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7,300 | Suppose that you have an abstract for a scientific paper: we show that if the visible universe is a membrane embedded in a higher - dimensional space , particles in uniform motion radiate gravitational waves because of spacetime lumpiness .
this phenomenon is analogous to the electromagnetic diffraction radiation of a charge moving near to a metallic grating . in the gravitational case ,
the role of the metallic grating is played by the inhomogeneities of the extra - dimensional space , such as a hidden brane .
we derive a general formula for gravitational diffraction radiation and apply it to a higher - dimensional scenario with flat compact extra dimensions .
gravitational diffraction radiation may carry away a significant portion of the particle s initial energy .
this allows to set stringent limits on the scale of brane perturbations .
physical effects of gravitational diffraction radiation are briefly discussed . .
And you have already written the first three sentences of the full article: larmor s formula of electromagnetism @xcite states that an electric charge in uniform motion does not radiate . however , there are two ways to have radiation from a charge moving with constant velocity .
the first way is to have a particle moving in a medium with velocity exceeding the phase velocity of light in that medium .
this gives rise to the well - known vavilov - cherenkov radiation @xcite ..
Please generate the next two sentences of the article | the second way is to consider charge motion in inhomogeneous media .
ginzburg and frank @xcite first discussed this effect by investigating a particle in uniform motion which crosses a planar interface between two media with dissimilar refractive index . |
7,301 | Suppose that you have an abstract for a scientific paper: as a critical part of the tracking active galactic nuclei with austral milliarcsecond interferometry ( tanami ) program @xcite , in november 2007 the australia telescope compact array ( atca ) started monitoring the radio spectra of a sample of southern hemisphere active galactic nuclei ( agn ) that were selected as likely candidates for detection ( as well as a control sample ) by the large area telescope ( lat ) aboard the _ fermi gamma ray space observatory_. the initial sample was chosen based on properties determined from agn detections by the energetic gamma ray experiment telescope ( egret ) .
most of the initial sample has been detected by _
fermi_/lat and with the addition of new detections the sample has grown to include 226 agn , 133 of which have data for more than one epoch . for the majority of these agn , our monitoring program provides the only dynamic radio spectra available .
the atca receiver suite makes it possible to observe several sources at frequencies between 4.5 and 41 ghz in a few hours , resulting in an excellent measure of spectral index at each epoch . by examining how the spectral index changes over time , we aim to investigate the mechanics of radio and @xmath0-ray emission from agn jets . .
And you have already written the first three sentences of the full article: results from egret revealed a very strong link between @xmath0-ray emission in agn and core - dominated radio emission from relativistic jets , which may originate from super - massive black hole and accretion disk systems @xcite .
recent _ fermi _ data have confirmed this @xcite .
observations at radio wavelengths were critically important for the understanding of the @xmath0-ray emission mechanism in these agn ..
Please generate the next two sentences of the article | in particular , the relative timing of @xmath0-ray flares and radio outbursts provides constraints on the mechanisms and location of the flare origin @xcite .
the main models for @xmath0-ray emission entail inverse compton scattering of low energy photons to high energies by the relativistic electron population in the agn jets . |
7,302 | Suppose that you have an abstract for a scientific paper: the introduction of a steady - state spatially - periodic raman coupling between two components of an ultracold atomic gas produces a dressed - state gas with an anisotropic and tunable dispersion relation . a bose - einstein condensate formed in such a gas is consequently characterized by an anisotropic superfluid critical velocity . the anisotropic dissipation of superfluid flow is quantified by considering the scattering of impurities flowing through this superfluid
a gradual transition from the isotropic nature of an uncoupled bose - einstein condensate to the anisotropic periodically - dressed condensate is obtained as the strength of the raman coupling is varied .
these results present a clear signature for future experiemental realizations of this novel superfluid .
the experimental attainment of quantum degenerate dilute gases , composed of both bosonic and fermionic atoms , has created many new opportunities in the study of quantum fluids . in particular , recent years have seen a flurry of experimental studies of superfluidity in dilute , scalar bose - einstein condensates .
these include the observations of critical velocities for superfluid flow about microscopic @xcite and macroscopic @xcite obstacles , the onset of turbulent flow above this critical velocity @xcite , beautiful studies of quantized vortices and vortex lattices in rotating bose - einstein condensates @xcite , and other manifestations of irrotational superfluid flow @xcite .
these experiments are closely analogous to those performed on another scalar superfluid , liquid @xmath0he , but apply new experimental probes and allow new insights due to the vastly different parameter regime of the dilute atomic gases , and their amenability to a new set of tools for manipulation and probing .
dilute atomic gases also offer the opportunity to create novel quantum fluids by using these various tools to manipulate the internal and external states of the atoms comprising the superfluid .
for example , different types of....
And you have already written the first three sentences of the full article: as presented in ref .
@xcite , a periodically - dressed bose - einstein condensate ( pdbec ) is formed of atoms of mass @xmath3 with two internal states , @xmath4 and @xmath5 , separated by an energy difference @xmath6 . these atoms are exposed continuously to two laser beams of wavevectors @xmath7 and @xmath8 and frequencies @xmath9 and @xmath10 , which couple the states @xmath4 and @xmath5 via a raman transition ( see figure [ fig : scheme ] ) .
in such a raman transition , an atom in internal state @xmath4 with wavevector @xmath11 absorbs a photon from beam @xmath12 and emits a photon into beam @xmath13 , arriving in internal state @xmath5 with wavevector @xmath14 gaining a momentum @xmath15 and a kinetic energy @xmath16 . and.
Please generate the next two sentences of the article | @xmath10 induce raman transitions between internal states @xmath17 and @xmath18 . the beams share a common large detuning @xmath19 from the excited atomic state , and this state is adiabatically eliminated in the theoretical treatment .
the lasers are detuned by an amount @xmath20 from the two - photon raman transition . |
7,303 | Suppose that you have an abstract for a scientific paper: light axion like particles ( alps ) that couple to two photons are allowed in a number of proposed extensions to the standard model of elementary particles . of particular interest from a theoretical and observational standpoint
is the energy regime near 0.1 mev .
we present results from a pilot experiment to search for a signal from a 0.14 mev scalar alp by way of its coupling to two photons . using a copper resonant cavity cooled to four degrees kelvin while immersed in a seven tesla magnetic field , and coupled to a low noise cryogenic amplifier and room temperature receiver
, we exclude an alp driven excess of 34 ghz photons with g @xmath010@xmath1/gev with 5@xmath2 confidence .
we discuss the ramifications of this initial measurement as well as planned modifications to the experiment for increased sensitivity . .
And you have already written the first three sentences of the full article: several theories of particle physics as well as cosmology predict the existence of at least one sub
ev scalar , that is , spin - zero , boson @xcite .
correspondingly , many theories of physics beyond the standard model ( sm ) can accommodate scalars with very small masses and feeble couplings to sm fields @xcite ..
Please generate the next two sentences of the article | an intriguing possibility in astrophysics and cosmology is that these weakly interacting , sub ev particles ( wisps ) may constitute at least some component of the cold dark matter in the universe @xcite .
it has been shown that these arguments apply for both pseudoscalar , namely axion @xcite , and scalar @xcite wisps , e.g. axion like particles ( alps ) that couple to two photons . |
7,304 | Suppose that you have an abstract for a scientific paper: we perform three - dimensional ( 3d ) compressible mhd simulations over many dynamical times for an extended range of sonic and alfvn mach numbers and analyze the statistics of 3d density and 2d column density , which include probability distribution functions , spectra , skewness , kurtosis , she - lvque exponents , and genus . in order to establish the relation between the statistics of the observables , i.e. column densities , and the underlying 3d statistics of density
, we analyze the effects of cloud boundaries .
we define the parameter space for 3d measures to be recovered from column densities .
in addition , we show that for subsonic turbulence the spectra of density fluctuations are consistent with @xmath0 in the case of a strong magnetic field and @xmath1 in the case of a weak magnetic field . for supersonic turbulence
we confirm the earlier findings of the shallow spectra of density and kolmogorov spectra of the logarithm of density .
we find that the intermittencies of the density and velocity are very different . .
And you have already written the first three sentences of the full article: magnetohydrodynamic ( mhd ) turbulence is a key element for understanding star formation ( see * ? ? ?
* ; * ? ? ?
* and references therein ) ..
Please generate the next two sentences of the article | in a new emerging paradigm , density perturbations produced by compressible mhd turbulence create molecular clouds and clumps within the clouds .
this makes studies of density statistics very timely . |
7,305 | Suppose that you have an abstract for a scientific paper: here we show that in the case when double peaked emission lines originate from outer parts of accretion disk , their variability could be caused by perturbations in the disk emissivity . in order to test this hypothesis
, we introduced a model of disk perturbing region in the form of a single bright spot ( or flare ) by a modification of the power law disk emissivity in appropriate way .
the disk emission was then analyzed using numerical simulations based on ray - tracing method in kerr metric and the corresponding simulated line profiles were obtained .
we applied this model to the observed h@xmath0 line profiles of 3c 390.3 ( observed in the period 1995 - 1999 ) , and estimated the parameters of both , accretion disk and perturbing region .
our results show that two large amplitude outbursts of the h@xmath0 line observed in 3c 390.3 could be explained by successive occurrences of two bright spots on approaching side of the disk .
these bright spots are either moving , originating in the inner regions of the disk and spiralling outwards by crossing small distances during the period of several years , or stationary . in both cases ,
their widths increase with time , indicating that they most likely decay . .
And you have already written the first three sentences of the full article: the huge amount of active galactic nucleus ( agn ) energy is released through accretion onto super - massive black hole ( bh ) , supposed to exist in the center of agn .
the emission of the accretion disk is not only in the continuum , but also in the emission lines ( e.g. in fe k@xmath1 line ) and in low ionization lines , as e.g. in broad balmer emission lines which are seen as double peaked ( dp ) .
dp balmer lines are found in 20% of radio loud agn at @xmath2 @xcite and 4% of the sloan digital sky survey ( sdss ) quasars at @xmath3 @xcite ..
Please generate the next two sentences of the article | broad , double - peaked emission lines of agn provide dynamical evidence for presence of an accretion disk feeding a supermassive black hole in the center of agn .
but in some cases , the variability of these lines shows certain irregularities which could not be explained just by standard model of accretion disk . |
7,306 | Suppose that you have an abstract for a scientific paper: we construct an analytic model for the mass distributions of superclusters and clusters in each supercluster .
our model is a modification of the press - schechter theory , and defines superclusters as the regions that have some overdensity smaller than those for usual virialized objects .
we compare the mass functions with a catalog of superclusters in the sloan digital sky survey early data release and found that they are in reasonable agreement with each other . .
And you have already written the first three sentences of the full article: it is now known that our universe is hierarchical .
the largest virialized objects in the universe are clusters that are made of hundreds of galaxies .
clusters have extensively been used to test structure formation models in the universe , through their abundances and correlations@xcite ..
Please generate the next two sentences of the article | superclusters are defined as an ensemble of clusters .
they are still assembling , and are even larger structure than clusters ; superclusters have extents of @xmath0 or even larger . |
7,307 | Suppose that you have an abstract for a scientific paper: we present a monitoring study of sn 2004a and probable discovery of a progenitor star in pre - explosion _ hst _ images .
the photometric and spectroscopic monitoring of sn 2004a show that it was a normal type ii - p which was discovered in ngc 6207 about two weeks after explosion .
we compare sn 2004a to the similar type ii - p sn 1999em and estimate an explosion epoch of 2004 january 6 .
we also calculate three new distances to ngc 6207 of @xmath0 , @xmath1 and @xmath2mpc .
the former was calculated using the standard candle method ( scm ) for , and the latter two from the brightest supergiants method ( bsm ) .
we combine these three distances with existing kinematic distances , to derive a mean value of . using this distance
we estimate that the ejected nickel mass in the explosion is @xmath3 .
the progenitor of sn 2004a is identified in pre - explosion wfpc2 f814w images with a magnitude of @xmath4 , but is below the detection limit of the f606w images .
we show that this was likely a red supergiant ( rsg ) with a mass of @xmath5 .
the object is detected at 4.7@xmath6 above the background noise . even if this detection is spurious
, the 5@xmath6 upper limit would give a robust upper mass limit of 12 for a rsg progenitor .
these initial masses are very similar to those of two previously identified rsg progenitors of the type ii - p sne 2004gd ( @xmath7 ) and 2005cs ( @xmath5 ) .
[ firstpage ] stars : evolution - supernovae : general - supernovae : individual : sn 2004a - galaxies : individual : ngc 6207 - galaxies : distances and redshifts .
And you have already written the first three sentences of the full article: supernovae ( sne ) are associated with the deaths of stars , in particular core - collapse supernovae ( ccsne ) are associated with the deaths of massive stars , which have initial masses greater than about 8 .
sne are principally separated into two categories , those without hydrogen ( type i ) and those with ( type ii ) .
only type ia sne are thought to be thermonuclear explosions , which arise from accreting white dwarfs in binary stellar systems ..
Please generate the next two sentences of the article | all the other sub - types are thought to be initiated by the core collapsing in massive stars .
the type of sn that occurs depends on the massive star s evolutionary stage at the time of the explosion . |
7,308 | Suppose that you have an abstract for a scientific paper: this paper is related to our previous works @xcite @xcite on the error estimate of the averaging technique , for systems with one fast angular variable . in the cited references , a general method ( of mixed analytical and numerical type )
has been introduced to obtain precise , fully quantitative estimates on the averaging error . here
, this procedure is applied to the motion of a satellite in a polar orbit around an oblate planet , retaining only the @xmath0 term in the multipole expansion of the gravitational potential . to exemplify the method ,
the averaging errors are estimated for the data corresponding to two earth satellites ; for a very large number of orbits , computation of our estimators is much less expensive than the direct numerical solution of the equations of motion .
p h v s l o _0 _
m 1*t*^1 s 1 _ addtoresetequationsection on the averaging principle for one - frequency systems .
an application to satellite motions .
carlo morosi@xmath1 , livio pizzocchero@xmath2 + @xmath1 dipartimento di matematica , politecnico di milano , + p.za l. da vinci 32 , i-20133 milano , italy + e mail : [email protected] + @xmath2 dipartimento di matematica , universit di milano + via c. saldini 50 , i-20133 milano , italy + and istituto nazionale di fisica nucleare , sezione di milano , italy + e mail : [email protected] * keywords : * slow and fast motions , perturbations , averaging method .
* ams 2000 subject classification * : 70k65 , 70k70 , 34c29 , 70h09 , 37j40 , 70f15 . .
And you have already written the first three sentences of the full article: celestial mechanics often requires approximation techniques to compute the motion of bodies over very long times .
giving reliable error estimates on these techniques is a very practical problem , of not simple solution . in this paper
we apply to a typical astronomical problem the general scheme of @xcite @xcite to estimate the error of the averaging principle , in the case of one fast angular variable @xmath3 ( in the one - dimensional torus ) and many slow variables @xmath4 ( the actions ) ..
Please generate the next two sentences of the article | the application we consider refers to the motion of a satellite around an oblate planet : of course , oblateness gives a perturbation of the keplerian , purely radial gravitational potential .
there is a classical way to express the perturbed potential as a series of spherical harmonics , where the multipole moments of the planetary mass distribution appear as coefficients . in the case of axial symmetry , this series only involves zonal harmonics and the @xmath5-th term contains a multipole coefficient @xmath6 ( for a reminder , see subsection and references therein ) . for a slightly oblate planet , all these coefficients |
7,309 | Suppose that you have an abstract for a scientific paper: we describe constructing solutions of the field equations of chern - simons and topological bf theories in terms of deformation theory of locally constant ( flat ) bundles
. maps of flat connections into one another ( dressing transformations ) are considered .
a method of calculating ( nonlocal ) dressing symmetries in chern - simons and topological bf theories is formulated .
journal of nonlinear mathematical physics 2000 , v.7 , n 4 , . [ firstpage ] .
And you have already written the first three sentences of the full article: let @xmath0 be an oriented smooth manifold of dimension @xmath1 , @xmath2 a semisimple lie group , @xmath3 its lie algebra , @xmath4 a principal @xmath2-bundle over @xmath0 , @xmath5 a connection 1-form on @xmath4 and @xmath6 its curvature .
we assume that @xmath0 is a compact manifold without boundary .
a connection 1-form @xmath5 on @xmath4 is called _ flat _ if its curvature @xmath7 vanishes , @xmath8 locally eqs.(1.1a ) are solved trivially , and on any sufficiently small open set @xmath9 we have @xmath10 , where @xmath11 ..
Please generate the next two sentences of the article | so , locally @xmath5 is a pure gauge .
but globally eqs.(1.1a ) are nontrivial , and finding their solutions is not an easy problem . |
7,310 | Suppose that you have an abstract for a scientific paper: we study an unconventional two - dimensional , two - component classical plasma on a sphere , with emphasis on detecting signatures of melting transitions .
this system is relevant to ising - type quantum hall states , and is unconventional in the sense that it features particles interacting via two different two - dimensional coulomb interactions .
one species of particles in the plasma carries charge of both types @xmath0 , while the other species carries only charge of the second type @xmath1 .
we find signatures of a freezing transition at @xmath2 .
this means that the species with charge of both types will form a wigner crystal , whereas the species with charge of the second type also shows signatures of being a wigner crystal , due to the attractive inter - component interaction of the second type .
moreover , there is also a berezinskii - kosterlitz - thouless phase transition at @xmath3 , at which the two species of particles bind to form molecules that are neutral with respect to the second coulomb interaction .
these two transitions appear to be independent of each other , giving a rectangular phase diagram . as a special case , @xmath4 describes the ( conventional ) two - dimensional one - component plasma .
our study is consistent with previous studies of this plasma , and sheds new light on the freezing transition of this system . .
And you have already written the first three sentences of the full article: multi - component quantum condensates with novel types of inter - component interactions are of considerable interest in contemporary physics .
for example , they are relevant to widely disparate systems , including low - dimensional spin-@xmath5 quantum antiferromagnets @xcite , bose - einstein condensates @xcite , multi - component / multi - band superconductors @xcite , and non - abelian quantum hall states and topological superconductors @xcite .
these systems have the remarkable property of possessing a mapping to a classical multi - component plasma system with highly unusual intra- and inter - component interactions ..
Please generate the next two sentences of the article | the statistical properties of these unconventional plasmas especially their phase diagrams have important ramifications for the physics of their corresponding fractional quantum hall systems @xcite .
the statistical physics of such systems has only recently begun to be explored . in a previous paper , we investigated the metal - insulator transition in a particular version of such a plasma @xcite . in this paper , we will extend these investigations to a study of the freezing of such a plasma from a liquid to a wigner crystal . the canonical partition function of the unconventional two - component plasma that we investigate is given by @xcite @xmath6 where the potential energy @xmath7 describes two species ( components ) of particles interacting via two different types of two - dimensional ( 2d ) coulomb interactions , which are logarithmic . here |
7,311 | Suppose that you have an abstract for a scientific paper: the faint irregular galaxies gmrt survey ( figgs ) is a giant metrewave radio telescope ( gmrt ) based hi imaging survey of a systematically selected sample of extremely faint nearby dwarf irregular galaxies .
the primary goal of figgs is to provide a comprehensive and statistically robust characterization of the neutral inter - stellar medium properties of faint , gas rich dwarf galaxies .
the figgs galaxies represent the extremely low - mass end of the dwarf irregular galaxies population , with a median m@xmath0 and median hi mass of @xmath1 m@xmath2 , extending the baseline in mass and luminosity space for a comparative study of galaxy properties .
the hi data is supplemented with observations at other wavelengths .
in addition , distances accurate to @xmath3 10% are available for most of the sample galaxies .
this paper gives an introduction to figgs , describe the gmrt observations and presents the first results from the hi observations . from the figgs data we confirm the trend of increasing hi to optical diameter ratio with decreasing optical luminosity ;
the median ratio of d@xmath4/d@xmath5 for the figgs sample is 2.4 .
further , on comparing our data with aperture synthesis surveys of bright spirals , we find at best marginal evidence for a decrease in average surface density with decreasing hi mass . to a good approximation
the disks of gas rich galaxies , ranging over 3 orders of magnitude in hi mass , can be described as being drawn from a family with constant hi surface density .
[ firstpage ] galaxies : dwarf galaxies : kinematics and dynamics radio lines : galaxies .
And you have already written the first three sentences of the full article: hi 21 cm aperture synthesis observations of nearby spiral galaxies is a mature field with over three decades of history
probably something of the order of a thousand galaxies have already been imaged .
however observers have tended to focus on bright ( @xmath3 l@xmath6 ) galaxies with hi masses @xmath7 m@xmath2 ..
Please generate the next two sentences of the article | hi observations of faint dwarf galaxies ( m@xmath8 ) generally require comparatively long integration times , and such galaxies have hence not been studied in similar numbers .
while there have been some systematic hi surveys of dwarf galaxies ( @xcite ) , these have generally been restricted to the brighter ( m@xmath9 ) dwarfs . in hierarchical models of galaxy formation , nearby dwarf galaxies would , in some ways , be analogs of the primordial building blocks of large galaxies . |
7,312 | Suppose that you have an abstract for a scientific paper: with the availability of considerably more data , we revisit the question of how special our solar system is , compared to observed exoplanetary systems . to this goal , we employ a mathematical transformation that allows for a meaningful , statistical comparison .
we find that the masses and densities of the giant planets in our solar system are very typical , as is the age of the solar system . while the orbital location of jupiter is somewhat of an outlier , this is most likely due to strong selection effects towards short - period planets .
the eccentricities of the planets in our solar system are relatively small compared to those in observed exosolar systems , but still consistent with the expectations for an 8-planet system ( and could , in addition , reflect a selection bias towards high - eccentricity planets ) .
the two characteristics of the solar system that we find to be most special are the lack of super - earths with orbital periods of days to months and the general lack of planets inside of the orbital radius of mercury .
overall , we conclude that in terms of its broad characteristics our solar system is not expected to be extremely rare , allowing for a level of optimism in the search for extrasolar life .
[ firstpage ] .
And you have already written the first three sentences of the full article: the discovery of thousands of extrasolar planets and planet candidates in recent years ( see , e.g. , * ? ? ?
* ; * ? ? ?
* ; * ? ? ?.
