id
int64 0
203k
| input
stringlengths 66
4.29k
| output
stringlengths 0
3.83k
|
|---|---|---|
12,000 |
Suppose that you have an abstract for a scientific paper: we show that a star orbiting close enough to an adiabatically grown supermassive black hole ( smbh ) can capture weakly interacting massive particles ( wimps ) at an extremely high rate .
the stellar luminosity due to annihilation of captured wimps in the stellar core may be comparable to or even exceed the luminosity of the star due to thermonuclear burning .
the model thus predicts the existence of unusual stars , essentially wimp burners , in the vicinity of a smbh .
we find that the most efficient wimp burners are stars with degenerate electron cores , e.g. white dwarfs ( wds ) ; such wds may have a very high surface temperature . if found , such stars would provide evidence for the existence of particle dark matter and can possibly be used to establish its density profile . on the other hand ,
the lack of such unusual stars may provide constraints on the wimp density near the smbh , as well as the wimp - nucleus scattering and pair annihilation cross - sections . .
And you have already written the first three sentences of the full article: the nature of the non - baryonic dark matter , which dominates the visible matter by about 4:1 , is perhaps the most interesting experimental challenge for contemporary particle astrophysics .
a hint for a solution has been found in particle physics where the wimps arise naturally in supersymmetric extensions of the standard model ( e.g. , * ? ? ?
* ) , among other possibilities ..
Please generate the next two sentences of the article
|
the wimp is typically defined as a stable , electrically neutral , massive particle . assuming that non - baryonic dark matter is dominated by wimps , the pair annihilation cross - section is related to the observed relic density @xcite .
a pair of wimps can annihilate producing ordinary particles and @xmath0-rays .
|
12,001 |
Suppose that you have an abstract for a scientific paper: this paper presents hyperbolic rank rigidity results for rank 1 , nonpositively curved spaces .
let @xmath0 be a compact , rank 1 manifold with nonpositive sectional curvature and suppose that along every geodesic in @xmath0 there is a parallel vector field making curvature @xmath1 with the geodesic direction .
we prove that @xmath0 has constant curvature equal to @xmath1 if @xmath0 is odd dimensional , or if @xmath0 is even dimensional and has sectional curvature pinched as follows : @xmath2 where @xmath3 .
when @xmath1 is the upper curvature bound this gives a shorter proof of the hyperbolic rank rigidity theorem of hamenstdt , subject to the pinching condition in even dimension ; in all other cases it is a new result .
we also present a rigidity result using only an assumption on maximal lyapunov exponents in direct analogy with work done by connell .
the proof of the main theorem is simplified considerably by assuming strict negative curvature ; in fact , in all dimensions but 7 and 8 it is then an immediate consequence of ergodicity of the @xmath4-frame flow . in these exceptional dimensions ,
recourse to the dynamics of the 2-frame flow must be made and the scheme of proof developed there can be generalized to deal with rank 1 , nonpositively curved spaces .
[ section ] [ thm]definition [ thm]lemma [ thm]proposition [ thm]remark .
And you have already written the first three sentences of the full article: rank rigidity was first proved in the higher euclidean rank setting by ballman @xcite and , using different methods , by burns and spatzier @xcite .
a manifold is said to have higher euclidean rank if a parallel , normal jacobi field can be found along every geodesic .
ballman and burns - spatzier proved that if an irreducible , compact , nonpositively curved manifold has higher euclidean rank , then it is locally symmetric ..
Please generate the next two sentences of the article
|
ballman s proof works for finite volume as well and the most general version of this theorem is due to eberlein and heber , who prove it under only a dynamical condition on the isometry group of @xmath0 s universal cover @xcite .
hamenstdt showed that a compact manifold with curvature bounded above by -1 is locally symmetric if along every geodesic there is a jacobi field making curvature -1 with the geodesic direction @xcite .
|
12,002 |
Suppose that you have an abstract for a scientific paper: in this paper we study the valuation problem of an insurance company by maximizing the expected discounted future dividend payments in a model with partial information that allows for a changing economic environment .
the surplus process is modeled as a brownian motion with drift .
this drift depends on an underlying markov chain the current state of which is assumed to be unobservable .
the different states of the markov chain thereby represent different phases of the economy .
+ we apply results from filtering theory to overcome uncertainty and then we give an analytic characterization of the optimal value function .
finally , we present a numerical study covering various scenarios to get a clear picture of how dividends should be paid out .
_ keywords : _ dividend maximization , hidden markov model , filtering theory , stochastic optimal control , viscosity solutions + mathematics subject classification ( 2010 ) : 91b30 , 91b70 , 93e20 + m. szlgyenyi + institute of statistics and mathematics , vienna university of economics and business , 1020 vienna , austria + [email protected] .
And you have already written the first three sentences of the full article: the classical risk measure for insurance companies is the probability of ruin .
this quantity is intensively studied , since in 1903 @xcite introduced his model for the surplus of an insurance company . however , in many models a trajectory can only either lead to ruin or tend to infinity .
hence , @xcite introduced expected discounted future dividend payments as a valuation principle for a homogeneous insurance portfolio , which builds an alternative risk measure ..
Please generate the next two sentences of the article
|
this concept originally comes from corporate finance , where the firm value is often determined by the accumulated future dividend payments .
our aim is to solve the valuation problem of an insurance company in these terms . since its introduction
|
12,003 |
Suppose that you have an abstract for a scientific paper: we propose to study the @xmath0 and the @xmath1 resonances in the @xmath2 decay via the final state interactions of the @xmath3 and @xmath4 pairs .
the weak interaction part proceeds through the @xmath5 quark decay process : @xmath6 , while the hadronization part takes place in two different mechanisms . in the first mechanism
, the @xmath7 cluster picks up a @xmath8 pair from the vacuum to form the @xmath9 meson - baryon pair while the @xmath10 pair from the weak decay hadronizes into a @xmath11 . in the second
, the @xmath7 cluster turns into a @xmath12 , while the @xmath10 pair from the @xmath5 decay picks up a @xmath8 pair and hadronizes into a meson - meson pair ( @xmath13 or @xmath14 ) .
because the final @xmath3 and @xmath4 states are in pure isospin @xmath15 and @xmath16 combinations , the @xmath2 decay can be an ideal process to study the @xmath0 and @xmath1 resonances . describing the final state interaction in the chiral unitary approach
, we find that the @xmath3 and @xmath4 invariant mass distributions , up to an arbitrary normalization , show clear cusp and peak structures , which can be associated with the @xmath0 and @xmath1 resonances , respectively .
the proposed mechanism can provide valuable information on the nature of these resonances and can in principle be test by facilities such as bepcii . .
And you have already written the first three sentences of the full article: understanding the nature of mesons and baryons has always been one of the most challenging topics in hadron physics .
the new observations @xcite have challenged the conventional wisdom that mesons are made of quark - antiquark pairs and baryons are composed of three quarks . in this respect , it is not surprising that both the @xmath0 state and the @xmath1 have generated a lot of interests in their true nature .
the @xmath0 has been suggested of being either a @xmath17 , a tetraquark state , a meson - meson molecule , a glueball , or a dynamically generated state @xcite ..
Please generate the next two sentences of the article
|
similarly , the @xmath1 has been found to be consistent with both a naive three quark picture and a molecular picture dynamically generated from @xmath9 and @xmath18 interactions . in the chiral unitary approach ,
the @xmath0 state was shown to be dynamically generated from the interaction of @xmath19 and @xmath20 treated as coupled channels in isospin @xmath21 @xcite .
|
12,004 |
Suppose that you have an abstract for a scientific paper: signature change at high density has been obtained as a possible consequence of deformed space - time structures in models of loop quantum gravity .
this article provides a conceptual discussion of implications for cosmological scenarios , based on an application of mathematical results for mixed - type partial differential equations ( the tricomi problem ) .
while the effective equations from which signature change has been derived are shown to be locally regular and therefore reliable , the underlying theory of loop quantum gravity may face several global problems in its semiclassical solutions .
some implications of signature - change + in cosmological models of loop quantum gravity + martin bojowald@xmath0 and jakub mielczarek@xmath1 + @xmath2institute for gravitation and the cosmos , the pennsylvania state university , + 104 davey lab , university park , pa 16802 , usa + @xmath3laboratoire de physique subatomique et de cosmologie , ujf , inpg , cnrs , in2p3 53 , avenue des martyrs , 38026 grenoble cedex , france + @xmath4institute of physics , jagiellonian university , ojasiewicza 11 , 30 - 348 cracow , poland + @xmath5department of fundamental research , national centre for nuclear research , + hoa 69 , 00 - 681 warsaw , poland .
And you have already written the first three sentences of the full article: anomaly - free effective models of loop quantum gravity , derived for spherically symmetric configurations @xcite and cosmological perturbations at high density @xcite , have revealed an unexpected phenomenon : at large curvature , signature change appears to be a generic feature of quantum space - time geometry as provided by this theory @xcite .
not only the general phenomenon but also the specific form of signature change seems to be universal in these models , giving further support of the genericness of the effect . for the typical form of `` holonomy modifications '' used widely in models of loop quantum gravity , the speed of physical modes differs from the classical speed of light by a factor of @xmath6 where @xmath7 is a function of the spatial geometry ( the metric @xmath8 ) , @xmath9 is a quantization parameter often assumed to be related to the planck length , and @xmath10 is a measure for extrinsic curvature ( or the hubble parameter in cosmological models ) . for large curvature @xmath11 ,
the speed is negative and commonly hyperbolic mode equations turn elliptic , which in these models are of the form @xmath12\ ] ] with source and lower - derivative terms @xmath13 $ ] ..
Please generate the next two sentences of the article
|
all modes @xmath14 , gravitational as well as matter , are affected in the same way .
the overall picture shows some relationships with other approaches to quantum cosmology , mainly the no - boundary proposal of hartle and hawking @xcite , and with other physical phenomena such as transonic flow or phases of nano - wires .
|
12,005 |
Suppose that you have an abstract for a scientific paper: the following question is addressed : under what conditions can a strange diffusive process , defined by a semi - dynamical v - langevin equation or its associated hybrid kinetic equation ( hke ) , be described by an equivalent purely stochastic process , defined by a continuous time random walk ( ctrw ) or by a fractional differential equation ( fde ) ? more specifically , does there exist a class of v - langevin equations with long - range ( algebraic ) velocity temporal correlation , that leads to a time - fractional superdiffusive process ?
the answer is always affirmative in one dimension .
it is always negative in two dimensions : any algebraically decaying temporal velocity correlation ( with a gaussian spatial correlation ) produces a normal diffusive process .
general conditions relating the diffusive nature of the process to the temporal exponent of the lagrangian velocity correlation ( in corrsin approximation ) are derived . .
And you have already written the first three sentences of the full article: * strange transport * has been the object of intense studies in recent years ( a very recent qualitative review is @xcite ) .
( we use the terminology `` strange transport '' @xcite rather than `` anomalous transport '' which is customary in dynamical systems theory , but has a different meaning in plasma transport theory ) .
the concept first appeared in the theory of stochastic processes , especially the theory of continuous time random walks ( * ctrw ) * @xcite , @xcite ..
Please generate the next two sentences of the article
|
consider a _ disordered _ system ( _ e.g. _ a turbulent fluid or plasma ) .
the position @xmath0 at time @xmath1 of one of its particles is determined by its interactions with the other particles and/or with external sources . in a strongly disordered system
|
12,006 |
Suppose that you have an abstract for a scientific paper: new experimental data on medium to heavy single @xmath0 hypernuclei revealed a much larger spin - orbit splitting than observed in older measurements of light hypernuclei . taking into account particle threshold effects and the density - dependence of in - medium coupling constants the apparent suppression of spin - orbit strength in light hypernuclei as well as the spin - orbit structure observed in medium to heavy nuclei
are explained in a unified manner within the density dependent relativistic hadron field theory .
it is concluded that the most valuable information on the @xmath0 spin - orbit dynamics in finite nuclei has to be extracted from medium to heavy mass nuclei .
hypernuclei , spin - orbit splitting 21.80.+a .
And you have already written the first three sentences of the full article: guided by experiment , e.g. in @xmath1c @xcite and @xmath2o @xcite it is a long standing opinion that the spin - orbit splitting of the @xmath0 single particle levels in @xmath0 hypernuclei should be very small or almost zero .
the most prominent theoretical explanation for this effect has been given through the quark - spin substructure of the @xmath0 leading to an additional @xmath0@xmath3 tensor coupling that almost exactly cancels the more conventional scalar - vector spin - orbit force of the @xmath0 single particle states in finite systems @xcite .
a reanalysis of older @xmath4c@xmath5 @xcite and @xmath6o@xmath5 @xcite proton emitter emulsion data by dalitz _.
Please generate the next two sentences of the article
|
_ , however , lead already to a remarkably bigger splitting , i.e. @xmath70.8 mev for @xmath1c and [email protected] mev for @xmath2o though the statistics was not so good .
new experiments at kek , measuring high resolution @xmath0 single - particle spectra for medium and heavy hypernuclei , show a spin - orbit splitting for the @xmath0 levels in the range of 12 mev @xcite .
|
12,007 |
Suppose that you have an abstract for a scientific paper: we investigate the natural families of periodic orbits associated with the equilibrium configurations of the the planar restricted @xmath0 body problem for the case @xmath1 equal mass satellites .
such periodic orbits can be used to model both trojan exoplanetary systems and parking orbits for captured asteroids within the solar system . for @xmath2
there are two families of periodic orbits associated with the equilibria of the system : the well known horseshoe and tadpole orbits . for @xmath3
there are three families that emanate from the equilibrium configurations of the satellites , while for @xmath4 there are six such families as well as numerous additional connecting families .
the families of periodic orbits are all of the horseshoe or tadpole type , and several have regions of neutral linear stability .
[ firstpage ] celestial mechanics planets and satellites : dynamical evolution and stability minor planets , asteroids : general .
And you have already written the first three sentences of the full article: the motion of small co - orbital satellites can be studied using the @xmath0 body problem .
this is a restricted version of the @xmath5 problem of one central mass with @xmath6 other masses in a ring surrounding it , which was first studied by @xcite as a model of the motion of the rings of saturn . in the restricted version ,
the @xmath6 orbiting masses @xmath7 interact with each other , but not the central mass @xmath8 i.e. the @xmath7 are infinitesimally small and @xmath9 tends to zero ..
