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9,900 |
Suppose that you have an abstract for a scientific paper: we shall outline two ways of introducing the modification of einstein s relativistic symmetries of special relativity theory - the poincar symmetries . the most complete way of introducing the modifications is via the noncocommutative hopf - algebraic structure describing quantum symmetries .
two types of quantum relativistic symmetries are described , one with constant commutator of quantum minkowski space coordinates ( @xmath0-deformation ) and second with lie - algebraic structure of quantum space - time , introducing so - called @xmath1-deformation .
the third fundamental constant of nature - fundamental mass @xmath1 or length @xmath2 - appears naturally in proposed quantum relativistic symmetry scheme .
the deformed minkowski space is described as the representation space ( hopf - module ) of deformed poincar algebra .
some possible perspectives of quantum - deformed relativistic symmetries will be outlined .
address = institute for theoretical physics + university of wrocaw , pl .
m. borna 9 , 50 - 204 wrocaw , poland .
And you have already written the first three sentences of the full article: it is well - known that the nonrelativistic symmetries are described by the galilei group , with the galilean boosts relating dynamically equivalent frames which move with relative constant velocity @xmath3 @xmath4 the velocity values @xmath5 are not bounded and three boost generators @xmath6 ( @xmath7 ) commute @xmath8 = 0 \ , , \ ] ] einstein s equivalence of relativistic frames is described by the following modification of ( we choose for simplicity @xmath9 , @xmath10 the lorentz boosts @xmath11 generating pseudo - orthogonal rotations in the lobachevsky planes @xmath12 are described by the deformation of the abelian algebra @xmath13 = \frac{1}{c^2}\ , m_{ij } = \frac{1}{c^2 } \ \epsilon_{ijk } \ , m_k \ , , \ ] ] where @xmath14 generate the space rotations in ( @xmath15 ) plane ( @xmath16 ) .
the relativistic transformation should be applied to moving frames if the relative velocity ration @xmath17 is not negligible .
further , from the invariance of maxwell equations under poincar symmetries follows that @xmath18 should be interpreted as the velocity of electromagnetic waves ( light velocity ) ..
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the poincar symmetries of special relativity theory are described by 10 generators @xmath19 which satisfy the poincar lie algebra ( to compare with we should put @xmath20 ) @xmath21 = \eta_{\mu\rho } \ , m_{\nu\tau } - \eta_{\nu\rho } \ , m_{\mu\tau } + \eta_{\nu\tau}\ , m_{\mu\rho } - \eta_{\mu\tau}\ , m_{\nu\rho } \ , , \cr\cr & & [ m_{\mu\nu } , p_{\rho } ] = \eta_{\mu\rho } \ , p_\nu - \eta_{\nu\rho}\ , p_\mu \ , , \cr\cr & & [ p_{\mu } , p_{\nu } ] = 0\ , .
\end{aligned}\ ] ] the poincar algebra was considered for almost a century after einstein s discovery in 1905 as quite uncontested way of describing the equivalent space - time frames in relativistic elementary particle physics , however under the assumption that the gravitational effects are negligible .
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9,901 |
Suppose that you have an abstract for a scientific paper: predictions from a galactic structure and kinematic model are compared to the absolute proper - motions of about 30,000 randomly selected stars with @xmath0 derived from the southern proper - motion program ( spm ) toward the south galactic pole .
the absolute nature of the spm proper - motions allow us to measure not only the relative motion of the sun with respect to the local disk , but also , and most importantly , the overall state of rotation of the local disk with respect to galaxies .
the spm data are best fit by models having a solar peculiar motion of + 5 km s@xmath1 in the v - component ( pointing in the direction of galactic rotation ) , a large lsr speed of 270 km s@xmath1 , and a disk velocity ellipsoid that points towards the galactic center .
we stress , however , that these results rest crucially on the assumptions of both axisymmetry and equilibrium dynamics .
the absolute proper - motions in the u - component indicate a solar peculiar motion of @xmath2 km s@xmath1 , with no need for a local expansion or contraction term .
the implications of the large lsr speed are discussed in terms of gravitational mass of the galaxy inferred from the most recent and accurate determination for the proper - motion of the lmc .
we find that our derived value for the lsr is consistent both with the mass of the galaxy inferred from the motion of the clouds ( @xmath3 to @xmath4 kpc ) , as well as the timing argument , based on the binary motion of m31 and the milky way , and leo i and the milky way ( @xmath5 to @xmath6 kpc ) . .
And you have already written the first three sentences of the full article: in this paper , we present the main results from an analysis of the kinematic data obtained in the context of a massive _ absolute _ proper - motion survey , the southern proper - motion program ( spm hereafter ) .
our analysis is based on the spm catalog as described by platais et al .
this catalog provides positions , absolute proper - motions , and @xmath7 photometry for about 30,000 randomly selected stars , among other objects , near the south galactic pole ..
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the sky coverage of the spm catalog is about 720 deg@xmath8 in the magnitude range @xmath9 .
the accuracy of individual absolute proper - motions is 3 - 8 mas yr@xmath1 depending on the star s magnitude . for a complete description of the catalogue structure , contents , plate measurement and other astrometric / photometric details ,
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9,902 |
Suppose that you have an abstract for a scientific paper: manifolds admitting positive sectional curvature are conjectured to have a very rigid homotopical structure and , in particular , comparatively small euler charateristics .
however , this structure is still highly speculative and best results in this direction are known under the assumption of large isometric torus actions . in this article , we obtain upper bounds for euler characteristics of closed manifolds that admit metrics with positive curvature and isometric torus actions .
we apply our results to prove obstructions to symmetric spaces and manifold products and connected sums admitting positively curved metrics with symmetry , providing evidence for a conjecture of hopf .
we also derive vanishing properties of the elliptic genus of positively curved manifolds . .
And you have already written the first three sentences of the full article: the question of whether a given smooth manifold admits a riemannian metric with positive sectional curvature is nearly as old as the subject of riemannian geometry itself .
the classical gauss bonnet theorem @xmath0 relating the sectional curvature @xmath1 of a compact surface @xmath2 to its euler characteristic , @xmath3 , can be considered a first classification theorem of that kind : the only compact @xmath4manifold of positive curvature is the @xmath4sphere or the real projective plane .
moreover it poses one of the motivational questions for this article : to which degree does positive curvature determine the euler characteristic ? we shall approach an answer to this under mild symmetry assumptions . given the historic dimension of the topic , it is somewhat surprising that there exists few known examples of smooth manifolds admitting such metrics ..
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in fact , besides the rank one symmetric spaces @xmath5 , @xmath6 , @xmath7 and @xmath8 , there are no known simply connected manifolds in dimensions above 24 that admit metrics with positive sectional curvature .
see ziller @xcite for a survey of known examples and @xcite for recent examples in dimension seven .
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9,903 |
Suppose that you have an abstract for a scientific paper: detection and quantification of entanglement in quantum resources are two key steps in the implementation of various quantum - information processing tasks . here
, we show that bell - type inequalities are not only useful in verifying the presence of entanglement but can also be used to bound the entanglement of the underlying physical system .
our main tool consists of a family of clauser - horne - like bell inequalities that can not be violated maximally by any finite - dimensional maximally entangled state . using these inequalities , we demonstrate the explicit construction of both lower and upper bounds on the concurrence for two - qubit states .
the fact that these bounds arise from bell - type inequalities also allows them to be obtained in a semi - device - independent manner , that is , with assumption of the dimension of the hilbert space but without resorting to any knowledge of the actual measurements being performed on the individual subsystems . .
And you have already written the first three sentences of the full article: entanglement @xcite has long played a pivotal role in many quantum information processing tasks , such as secure communication using quantum - key distribution @xcite , teleportation of quantum states @xcite , quantum computation @xcite , reduction in communication complexity @xcite , and more recently , expansion and certification of randomness @xcite . as a result ,
the verification and quantification of this resource present in quantum systems is often an indispensable part of quantum - information processing ( qip ) protocols .
traditionally , for low - dimensional composite systems that are made up of only a few subsystems , the process of entanglement certification and/or quantification is carried out using complete quantum state tomography followed by the application of certain separability criteria @xcite ..
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this approach , however , suffers from the drawbacks that it is unnecessarily resource intensive and that the procedure of tomography may already be intractable for a physical system that is made up of only a handful of qubits ( see , for example , ref .
@xcite and references therein ) .
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9,904 |
Suppose that you have an abstract for a scientific paper: if @xmath0be solar neutrinos can be observed in real time experiments , then an extended region of @xmath1 can be probed by a proper analysis of the rapidly changing phase of vacuum oscillations due to the eccentricity of the earth s orbit about the sun . for the case of maximal vacuum mixing , a kind of fourier analysis of expected data for one year s time could uniquely pick out @xmath1 if it lies in the region @xmath2(ev)@xmath3 .
+ * pacs : 14.60.pq , 13.10.+q , 25.30.pt * = 100000 specialpagefalse @page=1 oddheaddraftto be submitted to phys .
rev .
d oddhead evenheadoddhead oddfoot@font evenfootoddfoot specialpagefalse oddhead evenheadoddhead .
And you have already written the first three sentences of the full article: in a previous work it was argued@xcite that with maximal vacuum mixing there is agreement , with minor modifications , between extant observations of solar neutrinos and predictions by the standard solar model ( ssm)@xcite . the maximal vacuum mixing case considered was that in which the phase of neutrino oscillations coming from the sun is averaged , leading to @xmath4 of the neutrinos arriving at the earth as electron neutrinos . as a result of this averaging , while @xmath5 was assumed to be maximal ( equal to one ) , @xmath1 was not determined and taken to lie in the approximate range @xmath6 with an exclusion of the approximate range @xmath7 for maximal mixing@xcite due to the lack of an observed day - night effect in the superkamiokande data@xcite . on the other hand , the recent first results of the sno measurement of charged current interactions produced by @xmath8b neutrinos@xcite , taken in combination with the elastic scattering result of the super - kamiokande collaboration@xcite , indicate that only about one third of the neutrinos arriving at the earth from the sun are electron neutrinos , with the other two thirds being @xmath9 or @xmath10 neutrinos .
oscillation into sterile neutrinos now seems relatively unlikely from the sno result .
while at first glance this comparison seems to make maximal vacuum mixing less likely , a global analysis of the sno result with the other solar neutrino experiments , chlorine@xcite , super - kamiokande@xcite , and gallium@xcite has led to the conclusion that `` the cc measurement by sno has not changed qualitatively the globally allowed solution space for solar neutrinos , although the cc measurement has provided dramatic and convincing evidence for neutrino oscillations and has strenghened the ths case for active oscillations with large mixing angles@xcite . ''.
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furthermore , global analyses@xcite@xcite do not completely exclude solutions to the solar neutrino problem in the mass region @xmath11 for maximal ( or near maximal ) mixing . in the following
, the time varying phase of oscillating @xmath0be neutrinos is investigated as a possible method to discover ( or exclude ) a solution of the solar neutrino problem in that mass region . in the mass region @xmath12
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9,905 |
Suppose that you have an abstract for a scientific paper: we consider the effect of an energy - dependent dipole form factor in the high - energy behavior of the forward amplitude .
the connection between the semihard parton - level dynamics and the hadron - hadron scattering is established by an eikonal qcd - based model .
our results for the proton - proton ( @xmath0 ) and antiproton - proton ( @xmath1 ) total cross sections , @xmath2 , obtained using the cteq6l1 parton distribution function , are consistent with the recent data from the totem experiment . .
And you have already written the first three sentences of the full article: the total cross section @xmath3 is a fundamental quantity in collisions of strongly interacting particles . at present
one of the main theoretical approaches for the description of @xmath4 is the qcd - inspired formalism @xcite . in this approach
the energy dependence of the total cross section is obtained from qcd via an eikonal formulation ..
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the high - energy dependence of @xmath4 is driven by the rapid increase in gluon density at small-@xmath5 . in this work
we explore the non - perturbative dynamics of qcd in order to describe , in both @xmath0 and @xmath1 channels , the total cross sections @xmath2 and the ratios of the real to imaginary part of the forward scattering amplitude , @xmath6 . in our calculations
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9,906 |
Suppose that you have an abstract for a scientific paper: it is found that 1e 1207.4 - 5209 could be a low - mass bare strange star if its small radius or low altitude cyclotron formation can be identified .
the age problems of five sources could be solved by a fossil - disk - assisted torque .
the magnetic dipole radiation dominates the evolution of psr b1757 - 24 at present , and the others are in propeller ( or tracking ) phases . .
And you have already written the first three sentences of the full article: the age of neutron star is an essential parameter , which is relevant to the physics of supernova explosion and thereafter the evolution of stars .
however , it is still a big problem now to determine generally an exact value of age ( except the crab pulsar ) .
it is a conventional and convenient way to obtain the age for rotation - powered neutron stars by equalizing the energy lose rate of spindown to that of magnetodipole radiation , assuming that the inclination angle between magnetic and rotational axes is @xmath0 ( e.g. , manchester & taylor 1977 ) ..
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the conclusion keeps quantitatively for any @xmath1 , as long as the braking torques due to magnetodipole radiation and the unipolar generator are combined ( xu & qiao 2001 ) .
the resultant age , the so - called characteristic age , is @xmath2 if the initial period @xmath3 is much smaller than the present period @xmath4 .
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9,907 |
Suppose that you have an abstract for a scientific paper: we compute haar ensemble averages of ratios of random characteristic polynomials for the classical lie groups @xmath0 , @xmath1 , and @xmath2 . to that end , we start from the clifford - weyl algebra in its canonical realization on the complex @xmath3 of holomorphic differential forms for a @xmath4-vector space @xmath5 . from it
we construct the fock representation of an orthosymplectic lie superalgebra @xmath6 associated to @xmath5 .
particular attention is paid to defining howe s oscillator semigroup and the representation that partially exponentiates the lie algebra representation of @xmath7 . in the process , by pushing the semigroup representation to its boundary and arguing by continuity , we provide a construction of the shale - weil - segal representation of the metaplectic group . to deal with a product of @xmath8 ratios of characteristic polynomials , we let @xmath9 where @xmath10 is equipped with the standard @xmath11-representation , and focus on the subspace @xmath12 of @xmath11-equivariant forms .
by howe duality , this is a highest - weight irreducible representation of the centralizer @xmath13 of @xmath14 in @xmath6 .
we identify the @xmath11-haar expectation of @xmath8 ratios with the character of this @xmath15-representation , which we show to be uniquely determined by analyticity , weyl group invariance , certain weight constraints and a system of differential equations coming from the laplace - casimir invariants of @xmath13 .
we find an explicit solution to the problem posed by all these conditions . in this way
, we prove that the said haar expectations are expressed by a weyl - type character formula for _ all _ integers @xmath16 .
this completes earlier work of conrey , farmer , and zirnbauer for the case of @xmath17 . .
And you have already written the first three sentences of the full article: [ varying ] in this article we derive an explicit formula for the average @xmath18 where @xmath11 is one of the classical compact lie groups @xmath19 , @xmath1 , or @xmath20 equipped with haar measure @xmath21 of unit mass @xmath22 and @xmath23 depends on a set of complex parameters @xmath24 , which satisfy @xmath25 for all @xmath26 .
the case of @xmath27 is handled in @xcite .
note that @xmath28 with @xmath29 ..
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this means that @xmath30 is a product of ratios of characteristic polynomials , which explains the title of the article .
the haar average @xmath31 can be regarded as the ( numerical part of the ) character of an irreducible representation of a lie supergroup @xmath32 restricted to a suitable subset of a maximal torus of @xmath33 .
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9,908 |
Suppose that you have an abstract for a scientific paper: we review the construction of a @xmath0-analogue of the gaussian measure .
we apply that construction to obtain a @xmath0-analogue of feynman integrals and to compute explicitly an example of such integrals . .
And you have already written the first three sentences of the full article: the main goal of this note is to provide a gentle introduction to the theory of feynman - jackson integrals , and to compute an example of such integrals as explicitly as possible . roughly speaking feynman - jackson integrals are the analogue in @xmath0-calculus of feynman integrals .
the name of jackson is included since integration in @xmath0-calculus was introduced by f.h .
jackson , see @xcite and @xcite ..
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our computations are done in the one dimensional setting .
extending our concepts to higher dimensions , in particular to infinite dimensions , is the main problem in this subject . in principle
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9,909 |
Suppose that you have an abstract for a scientific paper: we present here an efficient method which systematically reduces the rank of the augmented space and thereby helps to implement augmented space recursion for any real calculation .
our method is based on the symmetry of the hamiltonian in the augmented space and keeping recursion basis vectors in the irreducible subspace of the hilbert space .
@xmath0 # 1 2\ { r } # 1 # 1 .
And you have already written the first three sentences of the full article: in a series of earlier communications @xcite we have proposed the augmented space recursion ( asr ) as an efficient computational technique for the calculation of configuration averaged electronic properties of random binary alloys .
the method is a combination of the augmented space formalism @xcite and the recursion method of haydock @xcite .
when coupled with the local density functional approximation based tight - binding linearized muffin - tin orbital @xcite it provides a first - principles determination of electronic structure and total energy calculations for disordered alloys ..
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effects such as short - ranged ordering and local lattice distortions due to size mismatch of the constituent atoms can very easily be incorporated in the methodology @xcite . recently
the method has been applied to study dispersion and line widths for phonons in disordered alloys . since recursion can take into account disorder in beyond nearest - neighbour force constants as well as large environmental effects , this application was a step forward in the theory of phonons in disordered alloys @xcite .
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9,910 |
Suppose that you have an abstract for a scientific paper: a stochastic genetic model for biological aging is introduced bridging the gap between the bit - string penna model and the pletcher - neuhauser approach .
the phenomenon of exponentially increasing mortality function at intermediate ages and its deceleration at advanced ages is reproduced for both the evolutionary steady - state population and the genetically homogeneous individuals .
: biological aging ; mortality ; penna model . .
And you have already written the first three sentences of the full article: the problem of biological aging has attracted much attention in recent years . based on the data of human demography and experiments of other living organisms , many important phenomena of longevity have been found @xcite .
for instance , the gompertz law was observed for intermediate ages , that is , the mortality function increases exponentially with age , while at old ages the mortality was found to decelerate or level off , and even decline for some organisms like flies , worms , and yeast @xcite . to reproduce and explain these phenomena , various models of senescence
have been proposed , with genetic or nongenetic mechanisms @xcite . among them , the one widely used by physicists is the penna model @xcite , where one computer word is used to represent the inherited genome of one individual and each bit of the word corresponds to one age of the individual lifetime ..
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a bit set to one represents a deleterious mutation and the suffering from an inherited disease from this age on , and the individual will die if the accumulation of these set bits exceeds a threshold .
although the penna model has been well applied to many problems related to biological aging @xcite , there exists an important flaw in this model as pointed out by pletcher and neuhauser very recently @xcite .
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9,911 |
Suppose that you have an abstract for a scientific paper: the stellar sites and the complete mechanism of @xmath0-process nucleosynthesis are still unresolved issues . from consideration of the observed abundances in metal - poor stars
, it is proposed that the production of the heavy @xmath0-process nuclei ( @xmath0-nuclei with mass numbers @xmath1 ) is not related to the production of the fe group elements or of the elements with lower atomic numbers : na , mg , al , si , ca , sc , and ti . this requires that the production of the heavy @xmath0-nuclei not occur in supernovae with extended shell structure , but be associated with either bare neutron stars or type ii supernovae ( sne ii ) in the mass range @xmath2 .
from the observations of stars with [ fe / h ] @xmath3 but with high abundances of @xmath0-elements , it is clear that these @xmath0-process enrichments can not represent the composition of the interstellar medium from which the stars were formed , but must represent very local contamination from binary companions .
further evidence for very high enrichments of @xmath4-process elements in metal - poor stars also requires binary systems for explanation .
we propose that the accretion - induced collapse ( aic ) of a white dwarf into a neutron star in a binary system may be associated with the production of the heavy @xmath0-nuclei and may provide occasional coupling of high @xmath0-process and high @xmath4-process enrichments in the envelopes of low - mass stars with low [ fe / h ] .
if we assume that the bulk of the heavy @xmath0-nuclei are produced in aic events , then these events would have produced @xmath5 neutron stars in the galaxy .
a much larger number of white dwarf binaries would have resulted from the evolution of other binary systems .
the aic scenario removes the assignment in our earlier model that sne ii provide the bulk of the heavy @xmath0-nuclei and relegates @xmath0-process production in sne ii to the light @xmath0-nuclei with @xmath6 .
this new assignment removes the requirement in our earlier model that most sne ii....
And you have already written the first three sentences of the full article: in this paper we try to establish the intrinsic characteristics of the stellar sources for the heavy @xmath0-process nuclei ( @xmath0-nuclei with mass numbers @xmath7 corresponding to the elements ba and above ) using aspects of a phenomenological model presented earlier ( wasserburg & qian 2000 ; qian & wasserburg 2001b , 2002 ) . the bulk of the light @xmath0-nuclei ( with @xmath6 ) appear to have different sources from those for the heavy @xmath0-nuclei ( wasserburg , busso , & gallino 1996 ) and are not extensively discussed here . from the observational data on metal - poor ( i.e. , low [ fe / h ] ) stars
, we will show that the heavy @xmath0-nuclei are produced with only some coproduction of the light @xmath0-elements such as sr , y , and zr , but without any coproduction of the elements from na to zn ( including fe ) .
we argue that supernovae with extended shell structure can not be the source for the heavy @xmath0-nuclei . instead ,.
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these nuclei must be produced during the formation of an essentially bare neutron star .
such a state may result from a low - mass ( @xmath8@xmath9 ) type ii supernova ( sn ii ) or from the accretion - induced collapse ( aic ) of a white dwarf into a neutron star in a binary system .
