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11,800 |
Suppose that you have an abstract for a scientific paper: we present a universal method to create a tunable , artificial vector gauge potential for neutral particles trapped in an optical lattice .
the necessary peierls phase of the hopping parameters between neighboring lattice sites is generated by applying a suitable periodic inertial force such that the method does not rely on any internal structure of the particles .
we experimentally demonstrate the realization of such artificial potentials , which generate ground state superfluids at arbitrary non - zero quasi - momentum .
we furthermore investigate possible implementations of this scheme to create tuneable magnetic fluxes , going towards model systems for strong - field physics .
first introduced in electromagnetism , gauge fields play a central role in the description of interactions in physics , from particle physics to condensed matter . currently there is a large interest to introduce gauge fields into model systems in order to study fundamental aspects of physics @xcite .
especially the emulation of synthetic electric and magnetic fields for of ultracold atomic systems is crucial in order to extend their proven quantum simulation abilities further , e.g. to quantum hall physics or topological insulators . in this context , the analogy between inertial and lorentz forces triggered the simulation of homogeneous artificial magnetic fields using rapidly rotating trapped ultracold gases @xcite .
recently , several proposals ( @xcite and references therein ) and experimental realizations focused on the simulation of a gauge vector potential @xmath0 either in a bulk system @xcite or in optical lattices @xcite .
the realized schemes exploit the berry phase which arises when the atomic ground state is split in several space - dependent sublevels , as in the presence of an electromagnetic field .
hence they rely on the coupling between internal and external degrees of freedom induced by laser fields . here
we demonstrate the generation of artificial gauge potentials for neutral atoms in an....
And you have already written the first three sentences of the full article: the 1d optical lattice is generated by two independent , phase stabilized laser beams at @xmath79=830 nm , intersecting at an angle of 117@xmath80 in the @xmath81 plane , which results in a lattice spacing of @xmath27=486 nm along @xmath82 .
the radial dimensions are only weakly confined by an optical dipole trap of trap frequency @xmath83=18@xmath582hz and @xmath84=45 - 55hz .
we load a bose einstein condensate of rubidium 87 atoms into the lattice , which results in an occupation of around 80 pancake - like lattice sites ..
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the lattice depth is 10@xmath581@xmath85 , where @xmath85=2@xmath86=3.33khz .
this results in a bare tunneling rate of roughly 0.007@xmath85 .
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11,801 |
Suppose that you have an abstract for a scientific paper: the origin of the far - infrared emission from the nearby radio galaxy m87 remains a matter of debate .
some studies find evidence of a far - infrared excess due to thermal dust emission , whereas others propose that the far - infrared emission can be explained by synchrotron emission without the need for an additional dust emission component .
we observed m87 with pacs and spire as part of the herschel virgo cluster survey ( hevics ) .
we compare the new herschel data with a synchrotron model based on infrared , submm and radio data to investigate the origin of the far - infrared emission .
we find that both the integrated sed and the herschel surface brightness maps are adequately explained by synchrotron emission . at odds with previous claims , we find no evidence of a diffuse dust component in m87 . .
And you have already written the first three sentences of the full article: at a distance of 16.7 mpc , m87 is the dominant galaxy of the virgo cluster .
it is one of the nearest radio galaxies and was the first extragalactic x - ray source to be identified . because of its proximity
, many interesting astrophysical phenomena can be studied in more detail in m87 than in other comparable objects ..
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particularly remarkable is the prominent jet extending from the nucleus , visible throughout the electromagnetic spectrum .
the central regions of m87 , in particular the structure of the jet , have been studied and compared intensively at radio , optical , and x - ray wavelengths .
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11,802 |
Suppose that you have an abstract for a scientific paper: in 2011 the nobel prize in physics was awarded for the 1998 discovery of the nonzero cosmological constant .
this discovery is very important and surely worth to receive the nobel prize .
however , years earlier several papers had been published ( pal , horvth , & lukcs 1992 ; holba et al .
1992 , holba et al .
1994 ) about a very similar discovery from observational data . .
And you have already written the first three sentences of the full article: `` the nobel prize in physics 2011 was divided , one half awarded to saul perlmutter , the other half jointly to brian p. schmidt and adam g. riess for the discovery of the accelerating expansion of the universe through observations of distant supernovae . '' the nobelprize.org wrote .
two research teams , supernova cosmology project ( scp ) lead by saul perlmutter and high - z supernova search team ( hzt ) headed by brian schmidt , raced to map the universe by locating the most distant supernovae .
the two research teams found over 50 distant supernovae which were dimmer than expected - this was a sign that the expansion of the universe was accelerating [ 1 ] , [ 2 ] . theoretically , this was not new idea since albert einstein came out the idea of cosmological constant ( often marked lambda ) ..
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einstein did that because he was guided by the paradigm of the day that the universe was static . when he heard the edwin hubble discovery that the universe was actually expanding he declared that the inclusion of the cosmological constant was his `` biggest blunder '' .
since there was no observation for cosmological constant after that most scientists assumed that lambda is zero .
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11,803 |
Suppose that you have an abstract for a scientific paper: we present results from a mosaic of nine _ chandra _ observations of m86 and the surrounding field .
we detect three main diffuse components : the virgo icm at @xmath02.4 kev , the extended halo of m86 at @xmath01.2 kev , and the cooler central and stripped gas of m86 at @xmath00.8 kev .
the most striking feature is a long tail of emission , which consists of a plume @xmath0 4north of m86 and two main extensions emanating from the plume .
based on the morphology and temperature structure of the tail , we conclude that it is formed by ram pressure stripping of m86 as it falls into the virgo cluster and interacts with the virgo icm , in agreement with earlier work .
the tail is 150 kpc in projection , and a simple estimate gives a lower limit on the true length of the tail of 380 kpc , making this the longest ram pressure stripped tail presently known .
the total gas mass in the plume ( @xmath1 ) and tail ( @xmath2 ) is about three times that in the core of m86 , which supports the scenario where most of the gas was stripped rapidly and recently .
the projected position of the plume can be understood if m86 has an aspherical potential , as suggested by optical isophotes .
ram pressure stripping from an aspherical potential can also explain the split `` double tails '' seen in m86 and in other virgo cluster galaxies in the field .
the large line - of - sight velocity of m86 ( 1550 @xmath3with respect to m87 ) , its position relative to the virgo cluster , and the orientation of the tail tightly constrain its orbital parameters . the data are inconsistent with a radial orbit , and imply inner and outer turning radii of @xmath4 kpc and @xmath5 mpc , indicating that m86 is , at best , only weakly bound to the virgo cluster . .
And you have already written the first three sentences of the full article: m86 ( ngc 4406 ) is a bright elliptical ( e3/s0 ) galaxy in the virgo cluster of galaxies .
it is the dominant member of one of the larger subgroups within virgo ( binggeli et al .
1993 ; bhringer et al . 1994 ; schindler et al ..
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its line - of - sight velocity relative to m87 , the dominant member of the virgo cluster , is -1550 km s@xmath6 , much higher than the average cluster velocity dispersion ( smith et al .
the x - ray surface brightness distribution is unusual , with a large `` plume '' extending to the northwest from m86 , which was first noticed as part of a survey of virgo cluster galaxies undertaken with the _ einstein observatory _ ( forman et al . 1979 ) .
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11,804 |
Suppose that you have an abstract for a scientific paper: a thin film of ferromagnetically ordered material proximate to the surface of a three - dimensional topological insulator explicitly breaks the time - reversal symmetry of the surface states . for an out - of - plane ferromagnetic order parameter on the surface , the parity is also broken , since the dirac fermions become massive .
this leads in turn to the generation of a topological chern - simons term by quantum fluctuations .
on the other hand , for an in - plane magnetization the surface states remain gapless for the non - interacting dirac fermions . in this work
we study the possibility of spontaneous breaking of parity due to a dynamical gap generation on the surface in the presence of a local , hubbard - like , interaction of strength @xmath0 between the dirac fermions .
a gap and a chern - simons term are generated for @xmath0 larger than some critical value , @xmath1 , provided the number of dirac fermions , @xmath2 , is odd . for an even number of dirac fermions
the masses are generated in pairs having opposite signs , and no chern - simons term is generated .
we discuss our results in the context of recent experiments in eus / bi@xmath3se@xmath4 heterostructures . .
And you have already written the first three sentences of the full article: due to its unique properties , topological insulators ( ti ) @xcite are likely to play a major role as a component material in different types of heterostructures . for instance , with a view towards spintronics applications,@xcite heterostructures involving ferromagnetic ( fm ) materials or magnetic impurities have been studied both theoretically @xcite and experimentally.@xcite underlying the many applications of magnetic heterostructures involving tis is the so - called axion electrodynamics,@xcite which was shown to distinguish the electromagnetic response of tis from ordinary insulators in an essential way.@xcite quite generally , it was shown in ref . that the lagrangian describing the electromagnetic response of _ all _ three - dimensional insulators is given by , @xmath5 where @xmath6 is in general a scalar field , the so - called axion,@xcite and @xmath7 is the fine - structure constant . in ordinary insulators
@xmath6 vanishes , but this is not the case in tis.@xcite in its simplest variant the axion field is uniform and assumes the value @xmath8 for a bulk time - reversal ( tr ) invariant ti.@xcite for uniform @xmath6 the axion term becomes a surface term , leaving therefore the maxwell equations unaffected.@xcite despite being a surface term when @xmath6 is uniform , the axion term still plays an important role in finite samples .
indeed , if we imagine a semi - infinite ti sample extending over @xmath9 up to the surface @xmath10 , we can use a covariant formalism to obtain , @xmath11 with the latin indices running over four - dimensional spacetime ..
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application of gauss theorem yields , @xmath12 where the greek indices run over @xmath13 , @xmath14 , and @xmath15 .
the above axion action at the surface actually represents a chern - simons ( cs ) term.@xcite as the chern - simons term does not depend on the metric , _
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11,805 |
Suppose that you have an abstract for a scientific paper: we present a new parametrization of a su(3 ) fixed point ( fp ) gauge action using smeared ( `` fat '' ) gauge links .
we report on the scaling behaviour of the fp action on coarse lattices by means of the static quark - antiquark potential , the hadronic scale @xmath0 , the string tension @xmath1 and the critical temperature @xmath2 of the deconfining phase transition .
in addition , we investigate the low lying glueball masses where we observe no scaling violations within the statistical errors . .
And you have already written the first three sentences of the full article: it is well known that on rather coarse lattices with lattice spacings @xmath3 0.1 fm the wilson gauge action produces quite large cut - off effects . on the other hand ,
decreasing the lattice spacing below 0.1 fm becomes increasingly difficult for simulations including fermions . therefore using a better
, i.e. improved gauge action might well be important ..
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one possible way of constructing non - perturbatively improved lattice gauge theories is provided by the fixed point ( fp ) action approach @xcite .
fp actions are classically perfect , i.e. they have no lattice artefacts on classical configurations . in particular , they possess exactly scale invariant instanton solutions .
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11,806 |
Suppose that you have an abstract for a scientific paper: we study flexible polymer macromolecules in a crowded ( porous ) environment , modelling them as self - attracting self - avoiding walks on site - diluted percolative lattices in space dimensions @xmath0 , @xmath1 .
the influence of stretching force on the polymer folding and properties of globule - coil transitions are analyzed . applying the pruned - enriched rosenbluth chain - growth method ( perm )
, we estimate the transition temperature @xmath2 between collapsed and extended polymer configurations and construct the phase diagrams of the globule - coil coexistence when varying temperature and stretching force . the transition to a completely stretched state , caused by applying force ,
is discussed as well . .
And you have already written the first three sentences of the full article: long flexible polymer macromolecules in a good solvent possess configurational statistics , which is perfectly captured by the model of self - avoiding random walks ( saw ) on a regular lattice @xcite .
this corresponds to the _ regime of polymer coils _ which holds provided that the temperature @xmath3 is above the so - called @xmath4-temperature . in this regime ,
the mean end - to - end distance of an @xmath5-step chain scales as @xmath6 , where @xmath7 is an universal exponent , which depends on space dimension @xmath8 only . with lowering the temperature.
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, the effect of monomer - monomer attraction grows and the polymer radius shrinks . at @xmath9 the effective repulsion due to the volume exclusion constraint
is exactly balanced by attractive interactions . at this particular temperature
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11,807 |
Suppose that you have an abstract for a scientific paper: in this paper , we dynamically select the transmission rate and design wireless network coding to improve the quality of services such as delay for time critical applications . with low transmission rate , and hence longer transmission range , more packets may be encoded together , which increases the coding opportunity .
however , low transmission rate may incur extra transmission delay , which is intolerable for time critical applications .
we design a novel joint rate selection and wireless network coding ( rsnc ) scheme with delay constraint , so as to minimize the total number of packets that miss their deadlines at the destination nodes .
we prove that the proposed problem is np - hard , and propose a novel graph model and transmission metric which consider both the heterogenous transmission rates and the packet deadline constraints during the graph construction . using the graph model ,
we mathematically formulate the problem and design an efficient algorithm to determine the transmission rate and coding strategy for each transmission .
finally , simulation results demonstrate the superiority of the rsnc scheme . .
And you have already written the first three sentences of the full article: with the increase in both wireless channel bandwidth and the computational capability of wireless devices , wireless networks now can be used to support time critical applications such as video streaming or interactive gaming .
such time critical applications require the data content to reach the destination node(s ) in a timely fashion , i.e. , a delay deadline is imposed on packet reception , beyond which the reception becomes useless ( or invalid ) @xcite .
recently , network coding becomes a promising approach to improve wireless network performance @xcite ..
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specifically , the work in @xcite proposed the first network coding based packet forwarding architecture , named _
cope _ , to improve the throughput of wireless networks . with cope
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11,808 |
Suppose that you have an abstract for a scientific paper: we review briefly the motivations for introducing additional group - theoretic data in tensor models , leading to the richer framework of group field theories , themselves a field theory formulation of loop quantum gravity .
we discuss how these data give to the gft amplitudes the structure of lattice gauge theories and simplicial gravity path integrals , and make their quantum geometry manifest .
we focus in particular on the non - commutative flux / algebra representation of these models . .
And you have already written the first three sentences of the full article: the idea of a fully background independent formulation of the microscopic structure of quantum space - time has recently found a tentative realisation in the ( tensorial ) group field theory ( gft ) approach to quantum gravity @xcite .
two main lines of research converge in this approach : tensor models @xcite and loop quantum gravity @xcite .
the first , a higher - dimensional generalisation of the matrix models formulation of 2d quantum gravity , provide the combinatorial backbone and several key mathematical tools , the second suggests the needed algebraic data that allow the definition of a hilbert space structure and of richer , more interesting quantum geometric models for 3d and 4d quantum gravity . in these notes , as in our talk at the workshop , we illustrate briefly how this enrichment of tensor models through the input of loop quantum gravity and spin foam models works , focusing in particular on data and tools from non - commutative geometry , and what it leads to , reviewing some recent results ..
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we thus complement the mostly combinatorial treatment of tensor models and tensorial group field theories provided by prof .
rivasseau at the same workshop @xcite .
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11,809 |
Suppose that you have an abstract for a scientific paper: we discuss the optical and radio early afterglow emission of the reverse shock that crosses a baryonic ejecta as it interacts with the external interstellar medium ( ism ) .
we show that the peak of the optical flash divides the light curve of the reverse shock into two distinctive phases .
the emission after the peak depends weakly on the initial conditions of the ejecta and therefore it can be used as an identifiable signature of a reverse shock emission . on the other hand , the emission before the optical peak is highly sensitive to the initial conditions and therefore can be used to investigate the initial hydrodynamic profile of the ejecta . in particular ,
if the prompt @xmath0-ray emission results from internal shocks , the early reverse shock emission should resemble a smoothed version of the prompt @xmath0-ray light curve . .
And you have already written the first three sentences of the full article: according to the internal - external shocks model the prompt gamma - ray burst ( grb ) is produced by internal shocks within a relativistic flow while the afterglow is produced by external shocks between this flow and the surrounding matter .
the early afterglow appears during the transition from the prompt @xmath0-ray emission to the afterglow . during this transition
the relativistic flow , ejected by the source , interacts directly with the circum burst medium ..
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this interaction can be used to pin down the nature of the relativistic flow ( baryonic or poynting flux ) . in a baryonic
flow the reverse shock ( rs ) that propagates into the ejecta produces both optical and radio emission .
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11,810 |
Suppose that you have an abstract for a scientific paper: mn doped semiconductors are extremely interesting systems due to their novel magnetic properties suitable for the spintronics applications .
it has been shown recently by both theory and experiment that mn doped gan systems have a very high curie temperature compared to that of mn doped gaas systems . to understand the electronic and magnetic properties , we have studied mn doped gan system in detail by a first principles plane wave method .
we show here the effect of varying mn concentration on the electronic and magnetic properties . for dilute mn concentration , @xmath0 states of mn form an impurity band completely separated from the valence band states of the host gan .
this is in contrast to the mn doped gaas system where mn @xmath0 states in the gap lie very close to the valence band edge and hybridizes strongly with the delocalized valence band states . to study the effects of electron correlation
, lsda+u calculations have been performed .
calculated exchange interaction in ( mn , ga)n is short ranged in contrary to that in ( mn , ga)as where the strength of the ferromagnetic coupling between mn spins is not decreased substantially for large mn - mn separation .
also , the exchange interactions are anisotropic in different crystallographic directions due to the presence or absence of connectivity between mn atoms through as bonds . .
And you have already written the first three sentences of the full article: diluted magnetic semiconductors ( dms ) are considered to be potential candidates for present and future technological applications in semiconductor spintronics @xcite . during the last decade ,
there have been numerous experimental and theoretical studies of ii - vi , iii - v and iv - vi dms . among the iii - v dms , mn
doped gaas system has been studied rigorously for the last few years ..
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this system shows a curie temperature ( @xmath1 ) of 110 k for a mn doping concentration of 10 @xmath2 . despite several attempts , @xmath1
could nt be raised beyond 175 k. recently , there have been reports of some room temperature dms .
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11,811 |
Suppose that you have an abstract for a scientific paper: here i summarize constraints on the nature of the dark matter halos of field galaxies that have been obtained from the most recent investigations of ( i ) weak galaxy
galaxy lensing and ( ii ) the dynamics of satellite galaxies in orbit about large host galaxies .
both of these techniques are statistical in their nature ( i.e. , large samples of galaxies are required to obtain a `` signal '' ) , but since they have inherently different selection biases and systematic errors , they are quite complementary to each other . results of work over the last several years on weak lensing and satellite dynamics is revealing a remarkably consistent picture regarding the dark matter halos of bright field galaxies ( @xmath0 ) .
the halos extend to large physical radii ( @xmath1 kpc ) and are flattened in projection on the sky , there is a marked difference in the depths of the potential wells of early type galaxies and late type galaxies , and the velocity dispersion profiles of the halos , @xmath2 , decrease at large projected radii .
all of these are expected to hold true in a cold dark matter universe and , while neither technique can address the possible small scale ( @xmath3 kpc ) conflicts between cold dark matter and observed galaxies , on scales @xmath4 kpc both techniques yield results that are consistent with each other , and with the predictions of cold dark matter .
address = boston university , institute for astrophysical research , 725 commonwealth ave . ,
boston , ma 02215 .
And you have already written the first three sentences of the full article: the existence of dark matter halos surrounding large , bright galaxies is well established ( e.g. , @xcite , @xcite , @xcite , @xcite and references therein ) , and in the standard cold dark matter ( cdm ) paradigm , the halos of large field galaxies are expected to extend to virial radii of @xmath5 kpc to @xmath6 kpc and have masses of @xmath7 ( e.g. , @xcite , @xcite , @xcite ) . until very recently
, however , direct observational constraints on the nature of the dark matter halos of field galaxies have not been especially strong . in particular , it has been challenging to address the question as to whether the halos of observed galaxies are consistent with the halos that one would expect in a cdm universe .
the lack of a keplerian fall off in the rotation curves of the disks of most spiral galaxies ( e.g. , @xcite ) indicates that the dark matter halos extend far beyond the visible radii of the galaxies ..
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therefore , in order to place constraints on the total mass distribution , it is necessary to use tracers of the halo potential that exist at large projected radii ( @xmath8 kpc ) .
two such tracers of the large scale potential are satellite galaxies that are in orbit about isolated host galaxies , and photons emitted by distant galaxies that , on their way to the observer , happen to pass through the potential wells of more nearby galaxies at small impact parameters ( i.e. , gravitational lensing ) .
