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3,900 | Suppose that you have an abstract for a scientific paper: eub@xmath0 is a low carrier density ferromagnet which exhibits large magnetoresistance , positive or negative depending on temperature .
the formation of magnetic polarons just above the magnetic critical temperature has been suggested by spin - flip raman scattering experiments .
we find that the fact that eub@xmath0 is a semimetal has to be taken into account to explain its electronic properties , including magnetic polarons and magnetoresistance . .
And you have already written the first three sentences of the full article: europium hexaboride is part of the large and heterogeneous class of materials that exhibit colossal magnetoresistance ( cmr ) .
the ferromagnetic transition in eub@xmath0 is accompanied by a dramatic change in resistivity .
there is a large body of experimental data available on the magnetic and electric properties , but a thorough understanding is lacking ..
Please generate the next two sentences of the article | eub@xmath0 has a cubic unit cell with eu - ions at its vertices and a boron octahedron at its center .
the material is ferromagnetic and shows two magnetic transitions : at @xmath1k and at @xmath2k @xcite . |
3,901 | Suppose that you have an abstract for a scientific paper: to explore the difference between the most two recent solar minima , we analyze the in - situ _ ace _ and _ ulysses _ observations and examine the distributions of the three types of solar wind ( streamer - stalk - associated wind , wind from outside the streamer stalk that can be associated , in part , with coronal holes , and interplanetary coronal mass ejections ) .
we use the taxonomy provided by @xcite to identify the three types of solar wind .
we then map the in - situ observations to the 2.5 solar radii surface . with the aid of the potential - field - source - surface model ( pfss )
, we calculate the normal distance from the solar wind `` foot point '' to the local helisopheric current sheet on that surface .
we find that the source region of the streamer stalk wind is narrower ( @xmath0 ) compared to the previous minimum ( @xmath1 ) .
the area outside the streamer stalk is accordingly larger , but the magnetic field strength is observed to be lower , with the result that the total amount of the magnetic open flux from the outside of streamer stalk region is conserved in the two successive solar minima .
the implications of the conservation of open magnetic flux for models of the behavior of the solar magnetic field are discussed . .
And you have already written the first three sentences of the full article: there are three distinct types of solar wind identified by @xcite .
first , there is relatively high coronal electron temperature wind originating from loops in the streamer stalk region @xcite .
second , there is solar wind from the outside of this region ..
Please generate the next two sentences of the article | this wind includes coronal hole wind that has relatively low coronal electron temperatures and high wind speeds , as well as slower solar wind with lower coronal electron temperatures than the stream stalk region .
the third type of solar wind is the transient interplanetary coronal mass ejections ( icmes ) which are caused by the coronal mass ejections ( cmes ) @xcite . |
3,902 | Suppose that you have an abstract for a scientific paper: in a multiply connected space , the two twins of the special relativity twin paradox move with constant relative speed and meet a second time without acceleration .
the twins situations appear to be symmetrical despite the need for one to be younger due to time dilation . here
, the suggestion that the apparent symmetry is broken by homotopy classes of the twins worldlines is reexamined using space - time diagrams .
it is found that each twin finds her own spatial path to have zero winding index and that of the other twin to have unity winding index , i.e. the twins worldlines relative homotopy classes are symmetrical .
although the twins apparent symmetry is in fact broken by the need for the non - favoured twin to non - simultaneously identify spatial domain boundaries , the non - favoured twin _ can not _ detect her disfavoured state if she only measures the homotopy classes of the two twins projected worldlines , contrary to what was previously suggested .
we also note that for the non - favoured twin , the fundamental domain can be chosen by identifying time boundaries ( with a spatial offset ) instead of space boundaries ( with a temporal offset ) .
reference systems time cosmology : theory .
And you have already written the first three sentences of the full article: since the confirmation by wilkinson microwave anisotropy probe ( wmap ) observations of the cosmic microwave background that the large scale ( @xmath0 in comoving units ) auto - correlation function of temperature fluctuations is close to zero [ fig . 16 , @xcite ( orthogonally projected spatial scale ) ; fig . 1 of @xcite ( non - projected spatial scale ) ] and difficult to reconcile with a standard cosmic concordance model ( 7 of @xcite
; though see also @xcite ) there has recently been considerable observational interest in understanding multiply connected models of the universe .
the poincar dodecahedral space ( pds ) has been proposed as a better model of the 3-manifold of comoving space rather than an `` infinite '' flat space ( e.g. @xcite ; though see also @xcite ) ..
Please generate the next two sentences of the article | curvature estimates are consistent with the model : analysis of the 3-year wmap data @xcite results in best estimates of the total density parameter @xmath1 ( when combined with hst key project on @xmath2 data ) and @xmath3 ( when combined with supernova legacy survey data ) , or together with the third , fourth and fifth acoustic peaks , as estimated from their observations near the south galactic pole using the arcminute cosmology bolometer array receiver ( acbar ) , @xmath4 is obtained @xcite , consistently with that expected from the pds analyses , which require positive curvature in this range of @xmath5 values .
it has also recently become noticed that global topology in a universe containing density perturbations can , in principle , have at least some effect on the metric , even though the effect is expected to be small . at the present epoch , in the case of a @xmath6 model of fundamental lengths which are slightly unequal by a small fraction @xmath7 |
3,903 | Suppose that you have an abstract for a scientific paper: squeezing of atomic resonance fluorescence is shown to be optimized by a properly designed environment , which can be realized by a quasi - resonant cavity .
optimal squeezing is achieved if the atomic coherence is maximized , corresponding to a pure atomic quantum state .
the atomic - state purification is achieved by the backaction of the cavity field on the atom , which increases the atomic coherence and decreases the atomic excitation . for realistic cavities ,
the coupling of the atom to the cavity field yields a purity of the atomic state of more than 99% .
the fragility of squeezing against dephasing is substantially reduced in this scenario , which may be important for various applications . [
[ introduction . ] ] introduction .
+ + + + + + + + + + + + + a single atom and its coupling to the electromagnetic field is a system of fundamental interest for the understanding of the quantum phenomena of light and matter . it was predicted that a driven two - level atom emits antibunched light @xcite , which can not be described by the classical maxwell theory .
the first experimental demonstration of this effect was based on the resonance fluorescence of an atomic beam @xcite . in a related experiment
it was demonstrated that a sub - poissonian photon statistics may occur @xcite .
later on , photon antibunching could be demonstrated with single trapped ions @xcite .
squeezing was predicted to occur in the single - atom resonance fluorescence @xcite .
it can also be realized in the fluorescence of many atoms , via regular arrangement of the atoms @xcite , detection in the forward direction with respect to the pump - beam @xcite , and bistability in a strong driving field @xcite .
the latter two cases , could be experimentally demonstrated @xcite . squeezing in single - atom resonance fluorescence
could not be observed yet .
based on homodyne correlation measurements with a weak local oscillator , an efficient measurement technique was proposed @xcite , which is....
And you have already written the first three sentences of the full article: [ [ numerical - calculations . ] ] numerical calculations .
+ + + + + + + + + + + + + + + + + + + + + + + starting from the master equations , we can formulate equations of motion for the elements of the density matrix @xmath81 with the first index being the cavity photon number and the second being the atomic excitation ( @xmath2 ) .
the explicit equations can be written as @xmath82\varrho_{n,1;m,1}-ig[\sqrt{n}\varrho_{n-1,2;m,1}-\sqrt{m}\varrho_{n,1;m-1,2}]\nonumber\\ & -i\omega_\text r[\varrho_{n,2;m,1}-\varrho_{n,1;m,2}]+\gamma\varrho_{n,2;m,2}+\kappa\sqrt{(n+1)(m+1)}\varrho_{n+1,1;m+1,1},\\ \dot\varrho_{n,1;m,2}=&[i(\delta_\text a-(n - m)\delta_\text c)-\tfrac{\gamma+\kappa(n+m)}{2}]\varrho_{n,1;m,2}-ig[\sqrt{n}\varrho_{n-1,2;m,2 } -\sqrt{m+1}\varrho_{n,1;m+1,1}]\nonumber\\ & - i\omega_\text r(\varrho_{n,2;m,2}-\varrho_{n,1;m,1})+\kappa\sqrt{(n+1)(m+1)}\varrho_{n+1,1;m+1,2},\\ \dot\varrho_{n,2;m,1}=&-[i(\delta_\text a+(n - m)\delta_\text c)+\tfrac{\gamma+\kappa(n+m)}{2}]\varrho_{n,2;m,1}-ig[\sqrt{n+1}\varrho_{n+1,1;m,1 } -\sqrt{m}\varrho_{n,2;m-1,2}]\nonumber\\ & - i\omega_\text r(\varrho_{n,1;m,1}-\varrho_{n,2;m,2})+\kappa\sqrt{(n+1)(m+1)}\varrho_{n+1,2;m+1,1},\\ \dot\varrho_{n,2;m,2}=&-[i\delta_\text c(n - m)+\gamma+\tfrac{\kappa}{2}(n+m)]\varrho_{n,2;m,2}-ig[\sqrt{n+1}\varrho_{n+1,1;m,2}-\sqrt{m+1}\varrho_{n,2;m+1,1}]\nonumber\\ & -i\omega_\text r(\varrho_{n,1;m,2}-\varrho_{n,2;m,1})+\kappa\sqrt{(n+1)(m+1)}\varrho_{n+1,2;m+1,2}.\end{aligned}\ ] ] we truncate the set of equations at a sufficiently large photon number @xmath83 . by varying @xmath83 ,.
Please generate the next two sentences of the article | the validity of the calculations can be checked .
using @xmath84 , we can eliminate one element of the main diagonal , in our case , we chose @xmath85 . |
3,904 | Suppose that you have an abstract for a scientific paper: we prove the uniqueness and non - degeneracy of positive solutions to a cubic nonlinear schrdinger ( nls ) type equation that describes nucleons .
the main difficulty stems from the fact that the mass depends on the solution itself . as an application
, we construct solutions to the @xmath0@xmath1 model , which consists of one dirac equation coupled to two klein - gordon equations ( one focusing and one defocusing ) . .
And you have already written the first three sentences of the full article: the purpose of this paper is to study the uniqueness and non - degeneracy of solutions to a nonlinear schdinger - type equation , arising from the minimization of the following energy functional @xmath2 under the mass constraint @xmath3 . here
@xmath4 is the positive part , @xmath5 is a 2-spinor that describes the quantum state of a nucleon ( a proton or a neutron ) , @xmath6 are the pauli matrices and @xmath7 .
the equation of interest is @xmath8 with @xmath9 the lagrange multiplier associated with the mass constraint ..
Please generate the next two sentences of the article | this equation can as well be written in the form of a system of two coupled dirac - like equations @xmath10 indeed , the above model can formally be deduced from a relativistic model involving one dirac particle coupled with two auxiliary classical fields ( the so - called _ @xmath11 model _ ) , in a specific non - relativistic limit that will be described in detail below . in this limit
, the equations for the classical fields can be solved explicitly , leading to the nonlinear system and the corresponding nonlinear energy functional , expressed in terms of @xmath12 only . |
3,905 | Suppose that you have an abstract for a scientific paper: we investigate the geometric properties of percolation clusters , by studying square - lattice bond percolation on the torus .
we show that the density of bridges and nonbridges both tend to 1/4 for large system sizes . using monte carlo simulations , we study the probability that a given edge is not a bridge but has both its loop arcs in the same loop , and find that it is governed by the two - arm exponent .
we then classify bridges into two types : branches and junctions .
a bridge is a _ branch _ iff at least one of the two clusters produced by its deletion is a tree .
starting from a percolation configuration and deleting the branches results in a _ leaf - free _ configuration , while deleting all bridges produces a bridge - free configuration . although branches account for @xmath0 of all occupied bonds , we find that the fractal dimensions of the cluster size and hull length of leaf - free configurations are consistent with those for standard percolation configurations . by contrast , we find that the fractal dimensions of the cluster size and hull length of bridge - free configurations are respectively given by the backbone and external perimeter dimensions .
we estimate the backbone fractal dimension to be @xmath1 . .
And you have already written the first three sentences of the full article: one of the main goals of percolation theory @xcite in recent decades has been to understand the geometric structure of percolation clusters .
considerable insight has been gained by decomposing the incipient infinite cluster into a _
backbone _ plus _ dangling bonds _ , and then further decomposing the backbone into _ blobs _ and _ red bonds _ @xcite . to define the backbone , one typically fixes two distant sites in the incipient infinite cluster , and defines the backbone to be all those occupied bonds in the cluster which belong to trails between the specified sites @xcite ..
Please generate the next two sentences of the article | the remaining bonds in the cluster are considered dangling .
similar definitions apply when considering spanning clusters between two opposing sides of a finite box @xcite ; this is the so - called _ busbar _ geometry . |
3,906 | Suppose that you have an abstract for a scientific paper: for any complex number @xmath0 , let @xmath1 denote the divisor function defined by @xmath2 for all @xmath3 , and define @xmath4 to be the range of @xmath5 .
we study the basic topological properties of the sets @xmath6 .
in particular , we determine the complex numbers @xmath0 for which @xmath6 is bounded and determine the isolated points of the sets @xmath6 . in the third section , we find those values of @xmath0 for which @xmath6 is dense in @xmath7 .
we also prove some results and pose several open problems about the closures of the sets @xmath6 when these sets are bounded .
.2 in 2010 _ mathematics subject classification _ : primary 11b05 ; secondary 11a25 . _
keywords : divisor function ; complex number ; range ; dense ; isolated point ; closure . _ .
And you have already written the first three sentences of the full article: throughout this article , we will let @xmath8 , @xmath9 , and @xmath10 denote the set of positive integers , the set of nonnegative integers , and the set of prime numbers , respectively . the lowercase letter @xmath11 will always denote
a prime number , and @xmath12 will denote the exponent of @xmath11 in the prime factorization of a positive integer @xmath13 .
furthermore , for any nonzero complex number @xmath14 , we let @xmath15 denote the principal argument of @xmath14 with the convention that @xmath16 . for any complex number @xmath0 ,.
Please generate the next two sentences of the article | the divisor function @xmath17 is the arithmetic function defined by @xmath2 for all @xmath3 .
the function @xmath5 is a multiplicative arithmetic function that satisfies @xmath18 for all primes @xmath11 and positive integers @xmath19 . of course , if @xmath20 , then we may write @xmath21 . |
3,907 | Suppose that you have an abstract for a scientific paper: in this letter recent developments are shown in experimental and theoretical physics which brings into question the validity of general relativity .
this letter emphasizes the construction of a fractal @xmath0 spacetime , in @xmath1-dimensions in order to formalize a physical and consistent theory of ` quantum gravity . '
it is then shown that a ` quantum gravity ' effect could arise by means of the strong equivalence principle . which is made possible through a pressure of the form @xmath2 . where it is seen that nuclear pressures can be added to the gravitational field equations by means of twistor spaces .
* keywords : * fractal geometry , new relativity , quantum vacuum , epr , zero - point field , quantum gravity , mach s principle , holographic principle , fermat s last theorem , alternative gravity , bohmian mechanics .
pacs numbers .
4.50 , 4.60 .
And you have already written the first three sentences of the full article: recently the validity of general relativity ( gr ) has been brought to question by yilmaz , et al . although such interpretations allow for gravitation to be mathematically consistent and singularity free .
such revisions fail to describe the behavior of test particles as adequately as gr , elevating gr as the correct theory .
today certain questions about gr remain relevant , such as how does it relate to vacuum energy and quantum mechanics in general ..
Please generate the next two sentences of the article | it has been shown in previous works that gr remains self consistent when including the quantum vacuum , or zero - point field .
however , the search for a self consistent theory of quantum gravity , " remains a major theoretical challenge today . among the theoretical arguments against the standard interpretation of gr |
3,908 | Suppose that you have an abstract for a scientific paper: models for gamma ray burst afterglows envisage an hyper relativistic fireball that is decelerated in the ambient medium around the explosion site .
this interaction produces a shock wave which amplifies the magnetic field and accelerates electrons to relativistic energies , setting the conditions for an efficient production of synchrotron photons . if produced in a region of large
scale ordered magnetic field , synchrotron radiation can be highly polarized .
the optical transient associated with grb 990510 was observed @xmath0 hr after the event and linear polarization in the @xmath1 band was measured at a level of @xmath2 .
this is the first detection of linear polarization in the optical afterglow of a gamma ray burst .
we exclude that this polarization is due to dust in the interstellar material , either in our galaxy or in the host galaxy of the gamma ray burst .
these results provide important new evidence in favor of the synchrotron origin of the afterglow emission , and constrains the geometry of the fireball and/or magnetic field lines . .
And you have already written the first three sentences of the full article: grb 990510 was detected by batse on - board the compton gamma ray observatory and by the _
beppo_sax gamma ray burst monitor and wide field camera on 1999 may 10.36743 ut ( @xcite , dadina et al .
its fluence ( 2.5@xmath3 erg @xmath4 above 20 kev ) was relatively high ( @xcite ) ..
Please generate the next two sentences of the article | follow up optical observations started @xmath5 hr later and revealed an @xmath6 ( @xcite ) optical transient , ot ( vreeswijk et al .
1999a ) , at the coordinates ( j2000 ) @xmath7 , @xmath8 ( @xcite ) ( galactic coordinates @xmath9 , @xmath10 ) . |
3,909 | Suppose that you have an abstract for a scientific paper: recently andrei teleman considered instanton moduli spaces over negative definite four - manifolds @xmath0 with @xmath1 .
if @xmath2 is divisible by four and @xmath3 a gauge - theoretic invariant can be defined ; it is a count of flat connections modulo the gauge group .
our first result shows that if such a moduli space is non - empty and the manifold admits a connected sum decomposition @xmath4 then both @xmath5 and @xmath6 are divisible by four ; this rules out a previously naturally appearing source of @xmath7-manifolds with non - empty moduli space .
we give in some detail a construction of negative definite @xmath7-manifolds which we expect will eventually provide examples of manifolds with non - empty moduli space . .
And you have already written the first three sentences of the full article: recently andrei teleman considered moduli spaces of projectively anti - selfdual instantons in certain hermitian rank-2 bundles over a closed oriented 4-manifold with negative definite intersection form @xcite .
these play a role in his classification program on class vii surfaces @xcite@xcite
. however , in certain situations the instanton moduli spaces involved consist of projectively flat connections and therefore have very interesting topological implications . in this article.
Please generate the next two sentences of the article | we will study these ` casson - type ' moduli spaces .
suppose @xmath8 is a hermitian rank-2 bundle with first chern - class a ( minimal ) characteristic vector @xmath9 of the intersection form . |
3,910 | Suppose that you have an abstract for a scientific paper: the problem of estimating an unknown phase @xmath0 using two - level probes in the presence of unital phase - covariant noise and using finite resources is investigated .
we introduce a simple model in which the phase - imprinting operation on the probes is realized by a unitary transformation with a randomly sampled generator .
we determine the optimal phase sensitivity in a sequential estimation protocol , and derive a general ( tight - fitting ) lower bound .
the sensitivity grows quadratically with the number of applications @xmath1 of the phase - imprinting operation , then attains a maximum at some @xmath2 , and eventually decays to zero .
we provide an estimate of @xmath2 in terms of accessible geometric properties of the noise and illustrate its usefulness as a guideline for optimizing the estimation protocol .
the use of passive ancillas and of entangled probes in parallel to improve the phase sensitivity is also considered .
we find that multi - probe entanglement may offer no practical advantage over single - probe coherence if the interrogation at the output is restricted to measuring local observables . .
And you have already written the first three sentences of the full article: advances in metrology are pivotal to improve measurement standards , to develop ultrasensitive technologies for defence and healthcare , and to push the boundaries of science , as demonstrated by the detection of gravitational waves @xcite . in a typical metrological setting
, an unknown parameter @xmath0 is dynamically imprinted on a suitably prepared probe .
we can think e.g. of a two - level spin undergoing a unitary phase shift @xmath3 . by subsequently interrogating the probe.
Please generate the next two sentences of the article | one builds an estimate @xmath4 for the parameter @xcite .
the corresponding mean - square error @xmath5 can be reduced , for instance , by using @xmath1 uncorrelated identical probes . in that case |
3,911 | Suppose that you have an abstract for a scientific paper: we compare the central mass concentration of cold dark matter halos found in cosmological n - body simulations with constraints derived from the milky way disk dynamics and from the tully - fisher relation . for currently favored values of the cosmological parameters ( @xmath0 ; @xmath1 ;
@xmath2 ; cobe- and cluster abundance - normalized @xmath3 ; big - bang nucleosynthesis @xmath4 ) , we find that halos with circular velocities comparable to the rotation speed of the galaxy have typically _ three times _ more dark matter inside the solar circle than inferred from observations of galactic dynamics .
such high central concentrations of dark matter on the scale of galaxy disks also imply that stellar mass - to - light ratios much lower than expected from population synthesis models must be assumed in order to reproduce the zero - point of the tully - fisher relation . indeed , even under the extreme assumption that _ all _ baryons in a dark halo are turned into stars , disks with conventional @xmath5-band stellar mass - to - light ratios ( @xmath6 ) are about two magnitudes fainter than observed at a given rotation speed .
we examine several modifications to the @xmath7cdm model that may account for these discrepancies and conclude that agreement can only be accomplished at the expense of renouncing other major successes of the model . reproducing
the observed properties of disk galaxies thus appears to demand substantial revision to the currently most successful model of structure formation . .
And you have already written the first three sentences of the full article: over the past few years , cosmological models based on the paradigm of an inflationary universe dominated by cold dark matter ( cdm ) have proved remarkably successful at explaining the origin and evolution of structure in the universe .
the free parameters of astrophysical relevance in this modeling are surprisingly few : the current rate of universal expansion , @xmath8 ; the mass density parameter , @xmath9 ; the primordial baryon abundance , @xmath4 ; and the overall normalization of the power spectrum of initial density fluctuations , @xmath3 . over the past few years
, limits on the values allowed for these parameters have been consistently refined by improved observational techniques and theoretical insight , and it is widely accepted that a new `` standard '' model has emerged as the clear front - runner amongst competing models of structure formation ..