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9,912 |
Suppose that you have an abstract for a scientific paper: mid - infrared spectra of 65 t tauri stars ( tts ) taken with the infrared spectrograph ( irs ) on board the _ spitzer space telescope _ are modeled using populations of optically thin dust at two temperatures to probe the radial variation in dust composition in the uppermost layers of protoplanetary disks .
most spectra with narrow emission features associated with crystalline silicates require mg - rich minerals and silica , but a very small number suggest other components .
spectra indicating large amounts of enstatite at higher temperatures ( 400 - 500k ) also require crystalline silicates , either enstatite or forsterite , at temperatures lower ( 100 - 200k ) than those required for spectra showing high abundance of other crystalline silicates .
a few spectra show 10 @xmath0 complexes of very small equivalent width .
they are fit well using abundant crystalline silicates but very few large grains , inconsistent with the expectation that low peak - to - continuum ratio of the 10 @xmath0 complex always indicates grain growth .
most spectra in our sample are fit well without using the opacities of large crystalline silicate grains .
if large grains grow by agglomeration of submicron grains of all dust types , the amorphous silicate components of these aggregates must typically be more abundant than the crystalline silicate components .
we also find that the more there is of one crystalline dust species , the more there is of the others .
this suggests that crystalline silicates are processed directly from amorphous silicates , whether by evaporation of the amorphous grains and condensation in chemical equilibrium or by annealing of the amorphous precursor grains .
this also suggests that neither forsterite , enstatite , nor silica are intermediate steps along the way to producing either of the other two for the majority of the crystalline dust produced .
crystalline silicate abundance is correlated tightly with disk geometry , in the sense of higher crystallinity accompanying more....
And you have already written the first three sentences of the full article: comets are thought to be largely unaltered reservoirs of leftover material from the primordial mixture of dust in the solar nebula orbiting the newly - formed sun ( e.g. , * ? ? ?
spectral observations of comet hale - bopp by @xcite using the _ infrared space observatory _ ( _ iso _ ; * ? ? ?
* ) allowed for detailed spectral models over a wide range of wavelengths @xcite . the amorphous dust of pyroxene ( [ mg , fe]sio@xmath1 ) or olivine ( [ mg , fe]@xmath2sio@xmath3 ) stoichiometry ( henceforth , `` amorphous pyroxene '' or `` amorphous olivine '' , respectively ) was found to require a stoichiometric ratio of magnesium to iron of about unity , being relatively iron - rich @xcite ; the crystalline pyroxene must be iron - poor , as it is cooler @xcite ; and the larger grains must be porous , fluffy aggregates of smaller grains @xcite ..
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interplanetary dust particles ( idps ; * ? ? ?
* ) , believed to originate from comets , were often found to be highly porous aggregates of mg - rich crystalline silicate dust , having qualities very similar to those inferred from comet spectra and spectra of young stellar objects ( ysos ; systems in the process of forming stars and planets ) . using increasingly powerful telescopes and sensitive detectors ,
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9,913 |
Suppose that you have an abstract for a scientific paper: topological objects can influence each other if the underlying homotopy groups are non - abelian . under such circumstances ,
the topological charge of each individual object is no longer a conserved quantity and can be transformed to each other . yet
, we can identify the conservation law by considering the back - action of topological influence .
we develop a general theory of topological influence and back - action based on the commutators of the underlying homotopy groups . in the case of the topological influence of a half - quantum vortex on a point defect , we point out that the topological back - action from the point defect is a twisting of the vortex .
the total twist of the vortex line compensates for the change in the point - defect charge to conserve the total charge .
we use this theory to classify charge transfers in condensed matter systems and show that a non - abelian charge transfer can be realized in a spin-2 bose - einstein condensate . .
And you have already written the first three sentences of the full article: topological excitations are the hallmark of symmetry broken systems , such as liquid crystals @xcite , superfluid helium systems @xcite , and ultracold atomic gases @xcite .
they appear as spatial variations of order parameters with a topological charge .
examples include a vortex ( line defect ) , a point defect , and a skyrmion ..
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the topological excitations arise as a result of the spontaneous symmetry breaking of the system and their existence is determined by the broken symmetry . to characterize the broken symmetry of a given order parameter @xmath0
, we introduce a symmetry group @xmath1 whose action @xmath2 @xmath3 does not change the energy of system .
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9,914 |
Suppose that you have an abstract for a scientific paper: it is generally understood that fourier s law does not describe ballistic phonon transport , which is important when the length of a material is similar to the phonon mean - free - path . using an approach adapted from electron transport ,
we demonstrate that fourier s law and the heat equation _ do _ capture ballistic effects , including temperature jumps at ideal contacts , and are thus applicable on all length scales .
local thermal equilibrium is not assumed , because allowing the phonon distribution to be out - of - equilibrium is important for ballistic and quasi - ballistic transport .
the key to including the non - equilibrium nature of the phonon population is to apply the proper boundary conditions to the heat equation .
simple analytical solutions are derived , showing that _
i ) _ the magnitude of the temperature jumps is simply related to the material properties and _ ii ) _ the observation of reduced apparent thermal conductivity physically stems from a reduction in the temperature gradient and not from a reduction in actual thermal conductivity .
we demonstrate how our approach , equivalent to fourier s law , easily reproduces results of the boltzmann transport equation , in all transport regimes , even when using a full phonon dispersion and mean - free - path distribution . .
And you have already written the first three sentences of the full article: thermal transport at the nanoscale is a problem of great fundamental and practical interest @xcite .
figure [ fig1 ] shows the temperature profiles across silicon films of varying length ( @xmath0 ) , as computed by the phonon boltzmann transport equation ( bte ) @xcite
. the temperature jumps at the interfaces with the two ideal , reflectionless contacts are characteristic features of quasi - ballistic phonon transport , and are commonly observed @xcite in physically - detailed modeling ( such as monte carlo simulations@xcite , molecular dynamics @xcite , or solutions of the phonon bte @xcite ) . in practical situations ,.
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the routine analysis of nanoscale heat transport phenomena , including ballistic effects , has been limited by the high computational demand of rigorous simulations .
simple , accurate and physically transparent models that provide physical insight could help in understanding the results of detailed simulations , as well as the analysis of experiments .
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9,915 |
Suppose that you have an abstract for a scientific paper: the hyperelliptic curve cryptography is based on the arithmetic in the jacobian of a curve . in classical mechanics
well - known cryptographic algorithms and protocols can be very useful for construct auto bcklund transformations , discretization of continuous flows and study of integrable systems with higher order integrals of motion .
we consider application of a standard generic divisor doubling for construction of new auto bcklund transformations for the lagrange top and hnon - heiles system . .
And you have already written the first three sentences of the full article: for many integrable by quadratures dynamical systems in holonomic and nonholonomic mechanics the generic level set of integrals of motion can be related to the jacobian of some hyperelliptic curve @xcite .
it allows us to study symmetries of integrals of motion using group operations in this jacobian [ add - jac ] d+ d=dd = d , where @xmath0 and @xmath1 are reduced divisors , @xmath2 and @xmath3 $ ] denote addition and scalar multiplication by an integer , respectively . in 1826 , abel made a great advance : he discovered an addition theorem of sweeping generality @xcite .
the main legacy of the abel theorem is the string of developments leading to our understanding of the picard variety , functor of points and divisor class group of an algebraic variety ..
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the history of these developments is rich and fascinating , and it is a significant part of the history of algebraic geometry , see article @xcite , which gives many precise references to the original sources and to the secondary literature .
in @xcite cantor proposed an algorithm for performing computations in jacobian groups of hyperelliptic curves which consists of two stages : composition stage which generally outputs an unreduced divisor , and reduction stage which transforms the unreduced divisor into the unique reduced divisor .
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9,916 |
Suppose that you have an abstract for a scientific paper: in the coherent electron cooling , the modern hadron beam cooling technique , each hadron receives an individual kick from the electric field of the amplified electron density perturbation created in the modulator by this hadron in a co - propagating electron beam .
we developed a method for computing the dynamics of these density perturbations in an infinite electron plasma with any equilibrium velocity distribution a possible model for the modulator .
we derived analytical expressions for the dynamics of the density perturbations in the fourier - laplace domain for a variety of 1d , 2d , and 3d equilibrium distributions of the electron beam . to obtain the space - time dynamics , we employed the fast fourier transform ( fft ) algorithm .
we also found an analytical solution in the space - time domain for the 1d cauchy equilibrium distribution , which serves as a benchmark for our general approach based on numerical evaluation of the integral transforms and as a fast alternative to the numerical computations .
we tested the method for various distributions and initial conditions . .
And you have already written the first three sentences of the full article: a few of years ago , a novel hadron beam cooling technique capable to deal with the accelerators operating in the range of few tevs , the coherent electron cooling ( cec ) , was proposed @xcite .
currently , a test facility is under construction at brookhaven national laboratory . for the present status of the developments of the machine
, we refer to @xcite ..
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the cec is the modern realization of the stochastic electron cooling , wherein the electron beam serves as a pick - up and a kicker .
it records the information about the hadron beam via the electron density perturbations resulting from the shielding of the hadrons .
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9,917 |
Suppose that you have an abstract for a scientific paper: in the search for vacuum solutions , with or without a cosmological constant , @xmath0 , of the einstein field equations of petrov type n with twisting principal null directions , the cr structures to describe the parameter space for a congruence of such null vectors provide a very useful tool .
a work of hill , lewandowski and nurowski has given a good foundation for this , reducing the field equations to a set of differential equations for two functions , one real , one complex , of three variables .
under the assumption of the existence of one killing vector , the ( infinite - dimensional ) classical symmetries of those equations are determined and group - invariant solutions are considered .
this results in a single ode of the third order which may easily be reduced to one of the second order .
a one - parameter class of power series solutions , @xmath1 , of this second - order equation is realized , holomorphic in a neighborhood of the origin and behaving asymptotically as a simple quadratic function plus lower - order terms for large values of @xmath2 , which constitutes new solutions of the twisting type n problem .
the solution found by leroy , and also by nurowski , is shown to be a special case in this class .
cartan s method for determining equivalence of cr manifolds is used to show that this class is indeed much more general .
in addition , for a special choice of a parameter , this ode may be integrated once , to provide a first - order abel equation .
it can also determine new solutions to the field equations although no general solution has yet been found for it . .
And you have already written the first three sentences of the full article: the search for general classes of solutions of the einstein equations that either have pure vacuum for their source or a non - zero cosmological constant , that are of petrov type n , and have principal null rays with non - zero twist has been continuing for a very long time now .
we will use the ( relatively common ) nomenclature `` einstein spaces '' for solutions with this sort of a source , i.e. , either the pure vacuum or that vacuum with a non - zero cosmological constant , @xmath0 , appended to it .
with this idea firmly in mind , there are only two solutions known so far for twisting type n einstein spaces : the one described by i. hauser @xcite , which has @xmath3 , and the one by j. leroy @xcite , with a non - zero value for @xmath0 , but which in the limit as @xmath4 degenerates to a flat solution , rather than one of type n. because of the apparent difficulty of the problem , many different approaches have been used to attempt the finding of such a solution . with a requirement of one or more killing vectors.
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, the problem can be reduced to the solution of a single , nonlinear ode , which has been produced in several forms by different authors @xcite ; nonetheless this approach has produced no new solutions .
looking at the problem as a reduction from complex - valued manifolds via plebaski s hyperheavenly equation @xcite has produced no new solutions @xcite .
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9,918 |
Suppose that you have an abstract for a scientific paper: we have developed fft beamforming techniques for the chime radio telescope , to search for and localize the astrophysical signals from fast radio bursts ( frbs ) over a large instantaneous field - of - view ( fov ) while maintaining the full angular resolution of chime .
we implement a hybrid beamforming pipeline in a gpu correlator , synthesizing 256 fft - formed beams in the north - south direction by four formed beams along east - west via exact phasing , tiling a sky area of @xmath0 square degrees . a zero - padding approximation is employed to improve chromatic beam alignment across the wide bandwidth of 400 to 800mhz .
we up - channelize the data in order to achieve fine spectral resolution of @xmath124khz and time cadence of 0.983ms , desirable for detecting transient and dispersed signals such as those from frbs . .
And you have already written the first three sentences of the full article: the canadian hydrogen intensity mapping experiment ( chime ) is a radio telescope currently being constructed at the dominion radio astrophysical observatory ( drao ) in penticton , bc , canada @xcite .
chime is a transit telescope with no moving parts , composed of four cylindrical reflecting surfaces , each 100 m in length north - south ( n - s ) and 20 m wide east - west ( e - w ) . on each of the four focal lines
is a linear array of 256 dual polarization antennas with a spacing of 0.3048 m ..
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this geometry provides an extremely wide effective fov of @xmath2120@xmath3 in n - s and [email protected]@xmath3 ( frequency dependent ) in e - w , that is , a primary beam size of @xmath0 square degrees .
chime is expected to be operational in 2017 .
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9,919 |
Suppose that you have an abstract for a scientific paper: using density - functional ab initio theoretical techniques , we study ( ga@xmath0in@xmath1)@xmath2o@xmath3 in both its equilibrium structures ( monoclinic @xmath4 and bixbyite ) and over the whole range of composition .
we establish that the alloy exhibits a large and temperature - independent miscibility gap . on the low-@xmath5 side ,
the favored phase is isostructural with @xmath4-ga@xmath2o@xmath3 ; on the high-@xmath5 side , it is isostructural with bixbyite in@xmath2o@xmath3 .
the miscibility gap opens between approximately 15% and 55% in content for the bixbyite alloy grown epitaxially on in@xmath2o@xmath3 , and 15% and 85% in content for the free - standing bixbyite alloy .
the gap , volume and band offsets to the parent compound also exhibit anomalies as function of @xmath5 .
specifically , the offsets in epitaxial conditions are predominantly type - b staggered , but have opposite signs in the two end - of - range phases . .
And you have already written the first three sentences of the full article: the group - iii sesquioxides ga@xmath2o@xmath3 and in@xmath2o@xmath3 are currently popular in basic materials science and technology for being , respectively , deep - uv large - breakdown and near - uv transparent - conducting materials . a natural development that can be envisaged
is the growth of a solid solution ( ga@xmath0in@xmath1)@xmath2o@xmath3 , typically ( but not necessarily ) epitaxially on the parent compounds .
this would enable one to combine and tune the functionalities of the two parent compounds , and to export the band - engineering and nanostructuration concepts well known in other semiconductor systems ( such as arsenides and nitrides ) to much higher absorption energies and breakdown voltages ..
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progress in this directions requires a knowledge of the miscibility , as well as the behavior of relevant properties ( gap , specific volume , band offsets , etc . ) , of a solid - solution substitutional alloy composed , in a given proportion , of the two parent materials . in this paper
we report the modeling of ( ga@xmath0in@xmath1)@xmath2o@xmath3 over the entire range of @xmath5 by ( mostly ) ab initio density - functional - theory techniques .
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9,920 |
Suppose that you have an abstract for a scientific paper: we present a study of the m83 cluster population , covering the disc of the galaxy between radii of 0.45 and 4.5 kpc .
we aim to probe the properties of the cluster population as a function of distance from the galactic centre .
we observe a net decline in cluster formation efficiency ( , i.e. the amount of star formation happening in bound clusters ) from about 26% in the inner region to 8% in the outer part of the galaxy .
the recovered values within different regions of m 83 follow the same versus star formation rate density relation observed for entire galaxies .
we also probe the initial cluster mass function ( icmf ) as a function of galactocentric distance .
we observe a significant steepening of the icmf in the outer regions ( from @xmath0 to @xmath1 ) and for the whole galactic cluster population ( slope of @xmath2 ) of m83 .
we show that this change of slope reflects a more fundamental change of the truncation mass at the high - mass end of the distribution .
this can be modelled as a schechter function of slope @xmath3 with an exponential cut - off mass ( @xmath4 ) that decreases significantly from the inner to the outer regions ( from 4.00 to @xmath5 ) while the galactic is @xmath6 .
the trends in and icmf are consistent with the observed radial decrease of the @xmath7 , hence in gas pressure .
as gas pressure declines cluster formation becomes less efficient .
we conclude that the host galaxy environment appears to regulate 1 ) the fraction of stars locked in clusters ; 2 ) the upper mass limit of the icmf , consistently described by a near - universal slope @xmath3 truncated at the high - mass end . [ firstpage ] galaxies : spiral galaxies : star clusters galaxies : star formation star : formation .
And you have already written the first three sentences of the full article: young star clusters are potentially bright , long lived , tracers of star formation within their host galaxies .
it is therefore of paramount importance to understand what governs the cluster formation process ( e.g. , * ? ? ?
* ) and how the host galactic environment may affect their formation and evolution ( e.g. , * ? ? ?.
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statistically we can describe the cluster formation as a stochastic process .
numerous works report of an initial cluster mass and luminosity function ( icmf and iclf , respectively ) being described with good approximation by a single power - law slope of index close to @xmath3 .
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9,921 |
Suppose that you have an abstract for a scientific paper: by h. strietz , 1975 , and g. czdli , 1996 , the complete lattice @xmath0 of all equivalences is four - generated , provided the size @xmath1 is an accessible cardinal .
results of i. chajda and g. czdli , 1996 , g. takch , 1996 , t. dolgos , 2015 , and j. kulin , 2016 , show that both the lattice @xmath2 of all quasiorders on @xmath3 and , for @xmath4 , the lattice @xmath5 of all transitive relations on @xmath3 have small generating sets . based on complicated earlier constructions ,
we derive some new results in a concise but not self - contained way . .
And you have already written the first three sentences of the full article: quasiorders , also known as preorders , on a set @xmath3 form a complete lattice @xmath2 .
so do the transitive relations on @xmath3 ; their complete lattice is denoted by @xmath5 .
similarly , @xmath0 will stand for the lattice of all equivalences on @xmath3 ..
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the natural involution , which maps a relation @xmath6 to its inverse , @xmath7 , is an automorhpism of each of the three lattices mentioned above .
if , besides arbitrary joins and meets , the involution is an operation of the structure , then we speak of the _ complete involution lattices _ @xmath2 and @xmath5 .
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9,922 |
Suppose that you have an abstract for a scientific paper: in the thermoelastic regime , photoacoustic sensing of optical absorption relies on conversion from light to acoustic energy via the coefficient of thermal expansion . in this work ,
we confront confront experimental measurements to theoretical predictions of nonlinear photoacoustic generation based on the dynamic variation of the coefficient of thermal expansion during the optical excitation of absorbers in aqueous solution .
the photoacoustic generation from solutions of organic dye and gold nanospheres ( with same optical densities ) , illuminated with 532 nm nanosecond pulses , was detected using a high frequency ultrasound transducer ( center frequency 20 mhz ) .
photoacoustic emission was observed with gold nanospheres at low fluence ( a few mj/@xmath0 ) for an equilibrium temperature around @xmath1 , where the linear photoacoustic effect in water vanishes , highlighting the nonlinear emission from the solution of nanospheres . under the same condition ,
no emission was observed with the absorbing organic dye . at a fixed fluence of 5 mj/@xmath0
, the photoacoustic amplitude was studied as a function of the equilibrium temperature from @xmath2 to @xmath3 . while the photoacoustic amplitude from the organic dye followed the coefficient of thermal expansion in water at the equilibrium temperature and vanished around @xmath1 , the photoacoustic amplitude from the gold nanospheres remained significant over the whole temperature range .
these experimental results are shown to be in qualitative agreement with theoretical calculations based on the nanoscale and nanosecond transient changes of the coefficient of thermal expansion of water around the gold nanospheres .
our results suggest that in the context of high frequency photoacoustic imaging , nanoparticles may be discriminated from molecular absorbers based on either the nonlinear fluence - dependence or the equilibrium temperature - dependence of the photoacoustic amplitude . .
And you have already written the first three sentences of the full article: photoacoustics has demonstrated optical contrast imaging in biological tissues at depth beyond 1 mm @xcite .
this non - invasive hybrid modality uses the conversion of transient illumination to ultrasound wave though thermoelastic expansion to detect optical absorption . besides the detection of endogenous photo - absorbers such as hemoglobin and melanin ,
the use of exogenous contrast agents has shown to provide functional and molecular information @xcite ..
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optical reporter agents in photoacoustics range from molecular agents to nanoparticles .
organic dyes like icg @xcite and methylene blue @xcite are of molecular agents and have already been used to enhance visualization of the circulatory system and its dynamic .
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9,923 |
Suppose that you have an abstract for a scientific paper: we investigate quantum phase transitions in ladders of spin @xmath0 particles by engineering suitable matrix product states for these ladders .
we take into account both discrete and continuous symmetries and provide general classes of such models .
we also study the behavior of entanglement between different neighboring sites near the transition point and show that quantum phase transitions in these systems are accompanied by divergences in derivatives of entanglement . .
And you have already written the first three sentences of the full article: the basic paradigm of many body physics is to use analytical and numerical tools to investigate the low - lying states and in particular the ground state properties of a system governed by a given hamiltonian . at very low temperatures , when thermal fluctuations are dominated by quantum fluctuations , quantum phase transitions can occur due to the change of character of the ground state @xcite .
what is exactly meant by `` character '' has been investigated in numerous works @xcite , @xcite , @xcite , especially in recent years after the discovery of exact measures @xcite of entanglement(purely quantum mechanical correlations ) .
for example , it has been a matter of debate whether a quantum phase transition is always accompanied by a divergence of some property in entanglement of the ground state wave function ..
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+ unfortunately , except for a few exactly solvable examples , the task of finding the exact ground state of a given hamiltonian is notoriously difficult . as always in dealing with difficult problems ,
one way round the difficulty is to investigate the inverse problem , that is to start from states with pre - determined properties and investigate quantum phase transitions which occur by smoothly changing some continuous parameters of these states .
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9,924 |
Suppose that you have an abstract for a scientific paper: we consider buch s rule for k - theory of the grassmannian , in the schur multiplicity - free cases classified by stembridge . using a result of knutson
, one sees that buch s coefficients are related to mbius inversion .
we give a direct combinatorial proof of this by considering the product expansion for grassmannian grothendieck polynomials .
we end with an extension to the multiplicity - free cases of thomas and yong . .
And you have already written the first three sentences of the full article: we consider the * grassmannian * @xmath0 . for a partition @xmath1 contained in a @xmath2 box ,
consider the path from the northeast corner to the southwest corner of the box that traces the partition .
for the standard flag ( @xmath3 ) , we define the * schubert variety * as @xmath4 we denote the * schubert class * in cohomology as @xmath5_h \in h^\star(gr_k { \mathbb{c}}^n)$ ] . the set @xmath6 forms a basis for @xmath7 , where @xmath8 for @xmath9 , and @xmath10 the littlewood - richardson coefficients ..