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11,812 |
Suppose that you have an abstract for a scientific paper: @xmath0-curves were experimentally investigated .
fishtail - effect ( fe ) was observed in mg yba@xmath1cu@xmath2o@xmath3 and yba@xmath1(cu@xmath4ag@xmath5)@xmath2o@xmath3 ( at @xmath6 0.02 ) crystals in a wide temperature range 0.4 @xmath7 0.8 at the orientation of magnetic field @xmath8 .
it was obtained that the influence of bulk pinning on fe is more effective at low temperatures while surface barriers dominates at high temperatures .
the value @xmath9 for ag - doped crystals is larger than for a pure one that due to the presence of additional pinning centers , above all on silver atoms . .
And you have already written the first three sentences of the full article: since the discovery of high - temperature superconductors ( htscs ) , their engineering applications at liquid nitrogen temperatures have drawn much attention .
the yba@xmath1cu@xmath2o@xmath3 ( ybco ) is one of the promising htscs materials for various technical applications .
however , in ceramic materials the critical current density ( @xmath10 ) is , due to the weak link effects , very low , rendering them unsuitable for applications . in order to enhance @xmath10 , the so - called melt - textured growth ( mg ) process.
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@xcite has been developed , which can significantly enhance @xmath10 .
one interesting phenomenon in the mg htscs is the fishtail effect ( fe ) in @xmath10 as well as in isothermal magnetic hysteresis loops ( @xmath11 curves ) @xcite . as for the fe origin
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11,813 |
Suppose that you have an abstract for a scientific paper: we discuss the tunneling spectroscopy at a surface in multi - band systems such as fe - based superconductors with the use of the quasiclassical approach .
we extend the single - band method by matsumoto and shiba [ j. phys .
soc .
jpn . * 64 * , 1703 ( 1995 ) ] into @xmath0-band systems ( @xmath1 ) .
we show that the appearance condition of the zero - bias conductance peak does not depend on details of the pair - potential anisotropy , but it depends on details of the normal state properties in the case of fully - gapped superconductors .
the surface density of states in a two - band superconductor is presented as a simplest application .
the quasiclassical approach enables us to calculate readily the surface - angular dependence of the tunneling spectroscopy . .
And you have already written the first three sentences of the full article: much attention has been focused on novel fe - based superconductors since the recent discovery of superconductivity at the high temperature 26k in lafeaso@xmath2f@xmath3.@xcite many theoretical and experimental studies on fe - based superconductors have been reported for the last year .
it is important to identify the superconducting order parameter to elucidate the mechanism of superconductivity in those high-@xmath4 materials .
a @xmath5-wave pairing symmetry has been theoretically proposed as one of the candidates for the pairing symmetry in fe - pnictide superconductors.@xcite the @xmath5-wave symmetry means that the symmetry of pair potentials on each fermi surface is @xmath6-wave and the relative phase between them is @xmath7 ..
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recently , we showed that a fully - gapped anisotropic @xmath5-wave superconductivity consistently explained experimental observations such as nuclear magnetic relaxation rate and superfluid density .
@xcite a key point to identify the @xmath5-wave symmetry is a detection of the sign change in the order parameters between fermi surfaces .
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11,814 |
Suppose that you have an abstract for a scientific paper: we concern with a special class of binary cellular automata , i.e. , the so - called particle cellular automata ( pca ) in the present paper .
we first propose max - plus expressions to pca of 4 neighbors .
then , by utilizing basic operations of the max - plus algebra and appropriate transformations , pca4 - 1 , 4 - 2 and 4 - 3 are solved exactly and their general solutions are found in terms of max - plus expressions .
finally , we analyze the asymptotic behaviors of general solutions and prove the fundamental diagrams exactly . .
And you have already written the first three sentences of the full article: cellular automaton ( ca ) can be used as discrete mathematical models for a variety of phenomena@xcite .
one remarkable feature for ca being used as a model lies in the fact that the setup is mathematically simple . since both dependent and independent variables are discrete and a set of values which the dependent variable takes is finite , a rule table is more suitable for representing logical expression in a ca model .
thus , ca is free from mathematical conditions such as continuity and differentiability . due to the complete discreteness of ca ,.
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mathematical tools for analyzing its solutions of ca are very different from those for analyzing solutions of other mathematical objects such as differential equation , finite - difference equation and coupled map lattice .
pattern analysis , graph theory and statistical mathematics are often used to analyze ca @xcite . however , in seeking for a general solution starting from arbitrary initial data of a ca , this difference often becomes an obstacle .
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11,815 |
Suppose that you have an abstract for a scientific paper: the atmospheres of cool , helium - rich white dwarfs constitute an exotic and poorly explored physical regime of stellar atmospheres . under physical conditions where the temperature varies from @xmath0 to @xmath1 ,
the density can reach values as large as @xmath2 , and the pressure is as high as @xmath3 , the atmosphere is no longer an ideal gas and must be treated as a dense fluid .
helium atoms become strongly correlated and refraction effects are present .
opacity sources such as @xmath4 free - free absorption must be calculated with a formalism that has never been applied to astrophysical opacities .
these effects have been ignored in previous models of cool white dwarf atmospheres . .
And you have already written the first three sentences of the full article: very cool white dwarfs ( wds ) with @xmath5 are among the oldest objects in our galaxy .
they are of great importance for cosmochronology and for understanding the formation and evolution of the milky way .
our main interest is in the atmospheres of these stars as the link between their physical characteristics and the observables . in this contribution.
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we concentrate on the atmospheres rich in helium . due to the high transparency of helium ( compared to hydrogen ) , our current models predicts for them densities that are typical of liquids , up to @xmath6 . under such extreme conditions ,
the input physics of atmosphere models needs to be reconsidered .
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11,816 |
Suppose that you have an abstract for a scientific paper: employing data on the assessed value of land in 19742007 japan , we exhibit a quasistatically varying log - normal distribution in the middle scale region . in the derivation
, a non - gibrat s law under the detailed quasi - balance is adopted together with two approximations .
the resultant distribution is power - law with the varying exponent in the large scale region and the quasistatic log - normal distribution with the varying standard deviation in the middle scale region . in the distribution ,
not only the change of the exponent but also the change of the standard deviation depends on the parameter of the detailed quasi - balance .
these results are consistently confirmed by the empirical data .
pacs code : 89.65.gh + .
And you have already written the first three sentences of the full article: log - normal distributions are frequently observed not only in natural phenomena but also in social ones . for representative example , the probability density function @xmath0 of personal income or firm size @xmath1 is considered to obey the log - normal distribution @xcite@xcite @xmath2 \label{ln } \end{aligned}\ ] ] in the middle scale region . here
@xmath3 is a mean value and @xmath4 is a variance . a large number of persons or firms are included in the middle scale region .
the study of the distributions is significant . the simplest model which describes the log - normal distribution is the pure multiplicative stochastic process defined by @xmath5 where @xmath6 is a positive random variable . by applying this process iteratively ,.
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we obtain @xmath7 the logarithm of this equation is @xmath8 if @xmath9 is negligible compared to @xmath10 in the limit @xmath11 and @xmath12 @xmath13 are independent probability variables , @xmath10 follows the normal distribution in the limit . as a result , this model leads the stationary log - normal distribution @xmath14 .
( [ msp ] ) means that the distribution of the growth rate @xmath6 does not depend on @xmath15 .
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11,817 |
Suppose that you have an abstract for a scientific paper: we study photon diffusion in a two - dimensional random packing of monodisperse disks as a simple model of granular media and wet foams .
we assume that the intensity reflectance of disks is a constant @xmath0 .
we present an _
analytic _
expression for the transport - mean - free path @xmath1 in terms of the velocity of light in the disks and host medium , radius @xmath2 and packing fraction of the disks , and the intensity reflectance . for the glass beads immersed in the air or water
, we estimate transport - mean - free paths about half the experimental ones . for the air bubbles immersed in the water ,
@xmath3 is a _ linear _ function of @xmath4 , where @xmath5 is the liquid volume fraction of the model wet foam .
this throws new light on the empirical law of vera et .
al [ applied optics * 40 * , 4210 ( 2001 ) ] , and promotes more realistic models . .
And you have already written the first three sentences of the full article: there is a good reason to study wave propagation in turbid or random media : multiply scattered waves can _ probe _ temporal changes in physical systems @xcite .
thus , light transport through fog @xcite , milky liquids , nematic liquid crystals @xcite , granular media@xcite , foams@xcite , and human tissue @xcite ; propagation of elastic waves in the earth s crust @xcite ; acoustic waves in the fluidized or sedimenting suspensions @xcite ; etc . , have attracted much attention . in a turbid medium
, light undergoes many scattering events before leaving the sample , and the transport of light energy is diffusive @xcite ..
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therefore , the photon can be considered as a random walker .
the transport - mean - free path @xmath1 , over which the photon direction becomes randomized , depends on the structural details of the opaque medium .
|
11,818 |
Suppose that you have an abstract for a scientific paper: to compare different forecasting methods on demand series we require an error measure .
many error measures have been proposed , but when demand is intermittent some become inapplicable , some give counter - intuitive results , and there is no agreement on which is best .
we argue that almost all known measures rank forecasters incorrectly on intermittent demand series .
we propose several new error measures with wider applicability , and correct forecaster ranking on several intermittent demand patterns .
we call these `` mean - based '' error measures because they evaluate forecasts against the ( possibly time - dependent ) mean of the underlying stochastic process instead of point demands . .
And you have already written the first three sentences of the full article: inventory management is of great economic importance to industry , but forecasting demand for spare parts is difficult because it is _ intermittent _ : in many time periods the demand is zero .
this type of demand occurs in several industries , for example in aerospace and military inventories from which spare parts such as wings or jet engines are infrequently required .
various methods have been proposed for forecasting , some simple and others statistically sophisticated , but relatively little work has been done on intermittent demand ..
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most work in this area is influenced by that of @xcite , who first separated the forecasting of demand size and inter - demand interval .
a survey of forecasting methods for spare parts is given in @xcite . to choose a good forecasting method we can test the alternatives empirically on demand series to see which gives the smallest error .
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11,819 |
Suppose that you have an abstract for a scientific paper: we formulate the non - linear field theory for a fluctuating counter - ion distribution in the presence of a fixed , arbitrary charge distribution .
the poisson - boltzmann equation is obtained as the saddle - point , and the effects of fluctuations and correlations are included by a loop - wise expansion around this saddle point .
we show that the poisson equation is obeyed at each order in the loop expansion and explicitly give the expansion of the gibbs potential up to two loops .
we then apply our formalism to the case of an impenetrable , charged wall , and obtain the fluctuation corrections to the electrostatic potential and counter - ion density to one - loop order without further approximations .
the relative importance of fluctuation corrections is controlled by a single parameter , which is proportional to the cube of the counter - ion valency and to the surface charge density .
we also calculate effective interactions between charged particles , which reflect counter - ion correlation effects .
pacs .
82.70.@xmath0y - disperse systems .
+ pacs .
61.20.qg - associated liquids .
+ pacs .
82.45.+z - electrochemistry . .
And you have already written the first three sentences of the full article: the behavior of charged , fluctuating systems is an old problem in chemistry and physics and is of importance for very diverse disciplines . in this article
we will be concerned with the distribution of counter ions around charged objects , which is experimentally realized whenever an object with dissociable surface groups is brought in contact with water ( or some other high - dielectric solvent ) . in such a situation
, the counter ions will be attracted to the oppositely charged object , but also repelled from other counter ions ..
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the characteristic feature of charged systems is that the coulomb interaction is long - ranged , which gives these systems very special properties .
since , in general , one counter ion interacts with many different counter ions simultaneously , the mean - field approach is very successful and can be used to describe experiments or simulations quantitatively .
|
11,820 |
Suppose that you have an abstract for a scientific paper: nonequilibrium steady states are investigated in a coupled cavity qed array system which is pumped by a thermal bath and dissipated through cavity loss . in the coherent ( non - zero photon amplitude ) phase , plateau regions appear , where the steady states become unchanged against the variation of the chemical potential of the thermal bath .
the cavity loss plays a crucial role for the plateaus : the plateaus appear only if the cavity loss exists , and the photon leakage current , which is induced by the loss , is essential to the mechanism of the plateaus . _
introduction_.in recent years , much attention has been paid to coupled cavity qed arrays . in these systems , the effective photon - photon interaction in each cavity and photon hopping between cavities lead to rich quantum many - body phenomena of photons @xcite .
for example , in equilibrium states , these systems exhibit quantum phase transitions between the `` incoherent ( or mott insulator ) '' and `` coherent ( or superfluid ) '' phases @xcite .
nonequilibrium states in these systems have been also investigated @xcite .
most of the works have focused on the nonequilibrium effects of the pumping and dissipation on the properties observed in equilibrium states ; e.g. , signatures of the two phases in nonequilibrium states . however
, phenomena genuinely characteristic to nonequilibrium states in the systems remain unexplored .
apart from the coupled cavity qed array , examples of this kind of phenomena are seen in `` nonequilibrium phase transitions , '' such as the pattern formation outside equilibrium @xcite , dissipative structure @xcite , and lasing phenomena @xcite .
these are observed not in equilibrium states but only in nonequilibrium states .
it is important to find such phenomena from the viewpoint that they can be used as test models for nonequilibrium statistical mechanics and thermodynamics . in this paper
, we report that another genuine nonequilibrium phenomenon can occur in a coupled cavity qed array....
And you have already written the first three sentences of the full article: here we investigate the dependence of the first plateau on the cavity loss @xmath3 to obtain data that support the essentiality of the cavity loss for the plateaus .
we denote the chemical potential at the beginning of the first plateau by @xmath93 , which is pointed with the up arrow in fig .
we plot @xmath93 ( circle symbols ) as a function of @xmath3 in fig ..
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[ fig : mub1st ] .
we observe that @xmath93 increases as @xmath3 becomes smaller .
|
11,821 |
Suppose that you have an abstract for a scientific paper: we have made observations with the keck i telescope and hires at a resolution of @xmath045,000 of five nearly identical stars at the turn - off of the metal - rich globular cluster m 71 .
we derive stellar parameters and abundances of several elements . our mean fe abundance , [ fe / h]@xmath1 , is in excellent agreement with previous cluster determinations from both giants and near - turnoff stars .
there is no clear evidence for any star - to - star abundance differences or correlations in our sample .
abundance ratios of the fe - peak elements ( cr , ni ) are similar to fe .
the turn - off stars in m71 have remarkably consistent enhancements of 0.2 - 0.3 dex in [ si / fe ] , [ ca / fe ] and [ ti / fe ] like the red giants .
our [ mg / fe ] ratio is somewhat lower than that suggested by other studies .
we compare our mean abundances for the five m 71 stars with field stars of similar metallicity [ fe / h ] 8 with halo kinematics and 17 with disk kinematics .
the abundances of the alpha - fusion products ( mg , si , ca , ti ) agree with both samples , but seem a closer match to the disk stars .
the mg abundance in m71 is at the lower edge of the disk and halo samples .
the neutron - capture elements , y and ba , are enhanced relative to solar in the m71 turn - off stars . our ratio [ ba / fe ] is similar to that of the halo field stars but a factor of two above that for the disk field stars .
the important [ ba / y ] ratio is significantly lower than m71 giant values ; the pre - cluster material may have been exposed to a higher neutron flux than the disk stars or self - enrichment has occured subsequent to cluster star formation .
the na content of the m71 turn - off stars is remarkably similar to that in the disk field stars , but more than a factor of two higher than the halo field star sample .
we find [ na / fe ] = + 0.14 @xmath20.04 with a spread less than half of that found in the red giants in m71 .
excluding mg , the lack of intracluster @xmath3-element variations ( turn....
And you have already written the first three sentences of the full article: it is important to determine the composition of unevolved stars in globular clusters in order to learn the basic composition of the cluster from stars that have not undergone any mixing with the interior layers .
we include as `` unevolved stars '' both main sequence and turn - off stars .
it is well known that there can be large spreads in the abundance of some elements in the giant stars of a given globular cluster ( e.g. kraft 1994 , sneden et al ..
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most previous high - resolution studies were limited to giant stars , whose atmospheres and interiors are less well modeled than those of dwarf stars .
more extensive studies of the unevolved stars , which have little or no advanced nuclear processing _ in situ _ , are expected to reveal the clusters original composition .
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11,822 |
Suppose that you have an abstract for a scientific paper: we propose a straightforward extension of symbolic transfer entropy to enable the investigation of delayed directional relationships between coupled dynamical systems from time series .
analyzing time series from chaotic model systems , we demonstrate the applicability and limitations of our approach .
our findings obtained from applying our method to infer delayed directed interactions in the human epileptic brain underline the importance of our approach for improving the construction of functional network structures from data .
20cm(3cm,27 cm ) published as phys .
rev .
e * 90 * , 062706 ( 2014 ) .
copyright 2014 by the american physical society . .
And you have already written the first three sentences of the full article: characterizing couplings between interacting systems plays an important role in numerous scientific fields , ranging from physics to the neurosciences @xcite . over the last years
, a large number of linear and nonlinear analysis techniques has been proposed to reveal couplings from passive observations of the systems behavior , e.g. , from time series of certain observables , and thus allow a data - driven quantification of the strength and direction of an interaction @xcite .
knowing interaction properties is important for the construction of functional network structures in diverse scientific fields @xcite . among these techniques ,.
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the information - theoretic concept of transfer entropy @xcite provides a model - free approach to characterizing directed interactions , because it can be viewed as transfers of information .
transfer entropy is related to the concept of granger causality @xcite and to conditional mutual information @xcite , and has widely been used to distinguish the driving and responding elements and to detect asymmetry in the interaction of subsystems in various scientific fields . since its invention , techniques that allow a data - driven estimation of transfer entropy are being steadily improved @xcite . among these improvements
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11,823 |
Suppose that you have an abstract for a scientific paper: a special test electromagnetic field in the spacetime of the higher - dimensional generally rotating nut(a)ds black hole is found .
it is adjusted to the hidden symmetries of the background represented by the principal killing - yano tensor .
such electromagnetic field generalizes the field of charged black hole in four dimensions . in higher dimensions , however , the gravitational back reaction of such a field can not be consistently solved . .
And you have already written the first three sentences of the full article: in recent years people have become interested in higher - dimensional spacetimes with motivation , among others , coming from string theories .
one of the important classes of exact solutions of the einstein equations are the spacetimes representing black holes . in the last years
various generalizations of black hole solutions to the higher - dimensional gravity have been discovered . starting with nonrotating and rotating black holes @xcite and following with the metric describing the rotating black hole with the cosmological constant in five dimensions @xcite ,.
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the generally rotating black hole in arbitrary dimension with the cosmological constant was found in @xcite . in 2006 this solution
was rewritten @xcite in much more convenient coordinates which allowed to add nut parameters and compute the curvature tensors explicitly @xcite .
|
11,824 |
Suppose that you have an abstract for a scientific paper: the s - stars have been suggested to be a brief transitional phase as stars evolve from oxygen - rich m - type stars into carbon stars , through the dredge up of carbon from he - shell burning . as possible transition objects , s - stars might help achieve a deeper understanding of the chemical evolution as a star ascends the agb , as well as shed more light on the mass - loss mechanism .
we have initiated a large survey of 40 s - stars to observe line emission in common molecules such as co , sio , hcn , cs and sis .
detailed radiative transfer modelling of multi - transition co radio line observations towards a sample of 40 s - stars shows that the mass - loss rate distribution of s - stars is consistent with those found for m - type agb stars and carbon stars .
initial results from modelling of the circumstellar sio emission are also presented . .
And you have already written the first three sentences of the full article: the molecular setup and grain types in the circumstellar envelopes ( cses ) of agb stars are to a large extent determined by the c / o - ratio in the photosphere of the central star .
there exists three chemical types : the carbon stars , with c / o@xmath01 , the m - stars , with c / o@xmath11 , and the s - stars , with c / o@xmath21 . the s - stars are believed to be a short transitional phase , as dredge - up of carbon from he - shell burning , changes the spectral type from m - stars to carbon stars .
the agb stars contribute to the chemical evolution of galaxies through their extensive mass loss and an understanding of their circumstellar properties is important in the study of galactic chemistry ..