Please generate the next two sentences of the article
|
the relative equilibria ( stationary configurations in a frame rotating with the co - orbiting satellites ) of both problems have been extensively studied in the context of central configurations : a configuration where the total ( newtonian ) acceleration of each body is proportional to the position vector of the body relative the centre of mass of the configuration . the simplest version of the restricted @xmath0 body problem is planar with the co - orbiting satellites in circular orbits with the same mean motion and same mass .
in this case the equilibrium configurations lie on a circle centred on the primary mass @xcite . for @xmath10
|
12,008 |
Suppose that you have an abstract for a scientific paper: new multi - core imaging fibre bundles hexabundles being developed at the university of sydney will provide simultaneous integral field spectroscopy for hundreds of celestial sources across a wide angular field .
these are a natural progression from the use of single fibres in existing galaxy surveys .
hexabundles will allow us to address fundamental questions in astronomy without the biases introduced by a fixed entrance aperture .
we have begun to consider instrument concepts that exploit hundreds of hexabundles over the widest possible field of view . to this end , we have compared the performance of a 61-core fully - fused hexabundle and 5 lightly - fused bundles with 7 cores each .
all fibres in the bundles have @xmath0 m cores . in the fully - fused bundle ,
the cores are distorted from a circular shape in order to achieve a higher fill fraction .
the lightly - fused bundles have circular cores and five different cladding thicknesses which affect the fill fraction .
we compare the optical performance of all 6 bundles and find that the advantage of smaller interstitial holes ( higher fill fraction ) is outweighed by the increase in modal coupling , cross - talk and the poor optical performance caused by the deformation of the fibre cores .
uniformly high throughput and low cross - talk are essential for imaging faint astronomical targets with sufficient resolution to disentangle the dynamical structure
. devices already under development will have between 100 and 200 lightly - fused cores , although larger formats are feasible .
the light - weight packaging of hexabundles is sufficiently flexible to allow existing robotic positioners to make use of them .
[ firstpage ] instrumentation : miscellaneous : hexabundles techniques : miscellaneous methods : observational instrumentation : spectrographs techniques : imaging spectroscopy . .
And you have already written the first three sentences of the full article: current and planned cosmological surveys in the optical and infrared have fundamental limitations .
multi - fibre [ e.g. 2df @xcite and sdss @xcite ] and multi - slit [ e.g. deimos @xcite and vimos @xcite ] surveys have or will amass large catalogues of galaxies in order to deduce their global properties .
however these suffer from biases introduced when a fixed angular size aperture such as a single fibre is used to observe galaxies , irrespective of the size , distance or morphology ( see for example , fig.8 in * ? ? ?.
Please generate the next two sentences of the article
|
* ) . on the other hand , integral field units ( ifus ) like teifu @xcite and gmos @xcite or image slicers such as sinfoni @xcite and nifs @xcite spatially sample the spectra , giving morphological and dynamical information
however , current ifus are restricted in the number of objects that can be observed .
|
12,009 |
Suppose that you have an abstract for a scientific paper: we introduce a tomography approach to describe the optical response of a cavity quantum electrodynamics device , beyond the semiclassical image of polarization rotation , by analyzing the polarization density matrix of the reflected photons in the poincar sphere . applying this approach to an electrically - controlled quantum dot - cavity device
, we show that a single resonantly - excited quantum dot induces a large optical polarization rotation by 20@xmath0 in latitude and longitude in the poincar sphere , with a polarization purity remaining above 84@xmath1 .
the quantum dot resonance fluorescence is shown to contribute to the polarization rotation via its coherent part , whereas its incoherent part contributes to degrading the polarization purity . in the development of quantum photonic networks ,
a crucial challenge is to demonstrate highly - efficient interfaces allowing the coherent transfer of quantum information between a stationary qubit and a flying one @xcite . in this context
, it has been shown that a single natural or artificial atom in a cavity quantum electrodynamics ( cqed ) system can induce giant phase shifts on incoming photons @xcite : this allowed the recent implementation of atom - photon gates @xcite and , subsequently , photon - photon gates @xcite .
most of these achievements are based on polarization - encoding protocols @xcite , in which the optical phase shift is used to rotate the polarization state of the outgoing photons .
polarization rotation is also at the heart of numerous quantum computation proposals based on spin - photon logic gates , where a stationary spin qubit is used as a quantum memory with a long coherence time @xcite .
by essence , these concepts of optical phase shift and polarization rotation rely on a semiclassical image , considering that the optical response of the atom - based device is entirely coherent . yet
, the output photonic field includes a contribution from the resonance fluorescence emitted by the natural or....
And you have already written the first three sentences of the full article: using the input - output formalism @xcite , we define @xmath18 the operator describing the incident @xmath14-polarized field , @xmath25 and @xmath26 the operators describing the @xmath13- and @xmath14-polarized output fields .
we also define the dimensionless intracavity fields @xmath98 and @xmath99 for both polarizations .
the continuity relations between these operators write : @xmath100 with @xmath76 the cavity intensity damping rate through the top mirror . + from these operators , one can define the output operators @xmath101 and @xmath102 in the diagonal / antidiagonal basis , @xmath103 and @xmath104 in the left - handed / right - handed circular basis : @xmath105 with these notations the intensity @xmath106 , i.e. the number of output photons per unit time in polarization @xmath107 ( with @xmath108 ) , is given by @xmath109 ..
Please generate the next two sentences of the article
|
this intensity is generally higher than @xmath110 , which only describes the coherent part of the @xmath107-polarized output field .
we schematize in fig .
|
12,010 |
Suppose that you have an abstract for a scientific paper: we derive a non - local four - fermi term with a linear potential from yang - mills theory in a stochastic background .
the stochastic background is a class of classical configuration derived from the non - linear gauge . .
And you have already written the first three sentences of the full article: the structure of the vacuum plays a key role in understanding physical phenomena .
for example , qed and the asymptotic freedom phase of non - abelian gauge theory are based on the trivial vacuum @xmath0 and the physical vector fields , the transverse photon / gluon , are clearly exposed by using the coulomb gauge .
confinement , on the other hand , is believed to be a non - perturbative vacuum phenomenon that is not yet clearly understood ..
Please generate the next two sentences of the article
|
presently , there are two confinement mechanisms discussed extensively in the literature .
these are the magnetic monopoles@xcite and vortices@xcite , which are related to the maximal abelian gauge@xcite and maximal central gauge@xcite , respectively .
|
12,011 |
Suppose that you have an abstract for a scientific paper: we describe an all - optical scheme for spin manipulation in the ground - state triplet of the negatively charged nitrogen - vacancy ( nv ) center in diamond .
virtual optical excitation from the @xmath0 ground state into the @xmath1 excited state allows for spin rotations by virtue of the spin - spin interaction in the two - fold orbitally degenerate excited state .
we derive an effective hamiltonian for optically induced spin - flip transitions within the ground state spin triplet due to off - resonant optical pumping .
furthermore , we investigate the spin qubit formed by the zeeman sub - levels with spin projection @xmath2 and @xmath3 along the nv axis around the ground state level anticrossing with regard to full optical control of the electron spin . .
And you have already written the first three sentences of the full article: nitrogen - vacancy ( nv ) centers in diamond have attracted much attention in research related to quantum computation @xcite due to their key advantages , such as high stability and long spin coherence times @xcite up to room temperature and beyond @xcite .
the spin coherence time can be increased further by isotopic engineering @xcite since only the @xmath4 carbon atoms have non - zero nuclear spin , thus contributing to spin decoherence due to hyperfine coupling . under resonant optical excitation
the @xmath5 center exhibits a strong and highly stable zero phonon line at @xmath6 ev @xcite with an excited state lifetime of about @xmath7 @xcite ..
Please generate the next two sentences of the article
|
electron spin resonance analysis of the center has shown that both ground state and excited state are spin triplets , which implies that there is an even number of active electrons involved .
the ground state levels with spin projection @xmath2 and @xmath3 along the nv axis become degenerate in a magnetic field of about @xmath8 g. optical pumping causes a spin polarization of the ground state @xcite that can be attributed to a spin - orbit induced intersystem crossing with an intermediate singlet state@xcite .
|
12,012 |
Suppose that you have an abstract for a scientific paper: the complex structure and magnetism of pr@xmath0bi@xmath1ru@xmath2o@xmath3 was investigated by neutron scattering and exafs .
pr has an approximate doublet ground - state and the first excited state is a singlet .
this overall crystal field level scheme is similar to metallic pr@xmath2ir@xmath2o@xmath3 , which is also reported here .
while the b - site ( ru ) is well ordered throughout , this is not the case for the a - site ( pr / bi ) .
a distribution of the pr - o2 bond length indicates the pr environment is not uniform even for @xmath4 .
the bi environment is highly disordered ostensibly due to the 6s lone pairs on bi@xmath5 .
correspondingly we find the non - kramers doublet ground state degeneracy otherwise anticipated for pr in the pyrochlore structure is lifted so as to produce a quadrupolar singlet ground state with a spatially varying energy gap . for @xmath4 , below t@xmath6 , the ru sublattice orders antiferromagnetically , with propagation vector * * k**= ( 0,0,0 ) , as for y@xmath2ru@xmath2o@xmath3 . no ordering associated with the pr sublattice is observed down to 100 mk
. the low energy magnetic response of pr@xmath0bi@xmath1ru@xmath2o@xmath3 features a broad spectrum of magnetic excitations associated with inhomogeneous splitting of the pr quasi - doublet ground state . for @xmath4 ( @xmath7 )
the spectrum is temperature dependent ( independent ) .
it appears disorder associated with bi alloying enhances the inhomogeneous pr crystal field level splitting so that inter - site interactions become irrelevant for @xmath7 .
the structural complexity for the a - site may be reflected in the hysteretic uniform magnetization of b - site ruthenium in the nel phase . .
And you have already written the first three sentences of the full article: in pyrochlore materials , with the general formula a@xmath2b@xmath2o@xmath3 , the a and b site ions form an interpenetrating network of corner - sharing tetrahedra .
@xcite when populated by magnetic ions with nearest neighbor antiferromagnetic ( afm ) interactions these materials display anomalous frustrated magnetism .
@xcite for classical spins and nearest neighbor interactions the ground - state is a manifold characterized by zero magnetization on every tetrahedron ..
Please generate the next two sentences of the article
|
@xcite correspondingly pyrochlore magnets remain paramagnetic to much lower temperatures than their curie - weiss temperature ( @xmath8 ) where the collective properties are determined by longer range or anisotropic interactions and thermal and/or quantum fluctuations .
the resulting low temperature phases include spin - glasses , spin - liquids , and magneto - elastically induced nel order .
|
12,013 |
Suppose that you have an abstract for a scientific paper: magnetic and magneto - functional behavior of a fe - doped mnnige alloy with nominal composition mn@xmath0fe@xmath1nige have been investigated in ambient as well as in high pressure condition .
the alloy undergoes first order martensitic phase transition ( mpt ) around 200 k and also shows large conventional magnetocaloric effect ( mce ) ( @xmath2 @xmath3 -21 j / kg - k for magnetic field ( @xmath4 ) changing from 0 - 50 koe ) around the transition in ambient condition .
application of external hydrostatic pressure ( @xmath5 ) results a shift in mpt towards the lower temperature and a clear decrease in the saturation moment of the alloy at 5 k. the peak value of mce is also found to decrease with increasing external @xmath5 ( @xmath3 18 j / kg - k decrease in @xmath2 has been observed for @xmath5 = 12.5 kbar ) .
the most interesting observation is the occurance of exchange bias effect ( ebe ) on application of external @xmath5 .
the competing ferromagnetic and antiferromagnetic interaction in presence of external @xmath5 plays the pivotal role towards the observation of @xmath5 induced ebe . .
And you have already written the first three sentences of the full article: magnetic equiatomic alloys ( meas ) of general formula mm@xmath6x ( m , m@xmath6 = transition metals , x = si , ge , sn etc . ) and their derivatives have attracted renewed attentions for the observation of fascinating magneto - functional and physical properties such as , large magneticaloric effect ( mce ) , exchange bias effect ( ebe ) , spin glass ( sg ) like ground state etc .
@xcite among various members of meas , mnnige is one of the potential candidates which undergoes a first - order diffusionless structural phase transition , known as martensitic phase transition ( mpt ) , at 470 k during cooling and orders spiral antiferromagnetically below 346 k. @xcite physical and chemical pressures are the two most influencing parameters that can affect the physical properties of these materials simply by modifying structural parameters like lattice volume , bond angle etc .
@xcite among these two , chemical pressure approach ( different doping studies ) is much popular among the researchers due to easy sample preparation and measurement options ..
Please generate the next two sentences of the article
|
however , the purest form of perturbation can only be given by the physical pressure approach . since mea s discovery , several doping studies ( chemical pressure effect )
have been performed to increase the magneto - functional properties by reducing the structural transition temperature below its magnetic transition .
|
12,014 |
Suppose that you have an abstract for a scientific paper: single crystals of @xmath0 are grown out of fe-(nd , ce ) flux .
chemical and structural analysis of the crystals indicates that @xmath0 forms a solid solution until at least @xmath1 with a vegard - like variation of the lattice constants with @xmath2 .
refinements of single crystal neutron diffraction data indicate that ce has a slight site preference ( 7:3 ) for the @xmath3 rare earth site over the @xmath4 site .
magnetization measurements show that for @xmath5 the saturation magnetization at 400 k , a temperature important to applications , falls from 29.8 for the parent @xmath6 to 27.6 @xmath7/f.u . , the anisotropy field decreases from 5.5 t to 4.7 t , and the curie temperature decreases from 586 to 543 k. first principles calculations carried out within density functional theory are used to explain the decrease in magnetic properties due to ce substitution . though the presence of the lower - cost and more abundant ce slightly affects these important magnetic characteristics , this decrease is not large enough to affect a multitude of applications .
ce - substituted @xmath6 is therefore a potential high - performance permanent magnet material with substantially reduced nd content . .
And you have already written the first three sentences of the full article: the reduction of critical materials present in consumer and industrial products in general , and in rare earth ( re ) -based permanent magnets in particular , is a pressing concern due to increasing demand and a decline and/or uncertainty in the supply chain of these materials .
dysprosium , judged to be the most critical of these elements @xcite , is substituted onto the nd site in @xmath6 ( 2 - 14 - 1 ) permanent magnets to increase the value of their coercive field and maximum operating temperatures @xcite .
depending on the application , the amount of dy added can be large , in the range of 1.4 - 8.7 wt% @xcite . the highest temperature applications , those that rely on the greatest quantities of dysprosium , are required by the rapidly emerging technologies of wind turbines , magnetically levitated transport , and traction motors for hybrid and electric cars @xcite ..
Please generate the next two sentences of the article
|
though dy is indeed considered the most critical element , by many criteria nd is not that far behind on the list @xcite .
it is therefore imperative that new and innovative solutions are applied to the synthesis of permanent magnets that contain more abundant elements . to this end , recent work by pathak @xmath8 @xmath9 .
|
12,015 |
Suppose that you have an abstract for a scientific paper: cherenkov telescopes have the capability of detecting high energy tau neutrinos in the energy range of 11000pev by searching for very inclined showers .
if a tau lepton , produced by a tau neutrino , escapes from the earth or a mountain , it will decay and initiate a shower in the air which can be detected by an air shower fluorescence or cherenkov telescope . in this paper , we present detailed monte carlo simulations of corresponding event rates for the veritas and two proposed cherenkov telescope array sites : meteor crater and yavapai ranch , which use representative agn neutrino flux models and take into account topographic conditions of the detector sites .
the calculated neutrino sensitivities depend on the observation time and the shape of the energy spectrum , but in some cases are comparable or even better than corresponding neutrino sensitivities of the icecube detector . for veritas and the considered cherenkov telescope array sites the expected neutrino sensitivities are up to factor 3 higher than for the magic site because of the presence of surrounding mountains . .
