstract for a scientific paper: despite their structural similarities , srbi@xmath0ta@xmath0o@xmath1 ( sbt ) and srbi@xmath0nb@xmath0o@xmath1 ( sbn ) undergo a different sequence of phase transitions .
the phase diagram of sbt as a function of the temperature includes an intermediate phase between the high - temperature phase and the ferroelectric ground state , while in the niobium compound the intermediate phase is suppressed and a single transition between the high- and low temperature structures is observed .
we present @xmath2 calculations that reveal the relevance of a trilinear coupling between three symmetry - adapted modes to stabilize the ground sate in both compounds , being this coupling much stronger in sbn . within the framework of the phenomenological landau theory ,
it is shown that by solely increasing the strength of the trilinear coupling the topology of the phase diagram of sbt can change up to suppress the intermediate phase .
monte carlo simulations on an idealized @xmath3 hamiltonian confirm that the trilinear coupling is the key parameter that determines the sequence of phase transitions and that for higher dimensionality of the order parameters the stability region of the intermediate phase is narrower . .
And you have already written the first three sentences of the full article: the aurivillius phases are layered bismuth compounds that obey the general formula bi@xmath4a@xmath5b@xmath6o@xmath7 @xcite .
the family includes many members that present ferroelectricity at room temperature , and they have been widely studied for potential technological applications mainly in thin film nonvolatile memories.@xcite srbi@xmath0ta@xmath0o@xmath1 ( sbt ) and srbi@xmath0nb@xmath0o@xmath1 ( sbn ) are members of the family , with @xmath8 and @xmath9 and their structure is formed by alternating two srmo@xmath10 ( m@xmath11ta , nb ) perovskite blocks and one bi@xmath0o@xmath0 slab ( fig .
[ fig : structure ] ) ..
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tantalum and niobium present very similar physical and chemical properties , including the valence and atomic radii . as a result , sbt and sbn present isomorphous polar structures at room temperature @xcite and analogous mechanical and electrical characteristics .
however , their phase diagrams are qualitatively different : on increasing the temperature sbt undergoes a phase transition to a non - polar orthorhombic phase that does not arise in sbn .
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Suppose that you have an abstract for a scientific paper: star formation in most galaxies requires cosmic gas accretion because the gas consumption time is short compared to the hubble time .
this accretion presumably comes from a combination of infalling satellite debris , cold flows , and condensation of hot halo gas at the cool disk interface , perhaps aided by a galactic fountain . in general
, the accretion will have a different specific angular momentum than the part of the disk that receives it , even if the gas comes from the nearby halo . then the gas disk expands or shrinks over time . here
we show that condensation of halo gas at a rate proportional to the star formation rate in the fountain model will preserve an initial shape , such as an exponential , with a shrinking scale length , leaving behind a stellar disk with a slightly steeper profile of younger stars near the center .
this process is slow for most galaxies , producing imperceptible radial speeds , and it may be dominated by other torques , but it could be important for blue compact dwarfs , which tend to have large , irregular gas reservoirs and steep blue profiles in their inner stellar disks . .
And you have already written the first three sentences of the full article: disk accretion is attributed to cold cosmic flows @xcite and dwarf satellite capture @xcite through the virial radius , which may be 20 times larger than the disk ( see reviews in * ? ? ?
* ; * ? ? ?
it is not clear whether these flows reach the disk directly . @xcite and @xcite suggest that the magellanic stream breaks apart and gets ionized by hydrodynamic instabilities without falling onto the disk ..
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@xcite also found substantial heating and ionization of the layers surrounding a cosmic cold flow in simulations of the milky way .
the numerical algorithm used for the simulation might also be important ; the arepo code @xcite has such high resolution that the infalling gas breaks apart by instabilities and heats up before reaching the disk .
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Suppose that you have an abstract for a scientific paper: we compare the structural properties of the street networks of ten different european cities using their primal representation . we investigate the properties of the geometry of the networks and a set of centrality measures highlighting differences and similarities among cases .
in particular , we found that cities share structural similarities due to their quasi planarity but that there are also several distinctive geometrical proprieties .
a principal component analysis is also performed on the distributions of centralities and their respective moments , which is used to find distinctive characteristics by which we can classify cities into families .
we believe that , beyond the improvement of the empirical knowledge on streets network proprieties , our findings can open new perspectives in the scientific relation between city planning and complex networks , stimulating the debate on the effectiveness of the set of knowledge that statistical physics can contribute for city planning and urban morphology studies . + * keywords : * complex street networks , urban form , city classification , centrality . .
And you have already written the first three sentences of the full article: defining urban form is certainly an important and difficult issue , especially if one wants to supply useful knowledge to urban planners and urban designers or new knowledge for city scientist . in this paper
we address this question , and we try to improve the empirical - based knowledge on the structure of a city by studying the urban street networks of ten european cities , namely edinburgh , leicester , sheffield , oxford , worcester , lancaster , catania , barcelona , bologna and geneva .
the form of cities is the subject of an area of urban studies named urban morphology ..
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urban morphology in its current form emerged between the 40s and the 60s of the xx century from the work of two scholars as prominent as different : the german - born and then british urban geographer m.r.conzen ( 1960 ) , and the italian architect and historian saverio muratori ( 1960 ) . in this area , the main subject of investigation is the urban fabric of the city at the scale of the neighborhood , street , plot and building .
a different branch of urban morphology has stemmed from the sciences of complex systems building on a long standing tradition in regional analysis , economic geography and modeling @xcite .
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Suppose that you have an abstract for a scientific paper: background : : : the information about the @xmath0li@xmath1he reaction rates of astrophysical interest can be obtained by extrapolating direct data to lower energies , or by indirect methods . the indirect trojan horse method , as well as various r - matrix and polynomial fits to direct data , estimate the electron screening energies much larger than the adiabatic limit .
calculations that include the subthreshold resonance estimate smaller screening energies .
purpose : : : obtain the @xmath0li@xmath2he reaction r - matrix parameters and the bare astrophysical @xmath3 factor for the energies relevant to the stellar plasmas by fitting the r - matrix formulas for the subthreshold resonances to the @xmath3-factor data above 60 kev .
methods : : : the bare @xmath3 factor is calculated using the single- and the two - level r - matrix formulas for the closest to the threshold @xmath4 and @xmath5 subthreshold states at @xmath6 , @xmath7 and @xmath8 mev .
the electron screening potential @xmath9 is then obtained by fitting it as a single parameter to the low - energy data .
the calculations are also done by fitting @xmath9 simultaneously with other parameters .
results : : : the low - energy @xmath3 factor is dominated by the @xmath5 subthreshold resonance at @xmath6 mev .
the influence of the other two subthreshold states is small .
the resultant electron screening is smaller than the adiabatic value .
the fits that neglect the electron screening above 60 kev produce a significantly smaller electron screening potential .
the calculations show a large ambiguity associated with a choice of the initial channel radius .
conclusions : : : the r - matrix fits do not show a significantly larger @xmath10 than predicted by the atomic physics models .
the r - matrix best fit provides @xmath11 ev and @xmath12 mev b. .
And you have already written the first three sentences of the full article: to obtain the reaction rates relevant for the nuclear astrophysics , experimental data should be extrapolated to the very low - energy region ( the gamow window ) .
the cross section depends strongly on the energy and therefore is expressed in terms of the astrophysical @xmath13 factor @xmath14 in the system of units , in which @xmath15 , the coulomb ( sommerfeld ) parameter @xmath16 .
@xmath17 is the charge of the nucleus @xmath18 , @xmath19 and @xmath20 are the relative momentum and the reduced mass of the interacting nuclei , @xmath21 is their relative kinetic energy in the c.m . frame ..
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the extrapolation of the cross section down to low energies assumes , that the coulomb potential of the target nucleus and a projectile results from bare nuclei . in experimental conditions , however , the coulomb potential is screened by electrons surrounding the target nucleus , thus reducing the height of the coulomb barrier and leading to a higher cross section .
as the energy approaches zero , the electron screening potential @xmath10 enhances the bare nucleus astrophysical factor @xmath22 .
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Suppose that you have an abstract for a scientific paper: we prove the strong sensitivity of the @xmath0 cross section at the large hadron collider on the explicitly cp - violating phases of the minimal supersymmetric standard model , where @xmath1 is the lightest supersymmetric higgs boson .
-0.125 in -0.125 in 6.5 in 8.75 in dcpt-09 - 26 + ippp-09 - 13 + shep-08 - 36 + revised * explicit cp violation in the mssm + through @xmath2 * pacs : 14.80.da , 14.80.ec , 11.30.er .
And you have already written the first three sentences of the full article: one of the main reasons to build the large hadron collider ( lhc ) at cern is the determination of the mechanism of electro - weak symmetry breaking ( ewsb ) . in the standard model ( sm ) of elementary particle physics and its extensions incorporating supersymmetry ( susy )
, ewsb occurs through the higgs mechanism , which in turn leads to the existence of one or more higgs particles . within the minimal supersymmetric standard model ( mssm ) , a realisation of susy with minimal particle content and gauge structure ,
the higgs potential conserves charge & parity ( cp ) at tree level @xcite . beyond the trivial order.
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, several studies have shown that cp invariance of the higgs potential may in principle be broken by radiative corrections @xcite , as the vacuum expectation values ( vevs ) of the two higgs doublets can develop a relative phase @xcite .
this type of cp violation is generally referred to as spontaneous cp violation and it requires a light higgs state as a result of the georgi - pais theorem @xcite , but the possibility of the latter has now essentially been ruled out by experiment @xcite@xcite .