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this follows from the surjective homomorphism @xmath11 @xmath12 @xmath13 for schur functions @xmath14 .
the * mbius function @xmath15 * is defined recursively on a poset @xmath16 as the unique function satisfying @xmath17 the connection of this definition to k - classes is shown in @xcite .
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9,925 |
Suppose that you have an abstract for a scientific paper: we report on the quadrupling of the transition spectrum of an @xmath0 cooper - pair box ( cpb ) charge qubit in the @xmath1{ghz}$ ] frequency range .
the qubit was coupled to a quasi - lumped element al superconducting resonator and measured at a temperature of @xmath2{mk}$ ] .
we obtained good matches between the observed spectrum and the spectra calculated from a model hamiltonian containing two distinct low excitation energy two - level systems ( tls ) coupled to the cpb . in our model , each tls has a charge that tunnels between two sites in a local potential and induces a change in the cpb critical current . by fitting the model to the spectrum
, we have extracted microscopic parameters of the fluctuators including the well asymmetry , tunneling rate , and a surprisingly large fractional change ( @xmath3 ) in the critical current ( @xmath4{na}$ ] ) .
this large change is consistent with a josephson junction with a non - uniform tunnel barrier containing a few dominant conduction channels and a tls that modulates one of them . .
And you have already written the first three sentences of the full article: dissipation and dephasing from two - level systems ( tls ) are a serious problem in many superconducting qubits .
the aggregate effect of many weakly coupled fluctuators causes @xmath5 charge noise , broadband dielectric loss , and magnetic flux noise , as well as inhomogeneous broadening and decreased measurement fidelity in qubits.@xcite an individual tls quantum - coherently coupled to a qubit can typically be identified when it leads to a resolvable avoided crossing in the qubit spectrum .
such avoided level crossings have been observed in phase,@xcite flux,@xcite charge,@xcite quantronium,@xcite and transmon@xcite qubits . while qubit performance is typically severely degraded near such an avoided crossing,@xcite strong qubit - tls interactions.
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allow the microscopic details of the tls to be determined.@xcite coherent coupling to a long - lived tls also makes it possible to observe coherent oscillations between a qubit and a tls@xcite or use the tls as a quantum memory.@xcite two - level fluctuators in superconducting devices can be classified into three types charge , flux , or critical current depending on the nature of the interaction with the qubit .
the microscopic origin of charge and critical current fluctuators is believed to be impurity ions such as h@xcite or low coordination bonds in the amorphous dielectric used to build the devices . in phase and flux qubits
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9,926 |
Suppose that you have an abstract for a scientific paper: this fluid dynamics video submitted to the gallery of fluid motion shows a turbulent boundary layer developing under a 5 metre - long flat plate towed through water .
a stationary imaging system provides a unique view of the developing boundary layer as it would form over the hull of a ship or fuselage of an aircraft .
the towed plate permits visualisation of the zero - pressure - gradient turbulent boundary layer as it develops from the trip to a high reynolds number state ( @xmath0 ) .
an evolving large - scale coherent structure will appear almost stationary in this frame of reference .
the visualisations provide an unique view of the evolution of fundamental processes in the boundary layer ( such as interfacial bulging , entrainment , vortical motions , etc . ) . in the more traditional laboratory frame of reference , in which fluid
passes over a stationary body , it is difficult to observe the full evolution and lifetime of turbulent coherent structures .
an equivalent experiment in a wind / water - tunnel would require a camera and laser that moves with the flow , effectively ` chasing ' eddies as they advect downstream @xcite . .
And you have already written the first three sentences of the full article: the experiment is conducted in a tow - tank of length 60 m , width 1.8 m and depth 2 m. the plate is towed by a fully automated carriage capable of speeds up to @xmath1 ms@xmath2 .
the plate is 5.0 m long and 1.2 m wide with an elliptical leading edge .
the boundary layer formed on the bottom surface of the plate is tripped using a 1 mm diameter trip wire ..
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fluorescein is injected through a spanwise oriented slot located immediately downstream of the trip .
the developing boundary layer is then illuminated using a continuous 4 w argon - ion laser which has been fanned into a streamwise / wall - normal sheet .
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9,927 |
Suppose that you have an abstract for a scientific paper: the relativistic jets of ss433 are outstanding for their optical thermal radiation .
the radiation is produced by small clouds ( @xmath0 cm ) whose lifetime is about @xmath1 times larger than the gas - dynamical crushing time .
we show that the clouds reside in thermal and dynamical balance as long as they collisionally interact with the wind of the supercritical accretion disk .
the interaction is caused by the precessional movement of the jets and takes place only in the sweep - out zone . beyond the sweep - out zone the interaction ceases and optical jets just terminate
the cloud magnetic field amplified in course of movement through a medium could play a role in containing a cloud .
thus , the clue to the uniqueness of the optical jets of ss433 is thought to be their precessional movement , which provides an opportunity for collisional interaction of the clouds with the wind . .
And you have already written the first three sentences of the full article: since the discovery of jets in ss433 in 1978 , there has been discussion about their uniqueness . by now the zoo of various jets has enlarged .
there have already been detected hundreds relativistic jets of agns , low velocity jets of young stars and a dozen jets of compact stars .
jets of ss433 stand out among the others for they harbour cool clouds within the relativistic flow ..
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it is not clear , however , how the clouds could survive in the relativistic jets and be observed .
it is also worth mentioning , that the thermal fraction is likely to be dominant in the jets of ss433 . on the contrary
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9,928 |
Suppose that you have an abstract for a scientific paper: we report on the discovery of high - energy ( he ; @xmath0gev ) and very high - energy ( vhe ; @xmath1gev ) @xmath2-ray emission from the high - frequency - peaked bl lac object rbs0413 .
veritas , a ground - based @xmath2-ray observatory , detected vhe @xmath2 rays from rbs0413 with a statistical significance of 5.5 standard deviations ( @xmath3 ) and a @xmath2-ray flux of @xmath4 @xmath5 @xmath6 @xmath7 ( @xmath8 of the crab nebula flux ) above 250gev . the observed spectrum can be described by a power law with a photon index of @xmath9 .
contemporaneous observations with the large area telescope ( lat ) on the _ fermi _ gamma - ray space telescope detected he @xmath2 rays from rbs0413 with a statistical significance of more than @xmath10 , a power - law photon index of @xmath11 and a @xmath2-ray flux between 300mev and 300gev of ( @xmath12 ) @xmath13 10@xmath14 photons m@xmath15 s@xmath16 .
we present the results from _ fermi_-lat and veritas , including a spectral energy distribution modeling of the @xmath2-ray , quasi - simultaneous x - ray ( _ swift_-xrt ) , ultraviolet ( _ swift_-uvot ) and @xmath17-band optical ( mdm ) data .
we find that , if conditions close to equipartition are required , both the combined synchrotron self - compton / external - compton and the lepto - hadronic models are preferred over a pure synchrotron self - compton model . .
And you have already written the first three sentences of the full article: blazars are active galactic nuclei that have their jet axis oriented at a small angle with respect to the observer @xcite .
they are observationally classified as either flat - spectrum radio quasars ( fsrq ) or bl lacertae ( bl lac ) objects according to the broad line emission in their optical spectra .
recent studies interpreting the differing spectral high - energy ( he ) @xmath2-ray properties of the fsrqs and bl lacs based on physical mechanisms can be found in e.g. , @xcite ..
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blazars are known to emit non - thermal radiation characterized by a double - peaked spectral energy distribution ( sed ) .
the low - energy component , generally covering radio to uv / x - ray bands , is usually explained as due to synchrotron emission from relativistic electrons in the blazar jet .
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9,929 |
Suppose that you have an abstract for a scientific paper: we study steady - state properties of inelastic gases in two - dimensions in the presence of an energy source .
we generalize previous hydrodynamic treatments to situations where high and low density regions coexist .
the theoretical predictions compare well with numerical simulations in the nearly elastic limit .
it is also seen that the system can achieve a nonequilibrium steady - state with asymmetric velocity distributions , and we discuss the conditions under which such situations occur .
pacs numbers : 05.20.dd , 47.50.+d , 81.35.+k 2 .
And you have already written the first three sentences of the full article: granular materials such as sand and powders have generated much interest of late .
such an ensemble of particles with macroscopic size is challenging since it may behave as a solid , a liquid or a gas .
size separation , pattern formation , avalanches , compaction and convection are just a few examples of the wide array of observed phenomena@xcite ..
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flow underlies most of these phenomena and therefore , theoretical studies so far focus on formulating a hydrodynamical description appropriate to sand@xcite .
these theories , stemming from the boltzmann equation , depend on the assumption of `` molecular chaos '' , _
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9,930 |
Suppose that you have an abstract for a scientific paper: we study the thermodynamic and gravitational stability of kerr anti - de sitter black holes in five and higher dimensions .
we show , in the case of equal rotation parameters , @xmath0 , that the kerr - ads background metrics become stable , both thermodynamically and gravitationally , when the rotation parameters @xmath1 take values comparable to the ads curvature radius . in turn
, a kerr - ads black hole can be in thermal equilibrium with the thermal radiation around it only when the rotation parameters become not significantly smaller than the ads curvature radius .
we also find with equal rotation parameters that a kerr - ads black hole is thermodynamically favored against the existence of a thermal ads space , while the opposite behavior is observed in the case of a single non - zero rotation parameter .
the five dimensional case is however different and also special in that there is no high temperature thermal ads phase regardless of the choice of rotation parameters .
we also verify that at fixed entropy , the temperature of a rotating black hole is always bounded above by that of a non - rotating black hole , in four and five dimensions , but not in six and more dimensions ( especially , when the entropy approaches zero or the minimum of entropy does not correspond to the minimum of temperature ) . in this last context ,
the six dimensional case is marginal . .
And you have already written the first three sentences of the full article: black holes are perhaps the most tantalizing objects in general relativity . recently
, the study of black holes in a background anti - de sitter spacetime has been well motivated from developments in string / m - theory , which naturally incorporate black holes as solitonic d - branes , or simply branes as the higher - dimensional progenitors of black holes .
an intriguing example of this is the conjectured duality @xcite between string theory on @xmath2 background and @xmath3 super yang - mills theory in four dimensions , and in particular , witten s interpretation @xcite of the hawking - page phase transition between thermal ads and ads black hole @xcite as the confinement - deconfinement phases of the dual gauge theory defined on the asymptotic boundaries of the ads space ..
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much effort has been put into the weak ads gravity regime , analyzing the implications of ads black holes on dual ( gauge ) theories at non - zero temperature , using the conjectured ads / cft correspondence . in this context ,
the most interesting black hole solutions are presumably the five dimensional kerr - ads solutions for a stationary black hole @xcite .
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9,931 |
Suppose that you have an abstract for a scientific paper: recent _ chandra _ and _ xmm _ observations of distant quasars have shown strong local ( @xmath0 ) x - ray absorption lines from highly ionized gas , primarily he - like oxygen .
the nature of these x - ray absorbers , i.e. , whether they are part of the hot gas associated with the milky way or part of the intragroup medium in the local group , remains a puzzle due to the uncertainties in the distance .
we present in this paper a survey of 20 agns with _
chandra _ and _ xmm _ archival data .
about 40% of the targets show local he@xmath1 absorption with column densities around @xmath2 ; in particular , absorption is present in all the high quality spectra .
we estimate that the sky covering fraction of this -absorbing gas is at least 63% , at 90% confidence , and likely to be unity given enough high - quality spectra . based on ( 1 ) the expected number of absorbers along sight lines toward distant agns , ( 2 ) joint analysis with x - ray emission measurements , and ( 3 ) mass estimation , we argue that the observed x - ray absorbers are part of the hot gas associated with our galaxy .
future observations will significantly improve our understanding of the covering fraction and provide robust test of this result .
nn .
And you have already written the first three sentences of the full article: recently , a number of _ chandra _ and _ xmm_-newton observations of quasars have shown local ( @xmath3 ) x - ray absorption lines ( @xcite ) .
these background quasars are among the brightest extragalactic x - ray sources in the sky and some of them were used as calibration targets .
the typical high ionic column densities of these x - ray absorbers ( @xmath4 @xmath5 ) imply the existence of large amounts of hot gas with temperatures around @xmath6 k. recent ultraviolet observations of the local high velocity absorbers also reveal such hot gas but at lower temperatures ( see ..
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e.g. , @xcite ) .
given the spectral resolution of _ chandra _ and _ xmm_-newton , it is still unclear where this hot gas is located : in the interstellar medium , in the galactic halo , or in the local group as the intragroup medium . in sharp contrast , so far only four targets were reported showing intervening absorption systems ( @xmath7 ) , all with low ion column densities .
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9,932 |
Suppose that you have an abstract for a scientific paper: we use local quark - hadron duality to estimate the purely nonperturbative soft contribution to the @xmath0 form factors .
our results are in agreement with existing experimental data .
we predict that the ratio @xmath1 is small for all accessible @xmath2 , in contrast to the pqcd expectations that @xmath3 .
-48pt -0.5 cm -0.5 cm cebaf - th-95 - 11 * quark - hadron duality and @xmath0 form factors * v.m . belyaev@xmath4 _ continuous electron beam accelerator facility + newport news , va 23606 , usa _ a.v . radyushkin + _ physics department , old dominion university , _ + _ norfolk , va 23529 , usa _ + _ and _ + _ continuous electron beam accelerator facility , _ + _ newport news , va 23606 , usa _ .
And you have already written the first three sentences of the full article: basically , there are two competing explanations of the experimentally observed power - law behaviour of elastic hadronic form factors : hard scattering @xcite and the feynman mechanism @xcite . at sufficiently large momentum transfer ,
the feynman mechanism contribution is dominated by configurations in which one of the quarks carries almost all the momentum of the hadron . in qcd , this results in an extra @xmath5 suppression compared to the hard scattering term generated by the valence configurations with small transverse sizes and finite light - cone fractions of the total hadron momentum carried by each valence quark .
the hard term , which eventually dominates , can be written in a factorized form @xcite,@xcite,@xcite , as a product of the perturbatively calculable hard scattering amplitude and two distribution amplitudes accumulating the necessary nonperturbative information . however , this mechanism involves exchange of virtual gluons , each exchange bringing in a suppression factor @xmath6 ..
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hence , to describe existing data by the hard contribution alone , one should intentionally increase the magnitude of the hard scattering term by using distribution amplitudes with a peculiar `` humped '' profile @xcite . in this case
, passive quarks carry a small fraction of the hadron momentum and , as pointed out in ref.@xcite , the `` hard '' scattering subprocess , even at rather large momentum transfers @xmath7 , is dominated , in fact , by very small gluon virtualities .
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Suppose that you have an abstract for a scientific paper: we investigate the properties of chain recurrent , chain transitive , and chain mixing maps ( generalizations of the well - known notions of non - wandering , topologically transitive , and topologically mixing maps ) .
we describe the structure of chain transitive maps .
these notions of recurrence are defined using @xmath0-chains , and the minimal lengths of these @xmath0-chains give a way to measure recurrence time ( chain recurrence and chain mixing times ) .
we give upper and lower bounds for these recurrence times and relate the chain mixing time to topological entropy . .
And you have already written the first three sentences of the full article: pseudo - orbits , or @xmath0-chains , are important tools for investigating properties of discrete dynamical systems .
these @xmath0-chains detect recurrent and mixing behaviors that may not be evident by studying actual orbits .
however , what is missing from the definitions of terms such as chain recurrence , chain transitivity , and chain mixing is any information about the lengths of the recurrence or mixing times ..
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they also do not give fine detail about the `` dynamics '' of the @xmath0-chains .
let @xmath1 be a compact metric space and @xmath2 be a continuous map .
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Suppose that you have an abstract for a scientific paper: we study the conditions for persistent cooperation in an off - lattice model of mobile agents playing the prisoner s dilemma game with pure , unconditional strategies .
each agent has an exclusion radius @xmath0 that accounts for the population viscosity , and an interaction radius @xmath1 that defines the instantaneous contact network for the game dynamics .
we show that , differently from the @xmath2 case , the model with finite sized agents presents a coexistence phase with both cooperators and defectors , besides the two absorbing phases in which either cooperators or defectors dominate .
we provide , in addition , a geometric interpretation of the transitions between phases . in analogy with lattice models ,
the geometric percolation of the contact network ( i.e. , irrespective of the strategy ) enhances cooperation .
more importantly , we show that the percolation of defectors is an essential condition for their survival . differently from compact clusters of cooperators ,
isolated groups of defectors will eventually become extinct if not percolating , independently of their size . .
And you have already written the first three sentences of the full article: network reciprocity @xcite is a general mechanism responsible for the development of spatial correlations within a viscous population , opening the possibility of persistent cooperation .
several specific models have been proposed showing how these correlations are related to stable groups of cooperating individuals , whose bulk benefits of self - defense and mutual support outcompete the surface exploitation by defectors @xcite .
although actual experiments have been performed @xcite , most of our knowledge comes from these simple models . in particular , a prevailing characteristic in real systems and an important ingredient for cooperation is the heterogeneous contact in systems whose interactions are given by complex @xcite or diluted networks @xcite ..
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when we consider the prisoner s dilemma ( pd ) dynamics @xcite on a diluted lattice that , albeit heterogeneous , has only short range interactions , intermediate densities present an enhancement of cooperation @xcite and , in the presence of a small amount of noise , the optimal dilution is closely related to the ( random site ) percolation threshold for that lattice @xcite .
whatever the level of heterogeneity , the contact network topology may evolve in time .
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Suppose that you have an abstract for a scientific paper: we have obtained spectra of hii regions in the heavily obscured spiral galaxy maffei 2 .
the observations have allowed for a determination of the galactic extinction of this galaxy using a correlation between extinction and hydrogen column density observed among spirals .
the technique reveals that the optical depth of galactic dust at 1 @xmath0 m obscuring maffei 2 is @xmath1 , which implies that @xmath2 mag , significantly higher than observed for the giant elliptical maffei 1 despite its similar latitude . for comparison
, we apply the same technique to ic 342 , a neighbouring spiral to maffei 2 but with more moderate obscuration by galactic dust , owing to its higher galactic latitude . for this galaxy ,
we obtain @xmath3 , which agrees within errors with the value of @xmath4 derived from the reddening estimate of @xcite .
we therefore adopt the weighted mean of @xmath5 for the extinction of ic 342 , which implies that @xmath6 mag .
a new distance estimate for maffei 2 of @xmath7 mpc is obtained from a self - consistent tully - fisher relation in @xmath8 adjusted to the ngc 4258 maser zero - point . with our new measurement of @xmath9 , maffei 2
joins maffei 1 and ic 342 as one of three giant members of the nearby ic 342/maffei group of galaxies .
we present the revised properties of all three galaxies based on the most accurate extinction and distance estimates to date , accounting for shifts in the effective wavelengths of broadband filters as this effect can be significant for highly reddened galaxies .
the revised distances are consistent with what would be suspected for the hubble flow , making it highly unlikely that the galaxies interacted with the local group since the big bang . .
And you have already written the first three sentences of the full article: the spiral galaxy maffei 2 was first detected by paolo maffei in 1968 on a near - infrared schmidt plate @xcite .
recent @xmath8-band photometry of this galaxy reveals a large highly - inclined barred spiral of hubble type sbc with isophotes visible out to @xmath10 from the nucleus @xcite . if the galaxy lies within 2 - 6 mpc as suggested in previous studies @xcite , it must be among the dominant galaxies in our galactic neighbourhood , which raises the question of its dynamical role in the early evolution of the local group .
unfortunately , a precise distance to maffei 2 has remained elusive owing to the heavy obscuration by dust in the milky way disk associated with its low galactic latitude ( @xmath11 ) ..
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attempts to determine the galactic extinction have so far produced ambiguous results : @xcite derived a value of @xmath12 mag by comparing the nuclear spectrum with that of m31 , and estimated that the galaxy suffers more extinction than the giant elliptical maffei 1 by about 1 magnitude in @xmath13 .
however , a modern estimate of the reddening of maffei 1 has been measured by fingerhut et al .
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Suppose that you have an abstract for a scientific paper: we address numerical aspects of local quark - hadron duality using the example of the exactly solvable t hooft model , two - dimensional qcd with @xmath0 .
the primary focus of these studies is total semileptonic decay widths relevant for extracting @xmath1 and @xmath2 .
we compare the exact channel - by - channel sum of exclusive modes to the corresponding rates obtained in the standard @xmath3 expansion arising from the operator product expansion .
an impressive agreement sets in unexpectedly early , immediately after the threshold for the first hadronic excitation in the final state . yet even at higher energy release it is possible to discern the seeds of duality - violating oscillations .
we find the `` small velocity '' sum rules to be exceptionally well saturated already by the first excited state .
we also obtain a convincing degree of duality in the differential distributions and in an analogue of @xmath4 . finally , we discuss possible lessons for semileptonic decays of actual heavy quarks in qcd .
pacs numbers : 12.38.aw , 11.10.kk , 13.20.-v 15.2 true cm 22.0 true cm 0 cm 0 cm 0.15 true in 0.4 true in 0.25 true in .7ex
.7ex 255=255 by 60 255 by-60255 by jlab - thy-00 - 21 + und - hep-00-big05 richard f. lebed@xmath5 and nikolai g.
uraltsev@xmath6 + ( june , 2000 ) .
And you have already written the first three sentences of the full article: questions of how to compare hadronic observables to the apparent underlying fundamental theory of qcd lie at the heart of understanding the nature of strong interactions .
thirty years after its inception , qcd in @xmath7 spacetime dimensions still stubbornly refuses to admit a global solution .
the asymptotic freedom property of the theory permits the perturbative calculation of ( euclidean ) green functions involving large values of momentum transfer or energy release in terms of quarks and gluons , the fundamental objects of qcd ..