And you have already written the first three sentences of the full article: neutrinos have long been anticipated to help answering some fundamental questions in astrophysics like the mystery of the source of the cosmic rays ( for a general discussion see @xcite ) .
for neutrinos in the tev range , prime source candidates are galactic supernova remnants @xcite .
neutrinos in the pev range and above are suspected to be produced by active galactic nuclei ( agn ) and gamma ray bursts ( grb ) with many agn models predicting a significant neutrino flux @xcite ..
Please generate the next two sentences of the article
|
recently , the icecube collaboration has reported the very first observation of a cosmic diffuse neutrino flux which lies in the 100 tev to pev range @xcite .
individual sources , however , could not be identified up to now .
|
12,016 |
Suppose that you have an abstract for a scientific paper: we present the results of band structure calculations for @xmath0cr@xmath1 ( @xmath0=zn , cd , hg and @xmath2=o , s , se ) spinels .
effective exchange coupling constants between cr spins are determined by fitting the energy of spin spirals to a classical heisenberg model .
the calculations reproduce the change of the sign of the dominant nearest - neighbor exchange interaction @xmath3 from antiferromagnetic in oxides to ferromagnetic in sulfides and selenides .
it is verified that the ferromagnetic contribution to @xmath3 is due to indirect hopping between cr @xmath4 and @xmath5 states via @xmath2 @xmath6 states .
antiferromagnetic coupling between 3-rd cr neighbors is found to be important in all the @xmath0cr@xmath1 spinels studied , whereas other interactions are much weaker .
the results are compared to predictions based on the goodenough - kanamori rules of superexchange . .
And you have already written the first three sentences of the full article: chromium spinels provide unrivalled possibilities for studying magnetic interactions in solids . in these compounds with a general formula @xmath0cr@xmath1 , where @xmath0 is a divalent nonmagnetic cation ( mg , zn , cd , or hg ) and @xmath2 is a divalent anion ( o , s , or se ) , a cr@xmath7 ion is in the 3@xmath8 configuration .
its three 3@xmath9 electrons occupy the majority - spin states of a completely spin polarised @xmath4 sub - shell leading to the total spin @xmath10=3/2 .
although charge and orbital degrees of freedom in the @xmath0cr@xmath1spinels are frozen , these compounds show wide variety of magnetic properties ranging from those of a strongly frustrated antiferromagnet to a heisenberg ferromagnet . depending on the chemical composition their effective curie - weiss temperature ( @xmath11 ) varies from @xmath12400 k in oxides to 200 k in selenides,@xcite which indicates that the sign of the dominant exchange interaction changes from antiferromagnetic ( afm ) to a ferromagnetic ( fm ) one . in the @xmath0cr@xmath13o@xmath14 spinels afm.
Please generate the next two sentences of the article
|
nearest - neighbor interactions between cr spins residing on a pyrochlore lattice are geometrically frustrated .
the magnetic ground state of a frustrated antiferromagnet is highly degenerate which leads to unusual low - temperature properties .
|
12,017 |
Suppose that you have an abstract for a scientific paper: the magnetic permeability of a ferrite is an important factor in designing devices such as inductors , transformers , and microwave absorbing materials among others . due to this
, it is advisable to study the magnetic permeability of a ferrite as a function of frequency .
when an excitation that corresponds to a harmonic magnetic field * h * is applied to the system , this system responds with a magnetic flux density * b * ; the relation between these two vectors can be expressed as * b * = @xmath0 * h * . where @xmath1 is the magnetic permeability . in this paper ,
ferrites were considered linear , homogeneous , and isotropic materials .
a magnetic permeability model was applied to nizn ferrites doped with yttrium .
the parameters of the model were adjusted using the genetic algorithm . in the computer science field of artificial intelligence , genetic algorithms and machine learning
does rely upon nature s bounty for both inspiration nature s and mechanisms .
genetic algorithms are probabilistic search procedures which generate solutions to optimization problems using techniques inspired by natural evolution , such as inheritance , mutation , selection , and crossover . for the numerical fitting
usually is used a nonlinear least square method , this algorithm is based on calculus by starting from an initial set of variable values .
this approach is mathematically elegant compared to the exhaustive or random searches but tends easily to get stuck in local minima .
on the other hand , random methods use some probabilistic calculations to find variable sets .
they tend to be slower but have greater success at finding the global minimum regardless of the initial values of the variables .
And you have already written the first three sentences of the full article: the ferrites materials have been widely used as various electronic devices such as inductors , transformers , and electromagnetic wave absorbers in the relatively high - frequency region up to a few hundreds of mhz .
the electromagnetic theory can be used to describe the macroscopic properties of matter .
the electromagnetic fields may be characterized by four vectors : electric field * e * , magnetic flux density * b * , electric flux density * d * , and magnetic field * h * , which at ordinary points satisfy maxwell s equations.
Please generate the next two sentences of the article
|
. the ferrite media under study can be considerer as linear , homogeneous , and isotropic .
the relation between the vectors * b * and * h * can be expressed as : * b * = @xmath0*h * . where @xmath1 is the magnetic permeability of the material .
|
12,018 |
Suppose that you have an abstract for a scientific paper: the phenomenology of a qcd - pomeron model based on the exchange of a pair of non - perturbative gluons , _
i.e. _ gluon fields with a finite correlation length in the vacuum , is studied in comparison with the phenomenology of qcd chiral symmetry breaking , based on non - perturbative solutions of schwinger - dyson equations for the quark propagator including these non - perturbative gluon effects .
we show that these models are incompatible , and point out some possibles origins of this problem .
= 10000 epsf * compatibility of a model for the qcd - pomeron and chiral - symmetry breaking phenomenologies * + a. a. natale and p. s. rodrigues da silva + instituto de fsica terica , universidade estadual paulista + rua pamplona , 145 , 01405 - 900 , so paulo , sp - brazil .
And you have already written the first three sentences of the full article: the interpretation of the pomeron in the framework of qcd is not fully understood .
it is expected to be generated at least by two gluons exchange @xcite . however , the exchange of two perturbative gluons can not reproduce the experimental results on diffractive scattering . in order to circumvent such difficulty , landshoff and nachtmann
@xcite(ln ) proposed a model where the pomeron is described by the exchange of two non - perturbative gluons , whose properties are dictated by the expected structure of the qcd vacuum ..
Please generate the next two sentences of the article
|
these non - perturbative gluons should not propagate over long distances , i.e. there is a finite correlation length for the gluon field in the vacuum , which should be determined from first principles , and can be understood in terms of gluon condensates @xcite .
the ln model describes successfully the experimental results of diffractive phenomena using a quite simple ansatz for the non - perturbative gluon propagator @xcite .
|
12,019 |
Suppose that you have an abstract for a scientific paper: ceres is the largest and most massive body in the asteroid main belt .
observational data from the dawn spacecraft reveal the presence of at least two impact craters about 280 km in diameter on the ceres surface , that could have expelled a significant number of fragments . yet
, standard techniques for identifying dynamical asteroid families have not detected any ceres family . in this work
, we argue that linear secular resonances with ceres deplete the population of objects near ceres .
also , because of the high escape velocity from ceres , family members are expected to be very dispersed , with a considerable fraction of km - sized fragments that should be able to reach the pristine region of the main belt , the area between the 5j:-2a and 7j:-3a mean - motion resonances , where the observed number of asteroids is low . rather than looking for possible ceres family members near ceres ,
here we propose to search in the pristine region .
we identified 156 asteroids whose taxonomy , colors , albedo could be compatible with being fragments from ceres . remarkably , most of these objects have inclinations near that of ceres itself . [ firstpage ] minor planets , asteroids : general minor planets , asteroids : individual : ceres celestial mechanics . .
And you have already written the first three sentences of the full article: ceres is the largest and most massive body in the asteroid main belt .
while many other large bodies of similar composition such as pallas , hygiea , euphrosyne have asteroid families , no such group has been so far identified for ceres @xcite . yet
collisional models suggest that about 10 craters larger than 10 km in diameter should have formed over 4.55 gyr of collisional evolution in the main belt @xcite . also.
Please generate the next two sentences of the article
|
, observational data from the dawn probe show that at least two @xmath0280-km sized craters were formed in the last @xmath1 gyr on ceres surface , and larger impacts may have happened in the past @xcite .
the absence of a ceres family is therefore a major mystery in asteroid dynamics @xcite .
|
12,020 |
Suppose that you have an abstract for a scientific paper: we study the correspondence between two theoretical frameworks for describing dark energy , @xmath0 gravity and higher - dimensional space - time - matter ( stm ) or induced - matter theory .
we show that the hubble expansion parameter in @xmath0 gravity can be associated with a combination of metric functions in stm theory , and consider a specific example whose properties are consistent with late - time acceleration .
-2.5 cm .
And you have already written the first three sentences of the full article: the question of dark energy and the accelerating universe has been the focus of a large amount of activities in recent years . this expansion has directly been measured from the light - curves of several hundred type ia supernovae @xcite and independently from observations of the cosmic microwave background ( cmb ) by the wmap satellite @xcite and other cmb experiments @xcite .
all these results strongly suggest that the universe is permeated smoothly by dark energy which has a negative pressure and violates the strong energy condition .
dark energy and the accelerating universe have been discussed extensively from various point of views over the past few years @xcite . in principle , a natural candidate for dark energy could be a small cosmological constant ..
Please generate the next two sentences of the article
|
one approach in this direction is to employ what is known as modified gravity where an arbitrary function of the ricci scalar is added to the einstein - hilbert action .
it has been shown that such a modification may account for the late time acceleration and the initial inflationary period in the evolution of the universe @xcite .
|
12,021 |
Suppose that you have an abstract for a scientific paper: we calculate the cp violating effects in the top quark semi
leptonic three body decays induced by the supersymmetric cp odd phase of the top squark trilinear soft breaking term @xmath0 .
the light top squark mass is assumed to be close to the top quark mass @xmath1 .
the cp conserving phase is provided by the @xmath2 and @xmath3 cut .
we find that the partial rate asymmetry is in the 0.1% level . in the most favorable parameter region
the decay rate asymmetry can reach up to 0.55% . * cp violation in semi
leptonic decays of the top quark within mssm * xiao - jun bi and yuan - ben dai + .
And you have already written the first three sentences of the full article: top quark physics is sensitive to new physics , which may exist near the electro weak scale , due to its large mass .
experimental and theoretical research about cp violation in top sector is one way to reveal new physics . to study the top quark cp
odd effects has its own advantage that the uncertainties coming from hardron matrix elements can be avoided ..
Please generate the next two sentences of the article
|
if @xmath4 is near to @xmath5 , the cp assymmetry effects in top quark decays can be induced by new particles . until now
a lot of works about cp
|
12,022 |
Suppose that you have an abstract for a scientific paper: the hydrodynamic ( hydro ) model applied to heavy ion data from the relativistic heavy ion collider ( rhic ) in the form of single - particle spectra and correlations seems to indicate that a dense qcd medium nearly opaque to partons , a strongly - coupled quark - gluon plasma ( sqgp ) , is formed in more - central au - au collisions , and that the sqgp may have a very small viscosity ( `` perfect liquid '' ) .
measurements of radial and elliptic flows , with possible coalescence of `` constituent quarks '' to form hadrons , seem to support the conclusion . however , other measurements provide contradictory evidence .
unbiased angular correlations indicate that a large number of back - to - back jets from initial - state scattered partons with energies as low as 3 gev survive as `` minijet '' hadron correlations even in central au - au collisions , suggesting near transparency .
two - component analysis of single - particle hadron spectra reveals a corresponding spectrum hard component ( parton fragment distribution described by pqcd ) which can masquerade as `` radial flow '' in some spectrum analysis .
reinterpretation of `` elliptic flow '' as a qcd scattering process resulting in fragmentation is also possible . in this paper
i review analysis methods and results in the context of two paradigms : the conventional hydrodynamics / hard - probes paradigm and an alternative quadrupole / minijets paradigm .
based on re - interpretation of fiducial data i argue that hydrodynamics may not be relevant to rhic collisions .
collision evolution may be dominated by parton scattering and fragmentation , albeit the fragmentation process is strongly modified in more - central a - a collisions . .
And you have already written the first three sentences of the full article: the hydrodynamic ( hydro ) model has been applied extensively to heavy ion collisions at the super proton synchrotron ( sps ) and rhic as part of a search for formation of a quark - gluon plasma ( qgp ) @xcite .
hydro is intended to describe collision evolution in terms of flowing hot and dense matter , possibly a qgp @xcite .
validity of the hydro description could support inference of parton thermalization @xcite and direct comparisons with lattice qcd @xcite ..
Please generate the next two sentences of the article
|
the hydro model appears to be successful in representing some aspects of particle data .
hadron spectra have been described in terms of radial flow combined with the statistical model @xcite .
|
12,023 |
Suppose that you have an abstract for a scientific paper: the solution of the hyperangular schrdinger equation for few - body systems using a basis of explicitly correlated gaussians remains numerically challenging .
this is in part due to the number of basis functions needed as the system size grows , but also due to the fact that the number of numerical integrations increases with the number of hyperangular degrees of freedom .
this paper shows that the latter challenge is no more . using a delta function to fix the hyperradius @xmath0 ,
all matrix element calculations are reduced to a single numerical integration regardless of system size @xmath1 or number of dimensions @xmath2 . in the special case of @xmath2
an even number , the matrix elements of the noninteracting system are fully analytical .
we demonstrate the use of the new matrix elements for the 3- , 4- , and 5-body electron - positron systems with zero total angular momentum @xmath3 , positive parity @xmath4 , and varied spins @xmath5 and @xmath6 . .
And you have already written the first three sentences of the full article: aspects of few - body phenomena arise in many areas of physics . for example
, experiments using cold atomic gases can study few - body loss phenomena within a many - body background @xcite , directly trap small clusters in a single microtrap @xcite , see the transition to the mott insulating phase of an optical lattice @xcite , and ions can be held and studied for long periods of time @xcite .
another area includes the formation of exotic `` molecules '' from a combination of matter and antimatter ..
Please generate the next two sentences of the article
|
more specifically , polyelectronic clusters have been experimentally verified such as ps @xcite , ps@xmath7 @xcite , and ps@xmath8 @xcite . on the other hand
, a recent study suggests that tripositronium is not bound @xcite . since wheeler s prediction of dipositronium ps@xmath8 in 1946 @xcite
|
12,024 |
Suppose that you have an abstract for a scientific paper: we perform a detailed analysis of high - order harmonic generation in diatomic molecules within the strong - field approximation , with emphasis on quantum - interference effects .
specifically , we investigate how the different types of electron orbits , involving one or two centers , affect the interference patterns in the spectra .
we also briefly address the influence of the choice of gauge , and of the initial and final electronic bound states on such patterns .
for the length - gauge sfa and undressed bound states , there exist additional terms , which can be interpreted as potential energy shifts .
if , on the one hand , such shifts alter the potential barriers through which the electron initially tunnels , and may lead to a questionable physical interpretation of the features encountered , on the other hand they seem to be necessary in order to reproduce the overall maxima and minima in the spectra .
indeed , for dressed electronic bound states in the length gauge , or undressed bound states in the velocity gauge , for which such shifts are absent , there is a breakdown of the interference patterns . in order to avoid such a problem
, we provide an alternative pathway for the electron to reach the continuum , by means of an additional attosecond - pulse train .
a comparison of the purely monochromatic case with the situation for which the attosecond pulses are present suggests that the patterns are due to the interference between the electron orbits which finish at different centers , regardless of whether one or two centers are involved . .