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Suppose that you have an abstract for a scientific paper: we calculate the full stellar - structural evolution of donors in am cvn systems formed through the wd channel coupled to the binary s evolution . contrary to assumptions made in prior modelling , these donors are not fully convective over much of the am cvn phase and do not evolve adiabatically under mass loss indefinitely . instead , we identify three distinct phases of evolution : a mass transfer turn - on phase ( during which @xmath0 continues to decrease even after contact , the donor contracts , and the mass transfer rate accelerates to its maximum ) , a phase in which the donor expands adiabatically in response to mass loss , and a cooling phase beginning at @xmath1 4555 minutes during which the donor contracts .
the physics that determines the behaviour in the first and third phases , both of which are new outcomes of this study , are discussed in some detail .
we find the overall duration of the turn - on phase to be between @xmath2-@xmath3 yrs , significantly longer than prior estimates .
we predict the donor s luminosity , @xmath4 , and effective temperature , @xmath5 . during the adiabatic expansion phase ( ignoring irradiation effects ) , @xmath6@xmath7 and @xmath8@xmath9 k. however
, the flux generated in the accretion flow dominates the donor s intrinsic light at all times .
the impact of irradiation on the donor extends the phase of adiabatic expansion to longer @xmath0 , slows the contraction during the cooling phase , and alters the donor s observational characteristics .
irradiated donors during the adiabatic phase can attain surface luminosities up to @xmath10 .
we argue that the turn - on and cooling phases both will leave significant imprints on the am cvn population s @xmath0-distribution .
finally , we show that the eclipsing am cvn system sdss j0926 + 3624 provides evidence that wd - channel systems with non - zero entropy donors contribute to the am cvn population , and we discuss the observational signature of the donor in this system .
binaries : close ....
And you have already written the first three sentences of the full article: the am canum venaticorum ( am cvn ) variables are a class of he - rich objects with variability periods of @xmath11566 minutes .
various lines of evidence ( see 1 of * ? ? ?
* for a brief summary ) indicate these periods are orbital in origin and that ongoing mass - transfer from a low - mass , essentially pure - he donor onto a white dwarf ( wd ) accretor is taking place ..
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thus , am cvn systems form the wd - accreting class of so - called ultracompact binaries : interacting stellar binaries with orbital periods , @xmath0 , below the minimum @xmath0 attainable by h - dominated objects ( @xmath117080 minutes , see , e.g. , * ? ? ?
* ) . at such short @xmath0 ,
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Suppose that you have an abstract for a scientific paper: let @xmath0 be a morphism between normal complex varieties , where @xmath1 is kawamata log terminal . given any differential form @xmath2 , defined on the smooth locus of @xmath1
, we construct a `` pull - back form '' on @xmath3 . the pull - back map obtained by this construction is @xmath4-linear , uniquely determined by natural universal properties and exists even in cases where the image of @xmath5 is entirely contained in the singular locus of @xmath1 .
one relevant setting covered by the construction is that where @xmath5 is the inclusion ( or normalisation ) of the singular locus @xmath6 . as an immediate corollary
, we show that differential forms defined on the smooth locus of @xmath1 induce forms on every stratum of the singularity stratification .
the same result also holds for many whitney stratifications . .
And you have already written the first three sentences of the full article: differential forms and sheaves of differentials are fundamental objects and indispensable tools in the study of smooth varieties and complex manifolds .
it is well - known that for singular spaces , there is no single notion of `` differential form '' that captures all features of the smooth case .
instead , there are several competing definitions , each generalising certain aspects ..
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the following two classes of differential forms are particularly important .
khler differentials : : uniquely determined by universal properties , khler differentials are the most fundamental notion of differential form .
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Suppose that you have an abstract for a scientific paper: we calculate the shear viscosity @xmath0 in a neutron star core composed of nucleons , electrons and muons ( @xmath1 being the electron - muon viscosity , mediated by collisions of electrons and muons with charged particles , and @xmath2 the neutron viscosity , mediated by neutron - neutron and neutron - proton collisions ) . deriving @xmath1 , we take into account the landau damping in collisions of electrons and muons with charged particles via the exchange of transverse plasmons .
it lowers @xmath1 and leads to the non - standard temperature behavior @xmath3 .
the viscosity @xmath4 is calculated taking into account that in - medium effects modify nucleon effective masses in dense matter .
both viscosities , @xmath1 and @xmath2 , can be important , and both are calculated including the effects of proton superfluidity .
they are presented in the form valid for any equation of state of nucleon dense matter .
we analyze the density and temperature dependence of @xmath5 for different equations of state in neutron star cores , and compare @xmath5 with the bulk viscosity in the core and with the shear viscosity in the crust . .
And you have already written the first three sentences of the full article: neutron stars are very compact .
their typical masses are @xmath6 ( where @xmath7 is the mass of the sun ) , while their radii are as small as @xmath8 km . as a result ,
a neutron star core contains matter , whose density @xmath9 reaches several @xmath10 ( @xmath11 g @xmath12 being the density of the standard saturated nuclear matter ) ..
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the core is composed of uniform neutron - rich nuclear matter and extends from @xmath13 to the stellar center ( where @xmath9 can be as high as @xmath14 ) .
it attracts special attention because of its poorly known composition and equation of state ( eos ) ; e.g. , ref . @xcite . from outside , the core is surrounded by a thin ( @xmath15 km thick ) and light ( a few per cent by mass ) crust composed of atomic nuclei , strongly degenerate electrons and ( after the neutron drip at @xmath16 g @xmath12 ) free neutrons . in this paper , we study the shear viscosity of neutron star cores .
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Suppose that you have an abstract for a scientific paper: we put forward a new highly efficient source of paired photons entangled in polarization with an ultra - large bandwidth .
the photons are generated by means of a conveniently designed spontaneous parametric down - conversion process in a semiconductor type - ii bragg reflection waveguide .
the proposed scheme aims at being a key element of an integrated source of polarization - entangled photon pairs highly suitable for its use in a multi - user quantum - key - distribution system .
99 a. serafini , s. mancini , and s. bose , `` distributed quantum computation via optical fibers , '' phys .
. lett . * 96 * , 010503 ( 2006 ) .
j. i. cirac , a. k. ekert , s. f. huelga , and c. macchiavello , `` distributed quantum computation over noisy channels , '' phys .
rev .
a * 59 * , 42494254 ( 1999 ) .
g. ribordy , j. brendel , j. gautier , n. gisin , and h. zbinden , `` long - distance entanglement - based quantum key distribution , '' phys .
rev .
a * 63 * , 012309 ( 2000 ) .
a. k. ekert , `` quantum cryptography based on bell s theorem , '' phys .
rev .
lett . * 67 * , 661663 ( 1991 ) .
m. hillery , v. buek , and a. berthiaume , `` quantum secret sharing , '' phys .
rev .
a * 59 * , 18291834 ( 1999 ) . c. h. bennett , g. brassard , c. crepeau , r. jozsa , a. peres , and w. k. wootters , `` teleporting an unknown quantum state via dual classical and einstein - podolsky - rosen channels , '' phys .
. lett . * 70 * , 18951899 ( 1993 ) .
t. s. humble , and w. p. grice , `` spectral effects in quantum teleportation , '' phys .
rev .
a * 75 * , 022307 ( 2007 ) .
h. hubel , m. r. vanner , t. lederer , b. blauensteiner , t. lorunser , a. poppe , and a. zeilinger , `` high - fidelity transmission of polarization encoded qubits from an entangled source over 100 km of fiber , '' opt .
express * 15 * , 78537862 ( 2007 ) .
t. e. chapuran , p. toliver , n. a. peters , j. jackel , m. s. goodman , r. j. runser , s. r. mcnown , n. dallmann , r. j. hughes , k.....
And you have already written the first three sentences of the full article: many quantum computing applications @xcite and quantum communication protocols @xcite , such as quantum teleportation @xcite , are based on the sharing of entangled two - photon states between two distant receiving stations .
the paired photons can be distributed through free space transmission channels , or alternatively , through single - mode fiber optical links . indeed
, fiber optical links are the most practical way to share entanglement between a large number of users ..
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the polarization degree of freedom is the most widely used resource to generate entanglement between two distant parties .
polarization - entangled photons can be generated by means of spontaneous parametric down - conversion ( spdc ) , a nonlinear optical process in which two lower - frequency photons ( signal and idler ) are generated when a strong pump interacts with the atoms of a nonlinear material .
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Suppose that you have an abstract for a scientific paper: a simple one - dimensional gas - piston kinetic model gives the interaction potential between two colliding heavy ions . in the frame of the classical , thermodynamical approach ,
the colliding heavy ions are not submitted to friction , but produces an irreversible phenomena with cause at the difference of pressure @xmath0 felt " by the nucleon gas when ions collide with the target when compared with the pressure that nuclear matter exert on their boundaries when in thermodynamical equilibrium , and offers a straightforward way to calculate interacting potentials .
[ multiblock footnote omitted ] .
And you have already written the first three sentences of the full article: the numerical calculations implicated in the study of nuclear reactions between heavy ions have an extreme complexity .
some times it is advisable to build simple models that allow to obtain concrete images of the phenomena based on classical conceptions and made useful predictions . in this perspective , d. h.
e. gross @xcite proposed the paradigmatic piston - gas model ..
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however , our interpretation differs , not sustaining a friction process .
we propose in this letter a classical , thermodynamical approach to determine the interaction potential to which two colliding heavy ions ( with mass number @xmath1 above 40 ) are submitted , and its dependency relatively to their nuclear temperature @xmath2 .