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but at lower scales one enters the nonperturbative regime , which not only invalidates ( or at least complicates ) the standard perturbative methods of field theory developed in qed , but also leads to a dramatic change in the physical spectrum of the theory . instead of quarks and gluons ,
only colorless hadrons are produced as asymptotic states in any process , even at arbitrarily large energy .
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Suppose that you have an abstract for a scientific paper: the _ distance - number _ of a graph @xmath0 is the minimum number of distinct edge - lengths over all straight - line drawings of @xmath0 in the plane .
this definition generalises many well - known concepts in combinatorial geometry .
we consider the distance - number of trees , graphs with no @xmath1-minor , complete bipartite graphs , complete graphs , and cartesian products .
our main results concern the distance - number of graphs with bounded degree .
we prove that @xmath2-vertex graphs with bounded maximum degree and bounded treewidth have distance - number in @xmath3 .
to conclude such a logarithmic upper bound , both the degree and the treewidth need to be bounded .
in particular , we construct graphs with treewidth @xmath4 and polynomial distance - number .
similarly , we prove that there exist graphs with maximum degree @xmath5 and arbitrarily large distance - number
. moreover , as @xmath6 increases the existential lower bound on the distance - number of @xmath6-regular graphs tends to @xmath7 . .
And you have already written the first three sentences of the full article: [ sec : intro ] this paper initiates the study of the minimum number of distinct edge - lengths in a drawing of a given graph is denoted by @xmath8 , and its edge set by @xmath9 . a graph with @xmath2 vertices , @xmath10 edges and maximum degree at
most @xmath6 is an @xmath2-vertex , @xmath10-edge , degree-@xmath6 graph .
a graph in which every vertex has degree @xmath6 is _.
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@xmath6-regular_. for @xmath11 , let @xmath12 $ ] be the subgraph of @xmath0 induced by @xmath13 , and let @xmath14 $ ] . for each vertex @xmath15 ,
let @xmath16 .
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Suppose that you have an abstract for a scientific paper: the recently - discovered `` ladder '' compound lacuo@xmath0 has been found to admit hole doping without altering its structure of coupled copper oxide ladders .
while susceptibility measurements on the parent compound suggest a spin gap and a spin - liquid state , nmr results indicate magnetic order at low temperatures .
these seemingly contradictory results may be reconciled if in fact the magnetic state is near the crossover from spin liquid to antiferromagnet , and we investigate this possibility . from a tight - binding fit to the valence lda bandstructure , we deduce that the strength of the interladder hopping term is approximately half that of intraladder hopping , showing that the material is three - dimensional in character .
a mean - field treatment of the insulating magnetic state gives a spin - liquid phase whose spin gap decreases with increasing interladder coupling , vanishing ( signalling a transition to the ordered phase ) at a value somewhat below that obtained for lacuo@xmath0 .
the introduction of an on - site repulsion term , @xmath1 , to the band scheme causes a transition to an antiferromagnetic insulator for rather small but finite values of @xmath1 , reflecting the predominance of ( one - dimensional ) ladder behavior , and an absence of any special nesting features . .
And you have already written the first three sentences of the full article: one of the interesting and challenging sub - fields of low - dimensional quantum magnetism which has emerged from the wealth of activity directed at improving the understanding of high - temperature superconductors is that of ladder systems @xcite . these consist of @xmath2 parallel , interacting chains of @xmath3 = ions , which can be considered as a spin ladder with @xmath2 legs , and rungs of @xmath2 - 1 bonds .
the ladders have only weak mutual interactions .
a combination of experimental and theoretical efforts has in the last few years produced significant advances in the realization and understanding of the properties of spin ladders , some of which are not at all intuitive ..
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ladder cuprates emerged first with the discovery by hiroi _
et al._@xcite that in the series of materials sr@xmath4cu@xmath5o@xmath6 it is possible to create two - dimensional , stoichiometric copper oxide planes of composition cu@xmath5 o@xmath6 by removing from the uniform cuo@xmath7 plane parallel , equally - spaced lines of oxygen atoms .
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Suppose that you have an abstract for a scientific paper: fission dynamics properties of the barcelona - catania - paris - madrid ( bcpm ) energy density functional are explored with mean field techniques .
potential energy surfaces as well as collective inertias relevant in the fission process are computed for several nuclei where experimental data exists .
inner and outer barrier heights as well as fission isomer excitation energies are reproduced quite well in all the cases .
the spontaneous fission half lives @xmath0 are also computed using the standard semiclasical approach and the results are compared with the experimental data . the experimental trend with mass
number is reasonably well reproduced over a range of 27 orders of magnitude .
however , the theoretical predictions suffer from large uncertainties when the quantities that enter the spontaneous fission half life formula are varied .
modifications of a few per cent in the pairing correlation strengths strongly modify the collective inertias with a large impact on the spontaneous fission lifetimes in all the nuclei considered .
encouraged by the quite satisfactory description of the trend of fission properties with mass number we explore the fission properties of the even - even uranium isotope chain from @xmath1u to @xmath2u .
very large lifetimes are found beyond a=256 with a peak at neutron number n=184 . .
And you have already written the first three sentences of the full article: fission is a physical phenomenon taking place in heavy atomic nuclei that leads to the disintegration of a parent nucleus into two or more emerging fragments .
it involves the evolution of the nucleus from its ground state to scission going through a variety of intrinsic shapes that cover a wide range of different intrinsic deformation parameters @xcite .
fission properties depend upon the competition between the surface energy term coming from the strong nuclear interaction and the coulomb repulsion and therefore they are often used as constraints and/or guidance to refine the parameters of effective nuclear interactions ..
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a typical example is the d1s parametrizaton of the gogny @xcite force with parameters fine tuned to reproduce the fission barrier of @xmath3pu @xcite .
more recently fission related constraints have been used with skyrme interactions to define the unedf1 parametrization @xcite .
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Suppose that you have an abstract for a scientific paper: this paper investigates the existence of positive solutions of a singular boundary value problem with negative exponent similar to standard emden fowler equation . a necessary and sufficient condition for the existence of @xmath0 $ ] positive solutions as well as @xmath1 $ ] positive solutions
is given by means of the method of lower and upper solutions with the schauder fixed point theorem .
= msam5 at 9pt = tibi at 10.4pt [ theo]*theorem * # 1#2 .
And you have already written the first three sentences of the full article: consider the singular boundary value problems for the emden
fowler equation @xmath2 & \alpha u(0)-\beta u'(0)=0,\quad \gamma u(1)+\delta u'(1)=0,\end{aligned}\ ] ] where @xmath3 and @xmath4 and may be singular at @xmath5 .
when @xmath6 , see @xcite for the result concerning the above problem ..
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when @xmath7 , @xcite shows the existence and uniqueness to ( 1 ) and ( 2 ) in the case of @xmath8 by means of the shooting method . for the following problem @xmath9 & \alpha u(0)-\beta u'(0)=0,\quad \gamma u(1)+\delta u'(1)=0,\end{aligned}\ ] ] where @xmath10 , @xmath11 and @xmath12
mao @xcite gave a sufficient and necessary condition when @xmath13 .
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Suppose that you have an abstract for a scientific paper: there is now unequivocal evidence that the jets in fr i radio galaxies are initially relativistic , decelerating flows . on the assumption that they are axisymmetric and intrinsically symmetrical ( a good approximation close to the nucleus )
, we can make models of their geometry , velocity , emissivity and field structure whose parameters can be determined by fitting to deep vla observations .
mass entrainment either from stellar mass loss within the jet volume or via a boundary layer at the jet surface is the most likely cause for deceleration .
this idea is quantitatively consistent with the velocity field and geometry inferred from kinematic modelling and the external gas density and pressure profiles derived from x - ray observations .
the jets must initially be very light , perhaps with an electron - positron composition . .
And you have already written the first three sentences of the full article: the morphological division of extragalactic radio sources into two classes introduced by @xcite has proved to be remarkably robust .
fanaroff & riley had already noted that the edge - brightened ( frii ) sources tend to have higher radio luminosities than the edge - darkened ( fri ) sources , but there is also a dependence on stellar luminosity of the host galaxy which makes the division even cleaner @xcite .
that said , the fri class is not homogeneous : examples of the range of structures are shown in fig ..
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[ fig : fris ] .
although almost all fri sources show jets on small scales , some appear to be confined to the nuclear regions ( e.g. 3c84 ; fig .
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Suppose that you have an abstract for a scientific paper: in the present paper we are concerned with a numerical algorithm for the approximation of the two - dimensional neural field equation with delay .
this algorithm was described in @xcite and @xcite .
we consider three numerical examples that have been analysed before by other authors and are directly connected with real world applications .
the main purposes are 1 ) to test the performance of the mentioned algorithm , by comparing the numerical results with those obtained by other authors ; 2 ) to analyse with more detail the properties of the solutions and take conclusions about their physical meaning . .
And you have already written the first three sentences of the full article: we are concerned about the numerical solution of the following integrodifferential equation : @xmath0 @xmath1 , \bar{x } \in \omega \subset { \mathbb{r}}^2,\ ] ] where the unknown @xmath2 is a continuous function @xmath3 \rightarrow { \mathbb{r}}$ ] , @xmath4 , @xmath5 and @xmath6 are given functions ; @xmath7 is a constant .
we search for a solution @xmath8 of this equation which satisfies the initial condition @xmath9 along with equation we will also consider @xmath10 @xmath1 , \quad \bar{x } \in \omega \subset { \mathbb{r}}^2,\ ] ] where @xmath11 is a delay , depending on the spatial variables . in the last case , the initial condition has the form @xmath12,\ ] ] where @xmath13 . by integrating both sides of with respect to time on @xmath14 $ ] ,
we obtain the volterra - fredholm integral equation : @xmath15 @xmath1 , \bar{x } \in \omega \subset { \mathbb{r}}^2.\ ] ] the existence and uniqueness of solution of equation was proved in @xcite , both in the case of a smooth and discontinuous function @xmath6 ..
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an analytical study of equation was carried out in @xcite , where the authors have addressed the problems of existence , uniqueness and stability of solutions .
when solving numerically equations of the forms and , they are often reduced to the form ; therefore we begin by discussing literature on computational methods for volterra - fredholm equations . starting with the one - dimensional case , without delay
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Suppose that you have an abstract for a scientific paper: we describe different physics topics which can be performed at the lhc using tagged intact protons , namely a better understanding of the pomeron structure in terms of quarks and gluons , and the serach for quartic anomalous couplings . .
And you have already written the first three sentences of the full article: in this section , we discuss potential measurements at the lhc that can constrain the pomeron structure . the pomeron structure in terms of quarks and gluons has been derived from qcd
fits at hera and at the tevatron and it is possible to probe this structure and the qcd evolution at the lhc in a completely new kinematical domain . the high energy and luminosity at the lhc allow the exploration of a completely new kinematical domain .
one can first probe if the pomeron is universal between @xmath0 and @xmath1 colliders , or in other other words , if we are sensitive to the same object at hera and the lhc ..
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the different diagrams of the processes that can be studied at the lhc are namely double pomeron exchange ( dpe ) production of dijets , of @xmath2jet , sensitive respectively to the gluon and quark contents of the pomeron , and the jet gap jet events .
all diagrams were included in the fpmc @xcite generator that was used for this analysis .
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Suppose that you have an abstract for a scientific paper: the outskirts of galaxies especially the very extended hi disks of galaxies are strongly affected by their local environment .
i highlight the giant 2x - hi disks of nearby galaxies ( m83 , ngc 3621 , and ngc 1512 ) , studied as part of the local volume hi survey ( lvhis ) , their kinematics and relation to xuv disks , signatures of tidal interactions and accretion events , the @xmath0 relation as well as the formation of tidal dwarf galaxies . - using multi - wavelength data , i create 3d visualisations of the gas and stars in galaxies , with the shape of their warped disks obtained through kinematic modelling of their hi velocity fields . .
And you have already written the first three sentences of the full article: to trace gas and stars in the outskirts of galaxy disks , we typically use hi mapping ( e.g. , ( * ? ? ?
* huchtmeier & bohnenstengel 1981 ) ; ( * ? ? ?
* koribalski & lpez - snchez 2009 ) ; ( * ? ? ?.
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* heald et al . 2011 ) ; ( * ? ? ?
* serra et al . 2012 ) ; ( * ? ? ?
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9,945 |
Suppose that you have an abstract for a scientific paper: we show that within any quantum stabilizer code there lurks a classical binary linear code with similar error - correcting capabilities , thereby demonstrating new connections between quantum codes and classical codes . using this result which applies to degenerate as well as nondegenerate codes
previously established necessary conditions for classical linear codes can be easily translated into necessary conditions for quantum stabilizer codes .
examples of specific consequences are : for a quantum channel subject to a @xmath0-fraction of errors , the best asymptotic capacity attainable by any stabilizer code can not exceed @xmath1 ; and , for the depolarizing channel with fidelity parameter @xmath0 , the best asymptotic capacity attainable by any stabilizer code can not exceed @xmath2 .
# 1 # 1*#1 * 1\{0,1 } .
And you have already written the first three sentences of the full article: the theory of error - correcting codes for classical information has been extensively studied for almost fifty years . a fundamental question in coding theory concerns
what _ capacity _ of information can be successfully transmitted through a noisy channel . call a code that maps @xmath3-bit inputs into @xmath4-bit codewords an @xmath5 code , and define its capacity to be @xmath6 . for any specific @xmath4-bit channel ,
let its _ capacity _ be the maximum capacity of all @xmath5 codes that successfully transmit information through it ..
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this capacity is often taken as an asymptotic limit as @xmath4 tends towards infinity .
we consider two basic kinds of @xmath4-bit noisy channels .
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Suppose that you have an abstract for a scientific paper: lie - integration is one of the most efficient algorithms for numerical integration of ordinary differential equations if .
the method is based on the computation of the taylor - coefficients of the solution as a set of recurrence relations . in this paper
we present these recurrence formulae for orbital elements and other integrals of motion for the planar @xmath0-body problem .
we show that if the reference frame is fixed to one of the bodies for instance to the sun in the case of the solar system , the higher order coefficients for all orbital elements and integrals of motion depend only on the mutual terms corresponding to the orbiting bodies . .
And you have already written the first three sentences of the full article: due to the lack of analytical solutions , numerical integration is required to solve the equations of motion of the gravitational @xmath0-body problem for almost any initial conditions for @xmath1 .
there are many textbooks with algorithms related to general purpose numerical integration of ordinary differential equations ( odes , see e.g. * ? ? ?
* for an introduction ) ..
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the method has many advantages : it is one of the most efficient methods if we consider long - term and high precision computations , adaptive forms can be implemented without losing computation time , roundoff errors are smaller than other algorithms , etc .
( see e.g. * ? ? ?
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Suppose that you have an abstract for a scientific paper: we present a stochastic two - population model that describes the migration and growth of semi - sedentary foragers and sedentary farmers along a river valley during the neolithic transition .
the main idea of this paper is that random migration and transition from sedentary to foraging way of life and backward is strongly coupled with the local crop production and the associated degradation of land .
we derive a non - linear integral equation for the population density coupled with the equations for the density of soil nutrients and crop production .
our model provides an explanation for the formation of human settlements along a river valley .
the numerical results show that the individual farmers have a tendency for aggregation and clustering .
we show that the large - scale pattern is a transient phenomenon which eventually disappears due to land degradation . .
And you have already written the first three sentences of the full article: the wave of colonization by migrating farmers and establishment of farming communities in europe between @xmath0 and @xmath1 bc is currently a topic of great interest in prehistoric archaeology , linguistics and anthropology ch , pr .
ammerman and cavalli - sforza developed a model for the expansion of farming as a demic diffusion which spread into europe in the form of wave of advance @xcite . using the radiocarbon dates
, they found that farmers spread at an average rate of about one kilometer a year ..
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interest in simulation and spatial modelling of spread of agriculture has been growing rapidly in the last decade , especially in the physics community @xcite .
one of the main reasons for this is that the geographical spread of population can be effectively described by the classical fisher - kpp equation and its various generalizations @xcite .
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Suppose that you have an abstract for a scientific paper: we report on a general method for the rapid production of quantum degenerate gases . using @xmath0yb
, we achieve an experimental cycle time as low as @xmath1s for the production of bose - einstein condensates ( becs ) of @xmath2 atoms .
while laser cooling to @xmath3k proceeds in a standard way , evaporative cooling is highly optimized by performing it in an optical trap that is dynamically shaped by utilizing the time - averaged potential of a single laser beam moving rapidly in one dimension .
we also produce large ( @xmath4 ) atom number becs and successfully model the evaporation dynamics over more than three orders of magnitude in phase space density .
our method provides a simple and general approach to solving the problem of long production times of quantum degenerate gases . .
And you have already written the first three sentences of the full article: the production of quantum degenerate gases has revolutionized the field of atomic physics .
such gases are now routinely used as a means towards understanding complex many - body quantum phenomena from the realms of condensed matter and nuclear physics @xcite . as atom sources with precisely controlled properties , these gases can also significantly advance applications such as atom interferometry @xcite and quantum information processing @xcite . while the production and measurement methods of quantum gas experiments are well established , the measurement rate remains substantially limited by the lack of a general method for rapid sample production .
cycle times for such experiments are dominated by the production time , typically tens of seconds , while the actual experiment on the prepared sample lasts for about a second before destructive measurement ..
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this separation of timescales is a severe impediment to the employment of quantum degenerate gases towards precision devices such as atomic clocks , inertial sensors and gravimeters @xcite .
bridging these timescales can significantly contribute to all classes of quantum gas explorations and applications , as most measurements rely on the statistics of results from many experimental iterations .
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Suppose that you have an abstract for a scientific paper: a new method to extract @xmath0 from high redshift intergalactic absorption is described , based on the distribution of heii ly@xmath1 optical depths in the voids in the ionization zone of quasars .
a preliminary estimate from recent hst - stis spectra of pks 1935 - 692 at @xmath2 gives @xmath3 ( 1-@xmath4 statistical errors , for a @xmath5cdm cosmology ) consistent with other estimates . .
And you have already written the first three sentences of the full article: in the last few years it has become possible to observe details of absorption by singly ionized helium .
the observations combine new information about the history of quasars , intergalactic gas , and structure formation .
early observations of the heii ly@xmath1 absorption spectral region included the quasars q0302 - 003 ( z=3.285 , jackobsen et al ..
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1994 , hs 1700 + 64 ( z=2.72 , davidsen et al . 1996 ) and pks 1935 - 692 ( z=3.18 tytler & jackobsen 1996 ) .
higher resolution ( ghrs ) observations of q0302 - 003 hogan , anderson & rugers 1997 and he 2347 - 4342 ( z=2.885 , reimers et al .
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Suppose that you have an abstract for a scientific paper: variations of the x - ray spectral slope have been found in many active galactic nuclei ( agn ) at moderate luminosities and redshifts , typically showing a `` softer when brighter '' behaviour .
however , similar studies are not usually performed for high - luminosity agns .
we present an analysis of the spectral variability based on a large sample of quasars in wide intervals of luminosity and redshift , measured at several different epochs , extracted from the fifth release of the xmm newton serendipitous source catalogue .
our analysis confirms a `` softer when brighter '' trend also for our sample , extending to high luminosity and redshift the general behaviour previously found .
these results can be understood in light of current spectral models , such as intrinsic variations of the x - ray primary radiation , or superposition with a constant reflection component . .
And you have already written the first three sentences of the full article: the spectral slope optical / uv variations in agns have been quantified by @xcite , by means of the _ spectral variability parameter _ @xmath0 , @xmath1 being the slope of the spectrum and @xmath2 its flux in the given band .
a positive value was found , which means that the spectrum is harder when the flux is higher .
+ however , in the x - ray band , the opposite behaviour has been found for individual sources , and very few systematic studies have been performed , e.g. @xcite , who found this trend for a sample of 10 nearby seyfert galaxies ..
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+ in our study we investigated the spectral variability of quasars , using the mexsas catalogue @xcite , created cross - matching the multi - epoch observations of the xmm - newton serendipitous source catalogue , data release 5 @xcite with two partially overlapping sloan digital sky survey catalogues , sdss - dr7q @xcite and sdss - dr12q @xcite , obtaining a catalogue of 7,837 x - ray observations of 2,700 quasar sources .
in order to study the spectral variability in the x - ray band , we redefine the spectral variability parameter in terms of the photon index @xmath3 , defined after @xmath4 .
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9,951 |
Suppose that you have an abstract for a scientific paper: steady state properties in the absorbing phase of the @xmath0 pair contact process ( pcp ) model are investigated .
it is shown that , in typical absorbing states ( reached by the system s dynamic rules ) , the density of isolated particles , @xmath1 , approaches a stationary value which depends on the annihilation probability ( @xmath2 ) ; the deviation from its natural value at criticality , @xmath3 , follows a power law : @xmath4 for @xmath5 .
monte carlo simulations yield @xmath6 .
a cluster approximation is developed for this model , qualitatively confirming the numerical results and predicting @xmath7 .
the singular behavior of the isolated particles density in the inactive phase is explained using a phenomenological approach . 2 .
And you have already written the first three sentences of the full article: in the simplest models undergoing absorbing state phase transitions in the directed percolation ( dp ) universality class , like the contact process ( cp ) , the stationary state of the system in the inactive phase is the state devoid of particles .
other models in the same class , like the pair contact process ( pcp ) , have however a richer structure , associated with the existence of an infinite number of absorbing states @xcite . in the inactive phase ,
the absorbing state the system evolves to depends on the initial conditions and the distance from the critical point , and so does the average density of isolated particles in the stationary state . in the case of pcp ,.
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the field responsible for the dynamics ( the density of pairs of particles , @xmath8 ) is coupled to another field ( the density of isolated particles , @xmath1 ) .
this background of isolated particles is responsible for the non - universality of some dynamic properties of the system at criticality @xcite .
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9,952 |
Suppose that you have an abstract for a scientific paper: the na49 experiment at cern sps has acquired a huge data set of pb+pb events over a broad range of energy and centrality during the last several years .
this high statistics data set , coupled with a state - of - the - art analysis technique , allows for the first model - independent extraction and energy scan of 3d emission sources for pion pairs at sps energies .
these 3d pion emission sources provide new insights into the nature of a long - range source previously reported by phenix at rhic .
the new results indicate that the pion source displays significant non - gaussian tails in the longitudinal direction at 40 and 158 agev and in the outward direction at 158 agev . .