Please generate the next two sentences of the article | this model , which we shall call `` standard '' @xmath7cdm , or s@xmath7cdm for short , envisions an eternally expanding universe with the following properties ( bahcall et al 1999 ) : ( i ) matter makes up at present less than about a third of the critical density for closure ( @xmath0 ) ; ( ii ) a non - zero cosmological constant restores the flat geometry predicted by most inflationary models of the early universe ( @xmath10 ) ; ( iii ) the present rate of universal expansion is @xmath11 km s@xmath12 mpc@xmath12 ( @xmath13 km s@xmath12 mpc@xmath14 ) ; ( iv ) baryons make up a very small fraction of the mass of the universe ( @xmath15 ) ; and ( v ) the present - day rms mass fluctuations on spheres of radius 8 @xmath16 mpc is of order unity ( @xmath17 ) .
the s@xmath7cdm model is consistent with an impressive array of well - established fundamental observations : the age of the universe as measured from the oldest stars ( e.g. , chaboyer et al 1998 ) , the extragalactic distance scale as measured by distant cepheids ( e.g. , madore et al 1998 ) ; the primordial abundance of the light elements ( e.g. , schramm & turner 1998 ) , the baryonic mass fraction of galaxy clusters ( e.g. , white et al 1993 ) , the amplitude of the cosmic microwave background fluctuations measured by cobe ( e.g. , lawrence , scott & white 1999 ) , the present - day abundance of massive galaxy clusters ( e.g. , eke , cole & frenk 1996 ) , the shape and amplitude of galaxy clustering patterns ( e.g. , wu , lahav & rees 1999 ) , the magnitude of large - scale coherent motions of galaxy systems ( e.g. , strauss & willick 1995 , zaroubi et al 1997 ) , and the world geometry inferred from observations of distant type ia supernovae ( e.g. , perlmutter et al 1999 , garnavich et al 1998 ) , among others . because its major parameters are fixed , s@xmath7cdm is an eminently falsifiable model whose predictive power may be used to ascertain its validity on scales different from those used to tune the model . |
3,912 | Suppose that you have an abstract for a scientific paper: we propose a new camera - based method of robot identification , tracking and orientation estimation .
the system utilises coloured lights mounted in a circle around each robot to create unique colour sequences that are observed by a camera .
the number of robots that can be uniquely identified is limited by the number of colours available , @xmath0 , the number of lights on each robot , @xmath1 , and the number of consecutive lights the camera can see , @xmath2 . for a given set of parameters
, we would like to maximise the number of robots that we can use .
we model this as a combinatorial problem and show that it is equivalent to finding the maximum number of disjoint @xmath1-cycles in the de bruijn graph @xmath3 .
we provide several existence results that give the maximum number of cycles in @xmath3 in various cases .
for example , we give an optimal solution when @xmath4 .
another construction yields many cycles in larger de bruijn graphs using cycles from smaller de bruijn graphs : if @xmath3 can be partitioned into @xmath1-cycles , then @xmath5 can be partitioned into @xmath6-cycles for any divisor @xmath7 of @xmath1 .
the methods used are based on finite field algebra and the combinatorics of words .
= 1 graph theory , robot network , de bruijn graph , graph decomposition , pose estimation , linear feedback shift register .
And you have already written the first three sentences of the full article: a _ robot network _ is a collection of robots working together to achieve a common goal . in order for the robots in such a network to cooperate effectively ,
the ability to observe each other s movements is critical . in many applications , distinguishing between the robots is necessary , but is usually difficult because the robots are identical .
for example , in a _ formation control _ system , robots collectively arrange themselves in some fixed geometric configuration @xcite ..
Please generate the next two sentences of the article | each robot controls its position relative to its neighbours . to achieve this
, the robot must continuously measure the position and determine the identity of each neighbour . |
3,913 | Suppose that you have an abstract for a scientific paper: we present optical integral field spectroscopy of the h@xmath0-luminous ( @xmath1 ) central cluster galaxies in the cores of the cooling flow clusters a1664 , a1835 , a2204 and zw8193 . from the [ nii]+h@xmath0 complex in these moderate resolution ( 70150 ) spectra we derive two - dimensional views of the distribution and kinematics of the emission line gas , and further diagnostics from the [ sii ] and [ oi ] lines
. the h@xmath0 emission shows a variety of disturbed morphologies , ranging from smooth but distorted to clumpy and filamentary , with velocity gradients and splittings of several hundred on spatial scales of 20 or more . despite the small sample size
, there are some generic features .
the most disturbed h@xmath0 emission appears to be associated with secondary galaxies within 1020 ( projected ) of the central galaxy and close in velocity to the h@xmath0 .
the global h@xmath0 kinematics match those of the co(1 - 0 ) emission in single - dish data .
the [ nii]/h@xmath0 , [ sii]/h@xmath0 and [ oi]/h@xmath0 ratios vary little with position , local h@xmath0 surface brightness or between clusters .
we propose that the h@xmath0 and co emission arise in molecular clouds heated by a starburst , and that the latter has been triggered by interaction with a secondary galaxy .
such co emission is known to trace massive ( @xmath2 ) compact ( @xmath3 ) reservoirs of cool molecular gas , and it is plausible that an infalling galaxy would disturb this gas , distorting the h@xmath0 morphology and initiating widespread star formation .
we also examine the role of cloud - cloud collisions in the undisturbed molecular gas reservoir , and suggest that they might be an important source of excitation for the emission line gas in the cores of lower h@xmath0 luminosity clusters with less intense star formation . #
1to 0pt#1 # 1 # 1 to size # 1 to size = cmr10 scaled2 = cmbx10 scaled2 = cmti10 scaled2 ps .
2 = 6truein galaxies : clusters : individual : a1664 , a1835 ,....
And you have already written the first three sentences of the full article: in recent years our understanding of the x - ray cooling flow phenomenon in galaxy cluster cores has been revolutionised . throughout most of the 1980s and 1990s
, x - ray observations suggested that gas in the central 100 is cooling out at rates of up to several hundred solar masses per year , but the lack of evidence for a reservoir of cooled gas led to heated debate ( summarised by fabian 1994 ) over this interpretation of the x - ray data .
results from _ xmm - newton _ and _ chandra _ have since led to a sharp downward revision in x - ray cooling rates ( e.g. schmidt , allen & fabian 2001 ) and also reveal a strong deficit of line emission from gas cooling below @xmath4 ( peterson et al ..
Please generate the next two sentences of the article | the implication is that x - ray cooling is quenched , for which numerous mechanisms have been proposed , including : rapid mixing of hot and cold phases , inhomogeneously distributed metals in the intracluster medium ( fabian et al .
2001,2002 ) ; active galactic nucleus ( agn ) heating by jets ( brggen & kaiser 2003 ) and sound waves ( fabian et al . |
3,914 | Suppose that you have an abstract for a scientific paper: we present sensitivity limits on the coefficients of a dimension6 effective lagrangian that parametrizes the possible effects of new physics beyond the standard model .
our results are based on the study of the process @xmath0 at lep2 and nlc energies . in our calculations , we include _ all _ the new anomalous interactions , involving vector and higgs bosons , and take into account the standard model irreducible background .
we analyse the impact of these new interactions on the total cross section , including the effects of the initial electron and final @xmath1 polarizations .
we then focus on the operators that will not be constrained by the @xmath2 process , obtaining limits based on the photon energy distribution . .
And you have already written the first three sentences of the full article: one of the main physics goals of lep2 and future @xmath3 colliders is to directly test the gauge nature of couplings among the electroweak gauge bosons .
the process with largest cross section at lep2 involving these couplings is the @xmath1pair production , @xmath4 , which is sensitive to the trilinear @xmath5 and @xmath6 couplings .
the measurement of these couplings and the sensitivity to possible deviations from the standard model ( sm ) predictions have been extensively studied in the recent years @xcite ..
Please generate the next two sentences of the article | the most general phenomenological parametrization for these couplings @xcite can be achieved by means of an effective lagrangian @xcite that involves operators with dimension higher than four , containing the relevant fields at low energies and respecting the symmetries of the standard model .
the effective lagrangian approach is a model independent way to describe new physics that can occur at an energy scale @xmath7 much larger than the scale where the experiments are performed . |
3,915 | Suppose that you have an abstract for a scientific paper: the energy levels of two and three anyons in a two - dimensional parabolic quantum dot and a perpendicular magnetic field are computed as power series in @xmath0 , where @xmath1 is the angular momentum .
the particles interact repulsively through a coulombic ( @xmath2 ) potential . in the two - anyon problem , the reached accuracy is better than one part in @xmath3 . for three anyons ,
we study the combined effects of anyon statistics and coulomb repulsion in the `` linear '' anyonic states . .
And you have already written the first three sentences of the full article: recent developments in semiconductor technology ( e.g. mbe and electron lithography ) opened the possibility to create totally confined electron systems , the so called artificial atoms or quantum dots @xcite .
this is one of the examples of present - day - physics interest in confined finite systems , among which one can mention also the atomic and electronic traps@xcite , and the condensation of confined bosons@xcite .
quantum dots exhibit very interesting properties like the possibility of varying their parameters ( number of electrons , applied fields , dot s geometry , temperature ) over a wide range , the observation of conductance oscillations@xcite and kohn s theorem@xcite , etc ..
Please generate the next two sentences of the article | theoretically , these systems have been studied mainly with the help of numerical methods . however
, analytic approaches have proven to work extremely well providing , at the same time , a qualitative understanding of the quantum dynamics . among these approaches one can mention the semiclassical quantisation@xcite , regularised perturbation theory@xcite , pade approximant techniques@xcite , and the @xmath4-expansion@xcite . |
3,916 | Suppose that you have an abstract for a scientific paper: the temporal and spectral analysis of 9 bright x - ray flares out of a sample of 113 flares observed by _ swift _ reveals that the flare phenomenology is strictly analogous to the prompt @xmath0-ray emission : high energy flare profiles rise faster , decay faster and peak before the low energy emission .
however , flares and prompt pulses differ in one crucial aspect : flares evolve with time .
as time proceeds flares become wider , with larger peak lag , lower luminosities and softer emission .
the flare spectral peak energy @xmath1 evolves to lower values following an exponential decay which tracks the decay of the flare flux .
the two flares with best statistics show higher than expected isotropic energy @xmath2 and peak luminosity @xmath3 when compared to the @xmath4 and @xmath5 prompt correlations .
@xmath1 is found to correlate with @xmath6 within single flares , giving rise to a time resolved @xmath7 .
like prompt pulses , flares define a lag - luminosity relation : @xmath8 .
the lag - luminosity is proven to be a fundamental law extending @xmath95 decades in time and @xmath95 in energy .
moreover , this is direct evidence that grb x - ray flares and prompt gamma - ray pulses are produced by the same mechanism .
finally we establish a flare- afterglow morphology connection : flares are preferentially detected superimposed to one - break or canonical x - ray afterglows .
[ firstpage ] gamma - ray : bursts radiation mechanism : non - thermal x - rays .
And you have already written the first three sentences of the full article: the high temporal variability was one of the first properties to be attributed to the gamma - ray burst ( grb ) prompt emission in the @xmath0-ray energy band ( @xcite ) .
the advent of _ swift _ ( @xcite ) revealed that a highly variable emission characterises also the early time x - ray afterglows in the form of erratic flares .
this established the temporal variability as one of the key features in interpreting the grb phenomena ..
Please generate the next two sentences of the article | grb050502b and the x - ray flash 050406 ( @xcite ; @xcite ; @xcite ) provided the first examples of dramatic flaring activity superimposed to a smooth decay : in particular , grb050502b demonstrated that flares can be considerably energetic , with a 0.3 - 10 kev energy release comparable to the observed prompt fluence in the 15 - 150 kev band . thanks to the rapid re - pointing _ swift _ capability , it was later shown that flares are a common feature of the early x - ray afterglows , being present in the @xmath10 of x - ray light - curves ( @xcite , hereafter c07 ; @xcite , hereafter f07 ) . on the contrary , a convincing optical flare , counterpart to a detected x - ray flare is still lacking , suggesting that the detected optical afterglow contemporaneous to the high - energy flares is dominated by a different emission component ( see e.g. grb060904b , @xcite but see also @xcite where an optical flare was probably detected but , unfortunately , contemporaneous x - ray coverage is lacking ) . based on the temporal and spectral study of a statistical sample of x - ray flares within grbs , c07 and
f07 showed that the flares share common properties and that the flare phenomenology can be described using averaged properties ( see c07 and f07 and references therein ) : * the same grb can show multiple flares ( see e.g. grb051117a which contains a minimum of 11 structures in the first 1 ks of observation ) ; * the underlying continuum is consistent with having the same slope before and after the flare , suggesting that flares constitute a separate component in addition to the observed continuum ; * each flare determines a flux enhancement evaluated at the peak time @xmath11 between @xmath12 and @xmath13 , with a fluence that competes in some cases ( e.g. grb050502b ) with the prompt @xmath0-ray fluence . |
3,917 | Suppose that you have an abstract for a scientific paper: we study the 2-loop resummed propagator in hot @xmath0 theory .
the propagator has a cut along the whole real axis in the complex energy plane , but for small @xmath1 , the spectral density is sharply peaked around the plasmon . the dispersion relation and the width of the plasmon
are calculated at zero _ and _ finite momentum . at large momenta
the spectral width vanishes , and the plasmon looses its collectivity and behaves like a non - interacting free particle . -1 cm .
And you have already written the first three sentences of the full article: at high temperature @xmath2 and low momenta @xmath3 the effective degrees of freedom in any field theory are collective modes , bosonic plasmons " @xcite and fermionic `` plasminos '' @xcite .
even if the fundamental field theoretical degrees of freedom were massless , the collective modes possess a finite thermal " mass which is generated dynamically by the interactions among the fundamental degrees of freedom .
the thermal masses regulate ( some of ) the severe infrared divergences which the massless theory would otherwise develop at finite temperature due to the singularity of the bose distribution at zero momentum @xcite ..
Please generate the next two sentences of the article | the strong rise of the bose distribution at small momenta causes , for example , the transport properties ( viscosity , heat conduction ) of a hot plasma of massless fields to be dominated by the interaction between low - momentum collective modes @xcite .
the determination of their dispersion relation and their collisional width is therefore a necessary prerequisite for any microscopic calculation of the transport coefficients , for example using the kubo formulae @xcite . |
3,918 | Suppose that you have an abstract for a scientific paper: absolute proper motions for @xmath0 7.7 million objects were derived based on data from the south galactic cap @xmath1-band sky survey ( scuss ) and astrometric data derived from uncompressed digitized sky surveys that the space telescope science institute ( stsci ) created from the palomar and uk schmidt survey plates .
we put a great deal of effort into correcting the position- , magnitude- and color- dependent systematic errors in the derived absolute proper motions .
the spectroscopically confirmed quasars were used to test the internal systematic and random error of the proper motions .
the systematic errors of the overall proper motions in the scuss catalog are estimated as @xmath2 and @xmath3 for @xmath4 and @xmath5 , respectively .
the random errors of the proper motions in the scuss catalog are estimated independently as 4.2 and @xmath6 for @xmath4 and @xmath5 .
there is no obvious position- , magnitude- and color- dependent systematic errors of the scuss proper motions .
the random error of the proper motions goes up with the magnitude from about @xmath7 at @xmath8 to about @xmath9 at @xmath10 .
the proper motions of stars in scuss catalog are compared with those in the sdss catalog , and they are consistent well . .
And you have already written the first three sentences of the full article: a catalog of proper motions in the * international * celestial reference system ( icrs ) , with precise positions and proper motions as well as deep * limiting * magnitude , is important for * research * on the galactic structure , galactic kinematics and stellar * populations*. there are two methods to determine the absolute proper motions of stars based on the hypothesis that the proper motions of background galaxies are zero .
one is that all the observations obtained in different epochs are transformed into one reference position system using galaxies , and absolute proper motions are calculated directly .
for example , munn et al . (.
Please generate the next two sentences of the article | 2004 ) took this method to construct the improved sdss proper motion catalog combining usno - b ( monet et al .
2003 ) and sdss ( gunn et al . 1998 |
3,919 | Suppose that you have an abstract for a scientific paper: by careful analysis of the comparison map from a simplicial set to its image under kan s ex - infinity functor we obtain a new and combinatorial proof that it is a weak homotopy equivalence .
moreover , we obtain a presentation of it as a _
strong anodyne extension_. from this description we are able to quickly deduce some basic facts about ex - infinity and hence provide a new construction of the kan - quillen model structure on simplicial sets , which avoids the use of topological spaces or minimal fibrations . .
And you have already written the first three sentences of the full article: model categories were introduced in @xcite , in which a main example is @xmath0 , the category of simplicial sets .
the proof given is combinatorial but uses the theory of _ minimal fibrations _ , thus relies essentially on the axiom of choice and so is very much non - constructive .
another popular approach can be found in @xcite , where the category of simplicial sets is related to a category of spaces via a nerve - realization adjunction ..
Please generate the next two sentences of the article | we begin by introducing a new viewpoint on the trivial cofibrations , which amounts to the observation that many examples of trivial cofibrations are in fact _ strong anodyne extensions _ ,
i.e. relative cell complexes of horn inclusions ( not featuring retracts ) . |
3,920 | Suppose that you have an abstract for a scientific paper: we introduce a very general method for high - dimensional classification , based on careful combination of the results of applying an arbitrary base classifier to random projections of the feature vectors into a lower - dimensional space .
in one special case that we study in detail , the random projections are divided into non - overlapping blocks , and within each block we select the projection yielding the smallest estimate of the test error .
our random projection ensemble classifier then aggregates the results of applying the base classifier on the selected projections , with a data - driven voting threshold to determine the final assignment .
our theoretical results elucidate the effect on performance of increasing the number of projections .
moreover , under a boundary condition implied by the sufficient dimension reduction assumption , we show that the test excess risk of the random projection ensemble classifier can be controlled by terms that do not depend on the original data dimension .
the classifier is also compared empirically with several other popular high - dimensional classifiers via an extensive simulation study , which reveals its excellent finite - sample performance . .
And you have already written the first three sentences of the full article: supervised classification concerns the task of assigning an object ( or a number of objects ) to one of two or more groups , based on a sample of labelled training data .
the problem was first studied in generality in the famous work of @xcite , where he introduced some of the ideas of linear discriminant analysis ( lda ) , and applied them to his iris data set . nowadays ,
classification problems arise in a plethora of applications , including spam filtering , fraud detection , medical diagnoses , market research , natural language processing and many others ..
Please generate the next two sentences of the article | in fact , lda is still widely used today , and underpins many other modern classifiers ; see , for example , @xcite and @xcite .
alternative techniques include support vector machines @xcite , tree classifiers @xcite , kernel methods @xcite and nearest neighbour classifiers @xcite . |
3,921 | Suppose that you have an abstract for a scientific paper: we propose new diagnostics for circumstellar interaction in type iip supernovae ( sne iip ) by the detection of high velocity ( hv ) absorption features in h@xmath0 and hei 10830 lines during the photospheric stage . to demonstrate the method
, we compute the ionization and excitation of h and he in supernova ejecta taking into account time - dependent effects and x - ray irradiation .
we find that the interaction with a typical red supergiant wind should result in the enhanced excitation of the outer layers of unshocked ejecta and the emergence of corresponding hv absorption , i.e. a depression in the blue absorption wing of h@xmath0 and a pronounced absorption of hei 10830 at a radial velocity of about @xmath1 km s@xmath2 .
we identify hv absorption in h@xmath0 and hei 10830 lines of sn 1999em and in h@xmath0 of sn 2004dj as being due to this effect .
the derived mass loss rate is close to @xmath3 yr@xmath2 for both supernovae , assuming a wind velocity 10 km s@xmath2 .
we argue that , in addition to the hv absorption formed in the unshocked ejecta , spectra of sn 2004dj and sn 1999em show a hv notch feature that is formed in the cool dense shell ( cds ) modified by the rayleigh - taylor instability . the cds results from both shock breakout and radiative cooling of gas that has passed through the reverse shock wave .
the notch becomes dominant in the hv absorption during the late photospheric phase , @xmath4 d. the wind density deduced from the velocity of the cds is consistent with the wind density found from the hv absorption produced by unshocked ejecta . .
And you have already written the first three sentences of the full article: the link between a certain type iip supernova ( sn iip ) and its main - sequence progenitor is poorly known despite the widely accepted view that these supernovae arise from the initial mass range of @xmath5 ( e.g. , * ? ? ?
the primary reasons for the uncertainty in this field are the small number of presupernova ( pre - sn ) mass determinations and the uncertain amount of matter lost through winds , presumably dominated by the red supergiant ( rsg ) wind .
while the former is becoming well - studied , the latter uncertainty is related to our poor knowledge of the complicated physics of mass loss and the unsatisfactory situation with the empirical measurements of mass loss from rsgs . even for the most studied close massive rsg , betelgeuse ,.
Please generate the next two sentences of the article | the range of observational estimates is large : @xmath6 yr@xmath2 @xcite .
the situation for sne iip has some promise because the dominant mass loss at the rsg stage may be observed by the detection of circumstellar ( cs ) interaction at x - ray and radio wavelengths . |
3,922 | Suppose that you have an abstract for a scientific paper: n - body simulations are an important tool in the study of formation of large scale structures .
much of the progress in understanding the physics of galaxy clustering and comparison with observations would not have been possible without n - body simulations . given the importance of this tool , it is essential to understand its limitations as ignoring these can easily lead to interesting but unreliable results . in this paper
we study the limitations due to the finite size of the simulation volume . in an earlier work we proposed a formalism for estimating the effects of a finite box - size on physical quantities and applied it to estimate the effect on the amplitude of clustering , mass function . here , we extend the same analysis and estimate the effect on skewness and kurtosis in the perturbative regime .
we also test the analytical predictions from the earlier work as well as those presented in this paper .
we find good agreement between the analytical models and simulations for the two point correlation function and skewness .
we also discuss the effect of a finite box size on relative velocity statistics and find the effects for these quantities scale in a manner that retains the dependence on the averaged correlation function @xmath0 .
methods : n - body simulations , numerical
gravitation
cosmology : theory , dark matter , large scale structure of the universe .
And you have already written the first three sentences of the full article: large scale structures like galaxies and clusters of galaxies are believed to have formed by gravitational amplification of small perturbations . for an overview and original references , see , e.g. , @xcite .
density perturbations are present at all scales that have been observed @xcite .
understanding the evolution of density perturbations for systems that have fluctuations at all scales is essential for the study of galaxy formation and large scale structures ..
Please generate the next two sentences of the article | the equations that describe the evolution of density perturbations in an expanding universe have been known for a long time and these are easy to solve when the amplitude of perturbations is much smaller than unity .
these equations describe the evolution of density contrast defined as @xmath1 . here |
3,923 | Suppose that you have an abstract for a scientific paper: in the quiet sun , magnetic fields are usually observed as small - scale magnetic elements , ` salt and pepper ' , covering the entire solar surface . by using 3d radiative mhd numerical simulations
we demonstrate that these fields are a result of local dynamo action in the top layers of the convection zone , where extremely weak ` seed ' magnetic fields can locally grow above the mean equipartition field ( e.g. , from a @xmath0 g ` seed ' field to more than 1000 g magnetic structures ) .
we find that the local dynamo action takes place only in a shallow , about 500 km deep , subsurface layer , from which the generated field is transported into deeper layers by convection downdrafts .
we demonstrate that the observed dominance of vertical magnetic fields at the photosphere and the horizontal fields above the photosphere can be explained by multi - scale magnetic loops produced by the dynamo . .
And you have already written the first three sentences of the full article: magnetic field generation is a key problem in understanding solar variability across wide range of scales .
modern high - resolution observations of the global magnetic field distribution , such as from hmi / sdo @xcite , and magnetic fields in selected areas by nst / bbso @xcite , sot / hinode @xcite and imax / sunrise @xcite demonstrate the complicated dynamics of magnetic fields and a tendency to self - organization . traditionally , the solar dynamo problem is divided according to two scales : the global dynamo , operating on the scale of the 22-year solar cycle and controlling the global field ( e.g. * ? ? ?
* ; * ? ? ?.
Please generate the next two sentences of the article | * ; * ? ? ?