Please generate the next two sentences of the article | * ; * ? ? ?
* ; * ? ? ? |
7,313 | Suppose that you have an abstract for a scientific paper: the result of a search for neutrino bursts from supernova explosions using the super - kamiokande detector is reported .
super - kamiokande is sensitive to core - collapse supernova explosions via observation of their neutrino emissions .
the expected number of events comprising such a burst is @xmath0 and the average energy of the neutrinos is in few tens of mev range in the case of a core - collapse supernova explosion at the typical distance in our galaxy ( 10 kiloparsecs ) ; this large signal means that the detection efficiency anywhere within our galaxy and well past the magellanic clouds is 100% .
we examined a data set which was taken from may , 1996 to july , 2001 and from december , 2002 to october , 2005 corresponding to 2589.2 live days .
however , there is no evidence of such a supernova explosion during the data - taking period . the 90% c.l .
upper limit on the rate of core - collapse supernova explosions out to distances of 100 kiloparsecs is found to be 0.32 sn @xmath1 year@xmath2 . .
And you have already written the first three sentences of the full article: on the 23rd of february , 1987 , the kamiokande ii , imb , and baksan experiments observed the neutrino burst from sn1987a , which was located in the large magellanic cloud @xcite .
this was the first detection of a supernova s neutrino burst , and it introduced a new method of investigation : neutrino astronomy .
super - kamiokande ( super - k , sk ) is an imaging water cherenkov detector containing 50,000 tons of pure water ; it is the successor to the kamiokande detector ..
Please generate the next two sentences of the article | super - k is located 1000 meters underground ( 2,700 meters of water equivalent ) in the kamioka zinc mine in the gifu prefecture of japan , at 36.4@xmath3n , 137.3@xmath3e and 25.8@xmath3n geomagnetic latitude .
the detector consists of a main inner detector and an outer veto detector . |
7,314 | Suppose that you have an abstract for a scientific paper: it is shown , that primary proton spectrum , reconstructed from sea - level and underground data on muon spectrum with the use of qgsjet 01 , qgsjet ii , nexus 3.97 and sibyll 2.1 interaction models , demonstrates not only model - dependent intensity , but also model - dependent form . for correct reproduction of muon spectrum shape primary proton flux should have non - constant power index for all
considered models , except sibyll 2.1 , with break at energies around 1015 tev and value of exponent before break close to that obtained in atic-2 experiment . to validate presence of this break understanding of inclusive spectra behavior in fragmentation region in p - air collisions should be improved , but we show , that it is impossible to do on the basis of the existing experimental data on primary nuclei , atmospheric muon and hadron fluxes . .
And you have already written the first three sentences of the full article: at present information on the characteristics of hadronic interactions in fragmentation region is still scarce or missing and experiments with ` roman pots ' are anticipated to improve the situation .
some of this information , in principle , could be obtained with the use of the data on cosmic ray ( cr ) muon and hadron spectra , provided primary spectra are known with high precision , but that is not the case .
the obvious obstacle here is that at high energies primary cosmic ray ( pcr ) fluxes , measured in direct experiments , themselves are functionals of various interaction parameters plus their accuracy is appreciably affected by additional systematic effects @xcite . in the series of our papers.
Please generate the next two sentences of the article | @xcite we underlined , that these effects can lead to underestimation of light nuclei fluxes and thus can explain discrepancy between measured and calculated muon fluxes for @xmath0 gev .
preliminary data of atic-2 @xcite , covering the gap between magnetic spectrometer and emulsion chamber experiments , seems to be in concordance with our conclusions , but situation is more complicated in fact , as further consideration will show . |
7,315 | Suppose that you have an abstract for a scientific paper: we consider the recently suggested model for some resonances near the open charm threshold as bound states of charmonium inside excited light mesons . it is argued in the soft - wall holographic model of qcd that such states of heavy quarkonium necessarily exist at sufficiently large spin of the light meson .
the bound state is provided by the dilaton exchange through the 5d bulk .
we also argue that the decay of such bound systems into mesons with open heavy flavors due to splitting of the heavy quarkonium can be treated as semiclassical tunneling and is suppressed .
this behavior is in agreement with the known relative suppression of the decay of the discussed charmonium - like resonances into channels with @xmath0 mesons .
* william i. fine theoretical physics institute + university of minnesota + * itep - th-18/08 + ftpi - minn-08/12 + umn - th-2643/08 + april 2008 + * holographic hadro - quarkonium + * school of physics and astronomy , university of minnesota , + minneapolis , mn 55455 , usa , + * a. gorsky + * institute of theoretical and experimental physics , moscow , 117218 , russia + and + * m.b .
voloshin + * william i. fine theoretical physics institute , university of minnesota , + minneapolis , mn 55455 , usa + and + institute of theoretical and experimental physics , moscow , 117218 , russia + .
And you have already written the first three sentences of the full article: recent observation of resonances near the open charm threshold which decay into a specific charmonium state , @xmath1 or @xmath2 , and two or even one pion with no other observed conspicuous decay channels@xcite suggests@xcite that these resonances in fact contain the specific charmonium state ` coated ' by an excited light - hadron matter .
it has been further argued@xcite that such hadro - charmonium systems are likely to arise due to binding of charmonium inside sufficiently excited light resonances through a qcd analog of the van der waals interaction . in this paper
we investigate in some detail the interaction of heavy quarkonium with excited light mesons within the simplest soft wall model of holographic qcd@xcite which provides linear behavior of regge trajectories@xcite and a reasonable behavior of a heavy - quark potential@xcite . in this approach.
Please generate the next two sentences of the article | the mesons can be considered as modes of the flavor gauge field in 5d theory ( vector mesons ) or a wilson line of this gauge field along the fifth coordinate ( @xmath3-meson ) .
large - spin mesons can be considered within this approach as well . |
7,316 | Suppose that you have an abstract for a scientific paper: some aspects of @xmath0 physics relevant for experiments in hadron colliders are discussed .
these include the determination of parameters of the ckm matrix and confirmation of its role in cp violation , studies of mixing of nonstrange and strange @xmath0 mesons , lifetimes of hadrons containing @xmath1 quarks , the use of `` same - side '' tagging of neutral @xmath0 mesons via correlations with charged pions through fragmentation or resonances , and the determination of ckm phases through the study of decays of @xmath0 mesons to pairs of light hadrons . .
And you have already written the first three sentences of the full article: while the first states containing the @xmath1 quark , the @xmath2 resonances , were discovered in hadronic interactions at fermilab @xcite , the study of @xmath0 mesons for many years has been largely the province of @xmath3 colliders . with the reconstruction of large numbers of exclusive @xmath0 decays by the cdf collaboration @xcite , that situation now has the potential to change .
the present talk outlines some of the ways in which hadron colliders can exploit their innate advantage of large @xmath0 production rates to provide information complementary and in many cases superior to that available in electron - positron collisions .
we begin in sec ..
Please generate the next two sentences of the article | ii with a discussion of the cabibbo - kobayashi - maskawa ( ckm ) matrix @xcite and its role in cp violation as currently observed in the neutral kaon system .
the role of @xmath0 mesons in checking this picture is outlined in sec . |
7,317 | Suppose that you have an abstract for a scientific paper: in recent papers , a model of a two - sheeted spacetime @xmath0 was introduced and the quantum dynamics of massive fermions was studied in this framework . in the present study , we show that the physical predictions of the model are perfectly consistent with observations and most important , it can solve the puzzling problem of the four - dimensional localization of the fermion species in multidimensional spacetimes .
it is demonstrated that fermion localization on the sheets arises from the combination of the discrete bulk structure and environmental interactions .
the mechanism described in this paper can be seen as an alternative to the domain wall localization arising in continuous five dimensional spacetimes .
although tightly constrained , motions between the sheets are , however , not completely prohibited . as an illustration , a resonant mechanism through which fermion oscillations between the sheets might occur is described . .
And you have already written the first three sentences of the full article: extradimensions are the backbone of present theoretical physics . during the last years
, there has been a considerable interest in kaluza - klein like scenarios suggesting that our usual spacetime could be just a slice of a larger dimensional manifold .
recent advances in string theory have thus postulated the existence of `` braneworlds '' ( @xmath1-hyperdimensional surfaces embedded in a @xmath2 dimensional manifold ) in which we are living on [ 1,2 ] ..
Please generate the next two sentences of the article | several issues like the hierarchy between the electroweak and the planck scales [ 3,4 ] as well as the idea that the post - inflationary epoch of our universe was preceded by the collision of d3-branes [ 5 ] , for instance , have been successfully addressed in such multidimensional approaches .
+ in braneworld models , it is generally assumed that the standard model particles can not freely propagate into unseen dimensions and must be constrained to live on a @xmath3 submanifold [ 1,2 ] . |
7,318 | Suppose that you have an abstract for a scientific paper: linearizability is a commonly accepted notion of correctness for libraries of concurrent algorithms .
unfortunately , it assumes a complete isolation between a library and its client , with interactions limited to passing values of a given data type .
this is inappropriate for common programming languages , where libraries and their clients can communicate via the heap , transferring the ownership of data structures , and can even run in a shared address space without any memory protection . in this paper
, we present the first definition of linearizability that lifts this limitation and establish an abstraction theorem : while proving a property of a client of a concurrent library , we can soundly replace the library by its abstract implementation related to the original one by our generalisation of linearizability .
this allows abstracting from the details of the library implementation while reasoning about the client .
we also prove that linearizability with ownership transfer can be derived from the classical one if the library does not access some of data structures transferred to it by the client . .
And you have already written the first three sentences of the full article: the architecture of concurrent software usually exhibits some forms of modularity . for example , concurrent algorithms are encapsulated in libraries and complex algorithms are often constructed using libraries of simpler ones .
this lets developers benefit from ready - made libraries of concurrency patterns and high - performance concurrent data structures , such as @xmath0 for java and threading building blocks for c++ . to simplify reasoning about concurrent software
, we need to exploit the available modularity ..
Please generate the next two sentences of the article | in particular , in reasoning about a client of a concurrent library , we would like to abstract from the details of a particular library implementation .
this requires an appropriate notion of library correctness . |
7,319 | Suppose that you have an abstract for a scientific paper: in this paper we establish some parabolicity criteria for maximal surfaces immersed into a lorentzian product space of the form @xmath0 , where @xmath1 is a connected riemannian surface with non - negative gaussian curvature and @xmath0 is endowed with the lorentzian product metric @xmath2 . in particular , and as an application of our main result , we deduce that every maximal graph over a starlike domain @xmath3 is parabolic .
this allows us to give an alternative proof of the non - parametric version of the calabi - bernstein result for entire maximal graphs in . .
And you have already written the first three sentences of the full article: a _ maximal _ surface in a @xmath4dimensional lorentzian manifold is a spacelike surface with zero mean curvature . here by _
spacelike _ we mean that the induced metric from the ambient lorentzian metric is a riemannian metric on the surface .
the mathematical interest of maximal surfaces resides in the fact that they locally maximize area among all nearby surfaces having the same boundary @xcite ..
Please generate the next two sentences of the article | furthermore , maximal surfaces and , more generally spacelike surfaces with constant mean curvature , have also a great importance in general relativity @xcite .
parabolicity is a concept that lies in the borderline between several branches of mathematics , such as riemannian geometry , stochastic analysis , partial differential equations and potential theory . |
7,320 | Suppose that you have an abstract for a scientific paper: we present ecom ( equilibrium solver via conformal mapping ) , a fast and accurate fixed boundary solver for toroidally axisymmetric magnetohydrodynamic equilibria with or without a toroidal flow .
ecom combines conformal mapping and fourier and integral equation methods on the unit disk to achieve exponential convergence for the poloidal flux function as well as its first and second partial derivatives . as a consequence of its high order accuracy , for dense grids and tokamak - like
elongations ecom computes key quantities such as the safety factor and the magnetic shear with higher accuracy than the finite element based code chease [ h. ltjens _ et al .
_ , computer physics communications 97 , 219 ( 1996 ) ] at equal run time .
ecom has been developed to provide equilibrium quantities and details of the flux contour geometry as inputs to stability , wave propagation and transport codes . .
And you have already written the first three sentences of the full article: numerically computed magnetohydrodynamic ( mhd ) equilibria are the starting point of a wide class of numerical solvers that are used to study mhd stability , transport , and heating and current drive in magnetic fusion devices @xcite .
static mhd equilibria of toroidally axisymmetric configurations are described by the grad - shafranov ( g - s ) equation @xcite , a nonlinear , second - order elliptic partial differential equation .
stationary equilibria with purely toroidal flows are determined by solving a close variant of the g - s equation @xcite , the only difference being that for the latter the pressure term does not only depend on the poloidal flux function @xmath0 , but also on the radial variable @xmath1 ..
Please generate the next two sentences of the article | numerical codes to solve the g - s equation have been developed since the early days of the magnetic fusion program @xcite . nevertheless , the development of optimized g - s codes remains a topic of active research , for three main reasons .
first , g - s solvers must be able to properly resolve complex two - dimensional geometries @xcite , with boundaries that may have a corner , corresponding to a magnetic field x - point @xcite . |
7,321 | Suppose that you have an abstract for a scientific paper: saturable absorption is a non - perturbative nonlinear optical phenomenon that plays a pivotal role in the generation of ultrafast light pulses .
here we show that this effect emerges in graphene at unprecedentedly low light intensities , thus opening avenues to new nonlinear physics and applications in optical technology .
specifically , we theoretically investigate saturable absorption in extended graphene by developing a non - perturbative single - particle approach , describing conduction - electron dynamics in the atomically - thin material using the two - dimensional dirac equation for massless dirac fermions , which is recast in the form of generalized bloch equations . by solving the electron dynamics non - perturbatively
, we account for both interband and intraband contributions to the intensity - dependent saturated conductivity and conclude that the former dominates regardless of the intrinsic doping state of the material .
the results are in excellent agreement with atomistic quantum - mechanical simulations including higher - band effects .
additionally , we find that the modulation depth of saturable absorption in graphene can be electrically manipulated through an externally applied gate voltage .
our results are relevant for the development of graphene - based optoelectronic devices , as well as for applications in mode - locking and random lasers . .
And you have already written the first three sentences of the full article: saturable absorption ( sa ) is an extreme nonlinear phenomenon that consists in the quenching of optical absorption under high - intensity illumination .
this effect , which is an inherent property of photonic materials , constitutes a key element for passive mode - locking ( pml ) in laser cavities @xcite , where continuous waves are broken into a train of ultrashort optical pulses .
most materials undergo saturable absorption at very high optical intensities , in close proximity to their optical damage threshold ..
Please generate the next two sentences of the article | currently , state - of - the - art semiconductor - based sa mirrors are routinely employed for pml lasers @xcite .
however , these mirrors operate in a narrow spectral range , are poorly tunable , and require advanced fabrication techniques . recently , carbon nanomaterials have emerged as an attractive , viable , and cost - effective alternative for the development of next - generation pml lasers . |
7,322 | Suppose that you have an abstract for a scientific paper: the expansion of laser - irradiated clusters or nanodroplets depends strongly on the amount of energy delivered to the electrons and can be controlled by using appropriately shaped laser pulses . in this paper ,
a self - consistent kinetic model is used to analyze the transition from quasineutral , hydrodinamic - like expansion regimes to the coulomb explosion ( ce ) regime when increasing the ratio between the thermal energy of the electrons and the electrostatic energy stored in the cluster .
it is shown that a suitable double - pump irradiation scheme can produce hybrid expansion regimes , wherein a slow hydrodynamic expansion is followed by a fast ce , leading to ion overtaking and producing multiple ion flows expanding with different velocities .
this can be exploited to obtain intracluster fusion reactions in both homonuclear deuterium clusters and heteronuclear deuterium - tritium clusters , as also proved by three - dimensional molecular - dynamics simulations . .
And you have already written the first three sentences of the full article: the interaction of ultraintense lasers with jets of molecular clusters or nanodroplets ( with typical size in the range @xmath0 nm and containing @xmath1 particles ) is a central research topic @xcite , with important applications , such as tabletop nuclear fusion for compact neutron sources @xcite , or the laboratory investigations of nucleosynthesis reactions , relevant to astrophysical scenarios @xcite .
clustered media can be regarded as sparse distributions of tiny solid targets , a peculiar configuration that allows for both a deep penetration of the laser radiation and a strong laser - matter coupling with many individual , overdense targets , thus providing extremely efficient energy absorption @xcite .
when hit by an ultraintense laser beam , the neutral atoms in a cluster are promptly ionized ( cf . ref ..
Please generate the next two sentences of the article | @xcite for a detailed analysis of the concurring ionization mechanisms in different laser / cluster configurations ) and a dense `` nanoplasma '' @xcite is formed .
the free electrons then absorb energy from the laser pulse @xcite and start expanding , causing the formation of strong electric fields , which lead to efficient ion acceleration , as first predicted by dawson @xcite . when the energy transferred to the electrons is much smaller than the electrostatic energy stored in the ion core , charge separation is localized to regions much smaller than the cluster @xcite , which then remains quasi - neutral and undergoes a hydrodynamic - like expansion @xcite ; in opposite conditions ( e.g. with small deuterium clusters exposed to extremely intense laser radiation ) the electrons suddenly escape from the cluster and the remaining bare - ion distribution undergoes a pure coulomb explosion ( ce ) @xcite . in intermediate situations , |
7,323 | Suppose that you have an abstract for a scientific paper: we present a catalog of 799 clusters of galaxies in the redshift range z@xmath0 = 0.05 - 0.3 selected from @xmath1400 deg@xmath2 of early sdss commissioning data along the celestial equator .
the catalog is based on merging two independent selection methods a color - magnitude red - sequence maxbcg technique ( b ) , and a hybrid matched - filter method ( h ) .
the bh catalog includes clusters with richness @xmath3@xmath4 40 ( matched - filter ) and @xmath5@xmath4 13 ( maxbcg ) , corresponding to typical velocity dispersion of @xmath6@xmath7 400 km s@xmath8 and mass ( within 0.6 @xmath9 mpc radius ) @xmath10 m@xmath11 .
this threshold is below abell richness class 0 clusters .
the average space density of these clusters is @xmath12 mpc@xmath13 .
all noras x - ray clusters and 53 of the 58 abell clusters in the survey region are detected in the catalog ; the 5 additional abell clusters are detected below the bh catalog cuts . the cluster richness function is determined and found to exhibit a steeply decreasing cluster abundance with increasing richness .
we derive observational scaling relations between cluster richness and observed cluster luminosity and cluster velocity dispersion ; these scaling relations provide important physical calibrations for the clusters
. the catalog can be used for studies of individual clusters , for comparisons with other sources such as x - ray clusters and agns , and , with proper correction for the relevant selection functions , also for statistical analyses of clusters . .
And you have already written the first three sentences of the full article: clusters of galaxies , the largest virialized systems known , provide one of the most powerful tools in studying the structure and evolution of the universe .
clusters highlight the large scale structure of the universe @xcite ; they trace the evolution of structure with time @xcite ; they constrain the amount and distribution of dark and baryonic matter @xcite ; they reveal important clues about the formation and evolution of galaxies @xcite ; and they place critical constraints on cosmology @xcite . in fact , clusters of galaxies place some of the most powerful constraints on cosmological parameters such as the mass density of the universe and the amplitude of mass fluctuations . in spite of their great value and their tremendous impact on understanding the universe , systematic studies of clusters of galaxies are currently limited by the lack of large area , accurate , complete , and objectively selected catalogs of optical clusters , and by the limited photometric and redshift information for those that do exist . the first comprehensive catalog of clusters of galaxies ever produced , the abell catalog of rich clusters @xcite , was a pioneering project that provided a seminal contribution to the study of extragalactic astronomy and to the field of clusters of galaxies . while galaxy clustering had been recognized before abell , the data were fragmentary and not well understood .
both abell s catalog , as well as zwicky s @xcite independent catalog , were obtained by visual inspection of the palomar observatory sky survey plates ..
Please generate the next two sentences of the article | these catalogs have served the astronomical community for nearly half a century and were the basis for many of the important advances in cluster science ( see references above ; also abell s centennial paper , @xcite ) . at the beginning of the new century , the need for a new comprehensive catalog of optical clusters one that is automated , precise , and objectively selected , with redshifts that extend beyond the [email protected] limit of the abell catalog has become apparent .
there have been recent advances in this direction , including large area catalogs selected by objective algorithms from digitized photographic plates ( @xcite for the lick catalog ; @xcite for the edcc catalog ; @xcite and @xcite for the apm catalog ) , as well as small area , deep digital surveys of distant clusters ( e.g. , the 5 deg@xmath2 palomar distant cluster survey , @xcite ; 100 deg@xmath2 red - sequence cluster survey , @xcite ; and 16 deg@xmath2 kpno deeprange survey , @xcite ) . |
7,324 | Suppose that you have an abstract for a scientific paper: we consider the problem of spatiotemporal sampling in a discrete infinite dimensional spatially invariant evolutionary process @xmath0 to recover an unknown convolution operator @xmath1 given by a filter @xmath2 and an unknown initial state @xmath3 modeled as avector in @xmath4 .
traditionally , under appropriate hypotheses , any @xmath3 can be recovered from its samples on @xmath5 and @xmath1 can be recovered by the classical techniques of deconvolution . in this paper
, we will exploit the spatiotemporal correlation and propose a new spatiotemporal sampling scheme to recover @xmath1 and @xmath3 that allows to sample the evolving states @xmath6 on a sub - lattice of @xmath5 , and thus achieve the spatiotemporal trade off .
the spatiotemporal trade off is motivated by several industrial applications @xcite .
specifically , we show that @xmath7 contains enough information to recover a typical low pass filter " @xmath8 and @xmath3 almost surely , in which we generalize the idea of the finite dimensional case in @xcite .
in particular , we provide an algorithm based on a generalized prony method for the case when both @xmath8 and @xmath3 are of finite impulse response and an upper bound of their support is known .
we also perform the perturbation analysis based on the spectral properties of the operator @xmath1 and initial state @xmath3 , and verify them by several numerical experiments .
finally , we provide several other numerical methods to stabilize the method and numerical example shows the improvement .
+ + .