And you have already written the first three sentences of the full article: a deconfined phase of nuclear matter is expected to be formed at the high energy densities created in relativistic heavy ion collisions @xcite .
it is widely believed that important signatures of such a phase are reflected in the space - time extent and shape of particle emission source functions .
recently , 1-dimensional source imaging techniques @xcite have revealed a non - trivial long range structure in the two - pion emission source at rhic @xcite ..
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the origins of this structure are still unclear .
the presence / absence of such a structure in the pion emission sources in heavy ion collisions at intermediate sps energies could yield important information which could help resolve the structure s origins .
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9,953 |
Suppose that you have an abstract for a scientific paper: the application of high - resolution spectropolarimetry has led to major progress in understanding the magnetism and activity of late - type stars . during the last decade , magnetic fields have been discovered and mapped for many types of active cool stars using spectropolarimetric data .
however , these observations and modeling attempts are fundamentally incomplete since they are based on the interpretation of the circular polarization alone . taking advantage of the newly built harps polarimeter
, we have obtained the first systematic observations of several cool active stars in all four stokes parameters .
here we report the detection of magnetically - induced linear polarization for the primary component of the very active rs cvn binary hr1099 and for the moderately active k dwarf @xmath0 eri . for both stars
the amplitude of linear polarization signatures is measured to be @xmath110@xmath2 of the unpolarized continuum , which is approximately a factor of ten lower than for circular polarization .
this is the first detection of the linear polarization in line profiles of cool active stars .
our observations of the inactive solar - like star @xmath3 cen a show neither circular nor linear polarization above the level of @xmath110@xmath4 , indicating the absence of a net longitudinal magnetic field stronger than 0.2 g. .
And you have already written the first three sentences of the full article: polarization in spectral lines is the most direct and reliable signature of the presence of magnetic fields on the surfaces of stars .
while the zeeman broadening of unpolarized spectra can be used , with some ambiguity , to diagnose kg - strength fields in the extremely active stars @xcite , circular polarimetry enables detection of global magnetic fields on the order of one gauss and weaker in moderately active stars @xcite .
the diagnostic power of polarimetry comes from the possibility to measure very precisely magnetic signals in spectral lines against an unpolarized continuum and to boost the signal - to - noise ratio by combining weak polarization signals in thousands of spectral lines recorded simultaneously with a wide wavelength coverage chelle spectrometer @xcite ..
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furthermore , doppler imaging analysis of the rotational modulation of circular polarization in spectral lines has resulted in detailed maps of stellar magnetic fields ( e.g. , * ? ? ?
* ) , leading to many new insights into the magnetism and activity of different groups of late - type stars @xcite .
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9,954 |
Suppose that you have an abstract for a scientific paper: lattice fermions have well - known difficulties with chiral symmetry . to evade them
it is possible to couple _ continuum _ fermions to _ lattice _ gauge fields , by introducing an interpolation of the latter . following this line of thinking ,
this paper presents two euclidean formulations of the effective action that appears after functional integration over fermion fields , one for vector - like and the other for chiral couplings . with suitable finite - mode regulators both
effective actions can be evaluated in a finite computation .
the prescriptions provided here contain some details not found in previous work marrying continuum fermions to the lattice via an interpolation .
for example , the counter - terms needed to maintain chiral gauge invariance are explicitly given . by construction
coupling - constant renormalization , anomaly structure , and ( in the chiral gauge theory ) fermion nonconserving amplitudes all satisfy one s expectations from perturbative and semi - classical analyses . addtoresetequationsection # 1#1^ # 1#1 # 1 # 1#1 # 1#2 # 1#2 .
And you have already written the first three sentences of the full article: a long - standing problem in quantum field theory is a nonperturbative formulation of chiral fermions .
our only general nonperturbative formulation of quantum field theory is the renormalization - group limit of functional integrals defined on a lattice .
but when chiral symmetry is an issue , there are notorious problems @xcite ..
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briefly , one must either sacrifice locality or positivity , tolerate additional states ( doubling or mirror states ) , or break chiral symmetry explicitly . when the coupling of fermions to gauge fields is vector - like , the standard formulations @xcite are adequate , if imperfect . on the other hand ,
when fermions couple to chiral gauge fields , it has been difficult to prove a conceptually clean theory ; see ref .
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9,955 |
Suppose that you have an abstract for a scientific paper: to ensure the privacy of users in transport systems , researchers are working on new protocols providing the best security guarantees while respecting functional requirements of transport operators . in this paper[multiblock footnote
omitted ] , we design a secure nfc m - ticketing protocol for public transport that preserves users anonymity and prevents transport operators from tracing their customers trips . to this end , we introduce a new practical set - membership proof that does not require provers nor verifiers ( but in a specific scenario for verifiers ) to perform pairing computations .
it is therefore particularly suitable for our ( ticketing ) setting where provers hold sim / uicc cards that do not support such costly computations .
we also propose several optimizations of boneh - boyen type signature schemes , which are of independent interest , increasing their performance and efficiency during nfc transactions .
our m - ticketing protocol offers greater flexibility compared to previous solutions as it enables the post - payment and the off - line validation of m - tickets . by implementing a prototype using a standard nfc sim card ,
we show that it fulfils the stringent functional requirement imposed by transport operators whilst using strong security parameters . in particular , a validation can be completed in @xmath0 when the mobile is switched on , and in @xmath1 when the mobile is switched off or its battery is flat . .
And you have already written the first three sentences of the full article: _ near field communication ( nfc ) _
@xcite is a highly - practical emerging technology @xcite . indeed ,
nfc - enabled smartphones are being used in several domains , such as payment @xcite , access control @xcite and ticketing @xcite . in the following ,.
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we focus on mobile ticketing for public transport .
such a ticketing system is operated by a transport authority representing the transport service provider , and it usually consists of three phases @xcite .
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9,956 |
Suppose that you have an abstract for a scientific paper: a recent data analysis of the far - infrared ( fir ) map of the galaxy and the magellanic clouds has shown that there is a tight correlation between two fir colours : the @xmath0 and @xmath1 colours .
this fir colour relation called `` main correlation '' can be interpreted as indicative of a sequence of various interstellar radiation fields with a common fir optical property of grains . in this paper
, we constrain the fir optical properties of grains by comparing the calculated fir colours with the observational main correlation . we show that neither of the `` standard '' grain species ( i.e. astronomical silicate and graphite grains ) reproduces the main correlation .
however , if the emissivity index at @xmath2 m is changed to @xmath31.5 ( not @xmath4 as the above two species ) , the main correlation can be successfully explained .
thus , we propose that the fir emissivity index is @xmath31.5 for the dust in the galaxy and the magellanic clouds at @xmath5 .
we also consider the origin of the minor correlation called `` sub - correlation '' , which can be used to estimate the galactic star formation rate .
[ firstpage ] dust , extinction galaxies : ism galaxy : stellar content infrared : galaxies infrared : ism magellanic clouds .
And you have already written the first three sentences of the full article: dust grains absorb stellar ultraviolet ( uv)optical light and reprocess it into far - infrared ( fir ) , thereby affecting the energetics of interstellar medium ( ism ) ( e.g. * ? ? ?
the fir luminosity is known to be a good indicator of star formation rate ( sfr ) in galaxies @xcite .
this can be explained if a large part of dust grains are heated by uv light from massive stars ..
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the fir spectral energy distribution ( sed ) of dust grains reflects various information on the grains themselves and on the sources of grain heating ( e.g. * ? ? ?
* ; * ? ? ?
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9,957 |
Suppose that you have an abstract for a scientific paper: recent optical spectra of post - agb stars show the presence of c@xmath0 , cn , and ch@xmath1 originating in the circumstellar shell .
we present here new , higher resolution spectra which provide constraints on the physical parameters and information on the line profiles .
an empirical curve of growth for the c@xmath0 phillips and cn red system lines in the spectrum of hd 56126 yields @xmath2 km s@xmath3 .
ch@xmath1 ( 0,0 ) emission lines in the spectrum of the red rectangle have been resolved with a fwhm @xmath4 0.8 kms@xmath3 .
the circumstellar cn lines of iras 080052356 are resolved into two separate components with a velocity separation of @xmath5 km s@xmath3 .
the line profiles of cn of hd 235858 have not been resolved . .
And you have already written the first three sentences of the full article: post - agb stars are in a transition stage between the asymptotic giant branch ( agb ) and the planetary nebulae ( pn ) stage . during the early stage of post - agb evolution
the star is obscured by material expelled during the agb phase ( the agb ejecta ) . as this ejecta slowly moves away from the central star , the optical depth decreases and
the star can be detected in the optical ..
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when the star reaches high enough temperatures , the agb ejecta is ionized and is observable as a planetary nebula .
we have studied optically bright post - agb stars ( spectral type a to g supergiants ) which show circumstellar molecular line absorption ( c@xmath0 and cn , or ch@xmath1 ) or emission ( ch@xmath1 ) in their optical spectra .
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9,958 |
Suppose that you have an abstract for a scientific paper: the perturbation caused by planet - moon binarity on the time - of - arrival signal of a pulsar with an orbiting planet is derived for the case in which the orbits of the moon and the planet - moon barycenter are both circular and coplanar .
the signal consists of two sinusoids with frequency @xmath0 and @xmath1 , where @xmath2 and @xmath3 are the mean motions of the planet and moon around their barycenter , and the planet - moon system around the host , respectively .
the amplitude of the signal is equal to the fraction @xmath4 [ r / r]^5 $ ] of the system crossing time @xmath5 , where @xmath6 and @xmath7 are the the masses of the planet and moon , @xmath8 is their orbital separation , @xmath9 is the distance between the host pulsar and planet - moon barycenter , @xmath10 is the inclination of the orbital plane of the planet , and @xmath11 is the speed of light .
the analysis is applied to the case of psr b1620 - 26 b , a pulsar planet , to constrain the orbital separation and mass of any possible moons .
we find that a stable moon orbiting this pulsar planet could be detected , if the moon had a separation of about one fiftieth of that of the orbit of the planet around the pulsar , and a mass ratio to the planet of @xmath12 5% or larger . .
And you have already written the first three sentences of the full article: in the past decade and a half , over two hundred and fifty extra - solar planets have been discovered . with the data expected to be produced by satellites such as corot @xcite and kepler @xcite
, it will not only be possible to find smaller planets , but moons of those planets as well @xcite . as a result
, the detectability of extra - solar moons is starting to be explored in terms of their effect on planetary microlensing @xcite and transit lightcurves @xcite ..
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upper limits have already been placed on the mass and radius of putative moons of the planets hd 209458 b @xcite , ogle - tr-113 b @xcite and hd 189733 b @xcite . while the limitations of microlensing and the transit technique for detecting moons have been discussed and used in the literature , the limitations of other techniques such as the time - of - arrival ( toa ) technique have not .
this technique involves determining the variations in line - of - sight position to the host star , usually a pulsar , using the observed time of periodic events associated with that host .
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9,959 |
Suppose that you have an abstract for a scientific paper: the backscattering process of injected electrons on exchange - splitted levels of quantum well ( qw ) in ferromagnetic metal / insulator / semiconductor heterostructure is studied .
it is found that , if one of the exchange - splitted levels lies in the top region of the qw and the energy of injected electrons is close to the energy of localized electron on this level , the backward scattering becomes dependent on spins of injected electrons .
accumulation of backscattered electrons in the qw leads to considerable reduction of the current depended on its spin orientation .
the spin polarization increases with growth of the applied electric field and the storage time of electrons in the qw .
high values of the spin polarization can be achieved at room temperature . in this way , the qw with exchange - splitted levels in ferromagnetic metal / insulator / semiconductor heterostructure can be used as effective spin filter . .
And you have already written the first three sentences of the full article: the active manipulation of spin - dependent electron transport is the principal task in spintronics @xcite .
one of the effective way to achieve spin polarization of electrons injected into semiconductors is spin - dependent tunnelling through a barrier in ferromagnetic metal / insulator / semiconductor heterostructures @xcite .
the maximum of the spin injection efficiency reaches 52% at 100 k and 32% at 290 k for a mgo barrier on gaas @xcite ..
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high electrical injection of spin - polarized electrons from a fe film through an al@xmath0o@xmath1 tunnel barrier into si has been demonstrated in @xcite . however , in si the electron spin polarization was observed at low temperatures
30% at 5 k , with polarization extending to at least 125 k. although important results in the spin injection have been obtained , high values of the spin polarization of injected electrons at room temperature has not been achieved .
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9,960 |
Suppose that you have an abstract for a scientific paper: determining the properties of remote globular clusters and elliptical galaxies using evolutionary population synthesis requires a library of reliable model stellar fluxes .
empirical libraries are limited to spectra of stars in the solar neighborhood , with nearly solar abundances and abundance ratios .
we report here a first step towards providing a flux library that includes nonsolar abundances , based on calculations from first principles that are calibrated empirically .
because the mid - ultraviolet spectrum of an old stellar system is dominated by the contribution from its main - sequence turnoff stars , we have started by modeling these .
we have calculated mid - ultraviolet spectra for the sun and nine nearby , near - main - sequence stars spanning metallicities from less than 1/100 solar to greater than solar , encompassing a range of light - element abundance enhancements .
we first determined temperatures of eight of the stars by analyzing optical echelle spectra together with the mid - ultraviolet .
both could be matched at the same time only when models with no convective overshoot were adopted , and only when an approximate chromosphere was incorporated near the surface of relatively metal - rich models .
extensive modifications to mid - uv line parameters were also required , notably the manual assignment of approximate identifications for mid - uv lines missing from laboratory linelists . without recourse to additional missing opacity , these measures suffice to reproduce in detail almost the entire mid - uv spectrum of solar - temperature stars up to one - tenth solar metallicity , and the region from 2900 to 3100 throughout the entire metallicity range .
ramifications for abundance determinations in individual metal - poor stars and for age - metallicity determinations of old stellar systems are briefly discussed , with emphasis on the predictive power of the calculations . .
And you have already written the first three sentences of the full article: to characterize the metallicity and age of an old stellar system , iron abundance [ fe / h ] ( the logarithm of the iron - to - hydrogen abundance ratio with respect to its solar value ) and the stellar effective temperature must be determined together for its main - sequence turnoff ( msto ) stars .
these are dwarfs and subgiants of types f and early g with @xmath0 .
their spectra are dominated by fei lines , whose strength increases as declines . for both metallicity and age , then , a reliable derivation of is necessary ..
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this can be problematical even for an individual star .
the photometric colors often used to derive are sensitive to reddening by the interstellar medium and to the modeling of convection ( castelli , gratton , & kurucz 1997 ) , as is the more recently developed infrared flux method @xcite .
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9,961 |
Suppose that you have an abstract for a scientific paper: we report the first detection of ammonia in the homunculus nebula around @xmath0 carinae , which is also the first detection of emission from a polyatomic molecule in this or any other luminous blue variable ( lbv ) nebula .
observations of the nh@xmath1 ( j , k)=(3,3 ) inversion transition made with the australia telescope compact array reveal emission at locations where infrared h@xmath2 emission had been detected previously , near the strongest dust emission in the core of the homunculus .
we also detect ammonia emission from the so - called `` strontium filament '' in the equatorial disk .
the presence of nh@xmath1 around @xmath0 car hints that molecular shells around some wolf - rayet stars could have originated in prior lbv eruptions , rather than in cool red supergiant winds or the ambient interstellar medium . combined with the lack of any co detection , nh@xmath1 seems to suggest that the homunculus is nitrogen rich like the ionized ejecta around @xmath0 car .
it also indicates that the homunculus is a unique laboratory in which to study unusual molecule and dust chemistry , as well as their rapid formation in a nitrogen - rich environment around a hot star .
we encourage future observations of other transitions like nh@xmath1 ( 1,1 ) and ( 2,2 ) , related molecules like n@xmath2h@xmath3 , and renewed attempts to detect co. .
And you have already written the first three sentences of the full article: so far , @xmath0 carinae is the only luminous blue variable ( lbv ) known to be surrounded by dense molecular gas in its own ejecta nebula ( smith 2006 , 2002a ; smith & davidson 2001 ) .
nearly all other lbv nebulae show bright infrared [ fe ii ] emission from dense partially - ionized gas ( smith 2002b ; smith & hartigan 2006 ) and many have detectable dust shells ( e.g. , clark et al .
this owes to the extreme youth , high density , and extremely high mass ( more than 10 m@xmath4 ) of the bipolar homunculus nebula ( smith et al ..
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thus , it is a unique laboratory in which to study the behavior of molecules bathed in fuv radiation ( e.g. , ferland et al .
2005 ) .
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9,962 |
Suppose that you have an abstract for a scientific paper: we initiate the study of reducts of relational structures up to primitive positive interdefinability : after providing the tools for such a study , we apply these tools in order to obtain a classification of the reducts of the logic of equality .
it turns out that there exists a continuum of such reducts .
equivalently , expressed in the language of universal algebra , we classify those locally closed clones over a countable domain which contain all permutations of the domain . .
And you have already written the first three sentences of the full article: our results have impact on three fields : model theory , universal algebra , and theoretical computer science .
we therefore have a three - fold introduction . in model theory , reducts of a relational structure @xmath0
are usually considered _ up to first - order interdefinability_. to be more precise , one considers the reducts of the expansion of @xmath0 by all first - order definable relations , and two reducts @xmath1 and @xmath2 are considered to be the same if and only if there is a first - order definition of @xmath1 in @xmath2 and vice versa ..
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it is well - known that there is a close connection between classifications of reducts up to first - order interdefinability and the theory of infinite ( closed ) permutation groups . in 1976
, cameron @xcite showed that the highly set - transitive permutation groups are exactly the automorphism groups of the reducts of @xmath3 .
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9,963 |
Suppose that you have an abstract for a scientific paper: graph cocycles for star - products are investigated from the combinatorial point of view , using connes - kreimer renormalization techniques .
the hochschild complex , controlling the deformation theory of associative algebras , is the `` kontsevich representation '' of a dgla of graphs coming from a pre - lie algebra structure defined by graph insertions ( gerstenhaber composition with leibniz rule ) .
properties of the dual of its uea ( an odd parity analog of connes - kreimer hopf algebra ) , are investigated in order to find solutions of the deformation equation .
the solution of the initial value deformation problem , at tree - level , is unique . for linear coefficients
the resulting formulas are relevant to the hausdorff series .
xypic epsf # 1by # 1 # 1by # 1 0.5 in 6.5 in 8.5 in [ section ] [ section ] [ section ] [ section ] [ section ] [ section ] [ section ] [ section ] .
And you have already written the first three sentences of the full article: kontsevich solution for deformation quantization of poisson manifolds @xcite is based on a specific qft @xcite , yet universal : use one quantization to find them all .
the coefficients of the star - product , expressed as integrals on some configuration spaces , are the corresponding amplitudes .
in @xcite it was shown that the coefficients represent a cocycle of the cobar construction of the dg - coalgebra of kontsevich graphs , and it was conjectured that there should exist a direct combinatorial approach , as an alternative to the above analytical approach . in this article the deformation problem for associative algebras is pulled back at the level of graphs . as a generalization , generic associative deformations of associative algebras in a generic direction , not necessarily poisson , are also considered ..
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the corresponding cocycles are `` unitary characters '' , i.e. satisfying @xmath0 ( inverse relative to convolution ) .
the `` initial value ( deformation ) problem '' at tree - level ( no loops ) has a unique solution . in the case of linear coefficients , e.g. for @xmath1 , with @xmath2 a lie algebra , the solution is expected to correspond to the hausdorff series , which is the `` forefather '' of all quantizations .
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9,964 |
Suppose that you have an abstract for a scientific paper: possible detection of signatures of structure formation at the end of the dark age epoch ( @xmath0 ) is examined .
we discuss the spectral spatial fluctuations in the cmbr temperature produced by elastic resonant scattering of cmbr photons on hd molecules located in protostructures moving with peculiar velocity .
detailed chemical kinematic evolution of hd molecules in the expanding homogeneous medium is calculated .
then , the hd abundances are linked to protostructures at their maximum expansion , whose properties are estimated by using the top hat spherical approach and the @xmath1cdm cosmology .
we find that the optical depths in the hd three lowest pure rotational lines for high peak protohaloes at their maximum expansion are much higher than those in lih molecule .
the corresponding spectral spatial fluctuation amplitudes however are probably too weak as to be detected by current and forthcoming millimeter
telescope facilities .
we extend our estimates of spectral spatial fluctuations to gas clouds inside collapsed cdm haloes by using results from a crude model of hd production in these clouds .
the fluctuations for the highest
peak cdm haloes at redshifts @xmath2 could be detected in the future .
observations will be important to test model predictions of early structure formation in the universe .
cosmology : first stars galaxies : formation molecular processes cosmology : theory dark matter .
And you have already written the first three sentences of the full article: in the last years a great deal of interest arose for understanding the formation of the first structures in the universe at the end of the so called dark age epoch .
this interest is motivated not only by the possibilities of direct measurements of the physical conditions prevailing in these ( proto)structures and the constraining of cosmological parameters at very high redshifts , but also by the measurement of the primordial abundances of key elements ( e.g. , d and li ) in pregalactic epochs as a direct signature of the big bang nucleosynthesis ( bbn ) . from the observational side , the re emission or absorption of cosmic microwave background radiation ( cmbr ) photons in resonant lines from h@xmath3 , lih , and hd , among other primordial molecules ,
have been suggested as a viable way to detect cosmic protostructures ( dubrovich 1977,1983 ; maoli , melchiorri & tosti 1994 ; maoli et al.1996 ) ..
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resonant absorption by neutral h at its 21 cm transition has also been proposed to trace protostructures at early cosmic times ( hogan & rees 1979 ; for more recent studies see barkana & loeb 2005 and more references therein ) .
the first attempt to detect lih emission and doppler induced anisotropies in the cmbr from the protostructures at redshift @xmath4 was made with the 30 meter iram radio telescope ( de bernardis et al .