* ) , and the local dynamo ( e.g. * ? ? ? |
3,924 | Suppose that you have an abstract for a scientific paper: low density parity check ( ldpc ) lattices are obtained from construction d and a family of nested binary ldpc codes .
we consider an special case of these lattices with one binary ldpc code as underlying code . this special case of ldpc lattices
can be obtained by lifting binary ldpc codes using construction a lattices .
the ldpc lattices were the first family of lattices which have efficient decoding in high dimensions .
we employ the encoding and decoding of the ldpc lattices in a cooperative transmission framework .
we establish two efficient shaping methods based on hypercube shaping and voronoi shaping , to obtain ldpc lattice codes .
then , we propose the implementation of block markov encoding for one - way and two - way relay networks using ldpc lattice codes .
this entails owning an efficient method for decomposing full - rate codebook into lower rate codebooks .
we apply different decomposition schemes for one - way and two - way relay channels which are the altered versions of the decomposition methods of low density lattice codes ( ldlcs ) . due to the lower complexity of the decoding for ldpc lattices comparing to ldlcs ,
the complexity of our schemes are significantly lower than the ones proposed for ldlcs .
the efficiency of the proposed schemes are presented using simulation results .
relay networks , lattice codes , block markov encoding . .
And you have already written the first three sentences of the full article: the last few years , cooperative transmission has become widely prominent with the increases in the size of communication networks . in wireless networks , the transmitted message from a node is heard not only by its intended receiver , but also by other neighbour nodes and those neighbour nodes can use the received signals to help transmission .
they bring a cooperative transmission by acting as relays .
the relay channel first introduced by van der meulen in @xcite and it consists of a source aiming to communicate with a destination with the help of a relay . in this case.
Please generate the next two sentences of the article | , we call the relay channel _ one - way relay channel _ or _ single relay channel_. in @xcite , cover and el gamal proposed the fundamental _ decode - forward _ ( df ) and _ compress - forward _ ( cf )
schemes for the one - way relay channels which achieve near capacity rates . in df scheme , |
3,925 | Suppose that you have an abstract for a scientific paper: qsos and radio - galaxies , together with the cmb , `` normal '' galaxies and clusters , represent the main source of information about the origin and evolution of the large scale structure .
they can be used either directly , as tracers of the density peaks , or as cosmic lighthouses , probing the universe along the line of sight with their conspicuous flow of photons .
observations of the qso and radio - galaxy clustering and its evolution interweave information about their nature and the cosmology that will hopefully be disentangled with the map and planck missions .
the amplitude of the qso clustering has been measured to be @xmath0 at @xmath1 and appears to increase with redshift .
these properties are consistent with a scenario in which the quasars , with a lifetime of @xmath2 , sparsely sample halos of mass greater than @xmath3 m@xmath4 .
radio - galaxies are found to cluster on similar scales .
the study of qso and radio - galaxy environments is in qualitative agreement with their clustering properties .
absorption - line systems observed in high - resolution spectra of qsos show structure , including voids / underdensities and overdensities , from the smallest scales to tens of mpc .
qso pairs , groups and lenses allow us to get a 3-d glimpse of the absorbers , providing invaluable information about their size , ionization , mass .
great progress in this field is expected from the new instrumentation coming into operation at the 8-m class telescopes .
much work remains to be done also at low redshift to clarify whether the absorption systems have a direct physical connection with galaxies or a significant fraction of them is caused by a truly intergalactic medium .
psfig 24.5 cm 16.5 cm -2.5 cm -2.2 cm invited review at the mpa / eso cosmology conference `` evolution of large - scale structure : from recombination to garching '' garching , germany , 2 - 7 august , 1998 . .
And you have already written the first three sentences of the full article: the first indications of qso clustering came from the observations of possible physical pairs of quasars around 1980 ( hazard 1979 , oort 1981 , margon 1981 , webster 1982 ) .
although the individual cases were of tantalizing interest , it was difficult to gain an appreciation of their true significance from a - posteriori statistics .
systematic searches began with the pioneering work of osmer ( 1981 ) and the first detection was obtained by shaver ( 1984 ) , using a large , inhomogeneous qso catalog ..
Please generate the next two sentences of the article | the surveys carried out to investigate the qso luminosity function ( lf ) before long provided statistically - well - defined samples with sufficient surface density and size for a study of the clustering on scales of a few tens of mpc ( shanks 1983 , 1987 ) .
the two - point correlation function ( tpcf ) and its fourier transform , the power - spectrum , have been applied as a standard approach to investigate the qso clustering , but other techniques have also been explored , such as counts in cells ( andreani 1994 , carrera 1998 ) , the minimal spanning tree ( graham 1995 ) , fractal analysis ( andreani 1991 ) and the friend - of - friend algorithm ( komberg 1996 ) . |
3,926 | Suppose that you have an abstract for a scientific paper: the interactions between holes in the hubbard model , in the low density , intermediate to strong coupling limit , are investigated by systematically improving mean field calculations .
the configuration interaction basis set is constructed by applying to local unrestricted hartree - fock configurations all lattice translations and rotations .
it is shown that this technique reproduces , correctly , the properties of the heisenberg model , in the limit of large u. upon doping , dressed spin polarons in neighboring sites have an increased kinetic energy and an enhanced hopping rate .
both effects are of the order of the hopping integral and lead to an effective attraction at intermediate couplings .
the numerical results also show that when more than two holes are added to the system , they do not tend to cluster , but rather hole pairs remain far appart .
hole
hole correlations are also calculated and shown to be in qualitative agreement with exact calculations for @xmath0 clusters .
in particular our results indicate that for intermediate coupling the hole hole correlation attains a maximum when the holes are in the same sublattice at a distance of @xmath1 times the lattice spacing , in agreement with exact results and the @xmath2@xmath3 model .
the method is also used to derive known properties of the quasiparticle band structure of isolated spin polarons . .
And you have already written the first three sentences of the full article: the nature of the low energy excitations in the hubbard model has attracted a great deal of attention .
it is well established that at half filling the ground state is an antiferromagnetic ( af ) insulator .
also , there exists conclusive evidence which indicates that antiferromagnetism is rapidly suppressed upon doping @xcite ..
Please generate the next two sentences of the article | close to half filling , a large amount of work suggests the existence of spin polarons , made of dressed holes , which propagate within a given sublattice with kinetic energy which in the strong coupling limit is of the order of @xmath4 @xcite , where @xmath2 is the hopping integral and @xmath5 the on site coulomb repulsion .
these results are consistent with similar calculations in the strong coupling , low doping limit of the hubbard model , the @xmath6 model@xcite . |
3,927 | Suppose that you have an abstract for a scientific paper: the constrained voter model describes the dynamics of opinions in a population of individuals located on a connected graph .
each agent is characterized by her opinion , where the set of opinions is represented by a finite sequence of consecutive integers , and each pair of neighbors , as defined by the edge set of the graph , interact at a constant rate .
the dynamics depends on two parameters : the number of opinions denoted by @xmath0 and a so - called confidence threshold denoted by @xmath1 .
if the opinion distance between two interacting agents exceeds the confidence threshold then nothing happens , otherwise one of the two agents mimics the other one just as in the classical voter model .
our main result shows that the one - dimensional system starting from any product measures with a positive density of each opinion fluctuates and clusters if and only if @xmath2 .
sufficient conditions for fixation in one dimension when the initial distribution is uniform and lower bounds for the probability of consensus for the process on finite connected graphs are also proved . .
And you have already written the first three sentences of the full article: the constrained voter model has been originally introduced in @xcite to understand the opinion dynamics in a spatially structured population of leftists , centrists and rightists . as in the popular voter model @xcite , the individuals are located on the vertex set of a graph and
interact through the edges of the graph at a constant rate .
however , in contrast with the classical voter model where , upon interaction , an individual adopts the opinion of her neighbor , it is now assumed that this imitation rule is suppressed when a leftist and a rightist interact . in particular.
Please generate the next two sentences of the article | , the model includes a social factor called homophily that prevents agents who disagree too much to interact .
* model description * this paper is concerned with a natural generalization of the previous version of the constrained voter model that includes an arbitrary finite number @xmath0 of opinions and a so - called confidence threshold @xmath1 . having a connected graph @xmath3 representing the network of interactions , |
3,928 | Suppose that you have an abstract for a scientific paper: supercontinuum generation by femtosecond filaments in air is investigated for different laser wavelengths ranging from ultraviolet to infrared .
particular attention is paid on the role of third - harmonic generation and temporal steepening effects , which enlarge the blue part of the spectrum . a unidirectional pulse propagation model and nonlinear evolution equations are numerically integrated and their results are compared .
apart from the choice of the central wavelength , we emphasize the importance of the saturation intensity reached by self - guided pulses , together with their temporal duration and propagation length as key players acting on both supercontinuum generation of the pump wave and emergence of the third harmonics .
maximal broadening is observed for large wavelengths and long filamentation ranges . , supercontinuum generation , femtosecond filaments , nonlinear schrdinger equation , self - phase modulation 42.65.tg , 52.38.hb , 42.65.jx , 42.68.ay .
And you have already written the first three sentences of the full article: third harmonic ( th ) generation and supercontinuum ( sc ) emission are two phenomena which have attracted broad interest in the past years @xcite .
an evident reason is their direct application in atmospheric remote sensing measurements based on lidar ( light detection and ranging ) femtosecond laser setups @xcite . in this context ,
spectral broadening originates from complex mechanisms that drive the long - range propagation of ultrashort pulses , when they form narrow filaments in optically - transparent media ..
Please generate the next two sentences of the article | the physics of isolated femtosecond filaments in air is nowadays rather well understood ( see , e.g. , @xcite and references therein ) .
it involves the competition between kerr self - focusing and plasma defocusing , triggered whenever the input pulse power exceeds the critical power for self - focusing @xmath0 . here |
3,929 | Suppose that you have an abstract for a scientific paper: we investigate the orbital evolution of particles in a planet s chaotic zone to determine their final destinations and their timescales of clearing .
there are four possible final states of chaotic particles : collision with the planet , collision with the star , escape , or bounded but non - collision orbits . in our investigations , within the framework of the planar circular restricted three body problem for planet - star mass ratio @xmath0 in the range @xmath1 to @xmath2 , we find no particles hitting the star .
the relative frequencies of escape and collision with the planet are not scale - free , as they depend upon the size of the planet . for planet radius @xmath3 where @xmath4 is the planet s hill radius
, we find that most chaotic zone particles collide with the planet for @xmath5 ; particle scattering to large distances is significant only for higher mass planets . for fixed ratio @xmath6 , the particle clearing timescale , @xmath7 , has a broken power - law dependence on @xmath0 .
a shallower power - law , @xmath8 , prevails at small @xmath0 where particles are cleared primarily by collisions with the planet ; a steeper power law , @xmath9 , prevails at larger @xmath0 where scattering dominates the particle loss . in the limit of vanishing planet radius ,
we find @xmath10 .
the interior and exterior boundaries of the annular zone in which chaotic particles are cleared are increasingly asymmetric about the planet s orbit for larger planet masses ; the inner boundary coincides well with the classical first order resonance overlap zone , @xmath11 ; the outer boundary is better described by @xmath12 , where @xmath13 is the planet - star separation . .
And you have already written the first three sentences of the full article: dynamical chaos arising from the overlap of orbital resonances is responsible for orbital instabilities in the solar system @xcite .
for the simplest case of the planar circular restricted three body problem , the overlap of first order , @xmath14 , mean motion resonances occurs for @xmath15 , where @xmath16 is an integer , @xmath17 and @xmath18 is the planet - star mass ratio @xcite .
this resonance overlap condition defines an approximately annular `` chaotic zone '' in the vicinity of a planet s circular orbit in which initially circular test particle orbits are rendered strongly chaotic . making use of kepler s third law with eq ..
Please generate the next two sentences of the article | [ eq : pro ] , the half - width of this zone on either side of the planet s orbit is given by @xmath19 where @xmath13 is the semi - major axis of the planet , and @xmath20 is a numerical coefficient .
an alternative analytical derivation by @xcite found @xmath21 . a numerical analysis by @xcite determined @xmath22 for planet mass in the range @xmath23 . |
3,930 | Suppose that you have an abstract for a scientific paper: we have studied numerically the spectral correlations in a metallic phase and at the metal - insulator transition .
we have calculated directly the two - point correlation function of the density of states @xmath0 . in the metallic phase ,
it is well described by the random matrix theory ( rmt ) .
for the first time , we also find numerically the diffusive corrections for the number variance @xmath1 predicted by altshuler and shklovski . at the transition , at small energy scales
, @xmath2 starts linearly , with a slope larger than in a metal . at large separations
@xmath3 , it is found to decrease as a power law @xmath4 , in good agreement with recent microscopic predictions . at the transition
, we have also calculated the form factor @xmath5 , fourier transform of @xmath2 . at large @xmath6 ,
the number variance contains two terms @xmath7 where @xmath8 is the limit of the form factor for @xmath9 .
june 14 , 1995 .
And you have already written the first three sentences of the full article: it is well established that the statistical properties of energy levels in an isolated metal present universal features characteristic of the chaotic systems@xcite . at low energy scales , in the so - called ergodic regime ,
the correlations functions are well described by the random matrix theory ( rmt)@xcite . in the diffusive regime , i.e. when the electronic mean free path @xmath10 is smaller than the typical size @xmath11 of the system , deviations from rmt occur @xcite when the energy scales become larger than the thouless energy @xmath12 .
this energy is the inverse of the characteristic time @xmath13 for a particle to diffuse through the sample ..
Please generate the next two sentences of the article | @xmath14 is the diffusion coefficient . on the other hand , in the localized regime ,
the correlations between levels are weaker and in the limit of an infinite system the statistics of energy levels becomes poissonnian . |
3,931 | Suppose that you have an abstract for a scientific paper: the ground - state magnetic phase diagram is calculated within the hubbard and @xmath0-@xmath1 exchange ( kondo ) for square and simple cubic lattices vs band filling and interaction parameter .
the difference of the results owing to the presence of localized moments in the latter model is discussed .
we employ a generalized hartree - fock approximation ( hfa ) to treat commensurate ferromagnetic ( fm ) , antiferromagnetic ( afm ) , and incommensurate ( spiral ) magnetic phases .
the electron correlations are taken into account within the hubbard model by using the kotliar - ruckenstein slave boson approximation ( sba ) .
the main advantage of this approach is a correct qualitative description of the paramagnetic phase : its energy becomes considerably lower as compared with hfa , and the gain in the energy of magnetic phases is substantially reduced .
magnetic ordering , electron correlations , phase separation .
And you have already written the first three sentences of the full article: magnetic properties of strongly correlated transition - metal systems and their relation to doping , lattice geometry and band structure are still extensively investigated .
the general result of these investigations is the existence of first - order transition between various commensurate and incommensurate magnetic states which invokes a phase separation ( first discussed by visscher @xcite ) . to describe the properties of such systems one uses many - electron models like the hubbard , @xmath0-@xmath1 exchange ( kondo ) model and anderson lattice model .
these are widely applied , _.
Please generate the next two sentences of the article | e. g. _ , for high-@xmath2 cuprates and rare earth compounds .
there exist some relations between these models in various parameter regions . |
3,932 | Suppose that you have an abstract for a scientific paper: we have investigated the structure of cyclohexene-2-ethanamine molecule both theoretically and experimantally .
theoretical investigation is based on a first principle technique density functional theory ( dft ) using plane wave basis sets and ultrasoft pseudo - potentials while the experimental technique is infrared ( ir ) spectroscopy .
exchange - correlation potential of dft was approximated in the frame of both local density approximation ( lda ) and generalized gradient approximation ( gga ) schemes .
vibrational properties of this molecule are given by the assignments in the range for wavenumber @xmath0 @xmath1 .
stable equilibrium structure of the molecule was also obtained by using lda and gga .
obtained optimized geometrical structure was used to calculate vibrational properties and stm images .
a remarkable agreement was obtained between theory and experiment , especially in the symmetric and asymmetric vibrations of nh groups . _
keywords : _
cyclohexene-2-ethanamine , first principle , ir spectrum , stm images . .
And you have already written the first three sentences of the full article: the design and synthesis of strong organic bases have long been an active field of research @xcite .
infrared spectroscopy is a valuable tool in order to obtain information about the molecular structure and properties of the molecules .
this technique is used widely in qualitative and quantitative molecular analysis ..
Please generate the next two sentences of the article | ir spectrum of interatomic vibrations can be used as structural probes for determining weak changes of structure or chemical bonding in molecules .
cyclohexene-2-ethanamine molecule consists of cyclohexene @xmath2 group attached to the carbon of ethylamine @xmath3 . |
3,933 | Suppose that you have an abstract for a scientific paper: the problem of reliability of the dynamics in biological regulatory networks is studied in the framework of a generalized boolean network model with continuous timing and noise . using well - known artificial genetic networks such as the repressilator , we discuss concepts of reliability of rhythmic attractors . in a simple evolution process
we investigate how overall network structure affects the reliability of the dynamics . in the course of the evolution ,
networks are selected for reliable dynamics .
we find that most networks can be easily evolved towards reliable functioning while preserving the original function . .
And you have already written the first three sentences of the full article: biological systems are composed of molecular components and the interactions between these components are of an intrinsically stochastic nature . at the same time , living cells perform their tasks reliably , which leads to the question how reliability of a regulatory system can be ensured despite the omnipresent molecular fluctuations in its biochemical interactions .
previously , this question has been investigated mainly on the single gene or molecule species level .
in particular , different mechanisms of noise attenuation and control have been explored , such as the relation of gene activity changes , transcription and translation efficiency , or gene redundancy @xcite ..
Please generate the next two sentences of the article | apart from these mechanisms acting on the level of the individual biochemical reactions , also features of the circuitry of the reaction networks can be identified which aid robust functioning @xcite .
a prime example of such a qualitative feature that leads to an increased stability of a gene s expression level despite fluctuations of the reactants is negative autoregulation @xcite . at a higher level of organization |
3,934 | Suppose that you have an abstract for a scientific paper: voltage - driven 180@xmath0 magnetization switching without electric current provides the possibility for revolutionizing the spintronics .
we demonstrated the voltage - driven charge - mediated 180@xmath0 magnetization switching at room temperature by combining first - principles calculations and temperature - dependent magnetization dynamics simulation .
the electric field ( @xmath1 ) induced interface charge is found to allow a giant modulation of the magnetic anisotropy ( @xmath2 ) of the nanomagnet .
particularly @xmath2 is revealed to vary linearly with respect to @xmath1 and the epitaxial strain .
magnetization dynamics simulations using the so - obtained @xmath2 show that both in - plane and perpendicular 180@xmath0 switching can be achieved by @xmath1 pulses .
the temperature effect renders the 180@xmath0 switching as probability events . statistical analysis indicates a fast ( around 2 ns ) and deterministic 180@xmath0 switching achievable at room temperature by controlling the magnitude of e and the pulse width .
the study inspires the rational design of miniaturized nanoscale spintronic devices where finite temperature effect has a great impact . .
And you have already written the first three sentences of the full article: recently , the voltage control of magnetism without electric current has been extensively studied in order to achieve minimum power consumption and device miniaturization in next - generation of spintronics.@xcite such a control is usually implemented through the magnetoelectric ( me ) coupling in heterostructures which possess coupled magnetic and electric properties .
generally , in me heterostructures voltage can control the magnetism through the interfacial mechanisms such as elastic coupling via strain transfer,@xcite charge modulation,@xcite interface bonding,@xcite and exchange coupling.@xcite for the ferromagnetic / ferroelectric heterostructures , elastic coupling mechanism is most extensively investigated , i.e. a strain generated in a ferroelectric layer by a voltage is transferred to the ferromagnetic layer through the interface and thus can be used to tailor magnetization through the magnetoelastic coupling .
the elastic coupling mechanism can work at the bulk level ..
Please generate the next two sentences of the article | all the other three mechanisms are localized to the region near the interface . among them
, the exchange coupling is localized , but can induce propagation of the magnetization into the bulk . |
3,935 | Suppose that you have an abstract for a scientific paper: this paper is the second part of a work investigating the properties of dusty tori in active galactic nuclei ( agn ) by means of multi - component spectral energy distribution ( sed ) fitting .
it focuses on low luminosity , low redshift ( @xmath0 ) agn selected among emission line galaxies in the overlapping regions between swire and sdss data release 4 as well as x - ray , radio and mid - infrared selected type 2 agn samples from the literature .
the available multi - band photometry covers the spectral range from the @xmath1-band up to 160 .
using a standard @xmath2 minimisation , the observed sed of each object is fit to a set of multi - component models comprising a stellar component , a high optical depth ( @xmath3 ) torus and cold emission from a starburst ( sb ) .
the torus components assigned to the majority of the objects were those of the highest optical depth of our grid of models ( @xmath4 ) .
the contribution of the various components ( stars , torus , sb ) is reflected in the position of the objects on the irac colour diagram , with star- , torus- and starburst - dominated objects occupying specific areas of the diagrams and composite objects lying in between .
the comparison of type 1 ( as derived from paper 1 , @xcite ) and type 2 agn properties is broadly consistent with the unified scheme .
the estimated ratio between type 2 and type 1 objects is about 2 - 2.5:1 .
the agn accretion - to - infrared luminosity ratio is an indicator of the obscuration of the agn since it scales down with the covering factor .
we find evidence supporting the receding torus paradigm , with the estimated fraction of obscured agn , derived from the distribution of the covering factor , decreasing with increasing optical luminosity ( @xmath5 ) over four orders of magnitude .
the average star formation rates are of @xmath6 for the low-@xmath7 sample , @xmath8 for the other type 2 agn and @xmath9 for the quasars ; this result however , might simply reflect observational biases , as the quasars....
And you have already written the first three sentences of the full article: dust is the cornerstone of the active galactic nuclei ( agn ) unified scheme that postulates that the diversity of the observed properties of agn are merely a result of the different lines of sight with respect to obscuring material surrounding the active nucleus ( @xcite ; @xcite ; @xcite ) .
the elements necessary for understanding the nature of agn and the variety of their properties are in fact the geometry of the circumnuclear dust and the amount of obscuration .
the latter is also needed in order to understand the physical conditions of the dust enshrouded nuclear region and to estimate the intrinsic uv - to - optical properties of the agn ..