And you have already written the first three sentences of the full article: in situations of practical interest , physical systems evolve in time under the action of well studied operators , one common example is provided by the diffusion processes .
sampling of such an evolving system can be done by sensors or measurement devices that are placed at various locations and can be activated at different times . in practice , increasing the spatial sampling density is usually much more expensive than increasing the temporal sampling rate ( @xcite ) .
given the different costs associated with spatial and temporal sampling , we aim to reconstruct any states in the evolutionary process using as few sensors as possible , but allow one to take samples at different time levels ..
Please generate the next two sentences of the article | besides , in some cases , obtaining samples at a sufficient rate at any single time level may not even be possible , spatiotemporal sampling may resolve this issue by oversampling in time .
a natural question is whether one can compensate for insufficient spatial sampling densities by oversampling in time . |
7,325 | Suppose that you have an abstract for a scientific paper: we examine the effect of excited neutrinos on the annihilation of relic neutrinos with ultra high energy cosmic neutrinos for the @xmath0 process .
the contribution of the excited neutrinos to the neutrino - photon decoupling temperature are calculated .
we see that photon - neutrino decoupling temperature can be significantly reduced below the obtained value of the standard model with the impact of excited neutrinos . .
And you have already written the first three sentences of the full article: according to standard cosmology , neutrinos are probably one of the most abundant particles of the universe .
the universe is filled with a sea of relic neutrinos that decoupled from the rest of the matter within the first few seconds after the big bang .
it is excessively difficult to measure relic neutrinos since the interactions of their cross sections with matter are tremendously suppressed ..
Please generate the next two sentences of the article | besides , it is crucial to detect relic neutrinos in order to test the neutrino aspects of the big bang model of cosmology but it would seem impossible with present methods . however , some indirect evidences of the relic sea may be observed . for example , weiler @xcite have shown that the uhe cosmic neutrinos may interact with relic neutrinos via the following reactions occurring on the z resonance : @xmath1 in such an event , an uhe cosmic neutrino has energy @xmath2 ev .
therefore , the interaction of relic neutrinos and uhe cosmic neutrinos would have significant cross section . |
7,326 | Suppose that you have an abstract for a scientific paper: we consider a description of the deuteron based on meson exchange potentials .
a key feature is the inclusion of the @xmath0 two - pion intermediate state ( ` @xmath1 ' ) as a significant component of the inter - nucleon potential energy . in this approach ,
deuteron binding is seen to be predominantly a consequence of @xmath1 and @xmath2 exchange , with a secondary role played by @xmath3 .
we explore sensitivity of two - nucleon binding to changes in the potential and thereby obtain an anthropic constraint that the deuteron unbinds for a modest decrease ( about @xmath4 ) in the attractive @xmath1 potential . .
And you have already written the first three sentences of the full article: imagine a sequence of worlds in which the light quark masses are continuously varied away from their physical values .
it has been argued that heavy nuclei will disassociate for a @xmath5 increase in the sum @xmath6
one can anticipate that before this happens , the deuteron will become unbound ..
Please generate the next two sentences of the article | this is because the deuteron binding energy is less than the average binding energy per nucleon . here , we study this problem quantitatively and provide details about how the deuteron would respond to variations in its potential induced by changes in @xmath6 .
the deuteron is an example of a hadronic molecule . |
7,327 | Suppose that you have an abstract for a scientific paper: quark - hadron duality in neutrino - nucleon reactions is investigated under the assumption that cross sections in the resonance region are given by the rein - sehgal model .
the quantitative analysis of the duality is done by means of appropriate integrals of the structure functions in the nachtmann variable . we conclude that with the definition of the resonance region @xmath0 gev ) the duality holds for neutrino - proton reaction @xmath1 structure function for @xmath2 gev@xmath3 and it is absent for neutrino - neutron reaction . .
And you have already written the first three sentences of the full article: the discovery of quark - hadron duality in electron - nucleon interactions @xcite rises a natural question if the same phenomenon can be seen also in neutrino - nucleon scattering .
unfortunately the available data is not yet precise enough to discuss the problem on the experimental level . at present
the only possibility is to analyze the existing theoretical models of resonance production ..
Please generate the next two sentences of the article | this approach was adopted by sato and lee @xcite who discovered that for their model of @xmath4 production the quark - hadron duality is seen : the resonance peaks of structure functions calculated at @xmath5 gev@xmath3 slide along the dis structure functions ( with cteq6 pdfs ) calculated at @xmath6 gev@xmath3 , both as functions of the nachtmann variable . in this contribution
we wish to report an investigation of the rein - sehgal ( rs ) model @xcite of resonance production . |
7,328 | Suppose that you have an abstract for a scientific paper: we investigate the possibility of testing of the einstein equivalence principle ( eep ) using measurements of anomalous magnetic moments of elementary particles .
we compute the one loop correction for the @xmath0 anomaly within the class of non metric theories of gravity described by the formalism . we find several novel mechanisms for breaking the eep whose origin is due purely to radiative corrections .
we discuss the possibilities of setting new empirical constraints on these effects . 6.0 in 8.5 in -0.25truein 0.30truein 0.30truein = 0.6 cm * the equivalence principle and anomalous magnetic moment experiments * + c. alvarez and r.b .
mann + department of physics + university of waterloo + waterloo , ont n2l 3g1 , canada + + .
And you have already written the first three sentences of the full article: metric theories of gravity offer the singular beauty of endowing spacetime with a symmetric , second - rank tensor field @xmath1 that couples universally to all non - gravitational fields .
this unique operational geometry is dependent upon the validity of the einstein equivalence principle ( eep ) , which states that the outcomes of nongravitational test experiments performed within a local , freely falling frame are independent of the frame s location ( local position invariance , lpi ) and velocity ( local lorentz invariance , lli ) in a background gravitational field .
non metric theories break this universality by coupling additional gravitational fields to matter , and so violate either lpi , lli or both ..
Please generate the next two sentences of the article | limits on lpi or lli are imposed by gravitational redshift and atomic physics experiments respectively , by comparing atomic energy transitions that are sensitive to these symmetries .
laser experiments have set stringent limits on violations of lli ( to a precision of @xmath2 ) @xcite , while the next generation of gravitational redshift experiments could reach a precision up to @xmath3 @xcite . |
7,329 | Suppose that you have an abstract for a scientific paper: warped accretion discs in active galactic nuclei ( agn ) exert a torque on the black hole that tends to align the rotation axis with the angular momentum of the outer disc .
we compute the magnitude of this torque by solving numerically for the steady state shape of the warped disc , and verify that the analytic solution of scheuer & feiler ( 1996 ) provides an excellent approximation .
we generalise these results for discs with strong warps and arbitrary surface density profiles , and calculate the timescale on which the black hole becomes aligned with the angular momentum in the outer disc . for massive black holes and accretion rates of the order of the eddington limit
the alignment timescale is always short ( @xmath0 yr ) , so that jets accelerated from the inner disc region provide a prompt tracer of the angular momentum of gas at large radii in the disc .
longer timescales are predicted for low luminosity systems , depending on the degree of anisotropy in the disc s hydrodynamic response to shear and warp , and for the final decay of modest warps at large radii in the disc that are potentially observable via vlbi .
we discuss the implications of this for the inferred accretion history of those active galactic nuclei whose jet directions appear to be stable over long timescales .
the large energy deposition rate at modest disc radii during rapid realignment episodes should make such objects transiently bright at optical and infrared wavelengths .
psfig accretion , accretion discs black hole physics
galaxies : active galaxies : jets galaxies : nuclei .
And you have already written the first three sentences of the full article: the angular momentum of gas accreting onto massive black holes in active galactic nuclei ( agn ) is likely to change with time , either as a result of mergers funneling fresh gas towards the nucleus ( hernquist & mihos 1995 ) , or because of radiation or disc wind driven warping instabilities in an existing accretion flow ( pringle 1996 , 1997 ; maloney , begelman & pringle 1996 ; maloney , begelman & nowak 1998 ) . in either case , the angular momentum of gas at large radius in the disc will be misaligned with the rotation axis of the black hole , while at small radius the combined action of viscosity and differential precession induced by the lense - thirring effect ( lense & thirring 1918 ) leads to alignment of the disc and hole angular momenta ( bardeen & petterson 1975 ; kumar & pringle 1985 ) . achieving this alignment
requires that the black hole exert a torque on the disc gas , and implies that an equal and opposite torque act on the black hole itself . over time
, this causes a change in the spin axis of the hole towards alignment with the large angular momentum reservoir provided by the disc at large radius . whether the timescale for alignment is long or short compared to the lifetime of an agn has implications for our understanding of the accretion history of these objects . if the black hole is spinning , then jets , regardless of whether they derive power from the aligned inner disc or directly from the hole itself ( blandford & znajek 1977 ; see also ghosh & abramowicz 1997 ; livio , ogilvie & pringle 1999 ) , trace the spin of the black hole ..
Please generate the next two sentences of the article | if the alignment timescale is long , then we expect that the jet direction reflects the initial spin of the black hole established during ( or prior ) to the formation of the host galaxy ( rees 1978 ) .
moreover the jet direction is expected to be stable over time , irrespective of variations in the angular momentum of accreting gas . |
7,330 | Suppose that you have an abstract for a scientific paper: we study the statistics of soft gamma repeater ( sgr ) bursts , using a data base of 187 events detected with batse and 837 events detected with rxte pca , all from sgr 1900 + 14 during its 1998 - 1999 active phase .
we find that the fluence or energy distribution of bursts is consistent with a power law of index 1.66 , over 4 orders of magnitude .
this scale - free distribution resembles the gutenberg - richter law for earthquakes , and gives evidence for self - organized criticality in sgrs .
the distribution of time intervals between successive bursts from sgr 1900 + 14 is consistent with a log - normal distribution .
there is no correlation between burst intensity and the waiting times till the next burst , but there is some evidence for a correlation between burst intensity and the time elapsed since the previous burst .
we also find a correlation between the duration and the energy of the bursts , but with significant scatter .
in all these statistical properties , sgr bursts resemble earthquakes and solar flares more closely than they resemble any known accretion - powered or nuclear - powered phenomena .
thus our analysis lends support to the hypothesis that the energy source for sgr bursts is internal to the neutron star , and plausibly magnetic . .
And you have already written the first three sentences of the full article: at least three of the four currently - known soft gamma repeaters are associated with slowly rotating , extremely magnetized neutron stars located within young supernova remnants ( kouveliotou et al .
1998 , 1999 ) .
they are characterized by the recurrent emission of gamma - ray bursts with relatively soft spectra ( resembling optically - thin thermal bremsstrahlung at @xmath040 kev ) and short durations ( @xmath1 0.1 s ) ( kouveliotou 1995 ) ..
Please generate the next two sentences of the article | thompson and duncan ( 1995 ) suggested that these bursts are due to neutron star crust fractures , driven by the stress of an evolving , ultra - strong magnetic field , @xmath2 gauss .
cheng , epstein , guyer & young ( 1996 ) observed that particular statistical properties of a sample of 111 sgr events from sgr 1806 - 20 are quite similar to those of earthquakes ( eq ) . |
7,331 | Suppose that you have an abstract for a scientific paper: two phenomenological variable @xmath0 models , viz . @xmath1 and @xmath2 have been studied under the assumption that the equation of state parameter @xmath3 is a function of time .
the selected @xmath0 models are found to be equivalent both in four and five dimensions .
the possibility of signature flip of the deceleration parameter is also shown . .
And you have already written the first three sentences of the full article: recent years have witnessed the emergence of the idea of an accelerating universe and due to some observational results @xcite , it is now established that the universe is accelerating .
this signifies a paradigm shift in cosmological research from _ expanding universe _ to _ accelerated expanding universe_. now , the problem lies in detecting an exotic type of unknown repulsive force , termed as dark energy , which is driving this acceleration .
a key factor in dark energy investigation is the equation of state parameter @xmath3 , which relates pressure and density through an equation of state of the form @xmath4 . due to lack of observational evidence in making a distinction between constant and variable @xmath3 , usually the equation of state parameter.
Please generate the next two sentences of the article | is considered as a constant @xcite with phase wise values @xmath5 , @xmath6 , @xmath7 and @xmath8 for dust , radiation , vacuum fluid and stiff fluid dominated universe respectively .
but in general , @xmath3 is a function of time or redshift @xcite . |
7,332 | Suppose that you have an abstract for a scientific paper: we report early results of an observational campaign targeted on a sample of compact steep spectrum sources selected from the first survey which are significantly weaker than those investigated before .
the selection criteria and procedure are given in detail .
we present here an assortment of merlin and vlbi observations and make some general comments based on the morphologies of the sources presented .
= 2em = 15.5 cm = 22.6 cm = -1.0 cm = 0.5 cm = 0.5 cm @xmath0 toru centre for astronomy , nicholas copernicus university , toru , poland + @xmath1 jodrell bank observatory , university of manchester , uk + * keywords : * surveys radio continuum : general quasars : general galaxies : active .
And you have already written the first three sentences of the full article: to select weak compact steep spectrum ( css ) sources from the first catalogue ( white et al .
1997 ) we took the following steps : 1 . from the source list based on green bank ( gb ) surveys at 21 and 6 cm ( white & becker 1992 ) we selected those lying within the limits of the very first release of the first survey
it covered the area ra ( j2000 ) @xmath2 , dec ( j2000 ) @xmath3 at that time having steep spectra ( @xmath4 , @xmath5 ) and being stronger than 150mjy at 6 cm ..
Please generate the next two sentences of the article | this flux density limit was chosen in order to produce a sample of a manageable size .
the above declination limits indicate that the overlap between our sample and the b3vla survey - based sample ( fanti et al . |
7,333 | Suppose that you have an abstract for a scientific paper: we report _ hubble space telescope _ near - infrared nicmos observations of a remarkable low - luminosity class i ( protostellar ) source in the taurus molecular cloud . iras 04325
+ 2402 exhibits a complex bipolar scattered light nebula .
the central continuum source is resolved and may be multiple , or may be crossed by a small dust lane .
complex arcs seen in scattered light surround the central source ; the physical nature of these structures is not clear , but they may reflect perturbations from multiple stellar sources or from time - dependent mass ejection . a second ,
resolved continuum source is found at a projected distance of approximately 1150 au from the central region , near the edge of a nebular lobe probably produced by outflow .
the images indicate that this second source is another low - luminosity young stellar object , seen nearly edge - on through a dusty disk and envelope system with disk diameter @xmath0 au .
we suggest that the scattered light `` streaks '' associated with this second source are limb - brightened outflow cavities in the dusty envelope , possibly perturbed by interaction with the outflow lobes of the main source .
the nature of the companion is uncertain , since it is observed mostly in scattered light , but is most probably a very low mass star or brown dwarf , with a minimum luminosity of @xmath1 .
our results show that protostellar sources may have multiple centers of infall and non - aligned disks and outflows , even on relatively small scales . .
And you have already written the first three sentences of the full article: understanding the manner in which protostellar envelopes collapse to stellar and disk systems is an essential problem in star formation . while progress has been made in testing the predictions of the standard theory of protostellar collapse using overall spectral energy distributions ( seds ) and source statistics of protostellar ( class i ) sources in the taurus molecular complex ( e.g. , adams , lada , & shu 1987 ; butner et al .
1991 ; kenyon , calvet , & hartmann 1993 @xmath2 kch ; kenyon et al . 1990 , 1994 ) , many details remain to be understood . in particular , the roles of outflows and non - spherical initial cloud structure in shaping protostellar clouds ( whitney & hartmann 1993 ; kenyon et al .
1993 ; calvet et al ..
Please generate the next two sentences of the article | 1994 ; hartmann et al . 1994 , 1996 ; li & shu 1996 , 1997 ) , and the way in which these effects might or might not combine with the angular momentum distribution of protostellar clouds to produce collapse to binary systems and disks ( cf .
terebey , shu , & cassen 1984 ; boss 1995 , and references therein ) , is far from clear . |
7,334 | Suppose that you have an abstract for a scientific paper: we present submillimeter array ( sma ) molecular line observations in two 2 ghz - wide bands centered at 217.5 and 227.5 ghz , toward the massive star forming region w51 north .
we identified 84 molecular line transitions from 17 species and their isotopologues .
the molecular gas distribution of these lines mainly peaks in the continuum position of w51 north , and has a small tail extending to the west , probably associated with w51 d2 .
in addition to the commonly detected nitrogen and oxygen - bearing species , we detected a large amount of transitions of the acetone ( ch@xmath0coch@xmath0 ) and methyl formate ( ch@xmath0ocho ) , which may suggest that these molecules are present in an early evolutionary stage of the massive stars .
we also found that w51 north is an ethanol - rich source .
there is no obvious difference in the molecular gas distributions between the oxygen - bearing and nitrogen - bearing molecules . under the assumption of local thermodynamic equilibrium ( lte ) , with the xclass tool , the molecular column densities , and rotation temperatures are estimated .
we found that the oxygen - bearing molecules have considerable higher column densities and fractional abundances than the nitrogen - bearing molecules .
the rotation temperatures range from 100 to 200 k , suggesting that the molecular emission could be originated from a warm environment . finally , based on the gas distributions , fractional abundances and the rotation temperatures ,
we conclude that ch@xmath0oh , c@xmath1h@xmath2oh , ch@xmath0coch@xmath0 and ch@xmath0ch@xmath1cn might be synthesized on the grain surface , while gas phase chemistry is responsible for the production of ch@xmath0och@xmath0 , ch@xmath0ocho and ch@xmath1chcn .
[ firstpage ] ism : abundances ism : individual ( w51 north ) ism : molecules radio lines : ism stars : formation .
And you have already written the first three sentences of the full article: there are three promising theoretical models to explain the formation of the massive stars : monolithic collapse , competitive accretion , and mergers of low mass stars ( see for a review , zinnecker & yorke 2007 ) .
however , their relative large distances ( a few parsecs ) , the clustered formation environments , and their short timescales have made extremely difficult to discard any of these models ( zapata et al .
2015 ) ..
Please generate the next two sentences of the article | massive stars have a substantial impact on their surrounding environments , making important contributions to the chemistry enrichment of the interstellar medium ( e. g. , hernndez - hernndez et al .
thus , searching for complex molecules in massive star formation regions is a crucial building block to understand massive star formation , since these molecules can provide information on the physical conditions and evolutionary phases of massive star formation ( herbst & van dishoeck 2009 ) . |
7,335 | Suppose that you have an abstract for a scientific paper: we present _ spitzer _ infrared observations of the starless core l429 . the ir images of
this core show an absorption feature , caused by the dense core material , at wavelengths @xmath0 70 .
the core has a steep density profile , and reaches @xmath1 mag near the center .
we show that l429 is either collapsing or in a near collapse state . .
And you have already written the first three sentences of the full article: the collapse of a dense cloud core into a star happens rapidly @xcite and therefore is rarely observed ; furthermore , most dense cores appear not to be collapsing but to be close to equilibrium ( e.g. , * ? ? ?
if they are not sufficiently supported by gas pressure and turbulence , then a plausible level of magnetic field strength would suffice to support them ( e.g. , * ? ? ?
* ; * ? ? ?.
Please generate the next two sentences of the article | * ; * ? ? ?
because the process of collapse is so rarely observed , there is considerable debate about what triggers it and how it proceeds to form a star . |
7,336 | Suppose that you have an abstract for a scientific paper: major breakthrough in quantum computation has recently been achieved using quantum annealing to develop analog quantum computers instead of gate based computers . after a short introduction to quantum computation
, we retrace very briefly the history of these developments and discuss the indian researches in this connection and provide some interesting documents ( in the figs . ) obtained from a chosen set of high impact papers ( and also some recent news etc .
blogs appearing in the internet ) .
this note is also designed to supplement an earlier note by bose ( science and culture , * 79 * , pp .
337 - 378 , 2013 ) .
3cm(5cm,-7 cm ) 0.5 cm .
And you have already written the first three sentences of the full article: 0.5 cm quantum computers are actively being sought for the last couple of decades .
basic hope being that quantum mechanics promises several features to help faster computations if quantum features are properly implemented in the hardware architecture of such computers .
traditional architecture of classical computers is logical gate - based ones ..
Please generate the next two sentences of the article | the linear superposition processing of the wave functions in quantum mechanics helps simultaneous ( probabilistic ) processing of the binary bits or qubits ( of information ) .
quantum mechanics also promises major advantages of parallel operation of these gates in appropriate architectures . |
7,337 | Suppose that you have an abstract for a scientific paper: we consider the gravitational collapse of a spherically symmetric homogeneous matter distribution consisting of a weyssenhoff fluid in the presence of a negative cosmological constant . our aim is to investigate the effects of torsion and spin averaged terms on the final outcome of the collapse . for a specific interior spacetime setup , namely the homogeneous and isotropic flrw metric ,
we obtain two classes of solutions to the field equations where depending on the relation between spin source parameters , @xmath0 the collapse procedure culminates in a spacetime singularity or @xmath1 it is replaced by a non - singular bounce .
we show that , under certain conditions , for a specific subset of the former solutions , the formation of trapped surfaces is prevented and thus the resulted singularity could be naked .
the curvature singularity that forms could be gravitationally strong in the sense of tipler .
our numerical analysis for the latter solutions shows that the collapsing dynamical process experiences four phases , so that two of which occur at the pre - bounce and the other two at post - bounce regimes .
we further observe that there can be found a minimum radius for the apparent horizon curve , such that the main outcome of which is that there exists an upper bound for the size of the collapsing body , below which no horizon forms throughout the whole scenario . .
And you have already written the first three sentences of the full article: the final state of the gravitational collapse of a massive star is one of the challenges in classical general relativity ( gr ) @xcite .
a significant contribution has been to show that , under reasonable initial conditions , the spacetime describing the collapse process would inevitably admit singularities @xcite .
these singularities , can either be hidden behind an event horizon or visible to distant observers . in the former , a black hole forms as the end product of a continual collapse process , as hypothesized by the cosmic censorship conjecture ( ccc ) @xcite ( see also @xcite for reviews on the conjecture ) ..