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Suppose that you have an abstract for a scientific paper: we study a feedback control version of the flashing brownian ratchet , in which the application of the flashing potential depends on the state of the particles to be controlled .
taking the view that the ratchet acts as a maxwell s demon , we study the relationship that exists between the performance of the demon as a rectifier of random motion and the amount of information gathered by the demon through measurements . in the context of a simple measurement model ,
we derive analytic expressions for the flux induced by the feedback ratchet when acting on one particle and a few particles , and compare these results with those obtained with its open - loop version , which operates without information .
our main finding is that the flux in the feedback case has an upper bound proportional to the square - root of the information .
our results provide a quantitative analysis of the value of information in feedback ratchets , as well as an effective description of imperfect or noisy feedback ratchets that are relevant for experimental applications .
pacs : 05.40.-a , 89.70.+c , 02.30.yy keywords : ratchet ; brownian motor ; feedback ; closed - loop ; information . .
And you have already written the first three sentences of the full article: thermal ratchets or brownian motors can be viewed as controllers that act on stochastic systems with the aim of inducing directed motion through the rectification of fluctuations @xcite . in most cases ,
the system to be controlled is modelled as a collection of brownian particles undergoing langevin dynamics , and the control action that is , the rectification mechanism is implemented by applying random or deterministic time - dependent perturbations to the particles . in this context , one can distinguish , as is common in control theory @xcite , two types of ratchets : ( i ) _ open - loop _ ratchets , which are ratchets that apply a rectifying potential independently of the state of the system to be controlled ; ( ii ) _ closed - loop _ or _ feedback
_ ratchets , whose rectification action on a system has an explicit dependence on that system s evolution in time ..
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examples of open - loop ratchets include the flashing ratchet @xcite and the rocking ratchet @xcite .
an example of closed - loop ratchet based on the flashing ratchet was proposed in @xcite ( see also @xcite ) .
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Suppose that you have an abstract for a scientific paper: we demonstrate that our recently introduced stochastic hebb - like learning rule @xcite is capable of learning the problem of timing in general network topologies generated by an algorithm of watts and strogatz @xcite .
we compare our results with a learning rule proposed by bak and chialvo @xcite and obtain not only a significantly better convergence behavior but also a dependence of the presentation order of the patterns to be learned by introduction of an additional degree of freedom which allows the neural network to select the next pattern itself whereas the learning rule of bak and chialvo stays uneffected .
this dependence offers a bidirectional communication between a neuronal and a behavioural level and hence completes the action - perception - cycle which is a characteristics of any living being with a brain . .
And you have already written the first three sentences of the full article: one of the most fascinating complex adaptive systems in nature is the brain . despite its relatively simple basic units
the neurons the cooperative bebaviour of the interconnected neurons and their functional implications are only poorly understood .
the problem in investigating this system is not only its complexity , because e.g. the human brain consists of about @xmath0 neurons @xcite , but also its characteristic cycle structure which is known as action - perception - cycle ..
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the difficulty with the action - perception - cycle , which was already known to von uexkll in 1928 @xcite , is that a closed formulation of the problem has to include a coupled description of the brain and the environment because the actions of an animal are transformed by the environment to perceptions which are transformed by the brain to actions and so on . from this
it is also clear that neither the perceptions nor the actions occurring in the system are randomly generated . in this paper
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Suppose that you have an abstract for a scientific paper: we discuss the quantum action principles and equations of motion for heavy quark effective field theory .
we prove the so - called equivalence theorem for hqeft which states that the physical predictions of hqeft are independent from the choice of interpolating fields .
en passant we point out that hqeft is in fact more subtle than the quantum mechanical foldy - wouthuysen transformation . .
And you have already written the first three sentences of the full article: heavy quark effective field theory ( hqeft ) has arguably been the fastest growing sector of elementary particle theory in the four years since its introduction @xcite .
this can be ascribed to two features : on one hand the spin and flavor symmetries are phenomenologically successful @xcite and , on the other hand , corrections to the symmetry limit @xmath0 are well defined and therefore calculable . given this state of affairs
, it seems appropriate to investigate the theoretical formalism of hqeft in all orders of the combined @xmath1 , @xmath2 expansion ..
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it is only a slight exaggeration that quantum field theory ( qft ) has no physical content and is just the most powerful tool known for the calculation of @xmath3-matrix elements @xcite .
the fields and the off - shell values of their green s functions are not observable and therefore all qfts which lead to identical @xmath3-matrices are physically equivalent .
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Suppose that you have an abstract for a scientific paper: we study the magnon modes in the presence of a topological soliton in a 2d heisenberg easy axis ferromagnet .
the problem of magnon scattering on the soliton with arbitrary relation between the soliton radius @xmath0 and the `` magnetic length '' @xmath1 is investigated for partial modes with different values of the azimuthal quantum numbers @xmath2 .
truly local modes are shown to be present for all values of @xmath2 , when the soliton radius is enough large .
the eigenfrequencies of such internal modes are calculated analytically on limiting case of a large soliton radius and numerically for arbitrary soliton radius .
it is demonstrated that the model of an isotropic magnet , which admits an exact analytical investigation , is not adequate even for the limit of small radius solitons , @xmath3 : there exists a local mode with nonzero frequency .
we use the data about local modes to derive the effective equation of soliton motion ; this equation has the usual newtonian form in contrast to the case of the easy plane ferromagnet .
the effective mass of the soliton is found . .
And you have already written the first three sentences of the full article: nonlinear topologically nontrivial excitations ( solitons ) are well known to play a special role in low dimensional magnetic systems .
for example , the presence of vortices in 2d easy plane ( ep ) magnets gives rise to the berezinski kosterlitz
thouless ( bkt ) phase transition.@xcite kinks in 1d magnets and localized belavin polyakov ( bp ) solitons @xcite in 2d isotropic magnets are responsible for the destruction of long range order at finite temperature ..
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the soliton signatures in dynamical response functions can be observed experimentally .
translational motion of solitons leads to the so called soliton central peak.@xcite another possibility to detect soliton signature is to look for magnon modes , localized at the soliton ( _ local modes _ , lm ) ; such modes are the cause of soliton magnetic resonance at the characteristic frequencies of `` intrinsic '' motion.@xcite this can be explained within the scope of the so called soliton phenomenology , where the magnet can be described as a two component gas of elementary excitations : solitons and magnons . such an approach was developed for 1d magnets.@xcite it was shown that the contribution of magnons and soliton magnon interaction is important for this approach , as is obvious , for example , in the discussion of soliton magnetic resonance.@xcite but for 1d magnets the soliton
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Suppose that you have an abstract for a scientific paper: in this work we use the heavy - quark - light - diquark picture to study the semileptonic decay @xmath0 in the so - called hybrid scheme .
namely , we apply the heavy quark effective theory ( hqet ) for larger @xmath1 ( corresponding to small recoil ) , which is the invariant mass square of @xmath2 , whereas the perturbative qcd approach for smaller @xmath1 to calculate the form factors .
the turning point where we require the form factors derived in the two approaches to be connected , is chosen near @xmath3 .
it is noted that the kinematic parameter @xmath4 which is usually adopted in the perturbative qcd approach , is in fact exactly the same as the recoil factor @xmath5 used in hqet where @xmath6 , @xmath7 are the four velocities of @xmath8 and @xmath9 respectively .
we find that the final result is not much sensitive to the choice , so that it is relatively reliable .
moreover , we apply a proper numerical program within a small range around @xmath10 to make the connection sufficiently smooth and we parameterize the form factor by fitting the curve gained in the hybrid scheme .
the expression and involved parameters can be compared with the ones gained by fitting the experimental data . in this scheme
the end - point singularities do not appear at all .
the calculated value is satisfactorily consistent with the data which is recently measured by the delphi collaboration within two standard deviations . .
And you have already written the first three sentences of the full article: the general theory of qcd has been developed for more than 40 years , and at present , nobody ever doubts its validity .
however , on the other side there is still not a reliable way to deal with the long - distance effects of qcd which are responsible for the quark confinement and hadronic transition matrix elements , because their evaluations can not be done in perturbative approach .
thus , one needs to factorize the perturbative sub - processes and the non - perturbative parts which correspond to different energy scales ..
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the perturbative parts are in principle , calculable to any order within the framework of quantum field theory , whereas the non - perturbative part must be evaluated by either fitting data while its universality is assumed , or invoking concrete models .
the perturbative qcd method ( pqcd ) has been applied to study processes where transitions from heavy mesons or baryons to light hadrons are concerned @xcite , namely the pqcd which includes the sudakov resummation , is proved to be successful for handling processes with small 4-momentum transfer @xmath1 . indeed the processes involving heavy hadrons may provide us with an opportunity to study strong interaction , because compared to @xmath11 there exist natural energy scales ( heavy quark masses ) which can be used to factorize the perturbative contributions from the non - perturbative effects . on the other hand , for the processes involving heavy hadrons , at small recoil region , where @xmath12 is close to unity ( @xmath6 and @xmath7 denote the four - velocities of the initial and final hadrons ) , i.e. the momentum transfer @xmath1 is sufficiently large , the heavy quark effective theory ( hqet ) works well due to an extra symmetry @xmath13 @xcite .
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Suppose that you have an abstract for a scientific paper: a microscopic theory of the phonon - induced resistance oscillations in weak perpendicular magnetic fields is presented .
the calculations are based on the consideration of interaction of two - dimensional electrons with three - dimensional ( bulk ) acoustic phonons and take into account anisotropy of the phonon spectrum in cubic crystals .
the magnetoresistance is calculated for [ 001]-grown gaas quantum wells .
the results are in agreement with available experimental data .
apart from the numerical results , analytical expressions for the oscillating part of magnetoresistance are obtained .
these expressions are valid in the region of high - order magnetophonon resonances and describe the oscillating magnetoresistance determined by several groups of phonons polarized along certain high - symmetry directions . .