And you have already written the first three sentences of the full article: in the past few years , high - order harmonic generation ( hhg ) and above - threshold ionization ( ati ) from aligned molecules in strong laser fields of femtosecond duration have proven to be a powerful tool for resolving , or even controlling , processes in the subfemtosecond and subangstrom scale .
for instance , one may employ hhg and ati in the tomographic reconstruction of molecular orbitals @xcite , and in the attosecond probing of dynamic changes in molecules @xcite .
this is possible due to the fact that the physical mechanisms governing both phenomena take place in a fraction of the laser period , i.e. , within hundreds of attoseconds @xcite , and involve the recombination or the elastic scattering of an electron with its parent molecule @xcite ..
Please generate the next two sentences of the article
|
thereby , high - order harmonics or high - energy photoelectrons , respectively , are generated .
thus , the spectral features are highly dependent on the spatial configuration of the ions with which the electron rescatters or recombines , and yield patterns which are characteristic of the molecule
|
12,025 |
Suppose that you have an abstract for a scientific paper: qcd phase diagram is obtained by analysing centrality dependence of @xmath0 suppression in @xmath1=17.3 pb+pb and @xmath1=200 gev au+au collisions .
s produced in initial interactions are assumed to dissolve if local temperature exceeds a threshold temperature .
the threshold temperature depends on the ( local ) fluid temperature and baryonic chemical potential , which are obtained , under certain assumptions , from experimentally determined quantities e.g. rapidity density , net baryon density .
qcd critical line with curvature parameter @xmath2 is consistent with experimental @xmath0 data .
@xmath3 is factor of @xmath43 larger than in lattice qcd calculations . .
And you have already written the first three sentences of the full article: in recent years , there is much interest in qgp phase diagram in @xmath5 plane , @xmath6 the temperature and @xmath7 the baryonic chemical potential @xcite,@xcite,@xcite,@xcite .
presently , only one point in the phase diagram is known from lattice qcd simulations , at @xmath80 , the qcd transition is a cross over @xcite at ( pseudo ) critical temperature @xmath9157 ( 3)(3 ) mev @xcite . from theoretical considerations ,
qcd phase transition is expected to be 1st order in baryon dense matter ..
Please generate the next two sentences of the article
|
one then expects a qcd critical end point ( cep ) , where the transition changes from 1st order to cross - over . to access the qcd phase diagram and cep ,
systematic study of nuclear collisions , as a function of collision energy , has been planned at fair @xcite in the energy range @xmath10=5 - 40 gev . at finite baryon density , fermion determinant is complex and standard technique of monte - carlo importance sampling fails .
|
12,026 |
Suppose that you have an abstract for a scientific paper: in a two - dimensional parabolic quantum dot charged with @xmath0 electrons , thomas - fermi theory states that the ground - state energy satisfies the following non - trivial relation : @xmath1 , where the coupling constant , @xmath2 , is the ratio between coulomb and oscillator ( @xmath3 ) characteristic energies , and @xmath4 is a universal function .
we perform extensive configuration interaction calculations in order to verify that the exact energies of relatively large quantum dots approximately satisfy the above relation .
in addition , we show that the number of energy levels for intraband and interband ( excitonic and biexcitonic ) excitations of the dot follows a simple exponential dependence on the excitation energy , whose exponent , @xmath5 , satisfies also an approximate scaling relation _ a la _ thomas - fermi , @xmath6 .
we provide an analytic expression for @xmath4 , based on two - point pad approximants , and two - parameter fits for the @xmath7 functions . .
And you have already written the first three sentences of the full article: thomas - fermi theory @xcite has proven to be a valuable tool for the qualitative understanding of atoms and molecules . in semiconductor quantum dots @xcite , which are a kind of artificial thomson atoms with many possibilities for fundamental research and technical applications
, thomas - fermi theory was shown to agree qualitatively and even quantitatively with a more ellaborated approach like density functional theory @xcite , being asymptotically exact in the limit of large electron numbers @xcite . from the computational point of view ,
thomas - fermi theory with minor corrections is able to reproduce the ground - state energy of electrons in a quadratic potential @xcite at the same level of accuracy of other semiclassical or semianalytic approaches like large-@xmath8 expansions @xcite or two - point pad approximants @xcite . in the present paper.
Please generate the next two sentences of the article
|
, we would like to stress on a less studied aspect of thomas - fermi theory : the highly non - trivial scaling relations following from it .
we show that the number of electrons , @xmath0 , and the coupling constant , @xmath2 , enter the ground - state energy in a scaled form .
|
12,027 |
Suppose that you have an abstract for a scientific paper: we explore the connection between the central supermassive blackholes ( smbh ) in galaxies and the dark matter halo through the relation between the masses of the smbhs and the maximum circular velocities of the host galaxies , as well as the relationship between stellar velocity dispersion of the spheroidal component and the circular velocity .
our assumption here is that the circular velocity is a proxy for the mass of the dark matter halo .
we rely on a heterogeneous sample containing galaxies of all types .
the only requirement is that the galaxy has a direct measurement of the mass of its smbh and a direct measurement of its circular velocity and its velocity dispersion .
previous studies have analyzed the connection between the smbh and dark matter halo through the relationship between the circular velocity and the bulge velocity dispersion , with the assumption that the bulge velocity dispersion stands in for the mass of the smbh , via the well - established smbh mass - bulge velocity dispersion relation . using intermediate relations may be misleading when one is studying them to decipher the active ingredients of galaxy formation and evolution .
we believe that our approach will provide a more direct probe of the smbh and the dark matter halo connection .
we find that the correlation between the mass of supermassive blackholes and the circular velocities of the host galaxies is extremely weak , leading us to state the dark matter halo may not play a major role in regulating the blackhole growth in the present universe . .
And you have already written the first three sentences of the full article: data has been accumulating over the last several years on an increasing number of galaxies in terms of measurements of the bulge velocity dispersion @xmath0 , mass of the central supermassive blackhole ( smbh ) @xmath1 , and the circular velocity , @xmath2 , of the host galaxy ( mcconnell & ma 2013 ; hu 2009 ; graham 2008 ; hu 2008 ; ho 2007 ; courteau et al .
2007 ; pizella et al . 2005 ; baes et al . 2003
; ferrarese 2002 ; tremaine et al ..
Please generate the next two sentences of the article
|
2002 ; onken et al 2004 ; peterson et al . 2004 ; nelson et al . 2004 ; merrit and ferrarese 2001 ; bedregal et al .
2006 ; bernardi et al . 2002 ; kronawitter et al .
|
12,028 |
Suppose that you have an abstract for a scientific paper: we have begun a survey of the structure of the milky way halo , as well as the halos of other local group galaxies , as traced by their constituent giant stars .
these giant stars are identified via large area , ccd photometric campaigns . here
we present the basis for our photometric search method , which relies on the gravity sensitivity of the mg i triplet + mgh features near 5150 in f - k stars , and which is sensed by the flux in the intermediate band @xmath0 filter .
our technique is a simplified variant of the combined washington / ddo51 four filter technique described by geisler [ 1984 , pasp , 96 , 723 ] , which we modify for the specific purpose of efficiently identifying distant giant stars for follow - up spectroscopic study : we show here that for most stars the washington @xmath1 color is correlated monotonically with the washington @xmath2 color with relatively low scatter ; for the purposes of our survey , this correlation obviates the need to image in the @xmath3 filter , as originally proposed by geisler . to calibrate our ( @xmath2 , @xmath4 ) diagram as a means to discriminate field giant stars from nearby dwarfs , we utilize new photometry of the main sequences of the open clusters ngc 3680 and ngc 2477 and the red giant branches of the clusters ngc 3680 , melotte 66 and @xmath5 centauri , supplemented with data on field stars , globular clusters and open clusters by doug geisler and collaborators . by combining the data on stars from different clusters , and by taking advantage of the wide abundance spread within @xmath5 centauri
, we verify the primary dependence of the @xmath4 color on luminosity , and demonstrate the secondary sensitivity to metallicity among giant stars .
our empirical results are found to be generally consistent with those from analysis of synthetic spectra by paltoglou & bell [ 1994 , mnras , 268 , 793 ] .
finally , we provide conversion formulae from the ( @xmath6 , @xmath2 ) system to the ( @xmath7 , @xmath8 ) system , corresponding reddening....
And you have already written the first three sentences of the full article: understanding the nature of the milky way halo
its shape , extent , density distribution , kinematics , abundance distribution and origin has long been a central topic in astronomy .
the importance of this endeavor has increased substantially with the growing , pervasive connections to a number of other astronomical enterprises bearing on such wide ranging astrophysical problems as , for example , the magnitude and distribution of dark matter and the frequency of microlensing events , the origin of the second parameter problem of horizontal branch morphology in globular clusters , the nature of high velocity hi clouds , the interaction of galaxies with their environment , and , of course , the origin and evolution of the milky way . in spite of the pressing need for a detailed picture of the halo , at present we still have only the most rudimentary prescriptions of , for example , the phase space distribution of halo stars ..
Please generate the next two sentences of the article
|
unfortunately , for many applications we no longer can be satisfied with elementary analytical models of the halo . indeed , the very suitability of such simple descriptions may now be questioned .
a number of new lines of evidence indicate that the halo of the milky way has not achieved a dynamically relaxed state .
|
12,029 |
Suppose that you have an abstract for a scientific paper: during polymer translocation driven by e.g. voltage drop across a nanopore , the segments in the cis - side is incessantly pulled into the pore , which are then pushed out of it into the trans - side .
this pulling and pushing polymer segments are described in the continuum level by nonlinear transport processes known , respectively , as fast and slow diffusions . by matching solutions of both sides through the mass conservation across the pore
, we provide a physical basis for the cis and trans dynamical asymmetry , a feature repeatedly reported in recent numerical simulations .
we then predict how the total driving force is dynamically allocated between cis ( pulling ) and trans ( pushing ) sides , demonstrating that the trans - side event adds a finite - chain length effect to the dynamical scaling , which may become substantial for weak force and/or high pore friction cases .
# 1 the dynamics of translocation , i.e. , the polymer passage through a narrow pore , has been actively studied more than a decade @xcite .
in addition to its relevance to cellular biological processes , i.e. , biopolymer transports in cells , the phenomenon has found promising applications in genome sequencing and related technology as a nanopore sensor @xcite . being a unique mode of the molecular transport inherent in long flexible polymers ,
there have been numerous attempts to characterize the process and to uncover the underlying physics behind it @xcite .
such efforts have led to the consensus that the _ tension _ is a key physical quantity , which is created in the polymer by the spontaneous segment motions and/or the action of the driving force @xcite .
now we have a fairly good description of the translocation process , which may be categorized according to the magnitude @xmath0 of the bias as follows .
( i ) unbiased regime : the tension imbalance across the pore arising from the segment exchange between cis and trans sides creates a long term power - law decaying memory @xcite .
this....
And you have already written the first three sentences of the full article: this work was supported by the jsps core - to - core program
non - equilibrium dynamics of soft matter and information " and jsps kakenhi grant number 24340100 ..
Please generate the next two sentences of the article
| |
12,030 |
Suppose that you have an abstract for a scientific paper: the standing quasi modes in a cylindrical incompressible flux tube with magnetic twist that undergoes a radial density structuring is considered in ideal magnetohydrodynamics ( mhd ) .
the radial structuring is assumed to be a linearly varying density profile . using the relevant connection formulae , the dispersion relation for the mhd waves
is derived and solved numerically to obtain both the frequencies and damping rates of the fundamental and first - overtone modes of both the kink ( @xmath0 ) and fluting ( @xmath1 ) waves .
it was found that a magnetic twist will increase the frequencies , damping rates and the ratio of the oscillation frequency to the damping rate of these modes .
the period ratio @xmath2 of the fundamental and its first - overtone surface waves for kink ( @xmath0 ) and fluting ( @xmath1 ) modes is lower than 2 ( the value for an untwisted loop ) in the presence of twisted magnetic field . for the kink modes , particularly , the magnetic twists @xmath30.0065 and 0.0255 can achieve deviations from 2 of the same order of magnitude as in the observations . furthermore , for the fundamental kink body waves , the frequency bandwidth increases with increasing the magnetic twist .
= 16truecm = 23truecm = -1.3truecm = -2truecm = 1.20 cm = 1.60 cm * keywords : * sun : corona sun : magnetic fields sun : oscillations .
And you have already written the first three sentences of the full article: transverse oscillations of coronal loops were first identified by aschwanden et al .
( 1999 ) and nakariakov et al .
( 1999 ) using the observations of transition region and coronal explorer ( trace ) ..
Please generate the next two sentences of the article
|
nakariakov et al .
( 1999 ) reported the detection of spatial oscillations in five coronal loops with periods ranging from 258 to 320 s. the decay time was @xmath4 min for an oscillation of @xmath5 mhz .
|
12,031 |
Suppose that you have an abstract for a scientific paper: primary goal of the witch experiment is to test the standard model for a possible admixture of a scalar or tensor type interaction in @xmath0-decay .
this information will be inferred from the shape of the recoil energy spectrum .
the experimental set - up was completed and is under intensive commissioning at isolde ( cern ) .
it combines a penning trap to store the ions and a retardation spectrometer to probe the recoil ion energy . a brief overview of the witch set - up and the results of commissioning tests performed until now are presented .
finally , perspectives of the physics program are reviewed . .
And you have already written the first three sentences of the full article: the most general interaction hamiltonian for nuclear @xmath0-decay which includes all possible interaction types consistent with lorentz - invariance @xcite contains 5 different terms , so - called scalar ( s ) , vector ( v ) , tensor ( t ) , axial - vector ( a ) and pseudoscalar ( p ) contributions .
the standard model ( sm ) of the weak interaction excepts only v and a interactions which leads to the well - known @xmath1 structure of the weak interaction .
however , the presence of scalar and tensor types of weak interaction is today ruled out only to the level of about 8% of the v- and a - interactions @xcite ..
Please generate the next two sentences of the article
|
a possible admixture of a scalar or tensor type weak interaction in @xmath0-decay can be studied by determining the @xmath2 angular correlation .
this correlation for unpolarized nuclei can be characterized by the @xmath2 angular correlation coefficient _ a _
|
12,032 |
Suppose that you have an abstract for a scientific paper: we study fermions in two dimensions interacting via a long - ranged @xmath0 potential for small particle separations and a short - ranged @xmath1 potential for larger separations in comparison to a length scale @xmath2 .
we compute the energy of the wigner crystal and of the homogeneous fermi liquid phases using a variational approach , and determined the phase diagram as a function of density and @xmath2 at zero temperature .
we discuss the collective modes in the fermi liquid phase , finite temperature effects on the phase diagram , and possible experimental realizations of this model . .