Please generate the next two sentences of the article | the latter are classified as naked singularities , whose existence in gr has been established under a variety of specific circumstances and for different models , with matter content of various types , e.g. scalar fields @xcite , perfect fluids @xcite , imperfect fluids @xcite and null strange quark fluids @xcite . the analysis has also been taken to wider gravitational settings , such as @xmath2 theories @xcite , lovelock gravity @xcite ( see also @xcite for some recent reviews ) and hypothesized quantum gravity theories @xcite .
this is an interesting line of research because , the possible discovery of naked singularities may provide us with an opportunity to extract information from physics beyond trans - planckian regimes @xcite , see e.g. ( @xcite for the possibility of observationally detecting naked singularities).[ff ] it is therefore well motivated to consider other realistic gravitational theories whose geometrical attributes ( not present in gr ) may affect the final asymptotic stages of the collapse . more concretely , |
7,338 | Suppose that you have an abstract for a scientific paper: a coarse - grained model for solutions of polymers in supercritical fluids is introduced and applied to the system of hexadecane and carbon dioxide as a representative example .
fitting parameters of the model to the gas - liquid critical point properties of the pure systems , and allowing for a suitably chosen parameter that describes the deviation from the lorentz - berthelot mixing rule , we model the liquid - gas and fluid - fluid unmixing transitions of this system over a wide range of temperatures and pressures in reasonable agreement with experiment .
interfaces between the polymer - rich phase and the gas can be studied both at temperatures above and below the end point of the triple line where liquid and vapor carbon dioxide and the polymer rich phase coexist . in the first case
interfacial adsorption of fluid carbon dioxide can be demonstrated .
our model can also be used to simulate quenches from the one - phase to the two - phase region . a short animation and a series of snapshots help to visualize the early stages of bubble nucleation and spinodal decomposition .
furthermore we discuss deviations from classical nucleation theory for small nuclei .
+ + pacs : 64.60.qb , 82.20.wt , 05.70.fh , 61.41.+e .
And you have already written the first three sentences of the full article: the phase behavior of polymer - solvent systems has important application in the industry for the production and processing of many kinds of plastic materials @xcite .
an example is the formation of solid polystyrene foams @xcite .
in addition , both the understanding of the equilibrium phase diagram of these systems and the kinetic mechanism of phase separation are challenging problems of statistical mechanics . on the one hand ,.
Please generate the next two sentences of the article | variation of the molecular weight of the polymer ( i.e. the `` chain length '' of the flexible linear macromolecule , n ) offers a control parameter that leaves intermolecular forces invariant , and hence allows a more stringent test of the theory than would be possible for small molecule systems . on the other hand , it is crucial to take the compressibility of the system fully into account , since for practical reasons one normally wishes to use supercritical fluids ( e.g. , co@xmath0 ) as a solvent @xcite
. then small changes of the pressure result in a large variation of the solvent density , and this fact obviously facilitates applications . while for an incompressible polymer solution ( as it is modelled , for instance , by the well - known flory - huggins lattice theory @xcite ) the early stages of phase separation can only be studied if one realizes a rapid temperature quench from a state in the one phase region into the miscibility gap ( cf . |
7,339 | Suppose that you have an abstract for a scientific paper: we have used hubble / wfc3 and the g141 grism to measure the secondary eclipse of the transiting very hot jupiter corot-2b in the 1.1 - 1.7@xmath0 m spectral region .
we find an eclipse depth averaged over this band equal to @xmath1parts per million , equivalent to a blackbody temperature of @xmath2k .
we study and characterize several wfc3 instrumental effects , especially the `` hook '' phenomenon described by @xcite .
we use data from several transiting exoplanet systems to find a quantitative relation between the amplitude of the hook and the exposure level of a given pixel . although the uncertainties in this relation are too large to allow us to develop an empirical correction for our data , our study provides a useful guide for optimizing exposure levels in future wfc3 observations .
we derive the planet s spectrum using a differential method .
the planet - to - star contrast increases to longer wavelength within the wfc3 bandpass , but without water absorption or emission to a @xmath3 limit of 85 ppm .
the slope of the wfc3 spectrum is significantly less than the slope of the best - fit blackbody .
we compare all existing eclipse data for this planet to a blackbody spectrum , and to spectra from both solar abundance and carbon - rich ( c / o=1 ) models .
a blackbody spectrum is an acceptable fit to the full dataset .
extra continuous opacity due to clouds or haze , and flattened temperature profiles , are strong candidates to produce quasi - blackbody spectra , and to account for the amplitude of the optical eclipses .
our results show ambiguous evidence for a temperature inversion in this planet . .
And you have already written the first three sentences of the full article: very hot jupiters are gas - giant exoplanets with orbital periods less than about 3 days . the close proximity of vhjs to their host stars enhances the influence of irradiation , tidal forces , and stellar activity on their structure and evolution .
corot-2b @xcite is a vhj of particular interest because of lingering questions about the structure of its atmosphere , which can be studied with observations of its secondary eclipse .
@xcite announced the first secondary eclipse observations of corot-2 in the _ corot _ optical waveband , followed by the mid - infrared _ spitzer _ secondary eclipse measurements of @xcite , re - analyzed and expanded with warm _ spitzer _ eclipses by @xcite ..
Please generate the next two sentences of the article | @xcite added a secondary eclipse point in the k@xmath4 band .
the analysis of @xcite favored a poor day - night - side heat distribution in corot-2b s atmosphere . |
7,340 | Suppose that you have an abstract for a scientific paper: in this paper we address the question : to what extent is the quantum state preparation of multiatom clusters ( before they are injected into the microwave cavity ) instrumental for determining not only the kind of machine we may operate but also the quantitative bounds of its performance ? figuratively speaking , if the multiatom cluster is the `` crude oil '' , the question is : which preparation of the cluster is the refining process that can deliver a `` gasoline '' with a `` specific octane '' ?
we classify coherences or quantum correlations among the atoms according to their ability to serve as ( i ) fuel for nonthermal machines corresponding to atomic states whose coherences displace or squeeze the cavity field , as well as cause its heating ; and ( ii ) fuel which is purely `` combustible '' , i.e. , corresponds to atomic states that only allow for heat and entropy exchange with the field and can energize a proper heat engine .
we identify highly promising multiatom states for each kind of fuel and propose viable experimental schemes for their implementation . .
And you have already written the first three sentences of the full article: the maser ( microwave amplification by stimulated emission of radiation ) was conceived based on thermodynamic considerations @xcite . in its micromaser implementation , coherent radiation is generated by inverted two - level ( rydberg ) atoms that are randomly injected into a microwave cavity one by one @xcite . for years
, the focus of micromaser studies had been on its quantum - electrodynamics features @xcite , including its extensions to the cooperative regime of multiatom clusters that are simultaneously present in the cavity @xcite , until scully et al .
@xcite revived the interest in the thermodynamics of such devices ..
Please generate the next two sentences of the article | they treated the atomic beam as a thermodynamic resource , since randomly injected atoms , which are discarded ( traced out ) after they exit the cavity , constitute an effective reservoir ( bath ) for the cavity field mode ( in the markovian approximation ) .
the surprising finding of scully et al . |
7,341 | Suppose that you have an abstract for a scientific paper: the argo - ybj experiment is almost completely installed at the yangbajing cosmic ray laboratory ( 4300 m a.s.l . ,
tibet , p.r .
china )
. the lower energy limit of the detector ( e @xmath0 1 gev ) is reached with the scaler mode , i.e. , recording the single particle rate at fixed time intervals . in this technique , due to its high altitude location and large area ( @xmath0 6700 m@xmath1 )
, this experiment is the most sensitive among all present and past ground - based detectors . in the energy range under investigation
, signals due to local ( e.g. solar gles ) and cosmological ( e.g. grbs ) phenomena are expected as significant enhancements of the counting rate over the background .
results on the search for grbs in coincidence with satellite detections are presented .
example.eps gsave newpath 20 20 moveto 20 220 lineto 220 220 lineto 220 20 lineto closepath 2 setlinewidth gsave .4 setgray fill grestore stroke grestore .
And you have already written the first three sentences of the full article: gamma ray bursts ( grbs ) have been deeply studied in the kev
mev energy range , but only little information in the gev range has been provided in the past decade by egret measurements .
only 3 bursts have been detected at energies @xmath21 gev , with one photon reaching 18 gev @xcite ..
Please generate the next two sentences of the article | the study of the high energy emission of grbs could provide extremely useful data able to constrain the emission models and the value of the ambient parameters . at these high energies
the detection from space is hampered by the very low fluxes , requiring large collection areas . from ground |
7,342 | Suppose that you have an abstract for a scientific paper: optical conductivity spectra of single crystals of the perovskite - type 3@xmath0 metallic alloy system have been studied to elucidate how the electronic behavior depends on the strength of the electron correlation without changing the nominal number of electrons .
the reflectivity measurements were made at room temperature between 0.05 ev and 40 ev .
the effective mass deduced by the analysis of the drude - like contribution to the optical conductivity and the plasma frequency do not show critical enhancement , even though the system is close to the mott transition .
besides the drude - like contribution , two anomalous features were observed in the optical conductivity spectra of the intraband transition within the 3@xmath1 band .
these features can be assigned to transitions involving the incoherent and coherent bands near the fermi level .
the large spectral weight redistribution in this system , however , does not involve a large mass enhancement . .
And you have already written the first three sentences of the full article: over the past few decades , a considerable number of studies have been performed on 3@xmath1 transition - metal oxides which have a considerably narrow 3@xmath1 band . in particular , a metal - to - insulator transition caused by a strong electron correlation@xcite ( mott transition ) as well as anomalous electronic properties in the metallic phase near the mott transition have attracted the interest of many researchers . since the discovery of the high-@xmath2 cuprate superconductors , the importance of two types of experimental approaches to the mott transition
have been discussed intensively : a filling control and a band - width control .
the former consists in doping holes or electrons to the system , and the latter in varying the strength of the electron correlation @xmath3 , where @xmath4 is the electron correlation due to coulomb repulsion and @xmath5 is the one - electron band - width . in recent years , the systematic evolutions of optical conductivity spectra in going from a correlated metallic phase to the mott - hubbard insulating phase have been reported on both the filling controlled and the band - width controlled mott - hubbard systems.@xcite the smallest energy gap for charge excitations of the mott - hubbard insulator is the excitation energy of the charge fluctuation @xmath6 , so - called a mott - hubbard gap.@xcite the optical conductivity of the mott - hubbard insulator is considered to show a gap feature due to the above charge excitation from the lower hubbard band to the upper hubbard band ..
Please generate the next two sentences of the article | v@xmath7o@xmath8 and related compounds have been extensively studied as typical materials which show the mott transition with varying the strength of the @xmath3 ratio .
the temperature dependent optical conductivity of v@xmath7o@xmath8 was reported by thomas _ |
7,343 | Suppose that you have an abstract for a scientific paper: we report on the synthesis of low doping zn@xmath0co@xmath1o ( @xmath2 ) thin films on ( 0001)-al@xmath3o@xmath4 substrates .
the films were prepared in an oxidizing atmosphere , using the pulsed laser deposition technique starting from zn and co metallic targets .
we first studied the influence of the strains of zno and their stuctural properties .
second , we have investigated the structural and the magnetic properties of the zn@xmath0co@xmath1o films .
we show that at low doping , the lattice parameters and the magnetization of the zn@xmath0co@xmath1o films depend strongly on the co concentration . .
And you have already written the first three sentences of the full article: diluted magnetic semiconductors ( dms ) of iii - v or ii - vi types have been obtained by doping semiconductors with magnetic impurities ( mn for example)@xcite .
these materials are very interesting due to their potential applications for spintronics@xcite .
however , the low curie temperature ( @xmath5 ) has limited their interest@xcite ( for example ga@xmath0mn@xmath1as , with @xmath6 has a @xmath7@xcite ) ..
Please generate the next two sentences of the article | based on the theoretical works of dietl _
et al._@xcite , several groups @xcite have studied the growth of co - doped zno films@xcite which is a good candidate having a high @xmath8 @xcite . |
7,344 | Suppose that you have an abstract for a scientific paper: in this series of papers , we develop a two - fluid model for vlbi jets .
the idea is that the jet itself is non- or mildly - relativistic ( electrons and protons ) , while the radiating blobs are relativistic electron - positron ` clouds ' moving on helical paths wrapped around the jet . in this work ,
the emphasis is on the physical description of the clouds , and not on the structure or origin of the trajectory . in the simple case where the magnetic field is uniform and homogeneous accross the cloud , and
the properties of the cloud are constant , the present paper shows synthetic maps of vlbi jets in different configurations , as well as the variation of different observational parameters along the trajectory . .
And you have already written the first three sentences of the full article: extragalactic jets at the parsec scale are present in numerous active galactic nuclei ( agn ; see a review by zensus 1995 ) .
impressive progress has been made by the very large baseline interferometry ( vlbi ) , and details still closer to the central engine are expected with the advent of millimeter vlbi .
already , a lot of information can be gained from the structure of these jets with typically 1 parsec resolution ..
Please generate the next two sentences of the article | it has been possible to detect motions within a few years in about 100 sources ( vermeulen 1995 ) , a lot of them being superluminal with apparent speeds up to @xmath0 .
the motions detected are those of blobs moving on curved trajectories . generally speaking , these paths are wiggling , reminiscent of more or less helical lines seen in projection , and apparently different from one blob to the other , and the blob velocities vary along the trajectory ( zensus 1995 ; qian et al . |
7,345 | Suppose that you have an abstract for a scientific paper: recent developments of the two mc - generators sphinx and pepsi are discussed . in sphinx
the process of polarized photo production was included to simulate the potential of a polarized hera to measure the photon structure function . in pepsi
the cc polarized cross sections on tree level have been added together with the electroweak corrections to simulate their effect on cc signals proposed for a polarized hera .
* recent developments of pepsi and sphinx * + .
And you have already written the first three sentences of the full article: the pepsi and sphinx programs are monte carlo event generators for longitudinally polarized deep inelastic lepton - nucleon scattering ( dis ) and longitudinally polarized high energy hadron - hadron collisions , respectively .
they both use probabilistic methods to generate events with unit weight .
the generation process can be split up into three parts . at first.
Please generate the next two sentences of the article | , the kinetic variables of the partonic reaction are determined according to the complete cross section yielding a two parton initial state and a two , three or four parton final state .
the partons include quarks , leptons and gauge bosons here . |
7,346 | Suppose that you have an abstract for a scientific paper: we present a microscopic calculation of the @xmath0he @xmath1-decay into the ground state of @xmath0li . to this end , we use chiral perturbation theory at next - to - next - to - next - to - leading order to describe the nuclear weak - currents . the nuclear wave functions are derived from the j - matrix inverse scattering nucleon - nucleon potential ( jisp ) , and the schrdinger equation is solved using the hyperspherical - harmonics expansion .
our calculation brings the theoretical decay - rate within @xmath2 of the measured one .
this success is attributed to the use of chiral - perturbation - theory based mesonic currents , whose contribution is qualitatively different compared to standard nuclear physics approach , where the use of meson exchange currents worsens the comparison to experiment .
the inherent inconsistency in the use of the jisp potential together with chiral - perturbation - theory based is argued not to affect this conclusion , though a more detailed investigation is called for .
we conclude that any suppression of the axial constant in nuclear matter is included in this description of the weak interaction in the nucleus . .
And you have already written the first three sentences of the full article: @xmath1-decay is the every - day reflection of weak - interaction in nuclei . as such
, it provides an experimental window to the properties of the weak interaction at nuclear density .
in particular , theoretical studies of @xmath1-decay rates of nuclei have argued for a suppression of the axial coupling constant @xmath3 , from its vacuum value , as extracted from the lifetime of the neutron @xmath4 @xcite , to unity , i.e. @xmath5 @xcite . according to a recent study , this suppression occurs gradually , as the mass of the nucleus grows , and fully utilized for @xmath6 @xcite ..
Please generate the next two sentences of the article | the ramifications of this suppression are numerous .
for example , to the understanding of astrophysical phenomena , such as neutron - star cooling and core collapse supernovae , whose dynamics is controlled by the weak interactions . |
7,347 | Suppose that you have an abstract for a scientific paper: the measurement of the beauty quark production cross section in deep inelastic scattering with the zeus detector at hera is presented . the cross section for beauty quarks , measured in the kinematic
range @xmath0 gev@xmath1 and @xmath2 , and for events with at least one muon and one jet in the breit frame , is somewhat above the next - to - leading order ( nlo ) qcd prediction , but in agreement within the experimental and theoretical uncertainties . .
And you have already written the first three sentences of the full article: deep inelastic scattering ( dis ) offers the unique opportunity to study the production mechanism of heavy quarks via the strong interaction in a particularly clean environment where a point - like projectile , a virtual photon with a virtuality @xmath3 , collides with a proton .
a first measurement of the total inclusive @xmath4-quark cross section in the dis region has been released by the h1 collaboration @xcite .
recently , the zeus collaboration has measured the production cross section of @xmath4-quarks in dis at hera , in the reaction with at least one hard jet in the breit frame , where @xmath5 is the momentum of the exchanged photon , @xmath6 is the bjorken scaling variable and @xmath7 is the proton momentum , a purely space - like photon and a proton collide head - on . ] and a muon in the final state ( @xmath8 ) @xcite ..
Please generate the next two sentences of the article | due to the large @xmath4-quark mass , muons from semi - leptonic @xmath4 decays usually have high values of @xmath9 , which is the transverse momentum of the muon with respect to the axis of the closest jet .
this allows a statistical separation of the signal from the background . |
7,348 | Suppose that you have an abstract for a scientific paper: 2ex = 3.5ex we study the fermi gas quantum mechanics associated to the abjm matrix model .
we develop the method to compute the grand partition function of the abjm theory , and compute exactly the partition function @xmath0 up to @xmath1 when the chern - simons level @xmath2 .
we find that the eigenvalue problem of this quantum mechanical system is reduced to the diagonalization of a certain hankel matrix . in reducing the number of integrations by commuting coordinates and momenta
, we find an exact relation concerning the grand partition function , which is interesting on its own right and very helpful for determining the partition function .
we also study the tba - type integral equations that allow us to compute the grand partition function numerically .
surprisingly , all of our exact results of the partition functions are written in terms of polynomials of @xmath3 with rational coefficients .
= 0.7 cm tit / hep-618 * exact results on the abjm fermi gas * .6em 1.2 cm yasuyuki hatsuda , sanefumi moriyama and kazumi okuyama 2em @xmath4 _ department of physics , tokyo institute of technology + tokyo 152 - 8551 , japan _ 1 em @xmath4 _ kobayashi maskawa institute & graduate school of mathematics , nagoya university + nagoya 464 - 8602 , japan _ 1 em @xmath4 _ department of physics , shinshu university + matsumoto 390 - 8621 , japan _ 1 em 1.5em july 2012 = 3.5ex .
And you have already written the first three sentences of the full article: m - theory is expected to unify all of our understandings on the nonperturbative effects of string theory . despite its importance , many aspects on this interesting theory await to be understood .
one of the most mysterious facts on m - theory is the degrees of freedom of the branes . from the ads / cft correspondence , it is known @xcite that @xmath5 coincident m2-branes ( or m5-branes )
have the degrees of freedom of order @xmath6 ( or @xmath7 , respectively ) . in the case of d.
Please generate the next two sentences of the article | - branes in string theory , the worldvolume theory can be described by the super yang - mills theory , which has the degrees of freedom @xmath8 .
compared with such a case , the field theoretical realization on the branes in m - theory is still unclear . |
7,349 | Suppose that you have an abstract for a scientific paper: it is well known that the poiseuille flow of a visco - elastic polymer fluid between plates or through a tube is linearly stable in the zero reynolds number limit , although the stability is weak for large weissenberg numbers . in this paper
we argue that recent experimental and theoretical work on the instability of visco - elastic fluids in taylor - couette cells and numerical work on channel flows suggest a scenario in which poiseuille flow of visco - elastic polymer fluids exhibits a _ nonlinear `` subcritical '' instability _ due to normal stress effects , with a threshold which decreases for increasing weissenberg number .
this proposal is confirmed by an explicit weakly nonlinear stability analysis for poiseuille flow of an ucm fluid .
our analysis yields explicit predictions for the critical amplitude of velocity perturbations beyond which the flow is nonlinearly unstable , and for the wavelength of the mode whose critical amplitude is smallest .
the nonlinear instability sets in quite abruptly at weissenberg numbers around 4 in the planar case and about 5.2 in the cylindrical case , so that for weissenberg numbers somewhat larger than these values perturbations of the order of a few percent in the wall shear stress suffice to make the flow unstable . we have suggested elsewhere that this nonlinear instability could be an important intrinsic route to melt fracture and that preliminary experiments are both qualitatively and quantitatively in good agreement with these predictions . .
And you have already written the first three sentences of the full article: in this paper , we reconsider the classical topic of the stability of visco - elastic poiseuille flow in the zero reynolds number limit . from a _ weakly nonlinear expansion _ , we find that this flow is nonlinearly unstable for high enough flow rates . the first linear stability analysis of the flow of a so - called oldroyd - b fluid one of the simplest continuum models for a visco - elastic polymeric fluid with nonzero normal stress differences , characterized by a single relaxation time @xmath0 @xcite was already performed almost thirty years ago @xcite . since the subsequent careful linear stability analysis of ho and denn @xcite it is generally accepted that _ poiseuille flow of an oldroyd - b fluid is linearly stable _ , even though the stability is weak for large values of the weissenberg number , the dimensionless quantity which measures the strength of polymer relaxation effects .
the definition used in this paper for the case of cylindrical coordinates relevant for pipe flow is @xmath1 where the term in the numerator is the normal stress difference of the flow . for the planar geometry the index @xmath2 has to be replaced by @xmath3 , with
the @xmath3-axis taken normal to the plates ..