And you have already written the first three sentences of the full article: in recent years , experimental studies of transport properties of high - mobility two - dimensional ( 2d ) electron gas in weak perpendicular magnetic fields have uncovered a variety of remarkable quantum phenomena caused by transitions of electrons between different landau levels .
such transitions can lead to oscillations of dissipative resistance as a function of the magnetic field .
for example , under steady - state microwave illumination of the 2d gas the resistance oscillates with a period determined by the ratio of the radiation frequency to the cyclotron frequency @xmath0 ..
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this phenomenon is known as the microwave - induced resistance oscillations ( miro).@xmath1 for a sufficiently high radiation power the miro minima evolve into the intervals of magnetic field where the dissipative resistance vanishes.@xmath2 next , it was found that an increase in the electric current passing though the 2d layer substantially reduces the resistance@xmath3 and leads to oscillations of the resistance as a function of either the magnetic field or the current.@xmath4 such oscillations are controlled by the ratio of a characteristic energy , which is defined as the drop of the hall electric field across the classical cyclotron diameter , to the cyclotron energy .
this phenomenon has been called the hall field - induced resistance oscillations ( hiro ) .
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Suppose that you have an abstract for a scientific paper: we present a concise account of our development of the first genuine local density approximation ( lda ) to the energy density functional ( edf ) for fermionic systems with superfluid correlations , with a particular emphasis to nuclear systems . .
And you have already written the first three sentences of the full article: the theorem of hohenberg and kohn @xcite concerning the existence of a universal energy density functional ( edf ) , and its subsequent implementation as a local density approximation ( lda ) , lead to a new qualitative approach to the study of electron systems , from atoms , to molecules , to condensed matter systems and macromolecules in particular and other fermionic systems in general .
even though neither hohenberg and kohn nor kohn and sham gave us recipes on how to construct the edf , various approximation schemes with increasing level of sophistication have been created .
moreover , the edf ideology has been extended to finite temperatures and finite excitation energies as well . however , essentially all of the implementations of the lda and edf have been limited so far to normal fermi systems , namely , systems with no pairing correlations ..
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there were two attempts to extend the lda to superconducting systems @xcite , however , the pairing field in this approach was still a nonlocal object .
one can present the argument that because electron superconductivity is phonon mediated , and since phonons have a spectrum limited by the debye frequency , such a genuinely nonlocal character of the electron pairing field is natural . in our opinion
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Suppose that you have an abstract for a scientific paper: simplicial lattices provide an elegant framework for discrete spacetimes . the inherent orthogonality between a simplicial lattice and its circumcentric dual yields an austere representation of spacetime which provides a conceptually simple form of einstein s geometric theory of gravitation . a sufficient understanding of simplicial spacetimes has been demonstrated in the literature for spacetimes devoid of all non - gravitational sources .
however , this understanding has not been adequately extended to non - vacuum spacetime models .
consequently , a deep understanding of the diffeomorphic structure of the discrete theory is lacking .
conservation laws and symmetry properties are attractive starting points for coupling matter with the lattice
. we present a simplicial form of the contracted bianchi identity which is based on the e. cartan moment of rotation operator .
this identity manifest itself in the conceptually - simple form of a kirchhoff - like conservation law .
this conservation law enables one to extend regge calculus to non - vacuum spacetimes and provides a deeper understanding of the simplicial diffeomorphism group . .
And you have already written the first three sentences of the full article: regge calculus ( rc ) provides a natural framework for the description of discrete spacetimes @xcite .
it has been applied to problems ranging from quantum gravity to classical relativity @xcite . in recent years
rc has been used in quantum gravity to construct emergent spacetime models @xcite and to investigate the spin - foam approach and its perturbative regime @xcite . in particular.
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, @xcite utilizes a pre - geometric framework wherein the spacetime is an emergent structure from an underlying quantum system .
the unitary operators of the discrete quantum system act as source terms for the ensuing spacetime . if an approach of this kind is to utilize rc as the coupling to the underlying quantum dynamics , it is incumbent upon us to understand the nature of the coupling of matter and fields to a rc lattice spacetime .
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Suppose that you have an abstract for a scientific paper: we construct a self - consistent model which describes a black hole from formation to evaporation including the back reaction from the hawking radiation . in the case where a null shell collapses , at the beginning the evaporation occurs , but it stops eventually , and a horizon and singularity appear . on the other hand , in the generic collapse process of a continuously distributed null matter , the black hole evaporates completely without forming a macroscopically large horizon nor singularity . we also find a stationary solution in the heat bath , which can be regarded as a normal thermodynamic object .
[ cols= " > " , ] * a self - consistent model of + the black hole evaporation * hikaru kawai@xmath0 , yoshinori matsuo@xmath1 and yuki yokokura@xmath0 _ @xmath0 department of physics , kyoto university , kitashirakawa , kyoto 606 - 8502 , japan + @xmath1 kek theory center , high energy accelerator research organization(kek ) , + oho 1 - 1 , tsukuba , ibaraki 305 - 0801 , japan _ .
And you have already written the first three sentences of the full article: in the analysis of the black hole evaporation , one usually assumes that a horizon is formed in a collapse process , and examines the evaporation and entropy in the static black hole @xcite-@xcite . in this paper
we try to build a self - consistent model which describes both formation and evaporation of a black hole including the back reaction from the hawking radiation .
that is , we solve the semi - classical einstein equation in a self - consistent manner : @xmath2 where @xmath3 contains the contribution from both the collapsing matter and the hawking radiation . from the solution we can investigate whether a horizon and singularity are formed or not ..
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we first consider a null shell as the collapsing matter and construct the geometry by connecting the inside flat metric and the outside outgoing vaidya metric on the shell .
note that particle creation generally occurs in a time - dependent gravitational potential , and especially , the hawking radiation can appear without a horizon @xcite .
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Suppose that you have an abstract for a scientific paper: we show somewhat unexpectedly that whenever a general bernstein - type maximal inequality holds for partial sums of a sequence of random variables , a maximal form of the inequality is also valid . _ dedicated to the memory of sndor csrg _ .
And you have already written the first three sentences of the full article: let @xmath0 be a sequence of independent random variables such that for all @xmath1 , @xmath2 and for some @xmath3 and @xmath4 for integers @xmath5 , @xmath6 .
the classic bernstein inequality ( cf .
@xcite , page 855 ) says that , in this situation , for all @xmath7 and @xmath8@xmath9 moreover ( cf ..
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@xcite , theorem b.2 ) , its maximal form also holds ; that is , we have @xmath10 it turns out that , under a variety of assumptions , a sequence of not necessarily independent random variables @xmath0 will satisfy a generalized bernstein - type inequality of the following form : for suitable constants @xmath11 , @xmath12 , @xmath13 and @xmath14 for all @xmath15 , @xmath7 and @xmath16 , @xmath17 where , for any choice of @xmath18 , we denote the partial sum @xmath19 here are some examples . [ ex1 ]
let @xmath0 be a stationary sequence satisfying @xmath20 and .
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Suppose that you have an abstract for a scientific paper: the various scenarios proposed for the origin of the multiple , helium - enriched populations in massive globular clusters are critically compared to the relevant constraining observations . among accretion of helium - rich material by pre - existing stars , star formation out of ejecta from massive agb stars or from fast rotating massive stars , and pollution by population iii stars , only the agb option appears to be viable .
accretion or star formation out of outflowing disks would result in a spread of helium abundances , thus failing to produce the distinct , chemically homogeneous sub - populations such as those in the clusters @xmath0 cen and ngc 2808 .
pollution by population iii stars would fail to produce sub - populations selectively enriched in helium , but maintaining the same abundance of heavy elements .
still , it is argued that for the agb option to work two conditions should be satisfied : i ) agb stars experiencing the hot bottom burning process ( i.e. , those more massive than @xmath1 ) should rapidly eject their envelope upon arrival on the agb , thus experiencing just a few third dredge - up episodes , and ii ) clusters with multiple , helium enriched populations should be the remnants of much more massive systems , such as nucleated dwarf galaxies , as indeed widely assumed . [ firstpage ] _ ( galaxy : ) _ globular clusters : general _ ( galaxy : ) _ * globular clusters : individual : @xmath0 cen , ngc 1851 , ngc 2808 , ngc 6388 , ngc 6441 , m54 * stars : agb and post - agb .
And you have already written the first three sentences of the full article: the recent discovery of discrete , multiple stellar populations within several among the most massive globular clusters ( gc ) in the milky way ( e.g. , bedin et al .
2004 : piotto et al .
2007 ) has brought new interest and excitement on gc research ..
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further excitement was added by the realization that some of these stellar populations are selectively enriched in helium to very high values ( @xmath2 ) , without such enrichment being accompanied by a corresponding increase in the heavy element abundance of the expected size , if at all ( e.g. norris 2004 ; piotto et al .
2005 , 2007 ) .
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Suppose that you have an abstract for a scientific paper: in this review , we give an introduction to the structural and functional properties of the biological networks .
we focus on three major themes : topology of complex biological networks like the metabolic and protein - protein interaction networks , nonlinear dynamics in gene regulatory networks and in particular the design of synthetic genetic networks using the concepts and techniques of nonlinear physics and lastly the effect of stochasticity on the dynamics .
the examples chosen illustrate the usefulness of interdisciplinary approaches in the study of biological networks .
department of physics , bose institute , 93/1 , a.p.c .
road , calcutta-700009 , india .
And you have already written the first three sentences of the full article: networks are widely prevalent in all spheres of life @xcite . a network of acquaintances is the simplest example one can think of . social , economic and political networks of various kinds are part of human society .
the internet , a network of information resources , plays a vital role in the gathering , sharing and transmission of information .
a network consists of nodes connected by links ..