And you have already written the first three sentences of the full article: inhomogeneity plays an important role in many highly correlated materials@xcite . for example
stripe phases which break translational symmetry of real space in one direction have been observed in high temperature superconductors@xcite .
similarly , a wigner crystal ( wc ) phase@xcite which has only discrete translational symmetry of triangular lattices and six - fold rotational symmetry has been observed in electrons on the surface of liquid helium@xcite and in ultra - clean two - dimensional hole gases@xcite . for interactions which decay as the power law @xmath3.
Please generate the next two sentences of the article
|
, a classical argument shows that the potential energy scales with density as @xmath4 in two dimensions ( 2d ) and the kinetic energy as @xmath5 .
the ratio of the potential to the kinetic energy scales as @xmath6 which becomes @xmath7 , for coulomb interactions , a constant for @xmath8 and @xmath9 for @xmath1 potentials .
|
12,033 |
Suppose that you have an abstract for a scientific paper: we study cp - violating effects in neutralino production and subsequent decay within the minimal supersymmetric standard model with complex parameters @xmath0 and @xmath1 . the observable we propose is a t - odd asymmetry based on a triple product in neutralino production @xmath2 , @xmath3 , with subsequent leptonic three - body decay @xmath4 , @xmath5 , at an @xmath6 linear collider with @xmath7 gev and polarised beams .
we provide compact analytical formulae for the cross section and the t - odd asymmetry taking into account the complete spin correlations between production and decay .
we give numerical predictions for the cross section and the t - odd asymmetry .
the asymmetry can go up to 10% .
dcpt-04 - 30 + ippp-04 - 15 + uwthph-2004 - 11 + wue - itp-2004 - 012 + hep - ph/0406190 + a. bartl@xmath8 , h. fraas@xmath9 , s. hesselbach@xmath8 , k. hohenwarter - sodek@xmath8 , g. moortgat - pick@xmath10 @xmath8_institut fr theoretische physik , universitt wien , a-1090 vienna , austria _
+ @xmath9_institut fr theoretische physik und astrophysik , universitt wrzburg , _ + _ am hubland , d-97074 wrzburg , germany _ + @xmath10_ippp , university of durham , durham dh1 3le , u.k . _ .
And you have already written the first three sentences of the full article: in the standard model ( sm ) the phase in the cabibbo - kobayashi - maskawa ( ckm ) matrix is the only source of cp violation . the small amount of cp violation in the sm , however , is not sufficient to explain the baryon - antibaryon asymmetry of the universe @xcite .
the lagrangian of the minimal supersymmetric standard model ( mssm ) contains several complex parameters , which can give rise to new cp - violating phenomena @xcite . in the neutralino sector of the mssm two complex parameters
appear , which lead to cp - violating effects in neutralino production and decay ..
Please generate the next two sentences of the article
|
these parameters are the @xmath11 gaugino mass parameter @xmath0 and the higgsino mass parameter @xmath1 .
the phase of the @xmath12 gaugino mass parameter @xmath13 can be eliminated by an @xmath11-symmetry of the model .
|
12,034 |
Suppose that you have an abstract for a scientific paper: motivated by a careful analysis of the laplacian on the supergroup @xmath0 we formulate a proposal for the state space of the @xmath0 wznw model .
we then use properties of @xmath1 characters to compute the partition function of the theory . in the special case of level @xmath2 the latter
is found to agree with the properly regularized partition function for the continuum limit of the integrable @xmath3 super - spin chain .
some general conclusions applicable to other wznw models ( in particular the case @xmath4 ) are also drawn . .
And you have already written the first three sentences of the full article: the @xmath0 wznw model is a key example of the sigma models with supergroup targets that appear in the supersymmetric description of non interacting disordered systems in low dimensional statistical mechanics .
the first occurrence of this model probably arose via a supersymmetrization of the path integral for two copies of the two dimensional critical ising model .
it was shown in @xcite how a @xmath5 system ( with central charge @xmath6 ) could be introduced to cancel out the pair of free majorana fermions ( regrouped for convenience into a dirac fermion ) path integrals @xmath7\ , \exp[s_{0}+\delta s]\ =.
Please generate the next two sentences of the article
|
\ 1 \label{ising}\ ] ] where @xmath8 and @xmath9 the theory without random mass @xmath10 is obviously a free osp(2@xmath112 ) theory , which can be considered as a @xmath0 wznw model at level @xmath4 .. in part of the literature , the level is defined as @xmath12 , so the free system in ( [ ising ] ) has @xmath2 there . ]
averaging over disorder produces a marginally irrelevant current current perturbation of this wznw model .
|
12,035 |
Suppose that you have an abstract for a scientific paper: we present an approach to the calculation of arbitrary spectral , thermal and excited state properties within the full configuration interaction quantum monte carlo framework .
this is achieved via an unbiased projection of the hamiltonian eigenvalue problem into a space of stochastically sampled krylov vectors , thus enabling the calculation of real - frequency spectral and thermal properties and avoiding explicit analytic continuation .
we use this approach to calculate temperature - dependent properties and one- and two - body spectral functions for various hubbard models , as well as isolated excited states in _ ab initio _ systems .
quantum monte carlo ( qmc ) in its various guises , is undoubtedly one of the most important approaches for accurate elucidation of properties for correlated systems@xcite .
however , these successes have focused primarily on the ground state energy and observables which commute with the hamiltonian .
critical importance for a deeper understanding of correlated systems comes from _ dynamic _ correlation functions and spectral quantities .
these mirror how we perceive our environment , namely by perturbing a system and measuring its response the basis of nearly all spectroscopic and experimental approaches .
this gives us direct insight into optical , magnetic and other beyond - ground - state properties , and allow for direct comparison to experimental results .
direct access to dynamic properties is a persistent difficulty for qmc approaches in general . while in the absence of a sign problem
, unbiased imaginary - time spectra can be obtained@xcite , the analytic continuation to physical , real - frequency functions is notoriously ill - conditioned and can lead to artefacts and smoothing of features.@xcite for more general fermionic systems , higher temperatures must be simulated to alleviate the sign problem@xcite , while nodal constraints bias towards a particular solution and are difficult to extend to spectra@xcite .
alternatively ,....
And you have already written the first three sentences of the full article: g.h.b gratefully acknowledges funding from the royal society . n.s.b acknowledges trinity college , cambridge for funding
this work has been supported by the epsrc under grant no .
ep / j003867/1 ..
Please generate the next two sentences of the article
|
39ifxundefined [ 1 ] ifx#1 ifnum [ 1 ] # 1firstoftwo secondoftwo ifx [ 1 ] # 1firstoftwo secondoftwo `` `` # 1''''@noop [ 0]secondoftwosanitize@url [ 0 ]
+ 12$12 & 12#1212_12%12@startlink[1]@endlink[0]@bib@innerbibempty @noop * * , ( ) @noop * * , ( ) @noop * * , ( ) @noop * * , ( ) @noop * * , ( ) @noop * * , ( ) @noop * * , ( ) @noop * * , ( ) @noop * * , ( ) @noop * * , ( ) @noop * * , ( ) @noop * * , ( ) @noop * * , ( ) @noop * * , ( ) @noop * * , ( ) @noop * * , ( ) @noop * * , ( ) @noop _ _ ( , ) pp . @noop
|
12,036 |
Suppose that you have an abstract for a scientific paper: in this article , we study the _ time - dependent _ aharonov - bohm effect for non - abelian gauge fields .
we use two well known time - dependent solutions to the yang - mills field equations to investigate the aharonov - bohm phase shift . for both of the solutions
, we find a cancellation between the phase shift coming from the non - abelian `` magnetic '' field and the phase shift coming from the non - abelian `` electric '' field , which inevitably arises in time - dependent cases .
we compare and contrast this cancellation for the time - dependent non - abelian case to a similar cancellation which occurs in the time - dependent abelian case .
we postulate that this cancellation occurs generally in time - dependent situations for both abelian and non - abelian fields . .
And you have already written the first three sentences of the full article: the aharonov - bohm effect @xcite is usually investigated in terms of abelian gauge theories , _ e.g. _ electromagnetism formulated via maxwell s equations .
further , the electromagnetic fields considered in the canonical aharonov - bohm effect are static fields . for the vector / magnetic aharonov - bohm effect
, this means a static vector potential , @xmath0 , which then translates to a static magnetic field via @xmath1 . in this article , we wish to consider the aharonov - bohm effect in the presence of _ time - dependent , non - abelian _ gauge fields ..
Please generate the next two sentences of the article
|
there has been some prior work on the aharonov - bohm effect in the presence of time - independent , non - abelian fields @xcite . unlike the abelian case of electromagnetism
, it may not be possible to observe the aharonov - bohm effect for static , non - abelian fields .
|
12,037 |
Suppose that you have an abstract for a scientific paper: we consider the termination / non - termination property of a class of loops .
such loops are commonly used abstractions of real program pieces .
second - order logic is a convenient language to express non - termination .
of course , such property is generally undecidable . however , by restricting the language to known decidable cases , we exhibit new classes of loops , the non - termination of which is decidable .
we present a bunch of examples .
termination , non - termination , monadic second - order logic . .
And you have already written the first three sentences of the full article: in this paper , we recall that second - order logic is a convenient language to express non - termination of while loops , modeled as rules . such rules
are commonly used abstractions of real program pieces , see , e.g. , @xcite for the java programming language .
our main contribution is the definition of two new classes of rules , the termination of which is decidable , by restricting the language to known decidable cases , namely s1s and s2s ..
Please generate the next two sentences of the article
|
we also show and illustrate how decision procedures for their weak versions ws1s and ws2s can help proving termination / non - termination .
we organize the paper as follows .
|
12,038 |
Suppose that you have an abstract for a scientific paper: over the past two decades , fair resource allocation problems have received considerable attention in a variety of application areas . however , _ little progress has been made in the design of distributed algorithms with convergence guarantees for general and commonly used @xmath0-fair allocations_. in this paper , we study weighted @xmath0-fair packing problems , that is , the problems of maximizing the objective functions ( i ) @xmath1 when @xmath2 , @xmath3 and ( ii ) @xmath4 when @xmath5 , over linear constraints @xmath6 , @xmath7 , where @xmath8 are positive weights and @xmath9 and @xmath10 are non - negative .
we consider the distributed computation model that was used for packing linear programs and network utility maximization problems . under this model ,
_ we provide a distributed algorithm for general @xmath0 _ that converges to an @xmath11approximate solution in time ( number of distributed iterations ) that has an inverse polynomial dependence on the approximation parameter @xmath12 and poly - logarithmic dependence on the problem size .
_ this is the first distributed algorithm for weighted @xmath13fair packing with poly - logarithmic convergence in the input size . _
the algorithm uses simple local update rules and is stateless ( namely , it allows asynchronous updates , is self - stabilizing , and allows incremental and local adjustments ) .
we also obtain a number of structural results that characterize @xmath13fair allocations as the value of @xmath0 is varied .
these results deepen our understanding of fairness guarantees in @xmath13fair packing allocations , and also provide insight into the behavior of @xmath13fair allocations in the asymptotic cases @xmath14 , @xmath15 , and @xmath16 . .
And you have already written the first three sentences of the full article: over the past two decades , _ fair resource allocation _ problems have received considerable attention in many application areas , including internet congestion control @xcite , rate control in software defined networks @xcite , scheduling in wireless networks @xcite , multi - resource allocation and scheduling in datacenters @xcite , and a variety of applications in operations research , economics , and game theory @xcite . in
most of these applications , positive linear ( packing ) constraints arise as a natural model of the allowable allocations . in this paper
, we focus on the problem of finding an _ @xmath0-fair _ vector on the set determined by packing constraints @xmath17 where all @xmath18 . is commonly assumed to be a 0 - 1 matrix @xcite , important applications ( such as , e.g. , multi - resource allocation in datacenters ) are modeled by a more general constraint matrix @xmath9 with arbitrary non - negative elements @xcite . ] we refer to this problem as @xmath13fair packing . for a vector of positive weights @xmath19 and @xmath20 , an allocation vector @xmath21 of size @xmath22 is weighted @xmath0-fair , if for any alternative feasible vector @xmath23 : @xmath24 @xcite . for a compact and convex feasible region.
Please generate the next two sentences of the article
|
, @xmath21 can be equivalently defined as a vector that solves the problem of maximizing @xmath25 @xcite , where : @xmath26 @xmath0-fairness provides a trade - off between efficiency ( sum of allocated resources ) and fairness ( minimum allocated resource ) as a function of @xmath0 : the higher the @xmath0 , the better the fairness guarantees and the lower the efficiency @xcite .
important special cases are proportional fairness ( @xmath5 ) and max - min fairness ( @xmath16 ) . when @xmath27 , we have the unfair " case of linear optimization
|
12,039 |
Suppose that you have an abstract for a scientific paper: in the article we present a hardware meteor detector . the detection principle is based on the electromagnetic wave reflection from the ionized meteor trail in the atmosphere .
the detector uses the anadigm field programmable analogue array ( fpaa ) , which is an attractive alternative for a typically used detecting equipment - a pc computer with dedicated software .
we implement an analog signal path using most of available fpaa resources to obtain precise audio signal detection .
our new detector was verified in collaboration with the polish fireball network - the organization which monitors meteor activity in poland . when compared with currently used signal processing pc software employing real radio meteor scatter signals ,
our low - cost detector proved to be more precise and reliable . due to its cost and efficiency superiority over the current solution
, the presented module is going to be implemented in the planned distributed detectors system . .
And you have already written the first three sentences of the full article: one of the methods used for meteor detection is the radio meteor observation @xcite .
the principle is based on the electromagnetic waves reflection from the meteor s trail in the atmosphere , which is called the meteor scattering .
when a meteor enters the atmosphere , it ionizes the electrons in atmospheric e - layer ( 90 - 150 km , ionosphere layer ) and leaves a plasma trail which , for a short time , works like a mirror for radio waves ..
Please generate the next two sentences of the article
|
although the effect of the scattering is the strongest for 20 - 50 mhz frequencies , it is possible to receive reflected signals from distant media radio stations operating in higher frequency range ( 90mhz and above ) .
this makes the phenomenon observable even by amateurs with a relatively low - cost equipment .
|
12,040 |
Suppose that you have an abstract for a scientific paper: we analyze closed one - dimensional chains of weakly coupled many level systems , by means of the so - called hilbert space average method ( ham ) .
subject to some concrete conditions on the hamiltonian of the system , our theory predicts energy diffusion with respect to a coarse - grained description for almost all initial states .
close to the respective equilibrium we investigate this behavior in terms of heat transport and derive the heat conduction coefficient .
thus , we are able to show that both heat ( energy ) diffusive behavior as well as fourier s law follows from and is compatible with a reversible schrdinger dynamics on the complete level of description . .
And you have already written the first three sentences of the full article: as a central problem of non - equilibrium thermodynamics , heat conduction has been of vital interest since the beginning of the 19th century . during his extensive investigations on heat transport in solids
fourier discovered around 1807 @xcite a proportionality between the temperature gradient @xmath0 and the heat respectively energy current density in the material , @xmath1 where @xmath2 is some material constant the heat conductivity .
concentrating on one - dimensional chains of interacting subsystems the temperature gradient can be discretized as @xmath3 , where @xmath4 is the temperature difference between two adjacent subsystems and @xmath5 their distance . introducing the current @xmath6 through some area @xmath7 , fourier s law ( [ eq:1 ] ).