Please generate the next two sentences of the article | obscuring dusty material should re - radiate in the infrared ( ir ) the fraction of accretion luminosity it absorbs , providing thus a direct metric for the study of the medium .
indeed all spectroscopically confirmed agn lying in regions covered by the various spitzer space telescope ( spitzer ) surveys show significant ir emission down to the detection limits . |
3,936 | Suppose that you have an abstract for a scientific paper: we present 45 - 47 angular resolution maps at 50@xmath0 sampling of the @xmath1co and @xmath2co j=1 - 0 emission toward a 1.39 @xmath3 1.33 region in the w51 hii region complex .
these data permit the spatial and kinematic separation of several spectral features observed along the line of sight to w51 , and establish the presence of a massive ( @xmath4 ) , large ( @xmath5 ) giant molecular cloud ( gmc ) , defined as the w51 gmc , centered at ( @xmath6km0.2em s@xmath7 ) . a second massive ( @xmath8 ) ,
elongated ( 136 pc @xmath3 22 pc ) molecular cloud is found at velocities of @xmath968km0.2em s@xmath7 along the southern edge of the w51 gmc .
of the five radio continuum sources that classically define the w51 region , the brightest source at @xmath10 cm ( g49.5 - 0.4 ) is spatially and kinematically coincident with the w51 gmc and three ( g48.9 - 0.3 , g49.1 - 0.4 , and g49.2 - 0.4 ) are associated with the 68km0.2em s@xmath7 cloud . published absorption line spectra indicate that the fifth prominent continuum source ( g49.4 - 0.3 ) is located behind the w51 molecular cloud .
the w51 gmc is among the upper 1% of clouds in the galactic disk by size and the upper 510% by mass .
while the w51 gmc is larger and more massive than any nearby molecular cloud , the average h@xmath11 column density is not unusual given its size and the mean h@xmath11 volume density is comparable to that in nearby clouds . the w51 gmc is also similar to other clouds in that most of the molecular mass is contained in a diffuse envelope that is not currently forming massive stars .
we speculate that much of the massive star formation activity in this region has resulted from a collision between the 68km0.2em s@xmath7 cloud and the w51 gmc .
10000 10000 .
And you have already written the first three sentences of the full article: the compact radio continuum sources comprising w51 ( @xcite ) have long been recognized to constitute some of the most luminous star formation regions in the disk of the galaxy ( @xcite ; @xcite ) .
the high luminosity , the large number of inferred o type stars ( @xcite ) , and the location of these sources within a molecular cloud ( @xcite ) all suggest that the w51 region represents the early formation stages of an ob association .
besides the intrinsic interest in the properties of w51 , this region represents one of the closest analogs in the disk of the milky way to the more vigorous star forming sites found in other galaxies ( e.g. 30 doradus ) ..
Please generate the next two sentences of the article | since these latter regions are quite distant , w51 affords many advantages in investigating the detailed properties of luminous star forming sites and inferring how these regions may originate .
one key to understanding the formation and evolution of any star forming region is establishing the properties of the molecular cloud out of which the stars form . while the molecular gas in the w51 region has been the subject of numerous studies , the interpretation of the results remain controversial . |
3,937 | Suppose that you have an abstract for a scientific paper: recently an accurate analysis of absorption spectra of molecular hydrogen , observed with the cosmic origins spectrograph aboard the hubble space telescope , in the photosphere of white dwarf stars gd133 and gd29 - 38 was published in a letter [ phys .
rev .
lett .
113 , 123002 ( 2014 ) ] , yielding a constraint on a possible dependence of the proton - electron mass ratio on a gravitational field of strength 10,000 times that at the earth s surface . in the present paper further details of that study
are presented , in particular a re - evaluation of the spectrum of the @xmath0 lyman bands relevant for the prevailing temperatures ( 12,000 - 14,000 k ) of the photospheres .
an emphasis is on the calculation of so - called @xmath1-coefficients , that represent the sensitivity of each individual line to a possible change in the proton - electron mass ratio .
such calculations were performed by semi - empirical methods and by _ ab initio _ methods providing accurate and consistent values .
a full listing is provided for the molecular physics data on the lyman bands ( wavelengths @xmath2 , line oscillator strengths @xmath3 , radiative damping rates @xmath4 , and sensitivity coefficients @xmath1 ) as required for the analyses of h@xmath5-spectra in hot dwarf stars .
a similar listing of the molecular physics parameters for the @xmath6 werner bands is provided for future use in the analysis of white dwarf spectra .
[ firstpage ] white dwarfs : molecules : h@xmath5 white dwarfs : photospheres stars : individual : gd133 , gd29 - 38 .
And you have already written the first three sentences of the full article: molecular hydrogen is the most abundant molecular species in the universe , but its spectrum is not so well suited for direct observations , because the strong dipole - allowed transitions in the lyman ( @xmath7 ) and werner ( @xmath8 ) systems fall in the range of the vacuum ultraviolet ( vuv ) , hence at wavelengths for which the earth s atmosphere is opaque . the first observation of molecular hydrogen in space was reported in 1970 @xcite using a rocket borne spectrometer observing from high altitudes , therewith evading atmospheric absorption of the vuv radiation .
subsequently , absorption lines in the vuv - spectrum of molecular hydrogen were observed with the _ copernicus _ satellite telescope @xcite .
later the vuv - absorption spectrum of h@xmath5 was observed with the _ far ultraviolet spectroscopic explorer _.
Please generate the next two sentences of the article | @xcite and the _ hubble space telescope _
@xcite , all satellite - based instruments . |
3,938 | Suppose that you have an abstract for a scientific paper: string theoretical ideas might be relevant for particle physics model building .
ideally one would hope to find a unified theory of all fundamental interactions .
there are only few consistent string theories in @xmath0 or @xmath1 space - time dimensions , but a huge landscape in @xmath2 .
we have to explore this landscape to identify models that describe the known phenomena of particle physics .
properties of compactified six spatial dimensions are crucial in that respect .
we postulate some useful rules to investigate this landscape and construct realistic models .
we identify common properties of the successful models and formulate lessons for further model building .
+ * geography of fields in extra dimensions : + string theory lessons for particle physics * * hans peter nilles@xmath3 and patrick k.s .
vaudrevange@xmath4 * + @xmath5 bethe center for theoretical physics + and + physikalisches
institut der universitt bonn , + nussallee 12 , 53115 bonn , germany + @xmath6 excellence cluster universe , technische universitt mnchen , + boltzmannstr .
2 , d-85748 , garching , germany + and + arnold sommerfeld center for theoretical physics , lmu + theresienstrae 37 , 80333 mnchen , germany .
And you have already written the first three sentences of the full article: one of the main goals of string theory is the inclusion of the standard model ( sm ) of particle physics in an ultraviolet complete and consistent theory of quantum gravity .
the hope is a unified theory of all fundamental interactions : gravity as well as strong and electroweak interactions within the @xmath7 sm .
recent support for the validity of the particle physics standard model is the 2012 discovery of the `` so - called '' higgs boson ..
Please generate the next two sentences of the article | how does this fit into known string theory ?
ideally one would have hoped to derive the standard model from string theory itself , but up to now such a program has not ( yet ) been successful . |
3,939 | Suppose that you have an abstract for a scientific paper: three - dimensional random tensor models are a natural generalization of the celebrated matrix models .
the associated tensor graphs , or 3d maps , can be classified with respect to a particular integer or half - integer , the degree of the respective graph . in this paper
we analyze the general term of the asymptotic expansion in @xmath0 , the size of the tensor , of a particular random tensor model , the multi - orientable tensor model .
we perform their enumeration and we establish which are the dominant configurations of a given degree . .
And you have already written the first three sentences of the full article: random tensor models ( see @xcite for a recent review ) generalize in dimension three ( and higher ) the celebrated matrix models ( see , for example , @xcite for a review ) . indeed , in the same way matrix models are related to combinatorial maps @xcite , tensor models in dimension three are related to tensor graphs or 3d maps . a certain case of random tensor models , the so - called colored tensor models , have been intensively studied in the recent years ( see @xcite for a review ) .
the graphs associated to these models are regular edge - colored graphs .
an important result is the asymptotic expansion in the limit @xmath1 ( @xmath0 being the size of the tensor ) , an expansion which was obtained in @xcite ..
Please generate the next two sentences of the article | the role played by the genus in the 2d case is played here by a distinct integer called the _ degree_. the dominant graphs of this asymptotic expansion are the so - called melonic graphs , which correspond to particular triangulations of the three - dimensional sphere @xmath2 .
let us also mention here that a universality result generalizing matrix universality was obtained in the tensor case in @xcite . |
3,940 | Suppose that you have an abstract for a scientific paper: the famous van benthem theorem states that modal logic corresponds exactly to the fragment of first - order logic that is invariant under bisimulation . in this article
we prove an exact analogue of this theorem in the framework of modal dependence logic @xmath0and team semantics .
we show that modal team logic @xmath1 , extending @xmath0by classical negation , captures exactly the @xmath2-definable bisimulation invariant properties of kripke structures and teams .
we also compare the expressive power of @xmath1to most of the variants and extensions of @xmath0recently studied in the area . .
And you have already written the first three sentences of the full article: the concepts of dependence and independence are ubiquitous in many scientific disciplines such as experimental physics , social choice theory , computer science , and cryptography . dependence logic @xmath3@xcite and
its so - called team semantics have given rise to a new logical framework in which various notions of dependence and independence can be formalized and studied .
dependence logic extends first - order logic by dependence atoms @xmath4 expressing that the value of the variable @xmath5 is functionally dependent on the values of @xmath6 ..
Please generate the next two sentences of the article | the formulas of dependence logic are evaluated over _ teams _ ,
i.e. , sets of assignments , and not over single assignments as in first - order logic . in @xcite a modal variant of dependence logic @xmath0was introduced . in the modal framework teams are sets of worlds , and a dependence atom @xmath7 holds in a team @xmath8 if there is a boolean function that determines the value of the propositional variable @xmath9 from those of @xmath10 in all worlds in @xmath8 . |
3,941 | Suppose that you have an abstract for a scientific paper: a key source for lisa will be the inspiral of compact objects into massive black holes .
recently mino has shown that in the adiabatic limit , gravitational waveforms for these sources can be computed by using for the radiation reaction force the gradient of one half the difference between the retarded and advanced metric perturbations . using post - newtonian expansions
, we argue that the resulting waveforms should be sufficiently accurate for signal detection with lisa .
data - analysis templates will require higher accuracy , going beyond adiabaticity ; this remains a significant challenge .
we describe an explicit computational procedure for obtaining waveforms based on mino s result , for the case of a point particle coupled to a scalar field .
we derive an explicit expression for the time - averaged time derivative of the carter constant , and verify that the expression correctly predicts that circular orbits remain circular while evolving under the influence of radiation reaction .
the derivation uses detailed properties of mode expansions , green s functions and bound geodesic orbits in the kerr spacetime , which we review in detail .
this paper is about three quarters review and one quarter new material .
the intent is to give a complete and self - contained treatment of scalar radiation reaction in the kerr spacetime , in a single unified notation , starting with the kerr metric , and ending with formulae for the time evolution of all three constants of the motion that are sufficiently explicit to be used immediately in a numerical code . .
And you have already written the first three sentences of the full article: a key unsolved problem in general relativity is to compute the gravitational radiation produced by a small object spiralling into a much larger black hole .
this problem is of direct observational relevance .
inspirals of compact objects into intermediate mass black holes ( @xmath0 may be observed by ligo and other ground based interferometers @xcite ; recent observations suggest the existence of black holes in this mass range @xcite ..
Please generate the next two sentences of the article | in addition , a key source for the space - based gravitational wave detector lisa is the final epoch of inspiral of a stellar - mass compact object into a massive ( @xmath1 ) black hole at the center of a galaxy .
@xcite have estimated that lisa should see over a thousand such inspiral events during its multi - year mission lifetime , based on monte carlo simulations of the dynamics of stellar cusps by freitag @xcite . |
3,942 | Suppose that you have an abstract for a scientific paper: the spinless resonant level model is studied when it is coupled by hopping to one of the arbitrary number of conduction electron channels .
the coulomb interaction acts between the electron on the impurity and in the different channels . in case of repulsive or attractive interaction the conduction electrons
are pushed away or attracted to ease or hinder the hopping by creating unoccupied or occupied states , respectively . in the screening of the hopping orthogonality catastrophe
plays an important role . in equilibrium
the weak and strong coupling limit the renormalizations are treated by perturbative , numerical and anderson - yuval coulomb gas methods . in case of two leads the current due to applied voltage is treated in the weak coupling limit .
the presented detailed study should help to test other methods suggested for non - equilibrium transport . .
And you have already written the first three sentences of the full article: in the recent years the quantum impurity problem out - of - equilibrium has attracted great interest .
the most relevant realizations are the quantum dots connected to at least two metallic leads@xcite and short metallic wires containing magnetic impurities@xcite . in the impurity problem
the exact methods play distinguished roles especially the bethe ansatz and conformal invariance ..
Please generate the next two sentences of the article | the generalization of these methods to out - of - equilibrium situations are the most challenging new directions .
mehta and andrei are aiming to solve the kondo problem on a dot with two contact attached . first a simple resonant level without spin was studied to test the new generalization of the bethe ansatz method@xcite . |
3,943 | Suppose that you have an abstract for a scientific paper: in this paper we propose on continuous level a class of domain decomposition methods of robin robin type to solve the problems of unilateral contact between elastic bodies with nonlinear winkler covers .
these methods are based on abstract nonstationary iterative algorithms for nonlinear variational equations in reflexive banach spaces .
we also provide numerical investigations of obtained methods using finite element approximations .
* key words : * unilateral contact , nonlinear winkler layers , nonlinear variational inequalities , nonlinear variational equations , iterative methods , domain decomposition * msc2010 : * 65n55 , 74s05 .
And you have already written the first three sentences of the full article: thin covers from another material are often applied in engineering to improve the functional properties of the surfaces of components of machines and structures . on the other hand ,
thin covers with certain mechanical properties are used for modeling of real microstructure of the surfaces , adhesion and glue bondings @xcite .
the classical methods for solution of contact problems for bodies with thin covers are grounded on integral equations and are reviewed in work @xcite ..
Please generate the next two sentences of the article | nowadays , one of the most effective numerical methods for such contact problems are methods , based on variational formulations and finite element approximations .
efficient approach for solution of multibody contact problems is the use of domain decomposition methods ( ddms ) . |
3,944 | Suppose that you have an abstract for a scientific paper: in this paper we compare the performance characteristics of our selection based learning algorithm for web crawlers with the characteristics of the reinforcement learning algorithm .
the task of the crawlers is to find new information on the web .
the selection algorithm , called weblog update , modifies the starting url lists of our crawlers based on the found urls containing new information .
the reinforcement learning algorithm modifies the url orderings of the crawlers based on the received reinforcements for submitted documents .
we performed simulations based on data collected from the web .
the collected portion of the web is typical and exhibits scale - free small world ( sfsw ) structure .
we have found that on this sfsw , the weblog update algorithm performs better than the reinforcement learning algorithm .
it finds the new information faster than the reinforcement learning algorithm and has better new information / all submitted documents ratio .
we believe that the advantages of the selection algorithm over reinforcement learning algorithm is due to the small world property of the web . .
And you have already written the first three sentences of the full article: the largest source of information today is the world wide web .
the estimated number of documents nears 10 billion .
similarly , the number of documents changing on a daily basis is also enormous ..
Please generate the next two sentences of the article | the ever - increasing growth of the web presents a considerable challenge in finding novel information on the web .
in addition , properties of the web , like scale - free small world ( sfsw ) structure @xcite may create additional challenges . |
3,945 | Suppose that you have an abstract for a scientific paper: we calculate the static critical behavior of systems of @xmath0 symmetry by renormalization group method within the minimal subtraction scheme in two loop order .
summation methods lead to fixed points describing multicritical behavior .
their stability boarder lines in the space of order parameter components @xmath1 and @xmath2 and spatial dimension @xmath3 are calculated .
the essential features obtained already in two loop order for the interesting case of an antiferromagnet in a magnetic field ( @xmath4 , @xmath5 ) are the stability of the biconical fixed point and the neighborhood of the stability border lines to the other fixed points leading to very small transient exponents .
we are also able to calculate the flow of static couplings , which allows to consider the attraction region .
depending on the nonuniversal background parameters the existence of different multicritical behavior ( bicritical or tetracritical ) is possible including a triple point . .
And you have already written the first three sentences of the full article: antiferromagnets in an external magnetic field show a variety of phase diagrams depending on the interaction terms present in the spin hamiltonian@xcite .
the spin interaction may be isotropic , anisotropic with an easy axis and/or single - ion anisotropy terms , where the anisotropy is in the direction of the external magnetic field .
the phase diagram of such models exhibit a multicritical point , where several transition lines meet . at a _.
Please generate the next two sentences of the article | bicritical _ point three phases - an antiferromagnetic phase , a spin flop phase and the paramagnetic phase - are in coexistence .
the phase transition lines to the paramagnetic phase are second order transition lines , whereas the transition line between the spin flop and the antiferromagnetic phase is of first order . at the _ tetracritical _ point four phases - an antiferromagnetic phase , a spin flop phase , an intermediate or mixed phase and the paramagnetic phase - are in coexistence . |
3,946 | Suppose that you have an abstract for a scientific paper: we present an explicit formula for the discrete power function introduced by bobenko , which is expressed in terms of the hypergeometric @xmath0 functions for the sixth painlev equation .
the original definition of the discrete power function imposes strict conditions on the domain and the value of the exponent .
however , we show that one can extend the value of the exponent to arbitrary complex numbers except even integers and the domain to a discrete analogue of the riemann surface .
moreover , we show that the discrete power function is an immersion when the real part of the exponent is equal to one . .
And you have already written the first three sentences of the full article: the theory of discrete analytic functions has been developed in recent years based on the theory of circle packings or circle patterns , which was initiated by thurston s idea of using circle packings as an approximation of the riemann mapping@xcite .
so far many important properties have been established for discrete analytic functions , such as the discrete maximum principle and schwarz s lemma@xcite , the discrete uniformization theorem@xcite , and so forth . for a comprehensive introduction to the theory of discrete analytic functions
, we refer to @xcite ..
Please generate the next two sentences of the article | it is known that certain circle patterns with fixed regular combinatorics admit rich structure .
for example , it has been pointed out that the circle patterns with square grid combinatorics introduced by schramm@xcite and the hexagonal circle patterns@xcite are related to integrable systems . |
3,947 | Suppose that you have an abstract for a scientific paper: galaxies over four decades in stellar mass are shown to obey a strong correlation between @xmath0 colors and atomic - gas - to - stellar mass ratios ( g / s ) , using stellar mass - to - light ratios derived from optical colors .
the correlation holds for g / s ranging from nearly 10:1 to 1:100 for a sample obtained by merging the sdss dr2 , 2mass , and hyperleda hi catalogs .
this result implies that @xmath0 colors can be calibrated to provide `` photometric gas fractions '' for statistical applications . here
this technique is applied to a sample of @xmath135,000 sdss-2mass galaxies to examine the relationship of gas fractions to observed bimodalities in galaxy properties as a function of color and stellar mass . the recently identified transition in galaxy properties at stellar masses
@xmath2@xmath3 m@xmath4 corresponds to a shift in gas richness , dividing low - mass late - type galaxies with g / s @xmath1 1:1 from high - mass galaxies with intermediate - to - low g / s .
early - type galaxies below the transition mass also show elevated g / s , consistent with formation scenarios involving mergers of low - mass gas - rich systems and/or cold - mode gas accretion . .
And you have already written the first three sentences of the full article: analyses of galaxies in the sloan digital sky survey ( sdss ) have demonstrated two distinct bimodalities in galaxy properties : a bimodality between recent - burst dominated and more continuous star formation histories ( sfhs ) as a function of stellar mass @xmath5 , divided at @xmath6 m@xmath4 @xcite , and a bimodality between blue late - type and red early - type galaxy sequences as a function of optical color , divided at @xmath7 @xcite .
recently , @xcite have partially unified these observations , demonstrating a color transition within each of the two galaxy sequences at @xmath8 m@xmath4 , as well as an increase in the relative number density of red sequence galaxies above @xmath125@xmath9 m@xmath4 .
they also argue that the number density of the red sequence is consistent with a major - merger origin ..
Please generate the next two sentences of the article | however , the cause of the color and sfh transitions at @xmath123@xmath9 m@xmath4 remains to be explained .
several physical processes that influence sfhs may imprint a transition mass on the galaxy population . |
3,948 | Suppose that you have an abstract for a scientific paper: this article describes the search for pair production of scalar leptoquarks performed by the cms collaboration using the data from the 2010 proton - proton run of the large hadron collider at a center of mass energy of 7 tev .
the following final state signatures from the decay of a pair of scalar leptoquarks are described in here : the di - lepton plus jets final state ( where the leptons are either both electrons or both muons ) and the lepton plus jets and transverse missing energy final state ( where the lepton is an electron ) . .
And you have already written the first three sentences of the full article: leptoquarks ( lq ) are hypothetical particles that are predicted by many extensions @xcite of the standard model of particle physics ( sm ) , such as grand unification theory , technicolor and composite models .
they carry both baryon and lepton numbers and thus couple to a lepton and a quark .
they carry fractional electric charge , they are color triples , and can have either zero or one unit of spin ( i.e. can be either scalar or vector particles ) . existing experimental limits on lepton number violation , flavor changing neutral current , proton decay , and other rare processes favor three generations of leptoquarks , with no inter - generational mixing . the production and decay of lqs.
Please generate the next two sentences of the article | are characterized by : the mass of the lq particle ( m@xmath0 ) , its decay branching ratio into a lepton and a quark ( usually denoted as @xmath1 ) and the yukawa coupling at the lq - lepton - quark vertex ( @xmath2 ) . at hadron colliders ,
leptoquarks are mainly produced in pairs , via gluon - gluon fusion and quark anti - quark annihilation . |
3,949 | Suppose that you have an abstract for a scientific paper: recent months have witnessed dramatic progress in our understanding of short @xmath0-ray burst ( sgrb ) sources .
there is now general agreement that sgrbs or at least a substantial subset of them are capable of producing directed outflows of relativistic matter with a kinetic luminosity exceeding by many millions that of active galactic nuclei . given the twin requirements of energy and compactness , it is widely believed that sgrb activity is ultimately ascribable to a modest fraction of a solar mass of gas accreting onto a stellar mass black hole or to a precursor stage whose inevitable end point is a stellar mass black hole .
astrophysical scenarios involving the violent birth of a rapidly rotating neutron star , or an accreting black hole in a merging compact binary driven by gravitational wave emission are reviewed , along with other possible alternatives ( collisions or collapse of compact objects ) .
if a black hole lies at the center of this activity , then the fundamental pathways through which mass , angular momentum and energy can flow around and away from it play a key role in understanding how these prime movers can form collimated , relativistic outflows .
flow patterns near black holes accreting matter in the _ hypercritical _ regime , where photons are unable to provide cooling , but neutrinos do so efficiently , are discussed in detail , and we believe that they offer the best hope of understanding the _ central engine_. on the other hand , statistical investigations of sgrb niches also furnish valuable information on their nature and evolutionary behavior .
the formation of particular kinds of progenitor sources appears to be correlated with environmental effects and cosmic epoch .
in addition , there is now compelling evidence for the continuous fueling of sgrb sources .
we suggest here that the observed late flaring activity could be due to a secondary accretion episode induced by the delayed fall back of material dynamically stripped from a compact object during a merger....
And you have already written the first three sentences of the full article: in the sections which follow , we shall be concerned predominantly with the theory of short @xmath0-ray bursts . if the concepts there proposed are indeed relevant to an understanding of the nature of these sources , then their existence becomes inextricably linked to the _ metabolic pathways _ through which gravity , spin , and energy can combine to form collimated , ultra relativistic outflows .
these threads are few and fragile , as we are still wrestling with understanding non - relativistic processes , most notably those associated with the electromagnetic field and gas dynamics .
if we are to improve our picture - making we must make more and stronger ties to physical theory . but in reconstructing the creature , we must be guided by our eyes and their extensions . in this introductory chapter.