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figure 1 shows the example of a network in which the solid circles denote the nodes and the solid lines the links .
some examples of real life networks are as follows : in a network describing an electrical power grid , the generators , transformers and substations are the nodes and the high - voltage transmission lines connecting them the links . in the world wide web ( www )
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Suppose that you have an abstract for a scientific paper: we make use of information provided in the titles and abstracts of over half a million publications that were published by the american physical society during the past 119 years . by identifying all unique words and phrases and determining their monthly usage patterns , we obtain quantifiable insights into the trends of physics discovery from the end of the 19th century to today . we show that the magnitudes of upward and downward trends yield heavy - tailed distributions , and that their emergence is due to the matthew effect .
this indicates that both the rise and fall of scientific paradigms is driven by robust principles of self - organization .
data also confirm that periods of war decelerate scientific progress , and that the later is very much subject to globalization . ] the 20th century is often referred to as the century of physics @xcite . from x - rays to the semiconductor industry ,
the human society today would be very different were it not for the progress made in physics laboratories around the world . and while amid the economic woes the budget for science is being cut down relentlessly @xcite , it seems now more than ever the need is there to remind the policy makers of this fact .
although to the layman the progress made on an individual level may appear to be puny and even needless , the history teaches us that collectively the physics definitively delivers .
it is therefore of interest to understand how the progress made so far came to be , and how to best maintain it in the future .
should there be overarching authorities that dictate which scientific challenges to address and prioritize , or should we rely on the spontaneous emergence of progress ? we know
, for example , that the acquisition of citations @xcite as well as the acquisition of collaborators @xcite are subject to preferential attachment .
these two processes are neither regulated nor imposed .
they are perpetuated by scientific excellence and individual choice .
in fact , barabsi and albert....
And you have already written the first three sentences of the full article: the timeline of publications for different journals and overall is presented in fig .
it can be observed that the overall output ( bottom most color stripe ) increases steadily over time .
an obvious exception is the world war ii period , during which the production dropped almost an order of magnitude , from nearly 100 publications per month before and after the war to below 10 during the war ..
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this confirms , not surprisingly , that periods of war decelerate scientific progress or at least very much hinder the dissemination of new knowledge . by geocoding the affiliations ,
it is also possible to infer where the physics published in the physical review has been coming from . as can be inferred from fig .
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Suppose that you have an abstract for a scientific paper: we study the superfluid transition in a quasi - two - dimensional fermi gas with a magnetic field tuning through a feshbach resonance . using an effective two - dimensional hamiltonian with renormalized interaction between atoms and dressed molecules ,
we investigate the berezinskii - kosterlitz - thouless transition temperature by studying the phase fluctuation effect .
we also take into account the trapping potential in the radial plane , and discuss the number and superfluid density distributions .
these results can be compared to experimental outcomes for gases prepared in one - dimensional optical lattices . .
And you have already written the first three sentences of the full article: the study of superfluidity and superconductivity in two - dimensional ( 2d ) fermi systems has attracted great attention in the past several decades , partly because of its close relationship to the problem of high-@xmath0 superconductors @xcite .
recently , the experimental progress on creating quasi - low - dimensional atomic gases in optical lattices @xcite and on atom chips @xcite provides us a possibility of realizing and studying superfluidity in a more controllable platform . in particular , with the aid of tuning an external magnetic field through a feshbach resonance , the interaction between fermionic atoms can be tuned continuously from the bardeen - cooper - schrieffer ( bcs ) limit to the bose - einstein condensation ( bec ) limit , so that the bcs - bec crossover can be studied @xcite .
the bcs - bec crossover in a 2d fermi system has been discussed at both zero @xcite and finite temperatures @xcite , where an effective 2d hamiltonian with atom - atom interaction ( called model 1 ) is employed . however , for strongly interacting fermionic atoms in a realistic quasi-2d geometry , due to the inevitable population of many excited levels along the strongly confined transverse direction @xcite , one needs to introduce a composite particle called dressed molecule to account for the population in these transverse excited levels , and write down a more complicated form for the effective 2d hamiltonian ( called model 2 ) with renormalized interaction between atoms ( in the transverse ground level ) and dressed molecules @xcite ..
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we have shown that the model 1 and the model 2 hamiltonians lead to qualitatively distinct results in some cases @xcite .
for instance , for quasi-2d fermions in a weak global harmonic trap , the model 1 hamiltonian predicts a constant value of the thomas - fermi cloud size at zero temperature from the bcs to the bec limit .
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Suppose that you have an abstract for a scientific paper: in this talk i describe a natural framework for bi - large neutrino mixing within the context of two models 1 ) a simple generalization of the mssm and 2 ) an so(10 ) model .
our starting point is the frampton , glashow , yanagida [ fgy ] neutrino mass ansatz which can easily accomodate bi - large neutrino mixing .
the main point of fgy , however , is to obtain a theory of neutrino masses with only one possible cp violating angle .
they argue that the sign of the baryon asymmetry of the universe ( assuming leptogenesis ) is then correlated with cp asymmetries possibly observable in accelerator experiments .
unfortunately , there is a fly in the ointment .
it was later shown by raidal and strumia [ rs ] that there is a sign ambiguity which frustrates the above correlation .
we note that the raidal - strumia ambiguity is resolved in our models . .
And you have already written the first three sentences of the full article: let us first summarize the present values of neutrino masses and mixing angles obtained by fitting atmospheric , solar , reactor and accelerator neutrino oscillation data .
the atmospheric and solar neutrino masses and mixing angles are given below * @xmath0 @xmath1 * @xmath2 @xmath3 with an approximate mixing matrix given by @xmath4 for this talk , i will assume three light neutrinos .
recall , the observed small neutrino masses can naturally be generated via the see - saw mechanism ..
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the @xmath5 neutrino mass matrix is given by @xmath6 , where @xmath7 ( @xmath8 ) is the dirac rl ( majorana rr ) mass matrix .
of course , the main problem with neutrino mixing angles is the fact that they are significantly larger than ckm mixing .
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Suppose that you have an abstract for a scientific paper: in this paper we consider a sequential `` meson emission '' mechanism for charmonium decays of the type @xmath0 , where @xmath1 is a generic charmonium state , @xmath2 is a nucleon and @xmath3 is a light meson .
this decay mechanism , which may not be dominant in general , assumes that an @xmath4 pair is created during charmonium annihilation , and the light meson @xmath3 is emitted from the outgoing nucleon or antinucleon line .
a straightforward generalization of this model can incorporate intermediate @xmath5 resonances .
we derive dalitz plot event densities for the cases @xmath6 , @xmath7 , @xmath8 , @xmath9 and @xmath10 and @xmath11 and @xmath12 ( and implicitly , any @xmath13 , @xmath14 or @xmath15 final light meson )
. it may be possible to separate the contribution of this decay mechanism to the full decay amplitude through characteristic event densities .
for the decay subset @xmath16 the two model parameters are known , so we are able to predict absolute numerical partial widths for @xmath17 . in the specific case @xmath18 the predicted partial width and @xmath19 event distribution
are intriguingly close to experiment .
we also consider the possibility of scalar meson and glueball searches in @xmath20 .
if the meson emission contributions to @xmath21 decays can be isolated and quantified , they can be used to estimate meson - nucleon strong couplings @xmath22 , which are typically poorly known , and are a crucial input in meson exchange models of the @xmath23 interaction .
the determination of @xmath24 from @xmath18 and the ( poorly known ) @xmath25 and the anomalous `` strong magnetic '' coupling @xmath26 from @xmath27 are considered as examples .
p 0p|p f_0 0p|p ^0 p0@xmath28p@xmath29 .
And you have already written the first three sentences of the full article: charmonium strong decays of the type @xmath30 , where @xmath1 is a generic charmonium state , @xmath2 is a nucleon and @xmath3 is a light meson , have recently attracted interest both as sources of information regarding the @xmath5 spectrum @xcite and in searches for a low energy @xmath31 enhancement @xmath32 " , which has been reported in @xmath33 @xcite and @xmath34 @xcite , but thus far not in @xmath35 .
these decays are also of interest because their partial widths can be used to estimate the @xmath36 associated charmonium production cross sections at panda @xcite .
as we shall show here , they may also provide information on @xmath37 meson - nucleon coupling constants , which could be used to identify unusual resonances such as molecule or glueball candidates ..
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specific @xmath30 reactions that have recently been studied experimentally include @xmath38 @xcite , @xmath39 and @xmath40 @xcite , and @xmath41 @xcite ; @xmath42 @xcite , @xmath43 @xcite , @xmath44 @xcite , @xmath45 @xcite and @xmath41 @xcite , and ( upper limit ) @xmath46 @xcite ; and @xmath47 and @xmath39 @xcite .
these decays may prove to be complicated processes in which several decay mechanisms contribute significantly .
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Suppose that you have an abstract for a scientific paper: we demonstrate that there are systematic scale errors in the [ fe / h ] values determined by the hamburg / eso survey ( and by the hk survey by inference ) for certain extremely metal poor ( emp ) highly c - enhanced giants .
the consequences of these scale errors are that a ) the fraction of carbon stars at extremely low metallicities has been substantially overestimated in several papers in the recent literature b ) the number of emp stars known is somewhat lower than has been quoted in the recent literature c ) the yield for emp stars by the hk and the he s survey is somewhat lower than is stated in the recent literature .
a preliminary estimate for the frequency of carbon stars among the giants in the he s sample with @xmath0 [ fe / h ] @xmath1 dex is 7.4@xmath2% , and for c - rich giants with [ c / fe ] @xmath3 + 1.0 dex is 14.4@xmath4% .
we rely on the results of an extensive set of detailed abundance analyses of stars expected to have [ fe / h ] @xmath5 dex selected from the hamburg / eso survey to establish these claims .
these analyses of @xmath650 he s candidate extremely metal poor stars have been carried out in as homogeneous a manner as possible . here
we present the key results of detailed abundance analyses of 14 c - stars selected in this way about 80% of such c - stars show highly enhanced ba as well , with c enhanced by a factor of about 100 , and [ ba / c ] roughly solar .
these stars often show prominent lead lines , and presumably are the remnants of the secondary in a mass transfer binary system where the former primary was an agb star , which transferred substantial mass at that evolutionary stage .
the remaining 20% of the c - stars do not show an enhancemement of the s - process neutron capture elements around the ba peak .
they tend to be the most metal - poor stars studied .
we suggest that they too result from mass transfer across a binary system .