Please generate the next two sentences of the article
|
can be rewritten as @xmath8 with @xmath9 .
instead of approaching a global equilibrium state with some temperature @xmath10 , a solid , under some external perturbation by a temperature gradient ( introduced by heat baths with different temperatures ) , enters a local equilibrium state only : the temperature may vary from one macroscopically small but microscopically large part of the system to the other . the heat transport itself
|
12,041 |
Suppose that you have an abstract for a scientific paper: we use _ ab initio _ molecular dynamics simulations to study a sample of liquid silica containing 3.84 wt.@xmath0 h@xmath1o .
we find that , for temperatures of 3000 k and 3500 k , water is almost exclusively dissolved as hydroxyl groups , the silica network is partially broken and static and dynamical properties of the silica network change considerably upon the addition of water .
water molecules or free o - h groups occur only at the highest temperature but are not stable and disintegrate rapidly .
structural properties of this system are compared to those of pure silica and sodium tetrasilicate melts at equivalent temperatures .
these comparisons confirm the picture of a partially broken tetrahedral network in the hydrous liquid and suggest that the structure of the matrix is as much changed by the addition of water than it is by the addition of the same amount ( in mole % ) of sodium oxide . on larger length scales , correlations are qualitatively similar but seem to be more pronounced in the hydrous silica liquid . finally , we study the diffusion mechanisms of the hydrogen atoms in the melt .
it turns out that hosi@xmath1 triclusters and sio dangling bonds play a decisive role as intermediate states for the hydrogen diffusion . .
And you have already written the first three sentences of the full article: over the last decades , amorphous silicates containing several wt.@xmath0 of water have attracted the interest of many experimental and theoretical research groups due to its importance in science and technology . e.g. these systems are supposed to play an important role in magmatic flow in the earth crust and have therefore been investigated extensively by many geologists ( for reviews see @xcite ) . in silicate melts ( lava ) , water can be released if temperature and pressure conditions are altered and in that case , the released water molecules assemble in bubbles .
these bubbles can set up pressure for explosive volcanism @xcite .
the microscopic origin of such bubbles is still very poorly understood @xcite and one of the main motivating aspects for our study is to find indicators for such bubble formation . the possible use of water containing silica in fuel cells @xcite and the use of water as defect passivant in semiconductor devices ( and reladed problems ) @xcite and its disturbing presence in optic fibers @xcite underline the technological importance ..
Please generate the next two sentences of the article
|
+ over the past years pure amorphous silica has been well understood regarding its electronic and structural properties and experimental and simulational data seem to agree well @xcite . in recent studies these investigations
have been extended to the technologically highly important class of sodium silicates @xcite .
|
12,042 |
Suppose that you have an abstract for a scientific paper: by combining the results of sno and super - kamiokande one can derive - in the absence of sterile neutrinos - the total neutrino flux produced from @xmath0b decay in the sun .
we use this information to check the accuracy of several input parameters of solar model calculations .
opacity and p - p fusion cross section are constrained by the @xmath0b flux measurement to the level of few per cent .
the central solar temperature is determined to the one - percent level .
we also find an upper limit for the flux on earth of sterile neutrinos .
we discuss the role of nuclear physics uncertainties on these determinations . .
And you have already written the first three sentences of the full article: electron neutrinos from @xmath0b decay in the sun have been detected at the sudbury neutrino observatory ( sno ) by means of the charged current ( cc ) reaction on deuterium @xcite .
the result , @xmath1 10@xmath2 @xmath3 s@xmath4 ( here and in the following one sigma statistical errors are combined in quadrature with systematical errors ) , is a factor three smaller than the ssm prediction of bahcall et al.@xcite : @xmath5 the cc reaction is sensitive exclusively to @xmath6 , while electron scattering ( es ) also has a small sensitivity to @xmath7 and @xmath8 .
comparison of @xmath9 to the super - kamiokande ( sk ) precision result on es yields a 3.3@xmath10 difference , providing evidence that there is a non - electron flavor active neutrino component in the solar flux ..
Please generate the next two sentences of the article
|
extraction of this flux , @xmath11 , can be done in a model independent way by exploiting the similarities of the response functions of sno and of sk , see @xcite . in this way
, one determines from the two experiments the total active neutrino flux , @xmath12 , produced by @xmath0b decay in the sun @xcite : @xmath13 the close agreement with the theoretical prediction ( [ fibssm ] ) is an important confirmation of the robustness of ssm calculations , see table [ tabtc ] .
|
12,043 |
Suppose that you have an abstract for a scientific paper: a programmable quantum networks model is used in this paper for development of methods of control of a quantum state transport .
these methods may be applied for a wide variety of patterns of controlled state transmission and spreading in quantum systems .
the programmable perfect state transfer and quantum walk , mobile quantum ( ro)bots and lattice gas automata may be described by unified way with such approach . ] .
And you have already written the first three sentences of the full article: different kinds of the non - optical quantum state transport using specific phenomena in `` quantum wires '' are investigated very actively during recent few years .
some references may be found in sec .
[ sec : transf ] and sec ..
Please generate the next two sentences of the article
|
[ sec : walk ] . in the present work
is discussed a compact theoretical approach to the programmable quantum state transfer .
|
12,044 |
Suppose that you have an abstract for a scientific paper: in this paper we highlight the advantages of using point - contact spectroscopy ( pcs ) in multigap superconductors like mgb@xmath0 , both as a fundamental research tool and as a non - destructive diagnostic technique for the optimization of thin - film characteristics .
we first present some results of crucial fundamental interest obtained by directional pcs in mgb@xmath0 single crystals , for example the temperature dependence of the gaps and of the critical fields and the effect of a magnetic field on the gap amplitudes .
then , we show how pcs can provide useful information about the surface properties of mgb@xmath0 thin films ( e.g. @xmath1 , gap amplitude(s ) , clean or dirty - limit conditions ) in view of their optimization for the fabrication of tunnel and josephson junctions for applications in superconducting electronics . .
And you have already written the first three sentences of the full article: from the point of view of fundamental physics , magnesium diboride ( mgb@xmath0 , discovered to be superconducting below 39 k in 2001 @xcite ) is particularly interesting because it is the clearest example of two - band superconductor ever studied @xcite .
however , this simple compound is also interesting because of its possible applications , that could take advantage of its rather low production cost and of its rather high @xmath1 . at present ,
one of the most promising fields of application is superconducting electronics , with the perspective of mgb@xmath0-based devices with good performances operating at a temperature ( @xmath2 10 - 15 k ) accessible to one - stage cryocoolers ..
Please generate the next two sentences of the article
|
after the early observation of the josephson effect in mgb@xmath0 break junctions @xcite , the efforts in this directions have led to the fabrication of various kinds of josephson and tunnel junctions @xcite as well as prototypal squids @xcite .
point - contact spectroscopy ( pcs ) has proved particularly useful in the fundamental research on mgb@xmath0 , since it allows measuring in a direct way both the gaps of this compound @xcite with great accuracy @xcite .
|
12,045 |
Suppose that you have an abstract for a scientific paper: we examine the idea that diffuse and giant molecular clouds and their substructure form as density fluctuations induced by large scale interstellar turbulence .
we do this by closely investigating the topology of the velocity , density and magnetic fields within and at the boundaries of the clouds emerging in high - resolution two - dimensional simulations of the ism including self - gravity , magnetic fields , parameterized heating and cooling and a simple model for star formation .
we find that the velocity field is continuous across cloud boundaries for a hierarchy of clouds of progressively smaller sizes .
cloud boundaries defined by a density - threshold criterion are found to be quite arbitrary , with no correspondence to any actual physical boundary , such as a density discontinuity .
abrupt velocity jumps are coincident with the density maxima , indicating that the clouds are formed by colliding gas streams .
this conclusion is also supported by the fact that the volume and surface kinetic terms in the eulerian virial theorem for a cloud ensemble are comparable in general .
the topology of the magnetic field is also suggestive of the same process , exhibiting bends and reversals where the gas streams collide .
however , no unique trend of alignment between density and magnetic features is observed .
both sub- and super - alfvnic motions are observed within the clouds in the simulations . in the light of these results , we argue that thermal pressure equilibrium is irrelevant for cloud confinement in a turbulent medium , since inertial motions can still distort or disrupt a cloud , unless it is strongly gravitationally bound .
turbulent pressure confinement appears self - defeating , because turbulence contains large - scale motions which necessarily distort lagrangian cloud boundaries , or equivalently cause flux through eulerian boundaries .
we then discuss the compatibility of the present scenario with observational data .
we find that density - weighted velocity....
And you have already written the first three sentences of the full article: theoretical models of interstellar clouds and clumps most frequently assume static or stationary configurations , the clouds being either confined by the external pressure ( @xcite ; bertoldi & mckee 1992 , herafter bm92 ) , or in `` virial equilibrium '' between its self - gravity and some form of internal energy , be it thermal ( e.g. , @xcite ) , micro - turbulent ( e.g. , @xcite ; @xcite ; @xcite ; @xcite ) or magnetic ( e.g. , @xcite ; @xcite , @xcite ) , forming out of instabilities or coagulation of smaller clouds ( see @xcite for a review ) .
nevertheless , the interstellar medium ( ism ) is well known to be highly violent ( e.g. , @xcite ) , and recently it has become increasingly accepted that it is turbulent throughout ( e.g. , @xcite ; see also the volume `` interstellar turbulence '' [ @xcite ] ) .
in such a medium , clouds may naturally form as turbulent density fluctuations as well . within this dynamic , turbulent framework.
Please generate the next two sentences of the article
|
, it is important to reconsider the meaning and feasibility of pressure cloud confinement , either thermal or turbulent .
this is most adequately done in the context of the virial theorem ( vt ) , which is a very useful tool for describing the balance between all the physical agents in molecular clouds .
|
12,046 |
Suppose that you have an abstract for a scientific paper: we analyze the shapes of the hi velocity profiles of the hi nearby galaxy survey ( things ) to study the phase structure of the neutral interstellar medium ( ism ) and its relation to global galaxy properties .
we use a method analogous to the stacking method sometimes used in high redshift hi observations to construct high signal - to - noise ( s / n ) profiles .
we call these high s / n profiles _ super profiles_. we analyze and discuss possible systematics that may change the observed shapes of the super profiles . after quantifying these effects and selecting a sub - sample of unaffected galaxies , we find that the super profiles are best described by a narrow and a broad gaussian component , which are evidence of the presence of the cold neutral medium ( cnm ) and the warm neutral medium ( wnm ) .
the velocity dispersion of the narrow component range from @xmath03.4 to @xmath08.6 @xmath1 with an average of [email protected] @xmath1 , whereas that of the broad component range from @xmath010.1 to @xmath024.3 @xmath1 with an average of [email protected] @xmath1 .
we find that the super profile parameters correlate with star formation indicators such as metallicity , fuv - nuv colors and @xmath3 luminosities .
the flux ratio between the narrow and broad components tends to be highest for high metallicity , high star formation rate ( sfr ) galaxies .
we show that the narrow component identified in the super profiles is associated with the presence of star formation , and possibly with molecular hydrogen . .
And you have already written the first three sentences of the full article: gas in the interstellar medium ( ism ) in disk galaxies can exist in a molecular , atomic or ionised phase .
most of it will be in the form of neutral atomic hydrogen ( hi ) whose hyperfine transition can be detected at the 21-cm wavelength . since the early work of @xcite ,
the neutral atomic ism has been known to exist in two phases , known as the cold neutral medium ( cnm ) and the warm neutral medium ( wnm ) ..
Please generate the next two sentences of the article
|
@xcite first suggested that hi seen in emission and absorption had different line widths because it arose from two distinct components of the ism .
the narrow absorption spectra are caused by a cold component of the ism ( the cnm ) with a temperature of @xmath4 whereas the broad emission spectra arose from a warm component with a temperature as high as @xmath5 ( the wnm ) .
|
12,047 |
Suppose that you have an abstract for a scientific paper: a spatial stochastic model is developed which describes the 3d nanomorphology of composite materials , being blends of two different ( organic and inorganic ) solid phases .
such materials are used , for example , in photoactive layers of hybrid polymer zinc oxide solar cells .
the model is based on ideas from stochastic geometry and spatial statistics .
its parameters are fitted to image data gained by electron tomography ( et ) , where adaptive thresholding and stochastic segmentation have been used to represent morphological features of the considered et data by unions of overlapping spheres .
their midpoints are modeled by a stack of 2d point processes with a suitably chosen correlation structure , whereas a moving - average procedure is used to add the radii of spheres .
the model is validated by comparing physically relevant characteristics of real and simulated data , like the efficiency of exciton quenching , which is important for the generation of charges and their transport toward the electrodes . , , , , , , , , and . .
And you have already written the first three sentences of the full article: using methods from stochastic geometry and spatial statistics , a stochastic model is developed which describes the 3d nanomorphology of composite materials , being blends of two different ( organic and inorganic ) solid phases .
such materials are used , for example , in photoactive layers of hybrid polymer zinc oxide ( zno ) solar cells where the two solid phases play the role of a polymeric electron donor , consisting of , for example , poly(3-hexylthiophene ) , and an inorganic zno - electron acceptor , respectively .
there is a great advantage of polymer solar cells due to their potentially low production costs , in comparison with classical silicon solar cells ..
Please generate the next two sentences of the article
|
however , the efficiency of polymer solar cells critically depends on the intimacy of mixing of the donor and acceptor semiconductors used in these devices to create charges as well as on the presence of unhindered percolation pathways in the individual solid phases of the composite material to transport positive and negative charges toward electrodes ; see , for example , @xcite .
it is therefore very important to have tools at one s disposal which are suitable to analyze and model the 3d morphology of these materials quantitatively .
|
12,048 |
Suppose that you have an abstract for a scientific paper: in this brief presentation , we would like to present our attempts of detecting chirality and mutations from chern - simons gauge theory .
the results show that the generalised knot invariants , obtained from chern - simons gauge theory , are more powerful than jones , homflypt and kauffman polynomials .
however the classification problem of knots and links is still an open challenging problem . .
And you have already written the first three sentences of the full article: the classification of three and four manifolds is one of the open questions which has been addressed by both mathematicians and physicists . in particular
, physicists have shown that a class of quantum field theories called topological field theories provides an elegant approach to solve these problems .
the main idea in any quantum field theory is to represent the theory by an action @xmath0 which gives information about the particle content and their interactions ..
Please generate the next two sentences of the article
|
the interaction strengths are given by coupling constants .
for capturing the topological features of knots or links as shown in fig .
|
12,049 |
Suppose that you have an abstract for a scientific paper: we introduce relative homological and weakly homological categories @xmath0 , where `` relative '' refers to a distinguished class @xmath1 of normal epimorphisms in @xmath2 . it is a generalization of homological categories , but
also protomodular categories can be regarded as examples .
we indicate that the relative versions of various homological lemmas can be proved in a relative homological category . .