Please generate the next two sentences of the article | we have therefore attempted to briefly summarize the observed properties of these ultra - energetic phenomena .
there are five sections : [ sec : his ] gives a brief account of their history from birth to present - age ; [ sec : metabolics ] is devoted to their metabolism in other words , to their gross energetics , spectra and time variability ; [ sec : aft ] describes the attributes of the afterglow signals , which , as fading beacons , mark the location of the fiery and brief @xmath0-ray event . these afterglows in turn enable the measurement of redshift distances , the identification of host galaxies at cosmological distances , and provide evidence that many short @xmath0-ray bursts are associated with old stellar populations and possibly with no bright supernova . |
3,950 | Suppose that you have an abstract for a scientific paper: we suggest searching for excited charmonium states in @xmath0 annihilation via double charmonium production at @xmath1 gev with @xmath2 factories , based on a more complete leading order calculation including both qcd and qed contributions for various processes .
in particular , for the c=+ states , the @xmath3 ( n=2,3 ) and @xmath4 ( m=3,4 ) may have appreciable potentials to be observed ; while for the c=- states , the @xmath5 production and especially the @xmath6 production might provide opportunities for observing the @xmath7 with higher statistics in the future . a brief discussion for the x(3940 ) observed in the double charmonium production is included . .
And you have already written the first three sentences of the full article: charmonium spectroscopy has become a challenging topic in hadron physics and qcd , because of the recent findings of possible new charmonium states ( for recent experimental and theoretical reviews and discussions , see e.g. @xcite and references therein ) . among others , for the puzzling state x(3872 ) , possible assignments of e.g. the @xmath8 and @xmath9 charmonium states and the charm - molecule
have been suggested ( see , e.g.@xcite for a comprehensive review ) , and it will be helpful to search for those states in other experiments and to clarify these assignments ; the measured mass splitting between @xmath10 and @xmath11 is about 50 mev , which is smaller than some theoretical predictions , and it is certainly useful to search for the @xmath12 to see what will be the mass splitting between the @xmath13 , which could be the observed @xmath14 , and the @xmath12 .
this may be particularly interesting since according to some potential model calculations the @xmath12 could lie above 4040 mev ( see , e.g. in @xcite the mass of @xmath12 is predicted to be 4060 mev ) . and the @xmath13 mass could actually be lowered by coupling to the nearby @xmath15 decay channels ( note that the energy level spacing between @xmath16 and @xmath17 is smaller than that between @xmath18 and @xmath16 , which is in contradiction with potential model calculations unless the coupled channel effects are considered or the assignments for @xmath16 and @xmath18 are incorrect.
Please generate the next two sentences of the article | . the mass spectrum of excited charmonium states will certainly provide important information on interquark forces and color confinement .
in addition , studies of the decay and production of these states will also be very important in understanding the underlying theory of strong interaction perturbative and nonperturbative qcd in view of many outstanding puzzles in charmonium physics . |
3,951 | Suppose that you have an abstract for a scientific paper: area - preserving twist maps have at least two different @xmath0-periodic orbits and every @xmath0-periodic orbit has its @xmath0-periodic action for suitable couples @xmath0 .
we establish an exponentially small upper bound for the differences of @xmath0-periodic actions when the map is analytic on a @xmath1-resonant rotational invariant curve ( resonant ric ) and @xmath2 is `` sufficiently close '' to @xmath3 .
the exponent in this upper bound is closely related to the analyticity strip width of a suitable angular variable .
the result is obtained in two steps .
first , we prove a neishtadt - like theorem , in which the @xmath4-th power of the twist map is written as an integrable twist map plus an exponentially small remainder on the distance to the ric .
second , we apply the mackay - meiss - percival action principle .
we apply our exponentially small upper bound to several billiard problems .
the resonant ric is a boundary of the phase space in almost all of them .
for instance , we show that the lengths ( respectively , areas ) of all the @xmath5-periodic billiard ( respectively , dual billiard ) trajectories inside ( respectively , outside ) analytic strictly convex domains are exponentially close in the period @xmath6 .
this improves some classical results of marvizi , melrose , colin de verdire , tabachnikov , and others about the smooth case .
_ keywords _ : twist maps , invariant curves , exponential smallness , billiards , dual billiards .
And you have already written the first three sentences of the full article: billiards were introduced by birkhoff @xcite .
let @xmath7 be a smooth strictly convex curve in the plane , oriented counterclockwise , and let @xmath8 be the billiard table enclosed by @xmath7 .
billiard trajectories inside @xmath8 consist of polygonal lines inscribed in @xmath7 whose consecutive sides obey to the rule `` the angle of reflection is equal to the angle of incidence . ''.
Please generate the next two sentences of the article | see @xcite for a general description .
a @xmath0-periodic billiard trajectory forms a closed polygon with @xmath6 sides that makes @xmath9 turns inside @xmath7 . |
3,952 | Suppose that you have an abstract for a scientific paper: this work introduces a single - stage , single - step method for the compressible euler equations that is provably positivity - preserving and can be applied on both cartesian and unstructured meshes .
this method is the first case of a single - stage , single - step method that is simultaneously high - order , positivity - preserving , and operates on unstructured meshes .
time - stepping is accomplished via the lax - wendroff approach , which is also sometimes called the cauchy - kovalevskaya procedure , where temporal derivatives in a taylor series in time are exchanged for spatial derivatives . the lax - wendroff discontinuous galerkin ( lxw - dg ) method developed in this work
is formulated so that it looks like a forward euler update but with a high - order time - extrapolated flux . in particular , the numerical flux used in this work
is a linear combination of a low - order positivity - preserving contribution and a high - order component that can be damped to enforce positivity of the cell averages for the density and pressure for each time step .
in addition to this flux limiter , a moment limiter is applied that forces positivity of the solution at finitely many quadrature points within each cell .
the combination of the flux limiter and the moment limiter guarantees positivity of the cell averages from one time - step to the next . finally , a simple shock capturing limiter that uses the same basic technology as the moment limiter is introduced in order to obtain non - oscillatory results .
the resulting scheme can be extended to arbitrary order without increasing the size of the effective stencil .
we present numerical results in one and two space dimensions that demonstrate the robustness of the proposed scheme . .
And you have already written the first three sentences of the full article: the purpose of this work is to develop a positivity - preserving version of the lax - wendroff discontinuous galerkin method for the compressible euler equations on unstructured meshes .
the compressible euler equations form a system of hyperbolic conservation law that can be written as follows : @xmath0 the _ conserved _ variables are the mass density , @xmath1 , the momentum density , @xmath2 , and the energy density , @xmath3 ; the _ primitive _ variables are the mass density , @xmath1 , the fluid velocity , @xmath4 , and the pressure , @xmath5 . the energy @xmath3 is related to the primitive variables through the equation of state , @xmath6 where the constant @xmath7 is the ratio of specific heats ( aka , the _ gas constant _ ) .
the compressible euler equations are an important mathematical model in the study of gases and plasma ..
Please generate the next two sentences of the article | attempts at numerically solving the these equations has led to a plethora of important historical advances in the development of numerical analysis and scientific computing ( see e.g. , @xcite ) .
the focus of this work is on high - order discontinuous galerkin ( dg ) methods , which were originally developed for general hyperbolic conservation laws by cockburn , shu , et al . in series of papers @xcite . |
3,953 | Suppose that you have an abstract for a scientific paper: the amount of information exchanged per unit of time between two nodes in a dynamical network or between two data sets is a powerful concept for analysing complex systems .
this quantity , known as the mutual information rate ( mir ) , is calculated from the mutual information , which is rigorously defined only for random systems . moreover ,
the definition of mutual information is based on probabilities of significant events .
this work offers a simple alternative way to calculate the mir in dynamical ( deterministic ) networks or between two data sets ( not fully deterministic ) , and to calculate its upper and lower bounds without having to calculate probabilities , but rather in terms of well known and well defined quantities in dynamical systems . as possible applications of our bounds
, we study the relationship between synchronisation and the exchange of information in a system of two coupled maps and in experimental networks of coupled oscillators . .
And you have already written the first three sentences of the full article: shannon s entropy quantifies information @xcite .
it measures how much uncertainty an observer has about an event being produced by a random system .
another important concept in the theory of information is the mutual information @xcite ..
Please generate the next two sentences of the article | it measures how much uncertainty an observer has about an event in a random system * x * after observing an event in a random system * y * ( or vice - versa ) .
mutual information is an important quantity because it quantifies not only linear and non - linear interdependencies between two systems or data sets , but also is a measure of how much information two systems exchange or two data sets share . due to these characteristics |
3,954 | Suppose that you have an abstract for a scientific paper: we present a time - resolved study of energy relaxation and trapping dynamics of polariton condensates in a semiconductor microcavity ridge . the combination of two non - resonant , pulsed laser sources in a gaas ridge - shaped microcavity gives rise to profuse quantum phenomena where the repulsive potentials created by the lasers allow the modulation and control of the polariton flow .
we analyze in detail the dependence of the dynamics on the power of both lasers and determine the optimum conditions for realizing an all - optical polariton condensate transistor switch .
the experimental results are interpreted in the light of simulations based on a generalized gross - pitaevskii equation , including incoherent pumping , decay and energy relaxation within the condensate . .
And you have already written the first three sentences of the full article: bose - einstein condensation of quasiparticles in solid - state systems has been observed in excitons in quantum hall bilayers , @xcite exciton - polaritons in semiconductor microcavities , @xcite gases of magnons , @xcite cavity photons @xcite and indirect excitons .
@xcite exciton - polaritons , mixed light - matter quasiparticles behaving as bosons , form condensates which exhibit not only the fundamental properties of quantum gases , but also new fascinating phenomena related to their out - of - equilibrium character .
@xcite the photonic component of polaritons is responsible for their light mass , which makes condensation possible up to room temperature @xcite , and for their easy creation , manipulation and detection by using simple optical - microscopy setups . on the other hand ,.
Please generate the next two sentences of the article | their excitonic component yields strong coulomb repulsive interactions that make them promising candidates for future non - linear optical technologies .
the peculiar quantum fluid properties of polariton condensates are under intense research nowadays . |
3,955 | Suppose that you have an abstract for a scientific paper: we study the nature of collective excitations in harmonic chains with masses exhibiting long - range correlated disorder with power spectrum proportional to @xmath0 , where @xmath1 is the wave - vector of the modulations on the random masses landscape . using a transfer matrix method and exact diagonalization ,
we compute the localization length and participation ratio of eigenmodes within the band of allowed energies .
we find extended vibrational modes in the low - energy region for @xmath2 . in order to study the time evolution of an initially localized energy input ,
we calculate the second moment @xmath3 of the energy spatial distribution .
we show that @xmath3 , besides being dependent of the specific initial excitation and exhibiting an anomalous diffusion for weakly correlated disorder , assumes a ballistic spread in the regime @xmath4 due to the presence of extended vibrational modes . .
And you have already written the first three sentences of the full article: the role played by disorder on the nature of collective excitations in condensed matter physics has been the subject of intensive studies due to its relevance in defining general transport characteristics @xcite .
usually , disorder induces localization of collective excitations thus degrading transport properties , an effect that is largely pronounced in low dimensions .
in particular , the one - electron eigen - states in the one - dimensional anderson model with site - diagonal uncorrelated disorder are exponentially localized for any degree of disorder @xcite ..
Please generate the next two sentences of the article | however , several one - dimensional models with correlated disorder have been proposed which exhibit delocalized states @xcite .
recently , it has been shown that the one - dimensional anderson model with long - range correlated disorder presents a phase of extended electronic states @xcite . |
3,956 | Suppose that you have an abstract for a scientific paper: we consider a general class of ( intersecting ) loop models in @xmath0 dimensions , including those related to high - temperature expansions of well - known spin models .
we find that the loop models exhibit some interesting features often in the `` unphysical '' region of parameter space where all connection with the original spin hamiltonian is apparently lost .
for a particular @xmath1 , @xmath2 model , we establish the existence of a phase transition , possibly associated with divergent loops .
however , for @xmath3 and arbitrary @xmath0 there is no phase transition marked by the appearance of large loops .
furthermore , at least for @xmath2 ( and @xmath4 large ) we find a phase transition characterised by broken translational symmetry .
loop models , reflection positivity , phase transitions . .
And you have already written the first three sentences of the full article: in the recent years there has been much interest in various loop models .
loop models are graphical models defined by drawing closed loops along the bonds of the underlying lattice .
the loops may come in @xmath4 different flavours ( colours ) ..
Please generate the next two sentences of the article | no two loops can share a bond , while sharing a vertex is generally allowed .
explicitly , the bond configurations are such that each vertex houses an even number possibly zero of bonds of each colour . |
3,957 | Suppose that you have an abstract for a scientific paper: we investigate the characteristic properties of self - sustained mri turbulence in low - ionized proto - planetary disks .
we study the transition regime between active and dead - zone , performing 3d global non - ideal mhd simulations of stratified disk covering range of magnetic reynolds number between @xmath0 .
we found converged and saturated mri turbulence for @xmath1 with a strength of @xmath2 .
below @xmath3 the mri starts to decay at the midplane , having elsasser numbers below one .
we find a transition regime between @xmath4 where the mri turbulence is still sustained but damped . at around @xmath5 the mri turbulence decays but could reestablished due to the accumulation of toroidal magnetic field or the radial transport of magnetic field from the active region . below @xmath6 the mri can not be sustained and is decaying . here hydro - dynamical motions , like density waves dominate .
we observe long - living anti - cyclonic vortices in the transition between dead - zone and active zone . .
And you have already written the first three sentences of the full article: the magneto - rotational instability ( mri ) is a candidate for driving turbulence and enabling the accretion of matter onto the central object @xcite .
dependent on the ionization degree , the mri generated turbulence will be reduced , down to a low turbulence regime , called the dead zone @xcite .
various studies showed that a certain level of resistivity suppresses mri activity @xcite ..
Please generate the next two sentences of the article | one of the most important dimensionless number , characterizing the coupling between gas and magnetic fields , is the magnetic reynolds number @xmath7 which relates the timescale of magnetic advection to magnetic diffusion .
we consider here the ohmic diffusion term which is most important at the midplane . up to now |
3,958 | Suppose that you have an abstract for a scientific paper: we present an experimental characterization of the statistics of multiple photon pairs produced by spontaneous parametric down - conversion realized in a nonlinear medium pumped by high - energy ultrashort pulses from a regenerative amplifier .
the photon number resolved measurement has been implemented with the help of a fiber loop detector .
we introduce an effective theoretical description of the observed statistics based on parameters that can be assigned direct physical interpretation .
these parameters , determined for our source from the collected experimental data , characterize the usefulness of down - conversion sources in multiphoton interference schemes that underlie protocols for quantum information processing and communication . .
And you have already written the first three sentences of the full article: spontaneous parametric down - conversion ( spdc ) is the basic source of non - classical light in experimental quantum optics @xcite , testing foundations of the quantum theory @xcite , and implementing protocols for quantum information information processing and communication @xcite .
the essential feature of spdc is the guarantee that the photons are always produced in pairs , and suitable arrangements allow one to generate various types of classical and quantum correlations within those pairs .
the physics of spdc depends strongly on optical properties of nonlinear media in which the process is realized ..
Please generate the next two sentences of the article | this leads to an interplay between different characteristics of the source and usually imposes trade - offs on its performance .
for example , many experiments require photon pairs to be prepared in well - defined single spatio - temporal modes . |
3,959 | Suppose that you have an abstract for a scientific paper: the textbook knowledge of solid state physics is that the electronic specific heat shows a linear temperature dependence with the leading corrections being a cubic term due to phonons and a cubic - logarithmic term due to the interaction of electrons with bosons .
we have shown that this longstanding conception needs to be supplemented since the generic behavior of the low - temperature electronic specific heat includes a kink if the electrons are sufficiently strongly correlated . .
And you have already written the first three sentences of the full article: landau s fermi liquid theory @xcite can be considered as the `` standard theory '' of solid state physics .
it predicts that the electronic properties of a ( normal ) metal follow , in the presence of coulomb correlations , a renormalized ( quasiparticle ) version of those for non - interacting electrons . among the most fundamental physical properties
is the heat capacity which , at low temperatures , is predominated by the electronic degrees of freedom . for a normal metal ,.
Please generate the next two sentences of the article | landau s fermi liquid theory @xcite predicts a linear increase of the specific heat capacity with temperature @xmath0 and a cubic term , more precisely a term @xmath1 , as the leading correction @xcite . for free electrons ,
the prefactor @xmath2 is directly proportional to the electronic density of states at the fermi level since , due to the pauli principle , only these electrons contribute . in the case of a fermi liquid |
3,960 | Suppose that you have an abstract for a scientific paper: magnonics and magnon spintronics aim at the utilization of spin waves and magnons , their quanta , for the construction of wave - based logic networks via the generation of pure all - magnon spin currents and their interfacing with electrical charge transport . the promise of efficient parallel data processing and low power consumption renders this field one of the most promising research areas in spintronics . in this context , the process of parallel parametric amplification , i.e. , the conversion of microwave photons into magnons at one half of the microwave frequency , has proven to be a versatile tool to excite and to manipulate spin waves .
its beneficial and unique properties such as frequency and mode - selectivity , the possibility to excite spin waves in a wide wavevector range and the creation of phase - correlated wave pairs , have enabled the achievement of important milestones like the magnon bose einstein condensation and the cloning and trapping of spin - wave packets .
parallel parametric amplification , which allows for the selective amplification of magnons while conserving their phase is , thus , one of the key methods of spin - wave generation and amplification .
the application of parallel parametric amplification to cmos - compatible micro- and nanostructures is an important step towards the realization of magnonic networks .
this is motivated not only by the fact that amplifiers are an important tool for the construction of any extended logic network but also by the unique properties of parallel parametric amplification .
in particular , the creation of phase - correlated wave pairs allows for rewarding alternative logic operations such as a phase - dependent amplification of the incident waves .
recently , the successful application of parallel parametric amplification to metallic microstructures has been reported which constitutes an important milestone for the application of magnonics in practical devices .
it has been demonstrated that parametric amplification....
And you have already written the first three sentences of the full article: the research fields of magnonics and , on a broader scale , magnon spintronics , which includes interfacing to electric charge transport phenomena , aim at the utilization of magnons , the quanta of spin - wave excitation in a magnetic material , as information carriers in a next generation of logic devices beyond conventional cmos@xcite .
this research area has attracted prominent interest in the recent years due to the demonstration of various game - changing devices such as magnonic all - linear time - inverters@xcite , magnon transistors@xcite and reconfigurable magnonic waveguides@xcite , which are just a few , yet instructive , examples . however , for a successful application of magnonics on the micro- and nanometer scale , the research field still faces several challenges .
one of the main issues is the spin - wave damping , which is substantial in most conventionally used , cmos - compatible ferromagnetic metals@xcite ..
Please generate the next two sentences of the article | while recent studies show the large potential to decrease this damping by material engineering@xcite , a reduction of the spin - wave damping comes together with a restriction of the maximum tolerable amplitude of the spin - wave excitation if nonlinear phenomena are to be avoided@xcite .
this is , for example , the case if several spin waves are conveying information encoded in their phase in parallel in a magnonic waveguide . |
3,961 | Suppose that you have an abstract for a scientific paper: we study the @xmath0 criticality and phase transition in the extended phase space of ads black holes in higher - dimensional drgt massive gravity , treating the cosmological constant as pressure and the corresponding conjugate quantity is interpreted as thermodynamic volume . besides the usual small / large black hole phase transitions
, the interesting thermodynamic phenomena of reentrant phase transitions are observed for all @xmath1 dimensions when the coupling coefficients @xmath2 of massive potential satisfy some certain conditions . .
And you have already written the first three sentences of the full article: the einstein s general relativity ( gr ) is a relativistic theory of gravity where the graviton is a massless spin-2 particle @xcite .
gr is the current description of gravitation in modern physics and has significantly astrophysical implications .
nevertheless , whether there exist a consistent extension of gr by a mass term is a basic challenge of classical field theory , since the open questions such as the old cosmological constant problem and the origin of the late - time acceleration of the universe remain behind the puzzles at the interface between gravity / cosmology and particle physics . in general , by adding generic mass terms for the gravitons on the given background usually brings various instabilities for the gravitational theories , sometimes on the nonlinear level ..
Please generate the next two sentences of the article | a new nonlinear massive gravity theory was proposed by de rham , gabadadze and tolley ( drgt ) @xcite , where the boulware - deser ghost @xcite was eliminated by introducing higher order interaction terms in the action . until now
, a nontrivial black hole solution with a ricci flat horizon in four - dimensional drgt massive gravity has been constructed by vegh @xcite . |
3,962 | Suppose that you have an abstract for a scientific paper: we provide the first evidence of a walking dynamics for two color lattice yang - mills theory with two dirac flavors in the symmetric representation of the gauge group . .
And you have already written the first three sentences of the full article: we undertake the first numerical study of a four dimensional asymptotically free gauge theory with dynamical fermions transforming according to the two index symmetric representation of the gauge group . to be more precise we consider the simplest of these theories with interesting dynamics and phenomenological applications , i.e. a two color gauge theory with two dirac fermions transforming according to the two index symmetric representation . for two colors the two index symmetric coincides with the adjoint representation and the reality of the representation
enhances the quantum flavor symmetry group to @xmath0 .
remarkably this theory coincides with the fermionic sector of the @xmath1 supersymmetric theory with two colors ..
Please generate the next two sentences of the article | recently it has been argued that this theory lies close to a non trivial infrared fixed point @xcite . in this case the coupling constant will run very slowly from the infrared to the ultraviolet ; the coupling is said to _ walk_. by analyzing the phase diagram as function of the number of colors and flavors in @xmath2 gauge theories with dirac fermions in a given arbitrary representation of the gauge group we have shown that this theory is _ minimal _ in the sense that it is the theory with the smallest number of flavors ( above one ) which exhibits such walking dynamics @xcite .
the walking dynamics is expected to be dramatically different than in the qcd case . |
3,963 | Suppose that you have an abstract for a scientific paper: the mean - field dynamics of a bose gas is shown to break down at time @xmath0 where @xmath1 is the lyapunov exponent of the mean - field theory , @xmath2 is the number of bosons , and @xmath3 is a system - dependent constant .
the breakdown time @xmath4 is essentially the ehrenfest time that characterizes the breakdown of the correspondence between classical and quantum dynamics .
this breakdown can be well described by a quantum fidelity defined for one - particle reduced density matrices .
our results are obtained with the formalism in particle - number phase space and are illustrated with a triple - well model .
the logarithmic quantum - classical correspondence time may be verified experimentally with bose - einstein condensates . .
And you have already written the first three sentences of the full article: the nonlinear gross - pitaevskii equation ( gpe ) , as a mean - field theory , has been the dominant tool in describing the dynamics of bose - einstein condensates ( becs ) in ultracold atomic gases @xcite .
however , we face a quandary when the mean - field dynamics of a bec becomes dynamically unstable or chaotic @xcite : on one hand , one may regard this instability as an unphysical artifact resulted from the mean - field approximation , since the exact dynamics of a bec is governed by the many - body schrdinger equation , which is linear and thus does not allow chaos ; on the other hand , the dynamical instability was observed in experiments @xcite and it has been proved with mathematical rigor that the gpe describes correctly not only the ground state but also the dynamics of a bec in the large @xmath2 limit ( @xmath2 is the number of bosons ) @xcite . our aim in this work is to resolve this fundamental dilemma .
our study shows that the mean - field theory ( the gpe ) is only valid up to time _.