Please generate the next two sentences of the article | the term in the denominator of ( [ widef ] ) is the shear stress at the wall . for an oldroyd - b or upper convected maxwell ( ucm ) fluid ,
the unperturbed flow field @xmath4 is simply parabolic , and we get @xmath5 here @xmath6 is the maximum velocity of the unperturbed profile , @xmath0 is the aforementioned relaxation time characterizing the oldroyd - b or ucm fluid , and @xmath7 is the radius of the pipe . for the planar case , r has to be replaced by @xmath8 , half the spacing between the plates . |
7,350 | Suppose that you have an abstract for a scientific paper: based on the updated urqmd transport model , the effect of the symmetry potential energy on the two - nucleon hbt correlation is investigated with the help of the coalescence program for constructing clusters , and the crab analyzing program of the two - particle hbt correlation .
an obvious non - linear dependence of the neutron - proton ( or neutron - neutron ) hbt correlation function ( @xmath0 ) at small relative momenta on the stiffness factor @xmath1 of the symmetry potential energy is found : when @xmath2 , the @xmath0 increases rapidly with increasing @xmath1 , while it starts to saturate if @xmath3 .
it is also found that both the symmetry potential energy at low densities and the conditions of constructing clusters at the late stage of the whole process influence the two - nucleon hbt correlation with the same power .
keywords : density dependence of the symmetry energy , sensitive observables , hbt correlation in recent years , the isospin dependent equation of state ( eos ) of both infinite and finite nuclear matter has been investigated in both deeper and broader range . theoretically , a large amount of probes have been brought out to be sensitively affected by the isovector part of the eos , i.e. , the symmetry energy term . based on different theories
, the symmetry energy has been parametrized in different ways ( please see @xcite for details ) . among these parametrizations ,
the @xmath4 is often used ( @xmath5 being the symmetry energy at the normal density , and @xmath6 the reduced density , while @xmath1 is the stiffness factor of the density dependence of the symmetry energy ) . especially , the density dependence of the symmetry potential energy is paid much more attention since the uncertainty of the symmetry energy mainly comes from this term .
recently , with some comparisons between the results of experimental data and dynamical model ibuu , the uncertainty in the density dependence of the symmetry energy at subnormal densities is reduced into the range of @xmath7....
And you have already written the first three sentences of the full article: we would like to thank s. pratt for providing the crab program and en - guang zhao for helpful discussions and encouragements .
we acknowledge support by the frankfurt center for scientific computing ( csc ) . the work is supported in part by the key project of the ministry of education of china under grant no .
209053 and the national natural science foundation of china under grant no ..
Please generate the next two sentences of the article | 10675046 .
chen l w , ko c m and li b a. studying stiffness of nuclear symmetry energy through isospin diffusion in heavy - ion collisions . |
7,351 | Suppose that you have an abstract for a scientific paper: lattice animals provide a discretized model for the @xmath0 transition displayed by branched polymers in solvent .
exact graph enumeration studies have given some indications that the phase diagram of such lattice animals may contain two collapsed phases as well as an extended phase .
this has not been confirmed by studies using other means .
we use the exact correspondence between the @xmath1 limit of an extended potts model and lattice animals to investigate the phase diagram of lattice animals on @xmath2 random graphs of arbitrary topology ( `` thin '' random graphs ) .
we find that only a two phase structure exists
there is no sign of a second collapsed phase .
the random graph model is solved in the thermodynamic limit by saddle point methods .
we observe that the ratio of these saddle point equations give precisely the fixed points of the recursion relations that appear in the solution of the model on the bethe lattice by henkel and seno .
this explains the equality of non - universal quantities such as the critical lines for the bethe lattice and random graph ensembles
. 22.5 cm 0.05 cm 0.2 cm 0.2 cm .
And you have already written the first three sentences of the full article: polymers , whether linear or branched , typically display a two phase structure in solvent with a @xmath0-transition @xcite , whose position depends on temperature and solvent composition , intervening between an extended and a collapsed phase .
the case of linear polymers has proved amenable to various analytical treatments such as conformal field theory and coulomb gas methods @xcite , but branched polymers have been rather more stubborn . a discretized model of branched polymers is provided by lattice animals , in essence graphs of connected sites on some lattice .
contact interactions exist between nearest neighbour sites that are not directly linked by a bond of the animal and solvent interactions exist between occupied sites and unoccupied nearest - neighbour sites ..
Please generate the next two sentences of the article | all the ingredients of the continuum polymer in solvent problem are thus present .
it is known that in @xmath3 dimensions the lattice animal exponents are related to those of the yang - lee edge singularity in @xmath4 dimensions which allows the calculation of the bulk entropic exponent for the so - called strongly embedded lattice animal @xcite . |
7,352 | Suppose that you have an abstract for a scientific paper: a mathematical model is developed to analyze the growth / decay rate of surface perturbations of an ultrathin metal film on an amorphous substrate ( @xmath0 ) .
the formulation combines the approach of mullins [ j. appl .
phys .
v30 , 77 , 1959 ] for bulk substrates , in which curvature - driven mass transport and surface deformation can occur by surface / volume diffusion and evaporation - condensation processes , with that of spencer et al .
[ phys .
rev .
lett .
v67 , 26 , 1991 ] to describe solid state transport in thin films under epitaxial strain .
modifications of mullins model to account for thin film boundary conditions result in qualitatively different dispersion relationships especially in the limit as _
@xmath1 _ where _ @xmath2 _ is the wavenumber of the perturbation and _ @xmath3 _ is the unperturbed film height .
the model is applied to study the relative rate of solid state mass transport as compared to that of liquid phase dewetting in a thin film subjected to fast a thermal pulse .
specifically , we have recently shown that multiple cycles of nanosecond ( @xmath4 ) pulsed laser melting and resolidification of ultrathin metal films on amorphous substrates can lead to the formation of various types of spatially ordered nanostructures [ phys .
rev .
b , v75 , 235439 ( 2007 ) ] .
the pattern formation has been attributed to the dewetting of the thin film by a hydrodynamic instability . in such experiments
the film is in the solid state during a substantial fraction of each thermal cycle .
however , results of a linear stability analysis based on the aforementioned model suggest that solid state mass transport has negligible effect on morphology changes of the surface .
further , a qualitative analysis of the effect of thermoelastic stress , induced by the rapid temperature changes in the film - substrate bilayer , suggests that stress relaxation does not appreciably contribute to surface deformation .
hence , surface deformation caused by liquid phase....
And you have already written the first three sentences of the full article: ion and photon beam irradiation are widely used to generate nanoscale surface features for a variety of applications : optoelectronic , plasmonic , magnetic , bio- and chemical sensing , and catalytic devices @xcite .
understanding interfacial transport mechanisms under fast thermal processing or energetic beam irradiation is essential to accurately predicting the spatio - temporal dynamics of film evolution that imparts the desired nanoscale surface features .
the contributions from various solid state transport processes that cause surface changes such as flattening or grooving in _ bulk materials _ were studied by mullins @xcite . in his formulation ,.
Please generate the next two sentences of the article | smoothening of bulk surfaces is driven by curvature effects that manifest in solid state surface diffusion , volume diffusion , or evaporation - condensation mechanisms@xcite .
mullins theory has been widely accepted and used extensively in the analyses of surface processes @xcite . however , mullins theoretical framework is inadequate to describe solid state mass transport in _ ultrathin films _ in which one has to account for the effects of other driving forces on pattern formation , e.g. dispersion forces and epitaxial stress . |
7,353 | Suppose that you have an abstract for a scientific paper: we have analyzed the broad absorption line system of the bright ( @xmath0 ) high - redshift ( @xmath1 ) qso sbs1542 + 541 using uv spectra from the hst fos along with optical data from the mmt and the steward observatory 2.3 m telescope .
these spectra offer continuous wavelength coverage from @xmath2 to @xmath3 , corresponding to @xmath4 in the qso rest frame .
the line of sight to the object contains only three identified intervening lyman - limit absorption systems .
only one of these is optically thick at the lyman edge , a low - redshift ( @xmath5 ) system with a strong lyman edge observed at @xmath6 ( @xmath7 in the rest frame ) in a hopkins ultraviolet telescope spectrum from the astro-2 mission .
the spectra therefore offer a rare opportunity to study broad absorption lines in the rest - frame extreme uv .
we find that the broad absorption line system is lacking in species of relatively low ionization often seen in broad absorption systems , such as , , and . instead , the system is dominated by very high - ionization species .
the strongest features correspond to , , and .
in addition to other high - ionization lines , we identify apparently saturated broad lyman - series lines of order ly@xmath8 and higher .
there is strong evidence for partial occultation of the qso emission source , particularly from the higher - order lyman lines which indicate a covered fraction less than @xmath9 . with the exception of and , which are low - ionization species in the context of this system ,
all of the other lines depress the flux by more than 20% .
absorption from ly@xmath10 also depresses the flux more than 20% , indicating that there are at least two different regions contributing to absorption .
overall , the data suggest a correlation between a larger covered fraction and a higher state of ionization .
these observations reveal inhomogeneity in the ionization structure of the broad absorption line gas .
we have used photoionization models to constrain the total column....
And you have already written the first three sentences of the full article: observations of sbs1542 + 541 using the international ultraviolet explorer ( porter _ et al .
_ unpublished ) show that there is significant continuum flux down to below @xmath19 , corresponding to @xmath20 in the rest frame .
this made the object a good candidate for possibly observing ly@xmath10@xmath21304 absorption in the intergalactic medium with the hopkins ultraviolet telescope ( hut ) during the astro-2 mission ..
Please generate the next two sentences of the article | observations of hs1700 + 64 ( @xmath22 ) on the same mission successfully measured the opacity ( davidsen , kriss , & zheng 1996 ) .
however , during the observations of sbs1542 + 541 on 1995 march 16 we discovered that there was a cutoff in flux slightly redshifted from the expected position of the ly@xmath10 absorption , causing us to suspect that the observed feature was a lyman limit from a low - redshift intervening absorber . to further investigate this possibility we performed observations on 1995 september 3 with the g130h , g190h , and g270h gratings of the hst fos . |
7,354 | Suppose that you have an abstract for a scientific paper: the spectral function of the closed - shell neon atom is computed by expanding the electron self - energy through a set of faddeev equations .
this method describes the coupling of single - particle degrees of freedom with correlated two - electron , two - hole , and electron - hole pairs .
the excitation spectra are obtained using the random phase approximation , rather than the tamm - dancoff framework employed in the third - order algebraic diagrammatic contruction [ adc(3 ) ] method .
the difference between these two approaches is studied , as well as the interplay between ladder and ring diagrams in the self - energy .
satisfactory results are obtained for the ionization energies as well as the energy of the ground state with the faddeev - rpa scheme that is also appropriate for the high - density electron gas . .
And you have already written the first three sentences of the full article: _ ab initio _ treatments of electronic systems become unworkable for sufficiently complex systems . on the other hand , the kohn - sham formulation @xcite of density functional theory ( dft ) @xcite incorporates many - body correlations ( beyond hartree - fock ) , while only single - particle ( sp ) equations must be solved . due to this simplicity dft
is the only feasible approach in some modern applications of electronic structure theory .
there is therefore a continuing interest both in developing new and more accurate functionals and in studying conceptual improvements and extensions to the dft framework ..
Please generate the next two sentences of the article | in particular it is found that dft can handle short - range interelectronic correlations quite well , while there is room for improvements in the description of long - range ( van der waals ) forces and dissociation processes .
microscopic theories offer some guidance in the development of extensions to dft . |
7,355 | Suppose that you have an abstract for a scientific paper: protocols for tasks such as authentication , electronic voting , and secure multiparty computation ensure desirable security properties if agents follow their prescribed programs .
however , if some agents deviate from their prescribed programs and a security property is violated , it is important to hold agents _ accountable _ by determining which deviations actually caused the violation .
motivated by these applications , we initiate a formal study of _ program actions as actual causes_. specifically , we define in an interacting program model what it means for a set of program actions to be an actual cause of a violation .
we present a sound technique for establishing program actions as actual causes .
we demonstrate the value of this formalism in two ways .
first , we prove that violations of a specific class of safety properties always have an actual cause .
thus , our definition applies to relevant security properties .
second , we provide a cause analysis of a representative protocol designed to address weaknesses in the current public key certification infrastructure .
security protocols , accountability , audit , causation .
And you have already written the first three sentences of the full article: ensuring accountability for security violations is essential in a wide range of settings .
for example , protocols for authentication and key exchange @xcite , electronic voting @xcite , auctions @xcite , and secure multiparty computation ( in the semi - honest model ) @xcite ensure desirable security properties if protocol parties follow their prescribed programs .
however , if they deviate from their prescribed programs and a security property is violated , determining which agents should be held accountable and appropriately punished is important to deter agents from committing future violations ..
Please generate the next two sentences of the article | indeed the importance of accountability in information systems has been recognized in prior work @xcite .
our thesis is that _ actual causation _ |
7,356 | Suppose that you have an abstract for a scientific paper: the electromagnetic properties of superconductors near a ferromagnetic instability are investigated by means of a generalized ginzburg - landau theory .
it is found that the magnetic flux expulsion capability of the superconductor gets stronger , in a well - defined sense , as the normal - state magnetic susceptibility increases .
the temperature dependencies of the london penetration depth , the critical fields , and the critical current are all strongly affected by ferromagnetic fluctuations .
in particular , for the critical current we find a temperature exponent @xmath0 over an appreciable temperature range .
the extent to which proximity to magnetic criticality may be a viable explanation for recent observations in mgcni microfibers , which find @xmath0 , is discussed . .
And you have already written the first three sentences of the full article: the coexistence of ferromagnetism and superconductivity has received substantial attention over the years . around 1980 ,
such states were predicted@xcite and observed,@xcite and the topic later received renewed interest in the context of experimental observations in rare earth borocarbides.@xcite more recently , interest in this subject has been revived by the observation of coexisting superconductivity and ferromagnetism in uge@xmath1@xcite and urhge,@xcite where both types of order are believed to be due to electrons in the same band .
recent theoretical attention has centered on the structure of the phase diagram,@xcite on the existence of spontaneous flux lattices,@xcite and on the question of spin - triplet versus spin - singlet superconductivity.@xcite in contrast , less is known about the properties of superconductors on the paramagnetic side of , but close to , a ferromagnetic instability ..
Please generate the next two sentences of the article | we will refer to `` paramagnetic superconductors '' to describe systems in this regime , although the superconductivity of course leads to the usual strong diamagnetic effects .
such paramagnetic superconductors include systems below the superconducting transition temperature , but above the temperature below which coexistence of superconductivity and ferromagnetism occurs , as well as systems that never develop ferromagnetism , but are close to a ferromagnetic instability in some direction in parameter space other than temperature . |
7,357 | Suppose that you have an abstract for a scientific paper: we present detailed , high spatial and spectral resolution , long - slit observations of four central cluster galaxies ( abell 0085 , 0133 , 0644 and ophiuchus ) recently obtained on the southern african large telescope ( salt ) .
our sample consists of central cluster galaxies ( ccgs ) with previously - observed h@xmath0 filaments , and have existing data from the x - ray to radio wavelength regimes available . here , we present the detailed optical data over a broad wavelength range to probe the spatially - resolved kinematics and stellar populations of the stars .
we use the pegase.hr model with the elodie v3.1 stellar library to determine the star formation histories of the galaxies using full spectrum fitting .
we perform single stellar population ( ssp ) as well as composite stellar population ( csp ) fits to account for more complex star formation histories .
monte - carlo simulations and @xmath1-maps are used to check the reliability of the solutions .
this , combined with the other multiwavelength data , will form a complete view of the different phases ( hot and cold gas and stars ) and how they interact in the processes of star formation and feedback detected in central galaxies in cooling flow clusters , as well as the influence of the host cluster .
we find small , young stellar components in at least three of the four galaxies , even though two of the three host clusters have zero spectrally - derived mass deposition rates from x - ray observations .
[ firstpage ] galaxies : formation galaxies : elliptical and lenticular , cd galaxies : clusters : individual : abell 0085 galaxies : clusters : individual : abell 0133 galaxies : clusters : individual : abell 0644 galaxies : clusters : individual : ophiuchus .
And you have already written the first three sentences of the full article: cooling flows in galaxy clusters , once thought to be on the order of 100 1000 m@xmath2 yr@xmath3 , are now understood to be depositing cool gas on the order of 1 10 m@xmath2 yr@xmath3 onto the central cluster galaxy ( hereafter abbreviated to ccg ; voigt @xmath4 fabian 2004 ) .
it is now generally accepted that some form of feedback ( agn , conduction etc . )
prevents the intracluster medium from cooling , allowing only small amounts of cool gas to accrete onto the ccg ..
Please generate the next two sentences of the article | thus , ccgs lie at the interface where it is crucial to understand the role of feedback and accretion in star formation . within these cooling - flow ccgs , cool
molecular clouds , warm ionized hydrogen , and the cooling intracluster medium are related . a complete view of the star formation process incorporates the stars with the gas and an understanding of the processes by which these phases interact , and therefore , requires information from several wavelength regimes . various previous studies have reported several examples of ongoing star formation in ccgs , in particular those hosted by cooling - flow clusters ( cardiel , gorgas @xmath4 aragn - salamanca 1998 ; crawford et al . 1999 ; mcnamara et al . |
7,358 | Suppose that you have an abstract for a scientific paper: connected radio interferometers are sometimes used in the tied - array mode : signals from antenna elements are coherently added and the sum signal applied to a vlbi backend or pulsar processing machine . usually there is no computer - controlled amplitude weighting in the existing radio interferometer facilities . radio frequency interference ( rfi ) mitigation with phase - only adaptive beamforming
is proposed for this mode of observation .
small phase perturbations are introduced in each of the antenna s signal .
the values of these perturbations are optimized in such a way that the signal from a radio source of interest is preserved and rfi signals suppressed .
an evolutionary programming algorithm is used for this task .
computer simulations , made for both one - dimensional and two - dimensional array set - ups , show considerable suppression of rfi and acceptable changes to the main array beam in the radio source direction .
* rfi mitigation with phase - only adaptive beamforming * + p. a. fridman + astron , dwingeloo , p.o .
box 2 , 7990 aa the netherlands + e - mail : [email protected] .
And you have already written the first three sentences of the full article: suppression of radio frequency interference ( rfi ) with adaptive beamforming is widely used in radio astronomy , radar and telecommunications . the main idea behind many algorithms proposed for use in radio astronomy consists of weighting the outputs of array elements in such a way as to create zero values in the synthesized array pattern in the direction of rfi and to keep the signal of interest ( soi ) , the radio source to be observed , in the maximum of the main lobe without significant loss of gain @xcite . during recent years
there has been a growing interest in radio astronomy for applying these methods of rfi mitigation both to existing radio telescopes and to future generation projects .
there are several specific features of the large connected radio interferometers ( ri ) used in radio astronomy such as westerbork synthesis radio telescope ( wsrt ) , very large array ( vla ) and giant metrewave radio telescope ( gmrt ) which make the straightforward application of this adaptive beam - forming different and difficult when compared to classic phased arrays : \1 ..
Please generate the next two sentences of the article | connected ri are highly sparse arrays .
their main mode of operation is correlation processing . |
7,359 | Suppose that you have an abstract for a scientific paper: we present 3d hydrodynamical simulations of an isotropic fast wind interacting with a previously ejected toroidally - shaped slow wind in order to model both the observed morphology and the kinematics of the planetary nebula ( pn ) .
this source , also known as the butterfly nebula , presents one of the most complex morphologies ever observed in pne . from our numerical simulations , we have obtained an intensity map for the h@xmath0 emission to make a comparison with the _ hubble space telescope _ ( _ hst _ ) observations of this object .
we have also carried out a proper motion ( pm ) study from our numerical results , in order to compare with previous observational studies .
we have found that the two interacting stellar wind model reproduces well the morphology of , and while the pm in the models are similar to the observations , our results suggest that an acceleration mechanism is needed to explain the hubble - type expansion found in _ hst _ observations .
[ firstpage ] methods : numerical planetary nebulae : general planetary nebulae : individual : ngc 6302 .
And you have already written the first three sentences of the full article: planetary nebulae ( pne ) form around stars of low and intermediate mass ( @xmath1 m@xmath2 ) towards the end of their evolution .
the nebula originates from the interaction between a fairly dense ( @xmath310@xmath4 m@xmath2 yr@xmath5 ) ` slow wind ' ( @xmath310 km s@xmath5 ) lost by the star as a red giant on the asymptotic giant branch ( agb ) with a tenuous ( @xmath310@xmath6 m@xmath2 yr@xmath5 ) ` fast wind ' ( @xmath31000 km s@xmath5 ) that follows after the agb phase .
the nebula material becomes ionized once the effective temperature of the central star , which evolves into a white dwarf , exceeds 25000 k ( for a review see @xcite ) ..
Please generate the next two sentences of the article | ngc 6302 ( pn [email protected] ) is a bipolar pn .
its complex and clumpy morphology shown in h@xmath0 and [ nii ] _ hubble space telescope _ |
7,360 | Suppose that you have an abstract for a scientific paper: we calculate low - energy proton
deuteron scattering in the framework of pionless effective field theory . in the quartet channel , we calculate the elastic scattering phase shift up to next - to - next - to - leading order in the power counting . in the doublet channel , we perform a next - to - leading order calculation .
we obtain good agreement with the available phase shift analyses down to the scattering threshold .
the phase shifts in the region of non - perturbative coulomb interactions are calculated by using an optimised integration mesh . moreover ,
the coulomb contribution to the @xmath0he@xmath0h binding energy difference is evaluated in first order perturbation theory .
we comment on the implications of our results for the power counting of subleading three - body forces . .
And you have already written the first three sentences of the full article: although quantum chromodynamics ( qcd ) is widely accepted as the underlying theory of strong interactions , _ ab initio _ calculations of nuclear properties in lattice qcd remain a large theoretical challenge @xcite . in nuclear physics ,
the relevant degrees of freedom are pions and nucleons , and much of the computational effort in such a calculation would be required for generating the correct degrees of freedom from quarks and gluons rather than their interactions .
traditionally , nucleon nucleon interactions are described via phenomenological nuclear forces fitted to scattering data ..