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9,965 |
Suppose that you have an abstract for a scientific paper: an iterative method for reconstructing mass distribution in spiral galaxies using a thin disk approximation is developed .
as an example , the method is applied to galaxy ngc 4736 ; its rotation curve does not allow one to employ a model with a massive spherical halo .
we find a global mass distribution in this galaxy ( without non - baryonic dark matter ) that agrees perfectly with the high resolution rotation curve of the galaxy .
this mass distribution is consistent with the @xmath0-band luminosity profile with the mean mass - to - light ratio @xmath1 , and also agrees with the amount of hydrogen observed in the outermost regions of the galaxy .
we predict the total mass of the galaxy to be only @xmath2 .
it is very close to the value predicted by the modified gravity models and much less than the currently accepted value of @xmath3 ( with @xmath4 of the mass in a dark matter halo ) . .
And you have already written the first three sentences of the full article: determination of dynamical masses of spiral galaxies is a decisive step in establishing empirically the clustering scale of dark matter . the cold dark matter model predicts a hierarchy of scales , from a dwarf sub - halo scale of @xmath5 of solar masses up to a galaxy cluster size .
there is a strong evidence from the @xmath6-ray observations of galaxy clusters , and from detecting dark matter with gravitational lensing @xcite for a @xmath7 scale , which is the galaxy cluster scale . at the galactic size scale ( of the order of @xmath8 ) , there are contradictory results .
dark matter was not observed in some elliptical galaxies @xcite . as for the spiral galaxies ,.
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it was pointed out that the amount of dark matter in the disk of the milky way galaxy near the sun is insignificant @xcite
. moreover , mass estimates of spiral galaxies are model - dependent @xcite . in the following
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9,966 |
Suppose that you have an abstract for a scientific paper: using molecular dynamics simulations we analyze the dynamics of two atomic liquids that display a liquid - liquid phase transition ( llpt ) : si described by the stillinger - weber potential and ga as modeled by the modified embedded - atom model ( meam ) .
in particular , our objective is to investigate the extent to which the presence of a dip in the self - intermediate scattering function is a manifestation of an excess of vibrational states at low frequencies and may be associated with a fragile - to - strong transition ( ftst ) across the llpt , as suggested recently .
our results do not lend support to these suggestions . specifically , in the case of ga we observe the appearance of an excess of vibrational states at low frequencies , even in the absence of the appearance of a dip in the self - intermediate scattering function across the llpt .
furthermore , studying the behavior of the shear viscosities traversing the llpts we find that , despite the development of a dip in the self - intermediate scattering function for the case of si and its absence in ga , both substances are fragile in character above and below their respective llpt temperatures . .
And you have already written the first three sentences of the full article: liquid polyamorphism , i.e. , the existence of distinct liquid phases of a pure substance , was proposed over 40 years ago @xcite to explain the occurrence of unusual melting properties of certain substances , such as melting - curve maxima ( as in p , cs , ba , etc ) and negative - sloped melting lines ( as in water , si , ge , ga , etc ) .
@xcite this so - called two - state model predicts the existence of a first - order phase transition between different liquid forms of the same substance , commonly referred to as the high - density liquid ( hdl ) and low - density liquid ( ldl ) , with a coexistence line that ends at a second critical point . although it is still an intensely debated issue,@xcite there are indications for the existence of such llpts in a number of substances . aside from experimental observations of llpts in elemental phosphorus @xcite , @xmath0 , @xcite the molecular liquids triphenyl phosphite @xcite and n - butane , @xcite and the compound ass .
@xcite other experimental data and computer simulations suggest the occurrence of llpts in other substances such as water , @xcite silicon , @xcite gallium @xcite and nitrogen ..
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@xcite in addition to studies considering the structural characteristics associated with the transition between the hdl and ldl forms , there has been an increasing interest in the liquid dynamics across llpts .
@xcite in the case of silicon , sastry and angell @xcite found that , across an interval of 15 k through the llpt , the intermediate scattering function develops a pronounced plateau characteristic of the so - called cage effect and the self - diffusion coefficient decreases by two orders of magnitude .
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9,967 |
Suppose that you have an abstract for a scientific paper: a theory for the heating of coronal magnetic flux ropes is developed .
the dissipated magnetic energy has two distinct contributions : ( 1 ) energy injected into the corona as a result of granule - scale , random footpoint motions , and ( 2 ) energy from the large - scale , nonpotential magnetic field of the flux rope .
the second type of dissipation can be described in term of hyperdiffusion , a type of magnetic diffusion in which the helicity of the mean magnetic field is conserved .
the associated heating rate depends on the gradient of the torsion parameter of the mean magnetic field .
a simple model of an active region containing a coronal flux rope is constructed .
we find that the temperature and density on the axis of the flux rope are lower than in the local surroundings , consistent with observations of coronal cavities .
the model requires that the magnetic field in the flux rope is stochastic in nature , with a perpendicular length scale of the magnetic fluctuations of order 1000 km . .
And you have already written the first three sentences of the full article: in this paper we consider the heating of the solar corona in regions where the large - scale magnetic field deviates significantly from a ( current - free ) potential field .
evidence for such nonpotential structures comes from a variety of sources .
measurements of photospheric vector fields in active regions often show deviations from the potential field ..
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x - ray observations show _ sigmoids _ , which are bright s - shaped or inverse s - shaped structures inside or between active regions .
these sigmoids contain coronal loops that are highly sheared with respect to the photospheric polarity inversion line ( pil ) , and are are often associated with h@xmath0 filaments .
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9,968 |
Suppose that you have an abstract for a scientific paper: + [ 10 mm ] * abstract : * in previous work , we presented a statistical scan over the soft supersymmetry breaking parameters of the minimal susy @xmath0 model .
for specificity of calculation , unification of the gauge parameters was enforced by allowing the two @xmath1 wilson lines to have mass scales separated by approximately an order of magnitude .
this introduced an additional `` left - right '' sector below the unification scale . in this paper , for three important reasons , we modify our previous analysis by demanding that the mass scales of the two wilson lines be simultaneous and equal to an `` average unification '' mass @xmath2 .
the present analysis is 1 ) more `` natural '' than the previous calculations , which were only valid in a very specific region of the calabi - yau moduli space , 2 ) the theory is conceptually simpler in that the left - right sector has been removed and 3 ) in the present analysis the lack of gauge unification is due to threshold effects particularly heavy string thresholds , which we calculate statistically in detail . as in our previous work ,
the theory is renormalization group evolved from @xmath2 to the electroweak scale being subjected , sequentially , to the requirement of radiative @xmath0 and electroweak symmetry breaking , the present experimental lower bounds on the @xmath0 vector boson and sparticle masses , as well as the lightest neutral higgs mass of @xmath3125 gev .
the subspace of soft supersymmetry breaking masses that satisfies all such constraints is presented and shown to be substantial . .
And you have already written the first three sentences of the full article: within the context of the heterotic superstring and heterotic m - theory @xcite , there have been a number of vacuum states whose four - dimensional low energy effective field theory @xcite has the exact spectrum of the mssm with or without right - handed neutrino chiral multiplets and , to prohibit rapid proton decay , contains r - parity @xcite either as a discrete symmetry or as a subgroup of an anomaly free @xmath4 extension of the standard model gauge group @xcite .
one such vacuum was presented in @xcite and will be referred to as the @xmath0 mssm .
be that as it may , this is only the first step in finding a realistic heterotic string vacuum ..
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any such theory must also also be compatible with all presently observed low - energy phenomenology ; that is , it must spontaneously break electroweak ( ew ) symmetry at the observed scale , must be compatible with the newly discovered higgs particle with mass @xmath5 gev @xcite , have all sparticle masses above the present observational lower bounds and assuming r - parity is contained in an additional @xmath4 symmetry
spontaneously break that abelian group with an associated gauge boson mass in excess of the present experimental lower bound . in a series of papers @xcite ,
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9,969 |
Suppose that you have an abstract for a scientific paper: we propose to realize microwave quantum illumination in weak coupling regime based on multimode optomechanical systems . in our proposal
the multimode together with a frequency - mismatch process could reduce mechanical thermal noise .
therefore , we achieve a significant reduction of error probability than conventional detector in weak coupling regime . moreover , we optimize the signal - to - noise ratio for limited bandwidth by tuning the delay time of entangled wave - packets .
= 0 pt .
And you have already written the first three sentences of the full article: quantum entanglement is a key ingredient in quantum information processing@xcite . in practice
, entanglement can be easily destroyed by environment noise@xcite .
quantum illumination(qi ) can benefit from entanglement in target detection even it is under these entanglement - destroying noise@xcite ..
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the aim of quantum illumination is to detect low - reflective target which is embedded in a bright background thermal bath .
half of a pair of entangled optical beams is sent out to interrogate the target region . then the returned and the retained signal beam are used to decide the presence or absence of the object . even though the fragile entanglement is easily destroyed by the bright thermal noise
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9,970 |
Suppose that you have an abstract for a scientific paper: we prove that a k3 quartic surface @xmath0 defined over a field of characteristic 3 can contain at most 112 lines .
if @xmath0 contains 112 lines , then it is projectively equivalent to the fermat quartic surface ; otherwise , @xmath0 contains at most 67 lines .
if @xmath0 contains a star , then it has 112 lines or at most 58 .
we provide explicit equations of three 1-dimensional families of smooth quartic surfaces with 58 lines . .
And you have already written the first three sentences of the full article: in the last years the enumerative geometry of straight lines on quartic surfaces in @xmath1 has been studied by many authors . unlike smooth cubic surfaces , which always contain 27 lines
, one can prove by a standard dimension count that a general quartic surface does not contain any line at all .
one is therefore led to study the maximal number of lines that a quartic surface can contain ..
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historically , the main focus has been on smooth complex quartic surfaces , which are well - known examples of algebraic k3 surfaces . in 1882
f. schur @xcite discovered a surface with 64 lines that now carries his name , given by the following equation @xmath2 the fact that 64 is indeed the highest number of lines that a smooth complex quartic surface can contain was proven by b. segre in 1943 @xcite . around 70 years later , though , s. rams and m. schtt @xcite discovered a flaw in segre s argument and fixed his proof , extending it to smooth quartic surfaces defined over a field of characteristic different from 2 and 3 . at the same time , a. degtyarev , i. itenberg and a. s. sertz @xcite spurred by a remark of w. barth @xcite were tackling the same problem using the theory of k3 surfaces and nikulin s theory of discriminant forms .
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9,971 |
Suppose that you have an abstract for a scientific paper: we report the discovery of milli - hertz ( mhz ) quasi - periodic oscillations ( qpos ) and qpo - modulated pulsations during large x - ray flares from the high - mass x - ray binary pulsar lmc x4 using data from the _ rossi x - ray timing explorer _ ( rxte ) .
the lightcurves of flares show that , in addition to @xmath074 mhz coherent pulsations , there exist two more time - varying temporal structures at frequencies of @xmath00.651.35 and @xmath0220 mhz .
these relatively long - term structures appear in the power density spectra as mhz qpos and as well - developed sidebands around the coherent pulse frequency as well , indicating that the amplitudes of the coherent pulsation is modulated by those of the mhz qpos .
one interesting feature is that , while the first flare shows symmetric sidebands around the coherent pulse frequency , the second flare shows significant excess emission in the lower - frequency sidebands due to the @xmath0220 mhz qpos .
we discuss the origin of the qpos using a combination of the beat - frequency model and a modified version of the keplerian - frequency model . according to our discussion
, it seems to be possible to attribute the origin of the @xmath00.651.35 and @xmath0220 mhz qpos to the beating between the rotational frequency of the neutron star and the keplerian frequency of large accreting clumps near the corotation radius and to the orbital motion of clumps at keplerian radii of 2@xmath110 @xmath2 10@xmath3 cm , respectively . .
And you have already written the first three sentences of the full article: since the first discovery of an x - ray pulsar in the cen x@xmath13 system , it has been generally accepted that accretion disk plays a key role in the evolution of accretion - powered x - ray binary pulsars ( axbps ) .
the instantaneous luminosity and spin rates are mainly determined by accretion rates from the surrounding disk through the release of gravitational potential energy and the transfer of angular momentum . if the precessing accretion disk is tilted with respect to the orbital plane of the binary and periodically lies in a plane containing the line - of - sight to the pulsar , the long - term super - orbital motions detected from a few axbps can also be explained . in spite of its critical importance and extensive previous studies ,
however , the detailed properties of the accretion disk around axbp are still poorly known . one useful phenomenon for studying the accretion disk around axbp is quasi - periodic oscillations ( qpos ) which have been considered to be related to the motion of the accretion disk , especially the innermost part ..
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about 10 axbps have been detected with x - ray qpos with frequency of 5220 mhz to date ( boroson et al . 2000 , and references therein ) .
according to the beat - frequency model ( bfm ) , which has been the canonical model for qpos in x - ray binaries , the observed qpo frequency ( @xmath4 ) is a beat frequency between the coherent spin frequency of the pulsar ( @xmath5 ) and the keplerian frequency ( @xmath6 ) of the innermost disk , @xmath4 = @xmath6 @xmath1 @xmath5 , at the magnetosphere boundary of the pulsar @xcite .
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9,972 |
Suppose that you have an abstract for a scientific paper: electronic properties of disordered binary alloys are studied _ via _ the calculation of the average density of states ( dos ) in two and three dimensions .
we propose a new approximate scheme that allows for the inclusion of local order effects in finite geometries and extrapolates the behavior of infinite systems following _ finite - size scaling _ ideas .
we particularly investigate the limit of the quantum site percolation regime described by a tight - binding hamiltonian .
this limit was chosen to probe the role of short range order ( sro ) properties under extreme conditions .
the method is numerically highly efficient and asymptotically exact in important limits , predicting the correct dos structure as a function of the sro parameters .
magnetic field effects can also be included in our model to study the interplay of local order and the shifted quantum interference driven by the field .
the average dos is highly sensitive to changes in the sro properties , and striking effects are observed when a magnetic field is applied near the _ segregated _ regime .
the new effects observed are twofold : there is a reduction of the band width and the formation of a gap in the middle of the band , both as a consequence of destructive interference of electronic paths and the loss of coherence for particular values of the magnetic field .
the above phenomena are periodic in the magnetic flux . for other limits that imply strong localization ,
the magnetic field produces minor changes in the structure of the average dos . .
And you have already written the first three sentences of the full article: considerable efforts have been made in the understanding of localization properties of electronic states of disordered systems since the work by anderson.@xcite being the simplest one to investigate the above phenomena , the anderson model is formulated through a tight binding hamiltonian with diagonal disorder and hopping @xmath0 to nearest neighbors .
the site energies are randomly distributed within some range @xmath1 , and @xmath2 is the relevant parameter to distinguish between the strong and weak localization regimes .
anderson showed that disorder , in three dimensional systems , drives a metal - insulator transition , with a mobility edge separating localized from extended electronic states ..
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the one parameter scaling theory , introduced by abrahams _
_ , @xcite predicts that all states are localized for dimensions smaller than or equal to two .
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9,973 |
Suppose that you have an abstract for a scientific paper: in this paper , we consider a stochastic differential equation driven by a fractional brownian motion ( fbm ) and a wiener process and having jumps . we prove that this equation has a unique solution and
show that all moments of the solution are finite .
fractional brownian motion ; wiener process ; poisson measure ; stochastic differential equation ; moments primary 60g15 ; secondary 60g22 , 60h10 , 60j65 . .
And you have already written the first three sentences of the full article: the main object of this paper is a stochastic differential equation @xmath0 , \end{gathered}\ ] ] where @xmath1 is a standard wiener process ; @xmath2 is a fractional brownian motion ( fbm ) with the hurst parameter @xmath3 ; @xmath4 is a poisson measure with finite intensity measure .
such equation can be used to model processes with jumps on financial markets , where two principal random noises influence the prices .
one noise is coming from economical background and has a long - range dependence , which is modeled by the fbm ..
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another noise is intrinsic to the stock exchange , where millions of agents act independently and behave irrationally sometimes ; this is a white noise and it is modeled by a wiener process . although equation were not studied before , many authors considered some particular examples . for a pure fractional stochastic equation without wiener component and jumps @xmath5 existence and uniqueness of a solution to such equation
was proved first in @xcite . in @xcite
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9,974 |
Suppose that you have an abstract for a scientific paper: numerical computations are performed and analytic bounds are obtained on the excited spectrum of glueballs in @xmath0 gauge theory , by transverse lattice hamiltonian methods .
we find an exponential growth of the density of states , implying a finite critical ( hagedorn ) temperature .
it is argued that the nambu - goto string model lies in a different universality class . .
And you have already written the first three sentences of the full article: the behavior of qcd at finite temperature is of great theoretical and experimental interest .
traditionally , finite temperature calculations of a field theory are performed in euclidean space with periodic boundary conditions imposed in the time direction .
however , the same information can be extracted from a minkowski space calculation by examining the density of states in the spectrum as a function of energy . in particular , an exponentially increasing density of states.
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implies a finite critical temperature @xmath1 @xcite .
there is some experimental evidence of this exponential increase in the hadron spectrum @xcite .
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9,975 |
Suppose that you have an abstract for a scientific paper: we have investigated a closed set of equations for the quark propagator , which has been obtained earlier within a new , nonperturbative approach to two - dimensional covariant gauge qcd .
it is shown that this theory implies quark confinement ( the quark propagator has no poles , indeed ) , as well as dynamical breakdown of chiral symmetry ( a chiral symmetry preserving solution is forbidden ) .
the above - mentioned set of equations can be exactly solved in the chiral limit .
we develop an analytical formalism , the so - called chiral perturbation theory at the fundamental quark level , which allows one to find solution for the quark propagator in powers of the light quark masses .
each correction satisfies the differential equation , which can be formally solved .
we develop also an analytical formalism which allows one to find solution for the quark propagator in the inverse powers of the heavy quark masses .
it coincides with the free heavy quark propagator up to terms of order @xmath0 , where @xmath1 is the heavy quark mass .
so this solution automatically possesses the heavy quark flavor symmetry up to terms of order @xmath2 . at the same time
, we have found a general solution for the heavy quark propagator , which by no means can be reduced to the free one . .
And you have already written the first three sentences of the full article: the investigation of two - dimensional ( 2d ) qcd in the context of the schwinger - dyson ( sd ) dynamical equations of motion has been initiated by the pioneering paper of t hooft @xcite .
he used the free gluon propagator in the light - cone gauge , which is free from ghost complications .
he used also the large @xmath3 ( the number of colors ) limit technique in order to make the perturbation ( pt ) expansion with respect to @xmath4 reasonable . in this case the planar diagrams are reduced to quark self - energy and ladder diagrams , which can be summed ..
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the bound - state problem within the bethe - salpeter ( bs ) formalism was finally obtained free from the infrared ( ir ) singularities .
the existence of a discrete spectrum only ( no continuum in the spectrum ) was demonstrated . since this pioneering paper 2d qcd continues to attract attention ( see , for example , review @xcite and recent papers @xcite and references therein ) . despite its simplistic vacuum structure
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9,976 |
Suppose that you have an abstract for a scientific paper: a mechanism is proposed to describe the occurrence of distance - dependent dissipation peaks in the dynamics of an atomic force microscope tip oscillating over a surface characterized by a charge density wave state .
the dissipation has its origin in the hysteretic behavior of the tip oscillations occurring at positions compatible with a localized phase slip of the charge density wave .
this model is supported through static and dynamic numerical simulations of the tip surface interaction and is in good qualitative agreement with recently performed experiments on a nbse@xmath0 sample .
the study of the microscopic mechanisms leading to energy dissipation and friction has very important theoretical and practical implications . in recent years
, experiments have started to single out the effects of microscopic probes in contact or near contact with different surfaces , and much theoretical effort has been devoted to the full understanding of such experiments @xcite . in particular ,
the minimally invasive non - contact experiments offer a chance to investigate delicate surface properties and promise to bring new insight on localized effects and their interaction with the bulk .
recently , a non - contact atomic force microscopy ( afm ) experiment @xcite on a nbse@xmath0 sample has shown dissipation peaks appearing at specific heights from the surface and extending up to @xmath1 nm far from it .
these peaks were obtained with tips oscillating both parallel and perpendicular to the surface , and in a range of temperatures compatible with the surface charge density wave ( cdw ) phase of the sample . in this paper ,
a model is proposed explaining in detail the mechanism responsible for these peaks : the tip oscillations induce a charge perturbation in the surface right under the tip , but , due to the nature of the cdw order parameter , multiple stable charge configurations exist characterized by different `` topological '' properties .
when the tip oscillates at distances corresponding....
And you have already written the first three sentences of the full article: in this article , the term cdw is used to indicate a periodic modulation of the charge density @xmath2 , irrespective of the process behind its generation .
this modulation is described , in the unperturbed system and for the simplest form of cdw , as @xmath3 , where @xmath4 is the intensity and @xmath5 the characteristic wavelength .
perturbations to cdws have been studied extensively @xcite , but most studies are concerned either with uniform perturbations ( e.g. an external electric field ) or point - like perturbations ( e.g. pinning by defects ) , and often consider one - dimensional models , appropriate for quasi - one - dimensional materials , where the coherence length in the perpendicular directions is smaller than the atomic distance ..
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what is considered here , instead , is the effect of a localized but extended perturbation of typical length scale similar to the cdw wavelength , acting on a material where the coherence length is macroscopic in more than one dimension . starting from the standard fukuyama - lee - rice model @xcite for cdw
, the charge modulation is described through a ginzburg - landau theory as a classical elastic medium .
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9,977 |
Suppose that you have an abstract for a scientific paper: an important way to make large training sets is to gather noisy labels from crowds of non experts .
we propose a method to aggregate noisy labels collected from a crowd of workers or annotators .
eliciting labels is important in tasks such as judging web search quality and rating products .
our method assumes that labels are generated by a probability distribution over items and labels .
we formulate the method by drawing parallels between gaussian mixture models ( gmms ) and restricted boltzmann machines ( rbms ) and show that the problem of vote aggregation can be viewed as one of clustering .
we use @xmath0-rbms to perform clustering .
we finally show some empirical evaluations over real datasets . .