Please generate the next two sentences of the article | h = n + o(n ) , [ eq : timescale ] where @xmath1 is the lyapunov exponent of the mean - field dynamics and @xmath3 is a constant that depends only on systems . with this time scale ,
the dilemma is resolved : on one hand , in the large @xmath2 limit ( @xmath5 ) , @xmath4 goes to infinity and thus the gpe is always valid just as proved rigorously in ref . |
3,964 | Suppose that you have an abstract for a scientific paper: when cmb data are used to derive cosmological parameters , their very choice does matter : some parameter values can be biased if the parameter space does not cover the `` true '' model .
this is a problem , because of the difficulty to parametrize dark energy ( de ) physics .
we test this risk through numerical experiments .
we create artificial data for dynamical or coupled de models and then use mcmc techniques to recover model parameters , by assuming a constant de state parameter @xmath0 and no dm de coupling . for the de potential considered ,
no serious bias arises when coupling is absent . on the contrary , @xmath1 , and thence @xmath2 and @xmath3 ,
suffer a serious bias when the `` true '' cosmology includes even just a mild dm de coupling . until the dark components keep an unknown nature ,
therefore , it can be important to allow for a degree of freedom accounting for dm de coupling , even more than increasing the number of parameters accounting for the @xmath4 behavior . .
And you have already written the first three sentences of the full article: scarce doubts remain that dark energy ( de ) exists . not only snia data indicate an accelerated cosmic expansion ( perlmutter et al . 1997 , 1998 , riess et al .
1998 , foley et al . 2007 ) ; also cmb and deep sample data show a clear discrepancy between the total density parameter @xmath5 approaching unity , and the matter density parameter @xmath6@xmath7 ( see , _
e.g. _ , spergel et al ..
Please generate the next two sentences of the article | de covers this gap ; its state parameter @xmath8 must approach @xmath9 today , so apparently excluding that de is made of free particles ( @xmath10 : de pressure , energy density ) .
the true nature of de is however still elusive ; a false vacuum and a self interacting scalar field are among the most popular hypotheses for it ( wetterich 1988 , ratra & peebles 1988 ) . |
3,965 | Suppose that you have an abstract for a scientific paper: standard measures of batting performance such as a batting average and an on - base percentage can be decomposed into component rates such as strikeout rates and home run rates .
the likelihood of hitting data for a group of players can be expressed as a product of likelihoods of the component probabilities and this motivates the use of random effects models to estimate the groups of component rates .
this methodology leads to accurate estimates at hitting probabilities and good predictions of performance for following seasons .
this approach is also illustrated for on - base probabilities and fip abilities of pitchers . .
And you have already written the first three sentences of the full article: efron and morris ( 1975 ) demonstrated the benefit of simultaneous estimation using a simple example of using the batting outcomes of 18 players in the first 45 at - bats in the 1970 season to predict their batting average for the remainder of the season . essentially , improved batting estimates shrink the observed averages towards the average batting average of all players .
one common way of achieving this shrinkage is by means of a random effects model where the players underlying probabilities are assumed to come from a common distribution , and the parameters of this `` random effects '' distribution are assigned vague prior distributions . in modern sabermetrics research
, a batting average is not perceived to be a valuable measure of batting performance ..
Please generate the next two sentences of the article | one issue is that the batting average assigns each possible hit the same value , and it does not incorporate in - play events such as walks that are beneficial for the general goal of scoring runs .
another concern is that the batting average is a convoluted measure that combines different batting abilities such as not striking out , hitting a home run , and getting a hit on a ball placed in - play . |
3,966 | Suppose that you have an abstract for a scientific paper: cyclic dominance of species has been identified as a potential mechanism to maintain biodiversity , see e.g. b. kerr , m. a. riley , m. w. feldman and b. j. m. bohannan [ nature * 418 * , 171 ( 2002 ) ] and b. kirkup and m. a. riley [ nature * 428 * , 412 ( 2004 ) ] . through analytical methods supported by numerical simulations
, we address this issue by studying the properties of a paradigmatic non - spatial three - species stochastic system , namely the ` rock - paper - scissors ' or cyclic lotka - volterra model .
while the deterministic approach ( rate equations ) predicts the coexistence of the species resulting in regular ( yet neutrally stable ) oscillations of the population densities , we demonstrate that fluctuations arising in the system with a _ finite number of agents _ drastically alter this picture and are responsible for extinction : after long enough time , two of the three species die out . as main findings we provide analytic estimates and numerical computation of the extinction probability at a given time .
we also discuss the implications of our results for a broad class of competing population systems . .
And you have already written the first three sentences of the full article: understanding biodiversity and coevolution is a central challenge in modern evolutionary and theoretical biology @xcite . in this context , for some decades
much effort has been devoted to mathematically model dynamics of competing populations through nonlinear , yet deterministic , set of rate equations like the equations devised by lotka and volterra @xcite or many of their variants @xcite .
this heuristic approach is often termed as population - level description . as a common feature.
Please generate the next two sentences of the article | , these deterministic models fail to account for stochastic effects ( like fluctuations and spatial correlations ) .
however , to gain some more realistic and fundamental understanding on generic features of population dynamics and mechanisms leading to biodiversity , it is highly desirable to include internal stochastic noise in the description of agents kinetics by going beyond the classical deterministic picture . |
3,967 | Suppose that you have an abstract for a scientific paper: at high energy , the photoproduction or electroproduction of vector mesons allow to prepare a beam of quark - antiquark pairs of a given flavor . at high momentum transfer ,
the study of the scattering of these pairs on a nucleon opens up an original window on the quark - gluon structure of hadronic matter , which may eventually shed light on its gluonic content , on correlations between quarks and on the van der walls part of the interaction between hadrons . .
And you have already written the first three sentences of the full article: since a photon has the same quantum numbers as vector mesons , a beam of high energy photons is a beam of quark - antiquark pairs .
their flavor is selected by the kind of vector meson which is detected : light quarks for @xmath0 or @xmath1 , strange quarks for @xmath2 and charmed quarks for @xmath3 mesons .
the life time of the fluctuation @xmath4 is given by the uncertainty principle and increases with the beam energy @xmath5 : for instance , a 5 gev beam of real photons fluctuates into a beam of @xmath0 mesons over 4 fm ..
Please generate the next two sentences of the article | therefore , the interaction with matter of a beam of energetic photons is similar to the interaction of hadrons .
this is illustrated in fig . |
3,968 | Suppose that you have an abstract for a scientific paper: in this note we discuss metastability in a long - but - finite range disordered model for the glass transition .
we show that relaxation is dominated by configuration belonging to metastable states and associate an in principle computable free - energy barrier to the equilibrium relaxation time .
adam - gibbs - like relaxation times appear naturally in this approach . .
And you have already written the first three sentences of the full article: metastable states and configurational entropy , are central concepts in our understanding of low temperature relaxation of disordered and glassy systems @xcite . in presence of time scale separation between `` fast '' and `` slow '' degrees of freedom relaxation
is often described as a walk between metastable states , intended as regions of configuration space where the fast degrees of freedom reach a state of quasi equilibrium before the relaxation of slow degrees of freedom can effectively take place . according to the adam and gibbs theory @xcite the configurational entropy , i.e. the logarithm of the multiplicity of metastable states is related to the relaxation time by an inverse proportionality relation .
the relation between metastability and relaxation is well understood in infinite range spin glasses with `` random first order transition '' @xcite ..
Please generate the next two sentences of the article | the dynamics of these systems is exactly described by the equations of ideal mode coupling theory @xcite .
the mode coupling transition , spurious in liquid systems , is here driven by the existence of metastable states capable to trap the system for time scales diverging with the systems size . |
3,969 | Suppose that you have an abstract for a scientific paper: we estimate the maximum contribution to reionization from the first generation of massive stars , with zero metallicity , under the assumption that one of these stars forms with a fixed mass in every collapsed halo in which metal - free gas is able to cool .
we assume that any halo that has already had stars previously formed in one of their halo progenitors will form only stars with metals , which are assigned an emissivity of ionizing radiation equal to that determined at @xmath0 from the measured intensity of the ionizing background .
we examine the impact of molecular hydrogen photodissociation ( which tends to reduce cooling when a photodissociating background is produced by the first stars ) and x - ray photoheating ( which heats the atomic medium , raising the entropy of the gas before it collapses into halos ) .
we find that in the cdm@xmath1 model supported by present observations , and even assuming no negative feedbacks for the formation of metal - free stars , a reionized mass fraction of 50% is not reached until redshift @xmath2 .
the combination of ordinary metal - enriched stars and early metal - free stars can yield a cmb optical depth to electron scattering of at most @xmath3 .
the contribution of metal - free stars to the present cosmic infrared background is negligibly small . .
And you have already written the first three sentences of the full article: in the last few years , our understanding of the reionization history of the universe has greatly improved thanks to the detection of quasars at increasingly high redshift ( e.g. , becker et al .
2001 ; fan et al .
2002 ; hu et al ..
Please generate the next two sentences of the article | 2002 ; white et al .
2003 ) and the new data on the cosmic microwave background ( cmb ) radiation from wmap ( bennet et al . |
3,970 | Suppose that you have an abstract for a scientific paper: we propose a new seesaw model based on a fermionic hypercharge zero weak quintuplet in conjunction with an additional scalar quadruplet which attains an induced vacuum expectation value .
the model provides both tree - level seesaw @xmath0 and loop - suppressed radiative @xmath1 contributions to active neutrino masses .
the empirical masses @xmath2 ev can be achieved with @xmath3 tev new states , accessible at the lhc . for @xmath4 of accumulated integrated luminosity at the lhc , there could be @xmath5 doubly - charged @xmath6 or @xmath7 fermions with mass @xmath8 , leading to interesting multilepton signatures .
the neutral component of the fermion quintuplet , previously identified as a minimal dark matter candidate , becomes unstable in the proposed seesaw setup .
the stability can be restored by introducing a @xmath9 symmetry , in which case neutrinos get mass only from radiative contributions .
= 2 * * * * + = 0.5 kreimir kumeriki , ivica picek and branimir radovi + _ department of physics , faculty of science , university of zagreb , p.o.b .
331 , hr-10002 zagreb , croatia + _ + _ pacs _ : 14.60.pq ; 14.60.st ; 95.35.+d + _ keywords _ : neutrino mass ; exotic leptons ; dark matter .
And you have already written the first three sentences of the full article: we propose a seesaw model built upon the hypercharge zero fermionic weak quintuplet which , in isolation , provides a viable dark matter ( dm ) particle within the so - called minimal dark matter ( mdm ) model @xcite .
we explore the conditions under which the quintuplets @xmath10 could simultaneously generate the masses of the known neutrinos and provide a stable dm candidate .
the proposed model goes beyond the three tree - level realizations of weinberg s effective dimension - five operator @xmath11 @xcite : type i @xcite , type ii @xcite , and type iii @xcite seesaw mechanisms , mediated by a heavy fermion singlet , a scalar triplet , and a fermion triplet , respectively ..
Please generate the next two sentences of the article | a seesaw mediator of isospin larger than one has to be accompanied by a scalar multiplet larger than that of the standard model ( sm ) higgs doublet .
our previous model @xcite based on an exotic nonzero hypercharge weak quintuplet dirac fermion @xmath12 generates the neutrino masses both at the tree level and at the loop level . at the tree level it corresponds to dimension - nine seesaw operator which reproduces the empirical neutrino masses @xmath2 ev with @xmath13 few 100 gev states testable at the lhc , while for heavier masses , which are outside of the lhc reach , these exotic leptons generate radiative neutrino masses |
3,971 | Suppose that you have an abstract for a scientific paper: recent success in explaining several properties of the dusty torus around the central engine of active galactic nuclei has been gathered with the assumption of clumpiness .
the properties of such clumpy dusty tori can be inferred by analyzing spectral energy distributions ( seds ) , sometimes with scarce sampling given that large aperture telescopes and long integration times are needed to get good spatial resolution and signal .
we aim at using the information already present in the data and the assumption of clumpy dusty torus , in particular , the clumpy models of nenkova et al .
, to evaluate the optimum next observation such that we maximize the constraining power of the new observed photometric point .
to this end , we use the existing and barely applied idea of bayesian adaptive exploration , a mixture of bayesian inference , prediction and decision theories .
the result is that the new photometric filter to use is the one that maximizes the expected utility , which we approximate with the entropy of the predictive distribution . in other words
, we have to sample where there is larger variability in the seds compatible with the data with what we know of the model parameters .
we show that bayesian adaptive exploration can be used to suggest new observations , and ultimately optimal filter sets , to better constrain the parameters of the clumpy dusty torus models . in general , we find that the region between 10 and 200 @xmath0 m produces the largest increase in the expected utility , although sub - mm data from alma also prove to be useful .
it is important to note that here we are not considering the angular resolution of the data , which is key when constraining torus parameters .
therefore , the expected utilities derived from this methodology must be weighted with the spatial resolution of the data . [ firstpage ] methods : data analysis , statistical galaxies : active , nuclei , seyfert .
And you have already written the first three sentences of the full article: the unified model for active galaxies @xcite is based on the existence of a dusty toroidal structure surrounding the central region of active galactic nuclei ( agn ) . considering this geometry of the obscuring material ,
the central engines of type-1 agn can be seen directly , resulting in typical spectra with both narrow and broad emission lines , whereas in type-2 agn the broad line region ( blr ) is obscured .
the infrared ( ir ) range ( and particularly the mid - infrared ; mir ) is key to characterize the torus , since the dust reprocesses the optical and ultraviolet radiation generated in the accretion process and re - emits it in this range ..
Please generate the next two sentences of the article | however , considering the small torus size , high angular resolution turns to be essential to isolate as much as possible its emission .
pioneering work in modelling the dusty torus @xcite assumed a uniform dust density distribution to simplify the modelling , although from the start , @xcite realized that smooth dust distributions can not survive within the immediate agn vicinity . to solve the various discrepancies between observations and models , an intensive search for an alternative torus geometry |
3,972 | Suppose that you have an abstract for a scientific paper: we report the results from measuring the phase lag and coherence function of x - ray emission from black hole candidate ( bhc ) xte j1550 - 564 .
these x - ray temporal properties have been recognized to be increasingly important in providing important diagnostics of the dynamics of accretion flows around black holes . for xte j1550 - 564
, we found significant hard lag the x - ray variability in high energy bands _ lags _ behind that in low energy bands associated both with broad - band variability and quasi - periodic oscillation ( qpo ) . however , the situation is more complicated for the qpo : while hard lag was measured for the first harmonic of the signal , the fundamental component showed significant _
soft _ lag .
such behavior is remarkably similar to what was observed of microquasar grs 1915 + 105 .
the phase lag evolved during the initial rising phase of the 1998 outburst .
the magnitude of both the soft and hard lags of the qpo increases with x - ray flux , while the fourier spectrum of the broad - band lag varies significantly in shape .
the coherence function is relatively high and roughly constant at low frequencies , and begins to drop almost right after the first harmonic of the qpo .
it is near unity at the beginning and decreases rapidly during the rising phase .
also observed is that the more widely separated the two energy bands are the less the coherence function between the two .
it is interesting that the coherence function increases significantly at the frequencies of the qpo and its harmonics . we discuss the implications of the results on the models proposed for bhcs .
And you have already written the first three sentences of the full article: black hole candidates ( bhcs ) are characterized by rapid x - ray variability ( see recent reviews by van der klis 1995 and cui 1999a ) .
it is also common for bhcs that the variability at high energies lags behind that at low energies ( cui 1999a and references therein ) , which is often referred to as hard lag .
the hard lag is often attributed to thermal inverse - comptonization processes ( e.g. , miyatomo et al ..
Please generate the next two sentences of the article | 1988 ; hua & titarchuk 1996 ; kazanas et al . 1997 ; bttcher & liang 1998 ; hua et al .
1999 ) , which are generally thought to be responsible for producing the characteristic hard tail in the x - ray spectra of bhcs ( tanaka & lewin 1995 ) . in these models , |
3,973 | Suppose that you have an abstract for a scientific paper: dynamic circuits are well suited for applications that require predictable service with a constant bit rate for a prescribed period of time , such as cloud computing and e - science applications .
past research on upstream transmission in passive optical networks ( pons ) has mainly considered packet - switched traffic and has focused on optimizing packet - level performance metrics , such as reducing mean delay .
this study proposes and evaluates a dynamic circuit and packet pon ( dycappon ) that provides dynamic circuits along with packet - switched service .
dycappon provides @xmath0 flexible packet - switched service through dynamic bandwidth allocation in periodic polling cycles , and @xmath1 consistent circuit service by allocating each active circuit a fixed - duration upstream transmission window during each fixed - duration polling cycle .
we analyze circuit - level performance metrics , including the blocking probability of dynamic circuit requests in dycappon through a stochastic knapsack - based analysis . through this analysis
we also determine the bandwidth occupied by admitted circuits .
the remaining bandwidth is available for packet traffic and we conduct an approximate analysis of the resulting mean delay of packet traffic . through extensive numerical evaluations and verifying simulations we demonstrate the circuit blocking and packet delay trade - offs in dycappon . dynamic circuit switching ; ethernet passive optical network ; grant scheduling ; grant sizing ; packet delay ; stochastic knapsack . .
And you have already written the first three sentences of the full article: optical networks have traditionally employed three main switching paradigms , namely circuit switching , burst switching , and packet switching , which have extensively studied respective benefits and limitations @xcite . in order to achieve the predictable network service of circuit switching while enjoying some of the flexibilities of burst and packet switching ,
_ dynamic circuit switching _ has been introduced @xcite .
dynamic circuit switching can be traced back to research toward differentiated levels of blocking rates of calls @xcite ..
Please generate the next two sentences of the article | today , a plethora of network applications ranging from the migration of data and computing work loads to cloud storage and computing @xcite as well as high - bit rate e - science applications , e.g. , for remote scientific collaborations , to big data applications of governments , private organizations , and households are well supported by dynamic circuit switching @xcite
. moreover , gaming applications benefit from predictable low - delay service @xcite provided by circuits , as do emerging virtual reality applications @xcite . |
3,974 | Suppose that you have an abstract for a scientific paper: the system consisting of a self gravitating perfect fluid and scalar field is considered in detail .
the scalar fields considered are the quintessence and `` tachyonic '' forms which have important application in cosmology .
mathematical properties of the general system of equations are studied including the algebraic and differential identities as well as the eigenvalue structure .
the cauchy problem for both quintessence and the tachyon is presented .
we discuss the initial constraint equations which must be satisfied by the initial data .
a cauchy evolution scheme is presented in the form of a taylor series about the cauchy surface .
finally , a simple numerical example is provided to illustrate this scheme .
pacs numbers : 04.20.ex , 04.40.-b , 98.80jk + msc : 83f05 , 83c05 + key words : scalar fields , cauchy problem , relativity + .
And you have already written the first three sentences of the full article: in the arena of cosmology and stellar structure , the importance of the perfect fluid source can not be understated .
the assumption of large - scale isotropy will demand , via the field equations , that the stress - energy tensor supporting the universe possess the algebraic structure of a perfect fluid .
as well , cosmologies containing scalar fields have long been considered ..
Please generate the next two sentences of the article | the motivation being that the scalar field would represent some exotic component of matter , which could explain various puzzling phenomena presented by observational cosmology .
more recently , viable alternatives to the standard big bang theory have been put forward , the most promising of which involve an inflationary era at some early time . most of these theories invoke a scalar field to play the role of the inflaton in the early universe . at late times , the scalar field may again play an important role as a `` dark energy '' field . |
3,975 | Suppose that you have an abstract for a scientific paper: we describe the electromagnetic calorimeter built for the graal apparatus at the esrf .
its monitoring system is presented in detail .
results from tests and the performance obtained during the first graal experiments are given .
the energy calibration accuracy and stability reached is a small fraction of the intrinsic detector resolution . .
And you have already written the first three sentences of the full article: the graal beam line facility @xcite currently in operation at the esrf in grenoble , is the first source of high intensity and completely polarized @xmath0 rays in the energy range [email protected] gev .
this project has been realized , with the prevailing support of the istituto nazionale di fisica nucleare ( infn ) , to study polarization observables in photoproduction reactions including strangeness . the graal apparatus ( see fig .
1 ) , consists of a high resolution and large solid angle bgo electromagnetic calorimeter combined with multiwire proportional chambers ( mwpc ) that covers a solid angle range of almost 4@xmath2 . particles emitted at small angles are also detected by a scintillator wall , that is installed three meters from the target and permits particle identification by means of their time of flight and their energy loss in the scintillators ..
Please generate the next two sentences of the article | the particle identification in the central region is accomplished with a plastic scintillator barrel through the measurement of de / dx . in this paper
we describe the photon - detection system , which has been designed to measure the energy of @xmath0 and neutral mesons decaying in two or more photons ( @xmath3 , @xmath4 , @xmath5 , k@xmath6 , @xmath7 ) , with a good angular resolution . |
3,976 | Suppose that you have an abstract for a scientific paper: i first motivate why we may want to look at possible new physics contributions to @xmath0 given relatively clear experimental but unclear theoretical situations .
i reexamine the supersymmetric contribution to @xmath0 and find an important one generally missed in the literature .
based on rather model - independent arguments based on flavor symmetries , an estimate of the possible supersymmetric @xmath0 is given , which interestingly come around the reported values without fine - tuning . if the observed values are dominated by supersymmetry , it is likely to give interesting consequences on hyperon cp violation , @xmath1 , and neutron and electron electric dipole moments .
august 23 , 1999 lbnl-44172 + ucb - pth-99/32 + hep - ph/9908442 + .1 in * can @xmath2 be supersymmetric ? * 0.3 in hitoshi murayama@xmath3 0.05 in @xmath4__department of physics , university of california + berkeley , ca 94720 - 7300 _ _ 0.05 in and 0.05 in @xmath5__theoretical physics group , ms 50a-5101 + lawrence berkeley national laboratory , berkeley , ca 94720 _ _ .
And you have already written the first three sentences of the full article: the year 1999 has already seen impressive progress in flavor physics .
cdf reported the first measurement of @xmath6 from @xmath7 decay @xcite which strongly hints to cp violation in a system other than the neutral kaon system .
the situation of direct cp violation @xmath0 in the neutral kaon system used to be somewhat unclear , but ktev result @xcite and the na48 result reported at this meeting @xcite made the experimental situation basically settled ..