Please generate the next two sentences of the article | effective field theory ( eft ) provides a powerful method to construct nuclear forces with a direct connection to qcd in a systematic , model - independent way @xcite . for very low energies and momenta @xmath1 , the non - analyticities from pion exchange
can not be resolved and one can hence use an eft including only short - range contact interactions between nucleons @xcite . this theory is constructed to reproduce the effective range expansion @xcite in the two - body system and recovers efimov s universal approach to the three - nucleon problem @xcite . |
7,361 | Suppose that you have an abstract for a scientific paper: milimeter wave ( mmwave ) band mobile communications can be a solution to the continuously increasing traffic demand in modern wireless systems .
even though mmwave bands are scarcely occupied , the design of a prospect transceiver should guarantee the efficient coexistence with the incumbent services in these bands . to that end , in this paper , two underlay cognitive transceiver designs are proposed that enable the mmwave spectrum access while controlling the interference to the incumbent users .
mmwave systems usually require large antenna arrays to achieve satisfactory performance and thus , they can not support fully digital transceiver designs due to high demands in hardware complexity and power consumption .
thus , in order to develop efficient solutions , the proposed approaches are based on a hybrid analog - digital pre - coding architecture . in such hybrid designs
, the overall beamformer can be factorized in a low dimensional digital counterpart applied in the baseband and in an analog one applied in the rf domain .
the first cognitive solution developed in this paper designs the cognitive hybrid pre - coder by maximizing the mutual information between its two ends subject to interference , power and hardware constraints related to the analog counterpart .
the second solution aims at reduced complexity requirements and thus derives the hybrid pre - coder by minimizing the frobenious norm of its difference to the optimal digital only one . a novel solution for the post - coder at the cognitive receiver part
is further proposed here based on a hardware constrained minimum mean square error criterion .
simulations show that the performance of both the proposed hybrid approaches is very close to the one of the fully digital solution for typical wireless environments .
submitted on the ieee transactions on signal processing millimeter wave ( mmwave ) , cognitive radio , multiple - input multiple - output ( mimo ) , large - scale antenna arrays , hybrid pre - coding ,....
And you have already written the first three sentences of the full article: exponentially increasing demand for data rates as well as the spectrum congestion in the lower parts of the electromagnetic spectrum forces the wireless communications industry to explore systems adapted to frequencies within the so - called mmwave band @xcite .
mobile operators are investigating the possibility of using mmwave frequencies for future generation of mobile communications , while migrating the backhaul networks to beyond 30 ghz @xcite .
satellite industry has already established its presence in higher frequency bands by using the @xmath0 ghz band for feeder links as well as fixed - satellite - service ( fss ) user terminals in the downlink , and @xmath1 ghz band for the user terminal uplinks @xcite ..
Please generate the next two sentences of the article | such a migration to tens of ghz bands provides the wireless industry with a much higher bandwidths , and thus enables them to deploy multiple gbps services . however , the development of communications systems in the mmwave bands is a challenging task .
mmwave signals suffer from severe propagation loss , penetration loss and rain fading compared to signals in lower frequencies @xcite . |
7,362 | Suppose that you have an abstract for a scientific paper: the thresholding covariance estimator has nice asymptotic properties for estimating sparse large covariance matrices , but it often has negative eigenvalues when used in real data analysis . to simultaneously achieve sparsity and positive definiteness , we develop a positive definite @xmath0-penalized covariance estimator for estimating sparse large covariance matrices . an efficient alternating direction method is derived to solve the challenging optimization problem and its convergence properties are established . under weak regularity conditions ,
non - asymptotic statistical theory is also established for the proposed estimator .
the competitive finite - sample performance of our proposal is demonstrated by both simulation and real applications .
= 1 * keywords * : alternating direction methods ; large covariance matrices ; matrix norm ; positive - definite estimation ; sparsity ; soft - thresholding . .
And you have already written the first three sentences of the full article: estimating covariance matrices is of fundamental importance for an abundance of statistical methodologies . nowadays
, the advance of new technologies has brought massive high - dimensional data into various research fields , such as fmri imaging , web mining , bioinformatics , climate studies and risk management , and so on .
the usual sample covariance matrix is optimal in the classical setting with large samples and fixed low dimensions @xcite , but it performs very poorly in the high - dimensional setting @xcite . in the recent literature ,.
Please generate the next two sentences of the article | regularization techniques have been used to improve the sample covariance matrix estimator , including banding @xcite , tapering @xcite and thresholding @xcite . banding or tapering is very useful when the variables have a natural ordering and off - diagonal entries of the target covariance matrix decays to zero as they move away from the diagonal . on the other hand ,
thresholding is proposed for estimating permutation - invariant covariance matrices . |
7,363 | Suppose that you have an abstract for a scientific paper: we show that grains can be efficiently aligned by interacting with a subsonic gaseous flow .
the alignment arises from grains having irregularities that scatter atoms with different efficiency in the right and left directions .
the grains tend to align with long axes perpendicular to magnetic field , which corresponds to davis - greenstein predictions .
choosing conservative estimates , scattering efficiency of impinging atoms and conservative `` degree of helicity '' , the alignment of helical grains is much more efficient than the gold - type alignment processes . .
And you have already written the first three sentences of the full article: one of the most convenient ways to trace magnetic field is related to emission and absorption of polarized radiation by aligned dust .
therefore aligned dust is widely used for this purpose both in diffuse interstellar medium and molecular gas .
moreover , there is evidence of aligned dust around young stellar objects and evolved stars as well as astrophysical environments . at the same time , the processes that aligned dust and their relation to magnetic field are still the subject of debates and require further studies ( see lazarian 2007 for a review ) . while radiative torques ( dolginov & mytrophanov 1976 , draine & weingartner 1996 , 1997 , weingartner & draine 2003 , cho & lazarian 2005 , lazarian & hoang 2007 , hoang & lazarian 2007 ) are currently seen as the most promising candidate mechanism , the variety of astrophysical conditions may enables other mechanisms to dominate in particular environments ..
Please generate the next two sentences of the article | mechanical alignment was pioneered by gold ( 1951 , 1952 ) and then quantified and elaborated by other researchers ( e.g. purcell 1969 , purcell & spitzer 1971 , dolginov & mytrophanov 1976 , lazarian 1994 , 1997 , roberge et al .
while the original mechanism could deal with thermally rotating grains only , two modifications of the mechanism introduced in lazarian ( 1995 ) and elaborated later in lazarian & efroimsky ( 1996 ) , lazarian , efroimsky & ozik ( 1997 ) , efroimsky ( 1999 ) enabled the alignment of grains rotating at much higher rates . |
7,364 | Suppose that you have an abstract for a scientific paper: based on an exteded grid of nlte , line blanketed model atmospheres with stellar winds as calculated by means of fastwind , we have investigated the change in the strengths of strategic helium transitions in the optical as caused by a 0.3 decrease in metallicity with respect to solar abundances .
our calculations predict that only part of the observed increase in of o - type dwarfs could be explained by metallicity effects on the spectral type indicators , while the rest must be attributed to other reasons ( e.g. , different stellar structures as a function of metallicity or differences between observed and theoretical wind parameters etc . ) .
in addition , we found that using the he ii 4686 line to classify stars in low metallicity environments ( @xmath0 0.3 ) might artificially increase the number of low luminosity ( dwarfs and giants ) o - stars , on the expense of the number of o - supergiants . .
And you have already written the first three sentences of the full article: thanks to the outstanding work by n. walborn and collaborators over the last 30 years , a detailed classification scheme for ob - stars of solar metallicity has been developed , based on the morphology of the line spectrum .
for the specific case of o - type stars , an alternative scheme relying on quantitative criteria has been provided by conti & alschuler @xcite and mathys @xcite as well .
consequently , the classification of galactic ob stars is rigorously defined ..
Please generate the next two sentences of the article | the classification of extragalactic stars , on the other hand , is still somewhat problematic . in particular
, the calibration between spectral types and physical parameters differs as a function of metallicity when criteria for milky way stars are applied . with respect to b - stars , |
7,365 | Suppose that you have an abstract for a scientific paper: we present an analytic formulation for the equilibrium gas density profile of early - type galaxies that explicitly includes the contribution of stars in the gravitational potential .
we build a realistic model for an isolated elliptical galaxy and explore the equilibrium gas configurations as a function of multiple parameters . for an assumed central gas temperature @xmath0 kev
, we find that neglecting the gravitational effects of stars , which can contribute substantially in the innermost regions , leads to an underestimate of the enclosed baryonic gas mass by up to @xmath165% at the effective radius , and by up to @xmath115% at the nfw scale radius , depending on the stellar baryon fraction .
this formula is therefore important for estimating the baryon fraction in an unbiased fashion .
these new hydrostatic equilibrium solutions , derived for the isothermal and polytropic cases , can also be used to generate more realistic initial conditions for simulations of elliptical galaxies . moreover ,
the new formulation is relevant when interpreting x - ray data .
we compare our composite isothermal model to the standard @xmath2-model used to fit x - ray observations of early - type galaxies , to determine the value of the nfw scale radius @xmath3 . assuming a 10% stellar baryon fraction , we find that the exclusion of stars from the gravitational potential leads to ( i ) an underestimate of @xmath3 by @xmath180% , and to ( ii ) an overestimate of the enclosed dark matter at @xmath3 by a factor of @xmath12 , compared to the equivalent @xmath2-model fit results when stars are not taken into account . for higher stellar mass fractions ,
a @xmath2-model is unable to accurately reproduce our solution , indicating that when the observed surface brightness profile of an isolated elliptical galaxy is found to be well fitted by a @xmath2-model , the stellar mass fraction can not be much greater than @xmath110% .
dark matter galaxies : elliptical and lenticular , cd galaxies : ism galaxies :....
And you have already written the first three sentences of the full article: several studies , both observational and computational , of groups and clusters of galaxies , and of individual early - type galaxies , assume that the hot gas present in these systems is in hydrostatic equilibrium ( he ) in the overall gravitational potential .
even though the assumption of he has been shown to not always be robust ( e.g. bertin et al . 1993 ; ciotti & pellegrini 2004 ) , many authors assume an isothermal @xmath2-model ( cavaliere & fusco - femiano 1976 , 1978 ) to describe the gas profile , but several solve the he equation , assuming that the gravitational potential is due to dark matter ( dm ) only , usually described by an nfw ( navarro , frenk & white 1996 ) profile ( e.g. makino , sasaki & suto 1998 ; suto , sasaki & makino 1998 ) , or by more general profiles ( e.g. ciotti & pellegrini 2008 ) .
while this approximation seems to hold for groups and clusters of galaxies , it is well known that stars contribute a significant fraction of the total and baryonic matter of elliptical galaxies , and even become the dominant part at the very centre of these systems ( e.g. ferreras , saha & williams 2005 ) ..
Please generate the next two sentences of the article | the purpose of this paper is to extend previous calculations that only considered the potential due to dm , and explicitly include the contribution of the stellar component as well .
providing an analytic fitting formula for calculating the response of the gas to the presence of the gravitational potential induced by both dm and stars is useful while interpreting x - ray data of early - type galaxies and for setting up initial conditions for simulations of elliptical galaxies . |
7,366 | Suppose that you have an abstract for a scientific paper: we have previously presented 5.7@xmath0 evidence for a smaller @xmath1 at redshifts @xmath2 from a sample of 128 keck / hires quasar absorption systems : @xmath3 .
a non - zero @xmath4 manifests itself as a distinct pattern of shifts in the measured absorption line wavelengths .
the statistical error is now small : we do detect small line shifts in the hires data .
whether these shifts are due to systematic errors or due to real variation in @xmath1 is now the central question .
here we summarize the two potentially most important systematic effects : atmospheric dispersion and isotopic abundance evolution .
previously , these have been difficult to quantify / model but here we find that neither of them can explain our results .
furthermore , the hires spectra themselves contain no evidence for these effects .
independent measurements of @xmath4 with a different telescope and spectrograph are now crucial if we are to rule out or confirm the present evidence for a variable @xmath1 . .
And you have already written the first three sentences of the full article: in @xcite and @xcite we presented new evidence for a smaller fine structure constant , @xmath5 , in high redshift quasar absorption clouds : @xmath6 .
this preliminary result is the weighted mean from a many - multiplet ( mm ) analysis of 128 absorption systems and represents a significant improvement on our previously published result from 49 systems @xcite : @xmath7 .
such a potentially fundamental result requires extreme scrutiny , including a thorough consideration of possible systematic errors . in @xcite.
Please generate the next two sentences of the article | we explored a wide range of possibilities : laboratory wavelength errors , wavelength calibration errors , atmospheric dispersion effects , unidentified interloping transitions , isotopic ratio and/or hyperfine structure effects , intrinsic instrumental profile variations , spectrograph temperature variations , heliocentric velocity corrections , kinematic effects and large scale magnetic fields .
all but two of these atmospheric dispersion effects and isotopic abundance variation were shown to be negligible . here |
7,367 | Suppose that you have an abstract for a scientific paper: image rotation , polarisation , rotating dielectric , specific rotary power when light is passing through a rotating medium the optical polarisation is rotated .
recently it has been reasoned that this rotation applies also to the transmitted image ( padgett _ et al .
_ 2006 ) .
we examine these two phenomena by extending an analysis of player ( 1976 ) to general electromagnetic fields .
we find that in this more general case the wave equation inside the rotating medium has to be amended by a term which is connected to the orbital angular momentum of the light .
we show that optical spin and orbital angular momentum account respectively for the rotation of the polarisation and the rotation of the transmitted image .
[ firstpage ] .
And you have already written the first three sentences of the full article: jones ( 1976 ) studied the propagation of light in a moving dielectric and showed by experiment that a rotating medium induces a rotation of the polarisation of the transmitted light . player ( 1976 ) confirmed that this observation could be accounted for through an application of maxwells equations in a moving medium . more recently
padgett _ et al . _
( 2006 ) reasoned that the rotation of the medium turns a transmitted image by the same angle as the polarisation ..
Please generate the next two sentences of the article | this is in contrast to the faraday effect ( faraday 1846 ) , where a static magnetic field in a dielectric medium , parallel to the propagation of light , causes a rotation of the polarisation but not a rotation of a transmitted image .
rotation of the plane of polarisation and image rotation in a rotating medium may be attributed respectively to the spin and orbital angular momentum of light ( allen _ et al . |
7,368 | Suppose that you have an abstract for a scientific paper: we report on monitoring observations of the tev @xmath0-ray binary , which were carried out to constrain the interaction between the be circumstellar disk and the compact object of unknown nature , and provide for the first time high - dispersion ( r@xmath1 ) optical spectra in the second half of the orbital cycle , from apastron through periastron .
the h@xmath2 , h@xmath3 , and h@xmath0 line profiles are found to exhibit remarkable short - term variability for @xmath41 month after the apastron ( phase 0.60.7 ) , whereas they show little variation near the periastron .
these emission lines show `` s - shaped '' variations with timescale of @xmath4150 days , which is about twice that reported previously .
in contrast to the balmer lines , no profile variability is seen in any emission line .
we estimate the radii of emitting regions of the h@xmath2 , h@xmath3 , h@xmath0 , and emission lines to be @xmath430 , 11 , 7 , and 2 stellar radii ( @xmath5 ) , respectively .
the amplitudes of the line profile variations in different lines indicate that the interaction with the compact object affects the be disk down to , at least , the radius of 7 @xmath5 after the apastron .
this fact , together with little profile variability near the periastron , rules out the tidal force as the major cause of disk variability . although this leaves the pulsar wind as the most likely candidate mechanism for disk variations , understanding the details of the interaction , particularly the mechanism for causing a large - scale disk disturbance after the apastron , remains an open question . .
And you have already written the first three sentences of the full article: tev @xmath0-ray binaries are a subclass of binaries with a compact object , established in the 2000 s ( e.g. , * ? ? ?
* for a recent review ) .
these systems have a spectral energy distribution with a peak beyond 1 mev and are variable at multi - wavelengths up to tev energies ..
Please generate the next two sentences of the article | there are 5 known binaries of this kind , all of which have either an o - type main - sequence star or a be star with a circumstellar disk as the optical counterpart .
the nature of the compact object is unknown in all systems but one ( ) . for such systems two competing scenarios have been proposed , based on the different nature of the compact object , and hence the different mechanism of high energy emissions . |
7,369 | Suppose that you have an abstract for a scientific paper: we study the angular power spectra of polarized galactic synchrotron in the range @xmath0 , at several frequencies between 0.4 and 2.7 ghz and at several galactic latitudes up to near the north galactic pole . electric- and
magnetic - parity polarization spectra are found to have slopes around @xmath1 in the parkes and effelsberg galactic - plane surveys , but strong local fluctuations of @xmath2 are found at @xmath3 from the 1.4 ghz effelsberg survey .
the @xmath4 spectrum , which is insensitive to the polarization direction , is somewhat steeper , being @xmath5 for the same surveys .
the low - resolution multifrequency survey of brouw and spoelstra ( 1976 ) shows some flattening of the spectra below 1 ghz , more intense for @xmath6 than for @xmath4 . in no case
we find evidence for really steep spectra .
the extrapolation to the cosmological window shows that at 90 ghz the detection of e - mode harmonics in the cosmic background radiation should not be disturbed by synchrotron , even around @xmath7 for a reionization optical depth @xmath8 . , , , , , , background radiations radio continuum : general methods : statistical pacs : 98.70-f , 98.70.vc .
And you have already written the first three sentences of the full article: angular power spectra ( henceforth , aps ) of the galactic synchrotron polarized radiation are raising up an increasing attention in these years .
the first study , based on the parkes 2.4 ghz survey ( duncan et al . 1997 , hereafter d97 ) , was due to tucci et al .
( 2000 ) , and other papers appeared shortly after ( baccigalupi et al ..
Please generate the next two sentences of the article | , 2001a ; giardino et al .
the main motivation for these works was the need for an angular - scale dependent separation of the cosmic microwave background ( cmb ) signal from the polarized radio foreground ; in fact the first work on the aps of a polarized galactic foreground ( prunet et al . |
7,370 | Suppose that you have an abstract for a scientific paper: we report two sympathetic solar eruptions , including a partial and a full flux rope eruption in a quadrupolar magnetic region , where a large and a small filament resided above the middle and the east neutral lines respectively .
the large filament first rose slowly at a speed of 8 km s@xmath0 for 23 minutes and then it was accelerated to 102 km s@xmath0 . finally , this filament erupted successfully and caused a coronal mass ejection . during the slow rising phase , various evidence for
breakout - like external reconnection has been identified at high and low temperature lines .
the eruption of the small filament started around the end of the large filament s slow rising .
this filament erupted partially and no associating coronal mass ejection could be detected .
based on a potential field extrapolation , we find that the topology of the three - dimensional coronal field above the source region is composed of three low - lying lobes and a large overlying flux system , and a null point located between the middle lobe and the overlying antiparallel flux system .
we propose a possible mechanism within the framework of the magnetic breakout model to interpret the sympathetic filament eruptions , in which the magnetic implosion mechanism is thought to be a possible linkage between the sympathetic eruptions , and the external reconnection at the null point transfers field lines from the middle lobe to the lateral lobes and thereby leads to the full ( partial ) eruption of the observed large ( small ) filament .
other possible mechanisms are also discussed briefly .
we conclude that the structural properties of coronal fields are important for producing sympathetic eruptions . .
And you have already written the first three sentences of the full article: the filament eruption is one of the most spectacular phenomena on the sun .
previous studies have shown that filament eruptions are closely associated with magnetic flux cancellation and emergence on the photosphere @xcite , flares , and coronal mass ejections ( cmes ) , which are large - scale expulsions of mass and magnetic field from the sun into the heliosphere ( for a review , see * ? ? ?
it has been widely accepted that the filament eruption , flare , and cme are three different manifestations of a single physical process originating from the coronal magnetic field , but the relationships among them are not well understood @xcite ..
Please generate the next two sentences of the article | generally speaking , the eruption of a filament always starts from a closed magnetic system in quasi - static equilibrium , in which the upward magnetic pressure force of the low - lying sheared field is balanced by the downward tension force of the overlying field . when the eruption begins , the equilibrium is destroyed catastrophically , and part of the nonpotential magnetic flux and the plasma contained within it are expelled from the sun violently . however ,
when and how the eruption takes place is still not well understood , even though extensive observational and theoretical studies have been made in the past several decades . from the space weather point of view |
7,371 | Suppose that you have an abstract for a scientific paper: we study fluctuations of the number of bose condensed atoms in weakly interacting homogeneous and trapped gases . for a homogeneous system
we apply the particle - number - conserving formulation of the bogoliubov theory and calculate the condensate fluctuations within the canonical and the microcanonical ensembles .
we demonstrate that , at least in the low - temperature regime , predictions of the particle - number - conserving and traditional , nonconserving theory are identical , and lead to the anomalous scaling of fluctuations .
furthermore , the microcanonical fluctuations differ from the canonical ones by a quantity which scales normally in the number of particles , thus predictions of both ensembles are equivalent in the thermodynamic limit .
we observe a similar behavior for a weakly interacting gas in a harmonic trap .
this is in contrast to the trapped , ideal gas , where microcanonical and canonical fluctuations are different in the thermodynamic limit . .
And you have already written the first three sentences of the full article: experimental realization of atomic bose - einstein condensation and degenerated fermi gases , has stimulated a large interest in the physics of ultracold gases @xcite . among others ,
the issue of fluctuations in the number of condensed atoms has been a subject of intensive theoretical studies @xcite-@xcite .
it is well - known that the standard textbook approach based on the grand - canonical ensemble predicts unphysically large fluctuations ..
Please generate the next two sentences of the article | this pathological behavior is avoided , however , when one employs the canonical or the microcanonical ensemble , where the total number of particles is fixed . from the experimental point of view ,
trapped atoms are under conditions of almost complete isolation . |
7,372 | Suppose that you have an abstract for a scientific paper: the evolution of gauge invariant second - order scalar perturbations in a general single field inflationary scenario are presented .
different second order gauge invariant expressions for the curvature are considered .
we evaluate _
perturbatively _ one of these second order curvature fluctuations and a second order gauge invariant scalar field fluctuation during the slow - roll stage of a massive chaotic inflationary scenario , taking into account the deviation from a pure de sitter evolution and considering only the contribution of super - hubble perturbations in mode - mode coupling .
the spectra resulting from their contribution to the second order quantum correlation function are nearly scale - invariant , with additional logarithmic corrections with respect to the first order spectrum .
for all scales of interest the amplitude of these spectra depends on the total number of e - folds .
we find , on comparing first and second order perturbation results , an upper limit to the total number of e - folds beyond which the two orders are comparable . .
And you have already written the first three sentences of the full article: one of the observational arguments supporting inflation is the evidence of nearly scale - invariant primordial adiabatic fluctuations with a mostly gaussian spectrum , as shown by cobe @xcite and wmap @xcite . in its simplest realizations , adiabatic cosmological fluctuations
are simply related to linear fluctuations of the inflaton generated during the accelerated stage : such fluctuations have a gaussian spectrum . non - linear fluctuations inevitably carry a @xmath0-squared distribution , which may contribute to non - gaussianities in the 3-d power spectrum and in cmb anisotropies depending on the amplitude and spectrum of these non - linearities ( see @xcite for a review ) .
a study of fluctuations beyond the linear level is therefore interesting not only for the issue of the stability of inflationary dynamics , but also because of its connection with the predictions of non - gaussianities in the matter power spectrum and in cmb anisotropies . even in absence of non - linearity in the potential for the scalar field ,.