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the mass - loss characteristics and molecular setup of m- and carbon stars are relatively well - studied .
however , comparatively little attention has been given to the s - stars . in order to improve this situation
|
11,825 |
Suppose that you have an abstract for a scientific paper: security organizations often attempt to disrupt terror or insurgent networks by targeting `` high value targets '' ( hvt s ) .
however , there have been numerous examples that illustrate how such networks are able to quickly re - generate leadership after such an operation . here ,
we introduce the notion of a _ shaping _ operation in which the terrorist network is first targeted for the purpose of reducing its leadership re - generation ability before targeting hvt s .
we look to conduct shaping by maximizing the network - wide degree centrality through node removal .
we formally define this problem and prove solving it is np - complete .
we introduce a mixed integer - linear program that solves this problem exactly as well as a greedy heuristic for more practical use .
we implement the greedy heuristic and found in examining five real - world terrorist networks that removing only @xmath0 of nodes can increase the network - wide centrality between @xmath1 and @xmath2 .
we also show our algorithm can scale to large social networks of @xmath3 nodes and @xmath4 edges on commodity hardware . .
And you have already written the first three sentences of the full article: terrorist and insurgent networks are known for their ability to regenerate leadership after targeted attacks .
for example , the infamous al qaeda in iraq terrorist leader abu musab al - zarqawi was killed on june 8th , 2006 only to be replaced with abu ayyub al - masri about a week later . here ,
we introduce the notion of a _ shaping _ operation in which the terrorist network is first targeted for the purpose of reducing its leadership re - generation ability ..
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such shaping operations would then be followed by normal attacks against high value targets however the network would be less likely to recover due to the initial shaping operations . in this paper , we look to shape such networks by increasing network - wide centrality , first introduced in @xcite . intuitively , this measure provides insight into the criticality of high - degree nodes .
hence , a network with a low network - wide centrality is a more decentralized organization and likely to regenerate leadership . in the shaping operations introduced in this paper
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11,826 |
Suppose that you have an abstract for a scientific paper: we describe a new microscopic approach for analyzing interacting electron systems with local moments or , in principle , any local order parameter .
we specialize attention to the doped mott insulator phase of the hubbard model , where standard weak coupling perturbation methods fail . a rotationally invariant stratonovich
hubbard field is introduced to decouple the static spin components of the interaction at each site .
charge degrees of freedom are then treated by `` slave '' hartree fock in the presence of a spatially varying random spin field .
the effective action reduces to a classical heisenberg model at half filling , insuring that the system has ( i ) finite range order at @xmath0 with an exponentially diverging correlation length and ( ii ) a one electron mott
hubbard gap in the presence of disorder .
away from half filling properties are determined by strongly non
gaussian fluctuations in the amplitude and orientation of the local spin fields .
the saddle point equations of the theory at zero temperature reduce to inhomogeneous hartree
fock , so that disordering of domain walls at finite temperature is in principle included .
we present preliminary small system results for the intermediate and large interaction regimes obtained by monte carlo simulation of random spin field configurations .
# 1 0= -.025em0 - 0 .05em0 - 0 -.025em.0433em0 .
And you have already written the first three sentences of the full article: in this paper we describe a new approach to perturbation theory for systems with local moments or , in principle , any local order parameter .
we begin by summarizing the present status of weak coupling perturbation theories for such systems , with the hubbard model as a primary example .
over the course of the last decade weak coupling perturbation theories have been used extensively to investigate the physics of the hubbard model and its extensions . the simplest perturbative approach to the hubbard model.
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is just hartree fock theory for one body correlation functions .
the conserving approximation implied for two body correlations is then the random phase approximation , or rpa . in the large@xmath1 limit at half filling the static spin response is unstable within hartree fock , and the system exhibits a broken symmetry ground state with infinite
|
11,827 |
Suppose that you have an abstract for a scientific paper: let @xmath0 be a regular riemann surface with a metric which has constant scalar curvature @xmath1 .
we give the asymptotic expansion of the sum of the square norm of the sections of the pluricanonical bundles @xmath2 .
that is , @xmath3 where @xmath4 is an orthonormal basis for @xmath5 for sufficiently large @xmath6 .
[ section ] .
And you have already written the first three sentences of the full article: let @xmath0 be an @xmath7-dimensional compact complex khler manifold with an ample line bundle @xmath8 over @xmath0 .
let @xmath9 be the khler metric on @xmath0 corresponding to the khler form @xmath10 for some positive hermitian @xmath11 metric on @xmath8 .
such a khler metric @xmath9 is called a polarized khler metric ..
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the metric @xmath11 induces a hermitian metric @xmath12 on @xmath13 for all positive integers @xmath6 .
let @xmath4 be an orthonormal basis of the space @xmath14 with respect to the inner product @xmath15 where @xmath16 and @xmath17 is the volume form of @xmath9 .
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11,828 |
Suppose that you have an abstract for a scientific paper: positive signs of the effective @xmath0-factors for free electrons in the conduction band and electrons localized on deep paramagnetic centers have been measured in nitrogen dilute alloy gaas@xmath1n@xmath2 at room temperature .
the @xmath0-factor signs have been determined from an asymmetry in the depolarization of edge photoluminescence in a transverse magnetic field ( hanle effect ) at the oblique incidence of the exciting radiation and oblique - angle detection of the luminescence .
the tilted spin polarization of free electrons is induced under interband absorption of circularly polarized light , and the paramagnetic centers acquire spin polarization because of spin - dependent capture of free spin - polarized electrons by these centers . the measured hanle curve is a superposition of two lines , narrow and broad , with the widths @xmath3 g and @xmath4 g , arising due to the depolarization of localized and free electrons , respectively .
the difference in the linewidths by two orders of magnitude strongly indicates much longer spin lifetime for the paramagnetic centers as compared with that for the free carriers .
the magnitude and direction of the asymmetry in the measured hanle curve have been found to depend on the partial contributions to the recombination radiation from the heavy- and light - hole subbands split by a uniaxial deformation of the gaas@xmath5n@xmath6 film grown on a gaas substrate .
we have extended the theory of optical orientation in order to calculate the excitation spectrum of the photoelectron tilted - spin polarization and the circularly - polarized luminescence spectrum taking into account that , in the strained samples under study , the light - hole subband lies above the heavy - hole one .
the results have further been used to calculate the shape of hanle curve as a function of the excitation and registration energies as well as the incidence and detection angles and to compare the theory with experiment . .
And you have already written the first three sentences of the full article: dilute iii - n - v alloys with the group - v cations partially substituted by nitrogen , e.g. , gaasn and ingaasn , have recently attracted particular attention owing to a number of their unusual properties .
thus , an increase of nitrogen content in the alloy is accompanied by an anomalous reduction of the fundamental band gap , by more than 0.1ev per 1% of n as the nitrogen concentration increases from zero up to 4% @xcite , as well as by a drastic increase of the electron effective mass and enhanced nonparabolicity of the @xmath7 conduction band @xcite ( for reviews , see also @xcite ) .
these specific properties are related to the n - substitution - induced resonant electronic states within the conduction band continuum and an anticrossing of the localized nitrogen states with the extended conduction states of the semiconductor matrix @xcite ..
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qualitatively , the available experimental data are consistent with the simple phenomenological band anticrossing ( bac ) model which takes into account the anticrossing hybridization only with the levels of isolated ( single ) nitrogen atoms @xcite . as a result ,
the two hybridized conduction bands , @xmath8 and @xmath9 , are formed .
|
11,829 |
Suppose that you have an abstract for a scientific paper: the dense @xmath0 loop model is a statistical physics model with connections to the quantum xxz spin chain , alternating sign matrices , the six - vertex model and critical bond percolation on the square lattice .
when cylindrical boundary conditions are imposed , the model possesses a commuting family of transfer matrices .
the original proof of the commutation property is algebraic and is based on the yang - baxter equation . in this paper
we give a new proof of this fact using a direct combinatorial bijection . .
And you have already written the first three sentences of the full article: in the * dense @xmath0 loop model * , a square lattice is tiled with the following two kinds of square tiles known as * plaquettes * , denoted symbolically by @xmath1 and @xmath2 :.
Please generate the next two sentences of the article
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11,830 |
Suppose that you have an abstract for a scientific paper: we investigate the magicity of the isotopes @xmath0ca and @xmath1ca , that was recently confirmed by two experimental measurements , and relate it to like particle and neutron proton tensor effects within a mean field description . by analyzing ca isotopes ,
we show that the like particle tensor contribution induces shell effects that render these nuclei more magic than they would be predicted by neglecting it .
in particular , such induced shell effects are stronger in the nucleus @xmath0ca and the single particle gaps are increased in both isotopes due to the tensor force . by studying @xmath2 and @xmath3 isotones , neutron
proton tensor effects may be isolated and their role analyzed .
it is shown that neutron
proton tensor effects lead to increasing @xmath2 and @xmath3 gaps , when going along isotonic chains , from @xmath4fe to @xmath0ca , and from @xmath5fe to @xmath1ca , respectively .
the mean field calculations are perfomed by employing one skyrme parameter set , that was introduced in a previous work by fitting the tensor parameters together with the spin orbit strength .
the signs and the values of the tensor strengths are thus checked within this specific application .
the obtained results indicate that the employed parameter set , even if generated with a partial adjustment of the parameters of the force , leads to the correct shell behavior and provides , in particular , a description of the magicity of @xmath0ca and @xmath1ca within a pure mean field picture with the effective two body skyrme interaction
. 0.5 cm .
And you have already written the first three sentences of the full article: we recently introduced tensor parametrizations for the phenomenological effective forces skyrme and gogny , by taking into account a tensor force of zero and finite range , respectively @xcite .
the tensor parameters were adjusted on top of already existing skyrme and gogny parametrizations , by employing a three - step fitting procedure inspired by refs .
@xcite and by modifying also , simultaneously , the spin orbit strength ..
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this work was done as an exploratory study to identify the correct signs and regions for the values of the tensor parameters , and can be viewed as a preparatory study for a global fit of all the parameters , especially in the gogny case , where much less work has been done including the tensor force . in the present work ,
we employ one of the skyrme parametrizations introduced in ref .
|
11,831 |
Suppose that you have an abstract for a scientific paper: we compare the theoretical frameworks and the phenomenological applications of the factorization approaches to exclusive @xmath0 meson decays , which include qcd - improved factorization , perturbative qcd , and soft - collinear effective theory .
recent progress on two - body nonleptonic @xmath0 meson decays made in these approaches are reviewed . .
And you have already written the first three sentences of the full article: `` factorizations `` in the naive factorization assumption and in factorization theorem have very different meanings .
the former refers to the factorization of a process into subprocesses .
for example , a @xmath0 meson decay amplitude @xmath1 is written , in the factorization assumption , as the product @xcite , @xmath2 where the meson decay constant @xmath3 arises from the production of the meson @xmath4 from the vacuum , and the form factor @xmath5 is associated with the @xmath6 transition ..
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the latter refers to the factorization of perturbative and nonperturbative dynamics in a qcd process . according to factorization theorem ,
the above amplitude is expressed as @xmath7 where @xmath8 denotes the convolution over parton kinematic variables , the hard kernel @xmath9 absorbs perturbative dynamics , and the @xmath0 ( @xmath10 , @xmath4 ) meson distribution amplitude @xmath11 ( @xmath12 ) absorbs nonperturbative dynamics in the @xmath13 decay . a piece of contribution to @xmath0 meson decays is factorizable , if it respects either eq .
|
11,832 |
Suppose that you have an abstract for a scientific paper: we show that dark matter substructure in galaxy - scale halos perturbs the time delays between images in strong gravitational lens systems .
the variance of the effect depends on the subhalo mass function , scaling as the product of the substructure mass fraction and a characteristic mass of subhalos ( namely @xmath0 ) .
time delay perturbations therefore complement gravitational lens flux ratio anomalies and astrometric perturbations by measuring a different moment of the subhalo mass function . unlike flux ratio anomalies ,
`` time delay millilensing '' is unaffected by dust extinction or stellar microlensing in the lens galaxy .
furthermore , we show that time delay _ ratios _ are immune to the radial profile degeneracy that usually plagues lens modeling .
we lay out a mathematical theory of time delay perturbations and find it to be tractable and attractive .
we predict that in `` cusp '' lenses with close triplets of images , substructure may change the arrival - time order of the images ( compared with smooth models ) .
we discuss the possibility that this effect has already been observed in rx j1131@xmath11231 . .
And you have already written the first three sentences of the full article: the cold dark matter ( cdm ) paradigm predicts that 5%10% of each galaxy s mass is bound up in subhalos left over from the hierarchical formation process . in the local group ,
the predicted number of dark matter subhalos significantly exceeds the observed number of dwarf galaxy satellites ( e.g. , * ? ? ?
* ; * ? ? ?.
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* ; * ? ? ?
* ; * ? ? ?
|
11,833 |
Suppose that you have an abstract for a scientific paper: we investigate the effect of disorder on the transfer of quantum states across a one - dimensional lattice with varying levels of control resources . we find that the application of properly designed control signals , even when applied only to the two ends of the lattice , allows perfect state transfer up to disorder strengths that would not allow a generic quantum state to propagate the length of the lattice . at sufficiently large disorder strengths ,
however , the local control signals fail to send the quantum state from one end of the system to the other end .
our results shed light on the interplay between disorder and controlled transport in one - dimensional systems . .
And you have already written the first three sentences of the full article: disorder has a profound effect on transport in quantum systems .
one of the most striking manifestations of this statement is anderson localization @xcite , where an increasing amount of disorder can lead to a phase transition from a metallic to an insulating state , even in the seemingly simple case of noninteracting particles .
this phenomenon , first predicted over fifty years ago , has been observed directly in a number of physical systems in recent years @xcite ..
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another subject where there has been extensive work in recent years is the problem of quantum state transfer along one - dimensional lattices or spin chains @xcite . in this problem
the goal is to transport an unknown quantum state from one end of a spin chain to the opposite end of the chain .
|
11,834 |
Suppose that you have an abstract for a scientific paper: we perform a bfkl - nll analysis of forward jet production at hera which leads to a good description of data over the full kinematical domain .
we also predict the azimuthal angle dependence of mueller - navelet jet production at the tevatron and the lhc using the bfkl nll formalism . .
And you have already written the first three sentences of the full article: r0.5 following the successful bfkl @xcite parametrisation of the forward - jet cross - section @xmath0 at leading order ( lo ) at hera @xcite , it is possible to perform a similar study using next - to - leading ( nll ) resummed bfkl kernels .
this method can be used for forward jet production at hera in particular , provided one takes into account the proper symmetric _ two - scale _ feature of the forward - jet problem , whose scales are in this case @xmath1 for the lepton vertex and @xmath2 for the jet vertex . in this short report , we will only discuss the phenomelogical aspects and all detailed calculations can be found in ref .
@xcite for forward jets at hera and in ref ..
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@xcite for mueller navelet jets at the tevatron and the lhc .
we perform a saddle point approximation of the bfkl nll formalism and compare it with the h1 forward jet cross section measurements .
|
11,835 |
Suppose that you have an abstract for a scientific paper: we introduce singular ricci flows , which are ricci flow spacetimes subject to certain asymptotic conditions .
we consider the behavior of ricci flow with surgery starting from a fixed initial compact riemannian @xmath0-manifold , as the surgery parameter varies .
we prove that the flow with surgery subconverges to a singular ricci flow as the surgery parameter tends to zero .
we establish a number of geometric and analytical properties of singular ricci flows . .
And you have already written the first three sentences of the full article: it has been a long - standing problem in geometric analysis to find a good notion of a ricci flow with singularities .
the motivation comes from the fact that a ricci flow with a smooth initial condition can develop singularities without blowing up everywhere ; hence one would like to continue the flow beyond the singular time .
the presence of singularities in ricci flow is one instance of the widespread phenomenon of singularities in pde , which is often handled by developing appropriate notions of generalized solutions ..
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for example , in the case of the minimal surface equation , one has minimizing or stationary integral currents @xcite , while in the case of mean curvature flow one has brakke flows @xcite and level set flows @xcite .
generalized solutions provide a framework for studying issues such as existence , uniqueness and partial regularity . one highly successful way to deal with ricci flow singularities was by surgery , as developed by hamilton @xcite and perelman @xcite .
|
11,836 |
Suppose that you have an abstract for a scientific paper: the neutralino sector of the u(1 ) extended susy is presented and some collider and cosmology - related phenomenology discussed . .
And you have already written the first three sentences of the full article: supersymmetry ( susy ) has been considered to be the best candidate beyond the standard model ( sm ) from a viewpoint of both the hierarchy problem and the gauge coupling unification .
recent astrophysical observations showing the existence of a substantial amount of non - relativistic and non - baryonic dark matter seem to make susy even more promising .
the lightest susy particle ( lsp ) of r - parity conserving models , in most cases the lightest neutralino , can serve as a good candidate for dark matter ( dm ) . the parameter space of the constrained mssm , however , is strongly restricted by the requirement of matching the precise measurement of the dm relic density as measured by the wmap ..
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the mssm also suffers from a naturalness problem ( the so - called @xmath0 problem ) : why the dimensionful parameter @xmath0 of the supersymmetric higgs mass term @xmath1 has to be of ew scale .
this problem can be solved in the next - to - mssm ( nmssm ) by promoting the @xmath0 parameter to a new singlet superfield @xmath2 coupled to higgs doublets , @xmath3 @xcite .
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11,837 |
Suppose that you have an abstract for a scientific paper: a new alternate method for evaluating linear response theory is formally developed , and results are presented .
this method involves the time - evolution of the system using tdhf and is constructed directly on top of a static hartree - fock calculation . by fourier transforming the time - dependent result the response function and the total probability amplitude are extracted .
this method allows for a coherent description of static properties of nuclei , such as binding energies and deformations , while also providing a method for calculating collective modes and reaction rates .
a full 3-d cartesian basis - spline collocation representation is used with several skyrme interactions .
sample results are presented for the giant multipole resonances of @xmath0o , @xmath1ca , and @xmath2s and compared to other calculations .
= 10000 = 10000 = 10000 .
And you have already written the first three sentences of the full article: typically , linear response theory equations are derived by adding a specific time - dependent perturbing function to the hamiltonian , which is usually harmonic in time , resulting in a set of rpa - like equations .
these equations are then solved , for a given energy , using several methods ( see for example refs .
@xcite ) to give the response of the system to a specific collective excitation mode . in this paper , a new alternate method.
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is presented to calculate response theory .
a specific time - dependent perturbing external piece is added to the static hamiltonian to give a time - dependent total hamiltonian , @xmath3 .
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11,838 |
Suppose that you have an abstract for a scientific paper: we study the impact of the measurements of three sets of observables on the parameter space of the constrained minimal supersymmetric standard model ( cmssm ) , its slightly general variant , the non - universal scalar model ( nusm ) , and some selected benchmark points of the 19-parameter phenomenological mssm ( pmssm ) : ( @xmath0 ) the direct measurement of the higgs boson mass @xmath1 gev at the cern large hadron collider ( lhc ) ; ( @xmath2 ) @xmath3 boson decay width in the @xmath4 channel normalized to its hadronic width ( @xmath5 ) , and the forward - backward asymmetry on the @xmath3-peak in the same channel @xmath6 ; and ( @xmath7 ) several @xmath8-physics observables , along with @xmath9 of muon .
in addition , there are constraints from non - observation of superparticles from direct searches at the lhc . in view of the recently re - estimated standard model ( sm ) value of @xmath5 with
improved higher order corrections , the measured value of @xmath5 has a 1.2@xmath10 discrepancy with its sm value , while the corresponding discrepancy in @xmath11 is 2.5@xmath10 .
mssm contributions from light superpartners improve the agreement of @xmath5 but worsen that of @xmath11 .
we project this ( @xmath5-@xmath12 ) tension _ vis - - vis _ the constraints arising from other observables in the parameter space of cmssm and nusm .
we also consider a few well - motivated pmssm benchmark points and show that pmssm does not fare any better than the sm .
sinp / tnp/2013/07 * minimal supersymmetry confronts @xmath13 , @xmath14 and @xmath15 * + gautam bhattacharyya@xmath16 , anirban kundu@xmath17 and tirtha sankar ray@xmath18 + .
And you have already written the first three sentences of the full article: it is still premature to conclude that the recently discovered scalar particle with a mass of around 125 gev at the lhc @xcite is the standard model ( sm ) higgs boson . among other possibilities
, it can very well be the lightest neutral higgs boson of the minimal supersymmetric standard model ( mssm ) , which is the most advocated beyond the sm scenario .
be that as it may , stringent constraints apply on the supersymmetric parameter space , which are , at least for the minimal versions , more severe than those placed from the non - observation of superparticles from direct searches at the colliders . in spite of several advantages that supersymmetry offers , like the solution of the big hierarchy problem and even the provision of a cold dark matter candidate.