Please generate the next two sentences of the article | the numbers on @xmath2 reported are . ]
@xmath8 .various standard model estimates of @xmath2 in the literature . |
3,977 | Suppose that you have an abstract for a scientific paper: infrared modifications of general relativity ( gr ) can be revealed by comparing the mass of galaxy clusters estimated from weak lensing to that from infall kinematics .
we measure the 2d galaxy velocity distribution in the cluster infall region by applying the galaxy infall kinematics ( gik ) model developed by @xcite to two suites of @xmath0 and galileon modified gravity simulations . despite having distinct screening mechanisms , namely , the chameleon and the vainshtein effects , the @xmath0 and galileon clusters exhibit very similar deviations in their gik profiles from gr , with @xmath1 enhancement in the characteristic infall velocity at @xmath2 and @xmath3 broadening in the radial and tangential velocity dispersions across the entire infall region , for clusters with mass @xmath4 at @xmath5 .
these deviations are detectable via the gik reconstruction of the redshift
space cluster
galaxy cross
correlation function , @xmath6 , which shows @xmath7 increase in the characteristic line - of - sight distance @xmath8 at @xmath9 from gr predictions . with overlapping deep imaging and large redshift surveys in the future
, we expect that the gik modelling of @xmath10 , in combination with the stacked weak lensing measurements , will provide powerful diagnostics of modified gravity theories and the origin of cosmic acceleration .
galaxy : clusters : general galaxies : kinematics and dynamics cosmology : large - scale structure of universe .
And you have already written the first three sentences of the full article: the late time acceleration of the universe can be explained by modifying general relativity ( gr ) on cosmological scales , avoiding the need of invoking a cosmological constant @xmath11 or an exotic repulsive fluid ( a.k.a . , dark energy ) .
many popular modified gravity ( mg ) theories rely on an extra scalar field @xmath12 to mediate a fifth force , making the distributions and motions of galaxies different from those predicted by gr ( see * ? ? ?
* and references therein ) ..
Please generate the next two sentences of the article | in particular , the coherent infall of galaxies onto massive clusters will exhibit systematic deviations due to the enhanced gravitational forces .
@xcite ( 2013 , hereafter zw13 ) demonstrated that in @xmath13+gr simulations the velocity distribution of galaxies in the virial and infall regions of clusters ( hereafter abbreviated gik for galaxy infall kinematics ) is well described by a 2component velocity distribution model , which can be reconstructed from measurements of the redshift space cluster |
3,978 | Suppose that you have an abstract for a scientific paper: tunneling spectroscopy of a nb coupled carbon nanotube quantum dot reveals the formation of pairs of andreev bound states ( abs ) within the superconducting gap .
a weak replica of the lower abs is found , which is generated by quasi - particle tunnelling from the abs to the al tunnel probe .
an inversion of the abs - dispersion is observed at elevated temperatures , which signals the thermal occupation of the upper abs .
our experimental findings are well supported by model calculations based on the superconducting anderson model . .
And you have already written the first three sentences of the full article: the proximity effect in a superconductor coupled to a mesoscopic normal conductor leads to a wide range of new quantum phenomena .
these include andreev reflection at normal and superconductor interfaces , the formation of andreev bound states ( abs ) in confined geometries , and proximity - induced supercurrent flow through normal conductors.@xcite the recent experimental detection of individual andreev bound states@xcite as well as the efforts towards demonstrating majorana states in superconductor coupled nanostructures devices with strong spin - orbit interaction@xcite received significant experimental and theoretical interest and opened a new area of research .
quantum dots ( qds ) coupled to superconducting leads provide an ideal system to test the theoretical predictions on the interplay of abs with the kondo effect.@xcite a 0 to @xmath0 junction transition@xcite has been reported in s - qd - s systems by measuring the sign reversal ( positive to negative ) of the josephson supercurrent for even to odd occupation of the qd.@xcite theoretical calculations suggest that this quantum phase transition in the s - qd - s josephson junction devices is signaled also by the crossing of two andreev levels.@xcite depending on the ratio of the kondo temperature @xmath1 at the center of a coulomb valley and the superconducting gap energy @xmath2 , the abs display a crossing ( @xmath3 ) or a non - crossing ( @xmath4 ) dispersion @xmath5 as a function of gate voltage @xmath6 ..
Please generate the next two sentences of the article | these predictions have been confirmed by recent experimental studies using al - contacted semiconductor quantum dot / nanowire devices.@xcite it has also been predicted theoretically that there could be up to four abs for a single level model in the superconducting gap .
however the two outer abs may not be visible in the transport spectrum since they can merge with the continuum.@xcite so far most of the experimental studies of abs formation are limited to al as contacts material , which restricts these experiments to very low temperatures and magnetic fields . despite these earlier reports |
3,979 | Suppose that you have an abstract for a scientific paper: we formulate the double exchange ( de ) model for systems with @xmath0 orbital degeneracy , relevant for hole - doped cubic vanadates . in the relevant regime of strong on - site
coulomb repulsion @xmath1 we solve the model using two distinct mean - field approximations : hartree - fock , and mean - field applied to the formulation of the model in the kotliar - ruckenstein slave boson represenation .
we show how , due to the relative weakness of the de mechanism via @xmath0 degenerate orbitals , the anisotropic @xmath2-type antiferromagnetic metallic phase and the orbital liquid state can be stabilized .
this is contrasted with the de mechanism via @xmath3 degenerate orbitals which stabilizes the ferromagnetic order in the hole - doped regime of manganites .
the obtained results are in striking agreement with the observed magnetic structures and the collapse of the orbital order in the doped la@xmath4sr@xmath5vo@xmath6 , pr@xmath4ca@xmath5vo@xmath6 and nd@xmath4sr@xmath5vo@xmath6 . .
And you have already written the first three sentences of the full article: recently orbital degrees of freedom in the strongly correlated electron systems have attracted much attention @xcite due to their crucial role in the stability of the various magnetic phases in the mott insulators @xcite or in the partial explanation of the mott metal - insulator transition itself @xcite .
typical examples of such systems are the transition - metal oxides with partly filled @xmath3 or @xmath0 degenerate orbitals .
the remarkable feature of these oxides is the large on - site coulomb repulsion @xmath7 , with @xmath8 being the effective electron hopping . in case of the stoichiometric ( undoped ) oxides the coulomb repulsion between electrons supresses charge fluctuations and leads to the effective low - energy @xmath9 superexchange ( se ) interactions between spin _ and _ orbital degrees of freedom ..
Please generate the next two sentences of the article | in addition , the atomic hund s interaction @xmath10 aligns the spins of the electrons occupying the degenerate and almost degenerate orbitals on the same site and should be taken into account in the realistic se - type models .
interestingly , it is the hund s interaction which to large extent stabilizes particular spin ( magnetic ) _ and _ orbital order . |
3,980 | Suppose that you have an abstract for a scientific paper: we investigate the connections between the differential - geometric properties of the exponential map from the space of real skew symmetric matrices onto the group of real special orthogonal matrices and the manifold of real orthogonal matrices equipped with the riemannian structure induced by the frobenius metric . keywords .
skew symmetric and orthogonal matrices , singular value decomposition of skew symmetric matrices , pfaffian , exponential map , skew symmetric and principal logarithms , trace and frobenius metrics , riemannian manifolds , geodesic curves , diameter , pairs of ( weakly ) diametral orthogonal matrices .
mathematics subject classification ( 2010 ) : 15a16 , 53c22 . .
And you have already written the first three sentences of the full article: the _ exponential map _ induces a surjection from the vector space @xmath0 of real _ skew symmetric matrices _ of order @xmath1 and the manifold @xmath2 of real _ special orthogonal matrices _ of the same order .
the study and the explicit computation of the fibers of this map are relevant subjects in matrix theory and in its applications ( see for instance @xcite ) . here
we analyse some of their differential - geometric properties ..
Please generate the next two sentences of the article | the set of all _ real skew symmetric logarithms _ of @xmath3 ( i.e. the fiber over a matrix @xmath4 ) can be described in terms of the set @xmath5 of its _ real skew symmetric principal logarithms _ ( i.e. the real skew symmetric logarithms of @xmath4 with eigenvalues having absolute value in @xmath6 $ ] ) and of linear combinations with integer coefficients of suitable skew symmetric matrices ( theorem [ all_skew_symmetric_logarithms ] ) .
@xmath5 is ( implicitly ) studied in @xcite , where the so - called _ rodrigues exponential formula _ for skew symmetric matrices of order @xmath7 is extended to any order @xmath1 ( proposition [ rgx_exp_form ] ) ; we point out the role of the _ singular value decomposition _ of a skew symmetric matrix ( proposition [ svd ] and definition [ svd - system ] ) . also |
3,981 | Suppose that you have an abstract for a scientific paper: we consider the possibility of multiply - connected spacetimes , ranging from the flamm - einstein - rosen bridge , geons , and the modern renaissance of traversable wormholes .
a fundamental property in wormhole physics is the flaring - out condition of the throat , which through the einstein field equation entails the violation of the null energy condition . in the context of modified theories of gravity
, it has also been shown that the normal matter can be imposed to satisfy the energy conditions , and it is the higher order curvature terms , interpreted as a gravitational fluid , that sustain these non - standard wormhole geometries , fundamentally different from their counterparts in general relativity .
we explore interesting features of these geometries , in particular , the physical properties and characteristics of these ` exotic spacetimes ' . .
And you have already written the first three sentences of the full article: traversable wormholes are solutions to the einstein field equation that violate the classical energy conditions and are primarily useful as `` gedanken - experiments '' and as a theoretician s probe of the foundations of general relativity ( gr ) .
they are obtained by solving the einstein field equation in the reverse direction , namely , one first considers an interesting and exotic spacetime metric , then finds the matter source responsible for the respective geometry .
it is interesting to note that they allow `` effective '' superluminal travel , although the speed of light is not surpassed _ locally _ , and generate closed timelike curves , with the associated causality violations . in this rapporteur article , we consider a brief historical review ranging from the flamm - einstein - rosen bridge,@xcite to the geon wormhole - like structure obtained by wheeler in 1955,@xcite to the modern renaissance of wormhole physics.@xcite wormhole physics can originally be traced back to flamm in 1916,@xcite when he analyzed the then recently discovered schwarzschild solution ..
Please generate the next two sentences of the article | one finds next that wormhole - type solutions were considered , in 1935 , by einstein and rosen ( er),@xcite where they constructed an elementary particle model represented by a `` bridge '' connecting two identical sheets .
this mathematical representation of physical space being connected by a wormhole - type solution was denoted an `` einstein - rosen bridge '' . |
3,982 | Suppose that you have an abstract for a scientific paper: the pressure dependence of electronic structure , exchange interactions and curie temperature in ferromagnetic heusler alloy ni@xmath0mnsn has been studied theoretically within the framework of the density - functional theory .
the calculation of the exchange parameters is based on the frozen
magnon approach .
the curie temperature , t@xmath1 , is calculated within the mean field approximation by solving the matrix equation for a multi sublattice system . in agrement with experiment
the curie temperature increased from 362k at ambient pressure to 396 at 12 gpa . extending the variation of the lattice parameter beyond the range studied experimentally we obtained non
monotonous pressure dependence of the curie temperature and metamagnetic transition .
we relate the theoretical dependence of t@xmath1 on the lattice constant to the corresponding dependence predicted by the empirical interaction curve . the mn - ni atomic interchange observed experimentally
is simulated to study its influence on the curie temperature . .
And you have already written the first three sentences of the full article: the pressure dependence of the curie temperature provides important information on a ferromagnetic system and is an object of intensive studies both experimental @xcite and theoretical .
@xcite the key question here is the character of the variation of various magnetic properties with decreasing distances between magnetic atoms . in an early work ,
castellitz @xcite proposed an empirical rule ( interaction curve ) that describes the dependence of the curie temperature of the mn - containing ferromagnetic alloys with 4 - 5 valence electrons per molecule on the ratio @xmath2 where @xmath3 is the nearest - neighbor mn - mn distance and @xmath4 is the radius of the atomic mn 3d shell ..
Please generate the next two sentences of the article | the curve is supposed to represent the curie temperatures of various systems at ambient pressure as well as the pressure dependence of t@xmath1 of a given system .
the function is not monotonous and has a maximum at the @xmath2 value of about 3.6 ( see fig . |
3,983 | Suppose that you have an abstract for a scientific paper: we investigate the ism properties of 13 star - forming galaxies within the @xmath0 cosmos cluster .
we show that the cluster members have [ ] /h@xmath1 and [ ] /h@xmath2 emission - line ratios similar to @xmath0 field galaxies , yet systematically different emission - line ratios ( by @xmath3 dex ) from the majority of local star - forming galaxies .
we find no statistically significant difference in the [ ] /h@xmath1 and [ ] /h@xmath2 line ratios or ism pressures among the @xmath0 cluster galaxies and field galaxies at the same redshift . we show that our cluster galaxies have significantly larger ionization parameters ( by up to an order of magnitude ) than local star - forming galaxies .
we hypothesize that these high ionization parameters may be associated with large specific star formation rates ( i.e. a large star formation rate per unit stellar mass ) .
if this hypothesis is correct , then this relationship would have important implications for the geometry and/or the mass of stars contained within individual star clusters as a function of redshift . .
And you have already written the first three sentences of the full article: galaxy clusters formed by the collapse of the highest density peaks in primordial density fluctuations ( e.g. , * ? ? ?
* ; * ? ? ?
the cluster environment strongly affects the star - formation history of cluster members ..
Please generate the next two sentences of the article | galaxies in the centers of clusters are observed to be redder and more evolved than galaxies on the outskirts of the cluster , as well as field galaxies at the same redshift @xcite .
thus , the most massive clusters today likely formed in short episodes of vigorous star formation that effectively ceased by @xmath4 @xcite . theoretical simulations of cluster formation and evolution support this scenario @xcite . however , using old stellar populations to reconstruct the star formation conditions and to understand why star formation ceased in clusters is extremely difficult . |
3,984 | Suppose that you have an abstract for a scientific paper: we present a leading - order pqcd calculation of the helicity - flip @xmath0 matrix element @xmath1 ( coulomb quadrupole amplitude @xmath2 ) , taking into account the transverse momenta of the quarks and the contribution from the gluons . in the large @xmath3 limit ,
its scaling behavior acquires a double - logarithmic correction @xmath4 compared with the standard scaling analysis , due to the contribution from the orbital motion of the small-@xmath5 partons .
based on this and on the latest jlab experimental results of the @xmath6 ratio @xmath7 at @xmath3 = 3 @xmath8 4 gev@xmath9 , we make a phenomenological prediction for the latter at higher values of @xmath3 . .
And you have already written the first three sentences of the full article: in recent years , there have been continuing interests in the electromagnetic @xmath10 transition .
one of the earlier interests was due to the work of becchi and morpurgo @xcite . in that work
they had shown that in the context of the symmetric , non - relativistic , @xmath11 quark model , the transition @xmath12 is a pure magnetic dipole @xmath13 and the contribution from the electric quadrupole @xmath14 is zero ..
Please generate the next two sentences of the article | one crucial assumption in their derivation of this ` selection rule ' is that the quarks in both the nucleon and the delta are in the zero orbital angular momentum states .
these predictions were to be considered as a check to the validity of the quark model , which was still questionable in those days . |
3,985 | Suppose that you have an abstract for a scientific paper: we present keck near - infrared imaging of three binary l dwarf systems , all of which are likely to be sub - stellar .
two are lithium dwarfs , and a third exhibits an l7 spectral type , making it the coolest binary known to date .
all have component flux ratios near 1 and projected physical separations between 5 and 10 au , assuming distances of 18 to 26 pc from recent measurements of trigonometric parallax .
these surprisingly similar binaries represent the sole detections of companions in ten l dwarf systems which were analyzed in the preliminary phase of a much larger dual - epoch imaging survey .
the detection rate prompts us to speculate that binary companions to l dwarfs are common , that similar - mass systems predominate , and that their distribution peaks at radial distances in accord both with m dwarf binaries and with the radial location of jovian planets in our own solar system . to fully establish these conjectures against doubts raised by biases inherent in this small preliminary survey ,
however , will require quantitative analysis of a larger volume - limited sample which has been observed with high resolution and dynamic range .
subject headings : stars : circumstellar matter binaries : spectroscopic planetary systems .
And you have already written the first three sentences of the full article: l dwarfs make up a new spectral class of objects that are believed to have masses near or below the hydrogen - burning limit ( kirkpatrick et al . 1999a ; 1999b ) .
many satisfy currently accepted criteria for identification as _ bona fide _
brown dwarfs ( see tinney 1999 for a review ) ..
Please generate the next two sentences of the article | their local field detection rate in infrared sky surveys suggests they comprise a sizeable population which is well represented by an extension of the field - star mass function , @xmath0 , with @xmath1 ( reid et al . 1999 ) .
the occurrence frequency of multiplicity among these systems is completely unknown ; it is an open question as to whether the distribution of their companions matches that of m dwarfs or bears the stamp of a different , sub - stellar formation mechanism . |
3,986 | Suppose that you have an abstract for a scientific paper: as an alternative to the description of a toric variety by a fan in the lattice of one parameter subgroups , we present a new language in terms of what we call bunches these are certain collections of cones in the vector space of rational divisor classes .
the correspondence between these bunches and fans is based on classical gale duality .
the new combinatorial language allows a much more natural description of geometric phenomena around divisors of toric varieties than the usual method by fans does .
for example , the numerically effective cone and the ample cone of a toric variety can be read off immediately from its bunch . moreover
, the language of bunches appears to be useful for classification problems . .
And you have already written the first three sentences of the full article: the most important feature of a toric variety @xmath0 is that it is completely described by a fan @xmath1 in the lattice @xmath2 of one parameter subgroups of the big torus @xmath3 .
applying a linear gale transformation to the set of primitive generators @xmath4 of the rays @xmath5 of @xmath1 , gives a new vector configuration in a rational vector space @xmath6 .
this opens an alternative combinatorial approach to the toric variety @xmath0 : the vector space @xmath6 is isomorphic to the rational divisor class group of @xmath0 , and one can shift combinatorial information between the spaces @xmath7 and @xmath6 . in toric geometry , this principle has been used to study the projective case , compare @xcite : roughly speaking , if we consider all fans @xmath8 in @xmath2 having their rays among @xmath9 , then the ( quasi-)projective @xmath8 correspond to so called gelfand - kapranov - zelevinski cones in @xmath6 ..
Please generate the next two sentences of the article | these cones subdivide the cone generated by the gale transform of the vector configuration @xmath10 , and the birational geometry of the associated toric varieties is reflected by the position of their gelfand - kapranov - zelevinski cones . if one leaves the ( quasi-)projective setting , then there are generalizations of gelfand - kapranov - zelevinski cones , compare e.g. @xcite ; but so far there seems to be no concept which is simple enough to serve for practical purposes in toric geometry .
our aim is to fill this gap and to propose a natural combinatorial language which also works in the non quasiprojective case . |
3,987 | Suppose that you have an abstract for a scientific paper: free electron laser ( fel ) and collective atomic recoil laser ( carl ) are described by the same model of classical equations for properly defined scaled variables .
these equations are extended to the quantum domain describing the particle s motion by a schrdinger equation coupled to a self - consistent radiation field .
the model depends on a single collective parameter @xmath0 which represents the maximum number of photons emitted per particle .
we demonstrate that the classical model is recovered in the limit @xmath1 , in which the wigner function associated to the schrdinger equation obeys to the classical vlasov equation . on the contrary , for @xmath2 , a new quantum regime
is obtained in which both fels and carls behave as a two - state system coupled to the self - consistent radiation field and described by maxwell - bloch equations . .
And you have already written the first three sentences of the full article: apparently very different systems as high - gain free electron laser ( fel ) @xcite and collective atomic recoil laser ( carl ) @xcite exhibit similar behaviors , showing self - bunching and exponential enhancement of the emitted radiation . originally conceived in a semiclassical framework , they can be as well described quantum - mechanically @xcite .
however , it is not explicitly evident how to obtain the classical limit starting from the quantum description .
first attempts to give a quantum description of the fel have been proposed in the 80s , starting from a canonical quantization of the @xmath3-particle hamiltonian in the heisenberg picture , to study photon statistics and quantum initialization from vacuum in the linear regime @xcite . in 1988 , preparata proposed a quantum field theory of fel @xcite , in which he has shown that , for @xmath4 , the fel dynamics is solved by a single - electron schrdinger equation coupled to a self - consistent radiation mode ..
Please generate the next two sentences of the article | the same model has been recently obtained to describe carl from a bose - einstein condensate ( bec ) at zero temperature @xcite .
furthermore , it has been also proved experimentally @xcite that carl in a bec exhibits quantum recoil effects when the average recoil velocity remains less than the photon recoil limit . in this letter |
3,988 | Suppose that you have an abstract for a scientific paper: the ferropnictide superconductors exhibit a sensitive interplay between the lattice and magnetic degrees of freedom , including a number of phonon modes that are much softer than predicted by nonmagnetic calculations using density functional theory ( dft ) .
however , it is not known what effect , if any , the long - range magnetic order has on phonon frequencies above 23 mev , where several phonon branches are very closely spaced in energy and it is challenging to isolate them from each other .
we measured these phonons using inelastic time - of - flight neutron scattering in @xmath0 40 brillouin zones , and developed a technique to determine their frequencies .
we find this method capable of determining phonon energies to @xmath0 0.1 mev accuracy , and that the dft calculations using the experimental structure yield qualitatively correct energies and eigenvectors .
we do not find any effect of the magnetic transition on these phonons . .
And you have already written the first three sentences of the full article: the role of phonons in the mechanism of high - temperature superconductivity in ferropnictides remains poorly understood .
while density function theory ( dft ) calculations indicate that conventional electron - phonon coupling is not responsible for superconductivity @xcite , there is nevertheless a strong relationship between the lattice and electronic properties , including both magnetism and superconductivity .
for example , there is an isotope effect due to fe @xcite , and the superconducting temperature strongly depends upon the fe - as - fe bond angle @xcite ( or alternatively the height of the pnictogen atom above the plane of the transition metal@xcite ) ..
Please generate the next two sentences of the article | in addition , the lattice and magnetism are strongly coupled , which manifests in several ways .
first , in order to correctly refine the internal parameters of the structure , dft calculations must be performed with spin - polarization @xcite . |
3,989 | Suppose that you have an abstract for a scientific paper: a class of asymptotically free scalar theories with o(@xmath0 ) symmetry , defined via the eigenpotentials of the gaussian fixed point ( halpern - huang directions ) , are investigated using renormalization group flow equations .
explicit solutions for the form of the potential in the nonperturbative infrared domain are found in the large-@xmath0 limit . in this limit ,
potentials without symmetry breaking essentially preserve their shape and undergo a mass renormalization which is governed only by the renormalization group distance parameter ; as a consequence , these scalar theories do not have a problem of naturalness .
symmetry - breaking potentials are found to be `` fine - tuned '' in the large-@xmath0 limit in the sense that the nontrivial minimum vanishes exactly in the limit of vanishing infrared cutoff : therefore , the o(@xmath0 ) symmetry is restored in the quantum theory and the potential becomes flat near the origin . .
And you have already written the first three sentences of the full article: common belief holds that only polynomial interactions up to a certain degree depending on the spacetime dimension are renormalizable , in the sense that interactions of even higher order require an infinite number of subtractions in a perturbative analysis .
this can be attributed to the implicit assumption that the higher - order couplings , which in general are dimensionful , set independent scales .
such nonrenormalizable theories can only be defined with a cutoff scale @xmath1 , while the unknown physics beyond the cutoff is encoded in the ( thereby independent ) values of the couplings ..