Please generate the next two sentences of the article | the generality of intrinsic non - gaussianities is guaranteed by the non - linearity of the einstein equations , a fact which has motivated a great interest both from the theoretical and observational point of view @xcite .
our choice of calculating the intrinsic non - gaussianities for a free massive inflationary model is therefore a case of primary interest , since in such a case the whole non - linear sector is given by gravity . |
7,373 | Suppose that you have an abstract for a scientific paper: magnetization and @xmath0cu nmr - nqr relaxation measurements are used to study the superconducting fluctuations in yba@xmath1cu@xmath2o@xmath3 ( ybco ) oriented powders . in optimally doped ybco
the fluctuating negative magnetization @xmath4 is rather well described by an anisotropic ginzburg - landau ( gl ) functional and the curves @xmath5 cross at @xmath6 . in underdoped ybco , instead , over a wide temperature range an anomalous diamagnetism is observed , stronger than in the optimally doped compound by about an order of magnitude .
the field and temperature dependences of @xmath7 can not be described either by an anisotropic gl functional or on the basis of scaling arguments .
the anomalous diamagnetism is more pronounced in samples with a defined order in the cu(1)o chains .
the @xmath0cu(2 ) relaxation rate shows little , if any , field dependence in the vicinity of the transition temperature @xmath8 .
it is argued how the results in the underdoped compounds can be accounted for by the presence of charge inhomogeneities , favoured by chains ordering . .
And you have already written the first three sentences of the full article: the superconducting transition in conventional superconductors is rather well described by mean field theories , essentially because in the coherence volume @xmath9 a large number of pairs is present . on the contrary , in cuprate superconductors the small coherence length @xmath10 , the reduced carrier density , the marked anisotropy and the high transition temperature @xmath6
strongly enhance the superconducting fluctuations ( sf ) . in a wide temperature range , which can extend up to @xmath11 or @xmath12 k above @xmath6
, a variety of phenomena related to sf @xcite can be detected by several experiments such as specific heat @xcite , thermal expansion @xcite , penetration depth @xcite , conductivity @xcite and magnetization @xcite measurements ..
Please generate the next two sentences of the article | also nmr - nqr relaxation has been used to detect sf @xcite .
recently the field dependence of the nmr relaxation rate @xmath13 and of the knight shift have been studied , by varying the magnetic field from @xmath14 up to @xmath15 tesla @xcite . |
7,374 | Suppose that you have an abstract for a scientific paper: we propose a circuit ( we call it r - pump ) comprising a linear array of three small - capacitance superconducting tunnel junctions with miniature resistors ( @xmath0 k@xmath1 ) attached to the ends of this array .
owing to the coulomb blockade effect and the effect of dissipative environment on the supercurrent , this circuit enables the gate - controlled transfer of individual cooper pairs . the first experiment on operating the r - pump
is described . .
And you have already written the first three sentences of the full article: the coulomb blockade effect in circuits with small - capacitance tunnel junctions provides the means of manipulating single charge quanta ( see , for example , the review paper by averin and likharev @xcite ) .
if periodic signals of frequency @xmath2 are applied to the gate electrodes of the circuit , a train of single charges @xmath3 can move across an array of junctions so that charge pumping , giving rise to the current @xmath4 , is achieved .
it was experimentally proven that the normal - state metallic circuits enable single electrons ( @xmath5 ) to be effectively pumped at frequencies @xmath2 of about several mhz @xcite . moreover.
Please generate the next two sentences of the article | , the accuracy of single - electron pumping can nowadays meet the requirements of fundamental metrology , @xmath6 @xmath7 @xcite .
unlike pumping of electrons , the pumping of cooper pairs ( @xmath8 ) in superconducting circuits has not been that successful so far . |
7,375 | Suppose that you have an abstract for a scientific paper: we performed thermal conductivity measurements on a single crystal of the ferromagnetic superconductor ucoge under magnetic field .
two different temperature dependencies of the thermal conductivity are observed , for @xmath0 : linear at low magnetic field and quadratic for magnetic field larger than 1 tesla . at the same field value
, a plateau appears in the field dependency of the residual term of thermal conductivity .
such observations suggest a multigap superconductivity with a line of nodes in the superconducting gap . thermal conductivity , ferromagnetic superconductor , multigap , re - entrance of superconductivity , ucoge . 74.20.rp,74.25.fc,71.27.+a , .
And you have already written the first three sentences of the full article: the orthorhombic heavy fermion system ucoge , discovered in 2007 @xcite , is one of the few compounds exhibiting long range coexistence between weak itinerant ferromagnetism ( magnetic moment m@xmath1 @xcite ) and superconductivity .
such coexistence is attested by the observation of two bulk phase transitions in specific heat measurements @xcite . @xmath2sr and nqr measurements on different samples
@xcite reveal that the compound is fully ferromagnetic below the curie temperature ( @xmath3@xmath4k ) while about 50% of the sample is superconducting below @xmath5@xmath6k @xcite ..
Please generate the next two sentences of the article | the upper critical field is extremely anisotropic , exceeding 16 tesla for @xmath7 and @xmath0 while it reaches only 0.5 tesla for @xmath8 @xcite , the easy magnetization axis @xcite .
the coexistence of ferromagnetism and superconductivity and the observed extremely high upper critical field suggest the realization of unconventional superconductivity with equal spin pairing ( triplet ) @xcite . |
7,376 | Suppose that you have an abstract for a scientific paper: the process of stimulated raman adiabatic passage ( stirap ) provides a possible route for the generation of a coherent molecular bose - einstein condensate ( bec ) from an atomic bec .
we analyze this process in a three - dimensional mean - field theory , including atom - atom interactions and non - resonant intermediate levels .
we find that the process is feasible , but at larger rabi frequencies than anticipated from a crude single - mode lossless analysis , due to two - photon dephasing caused by the atomic interactions .
we then identify optimal strategies in stirap allowing one to maintain high conversion efficiencies with smaller rabi frequencies and under experimentally less demanding conditions .
pacs numbers : 03.75.fi , 05.30.jp , 03.65.ge . .
And you have already written the first three sentences of the full article: coherent conversion of an atomic to a molecular bose - einstein condensate ( bec ) is a first step towards ` superchemistry ' @xcite , which is the stimulated emission of molecules in a chemical reaction .
a number of studies of this @xcite have shown that direct conversion via raman photoassociation @xcite appears feasible , based on stimulated free - bound and bound - bound transitions in the presence of two laser fields of different frequencies @xcite . here
pairs of atoms from the two - atom continuum of the ground electronic potential are transferred via an excited bound molecular state to a bound molecular state of a lower energy in the ground potential ..
Please generate the next two sentences of the article | raman photoassociation allows coupling to a single molecular state , which can be selected by the raman laser frequencies .
practical estimates using available lasers and transitions indicate that coherent transfer may be limited by spontaneous emission from the intermediate molecular excited electronic state . |
7,377 | Suppose that you have an abstract for a scientific paper: a covariant quark model , based both on the spectator formalism and on vector meson dominance , and previously calibrated by the physical data , is here extended to the unphysical region of the lattice data by means of one single extra adjustable parameter the constituent quark mass in the chiral limit .
we calculated the nucleon ( @xmath0 ) and the @xmath1 form factors in the universe of values for that parameter described by quenched lattice qcd .
a qualitative description of the nucleon and @xmath1 form factors lattice data is achieved for light pions . .
And you have already written the first three sentences of the full article: in principle qcd is the fundamental theory that describes hadronic systems , but its non - perturbative character makes a direct application to hadrons difficult , with the exception of the high energy and momentum transfer regime .
fortunately , at low @xmath2 effective field theories based on effective hadronic degrees of freedom have been applied with success .
examples are chiral perturbation theory @xcite , small scale expansion @xcite , soliton models and constituent quark models @xcite ..
Please generate the next two sentences of the article | constituent quark models provided consistent descriptions encompassing the low - energy baryon spectrum , elastic and inelastic form factors , charge and magnetic radii , magnetic moments , axial and pseudoscalar form factors @xcite .
although all those different frameworks may include the essential features of qcd , which are confinement and chiral symmetry , they are only partial simulations of the true underlying theory . recently , significant progress has occurred in calculations of qcd in the lattice , which evaluate the important qcd non - perturbative contributions at low @xmath2 directly from the underlying theory . up to now the applications of lattice qcd |
7,378 | Suppose that you have an abstract for a scientific paper: we report the parallax and proper motion of millisecond pulsar j0030 + 0451 , one of thirteen known isolated millisecond pulsars in the disk of the galaxy .
we obtained more than 6 years of monthly data from the 305 m arecibo telescope at 430 mhz and 1410 mhz .
we measure the parallax of psr j0030 + 0451 to be @xmath0mas , corresponding to a distance of @xmath1pc .
the cordes and lazio ( 2002 ) model of galactic electron distribution yields a dispersion measure derived distance of 317 pc which agrees with our measurement .
we place the pulsar s transverse space velocity in the range of 8 to 17 km s@xmath2 , making this pulsar one of the slowest known .
we perform a brief census of velocities of isolated versus binary millisecond pulsars .
we find the velocities of the two populations are indistinguishable .
however , the scale height of the binary population is twice that of the isolated population and the luminosity functions of the two populations are different .
we suggest that the scale height difference may be an artifact of the luminosity difference . .
And you have already written the first three sentences of the full article: a pulsar parallax can be combined with a measurement of the pulsar s dispersive delay ( the dispersion measure or dm ) to provide an accurate measure of the free electron density along the line of sight ( los ) .
psr j0030 + 0451 is one of fewer than a dozen pulsars to have its parallax measured via timing @xcite .
another dozen have been measured via vlbi ( e.g. see brisken et al ..
Please generate the next two sentences of the article | 2002 , chatterjee et al .
2004 , and also this urlshami / psrvlb / parallax.html ] ) . |
7,379 | Suppose that you have an abstract for a scientific paper: many physical experiments require analysis of the statistics of fluctuating radiation . in the case of an ideal single - photon detector ,
the contribution of photon noise to the statistics of the registered signal has been thoroughly examined . however , practical photon counters have a dead time , leading to miscounting of certain true events , and sometimes the counters generate false after - pulses .
this study investigate the impact of these two effects , and it presents the theoretical relations between the statistical moments of the radiation and the registered counts while also accounting for dead time and the probability of after - pulses .
expressions for statistical moments of any order are obtained on the basis of the generalized poisson distribution ( gpd ) . for counters with paralyzable dead time
, alternative relations for the mean and variance are derived using generally accepted formulas . as an example
, the measurements of stellar scintillation and the result of simple experiment are considered .
the results of the experimental verification of the theoretical expression confirm the need to account for the non - ideal nature of detectors in almost all similar measurements . .
And you have already written the first three sentences of the full article: when measuring the intensity of optical radiation , the registered signal is inevitably burdened with photon ( poisson ) noise , and the statistics concerning the received signal differ from those of incident radiation .
this noise is not additive and in the case of fluctuating incident radiation its power changes depending on the radiation s instantaneous intensity .
the problem concerning the contribution of photon noise in the measured statistical characteristics is considered a classical problem that has been solved many years ago ..
Please generate the next two sentences of the article | particular interest in the problem was triggered during the interpretation of the non - classical interference of light , study of raman scattering , and photon correlation spectroscopy ( see for e.g. , @xcite ) .
calculating the contribution of photon noise is important to several experimental works , particularly those that involve the photon counting method in low - light applications . |
7,380 | Suppose that you have an abstract for a scientific paper: we calculate exact one - dimensional collisionless plasma equilibria for a continuum of flux tube models , for which the total magnetic field is made up of the ` force - free ' gold - hoyle magnetic flux tube embedded in a uniform and anti - parallel background magnetic field . for a sufficiently weak background magnetic field
, the axial component of the total magnetic field reverses at some finite radius .
the presence of the background magnetic field means that the total system is not exactly force - free , but by reducing its magnitude the departure from force - free can be made as small as desired .
the distribution function for each species is a function of the three constants of motion ; namely the hamiltonian and the canonical momenta in the axial and azimuthal directions .
poisson s equation and ampre s law are solved exactly , and the solution allows either electrically neutral or non - neutral configurations , depending on the values of the bulk ion and electron flows .
these equilibria have possible applications in various solar , space and astrophysical contexts , as well as in the laboratory .
= 1 .
And you have already written the first three sentences of the full article: there has been significant recent work on vlasov - maxwell ( vm ) equilibria that are consistent with nonlinear force - free @xcite and ` nearly force - free ' @xcite magnetic fields in cartesian geometry .
therein , force - free refers to a magnetic field for which the associated current density is exactly parallel , which is the definition we shall also use , @xmath0 these works consider one - dimensional ( 1d ) collisionless current sheets , with refs . specifically calculating vm equilibrium distribution functions ( dfs ) that are self - consistent with a given specific magnetic field configuration .
a natural question to consider is whether it is also possible to find self - consistent force - free ( or nearly force - free ) vm equilibria for other geometries , in particular cylindrical geometry . in this paper.
Please generate the next two sentences of the article | we shall present particular vm equilibria for 1d magnetic fields which are nearly force - free in cylindrical geometry , i.e. flux tubes / ropes two of the archetypal field configurations in cylindrical geometry are the @xmath1-pinch ( with axial current and azimuthal magnetic field ) , a classical example of which is the bennett pinch@xcite ; and the @xmath2-pinch ( azimuthal current and axial magnetic field ) .
consideration of ` vlasov - fluid ' models of @xmath1-pinch equilibria was given in ref . |
7,381 | Suppose that you have an abstract for a scientific paper: transient collimated plasma eruptions in the solar corona , commonly known as coronal ( or x - ray ) jets , are among the most interesting manifestations of solar activity .
it has been suggested that these events contribute to the mass and energy content of the corona and solar wind , but the extent of these contributions remains uncertain .
we have recently modeled the formation and evolution of coronal jets using a three - dimensional ( 3d ) magnetohydrodynamic ( mhd ) code with thermodynamics in a large spherical domain that includes the solar wind .
our model is coupled to 3d mhd flux - emergence simulations , i.e , we use boundary conditions provided by such simulations to drive a time - dependent coronal evolution .
the model includes parametric coronal heating , radiative losses , and thermal conduction , which enables us to simulate the dynamics and plasma properties of coronal jets in a more realistic manner than done so far .
here we employ these simulations to calculate the amount of mass and energy transported by coronal jets into the outer corona and inner heliosphere . based on observed jet - occurrence rates
, we then estimate the total contribution of coronal jets to the mass and energy content of the solar wind to @xmath0% and ( 0.3 - 1.0)% , respectively .
our results are largely consistent with the few previous rough estimates obtained from observations , supporting the conjecture that coronal jets provide only a small amount of mass and energy to the solar wind .
we emphasize , however , that more advanced observations and simulations are needed to substantiate this conjecture . .
And you have already written the first three sentences of the full article: coronal ( or x - ray ) jets are collimated , transient eruptions of hot plasma observed predominantly in coronal holes and at the periphery of active regions , driven by flux emergence or cancellation ( e.g. , * ? ? ?
`` standard jets '' are launched by reconnection between open magnetic fields and expanding closed fields , while the more energetic `` blowout jets '' additionally involve an eruption of the closed fields @xcite . for detailed descriptions of coronal jets
see the recent reviews by @xcite , @xcite , and @xcite ..
Please generate the next two sentences of the article | coronagraph and in - situ observations revealed that coronal jets can produce signatures in the outer corona , sometimes even at earth or beyond @xcite .
it was therefore suggested that they contribute to powering the corona and solar wind ( e.g. , * ? ? ? |
7,382 | Suppose that you have an abstract for a scientific paper: the problem of a single impurity in one dimensional tomonaga luttinger liquids with a repulsive electron
electron interaction is discussed .
we find that the renormalization group flow diagram for the parameters characterizing the impurity is rather complex .
apart from the fixed points corresponding to two weakly connected semi infinite wires , the flow diagram contains additional fixed points which control the low temperature physics when the bare potential of the impurity is not strong .
specialpagefalse evenheadoddhead .
And you have already written the first three sentences of the full article: the recent advance in submicron technology enables fabrication of truly one dimensional ( 1d ) quantum wires .
the electron liquids in these systems are usually described in terms of the tomonaga
luttinger ( tl ) model@xcite ..
Please generate the next two sentences of the article | edge states in a two dimensional electron gas , under conditions of the fractional quantum hall effect , were argued to be tl liquids as well@xcite .
it is well known that in the tl model with a repulsive electron |
7,383 | Suppose that you have an abstract for a scientific paper: recent observations of the solar corona with the lasco coronagraph on board of the soho spacecraft have revealed the occurrence of triple helmet streamers even during solar minimum , which occasionally go unstable and give rise to particularly huge coronal mass ejections .
we present a method to calculate ( semi-)analytically self - consistent stationary configurations of triple helmet streamers which can serve as input for stability considerations and dynamical calculations .
the method is based on an asymptotic expansion procedure using the elongated structure of the streamers .
the method is very flexible and can be used in both cartesian and spherical geometry .
we discuss the effects of magnetic shear , gravity and field - aligned flow on open field lines .
example solutions illustrating the influence of each of these features on the solution structure are presented . .
And you have already written the first three sentences of the full article: recent observations of the corona with the lasco coronagraph @xcite on board of the soho spacecraft showed that the corona can be highly structured even during the solar activity minimum .
the observations revealed a triple structure of the streamer belt which was existent for several consecutive days .
the observations further showed that these triple structures occasionally go unstable leading to a seemingly new and extraordinarily huge kind of coronal mass ejection ( global cmes ) ..
Please generate the next two sentences of the article | natural questions arising from these observations are whether the helmet streamer triple structure is directly connected with or responsible for the occurrence of global cmes and what is the physical mechanism of their formation .
the aim of this paper is to provide a first step towards a better theoretical understanding of these phenomena . the structure of helmet streamers and their stability has been studied both observationally and theoretically for a long time ( e.g. @xcite , @xcite ; @xcite , @xcite ; @xcite , @xcite ; @xcite , @xcite ; @xcite , @xcite ; @xcite , @xcite ; @xcite , @xcite ; @xcite , @xcite ; @xcite , @xcite ) . |
7,384 | Suppose that you have an abstract for a scientific paper: we investigate gradient of magnetic field across neutral lines ( nls ) , and compare their properties for nls with and without the chromospheric filaments .
our results show that there is a range of preferred magnetic field gradients where the filament formation is enhanced . on the other hand
, a horizontal gradient of magnetic field across a nl alone does not appear to be a single factor that determines if a filament will form ( or not ) in a given location . .
And you have already written the first three sentences of the full article: chromospheric filaments ( prominences at the limb ) are one of the major features characterizing the solar activity in low solar atmosphere ( chromosphere and low corona ) .
filament eruptions are at the core of many solar - terrestrial effects or space weather .
the filaments are formed along magnetic polarity inversion lines , but only a minority of these neutral lines ( nls ) has filaments above them ..
Please generate the next two sentences of the article | several studies were made trying to find the necessary conditions for filament formation , but still there is no clear understanding of this @xcite .
it was found by previous studies that filaments form only in filament channels ( for review , see ) , which overlay nls . |
7,385 | Suppose that you have an abstract for a scientific paper: this is a survey on the state - of - the - art of the classification of finite - dimensional complex hopf algebras .
this general question is addressed through the consideration of different classes of such hopf algebras .
pointed hopf algebras constitute the class best understood ; the classification of those with abelian group is expected to be completed soon and there is substantial progress in the non - abelian case .
_ dedicado a biblioco 34 _ 16t05 , 16t20 , 17b37 , 16t25 , 20g42 .
hopf algebras , quantum groups , nichols algebras . .
And you have already written the first three sentences of the full article: hopf algebras were introduced in the 1950 s from three different perspectives : algebraic groups in positive characteristic , cohomology rings of lie groups , and group objects in the category of von neumann algebras .
the study of non - commutative non - cocommutative hopf algebras started in the 1960 s .
the fundamental breakthrough is drinfeld s report @xcite . among many contributions and ideas ,.
Please generate the next two sentences of the article | a systematic construction of solutions of the quantum yang - baxter equation ( qybe ) was presented .
let @xmath0 be a vector space . |
7,386 | Suppose that you have an abstract for a scientific paper: we examine the maximum negative energy density which can be attained in various quantum states of a massless scalar field .
we consider states in which either one or two modes are excited , and show that the energy density can be given in terms of a small number of parameters .
we calculate these parameters for several examples of superposition states for one mode , and entangled states for two modes , and find the maximum magnitude of the negative energy density in these states .
we consider several states which have been , or potentially will be , generated in quantum optics experiments . .
And you have already written the first three sentences of the full article: it has been proven , beginning in the early 1960 s @xcite , that there always exist states with negative energy density in quantum field theory .
some specific examples include the casimir effect @xcite and squeezed states @xcite , both of which have been experimentally realized .
( although the energy density itself is far too small to be directly measured . ).
Please generate the next two sentences of the article | negative energy is also required for black hole evaporation , and hence for the consistency of the laws of black hole physics with those of thermodynamics . on the other hand
, unrestricted amounts of negative energy could produce bizarre effects , for example , violations of the second law of thermodynamics @xcite . |
7,387 | Suppose that you have an abstract for a scientific paper: we study the effects of random homogenous and isotropic initial conditions on decaying magnetohydrodynamics ( mhd ) .
we show that for an initial distribution of velocity and magnetic field fluctuations , appropriately defined structure functions decay as power law in time .
we also show that for a suitable choice of initial cross - correlations between velocity and magnetic fields even order structure functions acquire anomalous scaling in time where as scaling exponents of the odd order structure functions remain unchanged .
we discuss our results in the context of fully developed mhd turbulence . .
And you have already written the first three sentences of the full article: in the absence of external forcing the fluid can not maintain its steady state because of the continous dissipation of energy .
the decay of kinetic energy in incompressible fluid turbulence has been explored in several studies ( see , e.g. , @xcite ) .
these studies , principally numerical , indicate that kinetic energy decays as @xmath0 , where @xmath1 is the initial time , i.e. the time when the initial forcing is switched off ..