And you have already written the first three sentences of the full article: f. borceux and d. bourn @xcite , call a category @xmath2 _ homological _ if it is pointed , regular , and protomodular ( in the sense of bourn @xcite ) ; in fact they claim that such categories provide the most convenient setting for non - abelian versions of various _ standard homological lemmas _ , such as snake lemma , 3@xmath33-lemma , etc . taking this viewpoint , one could still try , however , to introduce a more general setting involving a distinguished class @xmath1 of regular epimorphisms , where the homological lemmas are expected to hold only for short exact sequences @xmath4 with @xmath5 in @xmath1 . in particular
, there is no reason to exclude the trivial case , where @xmath2 is an arbitrary category ( say , pointed and with finite limits and finite colimits ) and @xmath1 the class of all isomorphisms in @xmath2 .
this idea goes back to n. yoneda @xcite , whose _ quasi - abelian _ categories can in fact be defined as pairs @xmath0 , where @xmath2 is an additive category in which the short exact sequences @xmath6 with @xmath7 in @xmath1 have the same properties as all short exact sequences in an abelian category ..
Please generate the next two sentences of the article
|
+ + the purpose of this paper is to present a new notion of relative homological and relative weakly homological categories @xmath0 , such that whenever @xmath2 is a pointed category with finite limits and cokernels / coequalizers , we have : * @xmath8 always is a relative homological category ; * @xmath9 is a relative weakly homological category if and only if @xmath2 is a protomodular category ; * @xmath10 is a relative homological category if and only if it is a relative weakly homological category and if and only if @xmath2 is a homological category ; * @xmath11 is a relative homological category if and only if @xmath2 is a trivial category ; * suitable reformulations of various homological lemmas relative to @xmath1 hold in @xmath2 .
throughout the paper we assume that @xmath2 is a pointed category with finite limits and cokernels , and @xmath1 is a class of morphisms in @xmath2 containing all isomorphisms .
|
12,050 |
Suppose that you have an abstract for a scientific paper: we use a novel method based on the semi - classical analysis of @xmath0-models to describe the phenomenon of strong localization in quasi one - dimensional conductors , obtaining the density of transmission eigenvalues . for several symmetry classes , describing random superconducting and chiral hamiltonians , the target space of the appropriate @xmath0-model is a ( super)group manifold . in these cases
our approach turns out to be exact .
the results offer a novel perspective on localization . .
And you have already written the first three sentences of the full article: beginning with the early work of thouless @xcite , quasi one - dimensional conductors have provided a valuable arena in which to explore the influence of quantum interference effects on the transport properties of weakly disordered phase coherent conductors . by the early 80 s ,
a complete scaling theory of localization in multi - mode wires had been formulated by dorokhov @xcite ( and developed later by mello , pereyra and kumar @xcite ) as a brownian motion of eigenvalues of the transmission matrix the ` dmpk equation ' ( for a recent review see , e.g. , ref . ) . for several symmetry classes , analytic results for the low moments of conductance
were obtained in both the metallic and strongly localized regimes @xcite . lately , a third , and potentially more versatile approach has been developed to investigate quantum transport in ( multi - terminal ) disordered conductors . by formally relating the transmission eigenvalue distribution to a ` multi - component green s function ' ( see below ) , nazarov has shown @xcite that known results in the metallic limit can be inferred from the equations of motion of the average quasi - classical green function @xcite ..
Please generate the next two sentences of the article
|
the transport properties of a conductor are fully specified by the transmission matrix @xmath1 @xcite .
in particular , the landauer - bttiker formula allows the conductance to be expressed through eigenvalues @xmath2 of the ` squared ' transmission matrix , @xmath3 the statistics of the @xmath2 follow the universal dorokhov distribution , valid in the metallic limit ( i.e. where the dimensionless conductance @xmath4 ) : @xmath5 by solving the corresponding quasi - classical equation in the diffusive limit , eq .
|
12,051 |
Suppose that you have an abstract for a scientific paper: at the intersection of galactic dynamics , evolution and global structure , issues such as the relation between bars and spirals and the persistence of spiral patterns can be addressed through the characterization of the angular speeds of the patterns and their possible radial variation .
the radial tremaine - weinberg ( twr ) method , a generalized version of the tremaine - weinberg method for observationally determining a single , constant pattern speed , allows the pattern speed to vary arbitrarily with radius . here
, we perform tests of the twr method with regularization on several simulated galaxy data sets .
the regularization is employed as a means of smoothing intrinsically noisy solutions , as well as for testing model solutions of different radial dependence ( e.g. constant , linear or quadratic ) .
we test these facilities in studies of individual simulations , and demonstrate successful measurement of both bar and spiral pattern speeds in a single disk , secondary bar pattern speeds , and spiral winding ( in the first application of a tw calculation to a spiral simulation ) .
we also explore the major sources of error in the calculation and find uncertainty in the major axis position angle most dominant . in all cases ,
the method is able to extract pattern speed solutions where discernible patterns exist to within @xmath0 of the known values , suggesting that the twr method should be a valuable tool in the area of galactic dynamics . for utility
, we also discuss the caveats in , and compile a prescription for , applications to real galaxies . .
And you have already written the first three sentences of the full article: one of the prime unresolved issues in the dynamics and evolution of galaxy disks remains the origin and evolution of large - scale bar and spiral structure .
though the persistence of grand - design spirals has been tied observationally to the presence of bars or companions @xcite , virtually nothing is known about the actual lifetimes of spiral patterns . additionally , despite indications that the relation between bar and spiral pattern speeds ( which @xcite first argued may not be equal ) may be important for understanding the role of bars in angular momentum transfer during secular disk evolution ( e.g. @xcite and @xcite ) , there are as yet unanswered questions about the connections between multiple patterns in different radial zones . while mode - coupling between patterns , which allows efficient outward angular momentum transfer in disks ( @xcite ; @xcite ) seems a most promising link , in 2d n - body simulations with a dissipative gas component @xcite find evidence for spiral structure in the absence of a bar , bar - spiral mode coupling , spiral - spiral mode coupling , and multiple pattern speeds without mode coupling . clearly , to address questions about the persistence of spiral patterns and the relation between bars and spirals requires not only determination of the pattern speed but how it varies with radius
; only with accurate measurement of bar and spiral or inner and outer spirals pattern speeds in the same galaxy can we confirm whether spiral structure is steady or winding , whether bars and spiral pattern speeds are equal or are unrelated , whether mode - coupling exists , and the domain and number of patterns that can be sustained in a disk ..
Please generate the next two sentences of the article
|
because they are not directly accessible through observation , pattern speeds are often determined with indirect means such as the identification of predicted behavior at resonance radii ( e.g. @xcite ; @xcite ) or kinematic and morphological comparisons of simulated and observed structure ( e.g. @xcite ; @xcite ) .
it is also clearly desirable to employ methods for estimating pattern speeds which do not rely on theoretical models or simulation .
|
12,052 |
Suppose that you have an abstract for a scientific paper: empirical evidence suggest that most urban systems experience a transition from a monocentric to a polycentric organisation as they grow and expand .
we propose here a stochastic , out - of - equilibrium model of the city which explains the appearance of subcenters as an effect of traffic congestion .
we show that congestion triggers the instability of the monocentric regime , and that the number of subcenters and the total commuting distance within a city scale sublinearly with its population , predictions which are in agreement with data gathered for around 9000 us cities between 1994 and 2010 .
as cities grow , they evolve from monocentric organisations where all the activities are concentrated in the same geographical area usually the central business district to more distributed , polycentric organisations @xcite .
traditional approaches in spatial economics have attempted to describe the phenomenon within the framework of equilibrium models of the city @xcite .
these models are traditionally based on the concept of agglomeration economies to explain why economical activities tend to group and the spatial distribution of wages and rents across the urban space .
however , these approaches fail at giving a satisfactory quantitative account @xcite of the polycentric transition of cities .
first , they describe a city as being in an equilibrium characterised by static spatial distributions of households and business firms . however , the equilibrium assumption is unsupported as cities are out - of - equilibrium systems and their dynamics is of particular interest for practical applications @xcite .
second , these models integrate so many interactions and variables that it is difficult to understand the hierarchy of processes governing the evolution of cities , which ones are fundamental and which ones are irrelevant . yet
, traffic congestion is not explicitly taken into account in the existing models , despite being mentioned in the economics literature as a possible reason for the....
And you have already written the first three sentences of the full article: the simulation results presented in these supplementary materials are obtained in the following way .
we first distribute randomly a number @xmath8 of potential activity centers uniformly in the unit circle .
then , at each time step , we add a worker @xmath0 at a random position in the circle , and compute the cost functions @xmath72 for all potential activity centers @xmath1 ..
Please generate the next two sentences of the article
|
we then connect the worker with the center maximizing the cost function , and add one to the value of the traffic corresponding to this center .
we repeat this procedure until all workers are connected to a center .
|
12,053 |
Suppose that you have an abstract for a scientific paper: by altering the polarization , phase and amplitude at the exit pupil , the intensity distribution near the focal plane of a solid immersion lens(sil ) system can be changed .
we have studied how the resolution and focal depth changes for a few particular cases .
it was seen that by impinging radial polarization on a sil system , we may obtain a rotational symmetric z - component of the focused wavefront with spot size similar to that predicted by scalar theory .
we also observed that it was possible to manipulate the contributions from the homogeneous and inhomogeneous waves behind the sil by changing the amplitude and phase distribution at the aperture . in this way it may be possible to improve both the resolution and focal depth of the system . .
And you have already written the first three sentences of the full article: the maximum resolution achievable with conventional optical techniques is determined by the classical diffraction limit .
the minimum optical spot diameter can be expressed as @xmath0 , where @xmath1 is the wavelength in air , and @xmath2 is the numerical aperture(n is the refractive index and @xmath3 is the convergence semiangle ) .
fortunately , the diffraction limit can be circumvented by use of scanning near - field optical systems , where resolutions less than 50 nm can be achieved . unfortunately , near - field techniques have been troubled by low transmission efficiencies , and therefore poor signal to noise ratios ..
Please generate the next two sentences of the article
|
although recent research have improved the transmission efficiency considerably , it is still only @xmath4 at 100 nm spot size@xcite .
another way to increase the resolution is by application of a solid immersion lens(sil)@xcite .
|
12,054 |
Suppose that you have an abstract for a scientific paper: @xmath0 her is a nearby quadruple system with a g - subgiant primary and several low mass companions arranged in a 2@xmath1 architecture . while the bc components have been well characterized , the ab component has been detected astrometrically and with direct imaging but there has been some confusion over its nature , in particular whether the companion is stellar or substellar . using near - infrared spectroscopy we are able to estimate the spectral type of the companion as a m4@xmath21v star .
in addition , we have measured the astrometry of the system for over a decade .
we combined the astrometry with archival radial velocity measurements to compute an orbit of the system . from the combined orbit ,
we are able to compute the mass sum of the system . using the estimated mass of the primary
, we estimate the mass of the secondary as 0.32 m@xmath3 , which agrees with the estimated spectral type .
our computed orbit is preliminary due to the incomplete orbital phase coverage , but it should be sufficient to predict ephemerides over the next decade . .
And you have already written the first three sentences of the full article: ( hd 161797 = hip 86974 = wds 17465 + 2743 ) is the third closest quadruple star system to the sun @xcite at a distance of 8.3 pc @xcite .
the system consists of the g5iv primary @xcite surrounded by several m dwarfs .
the closest companion is the ab component , which has long been known from astrometric variations of the primary @xcite and from radial velocity ( rv ) variations @xcite ..
Please generate the next two sentences of the article
|
the companion was first imaged by @xcite with the adaptive optics ( ao ) system on the 2.5 m telescope at mt .
wilson observatory .
|
12,055 |
Suppose that you have an abstract for a scientific paper: measurements in quantum mechanics can not only effectively freeze the state of the quantum system ( the quantum zeno effect ) but also accelerate the time evolution of the system ( the quantum anti - zeno effect ) . in studies of the quantum zeno and anti - zeno effects , a quantum state , usually an excited state of the system , is prepared repeatedly by projecting the quantum state onto the initial state again and again . in this paper
, we repeatedly prepare the initial quantum state in a different manner . instead of only performing projective measurements , we allow unitary operations to be performed , on a very short time - scale , after each measurement .
we can then repeatedly prepare the initial quantum state by performing some projective measurement and thereafter , after each measurement , performing a suitable unitary operation to repeatedly end up with the initial state .
our objective thereafter is to find the projective measurements that need to repeatedly performed such that we obtain the minimum possible effective decay rate of the quantum state .
consequently , the quantum state is maximally protected from its environment .
we find that these optimized projective measurements keep on changing depending on the measurement time interval .
we explicitly find the projective measurements that need to be performed , as well as the optimized effective decay rate , for a variety of system - environment models such as the population decay model , the pure dephasing model , the spin - boson model , and the large spin - boson model .
we find that there can be considerable differences between this optimized effective decay rate and the usual decay rate obtained by repeatedly projecting onto the initial state .
in particular , the zeno and anti - zeno regimes can be considerably modified .
rapid repeated measurements can slow down the time evolution of a quantum system , an effect known as the quantum zeno effect ( qze ) @xcite .
it has also been found that if the measurements are....
And you have already written the first three sentences of the full article: let us begin by considering a single two - level system interacting with an arbitrary environment .
the hamiltonian of the system is @xmath0 , the environment hamiltonian is @xmath1 , and there is some interaction between the system and the environment that is described by the hamiltonian @xmath2 .
the total system - environment hamiltonian is thus @xmath3 . at time @xmath4.
Please generate the next two sentences of the article
|
, we prepare the system state @xmath5 . in the usual treatment of the quantum zeno and anti - zeno effects ,
repeated projective measurements described by the projector @xmath6 are then performed on the system with time interval @xmath7 .
|
12,056 |
Suppose that you have an abstract for a scientific paper: we have obtained deep infrared @xmath0 and @xmath1 band observations of nine @xmath2 arcmin fields in the small magellanic cloud ( smc ) with the eso new technology telescope equipped with the sofi infrared camera . in these fields ,
34 rr lyrae stars catalogued by the ogle collaboration were identified . using different theoretical and empirical calibrations of the infrared period - luminosity - metallicity relation , we find consistent smc distance moduli , and find a best true distance modulus to the smc of @xmath3 ( statistical ) @xmath4 0.12 ( systematic ) mag which agrees well with most independent distance determinations to this galaxy , and puts the smc 0.39 mag more distant than the lmc for which our group has recently derived , from the same technique , a distance of 18.58 mag . .
And you have already written the first three sentences of the full article: in our ongoing araucaria project ( e.g. gieren et al .
2005a ) , we are applying a number of different stellar standard candles to independently determine the distances to a sample of nearby galaxies .
the systematic differences between the distance results obtained for the individual galaxies from the various stellar candles will be analyzed in forthcoming papers ..
Please generate the next two sentences of the article
|
this analysis is expected to lead to a detailed understanding of how the various stellar techniques , which are fundamental to calibrate the first rungs of the distance ladder , depend on metallicity and age . while the objects we use for the distance determinations are usually detected from optical wide - field imaging surveys of the target galaxies ( e.g. pietrzyski et al .