Please generate the next two sentences of the article | starting from the viewpoint that the cutoff @xmath1 is the only scale in the theory , halpern and huang @xcite pointed out the existence of theories with higher - order and even nonpolynomial interactions within the conventional setting of quantum field theory .
this happens because the higher - order couplings , by assumption , are proportional to a corresponding power of @xmath2 and therefore die out sufficiently fast in the limit @xmath3 ; the theories remain perturbatively renormalizable in the sense that infinitely many subtractions are not required . perhaps most important |
3,990 | Suppose that you have an abstract for a scientific paper: in an equity market model with `` knightian '' uncertainty regarding the relative risk and covariance structure of its assets , we characterize in several ways the highest return relative to the market that can be achieved using nonanticipative investment rules over a given time horizon , and under any admissible configuration of model parameters that might materialize .
one characterization is in terms of the smallest positive supersolution to a fully nonlinear parabolic partial differential equation of the hamilton
jacobi
bellman type . under appropriate conditions ,
this smallest supersolution is the value function of an associated stochastic control problem , namely , the maximal probability with which an auxiliary multidimensional diffusion process , controlled in a manner which affects both its drift and covariance structures , stays in the interior of the positive orthant through the end of the time - horizon .
this value function is also characterized in terms of a stochastic game , and can be used to generate an investment rule that realizes such best possible outperformance of the market . and . . .
And you have already written the first three sentences of the full article: consider an equity market with asset capitalizations @xmath0 at time @xmath1 , and with covariance and relative risk rates @xmath2 and @xmath3 , respectively . at any given time @xmath4 , these rates are _ nonanticipative functionals _ of past - and - present capitalizations @xmath5 , @xmath6 ; they are not specified with precision but are , rather , subject to `` knightian uncertainty . '' to wit , for a given collection @xmath7 of nonempty compact and convex subsets on @xmath8 , where @xmath9 is the space of real , symmetric , positive definite @xmath10 matrices , and @xmath11 is the origin in @xmath12 , they are subject to the constraint @xmath13 in other words , the pair @xmath14 must take values at time @xmath4 inside the compact , convex set @xmath15 which is determined by the current location of the asset capitalization process ; but within this range , the actual value @xmath16 is allowed to depend on past capitalizations as well .
[ to put it a little differently : the constraint ( [ e.3 ] ) is not necessarily `` markovian , '' as long as the sets in ( [ 1.b ] ) are not singletons . ] under these circumstances , what is the highest return on investment relative to the market that can be achieved using nonanticipative investment rules , and with probability one under all possible market model configurations that satisfy the constraints of ( [ e.3 ] ) ?
what are the weights in the various assets of an investment rule that accomplishes this ? answers : subject to appropriate conditions , @xmath17 and @xmath18\\[-8pt ] \eqntext{i = 1 , \ldots , n , 0 \le t \le t,}\end{aligned}\ ] ] respectively . here.
Please generate the next two sentences of the article | the function @xmath19 $ ] is the smallest nonnegative solution , in the class @xmath20 , of the fully nonlinear parabolic partial differential inequality @xmath21 subject to the initial condition @xmath22 , with @xmath23 we use in ( [ fg ] ) , ( [ e.3.d ] ) and throughout this paper , the notation @xmath24 , @xmath25 , @xmath26 , @xmath27 and define @xmath28 we call the function @xmath29 the _ arbitrage function , _ as @xmath30 gives the smallest initial capital starting with which an investor , who uses nonanticipative investment rules , can match or outperform the market portfolio by time @xmath31 , if the initial configuration of asset capitalizations is @xmath32 at @xmath33 , and does so with probability one under any `` admissible '' market configuration that might materialize
. it is perhaps worth noting that this function @xmath29 is characterized almost entirely in terms of the prevalent covariance structure @xmath34 . |
3,991 | Suppose that you have an abstract for a scientific paper: two ways of possibly solving the angular momentum problem plaguing cold dark matter ( cdm ) _ ab initio _ simulations of disk galaxy formation are discussed : 1 ) stellar feedback processes and 2 ) warm dark matter ( wdm ) rather than cdm . in relation to the chemical evolution of disk galaxies our simulations indicate that in case 1 ) the first generation of _ disk _ stars formed in disk galaxies like the milky way should have an abundance about two dex below solar , in fairly good agreement with the lowest observed abundance of the metal - weak tail of the galactic thick disk . for the second case
no such statements can be made without further assumptions about the star - formation history of the galaxies .
we find that the @xmath0-band tully - fisher relation can be matched by wdm disk galaxy formation simulations provided @xmath1 0.8 for disk galaxies , which sommer - larsen & dolgov ( 1999 ) argue is a reasonable value .
finally it is discussed how the magnetic field strengths observed in galactic disks can be obtained through disk galaxy _ formation _ , as an alternative to the conventional dynamo hypothesis . .
And you have already written the first three sentences of the full article: the formation of galactic disks is one of the most important unsolved problems in astrophysics today . in the currently favored hierarchical clustering framework , disks form in the potential wells of dark matter halos as the baryonic material cools and collapses dissipatively .
fall & efstathiou ( 1980 ) have shown that disks formed in this way can be expected to possess the observed amount of angular momentum ( and therefore the observed spatial extent for a given mass and profile shape ) , but only under the condition that the infalling gas retain most of its original angular momentum . however , numerical simulations of this collapse scenario in the cold dark matter ( cdm ) cosmological context ( e.g. , navarro & benz 1991 , navarro & white 1994 , navarro , frenk , & white 1995 ) have so far consistently indicated that when only cooling processes are included the infalling gas loses too much angular momentum ( by over an order of magnitude ) and the resulting disks are accordingly much smaller than required by the observations .
this discrepancy is known as the _ angular momentum problem _ of disk galaxy formation ..
Please generate the next two sentences of the article | it arises from the combination of the following two facts : a ) in the cdm scenario the magnitude of linear density fluctuations @xmath2 increases steadily with decreasing mass scale @xmath3 leading to the formation of non - linear , virialized structures at increasingly early epochs with decreasing mass i.e. the hierarchical `` bottom - up '' scenario .
b ) gas cooling is very efficient at early times due to gas densities being generally higher at high redshift as well as the rate of inverse compton cooling also increasing very rapidly with redshift . |
3,992 | Suppose that you have an abstract for a scientific paper: observations have shown that the spatial distribution of satellite galaxies is not random , but rather is aligned with the major axes of central galaxies ( cgs ) .
the strength of the alignment is dependent on the properties of both the satellites and centrals .
theoretical studies using dissipationless @xmath0-body simulations are limited by their inability to directly predict the shape of cgs .
using hydrodynamical simulations including gas cooling , star formation , and feedback , we carry out a study of galaxy alignment and its dependence on the galaxy properties predicted directly from the simulations.we found that the observed alignment signal is well produced , as is the color dependence : red satellites and red centrals both show stronger alignments than their blue counterparts .
the reason for the stronger alignment of red satellites is that most of them stay in the inner region of the dark matter halo where the shape of the cg better traces the dark matter distribution .
the dependence of alignment on the color of cgs arises from the halo mass dependence , since the alignment between the shape of the central stellar component and the inner halo increases with halo mass .
we also find that the alignment of satellites is most strongly dependent on their metallicity , suggesting that the metallicity of satellites , rather than color , is a better tracer of galaxy alignment on small scales .
this could be tested in future observational studies . .
And you have already written the first three sentences of the full article: observations over the past decades have clearly shown that satellite galaxies ( sgs ) are not randomly distributed , but rather are anisotropically distributed around centrals . this characteristic is observed from our milky way galaxy ( e.g. , * ? ? ?
* ; * ? ? ?
* ) , the neighboring m31 @xcite , to large samples of local galaxies , and even in the virgo cluster@xcite . in particular , both the results of 2dfgrs and sloan digital sky survey ( sdss ) have shown that satellites are preferentially distributed along the major axes of centrals ..
Please generate the next two sentences of the article | this phenomenon is known as galaxy alignment ( e.g. , * ? ? ?
* ; * ? ? ? |
3,993 | Suppose that you have an abstract for a scientific paper: we construct aligned and unaligned stationary perturbation configurations in a composite system of stellar and coplanarly magnetized gaseous singular isothermal discs ( sids ) coupled by gravity .
this study extends recent analyses on ( magnetized ) sids of shu et al . , lou and lou & shen .
by this model , we intend to provide a conceptual framework to gain insights for multi - wavelength large - scale structural observations of disc galaxies .
both sids are approximated to be razor - thin and are in a self - consistent axisymmetric background equilibrium with power - law surface mass densities and flat rotation curves .
the gaseous sid is embedded with a coplanar azimuthal magnetic field @xmath0 of a radial scaling @xmath1 that is not force - free . in comparison with sid problems studied earlier , there
exist three possible classes of stationary solutions allowed by more dynamic freedoms . to identify physical solutions ,
we explore parameter space involving three dimensionless parameters : ratio @xmath2 of alfvn speed to sound speed in the magnetized gaseous sid , ratio @xmath3 for the square of the stellar velocity dispersion to the gas sound speed and ratio @xmath4 of the surface mass densities of the two sids . for both aligned and unaligned spiral cases with azimuthal periodicities @xmath5 , one of the three solution branches
is always physical , while the other two branches might become invalid when @xmath3 exceeds certain critical values .
for the onset criteria from an axisymmetric equilibrium to aligned secular bar - like instabilities , the corresponding @xmath6 ratio , which varies with @xmath2 , @xmath3 and @xmath4 , may be considerably lower than the oft - quoted value of @xmath7 , where @xmath8 is the total kinetic energy , @xmath9 is the total gravitational potential energy and @xmath10 is the total magnetic energy . for unaligned spiral cases ,
we examine marginal instabilities for axisymmetric ( @xmath11 ) and non - axisymmetric ( @xmath12 ) disturbances .
the....
And you have already written the first three sentences of the full article: in galactic contexts , we venture to formulate a theoretical magnetohydrodynamic ( mhd ) disc problem to explore possible large - scale structures and dynamics of stationary mhd density waves in a composite system of stellar and magnetized interstellar medium ( ism ) gas discs .
the two gravitationally coupled discs are treated as ` fluid ' and ` magnetofluid ' respectively and are both expediently approximated as razor - thin singular isothermal discs ( sids ) with the gaseous sid being embedded with a coplanar azimuthal magnetic field . for the gravitational effect of a massive axisymmetric dark matter halo , we prescribe a background composite system of two coupled partial sids ( syer & tremaine 1996 ; shu et al . 2000 ;
lou 2002 ; lou & shen 2003 ; shen & lou 2003 ) . in our model analysis , we construct stationary aligned and unaligned logarithmic spiral mhd perturbation configurations in a composite system of two sids with flat rotation curves , and attempt to relate various morphologies of disc galaxies , including barred and lopsided , barred and normal spiral structures . for possible observational diagnostics , we derive phase relationships among perturbation patterns of the stellar surface mass density , the gas surface mass density and the azimuthal magnetic field ..
Please generate the next two sentences of the article | this introduction serves two purposes .
the first one is to provide a general background information relevant to the problem at hand and the second one is to give reasons of pursuing this mhd disc problem . in a pioneering study of a composite system of stellar and gas discs coupled by gravity , |
3,994 | Suppose that you have an abstract for a scientific paper: the interaction of an expanding pair - electromagnetic pulse ( pem pulse ) with a shell of baryonic matter surrounding a black hole with electromagnetic structure ( embh ) is analyzed for selected values of the baryonic mass at selected distances well outside the dyadosphere of an embh .
the dyadosphere , the region in which a super critical field exists for the creation of @xmath0 pairs , is here considered in the special case of a reissner - nordstrom geometry .
the interaction of the pem pulse with the baryonic matter is described using a simplified model of a slab of constant thickness in the laboratory frame ( constant - thickness approximation ) as well as performing the integration of the general relativistic hydrodynamical equations .
the validation of the constant - thickness approximation , already presented in a previous paper ruffini , et al.(1999 ) for a pem pulse in vacuum , is here generalized to the presence of baryonic matter .
it is found that for a baryonic shell of mass - energy less than 1% of the total energy of the dyadosphere , the constant - thickness approximation is in excellent agreement with full general relativistic computations .
the approximation breaks down for larger values of the baryonic shell mass , however such cases are of less interest for observed gamma ray bursts ( grbs ) . on the basis of numerical computations of the slab model for pem pulses ,
we describe ( i ) the properties of relativistic evolution of a pem pulse colliding with a baryonic shell ; ( ii ) the details of the expected emission energy and observed temperature of the associated grbs for a given value of the embh mass ; @xmath1 , and for baryonic mass - energies in the range @xmath2 to @xmath3 the total energy of the dyadosphere . .
And you have already written the first three sentences of the full article: that vacuum polarization process _
la _ heisenberg - euler - schwinger ( @xcite , @xcite ) can occur in the field of a kerr newmann embh and that they naturally lead to a model for gamma - ray bursts was pointed out in @xcite .
the basic energetics of the process , governed by the christodoulou - ruffini mass formula , for an embh gives as shown in @xcite , @xmath4 with @xmath5 where @xmath6 and @xmath7 are respectively the mass energy , the angular momentum and the charge of the embh and @xmath8 is the irreducible mass , @xmath9 is the horizon radius , @xmath10 is the quasi - spheroidal cylindrical coordinate of the horizon evaluated at the equatorial plane and @xmath11 is the horizon surface area ..
Please generate the next two sentences of the article | extreme black holes satisfy the equality in eq.([s1 ] ) . the vacuum polarization process being `` reversible '' transformations in the sense of @xcite can extract an energy up to 29% of the mass - energy of an extremal rotating black hole and up to 50% of the mass - energy of an extremely magnetized and charged black hole .
although in general such a process is endowed with axial symmetry , in order to clarify the pure interplay of the gravitational and electrodynamical phenomena and also for simplicity , we have examined ( @xcite and @xcite ) the limiting cases of such a process in the field of a reissner - nordstrom geometry whose spherically symmetric metric is given by @xmath12 where @xmath13 \equiv - \alpha^2(r)$ ] and @xmath14 . |
3,995 | Suppose that you have an abstract for a scientific paper: for animals living in groups , one of the important questions is to understand what are the decision - making mechanisms that lead to choosing a motion direction or leaving an area while preserving group cohesion . here , we analyse the initiation of collective departure in zebrafish _
danio rerio_. in particular , we observed groups of 2 , 3 , 5 , 7 and 10 zebrafish swimming in a two resting sites arena and quantify the number of collective departure initiated by each fish .
while all fish initiated at least one departure , the probability to be the first one to exit a resting site is not homogeneously distributed with some individuals leading more departures than others .
we show that this number of initiation is linearly proportional to the number of attempts performed and that all fish have the same success rate to lead the group out of a resting sites after an attempt .
in addition , by measuring the average swimming speed of all fish , we highlight that the intra - group ranking of a fish for its proportion of initiation is correlated to its intra - group ranking in average speed .
these results highlight that the initiation of collective departure in zebrafish is a heterogeneously distributed process , even if all individual have the same success rate after attempting a departure . .
And you have already written the first three sentences of the full article: collective departure is a decision - making faced by all social species that travel in groups . in this process
, an individual generally initiates the movement of the group out of a residence site or towards a new direction .
the identity and motivation of this initiator can widely vary according to the social organisation of the considered species @xcite . on the one hand ,.
Please generate the next two sentences of the article | the leadership is often assumed by a unique or a subset of individuals that monopolise the decisions in hierarchical societies .
these individuals can be older @xcite , dominant @xcite or of a specific sex @xcite . |
3,996 | Suppose that you have an abstract for a scientific paper: we describe a simple procedure for reducing adc common noise in modular detectors that does not require additional hardware . a method using detector noise groups should work well for modular particle detectors such as segmented electromagnetic calorimeters , plastic scintillator hodoscopes , cathode strip wire chambers , segmented active targets , and the like .
we demonstrate a `` second pedestal noise correction '' method by comparing representative adc pedestal spectra for various elements of the pibeta detector before and after the applied correction .
pacs numbers : 07.50.h , 07.05.hd , 07.05.kf _ keywords : _ adc pedestals , correlated common noise , daq zero suppression psfig.sty , , .
And you have already written the first three sentences of the full article: experimental areas in particle accelerator facilities are notoriously noisy places due to beamline elements like magnets , slits , pumps , power supplies , and fans as well as other assorted electronics equipment that either runs continuously or is intermittently turning on and off .
all of the above may cause voltage ripples that significantly compromise photomultiplier tube ( pmt ) current pulses digitized by analog - to - digital converters ( adcs ) .
the problem is compounded especially in analysis of data from segmented detectors where total energy and/or direction of each measured particle are derived from smeared adc values of several adjacent detector modules ..
Please generate the next two sentences of the article | an experimenter might try to follow the recipes for reduction of pedestal noise couplings by designing recommended magnetic shielding and applying proper electrical grounding principles @xcite .
but such efforts are in practice usually met with only limited success . in order to minimize the electronic noise arising from `` dirty '' electrical grounds and from cross - talk between adjacent detector adc channels , |
3,997 | Suppose that you have an abstract for a scientific paper: we investigate the color - magnitude ( cm ) relation of galaxies in the distant x - ray selected cluster rdcs1252.92927 at @xmath0 using images obtained with the advanced camera for surveys ( acs ) on the _ hubble space telescope _ in the f775w and f850lp bandpasses .
we select galaxies based on morphological classifications extending about 3.5 mag down the galaxy luminosity function , augmented by spectroscopic membership information . at the core of the cluster
is an extensive early - type galaxy population surrounding a central pair of galaxies that show signs of dynamical interaction .
the early - type population defines a tight sequence in the cm diagram , with an intrinsic scatter in observed ( i_775-z_850)@xmath1 of @xmath2 mag based on 52 galaxies , or @xmath3 mag for @xmath430 ellipticals .
simulations using the latest stellar population models indicate an age scatter for the ellipticals of about 34% , with a mean age @xmath5 gyr ( corresponding to @xmath6 ) , and the last star formation occurring at @xmath7 transforming to rest - frame @xmath8 , we conclude that the slope and scatter in the cm relation for morphologically selected early - type galaxies show little or no evidence for evolution out to @xmath9 .
thus , elliptical galaxies were already well established in x - ray luminous clusters when the universe was a third of its present age . .
And you have already written the first three sentences of the full article: present - day cluster ellipticals are a remarkably well - behaved class of objects , with structural and chemical properties obeying simple power - law scaling relations . but
this could not always have been the case in a hierarchical universe . while most galaxy formation models can be tuned to reproduce these relations at @xmath10 , a more stringent test lies in reproducing their evolution with redshift .
to this end , it is important to study rich clusters out to the highest redshifts , when fractional age differences among the galaxies were proportionately greater . in recent years.
Please generate the next two sentences of the article | , deep wide - field optical surveys and deep serendipitous x - ray surveys have uncovered significant numbers of rich galaxy clusters to redshift unity and beyond ( see reviews by postman 2002 ; rosati 2003 ) .
these most distant , and most massive , of known gravitationally bound structures can then be studied in detail through targeted , high - resolution , follow - up optical and near - infrared observations . |
3,998 | Suppose that you have an abstract for a scientific paper: we consider a population of agents that are heterogeneous with respect to ( i ) their strategy when interacting @xmath0 times with other agents in an iterated prisoners dilemma game , ( ii ) their spatial location on @xmath1 different islands .
after each generation , agents adopt strategies proportional to their average payoff received . assuming a mix of two cooperating and two defecting strategies , we first investigate for isolated islands the conditions for an exclusive domination of each of these strategies and their possible coexistence .
this allows to define a threshold frequency for cooperation that , dependent on @xmath0 and the initial mix of strategies , describes the outbreak of cooperation in the absense of migration .
we then allow migration of a fixed fraction of the population after each generation . assuming a worst case scenario where all islands are occupied by defecting strategies , whereas only one island is occupied by cooperators at the threshold frequency , we determine the optimal migration rate that allows the outbreak of cooperation on _ all _ islands .
we further find that the threshold frequency divided by the number of islands , i.e. the relative effort for invading defecting islands with cooperators decreases with the number of islands .
we also show that there is only a small bandwidth of migration rates , to allow the outbreak of cooperation .
larger migration rates destroy cooperation . _
keywords : _ migration , cooperation , iterated prisoners dilemma .
And you have already written the first three sentences of the full article: _ human migration _ , i.e. the movement of large numbers of people out of , or into specific geographical areas ,
is seen as one of the biggest challenges that face the human societies in the 21st century .
on one hand , part of the human population has reasons to _ emigrate _ into countries which provide a `` better '' life on the other hand , industrialized countries can not sustain their current situation without the _ immigration _ of people ..
Please generate the next two sentences of the article | the real problem arises because the `` demand '' and the `` supply '' side can not be matched .
industrialized countries fear that immigrants do not contribute to their further economic growth but , on the contrary , deplete their wealth by taking advantage of a social security , health , and educational system which they did not contribute to . |
3,999 | Suppose that you have an abstract for a scientific paper: the discovery by bepposax and coordinated ground - based observations of persistent x - ray , visible and radio counterparts to grb has successfully concluded a search begin in 1973 , and the observed redshifted absorption lines have proved that grb are at cosmological distances .
the problem of explaining the mechanisms of grb and their persistent counterparts remains .
there are two classes of models : 1 ) grb continue weakly for days at all frequencies ; 2 ) grb emission shifts to lower frequencies as relativistic debris sweeps up surrounding gas ( in an `` external shock '' ) and slows .
1 ) predicts that the visible afterglow should be accompanied by continuing gamma - ray emission , as hinted by the high energy emission of grb940217 and the `` gang of four '' bursts of october 2729 , 1996 .
it also suggests that the persistent emission will fluctuate .
behavior of this sort may be found in `` internal shock '' models .
2 ) has been the subject of several theoretical studies which disagree in assumptions and details but which predict that at each frequency the flux should rise and then decline , with the maximum coming later at lower frequencies . some of this behavior has been observed , but data from grb970508 show that its afterglow can not be simply extrapolated from its gamma - ray emission .
it is likely that both classes of processes occur in most grb .
comparisons between grb show that they are not all scaled versions of the same event .
these results suggest that most gamma - ray emission is the result of `` internal shocks '' while most afterglow is the result of `` external shocks '' , and hint at the presence of collimated outflows .
self - absorption in the radio spectrum of grb970508 permitted the size of the radiating surface to be estimated , and in future grb it may be possible to follow the expansion of the shell in detail and to construct an energy budget . .
And you have already written the first three sentences of the full article: the visible , infrared and radio afterglows of grb970228 and grb970508 have taught us many things .
some of them are obvious : the absorption redshift @xmath0 of grb970508 established the cosmological distance scale of grb beyond any reasonable doubt , confirming the very strong case made on statistical grounds@xcite from batse data .
it is also evident that afterglows are very faint ..
Please generate the next two sentences of the article | this suggests that the simultaneous visible counterparts to grb , as yet unobserved , will also be faint , so that experiments designed to detect them will have to be very sensitive . the loss of the original hete , carrying an insensitive ultraviolet imager , may therefore have been fortunate , for it will be replaced by hete-2 which instead will carry a soft x - ray ccd which may yield important spectral information .
observations of afterglows can answer a number of harder questions too : 1 . |
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