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, we can not escape the following pertinent question : does supersymmetry even partially ease the existing tension between the sm predictions and the experimental measurements for some specific observables ?
the tension with @xmath9 of muon , namely , @xmath19 , i.e. a 3.5@xmath10 deviation of the measured value @xcite from its sm expectation @xcite , is an old intriguing one .
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11,839 |
Suppose that you have an abstract for a scientific paper: different applications of crystalline whispering gallery mode resonators call for different properties of the resonator host material . we report on our recent study of resonators made out of sapphire , diamond , and quartz crystals and discuss possible applications of these resonators .
in particular , we demonstrate kerr frequency comb generation in sapphire microresonators . .
And you have already written the first three sentences of the full article: an efficient technique of measurement of attenuation of transparent optical crystals involves fabrication of monolithic resonators out of the materials and measurement of their intrinsic quality ( @xmath0 ) factors .
the attenuation of light in the resonator mode , @xmath1 , is related to the quality factor of a circular monolithic resonator as @xmath2 , where @xmath3 is the wavelength of measurement , and @xmath4 is the refractive index of the material at this wavelength .
the value of coefficient @xmath1 is determined by both absorption and scattering in the bulk material and on the surface of the resonator ..
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hence , @xmath1 gives a reasonable approximation of the bulk absorption if other loss mechanisms are made negligible . whispering gallery mode ( wgm )
resonators are solid state cavities that confine light in small geometrical volumes for long periods of time @xcite .
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11,840 |
Suppose that you have an abstract for a scientific paper: we propose that @xmath0-rays in blazars can be produced during encounters of relativistic blobs of plasma with radiation field produced by luminous stars within ( or close to ) the jet .
the blob is expected to contain relativistic electrons which comptonize stellar radiation to the gev - tev energies .
produced @xmath0-rays can initiate the inverse compton @xmath1 pair cascade in the stellar radiation .
we propose that such a scenario can be responsible for the appearance of the so - called orphan @xmath0-ray flares .
we show that the relativistic blob / luminous star collision model can explain the appearance of the extreme orphan @xmath0-ray flare observed in the gev and sub - tev energy range from the flat spectrum radio quasar pks1222 + 21 .
[ firstpage ] galaxies : active galaxies : individual ( pks1222 + 21 ) stars : massive radiation mechanisms : non - thermal gamma - rays : general .
And you have already written the first three sentences of the full article: it is widely accepted that the non - thermal radiation in blazars is produced within a relativistic jet directed towards the observer .
however , the mechanism of energization of particles and their radiation is not fully understood .
recently , simple scenarios exploiting collisions of compact objects with the jet plasma reached some attention ..
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in fact , many different types of compact objects ( e.g. stars , clouds or even globular clusters , fragments of supernova remnants or pulsar wind nebulae ) can be immersed within the jet , forming an obstacle for the jet plasma .
it has been proposed that particles , accelerated on the shocks appearing as a result of collisions of the jet plasma with stellar winds , can produce high energy @xmath0-rays ( see e.g. @xcite ) . in this work ,
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11,841 |
Suppose that you have an abstract for a scientific paper: we present temperature ( @xmath0 ) and baryonic chemical potential ( @xmath1 ) dependence of higher order fluctuations and correlation between conserved charges in excluded volume hadron resonance gas ( evhrg ) model .
products of moments , such as ratio of variance to mean ( @xmath2 , product of skewness and standard deviation ( @xmath3 ) , product of kurtosis and variance ( @xmath4 ) , for net - proton , net - kaon and net - charge have been evaluated on the phenomenologically determined freeze - out curve .
further , products of moments for net - proton and net - charge have been compared with the experimental data measured by star experiment .
the dependence of the model result on the hadronic radius parameter has also been discussed . .
And you have already written the first three sentences of the full article: one of the primary goals of heavy - ion collision experiments at ultra - relativistic energies is to study the thermodynamic aspects of strongly interacting matter at high temperature and density . while at low density and high temperature , present experimental as well as lattice data seem to indicate a smooth cross over @xcite from hadronic to a quark gluon matter , at high density and low temperature the system is expected to have a first order transition @xcite .
so the first order phase transition at high densities and low temperature should end at a critical end point ( cep ) - a second order phase transition point - as one moves towards high temperature and low density region , in the phase diagram of strongly interacting matter @xcite .
several experimental programmes have been launched to study the phase transition of strongly interacting matter . at present , relativistic heavy - ion collider ( rhic ) at brookhaven national laboratory and the large hadron collider ( lhc ) at cern are providing us plethora of data . in near future the facility for.
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anti - proton and ion research ( fair ) at gsi will also provide us a large amount of information .
the low temperature and high @xmath1 region will be studied in beam energy scan ( bes ) programme of rhic and the compressed baryonic matter ( cbm ) programme at fair .
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11,842 |
Suppose that you have an abstract for a scientific paper: quantum molecular dynamic simulations are introduced to study the dynamical , electrical , and optical properties of carbon dioxide under dynamic compressions .
the principal hugoniot derived from the calculated equation of states is demonstrated to be well accordant with experimental results .
molecular dissociation and recombination are investigated through pair correlation functions , and decomposition of carbon dioxide is found to be between 40 and 50 gpa along the hugoniot , where nonmetal - metal transition is observed .
in addition , the optical properties of shock compressed carbon dioxide are also theoretically predicted along the hugoniot . .
And you have already written the first three sentences of the full article: knowledge of pressure - induced transformations for materials under extreme conditions , which requires accurate understandings of the thermophysical properties into new and complex region , has gained much interest in a large number of scientific and technological domains @xcite .
carbon dioxide ( co@xmath0 ) is one kind of the most important molecules in planetary science and chemical ( or explosive ) process .
for instance , the magnetic fields and evolution of planets are closely related to the equation of states ( eos ) and electrical properties of planetary interiors @xcite , which are composed of species containing c , h , n , o , etc . ;.
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chemical reactions of carbonaceous molecules ( such as co@xmath0 , co ) , nitrogen ( n@xmath0 ) , oxygen ( o@xmath0 ) and their mixture at high densities and temperatures are focused due to their presence in reacted chemical explosives @xcite . from these aspects ,
clearly , an accurate description of thermodynamical properties of co@xmath0 at high pressures and temperatures is fundamental and proves itself to be indispensabe for developing realistic models of planetary interiors and reacted explosives .
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11,843 |
Suppose that you have an abstract for a scientific paper: intergalactic medium ( igm ) metal absorption lines observed in @xmath0 spectra offer the opportunity to probe early feedback processes , the nature of enriching sources , and the topology of reionization .
we run high - resolution cosmological simulations including galactic outflows to study the observability and physical properties of 5 ions ( @xmath1 , @xmath2 , @xmath3 , @xmath4 , @xmath5 ) in absorption between @xmath6 .
we apply three cases for ionization conditions : fully neutral , fully reionized , and a patchy model based on the flux from the nearest galaxy .
we find that our simulations can broadly fit available @xmath7 igm metal - line data , although all observations can not be accommodated with a single ionization condition .
variations in @xmath3 absorbers among sight lines seen by becker et al .
( 2006 ) suggest significant neutral igm patches down to @xmath8 .
strong @xmath2 absorbers at @xmath9 may be the result of ionization by the galaxy responsible for that enrichment , although the identification of the neighboring galaxy will have to wait to confirm this .
our outflows have typical speeds of @xmath10 km / s and mass loading factors of @xmath11 . such high mass loading is critical for enriching the igm to the observed levels while sufficiently curtailing early star formation to match the observed rest - frame uv luminosity function .
the volume filling factor of metals increases during this epoch , but only reaches @xmath12 for @xmath13 by @xmath14 .
detectable absorbers generally trace inhomogeneously - distributed metals residing outside of galactic halos .
@xmath2 is an ideal tracer of igm metals at @xmath7 , with dropping global ionization fractions to either higher or lower redshifts .
this results in a strongly increasing global @xmath2 mass density ( @xmath15 ) from @xmath6 , in contrast to its relative constancy from @xmath16 .
our simulations do not support widespread early igm enrichment from e.g. population iii stars , as this would overpredict the....
And you have already written the first three sentences of the full article: the universe undergoes its last major transition at @xmath8 as the first stars and early galaxies finish the process of reionizing the previously neutral intergalactic medium ( igm ) .
observations have only recently cracked the @xmath21 gyr universe with the discovery of galaxies tracing early star formation @xcite , quasars providing ionizing photons @xcite , and the complete absorption by the igm of all lyman-@xmath22 photons , i.e. the @xcite trough , in @xmath23 quasar spectra @xcite .
a new type of high-@xmath17 observation is the recent detection of metal - line absorbers in the most distant quasar spectra , probing the nucleosynthetic products of early star formation ..
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* hereafter bsrs ) surveyed 9 @xmath24 quasars and found 4 @xmath3 systems in the most distant object in their sample , j1148 + 5251 .
@xcite , @xcite , & @xcite discovered multiple @xmath2 absorbers at similar redshifts ( @xmath9 ) . despite the metals presumably being formed within galaxies ,
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11,844 |
Suppose that you have an abstract for a scientific paper: multiparticle production at high energies is described in terms of color strings stretched between the projectile and target . as the string density increases ,
overlap in the transverse plane leads to cluster formation . at some critical density
a macroscopic cluster appears , spanning the entire system .
this marks the percolation phase transition .
data from @xmath0 = 200 gev p+p , d+au and au+au collisions at rhic has been analyzed using the star detector to obtain the percolation density parameter , @xmath1 .
the particle p@xmath2 spectrum from 200 gev p+p data is parameterized using a power law .
values of the fit parameters are used in the d+au and au+au analysis . for 200 gev au+au collisions , the value of @xmath1 is found to lie above the critical percolation threshold , while for other collision systems and energies , it is below the critical value .
this supports the idea of string percolation , which at high enough string density is a possible mechanism to explore the hadronic phase transition to a quark - gluon plasma . .
And you have already written the first three sentences of the full article: it is postulated that in the collision of two nuclei at high - energy , color strings are formed between projectile and target partons .
these color strings decay into additional strings via @xmath3 production , and ultimately hadronize to produce the observed hadrons.@xcite in the collision process , it is possible for partons from different nucleons to begin overlapping in the plane transverse to the direction of travel of the colliding nuclei .
this overlap probability increases with increasing energy and atomic number of the colliding nuclei.@xcite it is this overlap that leads to cluster formation in the transverse plane , similar to the disk model of 2-d percolation theory.@xcite at a critical cluster density , a cluster will form that spans the entire system ..
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this is referred to as the maximal cluster and marks the onset of the percolation threshold .
the quantity @xmath1 , the percolation density parameter , can be used to describe overall cluster density .
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11,845 |
Suppose that you have an abstract for a scientific paper: the production of dielectrons in reactions involving @xmath0 mesons and pions is studied .
we compare results obtained with different phenomenological lagrangians that have been used in connection with hadronic matter and finite nuclei .
we insist on the necessity for those interactions to satisfy known empirical properties of the strong interaction .
large off - shell effects in dielectron production are found and some consequences for the interpretation of heavy ion data are outlined .
we also compare with results obtained using experimentally - extracted spectral functions . .
And you have already written the first three sentences of the full article: the field of heavy ion collisions is a very active one , straddling high energy and nuclear physics . at the upper energy limit of this flourishing area of research
, the goal is to eventually produce and study a new state of matter in the laboratory : the quark - gluon plasma ( qgp ) .
that strongly interacting matter in conditions of extreme energy densities undergoes a phase transition is in fact a prediction of qcd @xcite . to confirm whether the phase transition indeed occurs in relativistic heavy ion collisions and.
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that the qgp is formed , one needs a clear signal as a signature for the qgp .
many approaches have been suggested to elucidate the existence of this elusive state of matter , but unfortunately no single measurement can yet be singled - out as a `` smoking gun '' candidate .
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11,846 |
Suppose that you have an abstract for a scientific paper: we use density functional theory to determine the equilibrium shape of graphene flakes , through the calculation of the edge orientation dependence of the edge energy and edge stress of graphene nanoribbons .
the edge energy is a nearly linear function of edge orientation angle ; increasing from the armchair orientation to the zigzag orientation .
reconstruction of the zigzag edge lowers its energy to less than that of the armchair edge .
the edge stress for all edge orientations is compressive , however , reconstruction of the zigzag edge reduces this edge stress to near zero .
hydrogen adsorption is favorable for all edge orientations ; dramatically lowering all edge energies and all edge stresses .
it also removes the reconstruction of the zigzag edge . using the new edge energy data , we determine the equilibrium shape of a graphene sheet ( with unreconstructed edges ) to be hexagonal with straight armchair edges in the presence and absence of hydrogen . however , zigzag edge reconstruction produces graphene flakes with a six - fold symmetry , but with rounded edges .
this shape is dominated by near zigzag edges .
the compressive edge stresses will lead to edge buckling ( out - of - the - plane of the graphene sheet ) for all edge orientations , in the absence of hydrogen . exposing
the graphene flake to hydrogen dramatically decreases the buckling amplitude . .
And you have already written the first three sentences of the full article: graphene , a one - atom thick single sheet of @xmath0-bonded carbon atoms in a honeycomb lattice , is a zero - gap semiconductor ( semi - metal ) that exhibits extraordinarily high electron mobility and shows considerable promise for applications in electronic and optical devices , high sensitivity gas detection , ultracapacitors and biodevices@xcite .
graphene can be separated from bulk graphene using a peeling technique known as mechanical exfoliation@xcite .
lithography techniques@xcite have recently been applied to fabricate patterned graphene nanoribbons ( gnr ) with widths below 100 ; such gnr were used to produce graphene field effect transistors with on - off ratios as high as @xmath1.
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. there has been concerted efforts to investigate the stability of graphene sheets @xcite .
since applications of graphene necessarily employ sheets of finite extent , it is also of interest to inquire as to the equilibrium shape of such finite sheets or flakes .
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11,847 |
Suppose that you have an abstract for a scientific paper: we report the excitation energy dependence of specific heat ( @xmath0 ) of hadronic matter at freeze - out in au+au and cu+cu collisions at the relativistic heavy ion collider energies by analyzing the published data on event - by - event mean transverse momentum ( @xmath1 ) distributions .
the @xmath1 distributions in finite @xmath2 ranges are converted to distributions of effective temperatures , and dynamical fluctuations in temperature are extracted by subtracting widths of the corresponding mixed event distributions . the heat capacity per particle at the kinetic freeze - out surface
is presented as a function of collision energy , which shows a sharp rise in @xmath0 below @xmath3 = 62.4 gev .
we employ the hadron resonance gas ( hrg ) model to estimate @xmath0 at the chemical and kinetic freeze - out surfaces .
the experimental results are compared to the hrg and other theoretical model calculations .
hrg results show good agreement with data .
model predictions for @xmath0 at the large hadron collider energy are presented . .
And you have already written the first three sentences of the full article: the major goal of colliding heavy - ions at the relativistic heavy ion collider ( rhic ) at brookhaven national laboratory and the large hadron collider ( lhc ) at cern is to study matter at extreme conditions of temperature and energy densities , where quarks and gluons , rather than mesons and baryons , define the relevant degrees of freedom @xcite .
this new phase of matter , the quark - gluon plasma ( qgp ) , is governed by the principles of quantum chromodynamics ( qcd ) and is the result of a phase transition from the normal nuclear matter @xcite .
experiments at rhic and lhc are on the quest to unearth the nature of the qcd phase transition and to get a glimpse of how matter behaves at extreme conditions ..
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the beam energy scan ( bes ) program at rhic has been initiated to explore the onset of phase transition by scanning the collision energy over a larger range and to locate the critical point in the qcd phase diagram .
the thermodynamic state of the qcd matter can be specified by the temperature @xmath4 and the chemical potentials @xmath5 , @xmath6 and @xmath7 corresponding to the conserved charges of qcd , namely baryon number ( @xmath8 ) , strangeness ( @xmath9 ) , and electric charge ( @xmath10 ) , respectively .
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11,848 |
Suppose that you have an abstract for a scientific paper: a discrete model for the sintering of polydisperse , inhomogeneous arrays of cylinders is presented with empirical contact force - laws , taking into account plastic deformations , cohesion , temperature dependence ( melting ) , and long - time effects .
samples are prepared under constant isotropic load , and are sintered for different sintering times . increasing both external load and
sintering time leads to a stronger , stiffer sample after cooling down .
the material behavior is interpreted from both microscopic and macroscopic points of view . among the interesting results
is the observation , that the coordination number , even though it has the tendency to increase , sometimes slightly decreases , whereas the density continuously increases during sintering this is interpreted as an indicator of reorganization effects in the packing .
another result of this study is the finding , that strongly attractive contacts occur during cool - down of the sample and leave a sintered block of material with almost equally strong attractive and repulsive contact forces . .
And you have already written the first three sentences of the full article: in mechanics and physics exist two ways to describe and model a particulate , inhomogeneous material like powder , ceramics or concrete .
the first approach is based on continuum theory and relies on empirical assumptions about the macroscopic material behavior @xcite . for a summary of recent progress on the macroscopic modeling of sintering processes
see refs ..
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@xcite and the references therein .
this ansatz is complemented by a `` microscopic '' description of the material on the particle or grain level where the particles and their interactions are modeled one by one @xcite .
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11,849 |
Suppose that you have an abstract for a scientific paper: we review models where r parity is broken , either spontaneously or explicitly . in this last case
we consider the situation where r parity is broken via bilinear terms in the superpotential .
we show that although at tree level only one neutrino gets mass , at one loop level all three neutrinos became massive .
we study the conditions under which bimaximal mixing can be achieved and show that the masses can be in the correct ranges needed for solving the atmospheric and solar neutrino problems . .
And you have already written the first three sentences of the full article: in the past most discussions of supersymmetric ( susy)@xcite phenomenology assumed r parity ( @xmath0 ) conservation where , r_p=(-1)^2j + 3b + l this implies that susy particles are pair produced , every susy particle decays into another susy particle and that there is a _
lsp _ that it is stable .
but this is just an _ ad hoc _ assumption without a deep justification . in this talk.
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we will review how @xmath0 can be broken , either spontaneously or explicitly , and discuss the most important features of these models @xcite .
we will also describe recent results @xcite on one loop generated masses and mixings in the context of a model that is a minimal extension of the minimal extension of the mssm
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11,850 |
Suppose that you have an abstract for a scientific paper: this paper investigates a lossy source coding problem in which two decoders can access their side - information respectively .
the correlated sources are a product of two component correlated sources , and we exclusively investigate the case such that each component is degraded .
we show the rate - distortion function for that case , and give the following observations .
when the components are degraded in matched order , the rate distortion function of the product sources is equal to the sum of the component - wise rate distortion functions . on the otherhand ,
the former is strictly smaller than the latter when the component sources are degraded in mismatched order . .
And you have already written the first three sentences of the full article: the source coding problem for correlated sources has been regarded as an important research area in information theory , and various types of coding problems were studied so far ( e.g. @xcite ) . in particular , our focus in this paper is the lossy coding problem posed by heegard and berger @xcite . in the problem , there are one encoder and multiple decoders ( see fig .
[ fig : scenario ] ) . in this paper , we only treat the case with two decoders . the encoder send an encoded version of principal source @xmath0 , and decoders reproduce the principal source within prescribed distortion levels by the help of side - information @xmath1 and @xmath2 respectively . in this
setting , heegard and berger showed an upper bound on the rate distortion function ..
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they also showed that the upper bound is tight if the sources are degraded , i.e. , @xmath0 , @xmath1 , and @xmath2 form a markov chain in this order .
although some researchers investigated variants of heegard and berger
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11,851 |
Suppose that you have an abstract for a scientific paper: using a bistatic radar echo sounding ( res ) system developed for calibration of the rice particle astrophysics experiment at the south pole , we have studied radio frequency ( rf ) reflections off the bedrock .
the total propagation time of @xmath0ns - duration , vertically ( @xmath1 ) broadcast radio signals , as a function of polarization orientation in the horizontal plane , provides a direct probe of the geometry - dependence of the ice permittivity to a depth of 2.8 km .
we observe clear birefringent asymmetries along @xmath1 in the lowest half of the ice sheet , at a fractional level @xmath00.3% .
this result is in contrast to expectations based on measurements at dome fuji , for which birefringence was observed in the upper 1.5 km of the ice sheet .
this effect , combined with the increased radio frequency attenuation expected near the bedrock , renders the lower half thickness of south polar ice less favorable than the upper half of the ice sheet in terms of its ultra - high energy neutrino detection potential .
radio frequency birefringence in south polar ice and implications for neutrino reconstruction i. kravchenko + _ university of nebraska , department of physics and astronomy , lincoln , ne , 68588 - 0111 _ + d. besson , a. ramos , j. remmers + _ university of kansas , dept .
of physics and astronomy , lawrence , ks , 66045 - 7582 _ + .