( published abstract will be shorter due to space limitations ) .
And you have already written the first three sentences of the full article: we are engaged in a large scale project to find additional emp stars in the halo of our galaxy by mining the database of the he s .
the normal procedures outlined by @xcite to isolate emp stars from the candidate lists produced by the he s were followed .
the candidates were vetted via moderate resolution spectroscopy at large telescopes to eliminate the numerous higher abundance interlopers ..
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most of the follow up spectra for the stars discussed here were obtained with the double spectrograph on the hale telescope at palomar mountain .
we intend to observe all candidates to the magnitude limit of the he s ( b @xmath6 17.5 ) in our fields ; with @xmath61600 moderate resolution spectra in hand from campaigns at palomar and at the las campanas observatory , observations are now complete in @xmath6990 deg@xmath7 , complete to b=16.5 in an additional @xmath6700 deg@xmath7 , and approaching completion in the remaining fields . these follow up spectra are used to determine an accurate measure of the metallicity of the star via a combination of strength of absorption in h@xmath8 ( determining @xmath9 ) and in the ca ii line at 3933 ( the kp index ) , which then determines [ fe / h ] .
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Suppose that you have an abstract for a scientific paper: in this work , we give a detailed discussion for qcd factorization involved in the complete chirally enhanced power corrections in the heavy quark limit for @xmath0 decays to two light pseudoscalar mesons , and present some detailed calculations of radiative corrections at the order of @xmath1 .
we point out that the infrared finiteness of the vertex corrections in the chirally enhanced power corrections requires twist-3 light - cone distribution amplitudes ( lcdas ) of the light pseudoscalar symmetric .
however , even in the symmetric condition , there is also a logarithmic divergence from the endpoints of the twist-3 lcdas in the hard spectator scattering .
we point out that the decay amplitudes of @xmath2 predicted by qcd factorization are really free of the renormalization scale dependence , at least at the order of @xmath1 . at last
, we briefly compare the qcd factorization with the generalized factorization and pqcd method . _
/-2.5 mm _ * pacs numbers 13.25.hw 12.38.bx * .
And you have already written the first three sentences of the full article: the study of @xmath0 decays plays an important role in understanding the origin of @xmath3 violation and physics of heavy flavor .
we expect that the parameters of the cabibbo - kobayashi - maskawa ( ckm ) matrix in the standard model , for instance , the three angles @xmath4 , @xmath5 and @xmath6 in the unitary triangle , can be well - determined from @xmath0 decays , especially from the charmless non - leptonic two - body b decays . experimentally , many @xmath0 experiment projects have been running ( cleo , babar , belle etc . ) , or will run in forthcoming years ( btev , cern lhcb , desy herab etc . ) . with the accumulation of the data ,
the theorists will be urged to gain a deeper sight into @xmath0 decays , and to reduce the theoretical errors in determining the ckm parameters from the experimental data . in the theoretical frame ,.
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the standard approach to deal with such decays is based on the low - energy effective hamiltonian which is obtained by the wilson operator product expansion method ( ope ) . in this effective hamiltonian
, the short - distance contributions from the scale above @xmath7 have been absorbed into the wilson coefficients with the perturbative theory and renormalization group method .
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Suppose that you have an abstract for a scientific paper: in an oxide apertured quantum dot ( qd ) micropillar cavity - qed system , we found strong qd hysteresis effects and lineshape modifications even at very low intensities corresponding to @xmath0 intracavity photons .
we attribute this to the excitation of charges by the intracavity field ; charges that get trapped at the oxide aperture , where they screen the internal electric field and blueshift the qd transition .
this in turn strongly modulates light absorption by cavity qed effects , eventually leading to the observed hysteresis and lineshape modifications .
the cavity also enables us to observe the qd dynamics in real time , and all experimental data agrees well with a power - law charging model .
this effect can serve as a novel tuning mechanism for quantum dots .
cavity quantum electrodynamics with quantum dots ( qds ) coupled to microcavities enables various applications such as single - photon switches @xcite , generation of non - classical states of light @xcite and hybrid quantum information schemes @xcite . however , qds deviate from an ideal atom - like systems as they strongly interact with their environment , for example through nuclear spins @xcite and via charge traps @xcite .
these interactions need to be understood and controlled in order to improve the qd coherence properties . for this purpose cavities
are very useful to probe the qd environment , through increased light - matter interaction . and reflectivity @xmath1 . the qd cooperativity @xmath2 and dephasing rate @xmath3 obtained from the fits are named in the figures .
the black arrows denote a second qd in the same cavity .
scans were taken on @xmath4s timescale .
( d ) presents simulations that predict the scans in ( c ) . ] in this letter we investigate such a qd - cavity system . for sufficiently low optical field intensity
this system can be described by the qed of an effective 2-level system in a single - mode cavity .
for increasing intensities we report on bistable and strong nonlinear....
And you have already written the first three sentences of the full article: in this supplemental material we will first present photocurrent measurements . to confirm that a @xmath63 nm resonant
laser excites charges in the cavity region , we compare the photocurrent with when a @xmath53 nm off - resonant laser is used .
then we compare photoluminescence data with and without the presence of an aperture , to demonstrate that the oxide aperture plays an important role in trapping the charges , ..
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these observations support our claim that the mechanism behind the observed nonlinear effects in the resonant qd scans , is the excitation of charges that are trapped by the oxide aperture .
current as function of bias voltage was measured without ( dark ) and with the presence of a @xmath64 nm or a @xmath63 nm laser , see fig .
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Suppose that you have an abstract for a scientific paper: a nanoscale device consisting of a metal nanowire , a dielectric , and a gate is proposed .
a combination of quantum and thermal stochastic effects enable the device to have multiple functionalities , serving alternately as a transistor , a variable resistor , or a simple resistive element with @xmath0 characteristics that can switch between ohmic and non - ohmic . by manipulating the gate voltage ,
stochastic transitions between different conducting states of the nanowire can be induced , with a switching time as short as picoseconds . with an appropriate choice of dielectric
, the transconductance of the device can significantly exceed the conductance quantum @xmath1 , a remarkable figure of merit for a device at this lengthscale .
department of physics and astronomy , sacramento state university , 6000 j street , sacramento , ca 95819 department of physics , university of arizona , 1118 e. fourth street , tucson , az 85721 department of physics and courant institute of mathematical sciences , new york university , new york , ny 10003 .
And you have already written the first three sentences of the full article: variable resistors are commonly used circuit elements in many electronic applications .
however , their large size and slow response time have heretofore limited their use primarily to the human - circuit interface . in this article , we describe how the exploitation of quantum and stochastic effects at the nanoscale @xcite allows one to combine what would ordinarily be distinct macroscale circuit elements into a single nanoscale device with multiple functionalities , and to achieve response times on the order of picoseconds .
the device architecture we propose is illustrated in fig ..
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[ fig : diagram ] .
the physics behind its operation is the following : a metal nanowire is the active circuit element , and is embedded in a dielectric sheath , surrounded by an outer conductor of comparable dimensions , referred to as the gate .
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Suppose that you have an abstract for a scientific paper: we consider a closed region @xmath0 of 3d quantum space modeled by @xmath1 spin - networks . using the concentration of measure phenomenon
we prove that , whenever the ratio between the boundary @xmath2 and the bulk edges of the graph overcomes a finite threshold , the state of the boundary is always thermal , with an entropy proportional to its area .
the emergence of a thermal state of the boundary can be traced back to a large amount of entanglement between boundary and bulk degrees of freedom . using the dual geometric interpretation provided by loop quantum gravity , we interprete such phenomenon as a pre - geometric analogue of thorne s `` hoop conjecture '' , at the core of the formation of a horizon in general relativity . .
And you have already written the first three sentences of the full article: in statistical mechanics , small systems weakly coupled to a large bath are described by canonical ensembles when the composite system ( system + bath ) is in a microcanonical state@xcite .
when we deal with a closed many - body quantum systems , the reduced density matrix of a small part of the system can be proven to be almost canonical , even if the state of the overall system is pure @xcite .
such gibbs - like behaviour emerges locally , in closed systems , as a direct consequence of the concentration of measure phenomenon ..
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its application to quantum statistical mechanics goes under the name of `` canonical typicality''@xcite .
it is a purely kinematic analysis on the hilbert space of the system and it can be proven in full generality by means of levy s lemma@xcite . a brief summary of canonical typicality and of levy s lemma can be found in appendix [ app : typ ] and [ app : levy ] . + in a recent paper@xcite
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Suppose that you have an abstract for a scientific paper: although the internet as - level topology has been extensively studied over the past few years , little is known about the details of the as taxonomy .
an as `` node '' can represent a wide variety of organizations , e.g. , large isp , or small private business , university , with vastly different network characteristics , external connectivity patterns , network growth tendencies , and other properties that we can hardly neglect while working on veracious internet representations in simulation environments . in this paper
, we introduce a radically new approach based on machine learning techniques to map all the ases in the internet into a natural as taxonomy .
we successfully classify 95.3% of ases with expected accuracy of 78.1% .
we release to the community the as - level topology dataset augmented with : 1 ) the as taxonomy information and 2 ) the set of as attributes we used to classify ases .
we believe that this dataset will serve as an invaluable addition to further understanding of the structure and evolution of the internet . .