And you have already written the first three sentences of the full article: there has been considerable amount of work on learning when labeling is expensive , such as techniques on transductive inference and active learning . with the emergence of crowdsourcing services , like amazon mechanical turk , labeling costs in many applications
have dropped dramatically .
large amounts of labeled data can now be gathered at low price . due to a lack of domain expertise and misaligned incentives ,.
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however , labels provided by crowdsourcing workers are often noisy . to overcome the quality issue ,
each item is usually simultaneously labeled by several workers , and then we aggregate the multiple labels with some manner , for instance , majority voting .
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9,978 |
Suppose that you have an abstract for a scientific paper: we analyze the effects of the background velocity and the initial magnetic field correlations , and viscosities on the turbulent dynamo and the @xmath0-effect . we calculate the @xmath0-coefficients for arbitrary magnetic and fluid viscosities , background velocity and the initial magnetic field correlations .
we explicitly demonstrate that the general features of the initial growth and late - time saturation of the magnetic fields due to the non - linear feedback are qualitatively independent of these correlations .
we also examine the hydrodynamic limit of the magnetic field growth in a renormalization group framework and discuss the possibilities of suppression of the dynamo growth below a critical rotation .
we demonstrate that for kolmogorov- ( k41 ) type of spectra the _ ekman number _
@xmath1 for dynamo growth to occur . .
And you have already written the first three sentences of the full article: magnetic fields are ubiquitous .
all astrophysical objects are known to have magnetic fields of different magnitudes , e.g . , 1 gauss at the stellar scale to @xmath2 gauss at the galactic scale @xcite .
the origin of such fields ( _ primordial field _ ) is not very clear - there are several competing theories which attempt to describe this @xcite ..
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however , a finite magnetic field in any physical system undergoes a temporal decay due to the finite conductivity of the medium .
so , for steady magnetic fields to occur in astrophysical bodies , there has to be a mechanism of regeneration of the magnetic fields , which takes place due to the dynamo process @xcite .
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9,979 |
Suppose that you have an abstract for a scientific paper: viscosity and magnetic fields drive differentially rotating stars toward uniform rotation , and this process has important consequences in many astrophysical contexts .
for example , merging binary neutron stars can form a `` hypermassive '' remnant , i.e. a differentially rotating star with a mass greater than would be possible for a uniformly rotating star .
the removal of the centrifugal support provided by differential rotation can lead to delayed collapse of the remnant to a black hole , accompanied by a delayed burst of gravitational radiation .
both magnetic fields and viscosity alter the structure of differentially rotating stars on secular timescales , and tracking this evolution presents a strenuous challenge to numerical hydrodynamic codes . here , we present the first evolutions of rapidly rotating stars with shear viscosity in full general relativity . we self - consistently include viscosity in our relativistic hydrodynamic code by solving the fully relativistic navier - stokes equations .
we perform these calculations both in axisymmetry and in full 3 + 1 dimensions . in axisymmetry ,
the resulting reduction in computational costs allows us to follow secular evolution with high resolution over dozens of rotation periods ( thousands of @xmath0 ) .
we find that viscosity operating in a hypermassive star generically leads to the formation of a compact , uniformly rotating core surrounded by a low - density disk .
these uniformly rotating cores are often unstable to gravitational collapse .
we follow the collapse in such cases and determine the mass and the spin of the final black hole and ambient disk .
however , viscous braking of differential rotation in hypermassive neutron stars does not always lead to catastrophic collapse , especially when viscous heating is substantial .
the stabilizing influences of viscous heating , which generates enhanced thermal pressure , and centrifugal support prevent collapse in some cases , at least until the star cools . in all cases studied....
And you have already written the first three sentences of the full article: the field of numerical relativity has matured to a stage where it is possible to simulate realistic systems of astrophysical interest . in this paper , we examine the global effects of viscosity on differentially rotating , relativistic stars . viscosity can have significant effects on the stability of neutron stars .
for example , it can drive a secular bar instability in rapidly rotating neutron stars , as shown in newtonian gravitation @xcite and in general relativity @xcite .
viscosity can suppress the @xmath1-modes @xcite and other gravitational - radiation driven instabilities , including the secular bar modes @xcite ..
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viscosity also destroys differential rotation , and this can cause significant changes in the structure and evolution of differentially rotating massive neutron stars . differentially rotating neutron stars can support significantly more rest mass than their nonrotating or uniformly rotating counterparts , making `` hypermassive '' neutron stars possible @xcite .
such hypermassive neutron stars can form from the coalescence of neutron star binaries @xcite or from rotating core collapse .
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9,980 |
Suppose that you have an abstract for a scientific paper: the shapley supercluster survey is a multi - wavelength survey covering an area of @xmath023 deg@xmath1 ( @xmath0 260 mpc@xmath1 at z=0.048 ) around the supercluster core , including nine abell and two poor clusters , having redshifts in the range 0.045 - 0.050 .
the survey aims to investigate the role of the cluster - scale mass assembly on the evolution of galaxies , mapping the effects of the environment from the cores of the clusters to their outskirts and along the filaments .
the optical ( @xmath2 ) imaging acquired with omegacam on the vlt survey telescope is essential to achieve the project goals providing accurate multi - band photometry for the galaxy population down to m*+6 .
we describe the methodology adopted to construct the optical catalogues and to separate extended and point - like sources .
the catalogues reach average 5@xmath3 limiting magnitudes within a 3@xmath4 diameter aperture of @xmath2=[24.4,24.6,24.1,23.3 ] and are 93% complete down to @xmath2=[23.8,23.8,23.5,22.0]mag , corresponding to @xmath0 m*@xmath5 + 8.5 .
the data are highly uniform in terms of observing conditions and all acquired with seeing less than 1.1arcsec full width at half - maximum .
the median seeing in @xmath6-band is 0.6arcsec , corresponding to 0.56kpch@xmath7 at z=0.048 .
while the observations in the @xmath8 , @xmath9 and @xmath6 bands are still ongoing , the @xmath10-band observations have been completed , and we present the @xmath10-band catalogue over the whole survey area .
the latter is released and it will be regularly updated , through the use of the virtual observatory tools .
this includes 734,319 sources down to @xmath10=22.0mag and it is the first optical homogeneous catalogue at such a depth , covering the central region of the shapley supercluster .
[ firstpage ] methods : data analysis - methods : observational - catalogues - virtual observatory tools - galaxies : clusters : general - galaxies : clusters : individual : a3552 - galaxies : clusters : individual : a3554 -....
And you have already written the first three sentences of the full article: the main aim of the shapley supercluster survey ( shass ) is to quantify the influence of hierarchical mass assembly on galaxy evolution and to follow such evolution from filaments to cluster cores , identifying the primary location and mechanisms for the transformation of spirals into s0s and des .
the most massive structures in the local universe are superclusters , which are still collapsing with galaxy clusters and groups frequently interacting and merging , and where a significant number of galaxies are encountering dense environments for the first time .
the shapley supercluster ( hereafter ssc ) was chosen because of i ) the peculiar cluster , galaxy and baryon overdensities @xcite ; ii ) the relative dynamical immaturity of this supercluster and the possible presence of infalling dark matter haloes as well as evidence of cluster - cluster mergers ( e.g. * ? ? ?.
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* ; * ? ? ?
* ; * ? ? ?
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9,981 |
Suppose that you have an abstract for a scientific paper: the nature of chiral phase transition for two flavor qcd is an interesting but unresolved problem .
one of the most intriguing issues is whether or not the anomalous u(1 ) symmetry in the flavor sector is effectively restored along with the chiral symmetry .
this may determine the universality class of the chiral phase transition . since the physics near the chiral phase transition is essentially non - perturbative ,
we employ first principles lattice techniques to address this issue .
we use overlap fermions , which have exact chiral symmetry on the lattice , to probe the anomalous u(1 ) symmetry violation of 2 + 1 flavor dynamical qcd configurations with domain wall fermions .
the latter also optimally preserves chiral and flavor symmetries on the lattice , since it is known that the remnant chiral symmetry of the light quarks influences the scaling of the chiral condensate in the crossover transition region .
we observe that the anomalous u(1 ) is not effectively restored in the chiral crossover region .
we perform a systematic study of the finite size and cut - off effects since the signals of u(1 ) violation are sensitive to it .
we also provide a glimpse of the microscopic topological structures of the qcd medium that are responsible for the strongly interacting nature of the quark gluon plasma phase .
we study the effect of these microscopic constituents through our first calculations for the topological susceptibility of qcd at finite temperature , which could be a crucial input for the equation of state for anomalous hydrodynamics .
chiral fermions ; axial anomaly ; gauge field topology ; topological susceptibility ; instantons .
And you have already written the first three sentences of the full article: understanding the vacuum structure of qcd is one of the most interesting and intriguing field of research for about thirty years now .
new signals of non - trivial topological fluctuations in qcd have been proposed in recent times , like chiral magnetic effect @xcite and anomaly induced transport @xcite .
it is an ongoing topic of research in trying to understand appropriate experimental signatures of chiral magnetic effect in heavy ion collision experiments at rhic at bnl and at cern ..
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recent studies of hydrodynamic evolution in presence of chiral anomaly has also provided hints towards charge separation of different pion species @xcite .
however this is not a unique signature of non - trivial topological fluctuations in qcd .
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9,982 |
Suppose that you have an abstract for a scientific paper: three dimensional nonlinear wave interactions have been analytically described .
the procedure under interest can be applied to three dimensional quasilinear systems of first order , whose hydrodynamic reductions are homogeneous semi - hamiltonian hydrodynamic type systems ( i.e. possess diagonal form and infinitely many conservation laws ) .
the interaction of n waves was studied . in particular
we prove that they behave like simple waves and they distort after the collision region .
the amount of the distortion can be analytically computed .
october 2016 _ keywords : _ nonlinear wave interactions , hydrodynamic integrable systems , generalized hodograph method .
And you have already written the first three sentences of the full article: wave interaction problems are of great interest from a theoretical point of view as well as for possible applications in applied sciences . in this framework ,
a prominent role has been played by model evolution equations whose canonical structure allows for exact solutions describing relevant wave profiles as it happens for @xmath0 hyperbolic systems involving two dependent and two independent variables .
as well known , these mathematical models can be recast into a form expressing the evolution of a privileged set of field variables ( riemann invariants ) along the related characteristic curves . moreover , in the homogeneous case , the quasilinear system can be reduced to linear form through the classical hodograph transformation which , in principle , can be solved by using the riemann method @xcite . therefore @xmath1 homogeneous models represent a prototype for determining classes of systems whose canonical structure allows for exact solutions that facilitate a full understanding of the interaction process of hyperbolic waves . furthermore , for such a kind of models , the wave dynamics is only ruled by the behaviour of the solutions along the associated families of characteristic curves and , by making use of the special class of simple wave solutions @xcite , it is possible to understand in detail the role played by different families of characteristic curves inside the interaction region ..
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within such a theoretical framework , the riemann method was extended to the nonhomogeneous case in @xcite and a large new classes of solutions to quasilinear systems of pdes have been obtained in @xcite . furthermore a combined use of the hodograph method and of the differential constraints technique was considered in @xcite and quite recently was used in order to study nonlinear wave interactions @xcite as well as discontinuous initial value problems @xcite for homogeneous and nonhomogeneous @xmath1 systems . in a different way from @xmath1 models of first order pdes , for strictly hyperbolic systems involving @xmath2 dependent variables and two independent variables , the riemann invariants in general
do not exist so that a detailed description of wave interactions in terms of exact and closed form solutions to initial value problems is a hard task . in such a context
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9,983 |
Suppose that you have an abstract for a scientific paper: the rate of quasi - stationary , two - dimensional magnetic reconnection is calculated in the framework of incompressible hall magnetohydrodynamics ( mhd ) , which includes the hall and electron pressure terms in the ohm s law .
the hall - mhd equations are solved in a local region across the reconnection electron layer , including only the upstream region and the layer center . in the case
when the ion inertial length @xmath0 is larger than the sweet - parker reconnection layer thickness , the dimensionless reconnection rate is found to be independent of the electrical resistivity and equal to @xmath1 , where @xmath2 is the scale length of the external magnetic field in the upstream region outside the electron layer , and the ion layer thickness is found to be @xmath0 . .
And you have already written the first three sentences of the full article: magnetic reconnection is a fundamental process of breaking and topological rearrangement of magnetic field lines in magnetized plasmas .
reconnection converts magnetic energy into kinetic and thermal energy and is believed to be responsible for many phenomena observed in the laboratory and cosmic plasmas @xcite . because electrical resistivity is very low in hot plasmas , magnetic reconnection due to resistive dissipation of magnetic field is typically a very slow process @xcite .
reconnection can become much faster in the case when resistivity is anomalously high due to local plasma instabilities @xcite ..
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another possibility is fast reconnection made possible because of two - fluid plasma effects @xcite , which require a two - fluid magnetohydrodynamics ( mhd ) description of plasma . in the limit of zero electron - to - ion mass ratio ,
two - fluid mhd equations simplify and reduce to hall - mhd equations .
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9,984 |
Suppose that you have an abstract for a scientific paper: meetings such as adass demonstrate that there is an enthusiasm for communication within the astronomical software community .
however ,
the amount of information and experience that can flow around in the course of one , relatively short , meeting is really quite limited .
ideally , these meetings should be just a part of a much greater , continuous exchange of knowledge . in practice , with some notable
but often short - lived exceptions , we generally fall short of that ideal . keeping track of what is being used , where , and how successfully , can be a challenge .
a variety of new technologies such as those roughly classed as web 2.0 are now available , and getting information to flow ought to be getting simpler , but somehow it seems harder to find the time to keep that information current .
this paper looks at some of the ways we communicate , used to communicate , have failed to communicate , no longer communicate , and perhaps could communicate better .
it is presented in the hope of stimulating additional discussion and possibly even a little action aimed at improving the current situation . .
And you have already written the first three sentences of the full article: what follows is essentially a verbatim transcript of the introductory talk as given at adass , in quebec , on the morning of the first session which happened to be the day before the 2008 u.s
. presidential elections .
good morning everybody ..
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bonjour , tout le monde . everyone awake ?
no jet lag ?
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9,985 |
Suppose that you have an abstract for a scientific paper: we present theoretical ubvi- and bolometric light curves of sne ia for several explosion models , computed with our multi - group radiation hydro code .
we employ our new corrected treatment for line opacity in the expanding medium .
the results are compared with observed light curves .
our goal is to find the most viable thermonuclear sn model that gives good fits not only to a typical sn ia light curve , but also to x - ray observations of young snia remnants .
it appears that classical 1d snia models , such as deflagration w7 and delayed detonation dd4 , fit the light curves not so good as a new 3d deflagration model by reinecke et al ( which is averaged over angles for our lc modelling ) .
this model seems good also in reproducing x - ray observations of tycho snr .
we believe that the main feature of this model which allows us to get correct radiation during the first month , as well as after a few hundred years , when an snr forms , is strong mixing that pushes material enriched in iron and nickel to the outermost layers of sn ejecta . .
And you have already written the first three sentences of the full article: at the moment , there are many models of thermonuclear explosion of a star , that lead to the event we know as a type ia supernova ( sn ia ) .
some of them were discussed in the talk by j.niemeyer @xcite .
only a few parameters , such as kinetic energy and total @xmath0ni production , can be derived directly from the explosion modelling and compared with the observational values ..
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the subsequent evolution of the exploded star gives us much more possibilities to compare models and to decide which one fits observations better by reproducing more details in sn ia light curves and spectra .
we will focus here on the broad - band ubvi and bolometric light curve computations for sn ia models .
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9,986 |
Suppose that you have an abstract for a scientific paper: on the basis of the cranked skyrme - hartree - fock calculations in the three - dimensional coordinate - mesh representation , we suggest that , in addition to the well - known candidate @xmath0s , the neutron - rich nucleus @xmath1s and the drip - line nuclei , @xmath2s and @xmath3s , are also good candidates for finding superdeformed rotational bands in sulfur isotopes .
calculated density distributions for the superdeformed states in @xmath2s and @xmath3s exhibit superdeformed neutron skins .
pacs : 21.60-n ; 21.60.jz ; 27.30.+t + keywords : cranked skyrme - hartree - fock method ; superdeformation ; neutron - rich nuclei ; high - spin state ; sulfur isotopes .
And you have already written the first three sentences of the full article: recently , superdeformed ( sd ) rotational bands have been discovered in @xmath1ar , @xmath4ca and @xmath5ti @xcite .
one of the interesting new features of them is that they are built on excited @xmath6 states and observed up to high spin , in contrast to the sd bands in heavier mass regions where low - spin portions of them are unknown in almost all cases @xcite .
these excited @xmath6 states may be associated with multiparticle - multihole excitations from the spherical closed shells , so that we can hope to learn from such data detailed relationships between spherical shell model and sd configurations . for the mass @xmath730 - 50 region , although existence of a sd band in @xmath0s with the sd magic number @xmath8 has been expected for a long time @xcite , it has not yet been observed and remains as a great challenge @xcite . in this paper , as a continuation of the systematic theoretical search @xcite for sd bands in the mass @xmath730 - 50 region by means of the cranked skyrme - hartree - fock ( shf ) method@xcite , we would like to suggest that , in addition to @xmath0s , the neutron - rich nucleus @xmath1s and the nuclei , @xmath2s and @xmath3s , which are situated close to the neutron - drip line@xcite , are also good candidates for finding sd rotational bands in sulfur isotopes ..
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the appearance of the sd band in @xmath1s is suggested in connection with the sd shell structure at @xmath9 characterizing the observed sd band in @xmath4ca .
the drip - line nuclei , @xmath2s and @xmath3s , are expected to constitute a new `` sd doubly closed '' region associated with the sd magic numbers , @xmath10 for protons and @xmath11 for neutrons .
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9,987 |
Suppose that you have an abstract for a scientific paper: the spin
network quantum simulator model , which essentially encodes the ( quantum deformed ) @xmath0 racah wigner tensor algebra , is particularly suitable to address problems arising in low dimensional topology and group theory . in this combinatorial framework
we implement families of finite states and discrete time quantum automata capable of accepting the language generated by the braid group , and whose transition amplitudes are colored jones polynomials .
the automaton calculation of the polynomial of ( the plat closure of ) a link @xmath1 on @xmath2 strands at any fixed root of unity is shown to be bounded from above by a linear function of the number of crossings of the link , on the one hand , and polynomially bounded in terms of the braid index @xmath2 , on the other .
the growth rate of the time complexity function in terms of the integer @xmath3 appearing in the root of unity @xmath4 can be estimated to be ( polynomially ) bounded by resorting to the field theoretical background given by the chern simons theory .
* quantum automata , braid group and link polynomials * + dipartimento di fisica , politecnico di torino , + corso duca degli abruzzi 24 , 10129 torino ( italy ) + e - mail : [email protected] + + dipartimento di fisica nucleare e teorica , universit degli studi di pavia and istituto nazionale di fisica nucleare , sezione di pavia , + via a. bassi 6 , 27100 pavia ( italy ) + e - mail : [email protected] + + dipartimento di fisica , politecnico di torino , + corso duca degli abruzzi 24 , 10129 torino ( italy ) + e - mail : [email protected] + link invariants ; braid group representations ; chern simons theory ; quantum automata ; racah wigner algebra ; spin network simulator ; topological quantum computation ; @xmath5 representation theory . .
And you have already written the first three sentences of the full article: the spin network quantum simulator model @xcite represents a bridge between circuit schemes for standard quantum computation and approaches based on notions from topological quantum field theories ( tqft ) @xcite . the spin network computational space , naturally modelled as a graph for any fixed number of incoming spins , supports computing processes represented by families of paths and provides , on the one hand , a consistent discretized version of the topological quantum computation approach . on the other hand , such a quantum combinatorial scheme , which essentially encodes the ( quantum deformed ) @xmath0 racah
wigner tensor algebra , turns out to be particularly suitable to address problems arising in ( low dimensional ) topology and group theory .
the guiding idea of this paper is that the exponential efficiency that quantum algorithms may achieve with respect to classical ones proves to be especially relevant in problems in which the space of solutions is characterized by a structure definable in terms of the grammar and the syntax of a language , rather than algebraic or number theoretic in nature ..
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the spin network setting provides a ` natural encoding ' for classes of problems which basically share the combinatorial structure of the language underlying the ( re)coupling theory of @xmath0 angular momenta @xcite . on the other hand , the jones polynomial @xcite is no doubt the most famous knot invariant in topology , a knot invariant being a function on knots ( or links , namely circles embedded in @xmath6space ) which is invariant under isotopy ( smooth deformations ) of the knot . among its many connections to various mathematical and physical areas ( see _ e.g. _
@xcite for applications in statistical mechanics ) , we are mainly interested here in its relations with tqft @xcite . in the seminal paper @xcite , witten put link invariants in a field theoretical setting , showing that jones polynomials arise as vacuum expectation values of wilson loop operators in a three dimensional @xmath0 chern simons ( topological ) quantum field theory where the fundamental representation of the gauge group @xmath0 lives on each component of the link .
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9,988 |
Suppose that you have an abstract for a scientific paper: we investigate a simple dynamical model of a microtubule that evolves by attachment of guanosine triphosphate ( gtp ) tubulin to its end , irreversible conversion of gtp to guanosine diphosphate ( gdp ) tubulin by hydrolysis , and detachment of gdp at the end of a microtubule . as a function of rates of these processes , the microtubule can grow steadily or
its length can fluctuate wildly . in the regime where detachment can be neglected ,
we find exact expressions for the tubule and gtp cap length distributions , as well as power - law length distributions of gtp and gdp islands . in the opposite limit of instantaneous detachment , we find the time between catastrophes , where the microtubule shrinks to zero length , and determine the size distribution of avalanches ( sequence of consecutive gdp detachment events ) .
we obtain the phase diagram for general rates and verify our predictions by numerical simulations . .
And you have already written the first three sentences of the full article: microtubules are polar linear polymers that perform major organizational tasks in living cells @xcite . through a unique feature of microtubule assembly ,
termed dynamic instability @xcite , they function as molecular machines @xcite that move cellular structures during processes such as cell reproduction @xcite .
a surprising feature of microtubules is that they remain out of equilibrium under fixed external conditions and can undergo alternating periods of rapid growth and even more rapid shrinking ( fig ..