And you have already written the first three sentences of the full article: the response of ice as a function of polarization ( `` birefringence '' ) is characterized by differences in either wavespeed or absorption along linear ( generally orthogonal ) axes . over a km - scale pathlength , in the absence of any preferred in - ice direction , one might expect any time propagation asymmetry at the single - crystal level to be macroscopically mitigated by the randomness of the corresponding single - crystal orientation . in such a case , over a total pathlength @xmath2 consisting of @xmath3 unit steps , each characterized by an asymmetry @xmath4 , the average propagation time along each polarization axis should have a gaussian distribution , centered at @xmath5 , with width @xmath6 .
the asymmetry distribution would therefore be a gaussian of width @xmath7 , centered at zero . for 1% birefringence ( @xmath8 ) , @xmath2=1000 m , and step sizes corresponding to typical grain sizes ( @xmath9 m , or n=@xmath10 ) , we expect @xmath110.1 ns . if , however , bulk flow of the ice sheet results in a preferred in - ice direction much longer than typical grain sizes , the propagation time asymmetry can be @xmath12(10 ns ) .
efforts are underway to use the antarctic ice sheet as an ultra - high energy neutrino target@xcite ..
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neutrino - ice collisions result in the production of charged particles which emanate from the interaction point with velocities approaching the speed - of - light _ in vacuo _ : @xmath13 . in a medium with index - of - refraction @xmath14 , detection of the resulting cherenkov radiation in either the near - uv ( tev - scale neutrinos ) or radio wavelength regime ( pev - scale neutrinos ) by a suite of sensors can be used to reconstruct the kinematics of the initial neutrino , provided the absorption and refraction of the original electromagnetic signal due to the intervening ice can be reliably estimated .
the rice experiment@xcite demonstrated the feasibility of the radio - detection approach over the last decade .
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11,852 |
Suppose that you have an abstract for a scientific paper: in order to explore the possible existence of the exotic @xmath0 state , we have constructed the tetraquark interpolating operators systematically . as a byproduct
, we notice the @xmath1 tetraquark operators without derivatives do not exist .
the special lorentz structure of the @xmath0 currents forbids the four - quark type of corrections to the spectral density .
now the gluon condensates are the dominant power corrections .
none of the seven interpolating currents supports a resonant signal .
therefore we conclude that the exotic @xmath0 state does not exist below 2 gev , which is consistent with the current experimental observations . .
And you have already written the first three sentences of the full article: most of the experimentally observed hadrons can be interpreted as @xmath2/@xmath3 states and accommodated in the quark model @xcite . up to
now there has accumulated some evidence of the exotic state with @xmath4 @xcite .
such a quantum number is not accessible for a pair of quark and anti - quark ..
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it is sometimes labelled as an exotic hybrid meson with the particle contents @xmath5 .
recently we have investigated the @xmath6 state using the tetraquark currents @xcite .
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11,853 |
Suppose that you have an abstract for a scientific paper: some applications of the elementary kaon photoproduction process are discussed : the investigation of missing resonances in the @xmath0 channel , the role of the @xmath1 state in the @xmath2 channel , and the calculation of the gerasimov - drell - hearn sum rule . for the latter , we present an extension of our previous study to higher energies . .
And you have already written the first three sentences of the full article: the electromagnetic production of kaons provides an important source of information on hadronic physics with strangeness . due to the rather weak coupling at the electromagnetic vertex ,
the reaction operator is quite simple and , therefore , the use a of single channel analysis may be quite sufficient to describe the process . this process can be used to simultaneously study kaon - hyperon - nucleon coupling constants , isospin symmetry , hadronic form factors , baryon and meson resonances , and contributions of kaon - hyperon final states to the magnetic moment of the nucleon . in this report
we will focus only on the two last topics ..
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for a detailed discussion of the elementary operator we refer to ref.@xcite .
the background part of the operator consists of the standard born terms along with the @xmath3(892 ) and @xmath4(1270 ) vector meson poles in the @xmath5-channel .
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11,854 |
Suppose that you have an abstract for a scientific paper: laser - assisted photoemission from a solid is considered within a numerically exactly solvable one - dimensional model of a crystal .
the effect of the inelastic scattering and of the finite duration of the pump pulse on the photoelectron dynamics is elucidated .
the phenomenological result that the photoexcited wave packet moves with the group velocity @xmath0 and traverses on average the distance equal to the mean free path is found to hold for energies far from the spectral gaps of the final state band structure . on the contrary , close to a spectral gap the photoelectron
is found to move during the excitation by the pump pulse with a velocity higher than the group velocity . .
And you have already written the first three sentences of the full article: transport properties of electron wave packets underlie the functioning of electronic devices and are an important factor in photoemission spectroscopies and electron diffraction techniques . in a solid , as opposed to a single atom , special role is played by inelastic scattering giving rise to a limited electron lifetime and mean free path .
the inelastic scattering is phenomenologically described as electron absorption @xcite , and its implications for stationary processes are well understood @xcite .
a much less studied question is how the wave packet evolves and propagates on a time scale comparable to its lifetime ..
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experimental access to such ultrafast processes is given by modern time - resolved photoelectron spectroscopies , in particular by the streaking method @xcite , in which a subfemtosecond time resolution is achieved by mapping time to energy using a strong laser field : the electron wave packet created by an ultrashort pulse of extreme ultraviolet radiation ( xuv ) is accelerated by the superimposed laser field , and the energy by which its spectrum shifts up or down depends on the electron release time @xmath1 relative to the temporal profile of the laser field @xmath2 .
various models have been developed that treated the problem by the time - dependent schrdinger equation ( tdse ) @xcite or by applying a classical model @xcite .
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11,855 |
Suppose that you have an abstract for a scientific paper: a formulation of bit - string models of language evolution , based on differential equations for the population speaking each language , is introduced and preliminarily studied .
connections with replicator dynamics and diffusion processes are pointed out .
the stability of the dominance state , where most of the population speaks a single language , is analyzed within a mean - field - like approximation , while the homogeneous state , where the population is evenly distributed among languages , can be exactly studied .
this analysis discloses the existence of a bistability region , where dominance coexists with homogeneity as possible asymptotic states
. numerical resolution of the differential system validates these findings . .
And you have already written the first three sentences of the full article: the dynamics of language has recently been identified as a rich field for interdisciplinary application of statistical techniques traditionally associated with mathematics and physics .
a host of analytical and numerical models have been proposed , aimed at reproducing more or less quantitatively several aspects of language as a dynamical sociocultural entity.@xcite among them , models of language evolution focus on the joint processes of mutation of linguistic features and of language acquisition , switching , and adoption by human populations.@xcite bit - string models of language evolution , prototyped by schulze s model,@xcite conceive that a language is completely characterized by a sequence of dichotomic properties .
each of them represents , for instance , whether the language in question possesses certain grammatical property or not ..
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the sequence is naturally represented as a string of binary variables ( bits ) , whose length is the number of yes / no questions which fully identify a language .
emphasis in the study of bit - string language models has been put on agent - based numerical simulations,@xcite addressing possible explanations for the distribution of population among languages and the abundance of language families .
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11,856 |
Suppose that you have an abstract for a scientific paper: we study electron transport through a quantum dot , connected to non - magnetic leads , in a magnetic field . a super - poissonian electron noise due to the effects of both interacting localized states and dynamic channel blockade
is found when the coulomb blockade is partially lifted .
this is sharp contrast to the sub - poissonian shot noise found in the previous studies for a large bias voltage , where the coulomb blockade is completely lifted .
moreover , we show that the super - poissonian shot noise can be suppressed by applying an electron spin resonance ( esr ) driving field . for a sufficiently strong esr driving field strength ,
the super - poissonian shot noise will change to be sub - poissonian . .
And you have already written the first three sentences of the full article: shot noise , i.e. , current fluctuations due to the discrete nature of electrons , describes the correlation in electron transport through mesoscopic systems , such as quantum dots ( qds ) or molecular devices .
recently , shot noise measurements have provided additional information that is not available in conventional conductance measurements ( for reviews , see refs .
@xcite and @xcite ) ..
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in contrast to poissonian noise often observed in classical transport , quantum transport of electrons is usually described by binomial statistics @xcite , as has been used to explain the suppression of noise in noninteracting conductors @xcite . for quantum transport in many mesoscopic systems , the coulomb repulsion allows an electron to enter a region only after the departure of another electron .
this effect induces a negative electron correlation and , therefore , leads to a sub - poissonian shot noise @xcite . instead of coulomb blockade , an electron blockade due to the pauli exclusion principle also has a similar effect @xcite .
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11,857 |
Suppose that you have an abstract for a scientific paper: we present a computational method to quantitatively describe the linear - response conductance of nanoscale devices in the kondo regime .
this method relies on a projection scheme to extract an anderson impurity model from the results of density functional theory and non - equilibrium green s functions calculations .
the anderson impurity model is then solved by continuous time quantum monte carlo .
the developed formalism allows us to separate the different contributions to the transport , including coherent or non - coherent transport channels , and also the quantum interference between impurity and background transmission .
we apply the method to a scanning tunneling microscope setup for the 1,3,5-triphenyl-6-oxoverdazyl ( tov ) stable radical molecule adsorbed on gold .
the tov molecule has one unpaired electron , which when brought in contact with metal electrodes behaves like a prototypical single anderson impurity .
we evaluate the kondo temperature , the finite temperature spectral function and transport properties , finding good agreement with published experimental results . .
And you have already written the first three sentences of the full article: in recent years , much research effort has been dedicated to study the electronic transport through magnetic molecules and single atoms in order to combine molecular electronics with spintronics@xcite .
experiments and theoretical works have demonstrated that molecular and atomic spin states can be inferred and sometimes switched through an electrical current@xcite . among the many interesting phenomena arising in devices comprising magnetic molecules
, there is the kondo effect@xcite ..
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below the so called kondo temperature , @xmath0 , characteristic of each system , the coupling between the electrons from the electrodes and the spin of the molecule promotes the formation of a many - body state with a fully or partially quenched magnetic moment .
this results in a new resonant transport channel at the electrodes fermi level . to date
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11,858 |
Suppose that you have an abstract for a scientific paper: i comment on progress of lattice qcd techniques and calculations .
recent results on pentaquark masses as well as of the spectrum of excited baryons are summarizned and interpreted .
the present state of calculations of quantities related to the nucleon structure and of electromagnetic transition form factors is surveyed . .
And you have already written the first three sentences of the full article: in the past two years several narrow hadronic resonances have been discovered : new bottomonium and charmonium states , the @xmath0 and at least two new @xmath1 mesons . it is more than twenty years ago that new states with widths @xmath2 mev have been seen last , in the @xmath3 system .
this is an exciting situation as only a rather small number of discovered hadrons , including most notably quarkonia , the hydrogen of qcd , are narrow .
what makes this new era of hadron spectroscopy even more interesting is that many of these previously overlooked states appear to require more qcd than is allowed within simple quark - model @xmath4 mesons or @xmath5 baryons : at least some of the new states constitute the anti - thesis to the `` hydrogen of qcd '' ..
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if confirmed in a high statistics experiment , the @xmath6 pentaquark baryon and possibly other exotic baryons will add even more to this excitement .
lattice qcd is ideally positioned to compute the spectrum of reasonably stable hadrons as well as of non - perturbative properties relating to their internal structure .
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11,859 |
Suppose that you have an abstract for a scientific paper: let @xmath0 be a graph property .
a graph @xmath1 is said to be _ locally _ @xmath0 ( _ closed locally _
@xmath2 ) if the subgraph induced by the open neighbourhood ( closed neighbourhood , respectively ) of every vertex in @xmath1 has property @xmath0 .
the _ clustering coefficient _ of a vertex is the proportion of pairs of its neighbours that are themselves neighbours .
the _ minimum clustering coefficient _ of @xmath1 is the smallest clustering coefficient among all vertices of @xmath1 .
let @xmath3 be a subgraph of a graph @xmath1 and let @xmath4 .
we say that @xmath3 is a _ strongly induced subgraph _ of @xmath1 with _ attachment set _
@xmath5 , if @xmath3 is an induced subgraph of @xmath1 and the vertices of @xmath6 are not incident with edges that are not in @xmath3 .
a graph @xmath1 is _ fully cycle extendable _ if every vertex of @xmath1 lies in a triangle and for every nonhamiltonian cycle @xmath7 of @xmath1 , there is a cycle of length @xmath8 that contains the vertices of @xmath7 .
a complete characterization , of those locally connected graphs with minimum clustering coefficient 1/2 and maximum degree at most @xmath9 that are fully cycle extendable , is given in terms of forbidden strongly induced subgraphs ( with specified attachment sets ) .
moreover , it is shown that all locally connected graphs with @xmath10 and sufficiently large minimum clustering coefficient are weakly pancylic , thereby proving ryjek s conjecture for this class of graphs .
+ _ keywords _ : minimum clustering coefficient ; locally connected ; strongly induced subgraphs ; fully - cycle extendable ; ryjek s conjecture + _ ams subject classification _ : 05c38 .
And you have already written the first three sentences of the full article: the evolution of the internet and the resulting large communication , information and social networks has significantly impacted recent advances in graph theory .
the _ clustering coefficient _ of a user in a social network is the proportion of pairs of its friends that are themselves friends .
mean clustering coefficient _ for the network is the average clustering coefficient taken over all users ..
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this concept was introduced by watts and strogatz @xcite to determine whether a given network is a ` small world ' network .
it was reported in ugander et .
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11,860 |
Suppose that you have an abstract for a scientific paper: time series prediction covers a vast field of every - day statistical applications in medical , environmental and economic domains . in this paper
we develop nonparametric prediction strategies based on the combination of a set of `` experts '' and show the universal consistency of these strategies under a minimum of conditions .
we perform an in - depth analysis of real - world data sets and show that these nonparametric strategies are more flexible , faster and generally outperform arma methods in terms of normalized cumulative prediction error .
+ _ index terms _ time series , sequential prediction , universal consistency , kernel estimation , nearest neighbor estimation , generalized linear estimates .
nonparametric sequential prediction of time series grard biau @xmath0 , kevin bleakley @xmath1 , + lszl gyrfi @xmath2 and gyrgy ottucsk @xmath2 @xmath3 lsta & lpma + universit pierre et marie curie
paris vi + bote 158 , 175 rue du chevaleret + 75013 paris , france + + @xmath1 institut de mathmatiques et de modlisation de montpellier + umr cnrs 5149 , equipe de probabilits et statistique + universit montpellier ii , cc 051 + place eugne bataillon , 34095 montpellier cedex 5 , france + + @xmath2 department of computer science and information theory + budapest university of technology and economics + h-1117 magyar tudsok krt .
2 , budapest , hungary + + .
And you have already written the first three sentences of the full article: the problem of time series analysis and prediction has a long and rich history , probably dating back to the pioneering work of yule in 1927 @xcite .
the application scope is vast , as time series modeling is routinely employed across the entire and diverse range of applied statistics , including problems in genetics , medical diagnoses , air pollution forecasting , machine condition monitoring , financial investments , marketing and econometrics .
most of the research activity until the 1970s was concerned with parametric approaches to the problem whereby a simple , usually linear model is fitted to the data ( for a comprehensive account we refer the reader to the monograph of brockwell and davies @xcite ) ..
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while many appealing mathematical properties of the parametric paradigm have been established , it has become clear over the years that the limitations of the approach may be rather severe , essentially due to overly rigid constraints which are imposed on the processes .
one of the more promising solutions to overcome this problem has been the extension of classic nonparametric methods to the time series framework ( see for example gyrfi , hrdle , sarda and vieu @xcite and bosq @xcite for a review and references ) .
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11,861 |
Suppose that you have an abstract for a scientific paper: using resolved stellar photometry measured from archival _ hst _ imaging , we generate color - magnitude diagrams of the stars within 50 pc of the locations of historic core - collapse supernovae that took place in galaxies within 8 mpc .
we fit these color - magnitude distributions with stellar evolution models to determine the best - fit age distribution of the young population .
we then translate these age distributions into probability distributions for the progenitor mass of each sne .
the measurements are anchored by the main - sequence stars surrounding the event , making them less sensitive to assumptions about binarity , post - main - sequence evolution , or circumstellar dust .
we demonstrate that , in cases where the literature contains masses that have been measured from direct imaging , our measurements are consistent with ( but less precise than ) these measurements . using this technique ,
we constrain the progenitor masses of 17 historic sne , 11 of which have no previous estimates from direct imaging .
our measurements still allow the possibility that all sne progenitor masses are @xmath020 m@xmath1 .
however , the large uncertainties for the highest - mass progenitors also allow the possibility of no upper - mass cutoff . .
And you have already written the first three sentences of the full article: a fundamental question of stellar evolution theory is which stars end their lives as supernovae .
current theory for isolated massive stars makes two basic predictions for sne . for one , the zero - age - main - sequence mass ( ) and mass - loss history control whether a sn occurs , and secondly , for single stars there is a clear mapping between and the type of sn @xcite .
in particular , the lower masses explode with their hydrogen envelopes intact ( e.g. ii - p , ii - l , iin ) , and the most massive stars lose much of their envelopes and explode as hydrogen deficient sne ( e.g. iib , ib / c ) ..
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however , given the complexity of the underlying physics , especially binary evolution , winds , and episodic eruptions , it is unclear whether nature obeys the same well - delineated mass - dependence .
in fact , the relatively high observed rates of h - deficient sne @xcite and low upper limits on progenitor masses of type ibc sne @xcite imply that binary evolution may figure prominently in producing the h - deficient sne .
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11,862 |
Suppose that you have an abstract for a scientific paper: we present a long - term spectral monitoring of the unique double pulsar binary psr j0737 - 3039 corresponding to two `` large programs '' performed by xmm - newton in 2006 and 2011 .
spectral variability of pulsar emission in soft x - rays is not evident over 5 years , despite the significant relativistic spin precession in the considered time span ( @xmath0 ) .
we provide , for the first time , evidence of hard x - ray emission from the system in the @xmath1 kev energy band .
the standard spectral analysis was coupled to the energy dependent spatial analysis to confirm this excess , most likely ascribed to iron line emission .
the fe k@xmath2 emission line at @xmath3 kev was previously unheard - of in non - accreting binary systems and could testify to the presence of a relic disk that survived the supernova explosions that terminated the lives of the double pulsar s stellar progenitors .
the existence of a relic disk in this system reinforces speculation about the presence of similar structures around other peculiar classes of isolated neutron stars . .
And you have already written the first three sentences of the full article: fourteen years after its discovery , the double pulsar psr j0737 - 3039 is still studied extensively .
this system is composed of two neutron stars : an old , fast , mildly recycled 22.7 ms pulsar ( hereafter referred to as pulsar a ; @xcite ) and a younger and much slower pulsar with a period of 2.77 s ( hereafter pulsar b ; @xcite ) .
the compact objects orbit each other in a very tight orbit in only 2.4 hr , with mean orbital velocities of about 1 million km / h ( see e.g. * ? ? ?.
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* for a review ) .
psr j0737 - 3039 represents the most compact relativistic system and the only binary system in which both neutron stars have been detected as radio pulsars .
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11,863 |
Suppose that you have an abstract for a scientific paper: we present precise constraints on the normalization of the power spectrum of mass fluctuations in the nearby universe , @xmath0 , as a function of the mean local matter density , @xmath1 . using the observed local x - ray luminosity function of galaxy clusters from the extended bcs and reflex studies , a mass - luminosity relation determined from chandra and rosat x - ray data and weak gravitational lensing observations , and the mass function predicted by the hubble volume simulations of evrard
, we obtain @xmath2 , with @xmath3 at 68 per cent confidence .
the degeneracy between @xmath0 and @xmath1 can be broken using chandra measurements of the x - ray gas mass fractions in dynamically relaxed clusters . using this information and including gaussian priors on the mean baryon density of the universe and the hubble constant , we obtain @xmath4 and @xmath5 , for an assumed flat @xmath6cdm cosmology ( marginalized 68 per cent confidence limits ) .
our results are in good agreement with some recent studies based on the local x - ray temperature function of clusters , the redshift evolution of the x - ray luminosity and temperature functions of clusters , early results from the sloan digitized sky survey , the most recent results from studies of cosmic shear , and combined analyses of the 2df galaxy redshift survey and cosmic microwave background anisotropies . # 1to 0pt#1 = " 2218 # 1 # 1 to size # 1 to size = cmr10 scaled2 = cmbx10 scaled2 = cmti10 scaled2 ps . cosmological parameters x - rays : galaxies : clusters gravitational lensing large - scale structure of the universe x - rays : galaxies : clusters .