And you have already written the first three sentences of the full article: the rapid expansion of the internet in the last two decades has produced a large - scale system of thousands of diverse , independently managed networks that collectively provide global connectivity across a wide spectrum of geopolitical environments . from 1997 to 2005
the number of globally routable as identifiers has increased from less than 2,000 to more than 20,000 , exerting significant pressure on interdomain routing as well as other functional and structural parts of the internet .
this impressive growth has resulted in a heterogenous and highly complex system that challenges accurate and realistic modeling of the internet infrastructure . in particular.
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, the as - level topology is an intermix of networks owned and operated by many different organizations , e.g. , backbone providers , regional providers , access providers , universities and private companies .
statistical information that faithfully characterizes different as types is on the critical path toward understanding the structure of the internet , as well as for modeling its topology and growth . in topology modeling ,
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Suppose that you have an abstract for a scientific paper: we study the dynamical interaction in which the two single runaway stars @xmath0 and @xmath1 and the binary @xmath2 acquired their unusually high space velocity .
the two single runaways move in almost opposite directions with a velocity greater than 100@xmath3 away from the trapezium cluster .
the star @xmath2 is an eccentric ( @xmath4 0.8 ) binary moving with a velocity of about 10@xmath3 at almost right angles with respect to the two single stars .
the kinematic properties of the system suggest that a strong dynamical encounter occurred in the trapezium cluster about @xmath5myr ago .
curiously enough , the two binary components have similar spectral type but very different masses , indicating that their ages must be quite different .
this observation leads to the hypothesis that an exchange interaction occurred in which an older star was swapped into the original @xmath2 binary .
we test this hypothesis by a combination of numerical and theoretical techniques , using n - body simulations to constrain the dynamical encounter , binary evolution calculations to constrain the high orbital eccentricity of @xmath2 and stellar evolution calculations to constrain the age discrepancy of the two binary components .
we find that an encounter between two low eccentricity ( @xmath6 ) binaries with comparable binding energy , leading to an exchange and the ionization of the wider binary , provides a reasonable solution to this problem .
[ firstpage ] methods : n - body simulations - stars : binaries : spectroscopic - stars : individual : hd 34078 , hd 37043 , hd 38666 .
And you have already written the first three sentences of the full article: ob runaways are a subgroup of spectral type o and b stars which are recognized by their unusually high velocity ( @xmath7 ) , often away from known star forming regions ( blaauw , 1961 ) . stone ( 1979 ) also included stars at large distance ( up to several kpc ) from the galactic plane for which no parent association could be found .
about 40 per cent of o stars and 5 - 10 per cent of b stars are runaways ( stone 1991 ) , and only one in ten ob runaways has a known binary companion ( gies & bolton 1986 ) .
the peculiar velocities of about @xmath8 ob runaways have been determined and the trajectories of @xmath920 can be traced back to a nearby association ( hoogerwerf et al . 2000 , 2001 ) , supporting the idea that these stars originated in stellar clusters from which they were later ejected with high velocities ..
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the two main mechanisms that have been proposed to explain the high velocities of ob runaways are : * ejection upon a supernova in a binary system ( zwicky 1957 ; blaauw 1961 ) ; * ejection by a close multiple encounter in a star cluster ( poveda , ruiz & allen , 1967 ) .
we refer to scenario 1 and 2 as _ supernova ejection _ and _ dynamical ejection _ , respectively . in the supernova ejection scenario
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Suppose that you have an abstract for a scientific paper: this review describes recent experimental and theoretical advances in forming molecules in ultracold gases of trapped alkali metal atoms , both by magnetic tuning through feshbach resonances and by photoassociation .
molecular bose - einstein condensation of long - range states of both boson dimers and fermion dimers was achieved in 2002 - 3 .
condensates of boson dimers were found to be short - lived , but long - lived condensates of fermion dimers have been produced .
signatures of triatomic and tetraatomic molecules have recently been observed .
both homonuclear and heteronuclear molecules have been formed by photoassociation , mostly in very high vibrational levels .
recent attempts to produce ultracold molecules in short - range states ( low vibrational levels ) are described . experimental and theoretical work on collisions of ultracold molecules is discussed . to be published in international reviews in physical chemistry , vol .
25 , issue 4 ( oct - dec 2006 ) .
And you have already written the first three sentences of the full article: the achievement of bose - einstein condensation in 1995 in dilute gases of @xmath0rb @xcite , @xmath1li @xcite and @xmath2na @xcite revolutionised atomic physics . since that time , bose - einstein condensation has been achieved for several other alkali metal species ( @xmath3rb @xcite , @xmath4k @xcite and @xmath5cs @xcite ) and a few other systems ( @xmath6h @xcite , metastable he @xcite , @xmath7yb @xcite and @xmath8cr @xcite ) .
intense effort has been devoted to the study of the new properties of bose - einstein condensates @xcite .
the field was further broadened by the achievement of quantum degeneracy in fermi gases of @xmath9k @xcite and @xmath10li @xcite , and ultracold fermionic quantum matter has proved to exhibit a new range of novel properties ..
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bose - einstein condensation and fermi degeneracy in dilute gases typically require temperatures between 1 nk and 1 @xmath11k .
however , new quantum properties start to appear at temperatures around 1 mk , where de broglie wavelengths become large compared to atomic and molecular dimensions . under these circumstances
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Suppose that you have an abstract for a scientific paper: the model of coherent quadrupole and octupole motion ( cqom ) is applied to describe non - yrast split parity - doublet spectra in odd - mass nuclei .
the yrast levels are described as low - energy rotation - vibration modes coupled to the ground single - particle ( s.p . )
state , while the non - yrast parity - doublet structures are obtained as higher - energy rotation - vibration modes coupled to excited s.p . states .
it is shown that the extended model scheme describes both the yrast and non - yrast quasi parity - doublet spectra and the related b(e1 ) and b(e2 ) transition rates in different regions of heavy odd-@xmath0 nuclei .
the involvement of the reflection - asymmetric deformed shell model to describe the single - particle motion and the coriolis interaction on a deeper level is discussed . .
And you have already written the first three sentences of the full article: the observation of positive- and negative - parity states connected by e1 and e3 transitions in atomic nuclei is usually explained with the presence of quadrupole - octupole deformations @xcite . in the even - even nuclei one
typically observes alternating - parity bands , whereas in odd - mass nuclei the spectrum is characterized by a quasi parity - doublet structure @xcite .
the low - lying ( yrast ) structure of the quadrupole - octupole spectra was relatively well studied within different microscopic and collective model approaches @xcite@xcite ( see also @xcite and references therein ) ..
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however , the interpretation and the model classification of the higher , non - yrast parts of these spectra is still limited .
recently the model of coherent quadrupole - octupole motion ( cqom ) @xcite was applied to describe non - yrast collective bands with positive and negative parities in even - even nuclei together with attendant b(e1 ) , b(e2 ) and b(e3 ) transition probabilities @xcite .
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Suppose that you have an abstract for a scientific paper: we study the transport through the kitaev chain with incommensurate potentials coupled to two normal leads by the numerical operator method .
we find a quantized linear conductance of @xmath0 , which is independent to the disorder strength and the gate voltage in a wide range , signaling the majorana bound states . while the incommensurate disorder suppresses the current at finite voltage bias , and then narrows the linear response regime of the @xmath1 curve which exhibits two plateaus corresponding to the superconducting gap and the band edge respectively .
the linear conductance abruptly drops to zero as the disorder strength reaches the critical value @xmath2 with @xmath3 the p - wave pairing amplitude and @xmath4 the hopping between neighbor sites , corresponding to the transition from the topological superconducting phase to the anderson localized phase .
changing the gate voltage also causes an abrupt drop of the linear conductance by driving the chain into the topologically trivial superconducting phase , whose @xmath1 curve exhibits an exponential shape . .
And you have already written the first three sentences of the full article: it is well known that the resonant tunneling through a localized level results in a quantized conductance @xcite , which was observed in the transport through quantum dots @xcite .
recently , researchers @xcite found that the resonant tunneling with a quantized conductance also happens in the presence of majorana bound states , providing a way of detecting the majorana fermions @xcite . from then on , there is a growing interest in the study of the quantum transport through the systems that accommodate majorana bound states @xcite . the majorana fermion is a proposed charge - neutral particle of its own antiparticle @xcite , which continuously attracts the efforts of searching for its existence in nature @xcite , due to its potential application in topological quantum computation @xcite
the majorana fermions were predicted to emerge as the edge quasi - particle excitations of the topological superconductors @xcite ..
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some proposals have been introduced for observing the majorana fermions in these systems , e.g. , by the topological josephson effect ( see ref .
@xcite for recent progress ) . but no experiments realized these proposals up to now .
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Suppose that you have an abstract for a scientific paper: a parallel 2d+1 split - step fourier method with crank - nicholson scheme running on multi - core shared memory architectures is developed to study the propagation of ultra - short high - intensity laser pulses in air .
the parallel method achieves a near linear speed - up with results for the efficiency of more than @xmath0 on a 24-core machine .
this method is of great potential application in studying the long - distance propagation of the ultra - short high intensity laser pulses .
example.eps gsave newpath 20 20 moveto 20 220 lineto 220 220 lineto 220 20 lineto closepath 2 setlinewidth gsave .4 setgray fill grestore stroke grestore .
And you have already written the first three sentences of the full article: investigation of the ultra - short high - intensity laser pulses propagation in air has been a hot topic in recent years due to its physical interest as well as its potential applications .
it is very important to predict well how the electromagnetic field of the pulse evolves as it propagates @xcite .
although some analytical solutions with some approximations can be found @xcite , in most applications the analytic approximations can not describe accurately the evolution of the pulses and we have to resort to numerical methods ..