Please generate the next two sentences of the article | the value of @xmath2 seems to depend on the initial state .
similarly , recent numerical studies of decaying mhd turbulence @xcite also suggest that the total energy decays as power of time |
7,388 | Suppose that you have an abstract for a scientific paper: we study the impact of beam polarization on radiative neutralino production @xmath0 at the international linear collider .
we show that longitudinal polarized beams significantly enhance the signal and simultaneously reduce the standard model background from radiative neutrino production @xmath1 .
we point out that the radiative production of neutralinos could be the only accessible susy particles , if neutralinos , charginos , sleptons , as well as squarks and gluinos are too heavy to be pair - produced in the first stage of the ilc at @xmath2 gev .
( 10,10 ) ( 45,260)bonn - th-2007 - 04 .
And you have already written the first three sentences of the full article: the minimal supersymmetric standard model ( mssm ) is a promising extension of the standard model of particle physics ( sm ) @xcite . at the international linear collider ( ilc )
@xcite , the masses , decay widths , couplings , and spins of the new susy particles can be measured with high precision @xcite .
in particular , the lightest states like pairs of neutralinos , charginos , and sleptons , can be studied in the initial stage of the ilc , with a center - of - mass energy @xmath3 gev , and a luminosity of @xmath4 fb@xmath5 ..
Please generate the next two sentences of the article | the lightest susy state is a pair of radiatively produced neutralinos @xcite @xmath6 the signal is a single high energetic photon , radiated off the incoming beams or off the exchanged selectrons , and missing energy , carried by the neutralinos @xcite .
the main standard model background is photons from radiatively produced neutrinos @xmath1 @xcite . in order to quantify whether an excess of signal photons from radiative neutralino production , @xmath7 , can be observed over the sm background photons , @xmath8 |
7,389 | Suppose that you have an abstract for a scientific paper: we perform a series of high - resolution n - body simulations of cosmological structure formation starting from gaussian and non - gaussian initial conditions .
we adopt the best - fitting cosmological parameters from the third- and fifth - year data releases of the _ wilkinson microwave anisotropy probe _ and we consider non - gaussianity of the local type parameterised by eight different values of the non - linearity parameter @xmath0 .
building upon previous work based on the gaussian case , we show that , when expressed in terms of suitable variables , the mass function of friends - of - friends haloes is approximately universal ( i.e. independent of redshift , cosmology , and matter transfer function ) to good precision ( nearly 10 per cent ) also in non - gaussian scenarios . we provide fitting formulae for the high - mass end ( @xmath1 ) of the universal mass function in terms of @xmath0 , and we also present a non - universal fit in terms of both @xmath0 and @xmath2 to be used for applications requiring higher accuracy . for gaussian initial conditions ,
we extend our fit to a wider range of halo masses ( @xmath3 ) and we also provide a consistent fit of the linear halo bias . we show that , for realistic values of @xmath0 , the matter power - spectrum in non - gaussian cosmologies departs from the gaussian one by up to two per cent on the scales where the baryonic - oscillation features are imprinted on the two - point statistics . finally , using both the halo power spectrum and the halo - matter cross spectrum , we confirm the strong @xmath4-dependence of the halo bias on large scales ( @xmath5 mpc@xmath6 ) which was already detected in previous studies . however , we find that commonly used parameterisations based on the peak - background split do not provide an accurate description of our simulations which present extra dependencies on the wavenumber , the non - linearity parameter and , possibly , the clustering strength .
we provide an accurate fit of the simulation data that can be....
And you have already written the first three sentences of the full article: the detection of temperature anisotropies in the cosmic microwave background ( cmb ) provided evidence that large - scale structure formation in the universe was seeded by small density fluctuations generated at early times .
the statistical properties of these seeds are usually modelled with a gaussian random field .
historically the gaussian approximation was introduced for mathematical convenience . in the absence of a solid model for the generation of density fluctuations.
Please generate the next two sentences of the article | the gaussian hypothesis was accepted on the basis of the central limit theorem ( e.g. @xcite and references therein ) .
the advent of inflationary models provided further support for gaussianity . |
7,390 | Suppose that you have an abstract for a scientific paper: local diffusion coefficients in disordered systems such as spin glass systems and living cells are highly heterogeneous and may change over time .
such a time - dependent and spatially heterogeneous environment results in irreproducibility of single - particle - tracking measurements .
irreproducibility of time - averaged observables has been theoretically studied in the context of weak ergodicity breaking in stochastic processes . here ,
we provide rigorous descriptions of equilibrium and non - equilibrium diffusion processes for the annealed transit time model , which is a heterogeneous diffusion model in living cells .
we give analytical solutions for the mean square displacement ( msd ) and the relative standard deviation of the time - averaged msd for equilibrium and non - equilibrium situations .
we find that the time - averaged msd grows linearly with time and that the diffusion coefficients are intrinsically random in non - equilibrium situations .
our findings pave the way for a theoretical understanding of distributional behavior of the diffusion coefficients in disordered systems .
february 2014 _ keywords _ : anomalous diffusion , ergodicity , non - equilibrium processes .
And you have already written the first three sentences of the full article: transporting biological molecules in living cells plays a key role in biochemical interactions , transmembrane signaling , and efficient reactions . in single - particle tracking ( spt ) ,
the motion of proteins or lipids is tracked to determine directly the diffusivity and to understand the biological role of diffusivity .
therefore , it is expected that spt experiments will provide new insight into molecular transport in living cells . in fact.
Please generate the next two sentences of the article | , many spt experiments reveal anomalous dynamics such as subdiffusion , aging , fluctuating diffusivity , and heterogeneous environments in living cells @xcite .
mean square displacement ( msd ) is the most popular observable for characterizing the diffusivity of particles . |
7,391 | Suppose that you have an abstract for a scientific paper: possible phase transition of strongly interacting matter from hadron to a quark - gluon plasma ( qgp ) state have in the past received considerable interest .
it has been suggested that this problem might be treated by percolation theory .
the color string percolation model ( cspm ) is used to determine the equation of state ( eos ) of the qgp produced in central au - au collisions at rhic energies .
the bulk thermodynamic quantities- energy density , entropy density and the sound velocity- are obtained in the framework of cspm .
it is shown that the results are in excellent agreement with the recent lattice qcd calculations(lqcd ) .
relativistic heavy - ion collisions , percolation , qgp , eos .
And you have already written the first three sentences of the full article: one of the main goal of the study of relativistic heavy ion collisions is to study the deconfined matter , known as quark - gluon plasma(qgp ) , which is expected to form at large densities .
it has been suggested that the transition from hadronic to qgp state can be treated by percolation theory @xcite .
the formulation of percolation problem is concerned with elementary geometrical objects placed on a random d - dimensional lattice ..
Please generate the next two sentences of the article | the objects have a well defined connectivity radius @xmath0 , and two objects can communicate if the distance between them is less than @xmath0 .
several objects can form a cluster of communication . at certain density of the objects a infinite cluster appears which spans the entire system . |
7,392 | Suppose that you have an abstract for a scientific paper: destructive quantum interference ( dqi ) in single molecule electronics is a purely quantum mechanical effect and entirely defined by inherent properties of the molecule in the junction such as its structure and symmetry .
this definition of dqi by molecular properties alone suggests its relation to other more general concepts in chemistry as well as the possibility of deriving simple models for its understanding and molecular device design .
recently , two such models have gained wide spread attention , where one was a graphical scheme based on visually inspecting the connectivity of carbon sites in conjugated @xmath0 systems in an atomic orbital ( ao ) basis and the other one put the emphasis on the amplitudes and signs of the frontier molecular orbitals ( mos ) .
there have been discussions on the range of applicability for these schemes , but ultimately conclusions from topological molecular hamiltonians should not depend on whether they are drawn from an ao or a mo representation , as long as all the orbitals are taken into account . in this article
we clarify the relation between both models in terms of the zeroth order green s function and compare their predictions for a variety of systems . from this comparison
we conclude that for a correct description of dqi from a mo perspective it is necessary to include the contributions from all mos rather than just those from the frontier orbitals .
the cases where dqi effects can be successfully predicted within a frontier orbital approximation we show to be limited to alternant even - membered hydrocarbons , as a a direct consequence of the coulson - rushbrooke pairing theorem in quantum chemistry .
_ .. you have a program , for god s sake use it , play with it , do a calculation on any small problem related to your problem . let the calculations teach you .
they are so easy ! shall we stop teasing one another about mo and vb ? _
... quantum chemistry has given us two wonderful tools to reason about chemistry , and denying any one of....
And you have already written the first three sentences of the full article: first experimental studies of electron transport through single molecules attached to metal contacts by using a scanning tunnelling microscope ( stm ) or mechanically controlled break junction techniques @xcite , also triggered considerable theoretical activity in this field since the beginning of the new millennium .
the theoretical framework most widely used in this context is a non - equilibrium green s function ( negf ) formalism @xcite , where coherent electron transmission according to landauer s theory is assumed .
the conductance of a molecular junction can then be described in dependence on the incoming electron s energy @xmath1 in terms of the transmission probability @xmath2 , which within negf is defined as @xmath3,\ ] ] where the self energy matrices @xmath4 and @xmath5 contain the coupling of the molecule to the left and right electrodes and @xmath6 and @xmath7 are the retarded and advanced green s functions ( gf ) of the ( extended ) molecule ..
Please generate the next two sentences of the article | the negf formalism has been implemented in a variety of codes , where in combination with density functional theory ( dft ) it allows for a first principles treatment of the conductance of single molecule junctions @xcite@xmath8@xcite .
the usefulness of such calculations , however , still relies on simple models for interpreting them in terms of quantum chemical concepts such as atomic orbitals ( aos ) or molecular orbitals ( mos ) in order to achieve a qualitative understanding of the observed electron transport characteristics in the context of our general knowledge of the electronic properties of molecules or what is regarded as chemical intuition . in principle |
7,393 | Suppose that you have an abstract for a scientific paper: we discuss topological properties of the ground state of spatially homogeneous ensemble of fermions .
there are several classes of topologically different fermionic vacua ; in each case the momentum space topology of the vacuum determines the low - energy ( infrared ) properties of the fermionic energy spectrum . among them
there is class of the gapless systems which is characterized by the fermi - hypersurface , which is the topologically stable singularity .
this class contains the conventional landau fermi - liquid and also the non - landau luttinger fermi - liquid .
another important class of gapless systems is characterized by the topologically stable point nodes ( fermi points ) .
superfluid @xmath0he - a and electroweak vacuum belong to this universality class .
the fermionic quasiparticles ( particles ) in this class are chiral : close to the fermi points they are left - handed or right - handed massless relativistic particles . since the spectrum becomes relativistic at low energy , the symmetry of the system is enhanced in the low - energy edge .
the low - energy dynamics acquires local invariance , lorentz invariance and general covariance , which become better and better when the energy decreases .
interaction of the fermions near the fermi point leads to collective bosonic modes , which look like effective gauge and gravitational fields .
since the vacuum of superfluid @xmath0he - a and electroweak vacuum are topologically similar , we can use @xmath0he - a for simulation of many phenomena in high energy physics , including axial anomaly .
@xmath0he - a textures induce a nontrivial effective metrics of the space , where the free quasiparticles move along geodesics . with @xmath0he
- a one can simulate event horizons , hawking radiation , rotating vacuum , conical space , etc .
[ @twocolumnfalse ] .
And you have already written the first three sentences of the full article: the physical vacuum is a complicated condensed matter @xcite . at the moment we know only the low - energy properties of this substance , i.e. the properties at energies much smaller than the planck energy scale , @xmath1 , where @xmath2 is newton s constant .
we know that at the low - energy edge our vacuum has many different symmetries : @xmath3 and @xmath4 gauge symmetries , lorentz invariance , general coordinate invariance , and dicrete cpt symmetry . with increasing energy more elements of symmetry
are added : @xmath5 symmetry of weak interactions , probably the gut symmetry and even supersymmetry ..
Please generate the next two sentences of the article | when the temperature dicreases such symmetries become spontaneously broken . this is the traditional point of view , which is supported by the observation of the similar symmetry breaking in different ( many - body ) condensed matter systems : superfluids , superconductors , magnets , liquid and ordinary crystals .
however there is another and actually opposite point of view : all symmetries known in the universe spontaneously ( but without any phase transition ) appear at the low - energy corner@xcite . they become more and more pronounced the lower the energy . |
7,394 | Suppose that you have an abstract for a scientific paper: the _ chandra _ source catalog ( csc ) is a general purpose virtual x - ray astrophysics facility that provides access to a carefully selected set of generally useful quantities for individual x - ray sources , and is designed to satisfy the needs of a broad - based group of scientists , including those who may be less familiar with astronomical data analysis in the x - ray regime .
the first release of the csc includes information about 94,676 distinct x - ray sources detected in a subset of public acis imaging observations from roughly the first eight years of the _ chandra _ mission .
this release of the catalog includes point and compact sources with observed spatial extents @xmath0 .
the catalog ( 1 ) provides access to the best estimates of the x - ray source properties for detected sources , with good scientific fidelity , and directly supports scientific analysis using the individual source data ; ( 2 ) facilitates analysis of a wide range of statistical properties for classes of x - ray sources ; and ( 3 ) provides efficient access to calibrated observational data and ancillary data products for individual x - ray sources , so that users can perform detailed further analysis using existing tools .
the catalog includes real x - ray sources detected with flux estimates that are at least 3 times their estimated @xmath1 uncertainties in at least one energy band , while maintaining the number of spurious sources at a level of @xmath2 false source per field for a @xmath3 observation . for each detected source
, the csc provides commonly tabulated quantities , including source position , extent , multi - band fluxes , hardness ratios , and variability statistics , derived from the observations in which the source is detected .
in addition to these traditional catalog elements , for each x - ray source the csc includes an extensive set of file - based data products that can be manipulated interactively , including source images , event lists , light curves , and spectra from each observation....
And you have already written the first three sentences of the full article: ever since _ uhuru _ @xcite , x - ray astronomy missions have had a tradition of publishing catalogs of detected x - ray sources , and these catalogs have provided the fundamental datasets used by numerous studies aimed at characterizing the properties of the x - ray sky . while source catalogs are the primary data products from x - ray sky surveys ( e.g. , * ? ? ?
* ; * ? ? ?
* ; * ? ? ?.
Please generate the next two sentences of the article | * ; * ? ? ?
* ; * ? ? ? |
7,395 | Suppose that you have an abstract for a scientific paper: adaptation in a fluctuating environment is a process of fueling environmental information to gain fitness .
living systems have gradually developed strategies for adaptation from random and passive diversification of the phenotype to more proactive decision making , in which environmental information is sensed and exploited more actively and effectively .
understanding the fundamental relation between fitness and information is therefore crucial to clarify the limits and universal properties of adaptation . in this work ,
we elucidate the underlying stochastic and information - thermodynamic structure in this process , by deriving causal fluctuation relations ( frs ) of fitness and information .
combined with a duality between phenotypic and environmental dynamics , the frs reveal the limit of fitness gain , the relation of time reversibility with the achievability of the limit , and the possibility and condition for gaining excess fitness due to environmental fluctuation .
the loss of fitness due to causal constraints and the limited capacity of real organisms is shown to be the difference between time - forward and time - backward path probabilities of phenotypic and environmental dynamics .
furthermore , the frs generalize the concept of evolutionary stable state ( ess ) for fluctuating environment by giving the probability that the optimal strategy on average can be invaded by a suboptimal one owing to rare environmental fluctuation .
these results clarify the information thermodynamic structures in adaptation and evolution . .
And you have already written the first three sentences of the full article: adaptation is fundamental to all organisms for their survival and evolutionary success in a changing environment .
in the course of evolution , living systems have gradually attained and developed more active and efficient strategies for adaptation , which generally accompany more effective use of environmental information .
understanding how the use of information is linked to the efficiency of adaptation is crucial to clarify the fundamental limits and universal properties of biological adaptations@xcite ..
Please generate the next two sentences of the article | the most primitive strategy for adaptation is to randomly generate genetic and phenotypic heterogeneity in a population @xcite .
provided that a sufficiently large heterogeneity is constantly generated in the population , a fraction of organisms can , by chance , have the types adaptive to the upcoming environmental state and circumvent extinction of the population at the cost of others with non - adaptive types@xcite . |
7,396 | Suppose that you have an abstract for a scientific paper: we identify the extended einstein ipc x - ray source , 1e0657 - 56 , with a previously unknown cluster of galaxies at a redshift of @xmath0 .
optical ccd images show the presence of a gravitational arc in this cluster and galaxy spectra yield a cluster velocity dispersion of @xmath1 km s@xmath2 .
x - ray data obtained with the rosat hri and asca indicate that 1e0657 - 56 is a highly luminous cluster in which a merger of subclusters may be occurring .
the temperature of the hot gas in 1e0657 - 56 is @xmath3 , which makes it an unusually hot cluster , with important cosmological implications . .
And you have already written the first three sentences of the full article: measurements of the gas temperature in clusters of galaxies is a potentially powerful tool for testing cosmological models since the gas temperature provides a direct measurement of the cluster mass .
the cluster mass function is directly traceable to the underlying cosmology and can be used to determine the normalization and slope of the initial mass fluctuation spectrum in the early universe ( peebles et al .
1989 , henry & arnaud 1991 , lilje 1992 , bartlett & silk 1993 , white et al ..
Please generate the next two sentences of the article | 1993 , colafrancesco & vittorio 1994 , hattori et al .
1995 , eke et al . |
7,397 | Suppose that you have an abstract for a scientific paper: we are developing time- and energy - resolved near - ir / optical / uv photon detectors based on sharp superconducting - normal transition edges in thin films .
we report observations of the crab pulsar made during prototype testing at the mcdonald 2.7 m telescope with a fiber - coupled transition - edge sensor ( tes ) system .
these data show substantial ( @xmath0 ) , rapid variations in the spectral index through the pulse profile , with a strong phase - varying ir break across our energy band .
these variations correlate with x - ray spectral variations , but no single synchrotron population can account for the full spectral energy distribution ( sed ) .
we also describe test spectrophotopolarimetry observations probing the energy dependence of the polarization sweep ; this may provide a new key to understanding the radiating particle population . .
And you have already written the first three sentences of the full article: transition - edge sensor ( tes ) detectors are showing great promise as fast bolometer arrays in astronomical applications from the sub - millimeter through the x - rays ( wollman , _
et al._2000 ) . in the near - ir / optical / uv
range these devices offer good broad - band quantum efficiency ( qe ) , high time resolution and modest energy resolution and saturation count - rate ( cabrera _ et al._1998 , romani _.
Please generate the next two sentences of the article | et al._1999 ) . along with competing cryogenic technologies ( e.g. superconducting tunnel junction devices , stjs ; perryman , foden & peacock 1993 , perryman _
et al._1999 ) these sensor arrays offer the potential for important new capabilities , particularly for the study of rapidly varying compact object systems . |
7,398 | Suppose that you have an abstract for a scientific paper: the dynamics of the movement of gas is discussed for two - chambered polarized @xmath0he target cells of the sort that have been used successfully for many electron scattering experiments .
a detailed analysis is presented showing that diffusion is a limiting factor in target performance , particularly as these targets are run at increasingly high luminosities .
measurements are presented on a new prototype polarized @xmath0he target cell in which the movement of gas is due largely to convection instead of diffusion .
nmr tagging techniques have been used to visualize the gas flow , showing velocities along a cylindrically - shaped target of between @xmath1 .
the new target design addresses one of the principle obstacles to running polarized @xmath0he targets at substantially higher luminosities while simultaneously providing new flexibility in target geometry . .
And you have already written the first three sentences of the full article: nuclear - polarized @xmath0he has proven to be useful in a number of different areas of research . in electron scattering , polarized @xmath0he provides a means for studying spin - dependent interactions involving neutrons .
this is because , to first approximation , a @xmath0he nucleus is comprised of two protons whose spins are paired , and a single neutron that accounts for most of the nuclear spin @xcite .
an important early example of the use of polarized @xmath0he in electron scattering came during an experiment to measure the internal spin structure of the neutron at the stanford linear accelerator center ( slac ) , e142 @xcite . polarized.
Please generate the next two sentences of the article | @xmath0he has also been used to measure the electric form factor of the neutron @xmath2 , including a recent experiment at jefferson laboratory ( jlab ) in newport news , va @xcite .
important applications of polarized @xmath0he have also included its use as a neutron polarizer @xcite , and , together with polarized @xmath3xe , as a source of signal for magnetic resonance imaging @xcite . |
7,399 | Suppose that you have an abstract for a scientific paper: gamma - ray bursts of short duration may harbor vital clues to the range of phenomena producing bursts .
however , recent progress from the observation of optical counterparts has not benefitted the study of short bursts .
we have searched for early optical emission from six gamma - ray bursts using the rotse - i telephoto array .
three of these events were of short duration , including grb 980527 which is among the brightest short bursts yet observed .
the data consist of unfiltered ccd optical images taken in response to batse triggers delivered via the gcn .
for the first time , we have analyzed the entire @xmath0 field covered for five of these bursts .
in addition , we discuss a search for the optical counterpart to grb 000201 , a well - localized long burst .
single image sensitivities range from 13th to 14th magnitude around 10 s after the initial burst detection , and 14 - 15.8 one hour later .
no new optical counterparts were discovered in this analysis suggesting short burst optical and gamma - ray fluxes are uncorrelated . .
And you have already written the first three sentences of the full article: during the last decade , gamma - ray burst classification has emerged as a promising tool to understand these events . in the pre - batse data ,
there were indications of a bimodality in the temporal durations of non - repeating bursts @xcite , as well as a modest correlation of duration with spectral hardness @xcite .
these results were confirmed by data from the burst and transient source experiment ( batse ) which show that short bursts inhabit a distinct region of the duration / spectral hardness parameter space @xcite ..
Please generate the next two sentences of the article | more recently , theoretical work has made use of the batse archive to attempt to determine the processes which distinguish short and long bursts .
there is some evidence that short grbs arise from internal shock processes @xcite , and that they are differentiated from long bursts by the ejecta shell geometry ( eg . |
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