And you have already written the first three sentences of the full article: the x - ray luminosity function of galaxy clusters in the nearby universe provides a powerful cosmological probe .
the observed luminosity function , @xmath7 , can be combined with a relation linking the observed x - ray luminosity and mass , and the mass function , @xmath8 , predicted by simulations , to obtain tight constraints on the combination of cosmological parameters @xmath1 and @xmath0 , where @xmath1 is the mean matter density of the local universe and @xmath0 is the root - mean - square ( rms ) variation of the density field smoothed by a top hat window function of size 8@xmath9mpc .
observationally , the keys to such studies are precise determinations of the local x - ray luminosity function of clusters and the relation linking the observed x - ray luminosities and total masses ..
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x - ray selection currently offers the best way to identify massive galaxy clusters , and the local x - ray luminosity function has now been precisely determined by the bcs ( ebeling 1997 ; ebeling 2000 ) and reflex ( bhringer 2002 ) studies .
the flux - limited bcs and reflex samples , which are based on data from the rosat all - sky survey ( rass ; trmper 1993 ) , together include @xmath10 clusters and cover approximately two thirds of the sky .
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11,864 |
Suppose that you have an abstract for a scientific paper: a class of energy - transport equations without electric field under mixed dirichlet - neumann boundary conditions is analyzed .
the system of degenerate and strongly coupled parabolic equations for the particle density and temperature arises in semiconductor device theory .
the global - in - time existence of weak nonnegative solutions is shown .
the proof consists of a variable transformation and a semi - discretization in time such that the discretized system becomes elliptic and semilinear .
positive approximate solutions are obtained by stampacchia truncation arguments and a new cut - off test function .
nonlogarithmic entropy inequalities yield gradient estimates which allow for the limit of vanishing time step sizes . exploiting the entropy inequality ,
the long - time convergence of the weak solutions to the constant steady state is proved . because of the lack of appropriate convex sobolev inequalities to estimate the entropy dissipation , only an algebraic decay rate is obtained .
numerical experiments indicate that the decay rate is typically exponential . .
And you have already written the first three sentences of the full article: in this paper , we prove the global well - posedness of the energy - transport equations @xmath0 where @xmath1 , @xmath2 , and @xmath3 with @xmath4 is a bounded domain .
this system describes the evolution of a fluid of particles with density @xmath5 and temperature @xmath6 .
the parameter @xmath7 is the relaxation time , which is the typical time of the system to relax to the thermal equilibrium state of constant temperature ..
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the system arises in the modeling of semiconductor devices in which the elastic electron - phonon scattering is dominant .
the above model is a simplification for vanishing electric fields .
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11,865 |
Suppose that you have an abstract for a scientific paper: in this paper we find different types of black holes for the born - infeld extended new massive gravity .
our solutions include ( un)charged warped @xmath0 black holes for four and six derivative expanded action .
we also look at the black holes in unexpanded bi action . in each case
we calculate the entropy , angular momentum and mass of the black holes .
we also find the central charges for the cft duals .
ahmad ghodsi and davood mahdavian yekta + + .
And you have already written the first three sentences of the full article: the black hole solutions of three dimensional gravity have been investigated during recent years .
the first black hole solutions , known as the btz black holes , were found in @xcite .
these solutions were found in the presence of a negative cosmological constant . adding the higher derivative terms to the einstein - hilbert action in the presence of a cosmological constant changes the solutions and their asymptotic behaviors and their physical properties ..
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the topological massive gravity ( tmg ) describes propagation of the massive gravitons around the flat , de sitter or anti de sitter background metrics .
this theory is constructed by adding a parity - violating chern - simons term to the einstein - hilbert action @xcite .
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11,866 |
Suppose that you have an abstract for a scientific paper: surface sensitive synchrotron x - ray scattering studies were performed to obtain the distribution of monovalent ions next to a highly charged interface .
a lipid phosphate ( dihexadecyl hydrogen - phosphate ) was spread as a monolayer at the air - water interface to control surface charge density . using anomalous reflectivity off and at the @xmath0 cs@xmath1 resonance ,
we provide spatial counterion ( cs@xmath1 ) distributions next to the negatively charged interfaces .
five decades in bulk concentrations are investigated , demonstrating that the interfacial distribution is strongly dependent on bulk concentration .
we show that this is due to the strong binding constant of hydronium h@xmath2o@xmath1 to the phosphate group , leading to proton transfer back to the phosphate group and to a reduced surface charge .
the increase of cs@xmath3 concentration modifies the contact value potential , thereby causing proton release .
this process effectively modifies surface charge density and enables exploration of ion distributions as a function of effective surface charge - density .
the experimentally obtained ion distributions are compared to distributions calculated by poisson - boltzmann theory accounting for the variation of surface charge density due to proton release and binding .
we also discuss the accuracy of our experimental results in discriminating among possible deviations from poisson - boltzmann theory . .
And you have already written the first three sentences of the full article: the theoretical determination of ion distributions in aqueous solutions was initiated almost a century ago by guoy @xcite and chapman @xcite , who applied the poisson - boltzmann ( pb ) theory to calculate the spatial distribution of monovalent ions near a uniformly charged interface .
ever since their seminal work , the topic remains central in statistical mechanics , physical chemistry , and biophysics@xcite .
the original pb theory is a mean field theory with some simplified assumptions such as , point like particles and uniform surface charge density . to account for the finite ionic radius , stern introduced phenomenologically a layer of ions at the charged interface with a different dielectric constant , the stern layer @xcite ..
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the effect of excess salt concentration and the resulting screening was extended by debye - hckel @xcite .
grahame generalized the gouy - chapman theory to multivalent ions @xcite .
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11,867 |
Suppose that you have an abstract for a scientific paper: we investigate the influence of dissipation on one and two qubit rotations in coupled semiconductor quantum dots , using a ( pseudo ) spin boson model with adiabatically varying parameters . for weak dissipation ,
we solve a master equation , compare with direct perturbation theory , and derive an expression for the ` fidelity loss ' during a simple operation that adiabatically moves an electron between two coupled dots .
we discuss the possibility of visualizing coherent quantum oscillations in electron ` pump ' currents , combining quantum adiabaticity and coulomb blockade . in two qubit spin swap operations where the role of intermediate charge states has been discussed recently , we apply our formalism to calculate the fidelity loss due to charge tunneling between two dots . .
And you have already written the first three sentences of the full article: the control of quantum superpositions in coupled electronic systems has been suggested as a possible way to realize quantum logic gates in semiconductor structures .
an example are coupled quantum dots @xcite , where coulomb interactions between electrons can be exploited @xcite to define very small effective hilbert spaces such as that of two tunnel - splitted ground states , separated by a large energy gap from the remaining many - particle states@xcite . if parameters of the hamiltonian ( like the tunnel - coupling between dots ) are slowly changed as a function of time , adiabatic control of the state vector @xcite , swap operations @xcite , and the controlled transfer from an initial to a final state @xcite become possible .
in addition , by coupling such a system to external electronic reservoirs , one can pump electrons through the system in a controlled , adiabatic manner which in principle can serve as a ` read out ' of the state vector in form of an electric current . in the simplest case.
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, this can be achieved through a simultaneous variation of two parameters as a function of time .
both adiabatic control of rotations or swaps , and coherent pumping of electrons evidentally are very sensitive to decoherence .
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11,868 |
Suppose that you have an abstract for a scientific paper: we detect stars from the hipparcos and tycho catalogues in the field of view of observations with the rosat hri of three globular clusters .
we use the positions of these stars to reduce the systematic error in the positions of x - ray sources in the clusters to @xmath0 for @xmath1cen and ngc6752 , and @xmath2 for ngc6397 .
we detect three x - ray sources in the core of @xmath1cen , and four in the core of ngc6752 ; the data for the center of ngc6397 may be fitted with five or six sources . outside the cores , but within the half - mass radius of the clusters , we detect two sources in @xmath1cen , one in ngc6397 and two in ngc6752 ; these may or may not be cluster members .
a rosat hri observation of liller1 does not detect a low - luminosity source , at a limit below a detection with asca .
we discuss the nature of the low - luminosity x - ray sources in globular clusters in the light of these new results . .
And you have already written the first three sentences of the full article: globular clusters contain many x - ray sources at lower luminosities , @xmath3ergs@xmath4 .
these sources were first discovered with the einstein satellite ( hertz & grindlay 1983 ) , and many more were found with rosat ( for a compilation , see johnston & verbunt 1996 ) .
the nature of these low - luminosity sources is the subject of debate , because various types of objects can emit x - rays at such luminosities , such as soft x - ray transients in quiescence , cataclysmic variables , rs cvn binaries , and recycled neutron stars ( see e.g. fig ..
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8 in verbunt et al .
the most compelling identification of a dim x - ray source with an object observed at other wavelengths is the recycled radio pulsar in m28 : the x - ray flux varies on the pulse period ( danner et al .
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11,869 |
Suppose that you have an abstract for a scientific paper: the purpose of this paper is to introduce and study some basic concepts of quantitative rectifiability in the first heisenberg group @xmath0 . in particular
, we aim to demonstrate that new phenomena arise compared to the euclidean theory , founded by g. david and s. semmes in the 90 s .
the theory in @xmath0 has an apparent connection to certain nonlinear pdes , which do not play a role with similar questions in @xmath1 .
our main object of study are the _ intrinsic lipschitz graphs _ in @xmath0 , introduced by b. franchi , r. serapioni and f. serra cassano in 2006 .
we claim that these @xmath2-dimensional sets in @xmath0 , if any , deserve to be called quantitatively @xmath2-rectifiable .
our main result is that the intrinsic lipschitz graphs satisfy a _
weak geometric lemma _ with respect to _ vertical @xmath3-numbers_. conversely , extending a result of david and semmes from @xmath4 , we prove that a @xmath2-ahlfors - david regular subset in @xmath0 , which satisfies the weak geometric lemma and has _ big vertical projections _
, necessarily has _
big pieces of intrinsic lipschitz graphs_. .
And you have already written the first three sentences of the full article: _ rectifiability _ is a fundamental concept in geometric measure theory .
rectifiable sets extend the class of surfaces considered in classical differential geometry ; while admitting a few edges and sharp corners , they are still smooth enough to support a rich theory of local analysis . however , for certain question of more global nature the boundedness of singular integrals being the main example
the notion of rectifiability is too qualitative . in a series of influential papers around the year 1990 , @xcite.
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, g. david and s. semmes developed an extensive theory of _ quantitative rectifiability _ in euclidean spaces .
one of their main objectives was to find geometric criteria to characterize the @xmath5-dimensional subsets of @xmath6 , @xmath7 , on which `` nice '' singular integral operators ( sio ) are @xmath8-bounded . here ,
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11,870 |
Suppose that you have an abstract for a scientific paper: we present a unified approach to goodness - of - fit testing in @xmath0 and on lower - dimensional manifolds embedded in @xmath0 based on sums of powers of weighted volumes of @xmath1-th nearest neighbor spheres .
we prove asymptotic normality of a class of test statistics under the null hypothesis and under fixed alternatives . under such alternatives , scaled versions of the test statistics converge to the @xmath2-entropy between probability distributions .
a simulation study shows that the procedures are serious competitors to established goodness - of - fit tests . .
And you have already written the first three sentences of the full article: nearest neighbor methods have been successfully applied in a variety of fields , such as classification ( see @xcite ) , density and regression function estimation ( see @xcite , @xcite ) , and multivariate two - sample testing ( see , e.g. , @xcite , @xcite , and @xcite ) .
moreover , nearest neighbor methods have also been employed in the context of testing the goodness - of - fit of given data with a distributional model ( see @xcite , @xcite and @xcite ) .
this paper is devoted to a class of universally consistent goodness - of - fit tests based on nearest neighbors ..
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these tests can be applied not only to test for uniformity on a compact domain in @xmath0 , but also to test for a specified density on a @xmath3-dimensional manifold embedded in @xmath0 , where @xmath4 . here
, prominent special cases involve testing for uniformity on a circle or on a sphere . to be specific , let @xmath5 denote a @xmath6 @xmath3-dimensional manifold embedded in @xmath7 , where @xmath8 @xmath5 is endowed with the subset topology and is a closed subset of @xmath7 .
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11,871 |
Suppose that you have an abstract for a scientific paper: in this paper , we develop a new method for finding all perfect powers which can be expressed as the sum of two rational @xmath0-units , where @xmath0 is a finite set of primes .
our approach is based upon the modularity of galois representations and , for the most part , does not require lower bounds for linear forms in logarithms .
its main virtue is that it enables to carry out such a program explicitly , at least for certain small sets of primes @xmath0 ; we do so for @xmath1 and @xmath2 . .
And you have already written the first three sentences of the full article: if @xmath3 is a finite set of primes , we define the set of _ @xmath0-units _ to be those integers of the shape @xmath4 , with exponents @xmath5 nonnegative integers .
the arithmetic of such sets has been frequently studied due to its connections to a wide variety of problems in number theory and arithmetic geometry . in the latter direction , equations of the shape @xmath6 where @xmath7 and @xmath8 are @xmath0-units for certain specific sets @xmath0 ,
arise naturally when one wishes to make effective a theorem of shafarevich on the finiteness of isomorphism classes of elliptic curves over a number field @xmath9 with good reduction outside a given finite set of primes . by way of a simple example ,.
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if we wish to find all elliptic curves @xmath10 with nontrivial rational @xmath11-torsion and good reduction outside @xmath12 , we are led to consider curves @xmath13 of the shape @xmath14 where @xmath15 and @xmath16 are rational integers satisfying @xmath17 for nonnegative integers @xmath5 .
writing @xmath18 , we thus seek to solve equation ( [ two ] ) , with @xmath19 and @xmath20 .
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11,872 |
Suppose that you have an abstract for a scientific paper: we study the possibility to observe the two channel kondo physics in multiple quantum dot heterostructures in the presence of magnetic field .
we show that a fine tuning of the coupling parameters of the system and an external magnetic field may stabilize the two channel kondo critical point .
we make predictions for behavior of the scaling of the differential conductance in the vicinity of the quantum critical point , as a function of magnetic field , temperature and source - drain potential . .
And you have already written the first three sentences of the full article: simple models for non - fermi liquids , such as the multi - channel kondo models , have attracted recently much theoretical interest .
the predicted thermodynamic properties as well as transport properties are markedly different from the properties of a fermi liquid . for example
the conductance is predicted to approach its asymptotic zero temperature value as the square root of the temperature . in this work.
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we study a system built of a small quantum dot with even number of electrons coupled to a large dot and free leads .
we explore the possibility to observe two channel kondo physics in it by a fine tuning of the magnetic field and the couplings between the small quantum dot , the leads and the large dot . in the first experimental realization of the _
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11,873 |
Suppose that you have an abstract for a scientific paper: superselection rules ( ssrs ) constrain the allowed states and operations in quantum theory . they limit preparations and measurements hence impact upon our ability to observe non - locality , in particular the violation of bell inequalities .
we show that a reference frame compatible with a particle number ssr does not allow observers to violate a bell inequality if and only if it is prepared using only local operations and classical communication . in particular , jointly prepared separable reference frames are sufficient for obtaining violations of a bell inequality .
we study the size and non - local properties of such reference frames using superselection - induced variance .
these results suggest the need for experimental bell tests in the presence of superselection . .
And you have already written the first three sentences of the full article: symmetries impose powerful constraints in physics , leading wick _ et al . _ to suggest that the associated conserved quantities lead to additional restrictions on quantum theory , the so - called superselection rules ( ssrs ) @xcite .
they conjectured that superselection prevents the existence of coherent superpositions of charge , for example .
however , aharonov and susskind @xcite showed that the ability to observe superpositions depends on having a shared reference frame relative to which the system can be prepared and measured ..
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more generally , elements of quantum theory require reformulation in the presence of ssrs . quantum entanglement and various forms of non - locality
are particular examples of phenomena that are affected by the presence of ssrs , and a vast body of literature already exists on these topics @xcite-@xcite . here , we focus on bell inequality violation in the presence of ssrs .
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11,874 |
Suppose that you have an abstract for a scientific paper: we explore a transverse - field ising model that exhibits both spontaneous symmetry - breaking and eigenstate thermalization . within its ferromagnetic phase , the exact eigenstates of the hamiltonian of any large but finite - sized system are all schrdinger cat states : superpositions of states with ` up ' and ` down ' spontaneous magnetization .
this model exhibits two dynamical phase transitions _ within _ its ferromagnetic phase : in the lowest - temperature phase the magnetization can macroscopically oscillate between up and down .
the relaxation of the magnetization is always overdamped in the remainder of the ferromagnetic phase , which is divided in to phases where the system thermally activates itself _ over _ the barrier between the up and down states , and where it quantum tunnels . .
And you have already written the first three sentences of the full article: the dynamical properties of isolated many - body quantum systems have long been of interest , due to their role in the fundamentals of quantum statistical mechanics .
more recently , experiments approximating this ideal of isolated many - body quantum systems have become feasible in systems of trapped atoms @xcite and ions @xcite , and as a consequence this topic has received renewed attention .
it appears that a broad class of such systems obey the eigenstate thermalization hypothesis ( eth ) @xcite ..
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the eth asserts that each exact many - body eigenstate of a system s hamiltonian is , all by itself , a proper microcanonical ensemble in the thermodynamic limit , in which any small subsystem is thermally equilibrated , with the remainder of the system acting as a reservoir . in the present paper
we present some interesting results for an infinite - range transverse - field ising model that obeys the eth and also has spontaneous symmetry - breaking .
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Suppose that you have an abstract for a scientific paper: an exclusive measurement of the decay @xmath0 has been performed at the wasa facility at cosy .
the @xmath1 mesons were produced in the fusion reaction pd@xmath2he x at a proton beam momentum of 1.7 gev / c .
efficiency corrected differential distributions have been extracted based on 13960@xmath3140 events after background subtraction . the measured pion angular distribution is consistent with a relative _ p_-wave of the two - pion system , whereas the measured photon energy spectrum was found at variance with the simplest gauge invariant matrix element of @xmath0 .
a parameterization of the data can be achieved by the additional inclusion of the empirical pion vector form factor multiplied by a first - order polynomial in the squared invariant mass of the @xmath4 system .
@xmath1 meson , box anomaly , exclusive measurement 14.40.be , 13.20.jf , 12.39.fe .
And you have already written the first three sentences of the full article: the @xmath1 meson plays a special role in understanding low
energy quantum chromo dynamics ( qcd ) .
chiral symmetry , its realization in hadron physics at low energies and the role of explicit chiral symmetry breaking due to the masses of the light quarks @xmath5 can be investigated using @xmath1 decays ..
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this work focuses on the anomalous sector of qcd , which is manifested in the radiative decays of the @xmath1 meson .
the radiative decay @xmath0 is the fourth strongest decay mode of the @xmath1 meson with a branching ratio of 4.60 @xmath3 0.16% @xcite .
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11,876 |
Suppose that you have an abstract for a scientific paper: almost from the inception of hilbert s program , foundational and structural efforts in proof theory have been directed towards the goal of clarifying the computational content of modern mathematical methods .
this essay surveys various methods of extracting computational information from proofs in classical first - order arithmetic , and reflects on some of the relationships between them .
variants of the gdel - gentzen double - negation translation , some not so well known , serve to provide canonical and efficient computational interpretations of that theory . .
And you have already written the first three sentences of the full article: hilbert s program was launched , in 1922 , with the specific goal of demonstrating the consistency of modern , set - theoretic methods , using only finitary means .
but the program can be viewed more broadly as a response to the radical methodological changes that had been introduced to mathematics in the late nineteenth century .
central to these changes was a shift in mathematical thought whereby the goal of mathematics was no longer viewed as that of developing powerful methods of calculation , but , rather , that of characterizing abstract , possibly infinite , mathematical structures , often in ways that could not easily be reconciled with a computational understanding ..