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split - step fourier methods @xcite with the crank - nicholson scheme ( fcn ) in the transverse direction is often employed to numerical calculate the propagation of the ultra - short laser pulses via solving the nonlinear schr@xmath1dinger equation ( nlse)@xcite .
ultra - short high intensity laser pulse can convey high intensity over extended distances , and some applications need kilometer - range calculation .
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Suppose that you have an abstract for a scientific paper: we combine predictions for several hierarchical cosmogonies with observational evidence on damped ly@xmath0 systems to establish a correspondence between the high redshift galaxy population and the properties of damped ly@xmath0 systems ( dlas ) .
we assume that high redshift galaxies and damped ly@xmath0 systems are hosted by the same dark matter halos and require consistency between the predicted halo space density , the rate of incidence and the velocity width distribution of damped ly@xmath0 systems , and the observed galaxy luminosity function at the bright end .
we arrive at the following results : ( 1 ) predicted impact parameters between the damped absorption system and the luminous parts of the absorbing galaxy are expected to be very small ( 0.3 - 1 arcsec ) for most galaxies ; ( 2 ) luminosities of galaxies causing damped absorption are generally fainter than @xmath1 and damped ly@xmath0 systems are predicted to sample preferentially the outer regions of galaxies at the faint end of the galaxy luminosity function at high redshift .
therefore , dlas should currently provide the best probe of the progenitors of normal present - day galaxies .
= 24.5 cm [email protected] , [email protected] , [email protected] .
And you have already written the first three sentences of the full article: the physical conditions inferred from the absorption features caused by high redshift damped ly@xmath0 absorption systems ( dlas ) are , in several aspects , similar to those in the interstellar medium of present - day galaxies .
it has therefore been suggested to identify dlas with the progenitors of such galaxies ( e.g. wolfe 1988 ) . at low redshift dlas
show a wide variety of morphologies ( le brun et al ..
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1997 ) . at high redshift , however , few have been detected in emission ( mller & warren 1995 ; warren & mller 1995 , djorgovski et al .
1996 , djorgovski 1997 , mller & warren 1998 ) and the nature of galaxies causing the absorption remains unclear for the majority of dlas at high redshift .
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Suppose that you have an abstract for a scientific paper: nanophotonics has emerged as a powerful tool for manipulating light on chips .
almost all of today s devices , however , have been designed using slow and ineffective brute - force search methods , leading in many cases to limited device performance . in this article , we provide a complete demonstration of our recently proposed inverse design technique , wherein the user specifies design constraints in the form of target fields rather than a dielectric constant profile , and in particular we use this method to demonstrate a new demultiplexing grating .
the novel grating , which has not been developed using conventional techniques , accepts a vertical - incident gaussian beam from a free - space and separates o - band @xmath0 and c - band @xmath1 light into separate waveguides .
this inverse design concept is simple and extendable to a broad class of highly compact devices including frequency filters , mode converters , and spatial mode multiplexers .
@xmath2 ginzton laboratory , stanford university , stanford , ca , 94305 @xmath3 [email protected]_ conventional integrated photonic devices @xcite include components such as waveguide directional couplers @xcite , multimode interference couplers @xcite , distributed bragg reflectors @xcite , micro - ring resonators @xcite , adiabatic tapers @xcite and grating couplers @xcite . in all of these cases ,
the design space spans a relatively small @xmath4 number of parameters such as structure widths , heights and periodicity that are tuned throughout the photonic device design stage . to design a device
, the photonic engineer specifies a dielectric profile , computes the electromagnetic field response using maxwell s equations , and compares the response to the device specifications . the process is then repeated , modifying the dielectric profile each iteration , until satisfactory performance is obtained .
this brute force approach suffers from a long device design cycle , and does not take full advantage of the available design space of....
And you have already written the first three sentences of the full article: in general , we can specify the performance of a linear optical device by defining the mode conversion efficiency between a set of input modes and output modes @xcite .
these modes are specified by the user , and kept fixed during the optimization process .
the input modes @xmath10 are at frequencies @xmath11 , and can be represented by equivalent current density distributions @xmath12 . the generated electric fields @xmath13 should satisfy maxwell s equations in the frequency domain , @xmath14 where @xmath15 is the electric permittivity , and @xmath16 is the magnetic permeability of free space ..
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we can then specify @xmath17 output modes of interest for each input mode @xmath18 .
the output mode electric fields @xmath19 are given over output surfaces @xmath20 , where @xmath21 .
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Suppose that you have an abstract for a scientific paper: we present mid infrared ( mid - ir ) spectra of the compton - thick seyfert 2 galaxy ngc3281 , obtained with the thermal - region camera spectrograph ( t - recs ) at the gemini south telescope .
the spectra present a very deep silicate absorption at 9.7@xmath0 m , and [ siv]10.5@xmath0 m and [ neii]12.7@xmath0 m ionic lines , but no evidence of pah emission .
we find that the nuclear optical extinction is in the range 24 @xmath1 a@xmath2 @xmath1 83mag .
a temperature t = 300k was found for the black - body dust continuum component of the unresolved 65pc nucleus and at 130pc se , while the region at 130pc reveals a colder temperature ( 200k ) .
we describe the nuclear spectrum of ngc3281 using a clumpy torus model that suggests that the nucleus of this galaxy hosts a dusty toroidal structure .
according to this model , the ratio between the inner and outer radius of the torus in ngc3281 is @xmath3 = 20 , with 14 clouds in the equatorial radius with optical depth of @xmath4 = 40mag .
we would be looking in the direction of the torus equatorial radius ( @xmath5 = 60@xmath6 ) , which has outer radius of r@xmath7 11pc .
the column density is [email protected]@xmath9 and iron k@xmath10 equivalent width ( @xmath11 0.5 - 1.2kev ) are used to check the torus geometry .
our findings indicate that the x - ray absorbing column density , which classifies ngc3281 as a compton - thick source , may also be responsible for the absorption at 9.7@xmath0 m providing strong evidence that the silicate dust responsible for this absorption can be located in the agn torus . .
And you have already written the first three sentences of the full article: mid - infrared ( mid - ir ) spectra of active galactic nuclei ( agns ) are rich in emission features , such as polycyclic aromatic hydrocarbons ( pahs ) , molecular hydrogen and prominent forbidden emission lines @xcite .
another spectral feature commonly observed in agns is silicate at @xmath12 9.7@xmath0 m and 18@xmath0 m , both in emission and absorption .
the agn unified model proposes the existence of a dense concentration of absorbing material surrounding the central engine in a toroidal distribution , which blocks the broad line region ( blr ) emission from the line of sight in seyfert 2 ( sy2 ) galaxies @xcite ..
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however , it is not yet clear if the molecular gas and dust detected in mid - ir spectra is actually associated with the absorbing material required by the so - called torus in the unified model .
@xcite studied the distribution of the silicate feature strengths in a sample of 196 agns and ultraluminous infrared galaxies ( ulirgs ) .
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Suppose that you have an abstract for a scientific paper: we construct the quantum mechanical evolution operator in the functional schrdinger picture for a scalar field in spatially homogeneous flrw spacetimes when the field is a ) free and b ) coupled to a spacetime dependent source term . the essential element in the construction
is the causal propagator , linked to the commutator of two heisenberg picture scalar fields .
we show that the kernels can be expressed solely in terms of the causal propagator and derivatives of the causal propagator .
furthermore , we show that our kernel reveals the standard light cone structure in flrw spacetimes .
we finally apply the result to minkowski spacetime , to de sitter spacetime and calculate the forward time evolution of the vacuum in a general flrw spacetime . .
And you have already written the first three sentences of the full article: the functional schrdinger picture is based on the projection of quantum states and operators on the field amplitude basis .
guth and pi @xcite have already used it in the study of inflationary perturbations and related the width of the gaussian vacuum wave functional in de sitter spacetime to heisenberg picture scalar fields , thus casting quantum field theory in terms familiar from non - relativistic quantum mechanics .
a kernel is a quantum mechanical evolution operator in the functional schrdinger picture and is the fundamental object of any quantum mechanical theory ..
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it represents a transition amplitude from an arbitrary initial state at time @xmath0 to an arbitrary final state at time @xmath1 .
moreover , it allows to calculate the forward time evolution of any given initial field configuration . in this paper
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Suppose that you have an abstract for a scientific paper: we investigate the possible effects that deviations from kinetic equilibrium can have on massive particles as they decouple from chemical equilibrium .
different methods of solving the boltzmann equation yield significantly different relic number densities of such particles .
general considerations concerning the dirac or majorana structure of the particles are discussed .
it is shown that non - equilibrium effects are small for particles decoupling while strongly non - relativistic , as will be the case for most cold dark matter candidates .
+ pacs : 95.35.+d , 98.80.cq , 95.30.cq , 14.60.st + keywords : early universe , dark matter , neutrino physics .
And you have already written the first three sentences of the full article: deviations from thermodynamic equilibrium are of fundamental importance in the early universe .
the examples are plentiful , for example the freeze - out of photon thermodynamic equilibrium due to hydrogen recombination @xcite or the equivalent freeze - out of neutrinos slightly prior to electron - positron annihilation @xcite .
these phenomena have been investigated many times in the literature , but almost always in the context of deviations from chemical equilibrium , that is , kinetic or scattering equilibrium is assumed to hold at all times . in the limit of boltzmann statistics the single particle distribution then takes the form @xmath0 where @xmath1 is a pseudo - chemical potential , independent of @xmath2 . in recent years.
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there has been some discussions as to the validity of this assumption , especially concerned with the decoupling of neutrinos in the early universe @xcite . in this case
it has been found by several authors that the effects are small , but not negligible . in the present paper
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