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[ l - vs - t ] ) .
these sudden polymerization changes are driven by the interplay between several fundamental processes .
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9,989 |
Suppose that you have an abstract for a scientific paper: we formulate lattice theories in which chiral symmetry is realized nonlinearly on the fermion fields . in this framework
the fermion mass term does not break chiral symmetry .
this property allows us to use the wilson term to remove the doubler fermions while maintaining exact chiral symmetry on the lattice .
our lattice formulation enables us to address non - perturbative questions in effective field theories of baryons interacting with pions and in models involving constituent quarks interacting with pions and gluons .
we show that a system containing a non - zero density of static baryons interacting with pions can be studied on the lattice without encountering complex action problems . in our formulation
one can also decide non - perturbatively if the chiral quark model of georgi and manohar provides an appropriate low - energy description of qcd .
if so , one could understand why the non - relativistic quark model works .
addtoresetequationsection _ keywords _ : chiral quark model , chiral symmetry , lattice qcd , low - energy effective theories , non - zero baryon chemical potential _ pacs numbers _ : 11.30.rd , 12.38.gc , 12.38.mh , 12.39.fe .
And you have already written the first three sentences of the full article: realizing chiral symmetry on the lattice is a problem with a long history . in 1975
wilson decided to break chiral symmetry explicitly in order to remove the unwanted doubler fermions @xcite . as a result ,
recovering chiral symmetry with wilson fermions requires fine - tuning as well as taking the continuum limit . in 1981.
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it was proved by nielsen and ninomiya @xcite and in a different way by friedan @xcite that removing the doubler fermions while maintaining locality is possible only if one explicitly breaks the chiral symmetry of the continuum theory . in 1992 , using a wilson term in 4 + 1 dimensions , kaplan constructed domain wall fermions in order to realize chiral symmetry on the lattice @xcite . at the end of the same year
, narayanan and neuberger introduced the related overlap formulation of chiral lattice fermions @xcite . already in 1982
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9,990 |
Suppose that you have an abstract for a scientific paper: this paper presents a theoretical analysis on bulk and edge states in honeycomb lattice photonic crystals with and without time - reversal and/or space - inversion symmetries .
multiple dirac cones are found in the photonic band structure and the mass gaps are controllable via symmetry breaking .
the zigzag and armchair edges of the photonic crystals can support novel edge states that reflect the symmetries of the photonic crystals .
the dispersion relation and the field configuration of the edge states are analyzed in detail in comparison to electronic edge states .
leakage of the edge states to free space is inherent in photonic systems and is fully taken into account in the analysis .
a topological relation between bulk and edge , which is analogous to that found in quantum hall systems , is also verified . .
And you have already written the first three sentences of the full article: a mono - layer of graphite sheet , called graphene , has attracted growing interests recently.@xcite graphene exhibits a dirac cone with a linear dispersion at the corner of the first brillouin zone , resulting in a variety of novel transport phenomena of electrons .
they stimulate theoretical and experimental studies taking account of analogy to physics of relativistic electron , such as klein tunneling@xcite and zitterbewegung@xcite .
moreover , semi - infinite graphene and finite stripe of graphene with zigzag edges support a novel edge state with nearly flat dispersion.@xcite on the contrary , armchair edge does not support such an edge state ..
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the flat dispersion implies that the density of state ( dos ) diverges at the flat band energy , in a striking contrast to the zero dos in bulk .
so far , theoretical investigation of graphene heavily relies on the tight - binding model .
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9,991 |
Suppose that you have an abstract for a scientific paper: we present new co ( 1 @xmath0 0 ) observations of eleven extragalactic tails and bridges in nine interacting galaxy systems , almost doubling the number of such features with sensitive co measurements .
eight of these eleven features were undetected in co to very low co / hi limits , with the most extreme case being the ngc 7714/5 bridge .
this bridge contains luminous h ii regions and has a very high hi column density ( 1.6 @xmath1 10@xmath2 @xmath3 in the 55@xmath4 co beam ) , yet was undetected in co to rms t@xmath5@xmath6 = 2.4 mk .
the hi column density is higher than standard h@xmath7 and co self - shielding limits for solar - metallicity gas , suggesting that the gas in this bridge is metal - poor and has an enhanced n@xmath8/i@xmath9 ratio compared to the galactic value .
only one of the eleven features in our sample was unambiguously detected in co , a luminous hi - rich star formation region near an optical tail in the compact group stephan s quintet .
we detect co at two widely separated velocities in this feature , at @xmath106000 km s@xmath11 and @xmath106700 km s@xmath11 .
both of these components have hi and h@xmath12 counterparts .
these velocities correspond to those of galaxies in the group , suggesting that this gas is material that has been removed from two galaxies in the group .
the co / hi / h@xmath12 ratios for both components are similar to global values for spiral galaxies . .
And you have already written the first three sentences of the full article: large amounts of interstellar gas can be removed from the main disks of spiral galaxies by four main processes : tides due to the gravitational force of a companion , ram pressure stripping during a near - head - on collision between gas - rich galaxies , ram pressure stripping by intracluster gas , and galactic winds driven by supernovae . by ejecting processed gas into intergalactic space
, these mechanisms contribute to the metal - enrichment of the intergalactic medium . in many cases , which of these four processes is active in a given galaxy system
can be determined from the optical , radio , and/or x - ray morphology ..
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the signature of a tidal encounter between two galaxies is the presence of long stellar and/or hi tails and bridges ( e.g. , toomre @xmath13 toomre 1972 ) , while head - on collisions between gas - rich galaxies can produce ring galaxies ( e.g. , lynds @xmath13 toomre 1976 ; theys @xmath13 spiegel 1977 ) as well as gaseous bridges between the galaxies ( struck 1997 ) .
ram pressure stripping by intracluster gas leads to an hi deficiency ( e.g. , giovanelli @xmath13 haynes 1983 ) , truncation of the outer hi disk of a galaxy ( cayette et al .
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9,992 |
Suppose that you have an abstract for a scientific paper: we study theoretically the impact of zener tunneling on the charge - transport properties of quasi - metallic ( qm ) carbon nanotubes ( characterized by forbidden band gaps of few tens of mev ) .
we also analyze the interplay between zener tunneling and elastic scattering on defects . to this purpose
we use a model based on the master equation for the density matrix , that takes into account the inter - band zener transitions induced by the electric field ( a quantum mechanical effect ) , the electron - defect scattering and the electron - phonon scattering . in presence of zener tunnelling the qm tubes support an electrical current even when the fermi energy lies in the forbidden band gap . in absence of elastic scattering ( in high quality samples ) , the small size of the band gap of qm tubes enables zener tunnelling for realistic values of the the electric field ( above @xmath0 1 v/@xmath1 m ) .
the presence of a strong elastic scattering ( in low quality samples ) further decreases the values of the field required to observe zener tunnelling .
indeed , for elastic - scattering lengths of the order of 50 nm , zener tunnelling affects the current / voltage characteristic already in the linear regime . in other words , in quasi - metallic tubes ,
zener tunneling is made more visible by defects . .
And you have already written the first three sentences of the full article: single - wall carbon nanotubes ( swnts ) are quasi one - dimensional wires of great interest for future electronic - devices applications
. a swnt can be constructed by rolling up a graphene sheet and its geometry is univocally specified by a pair of chiral indexes @xmath2 @xcite .
the relationship between @xmath3 and @xmath4 defines three groups of swnts : armchair @xmath5 , zigzag ( @xmath6 or @xmath7 ) and chiral nanotubes ..
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the indexes @xmath2 also determine the swnt electronic structure .
if @xmath8 is not a multiple of 3 , swnts of diameters in the 1 - 2 nm range are semiconductors with a band gap @xmath9 larger than 0.5 ev .
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9,993 |
Suppose that you have an abstract for a scientific paper: signatures of warm absorbers are seen in soft x - ray spectra of about half of all seyfert1 galaxies observed and in some quasars and blazars .
we use the thermal equilibrium curve to study the influence of the shape of the ionizing continuum , density and the chemical composition of the absorbing gas on the existence and nature of the warm absorbers .
we describe circumstances in which a stable warm absorber can exist as a multiphase medium or one with continuous variation in pressure .
in particular we find the following results : i ) the warm absorber exists only if the spectral index of the x - ray power - law ionizing continuum @xmath0 and has a multiphase nature if @xmath1 , which interestingly is the spectral index for most of the observed seyfert 1 galaxies ; ii ) thermal and ionization states of highly dense warm absorbers are sensitive to their density if the ionizing continuum is sufficiently soft , i.e. dominated by the ultraviolet iii ) absorbing gas with super - solar metallicity is more likely to have a multiphase nature ; iv ) the nature of the warm absorber is significantly influenced by the absence of iron and associated elements which are produced in the later stages of star formation history in supernovae of type ia .
# 1[eq:#1 ] # 1[fig:#1 ] # 1[sec:#1 ] # 1[subsecn:#1 ] # 1[tab:#1 ] # 1equation [ eq:#1 ] # 1figure [ fig:#1 ] # 1section [ sec:#1 ] # 1section [ subsecn:#1 ] # 1table [ tab:#1 ] # 1#1 # 110^#1 -1 cm quasars : absorption lines - galaxies : active - seyfert - ism : abundances x - rays : ism .
And you have already written the first three sentences of the full article: absorption due to highly ionized oxygen and elements of similar atomic number ( e.g. o vii , viii , ne x ) is commonly found in the soft x - ray spectra of active galactic nuclei ( agns ) ( halpern 1984 ; nandra & pounds , 1994 ; reynolds , 1997 ; george @xmath2 1998 ) . high resolution x - ray spectra from _ chandra _ and _ xmm - newton _ show that these absorption lines are always blue - shifted compared with the emission lines and so must be in outflow from the central continuum source ( collinge @xmath2 2001 , kaastra @xmath2 2002 , kinkhabwala @xmath2 2002 , blustin @xmath2 2003 , krongold @xmath2 2003 , netzer @xmath2 2003 , turner @xmath2 2004 ) .
the absorption edges and lines respond to variation of the ionizing continuum emitted by the central engine . for example , krongold et al .
( 2007 ) show that for ngc4051 the ionization state of the wa responds to the continuum flux as predicted for gas that stays close to photoionization equilibrium , so that other factors , e.g. velocity changes and shocks , do not appear to be important ..
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it is therefore reasonable to assume that the absorbing cloud is photoionized by the continuum radiation from the active galactic nuclei ( agn ) .
this partially ionized optically thin gas along the line of sight to the center of the agn has come to be known as the warm absorber ( hereafter wa ) .
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9,994 |
Suppose that you have an abstract for a scientific paper: we survey some recent results on biconservative surfaces in @xmath0-dimensional space forms @xmath1 with a special emphasis on the @xmath2 and @xmath3 cases .
we study the local and global properties of such surfaces , from extrinsic and intrinsic point of view .
we obtain all non-@xmath4 complete biconservative surfaces in @xmath5 and @xmath6 . .
And you have already written the first three sentences of the full article: the study of submanifolds with constant mean curvature , i.e. , @xmath4 submanifolds , and , in particular , that of @xmath4 surfaces in @xmath0-dimensional spaces , represents a very active research topic in differential geometry for more than @xmath7 years .
there are several ways to generalize these submanifolds .
for example , keeping the @xmath4 hypothesis and adding other geometric hypotheses to the submanifold or , by contrast , in the particular case of hypersurfaces in space forms , studying the hypersurfaces which are `` highly non-@xmath4 '' ..
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the biconservative submanifolds seem to be an interesting generalization of @xmath4 submanifolds .
biconservative submanifolds in arbitrary manifolds ( and in particular , biconservative surfaces ) which are also @xmath4 have some remarkable properties ( see , for example @xcite ) . @xmath4
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9,995 |
Suppose that you have an abstract for a scientific paper: we present a surprisingly short proof that for any continuous map @xmath0 , if @xmath1 , then there exists no bound on the diameter of fibers of @xmath2 .
moreover , we show that when @xmath3 , the union of small fibers of @xmath2 is bounded ; when @xmath4 , the union of small fibers need not be bounded .
applications to data analysis are considered .
high - dimensional data sets are often difficult to analyze directly and , consequently , methods of simplifying them are important to modern data - intensive sciences .
continuous mappings @xmath5 are frequently used to reduce the dimension of large data sets .
indeed , a classic result of johnson and lindenstrauss @xcite shows that for @xmath6 points in any euclidean space , there exists an injective lipschitz function which maps these points into @xmath7 with minimal distortion in pairwise distances .
however , while continuous maps enjoy many desirable properties , the following suggests that a measure of caution should be exercised before employing them for high - dimensional data analysis .
we present a simple proof that for any continuous map @xmath0 , if @xmath1 then there exists no bound on the diameter of fibers of @xmath2 .
therefore , points can be arbitrarily far apart in @xmath8 , yet map to the same point under @xmath2 .
the * fibers * of a map @xmath9 are the preimages @xmath10 of points in @xmath11 .
the * diameter * of a set @xmath12 is the supremum @xmath13 , where @xmath14 denotes the euclidean distance between @xmath15 and @xmath16 .
we begin by considering real - valued functions .
let @xmath17 be a continuous function where @xmath18 .
then for any @xmath19 , there exists @xmath20 whose fiber has diameter greater than @xmath21 .
[ m=1 ] assume that some @xmath22 bounds all fiber diameters .
consider three points @xmath23 such that the distance between any two is @xmath24 , as in figure [ drawing ] .
as @xmath21 bounds the fiber diameters , @xmath25 , @xmath26 , and @xmath27 must be distinct....
And you have already written the first three sentences of the full article: at this point we consider the union of all small fibers . for the remainder of the paper , we consider an arbitrarily chosen but fixed @xmath22 .
we call a nonempty fiber * small * if its diameter is less than @xmath21 .
let @xmath17 be a continuous map where @xmath18 ..
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given three points @xmath50 such that the distance between each pair is at least @xmath21 , no more than two belong to small fibers of @xmath2 .
[ thelemma ] assume that @xmath50 all belong to small fibers .
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9,996 |
Suppose that you have an abstract for a scientific paper: we study inelastic neutrino scattering off hot nuclei for temperatures relevant under supernova conditions .
the method we use is based on the quasiparticle random phase approximation extended to finite temperatures within the thermo field dynamics ( tqrpa ) .
the method allows a transparent treatment of upward and downward transitions in hot nuclei , avoiding the application of brink s hypothesis . for the sample nuclei @xmath0fe and @xmath1ge
we perform a detailed analysis of thermal effects on the strength distributions of allowed gamow - teller ( gt ) transitions which dominate the scattering process at low neutrino energies . for @xmath0fe and @xmath1ge the finite temperature cross - sections are calculated by taking into account the contribution of allowed and forbidden transitions .
the observed enhancement of the cross - section at low neutrino energies is explained by considering thermal effects on the gt strength .
for @xmath0fe we compare the calculated cross - sections to those obtained earlier from a hybrid approach that combines large - scale shell - model and rpa calculations . .
And you have already written the first three sentences of the full article: the significant role played by processes involving neutrinos in core - collapse supernovae ( type ii supernovae ) is well known @xcite . until the core reaches densities of @xmath2 , a substantial amount of the gravitational energy of the collapse
is radiated by neutrinos that leave the star freely . however , at higher densities neutrino interactions with matter become important on the time - scale of the collapse , leading to neutrino trapping and thermalization .
supernova core - collapse simulations require a detailed description of neutrino transport and should in principle include all potentially important neutrino reactions ..
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it was first pointed by haxton @xcite that the neutral - current inelastic neutrino scattering on nuclei involving the excitation of giant resonances can lead to significant neutrino cross - sections and , therefore , this process should be incorporated into core - collapse simulations . shortly thereafter ,
this was done by bruenn and haxton @xcite .
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9,997 |
Suppose that you have an abstract for a scientific paper: the papers in this volume represent a broad spectrum of observational , theoretical , and computational astrophysics , sharing as a unifying core the disk - halo interaction in the milky way and other spiral galaxies .
this topic covers a wide range of galactic and extra - galactic research , built on a foundation of numerous and diverse physical processes .
this summary groups the papers according to six themes , with some historical background and finally a look to the future .
the final message is that the astrophysical techniques discussed and reviewed at this conference will grow over the next decade to answer even more fundamental questions about galaxy evolution and the history of the universe . .
And you have already written the first three sentences of the full article: this conference on the disk - halo interaction in galaxy evolution has been a showcase for many exciting new results in a broad spectrum of galactic and extragalactic research . later in this summary
i will briefly consider the significance of some of these results , and how they show the way forward .
but first a few paragraphs of historical background , for the benefit of people who are new to the field ..
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these concepts were implicit in many of the papers at the conference , but were not often mentioned explicitly . for astrophysicists ,
the disk - halo connection is almost as old as the interstellar medium itself . by the early 1950 s it was clear that both cosmic rays and interstellar clouds must sometimes leave the disk .
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9,998 |
Suppose that you have an abstract for a scientific paper: the sunyaev - zeldovich ( @xcite ; sz ) effect has proven to be an extremely powerful tool to study the physical and evolutionary properties of rich clusters of galaxies .
upcoming sz experiments , with their much improved sensitivity and angular resolution , will provide unique information also on phases of galaxy evolution characterized by the presence of large amounts of hot proto - galactic gas .
we present a preliminary analysis of the sz signals that can be expected at the collapse of the proto - galaxy when , according to the standard scenario , the gas is heated at its virial temperature , and during episodes of strong energy injections from the active nucleus .
the contributions of such signals to excess power on arc - minute scales recently found by cbi and bima experiments are briefly discussed .
address = inaf , osservatorio astronomico di padova , vicolo dellosservatorio 5 , i-35122 padova , altaddress = sissa , via beirut 4 , i-34014 trieste address = iasf - cnr , via gobetti , 101 , i-40129 bologna address = dipartimento fisica , ii universit di roma , via ricerca scientifica 1 , 00133 roma address = sissa , via beirut 4 , i-34014 trieste address = inaf , osservatorio astronomico di padova , vicolo dellosservatorio 5 , i-35122 padova , altaddress = sissa , via beirut 4 , i-34014 trieste address = dipartimento fisica , ii universit di roma , via ricerca scientifica 1 , 00133 roma address = dipartimento di fisica , universit di milano , via celoria 16 , i-20133 milano address = inaf , osservatorio astronomico di trieste , via g.b .
tiepolo 11 , i-34131 trieste .
And you have already written the first three sentences of the full article: the currently standard hierarchical clustering paradigm for large scale structure formation in a @xmath0cdm universe has successfully confronted a broad variety of observations , ranging from the formation of galaxy clusters , to large scale velocity fields , to power spectra of the galaxy distribution and of the microwave background , and more ( see , e.g. , @xcite ) . however , the theory of formation and evolution of galaxies is not in a very satisfactory state .
serious challenges have emerged in the last years ( @xcite ) : the excess of predicted small scale structure ; the persistent inability of even the best semi - analytic models ( @xcite ) to account for the surface density of massive galaxies at substantial redshifts detected by ( sub)-mm surveys with scuba and mambo ( @xcite ) and by deep k - band surveys ( @xcite ) ; the difficulties to account for the distribution of velocity dispersions of low - ionization damped lyman-@xmath1 systems at @xmath2 ( @xcite ) ; the low predicted specific angular momentum of galactic disks ( @xcite ) ; the observational evidence contradicting the existence of the central cusp in the dark matter distribution , predicted by numerical simulations ( @xcite ) . on larger scales ,
the observed relationship between x - ray luminosity and gas temperature for groups of galaxies strongly deviates from expectations of the simplest hierarchical clustering models ..
Please generate the next two sentences of the article
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solutions of these problems may require advances in different fields that may include particle physics ( self - interacting dark matter ? ) , deviations from a power law of the power spectrum of primordial density perturbations ( as may be suggested by wmap data , @xcite ) , or the astrophysics of galaxy formation and evolution . in any case
, a better understanding of the complex physical processes governing the galaxy formation is mandatory .
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9,999 |
Suppose that you have an abstract for a scientific paper: we study the impact of structural variations ( that is slowly varying geometry aberrations and internal strain fields ) on the width and shape of the stimulated brillouin scattering ( sbs ) resonance in nanoscale waveguides . we find that they lead to an inhomogeneous resonance broadening through two distinct mechanisms : firstly , the acoustic frequency is directly influenced via mechanical nonlinearities ; secondly , the optical wave numbers are influenced via the opto - mechanical nonlinearity leading to an additional acoustic frequency shift via the phase - matching condition .
we find that this second mechanism is proportional to the opto - mechanical coupling and , hence , related to the sbs - gain itself .
it is absent in intra - mode forward sbs , while it plays a significant role in backward scattering .
in backward sbs increasing the opto - acoustic overlap beyond a threshold defined by the fabrication tolerances will therefore no longer yield the expected quadratic increase in overall stokes amplification .
finally , we illustrate in a numerical example that in backward sbs and inter - mode forward sbs the existence of two broadening mechanisms with opposite sign also opens the possibility to compensate the effect of geometry - induced broadening .
our results can be transferred to other micro- and nano - structured waveguide geometries such as photonic crystal fibres . .
And you have already written the first three sentences of the full article: stimulated brillouin scattering ( sbs ) is a nonlinear and self - amplifying interaction between guided optical waves and hypersound waves in waveguides @xcite .
the scattering of light from mechanical vibrations was first predicted by brillouin in 1922 @xcite ; the stimulated version of this process was first experimentally demonstrated @xcite shortly after the invention of the laser by chiao et al . and
has since been used successfully to characterize materials at hypersonic frequencies @xcite . following the general trend of miniaturization ,.
Please generate the next two sentences of the article
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sbs has been studied and applied in ever smaller structures such as nano - structured optical fibres @xcite and even waveguides integrated on a chip @xcite . in these systems
sbs ceases to be a bulk effect and surface effects strongly come into play most prominently radiation pressure appears as a second major interaction process in addition to the bulk photoelastic effect . due to this additional coupling as well as the very tight mode confinement ,
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