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grisha s work over the years has touched on almost every aspect of proof theory , both of the reductive ( foundational ) and structural sort , involving a wide range of logical frameworks . but
much of his work addresses the core proof - theoretic concern just raised , and has served to provide us with a deep and satisfying understanding of the computational content of nonconstructive , infinitary reasoning .
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Suppose that you have an abstract for a scientific paper: we search for high - redshift dropout galaxies behind the hubble frontier fields ( hff ) galaxy cluster macs j1149.5 + 2223 , a powerful cosmic lens that has revealed a number of unique objects in its field . using the deep images from the _ hubble _ and _ spitzer _ space telescopes
, we find 11 galaxies at @xmath0 in the macs j1149.5 + 2223 cluster field , and 11 in its parallel field .
the high - redshift nature of the bright @xmath1 galaxy macs1149-jd , previously reported by zheng et al . , is further supported by non - detection in the extremely deep optical images from the hff campaign . with the new photometry ,
the best photometric redshift solution for macs1149-jd reduces slightly to @xmath2 .
the young galaxy has an estimated stellar mass of @xmath3 , and was formed at @xmath4 when the universe was @xmath5 myr old .
data available for the first four hff clusters have already enabled us to find faint galaxies to an intrinsic magnitude of @xmath6 , approximately a factor of 10 deeper than the parallel fields . .
And you have already written the first three sentences of the full article: the galaxy cluster macs j1149.5 + 2223 ( @xmath7 , * ? ? ?
* hereafter ) is one of the most interesting and best studied cosmic lenses .
its strong lensing power is demonstrated by many sets of multiply - imaged galaxies , including the largest known lensed images of a face - on spiral galaxy at @xmath8 , whose highly magnified images display little distortion @xcite ..
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the first multiply - imaged supernova was discovered in the lensed images of this spiral , forming an einstein cross @xcite .
the supernova reappeared a year later in another counter image of the spiral as predicted by lensing models @xcite . because of its high magnification power ,
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Suppose that you have an abstract for a scientific paper: in recent years , planck - scale modifications to particles dispersion relation have been deeply studied for the possibility to formulate some phenomenology of planckian effects in astrophysical and cosmological frameworks .
there are some indications [ arxiv : gr - qc/0611024 ] that finsler geometry can provide some generalization of riemannian geometry which may allow to account for non - trivial ( planckian ) structure of relativistic particles configuration space .
we investigate the possibility to formalize planck - scale deformations to relativistic models in curved spacetime , within the framework of finsler geometry .
we take into account the general strategy of analysis of modifications of dispersion relations in curved spacetimes proposed in [ arxiv:1507.02056 ] , generalizing to the de sitter case the results obtained in [ arxiv:1407.8143 ] , for deformed relativistic particle kinematics in flat spacetime using finsler formalism . .
And you have already written the first three sentences of the full article: one of the most important definitions in euclidean geometry concerns the norm of a vector and the distance between two points : they are defined using the pythagoras theorem . in the xix century , riemann generalized ideas of gauss , introduced the concept of manifold and constructed the riemannian geometry , in which pythagoras theorem would be only valid at a point or along a line , but would no longer be the way of measuring distances in an open set in the manifold ; instead , such measure would be performed using a general metric field .
euclidean geometry was the background of newtonian mechanics and was invariant by galilean boosts and rotations , but the advent of special relativity and a new kind of invariance group inspired the use of a geometry that unified space and time in a way that could keep invariant the interval between two events : such was minkowski geometry , in which the interval represents a distance in such spacetime , that is measured by a formula similar to the euclidean one , however allowing for positive , null or negative norms of vectors : this is a pseudo - euclidean space .
the next generalization , that is responsible for a relativistic description of gravity was performed by einstein by writing general relativity using a generalization of the minkowski space by the same terms of the generalization from euclidean to riemannian geometry : spacetime was defined as a differential manifold endowed with a pseudo - riemannian metric ..
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in the geometries just described , one uses a metric to define the norm of vectors and co - vectors and , then defines the length of curves and the distance between points .
an important feature of special relativity that gains a geometrical interpretation is the dispersion relation of particles , _ i d est _ the equation that relates energy , momentum and mass , it is defined as the norm of the four - momentum in minkowski spacetime
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Suppose that you have an abstract for a scientific paper: quantum computing shows great promise for the solution of many difficult problems , such as the simulation of quantum systems and the factorisation of large numbers .
while the theory of quantum computing is well understood , it has proved difficult to implement quantum computers in real physical systems .
it has recently been shown that nuclear magnetic resonance ( nmr ) can be used to implement small quantum computers using the spin states of nuclei in carefully chosen small molecules . here
we demonstrate the use of an nmr quantum computer based on the pyrimidine base cytosine , and the implementation of a quantum algorithm to solve deutsch s problem ( distinguishing between constant and balanced functions ) .
this is the first successful implementation of a quantum algorithm on any physical system .
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ + j. a. jones + _ oxford centre for molecular sciences , new chemistry laboratory , south parks road , oxford ox1 3qt , uk , _ and _ centre for quantum computing , clarendon laboratory , parks road , oxford ox1 3pu , uk _ + m. mosca + _ centre for quantum computing , clarendon laboratory , parks road , oxford ox1 3pu , uk , _ and _ mathematical institute , 2429 st giles , oxford , ox1 3 lb , uk _ + correspondence should be addressed to j. a. jones at the new chemistry laboratory . + email : [email protected] + _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _....
And you have already written the first three sentences of the full article: in 1982 feynman pointed out that it appears to be impossible to efficiently simulate the behaviour of a quantum mechanical system with a computer@xcite .
this problem arises because the quantum system is not confined to its eigenstates , but can exist in any superposition of them , and so the space needed to describe the system is very large . to take a simple example , a system comprising @xmath0 two level sub - systems , such as @xmath0 spin - particles , inhabits a hilbert space of dimension @xmath1 , and evolves under a series of transformations described by matrices containing @xmath2 elements . for this reason it is impractical to simulate the behaviour of spin systems containing more than about a dozen spins .
the difficulty of simulating quantum systems using classical computers suggests that quantum systems have an information processing capability much greater than that of corresponding classical systems ..
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thus it might be possible to build quantum mechanical computers@xcite which utilise this information processing capability in an effective way to achieve a computing power well beyond that of a classical computer . such a quantum computer could be used to efficiently simulate other quantum mechanical systems@xcite , or to solve conventional mathematical problems@xcite which suffer from a similar exponential growth in complexity , such as factoring@xcite .
considerable progress in this direction has been made in recent years .
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Suppose that you have an abstract for a scientific paper: the observed radio - optical - x - ray spectral energy distributions ( seds ) of 22 hot spots and 45 knots in the jets of 35 active galactic nuclei are complied from literature and modeled with single - zone lepton models .
it is found that the observed luminosities at 5 ghz ( @xmath0 ) and at 1 kev ( @xmath1 ) are tightly correlated , and the two kinds of sources can be roughly separated with a division of @xmath2 .
our sed fits show that the mechanisms of the x - rays are diverse . while the x - ray emission of a small fraction of the sources is a simple extrapolation of the synchrotron radiation for the radio - to - optical emission , an inverse compton ( ic ) scattering component is necessary to model the x - rays for most of the sources . considering the sources at rest ( the doppler factor @xmath3 )
, the synchrotron - self - compton ( ssc ) scattering would dominate the ic process .
this model can interpret the x - rays of some hot spots with a magnetic field strength ( @xmath4 ) being consistent with the equipartition magnetic field ( @xmath5 ) in one order of magnitude , but an unreasonably low @xmath4 is required to model the x - rays for all knots . measuring the deviation between @xmath4 and @xmath6 with ratio @xmath7 , we find that @xmath8 is greater than 1 and it is tightly anti - correlated with ratio @xmath9 for both the knots and the hot spots .
we propose that the deviation may be due to the neglect of the relativistic bulk motion for these sources .
considering this effect , the ic / cmb component would dominate the ic process .
we show that the ic / cmb model well explains the x - ray emission for most sources under the equipartition condition . although the derived beaming factor ( @xmath10 ) and co - moving equipartition magnetic field ( @xmath11 ) of some hot spots are comparable to the knots , the @xmath10 values of the hot spots tend to be smaller and their @xmath12 values tend to be larger than that of the knots , favoring the idea that the hot spots are jet....
And you have already written the first three sentences of the full article: hot spots and knots in large - scale jets have been observed in many active galactic nuclei ( agns ) .
hot spots are often found near the outmost boundaries of radio lobes .
they are regarded as jet termination ( fnanaroff & riley 1974 ; blandford & rees 1974 ; begelman et al ..
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1984 ; bicknell 1985 ; meisenheimer et al .
knots are usually thought to be a part of a well - collimated jet ( e.g. , harris & krawczynski 2006 ) .
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Suppose that you have an abstract for a scientific paper: we present radio and x - ray observations of an impulsive solar flare that was moderately intense in microwaves , yet showed very meager euv and x - ray emission .
the flare occurred on 2001 oct 24 and was well - observed at radio wavelengths by the nobeyama radioheliograph ( norh ) , the nobeyama radio polarimeters ( norp ) , and by the owens valley solar array ( ovsa ) .
it was also observed in euv and x - ray wavelength bands by the trace , goes , and _ yohkoh _ satellites .
we find that the impulsive onset of the radio emission is progressively delayed with _ increasing _ frequency relative to the onset of hard x - ray emission .
in contrast , the time of flux density maximum is progressively delayed with _ decreasing _ frequency . the decay phase is independent of radio frequency .
the simple source morphology and the excellent spectral coverage at radio wavelengths allowed us to employ a nonlinear @xmath0-minimization scheme to fit the time series of radio spectra to a source model that accounts for the observed radio emission in terms of gyrosynchrotron radiation from mev - energy electrons in a relatively dense thermal plasma .
we discuss plasma heating and electron acceleration in view of the parametric trends implied by the model fitting .
we suggest that stochastic acceleration likely plays a role in accelerating the radio - emitting electrons . .
And you have already written the first three sentences of the full article: radio and x - ray radiation from solar flares have been used for many years to study energy release , plasma heating , and particle acceleration and transport .
joint studies of radio and x - ray radiation are particularly powerful because they probe populations of electrons at different energies , ranging from hot thermal electrons to nonthermal electrons of tens of kev emitting at soft x - ray ( sxr ) and hard x - ray ( hxr ) wavelengths , and nonthermal electrons with energies ranging from hundreds of kev to several mev emitting @xmath1-rays and centimeter- and millimeter - wavelength radiation ( e.g. , takakura et al .
1983 ; klein et al . 1986 ; bruggmann et al . 1994 ; ramaty et al ..
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1994 , trottet et al .
1998 , 2002 ) .
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11,882 |
Suppose that you have an abstract for a scientific paper: human mobility has been traditionally studied using surveys that deliver snapshots of population displacement patterns .
the growing accessibility to ict information from portable digital media has recently opened the possibility of exploring human behavior at high spatio - temporal resolutions .
mobile phone records , geolocated tweets , check - ins from foursquare or geotagged photos , have contributed to this purpose at different scales , from cities to countries , in different world areas .
many previous works lacked , however , details on the individuals attributes such as age or gender . in this work ,
we analyze credit - card records from barcelona and madrid and by examining the geolocated credit - card transactions of individuals living in the two provinces , we find that the mobility patterns vary according to gender , age and occupation .
differences in distance traveled and travel purpose are observed between younger and older people , but , curiously , either between males and females of similar age . while mobility displays some generic features , here we show that sociodemographic characteristics play a relevant role and must be taken into account for mobility and epidemiological modelization . .
And you have already written the first three sentences of the full article: everyday , billions of individuals generate a large volume of geolocated data by using their mobile phone , gps , public transport cards or credit cards . such a vast amount of data is bringing new opportunities for the research in socio - technical systems @xcite . indeed
, geolocated data allow the identification of when and where people interact with or through ict tools .
each time someone makes a phone call or pays with a credit card the event gets registered contributing to massive databases with potential to provide useful insights on human behavior and mobility @xcite ..
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for example , the authors of refs .
@xcite used credit card and mobile phone datasets to study statistical characteristics of mobility patterns and showed that the distribution of displacement of all users can be approximated by a levy law . recently
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Suppose that you have an abstract for a scientific paper: we show that all nontrivial cp - violating phases can be determined in terms of three lepton flavor mixing angles and the ratio of @xmath0 to @xmath1 in the minimal seesaw model in which the frampton - glashow - yanagida ( fgy ) ansatz is incorporated .
this important point allows us to make very specific predictions for the cosmological baryon number asymmetry and cp violation in neutrino oscillations .
a measurement of the smallest neutrino mixing angle will sensitively test the fgy ansatz , in particular in the case that three light neutrinos have a normal mass hierarchy . .
And you have already written the first three sentences of the full article: in the minimal standard model of electroweak interactions , the lepton number conservation is assumed and neutrinos are exactly massless weyl particles . however , today s super - kamiokande @xcite , sno @xcite , kamland @xcite and k2k @xcite neutrino oscillation experiments have provided us with very strong evidence that neutrinos are actually massive and lepton flavor mixing does exist .
the most economical modification of the minimal standard model , which can both accommodate neutrino masses and allow lepton number violation to explain the cosmological baryon asymmetry via leptogenesis @xcite , is to introduce two heavy right - handed neutrinos @xmath2 and keep the lagrangian of electroweak interactions invariant under the @xmath3 gauge transformation @xcite .
after the spontaneous electroweak symmetry breaking , this simple but interesting model yields the following neutrino mass term : @xmath4 where @xmath5 with @xmath6 being the charge - conjugation operator ; and @xmath7 denote the left - handed neutrinos . the dirac neutrino mass matrix @xmath8 is a @xmath9 rectangular matrix , and the majorana neutrino mass matrix @xmath10 is a @xmath11 symmetric matrix ..
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the scale of @xmath8 is characterized by the electroweak scale @xmath12 gev . in contrast
, the scale of @xmath10 can be much higher than @xmath13 , because @xmath14 and @xmath15 are @xmath16 singlets and their corresponding mass term is not subject to the scale of gauge symmetry breaking .
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11,884 |
Suppose that you have an abstract for a scientific paper: the characteristic scale of neutral current , provided by an extension of standard model with a local group over the right - handed fermions , determines the smallness of neutrino masses of dirac kind .
the experimental observation of neutrino oscillations imposes the stringent limit on the @xmath0 physics appearance at low energies .
= -1.7 cm = -1 cm * neutrino masses and @xmath0 physics * v.v.kiselev + institute for high energy physics + 142284 , protvino , moscow region , russia . + e - mail : [email protected] .
And you have already written the first three sentences of the full article: the recent clear observation of neutrino oscillations @xcite indicates the non - zero masses for the neutrinos @xcite , which are generally considered to be extremely small due to the following mechanisms .
the common form of neutrino mass matrix is expressed through three terms : 1 .
the majorana mass @xmath1 for the left - handed neutrino , that appears as the triplet weak isospin contribution , 2 ..
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the dirac mass term @xmath2 , involving the interaction with the sterile right - handed neutrino @xmath3 , 3 .
the majorana mass @xmath4 for the singlet @xmath3 over the weak interaction .
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11,885 |
Suppose that you have an abstract for a scientific paper: control - based continuation is technique for tracking the solutions and bifurcations of nonlinear experiments .
the basic idea is to apply the method of numerical continuation to a feedback - controlled physical experiment . since in an experiment it is not ( generally ) possible to set the state of the system directly , the control target is used as a proxy for the state .
the challenge then becomes to determine a control target such that the control is non - invasive , that is , it stabilises a steady - state ( or periodic orbit ) of the original open - loop experiment without altering it otherwise .
once implemented , control - based continuation enables the systematic investigation of the bifurcation structure of a physical system , much like if it was numerical model
. however , stability information ( and hence bifurcation detection and classification ) is not readily available due to the presence of stabilising feedback control .
this paper uses methods from the system identification community to extract stability information in the form of floquet multipliers from the closed - loop experiment , thus enabling the direct detection of bifurcations .
in particular , it is shown that a periodic auto - regressive model with exogenous inputs ( arx ) can be constructed that approximates the time - varying linearisation of the experiment around a particular periodic orbit .
this method is demonstrated using a physical nonlinear tuned mass damper . numerical continuation , bifurcation theory , system identification , feedback control .
And you have already written the first three sentences of the full article: control - based continuation is a systematic method for performing bifurcation studies on physical experiments .
based on modern feedback control schemes it enables dynamical phenomena to be detected and tracked as system parameters are varied in a similar manner to how nonlinear numerical models can be investigated using numerical continuation .
control - based continuation was originally developed as an extension to pyragas time - delayed feedback control @xcite to make it more robust and suitable for parameter studies @xcite , though its current implementation contains no elements of time - delayed feedback ..
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the use of feedback control for the investigation of nonlinear systems is not new ; in addition to time - delayed feedback , methods such as ogy control @xcite have previously been employed to provide non - invasive control to stabilise unstable orbits and investigate dynamical phenomena .
indeed , previous authors have gone as far as to implement such control schemes within parameter continuation studies to numerically simulate particular experiments such as atomic force microscopes @xcite or reaction kinetics @xcite .
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Suppose that you have an abstract for a scientific paper: we report new calculations of the cooling rate of primordial gas by the hd molecule , taking into account its ro - vibrational structure .
the hd cooling function is calculated including radiative and collisional transitions for @xmath0 rotational levels , and for the vibrational levels @xmath1 and 3 .
the ro - vibrational level population is calculated from the balance equation assuming steady state .
the cooling function is evaluated in the ranges of the kinetic temperatures , @xmath2 , from @xmath3 to @xmath4 k and the number densities , @xmath5 , from 1 to @xmath6 @xmath7 .
we find that the inclusion of collisional ro - vibrational transitions increases significantly the hd cooling efficiency , in particular for high densities and temperatures . for @xmath8 and @xmath9
k the cooling function becomes more than an order of magnitude higher than previously reported .
we give also the hd cooling rate in the presence of the cosmic microwave radiation field for radiation temperatures of 30 , 85 and 276 k ( redshifts of 10 , 30 and 100 ) .
the tabulated cooling functions are available at http://www.cifus.uson.mx/personal_pages/anton/data/hd_cooling/hd_cool.html .
we discuss the relevance to explore the effects of including our results into models and simulations of galaxy formation , especially in the regime when gas cools down from temperatures above @xmath10k .
[ firstpage ] cosmology : first stars galaxies : formation molecular processes .
And you have already written the first three sentences of the full article: the cooling and thermal balance of the primordial , zero - metallicity gas by molecular hydrogen ( h@xmath11 ) and deuterated hydrogen ( hd ) are key ingredients in the formation process of the first baryonic objects in the universe , such as dwarf - sized galaxies and pop - iii stars ( see for recent reviews on this topic barkana & loeb 2001 ; ciardi & ferrara 2004 ; bromm & larson 2004 ) . it is well known that h@xmath11 and hd molecules form in the universe after recombination ( e.g. , lepp & shull 1984 ; puy et al .
1993 ; palla , galli , & silk 1995 ; galli & palla 1998 ; stancil , lepp , & dalgarno 1998 ) . the formation of h@xmath11 and hd molecules in primordial gas is also possible in a postshock flow ( mac low & shull 1986 ; shapiro & kang 1987 ; uehara & inutsuka 2000 ) , where the gas density and temperature , as well as the molecular fractions , are different from those of the expanding homogeneous gas . the h@xmath11 molecule is considered typically as the main coolant in the primordial medium ( e.g. , tegmark et al . 1997 ; abel , bryan & norman 2000 ; bromm , coppi & larson 2002 ) .
thus , rather detailed calculations were carried out for it ( see for the most recent results and references therein le bourlot , pineau des forts & flower 1999 ; flower et al ..
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2000 ; shaw et al . 2005 ) .
nevertheless , in the case of dense primordial gas , the role of the hd molecule in the thermal and cooling process may become comparable to or more important than the one of h@xmath11 .
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11,887 |
Suppose that you have an abstract for a scientific paper: this article reviews the present status of high energy @xmath0-ray astronomy at energies above 30 mev .
observations in the past decade using both space- and ground - based experiments have been primarily responsible for giving a tremendous boost to our knowledge of the high energy universe .
high energy @xmath0-rays have been detected from a wide range of galactic and extragalactic astrophysical sources , such as @xmath0-ray bursters , pulsars , and active galaxies .
these observations have established high energy @xmath0-ray astronomy as a vital and exciting field , that has a bright future .
this review summarizes the experimental techniques , observations and results obtained with recent experiments , and concludes with a short description of future prospects . .
And you have already written the first three sentences of the full article: high energy @xmath0-rays are one of the most direct ways of studying the non - thermal universe .
sources of very high energy radiation enable us to explore the highest energy accelerators in the cosmos , in situations with extreme gravitational and magnetic fields .
although high energy @xmath0-rays have been studied for some time , rapid development in the field came only in the 1990s ..
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the most significant thrust to high energy astronomy above 30 mev came with the launch of the _ compton gamma ray observatory _ ( cgro ) in 1991 , which carried onboard the energetic gamma - ray experiment telescope ( egret ) , along with three other instruments . until june 2000 ,
when cgro was de - orbitted , egret produced a wealth of astrophysical results , and was responsible for the detection of more than 270 point sources of @xmath0-rays @xcite .
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11,888 |
Suppose that you have an abstract for a scientific paper: we calculate qcd corrections to transversely polarized drell - yan process at a measured @xmath0 of the produced lepton pair in the dimensional regularization scheme . the @xmath0 distribution is discussed resumming soft gluon effects relevant for small @xmath0 .
hard processes with polarized nucleon beams enable us to study spin - dependent dynamics of qcd and the spin structure of nucleon .
the helicity distribution @xmath1 of quarks within nucleon has been measured in polarized dis experiments , and @xmath2 of gluons has also been estimated from the scaling violations of them .
on the other hand , the transversity distribution @xmath3 , i.e. the distribution of transversely polarized quarks inside transversely polarized nucleon , can not be measured in inclusive dis due to its chiral - odd nature,@xcite and remains as the last unknown distribution at the leading twist .
transversely polarized drell - yan ( tdy ) process is one of the processes where the transversity distribution can be measured , and has been undertaken at rhic - spin experiment .
we compute the 1-loop qcd corrections to tdy at a measured @xmath0 and azimuthal angle @xmath4 of the produced lepton in the dimensional regularization scheme . for this purpose
, the phase space integration in @xmath5-dimension , separating out the relevant transverse degrees of freedom , is required to extract the @xmath6 part of the cross section characteristic of the spin asymmetry of tdy.@xcite the calculation is rather cumbersome compared with the corresponding calculation in unpolarized and longitudinally polarized cases , and has not been performed so far .
we obtain the nlo @xmath7 corrections to the tdy cross section in the @xmath8 scheme .
we also include soft gluon effects by all - order resummation of logarithmically enhanced contributions at small @xmath0 ( `` edge regions of the phase space '' ) up to next - to - leading logarithmic ( nll ) accuracy , and obtain the first complete result of the @xmath0 distribution for all....
And you have already written the first three sentences of the full article: we would like to thank w. vogelsang for valuable discussions .
the work of j.k . was supported by the grant - in - aid for scientific research no .
the work of k.t . was supported by the grant - in - aid for scientific research no ..
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11,889 |
Suppose that you have an abstract for a scientific paper: we investigate the kaon semileptonic decay ( @xmath0 ) form factors within the framework of the nonlocal chiral quark model ( @xmath1qm ) from the instanton vacuum , taking into account the effects of flavor su(3 ) symmetry breaking .
we also consider the problem of gauge invariance arising from the momentum - dependent quark mass in the present work .
all theoretical calculations are carried out without any adjustable parameter , the average instanton size ( @xmath2 fm ) and the inter - instanton distance ( @xmath3 fm ) having been fixed .
we also show that the present results satisfy the callan - treiman low - energy theorem as well as the ademollo - gatto theorem . using the @xmath0 form factors , we evaluate relevant physical quantities .
it turns out that the effects of flavor su(3 ) symmetry breaking are essential in reproducing the kaon semileptonic form factors .
the present results are in a good agreement with experiments , and are compatible with other model calculations . .
And you have already written the first three sentences of the full article: it is of great importance to understand semileptonic decays of kaons ( @xmath0 ) , since it plays a significant role in determining the ckm matrix element @xmath4 precisely @xcite .
furthermore , it provides a simple phenomenological basis for testing the breaking of flavor su(3 ) symmetry : in exact flavor su(3 ) symmetry , the kaon semileptonic form factor @xmath5 becomes unity .
the ademollo - gatto @xcite theorem asserts that of second order are the corrections of flavor su(3 ) symmetry breaking to the form factors of vector currents at zero momentum transfer ( @xmath6 ) . however ,.
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when goldstone bosons are involved , the ademollo - gatto theorem must be modified : while the singlet part of flavor su(3 ) symmetry breaking preserves flavor su(3 ) symmetry , it breaks chiral su(3)@xmath7su(3 ) symmetry .
langacker and pagels showed that the corrections of flavor su(3 ) symmetry breaking appear to first order due to the presence of that singlet part @xcite .
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11,890 |
Suppose that you have an abstract for a scientific paper: a ( smooth ) dynamical system with transformation group @xmath0 is a triple @xmath1 , consisting of a unital locally convex algebra @xmath2 , the @xmath3-torus @xmath0 and a group homomorphism , which induces a ( smooth ) continuous action of @xmath0 on @xmath2 . in this paper
we present a new , geometrically oriented approach to the noncommutative geometry of principal torus bundles based on such dynamical systems .
our approach is inspired by the classical setting : in fact , after recalling the definition of a trivial noncommutative principal torus bundle , we introduce a convenient ( smooth ) localization method for noncommutative algebras and say that a dynamical system @xmath1 is called a noncommutative principal @xmath0-bundle , if localization leads to a trivial noncommutative principal @xmath0-bundle .
we prove that this approach extends the classical theory of principal torus bundles and present a bunch of ( non - trivial ) noncommutative examples . .
And you have already written the first three sentences of the full article: the correspondence between geometric spaces and commutative algebras is a familiar and basic idea of algebraic geometry .
noncommutative topology started with the famous gelfand - naimark theorems : every commutative c*-algebra is the algebra of continuous functions vanishing at infinity on a locally compact space and vice versa . in particular , a noncommutative c*-algebra may be viewed as `` the algebra of continuous functions vanishing at infinity '' on a `` quantum space '' .
the aim of noncommutative geometry is to develop the basic concepts of topology , measure theory and differential geometry in algebraic terms and then to generalize the corresponding classical results to the setting of noncommutative algebras ..
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the question whether there is a way to translate the geometric concept of a fibre bundle to noncommutative geometry is quite interesting in this context . in the case of vector bundles a refined version of the theorem of serre and swan @xcite gives the essential clue : the category of vector bundles over a manifold @xmath4 is equivalent to the category of finitely generated projective modules over @xmath5 .
it is therefore reasonable to consider finitely generated projective modules over an arbitrary algebra as noncommutative vector bundles " .
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11,891 |
Suppose that you have an abstract for a scientific paper: we calculate vacuum polarization corrections to the binding energies in neutral alkali atoms na through to the superheavy element e119 .
we employ the relativistic hartree - fock method to demonstrate the importance of relaxation of the electronic core and the correlation potential method to study the effects of second and higher orders of perturbation theory .
these many - body effects are sizeable for all orbitals , though particularly important for orbitals with angular momentum quantum number @xmath0 .
the orders of magnitude enhancement for @xmath1 waves produces shifts that , for rb and the heavier elements , are larger than those for @xmath2 waves and only an order of magnitude smaller than the @xmath3-wave shifts .
the many - body enhancement mechanisms that operate for vacuum polarization apply also to the larger self - energy corrections . .
And you have already written the first three sentences of the full article: within the last decade the need has arisen for a method that incorporates quantum electrodynamics ( qed ) radiative corrections into the many - body problem for heavy atoms and ions .
for example , account of qed radiative corrections , that is , the vacuum polarization and self - energy corrections , were critical in the interpretation of the measurement @xcite of the parity violating amplitude in cesium , which restored an apparent deviation from the standard model of particle physics ( see , e.g. , @xcite ) .
there are other areas where full account of qed and many - body effects are required , including in the transition frequencies of many - electron highly - charged ions ( see , e.g. , @xcite ) and in the spectra and chemical properties of superheavy elements @xcite ..
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ongoing improvements in experimental precision and developments in many - body methods across a range of precision atomic applications necessitate the accurate treatment of combined many - body and qed effects in the generic atomic problem .
the one - loop radiative corrections are made up of the ( local ) vacuum polarization and the ( non - local ) self - energy terms .
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11,892 |
Suppose that you have an abstract for a scientific paper: let @xmath0 be a field of characteristic @xmath1 at least 5 .
we study the loewy structures of specht modules in the principal block of @xmath2 .
we show that a specht module in the block has loewy length at most 4 and composition length at most 14 .
furthermore , we classify which specht modules have loewy length 1 , 2 , 3 , or 4 , produce a specht module having 14 composition factors , describe the second radical layer and the socle of the reducible specht modules , and prove that if a specht module corresponds to a partition that is @xmath1-regular and @xmath1-restricted then the head of the specht module does not extend the socle . .
And you have already written the first three sentences of the full article: in @xcite , chuang and tan determine the loewy structures of specht modules in defect 2 over odd characteristic .
the authors prove results for the schur algebra , and then translate to results for the symmetric group by applying the schur functor .
the authors mention that the symmetric group results may be proven entirely in the representation theory of the symmetric group . throughout this paper @xmath3.
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is the symmetric group on @xmath4 letters and @xmath0 is a field of characteristic @xmath1 at least 5 .
the goal of this paper is to establish some loewy structure results for specht modules which lie in the principal block of @xmath2 . for the remainder of the paper , the principal block of @xmath2
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11,893 |
Suppose that you have an abstract for a scientific paper: we show how the generation of a lepton number in the early universe induced by @xmath0 , in presence of small baryon number inhomogeneities , gives rise to the formation of lepton domains .
the structure of these domains reflects the spectral features of the baryon number inhomogeneities that generated it and interestingly the size of the lepton domains can be super - horizon .
pacs numbers : 14.60.pq ; 14.60.st ; 98.80.bp;11.30.fs keywords : early universe , neutrino oscillations , sterile neutrino , baryon isocurvature perturbations , leptogenesis . .
And you have already written the first three sentences of the full article: if one assumes the existence of a mixing between an active neutrino flavor @xmath1 and a sterile neutrino flavor , then a lepton number can be generated in the early universe @xcite .
to this purpose a small vacuum mixing angle ( @xmath2 ) is necessary ( the mass eigenstates almost coincide with the interaction eigenstates ) .
moreover the sterile neutrino must be lighter than the active neutrino and the absolute value of @xmath3 , the difference of squared masses , must be in the range @xmath4 ..
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in fact the critical temperature at which the generation occurs is given , if the sterile neutrino production is until that time negligible , by the expression : @xmath5 it follows that if @xmath6 , then @xmath7 and the lepton number variation would be dominated by the msw effect . in this case a lepton number larger than @xmath8 can not be generated @xcite .
on the other hand if @xmath9 then @xmath10 and one should be able to describe the neutrino oscillations in a quark - gluon plasma , something beyond the present level of matter effects account ( moreover it is not interesting in this context , because it would imply active neutrino masses much higher than @xmath11 , cosmologically excluded if neutrinos are stable ) .
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11,894 |
Suppose that you have an abstract for a scientific paper: using the sunspot numbers reported during the maunder minimum and the empirical relations between the mode frequencies and solar activity indices , the variations in the total solar irradiance and 10.7 cm radio flux for the period 1645 to 1715 is estimated .
we find that the total solar irradiance and radio flux during the maunder minimum decreased by 0.19% and 52% respectively , as compared to the values for solar cycle 22 . .
And you have already written the first three sentences of the full article: the period of low solar activity between 1645 to 1715 is commonly known as the maunder minimum and has attracted attention of researchers as it put forward many unexpected questions . during this period ,
the sunspots were infrequent and as a result it was assumed that the solar dynamo and the solar wind were either weak or switched off .
anomalies in the surface differential rotation during the maunder minimum @xcite also point out the global changes in the internal solar dynamo mechanism ..
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measurements of @xmath0be concentration in the dye 3 ice core @xcite recently showed that the magnetic cycles persisted throughout the maunder minimum , although the sun s over all activity was drastically reduced .
this period is also associated with the so called `` little ice age '' in europe and suggested that it might be due to a decrease in solar irradiance .
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11,895 |
Suppose that you have an abstract for a scientific paper: multicriteria optimization problems occur in many real life applications , for example in cancer radiotherapy treatment and in particular in intensity modulated radiation therapy ( imrt ) . in this work we focus on optimization problems with multiple objectives that are ranked according to their importance .
we solve these problems numerically by combining lexicographic optimization with our recently proposed level set scheme , which yields a sequence of auxiliary convex feasibility problems ; solved here via projection methods .
the projection enables us to combine the newly introduced superiorization methodology with multicriteria optimization methods to speed up computation while guaranteeing convergence of the optimization .
we demonstrate our scheme with a simple 2d academic example ( used in the literature ) and also present results from calculations on four real head neck cases in imrt ( radiation oncology of the ludwig - maximilians university , munich , germany ) for two different choices of superiorization parameter sets suited to yield fast convergence for each case individually or robust behavior for all four cases .
@xmath0 optimization department , fraunhofer - itwm , kaiserslautern 67663 , germany + @xmath1 mathematics department , ort braude college , karmiel 2161002 , israel e - mail : [email protected] and [email protected] _ keywords _ : superiorization , projection methods , feasibility problems , multicriteria optimization , iterative methods + _ msc _ : 65k10 , 65k15 , 90c25 , 90c90 + .
And you have already written the first three sentences of the full article: a wide variety of real - life problems involve the simultaneous optimization of several objectives or criteria .
objectives that contradict each are common , thus resulting in situations where one objective can not be improved without worsening at least one other objective .
for example , in cancer radiotherapy treatment , one goal is to maximize the amount of cancerous tissue exposed to radiation treatment while another ( contradicting ) goal is to minimize the radiation exposure of healthy organs . here.
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, there is typically no trivial compromise .
problems of this kind are called _ multi - criteria optimization _ ( mco ) problems .
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11,896 |
Suppose that you have an abstract for a scientific paper: we use sloan digital sky survey ( sdss ) data release 5 ( dr5 ) @xmath0 photometry to study milky way halo substructure in the area around the north galactic cap . a simple color cut ( @xmath1 )
reveals the tidal stream of the sagittarius dwarf spheroidal , as well as a number of other stellar structures in the field .
two branches ( a and b ) of the sagittarius stream are clearly visible in an rgb - composite image created from 3 magnitude slices , and there is also evidence for a still more distant wrap behind the a branch .
a comparison of these data with numerical models suggests that the shape of the galactic dark halo is close to spherical . .
And you have already written the first three sentences of the full article: stellar streams in the milky way halo produced by the accretion of smaller galaxies are a standard prediction of hierarchical merging cosmogonies ( e.g. , * ? ? ?
* and references therein ) .
the most spectacular example is the disrupting sagittarius dwarf spheroidal ( sgr dsph ) , originally discovered by ibata , gilmore & irwin ( 1995 ) ..
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it has a heliocentric distance of @xmath2 kpc and is centered at galactic coordinates of @xmath3 and @xmath4 @xcite .
it is dominated by an intermediate age population ( between 6 and 9 gyrs , bellazzini et al .
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11,897 |
Suppose that you have an abstract for a scientific paper: ultraluminous galaxies in the local universe ( [email protected] ) emit the bulk of their energy in the mid and far - infrared .
the multiwavelength approach to these objects has shown that they are advanced mergers of gas - rich spiral galaxies .
galaxy - galaxy collisions took place on all cosmological time - scales , and nearby mergers serve as local analogs to gain insight into the physical processes that lead to the formation and trans - formation of galaxies in the more distant universe . here
i review multiwavelength observations with particular emphasis on recent results obtained with iso of mergers of massive galaxies driving the formation of : 1 ) luminous infrared galaxies , 2 ) elliptical galaxy cores , 3 ) luminous dust - enshrouded extranuclear starbursts , 4 ) symbiotic galaxies that host agns , and 5 ) tidal dwarf galaxies .
the most important implication for studies on the formation of galaxies at early cosmological timescales is that the distant analogs to the local ultraluminous infrared galaxies are invisible in the ultraviolet and optical wavelength rest - frames and should be detected as sub - millimeter sources with no optical counterparts . .
And you have already written the first three sentences of the full article: one of the most important discoveries from extragalactic observations at mid- and far - infrared wavelengths has been the identification of a class of `` luminous infrared galaxies '' ( ligs ) , objects that emit more energy in the infrared ( @xmath15500@xmath2 ) than at all other wavelengths combined ( see @xcite for a comprhensive review ) .
the first all - sky survey at far - infrared wavelengths carried out in 1983 by the _ infrared astronomical satellite _ ( _ iras _ ) resulted in the detection of tens of thousands of galaxies , the vast majority of which were too faint to have been included in previous optical catalogs .
it is now clear that part of the reason for the large number of detections is the fact that the majority of the most luminous galaxies in the universe are extremely dusty ..
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previous assumptions , based primarily on optical observations , about the relative distributions of different types of luminous galaxies e.g .
starbursts , seyferts , and quasi - stellar objects ( qsos)need to be revised .
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11,898 |
Suppose that you have an abstract for a scientific paper: we report on a simple oven - loaded magneto - optical trap ( mot ) apparatus for the creation of both molecular bose - einstein condensates ( mbec ) and degenerate fermi gases ( dfgs ) of lithium .
the apparatus does not require a zeeman slower or a 2d mot nor does it require any separation or differential pumping between the effusive atom source and the science chamber .
the result is an exceedingly simple , inexpensive , and compact vacuum system ideal for miniaturization .
we discuss our work in the context of other realizations of quantum degenerate gases by evaporation in optical dipole traps and illustrate that our apparatus meets the key requirements of atom number and trap lifetime . with this system ,
we also demonstrate the production of a mbec , and we use it to observe the pairing gap of a strongly interacting two - component dfg in the bec - bcs crossover regime . .
And you have already written the first three sentences of the full article: since the first achievement of bose - einstein condensation ( bec ) in atomic gases , techniques for the production of quantum degenerate gases ( qdgs ) from laser cooled atoms have been continually improved , refined and simplified . because the phase space density achievable with laser cooling is limited by light - induced , density - dependent collisional losses and by the temperature limits of laser cooling , qdgs are typically made in a two step process .
the only exception to this is sr which has been directly laser cooled to degeneracy @xcite .
after laser cooling , the ensemble is transferred into a conservative potential formed by an off - resonant magnetic or optical field and forced evaporative cooling is performed to achieve the requisite temperatures and densities ..
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efficient evaporative cooling relies on rapid thermalization of the atoms in the trap and requires that the evaporation time be shorter than the lifetime of a particle in the trap .
since the speed of evaporation is limited by the elastic collision rate , @xmath0 ( where @xmath1 is the atomic density , @xmath2 is the elastic collision cross section , and @xmath3 is the average collision velocity ) , this requirement places simultaneous constraints on the minimum initial atom number loaded into the conservative trap and on the quality of the vacuum system because the density of room - temperature , background - gas particles sets an upper bound on the trap lifetime .
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11,899 |
Suppose that you have an abstract for a scientific paper: we propose an indicator to measure the degree to which a particular news article is novel , as well as an indicator to measure the degree to which a particular news item attracts attention from investors .
the novelty measure is obtained by comparing the extent to which a particular news article is similar to earlier news articles , and an article is regarded as novel if there was no similar article before it . on the other hand ,
we say a news item receives a lot of attention and thus is highly topical if it is simultaneously reported by many news agencies and read by many investors who receive news from those agencies .
the topicality measure for a news item is obtained by counting the number of news articles whose content is similar to an original news article but which are delivered by other news agencies . to check the performance of the indicators ,
we empirically examine how these indicators are correlated with intraday financial market indicators such as the number of transactions and price volatility .
specifically , we use a dataset consisting of over 90 million business news articles reported in english and a dataset consisting of minute - by - minute stock prices on the new york stock exchange and the nasdaq stock market from 2003 to 2014 , and show that stock prices and transaction volumes exhibited a significant response to a news article when it is novel and topical .
novelty ; topicality ; exogenous shocks ; financial markets ; business news ; .
And you have already written the first three sentences of the full article: financial markets can be regarded as a non - equilibrium open system .
understanding how they work remains a great challenge to researchers in finance , economics , and statistical physics .
fluctuations in financial market prices are sometimes driven by endogenous forces and sometimes by exogenous forces ..
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business news is a typical example of exogenous forces .
casual observation indicates that stock prices respond to news articles reporting on new developments concerning companies circumstances .
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