2002b ) , the most accurate distance work is then done from follow - up near - infrared images which virtually eliminate reddening as a significant source of error on the results .
|
12,057 |
Suppose that you have an abstract for a scientific paper: in this work , we investigate the problem of secretly broadcasting of three - qubit entangled state between two distant partners .
the interesting feature of this problem is that starting from two particle entangled state shared between two distant partners we find that the action of local cloner on the qubits and the measurement on the machine state vector generates three - qubit entanglement between them .
the broadcasting of entanglement is made secret by sending the measurement result secretly using cryptographic scheme based on orthogonal states .
further we show that this idea can be extended to generate three particle entangled state between three distant partners . .
And you have already written the first three sentences of the full article: no - cloning theorem is one of the most fundamental theorem in quantum computation and quantum information[1 ] .
the theorem states that there does not exist any process , which turns two distinct nonorthogonal quantum states @xmath0,@xmath1 into states @xmath2,@xmath3 respectively.this restrictions can be successfully utilized in quantum cryptography[2 ] .
although we can not copy an unknown quantum state perfectly but one can always do it approximately . beyond the no - cloning theorem , one can clone an arbitrary quantum state perfectly with some non - zero probability[3].in the past years , much progress has been made in designing quantum cloning machine ..
Please generate the next two sentences of the article
|
a first step towards the construction of approximate quantum cloning machine was taken by buzek and hillery in 1996 [ 4].they showed that the quality of the copies produced by their machine remain same for all input state.this machine is popularly known as universal quantum cloning machine ( uqcm ) .
later this uqcm was proved to be optimal [ 5 ] .
|
12,058 |
Suppose that you have an abstract for a scientific paper: we have performed small - angle light - scattering measurements of the static structure factor of a critical binary mixture undergoing diffusive partial remixing .
an uncommon scattering geometry integrates the structure factor over the sample thickness , allowing different regions of the concentration profile to be probed simultaneously .
our experiment shows the existence of interface capillary waves throughout the macroscopic evolution to an equilibrium interface , and allows to derive the time evolution of surface tension .
interfacial properties are shown to attain their equilibrium values quickly compared to the system s macroscopic equilibration time .
pacs numbers : 68.10.-m , 68.35.fx , 05.40.-a , 68.35.rh . .
And you have already written the first three sentences of the full article: the fluctuations at the interface between two fluid phases at thermodynamic equilibrium have been studied very extensively starting from the beginning of this century @xcite , and particular investigation has concerned those at the interfaces of critical fluids @xcite . although the features of equilibrium interfacial fluctuations are now relatively well known , the behavior of an interface under nonequilibrium conditions is still not well understood .
many experiments have been performed to detect an effective nonequilibrium surface tension in miscible fluids @xcite but the results obtained are mainly qualitative . in this paper
we will present experimental results about the behavior of interfacial fluctuations during the diffusive remixing of partially miscible phases . in this system.
Please generate the next two sentences of the article
|
the interface between two fluid phases is being crossed by a macroscopic mass flow .
it is well known that the fluctuations in the equilibrium states before and after the diffusive partial remixing are controlled by surface tension and gravity .
|
12,059 |
Suppose that you have an abstract for a scientific paper: dimuon production has been studied in a series of fixed - target experiments at fermilab during the last two decades .
highlights from these experiments , together with recent results from the fermilab e866 experiment , are presented .
future prospects for studying the parton distributions in the nucleons and nuclei using dimuon production are also discussed .
address = university of illinois at urbana - champaign , urbana , il 61801 .
And you have already written the first three sentences of the full article: the drell - yan process @xcite , in which a charged lepton pair is produced in a hadron - hadron interaction via the electromagnetic @xmath0 process , has provided unique information on parton distributions . in particular , the drell - yan process has been used to determine the antiquark contents of nucleons and nuclei @xcite , as well as the quark distributions of pions , kaons , and antiprotons @xcite .
such information is difficult , if not impossible , to obtain from dis experiments .
as the drell - yan process can be well described by next - to - leading order qcd calculations @xcite , a firm theoretical framework exists for utilizing the drell - yan process to extract the parton distributions . during the last two decades , a series of fixed - target dimuon production experiments ( e772 , e789 , e866 ) have been carried out using 800 gev / c proton beam at fermilab . at 800 gev / c ,.
Please generate the next two sentences of the article
|
the dimuon data contain drell - yan continuum up to dimuon mass of @xmath1 gev as well as quarkonium productions ( j/@xmath2 , @xmath3 , and @xmath4 resonances ) . the drell - yan process and quarkonium productions often provide complementary information , since drell - yan is an electromagnetic process via quark - antiquark annihilation while the quarkonium production is a strong interaction process dominated by gluon - gluon fusion at this beam energy .
the fermilab dimuon experiments covers a broad range of physics topics .
|
12,060 |
Suppose that you have an abstract for a scientific paper: we study the azimuthal scatter in the radial profiles of x - ray luminous galaxy clusters , with two sets of high - resolution cosmological re - simulations obtained with the codes enzo and gadget2 .
the average gas profiles are computed for different angular sectors of the cluster projected volume , and compared with the mean cluster profiles at each radius from the center .
we report that in general the level of azimuthal scatter is found to be @xmath0 per cent for gas density , temperature and entropy inside @xmath1 , and @xmath2 per cent for x - ray luminosity for the same volume .
these values generally doubles going to @xmath3 from the cluster center , and are generally found to be higher ( by @xmath4 per cent ) in the case of perturbed systems .
a comparison with results from recent _ suzaku _ observations is discussed , showing the possibility to simply interpret the large azimuthal scatter of observables in light of our simulated results .
[ firstpage ] galaxy : clusters , general methods : numerical intergalactic medium large - scale structure of universe 0.4 cm .
And you have already written the first three sentences of the full article: only a fraction of the volume occupied by the intra - cluster medium is currently mapped with x - ray observations .
the typical measures of the surface brightness , temperature and metal abundance extend out to a fraction of the virial radius , @xmath5 , and only in a few cases meaningful estimates at @xmath6 ( @xmath1 ) is the radius enclosing a mean matter over - density of 500 ( 200 ) times the critical density of the universe .
compared to the cluster virial radius these radii correspond to @xmath7 and to @xmath8 . ] or beyond are obtained ..
Please generate the next two sentences of the article
|
because of this , more than two - thirds of the typical cluster volume , where the primordial gas is accreted and the dark matter ( dm ) halo is forming , are still unknown for what concerns the gas / dm mass distribution and the related thermodynamical properties .
this poses a limitation in our ability to characterize the physical processes presiding over the formation and evolution of clusters , and thus to use them as high - precision cosmological tools ( see ettori & molendi 2010 and references therein ) . in general the surface brightness distribution , requiring lower counts statistic , is easier to be characterized and has been successfully studied with _
|
12,061 |
Suppose that you have an abstract for a scientific paper: in this paper , we redefine the graph fourier transform ( gft ) under the dsp@xmath0 framework .
we consider the jordan eigenvectors of the directed laplacian as graph harmonics and the corresponding eigenvalues as the graph frequencies .
for this purpose , we propose a shift operator based on the directed laplacian of a graph . based on our shift operator ,
we then define total variation of graph signals , which is used in frequency ordering .
we achieve natural frequency ordering and interpretation via the proposed definition of gft .
moreover , we show that our proposed shift operator makes the lsi filters under dsp@xmath0 to become polynomial in the directed laplacian .
graph signal processing , graph fourier transform , directed laplacian . .
And you have already written the first three sentences of the full article: defined on network - like structures are encountered in a large number of scenarios including molecular interaction in biological systems , computer networks , sensor networks , social and citation networks , the internet and the world wide web , power grids , transportation networks @xcite , and many more .
such data can be visualized as a set of scalar values , known as a graph signal , lying on a particular structure , i.e. , a graph . in computer graphics ,
data defined on any geometrical shape described by polygon meshes can be formulated as a graph signal @xcite ..
Please generate the next two sentences of the article
|
+ the irregular structure of the underlying graph , as opposed to the regular structure in case of time - series and image signals dealt in classical signal processing @xcite , imposes a great challenge in analysis and processing of graph signals .
fortunately , recent work toward the development of important concepts and tools , extending classical signal processing theory , including sampling and interpolation on graphs @xcite , graph - based transforms @xcite , and graph filters @xcite have enriched the field of graph signal processing .
|
12,062 |
Suppose that you have an abstract for a scientific paper: we have studied the dynamics of an equal - mass magnetized neutron - star binary within a resistive magnetohydrodynamic ( rmhd ) approach in which the highly conducting stellar interior is matched to an electrovacuum exterior . because our analysis is aimed at assessing the modifications introduced by resistive effects on the dynamics of the binary after the merger and through to collapse , we have carried out a close comparison with an equivalent simulation performed within the traditional ideal magnetohydrodynamic approximation .
we have found that there are many similarities between the two evolutions but also one important difference : the survival time of the hypermassive neutron star increases in a rmhd simulation .
this difference is due to a less efficient magnetic - braking mechanism in the resistive regime , in which matter can move across magnetic - field lines , thus reducing the outward transport of angular momentum .
both the rmhd and the ideal magnetohydrodynamic simulations carried here have been performed at higher resolutions and with a different grid structure than those in previous work of ours [ l. rezzolla , b. giacomazzo , l. baiotti , j. granot , c. kouveliotou , and m. a. aloy , astrophys .
j. letters 732 , l6 ( 2011 ) ] , but confirm the formation of a low - density funnel with an ordered magnetic field produced by the black hole torus system . in both regimes
the magnetic field is predominantly toroidal in the highly conducting torus and predominantly poloidal in the nearly evacuated funnel .
reconnection processes or neutrino annihilation occurring in the funnel , none of which we model , could potentially increase the internal energy in the funnel and launch a relativistic outflow , which , however , is not produced in these simulations . .
And you have already written the first three sentences of the full article: with the rapid progress made in upgrading and testing a series of advanced interferometric gravitational - wave detectors such as ligo @xcite , virgo @xcite , and kagra @xcite , there are now great expectations that in the next five years we will witness the first direct detection of gravitational waves .
prime sources for such a detection are binary systems of compact objects , namely , binary systems comprising either two black holes , a black hole and a neutron star , or two neutron stars . the latter configuration , in particular , is potentially a very interesting one , as it will represent the most common source , with a realistic expected detection rate of @xmath0 @xcite .
a detection of gravitational waves from binary neutron stars would yield a wealth of information about the chirp mass , the orientation , and the localization of the binary but also possibly the mass , spin and radius of the individual stars @xcite . in turn , this information could set constraints on the equation of state ( eos ) of the matter in their interior . indeed , a number of recent investigations have revealed that it is possible to set serious constraints on the properties of the neutron - star structure and eos , either when using the inspiral signal only @xcite , or when exploiting the rich spectral features of the postmerger signal @xcite . at the same time.
Please generate the next two sentences of the article
|
, the merger of a binary system containing at least one neutron star represents arguably the most attractive scenario to explain the complex phenomenology associated with short gamma - ray bursts ( sgrbs ) , although many alternatives exist [ see ref .
@xcite for a recent review ] . while such a scenario was suggested already 30 years ago @xcite , numerical simulations ( see , e.g. , refs .
|
12,063 |
Suppose that you have an abstract for a scientific paper: the spectrum of eigenenergies of a quantum integrable system whose hamiltonian depends on a single parameter shows degeneracies ( crossings ) when the parameter varies .
we derive a semiclassical expression for the density of crossings in the plane energy - parameter , that is the number of crossings per unit of energy and unit of parameter , in terms of classical periodic orbits .
we compare the results of the semiclassical formula with exact quantum calculations for two specific quantum integrable billiards .
-0.25 in 6.75 in + .
And you have already written the first three sentences of the full article: the analysis of energy spectra of different physical bounded systems has always been an interesting subject in quantum mechanics .
the energy level spacings as well as the existence of degeneracies ( crossings ) in such systems have been widely studied during recent years .
the number of degrees of freedom , the separability of the problem and the number of free parameters involved , among others , are very important features which have to be taken into account when a given quantum spectrum is analyzed ..
Please generate the next two sentences of the article
|
starting from percival s ideas @xcite for systems with more than one degree of freedom , two kinds of spectra have been distinguished .
the regular spectrum , whose level spacing is characterized by a poisson distribution @xcite , is associated with integrable problems ( the harmonic oscillator is an exception ) .
|
12,064 |
Suppose that you have an abstract for a scientific paper: ultracold atoms uniformly filling an optical lattice can be treated like an artificial crystal .
an implementation including the atomic occupation of a single excited atomic state can be represented by a two - component bose - hubbard model .
its phase diagram at zero temperature exhibits a quantum phase transition from a superfluid to a mott insulator phase .
the dynamics of electronic excitations governed by electrostatic dipole - dipole interactions in the ordered regime can be well described by wave - like collective excitations called excitons . here
we present an extensive study of such excitons for a wide range of optical lattice geometries and of different dimensionality including boundary effects in finite lattices . as they are coupled to the free space radiation field
, their decay depends on the lattice geometry , polarization and lattice constant .
their lifetimes can vary over many orders of magnitude from metastable propagation to superradiant decay .
particularly strong effects occur in one dimensional atomic chains coupled to tapered optical fibers where free space emission can be completely suppressed and only a superradiant interaction with the fiber modes takes place .
we show that coherent transfer of excitons among spatially separated optical lattices can be controlled and represents a promising candidate for quantum information transfer . for an optical lattice within a cavity the excitons
are coupled to cavity photons and the resulting collective cavity qed model can be efficiently formulated in terms of polaritons as elementary excitations .
their properties are explicitly calculated for different lattices and they constitute a non - destructive monitoring tool for important system properties as e.g. the atomic quantum statistics .
even the formation of bound states and molecules in optical lattices manifests itself in modified polariton properties as e.g. an anisotropic optical spectrum .
partial dissipation of the exciton energy in the lattice leads to....
And you have already written the first three sentences of the full article: trapping and manipulating ultracold neutral atoms in an array of optical potentials opened a vast new research area in the field of quantum fluids and solid state modeling @xcite . demonstrating the superfluid to mott insulator quantum phase transition of interacting bosons in an optical lattice laid the foundation to study and simulate strongly correlated quantum many - body systems with a big impact on condensed matter physics @xcite .
ultracold atoms in optical lattices are now one of the most flourishing directions of experimental and theoretical quantum physics @xcite . besides fundamental physics issues on entanglement , measurement and decoherence @xcite , more and more applications appear for the quantum simulations for a wide range of puzzling effects in solid state physics .
a bec of a dilute bosons , in which a very large number of atoms occupy the same quantum state of motion , was experimentally realized by several groups @xcite ..
Please generate the next two sentences of the article
|
optical control of the quantum state of such bec opened the door to a new generation of experiments @xcite .
in particular the loading of the bec into a standing wave formed by pairs of counter propagating far detuned laser beams creates a synthetic controllable periodic lattice @xcite .
|
12,065 |
Suppose that you have an abstract for a scientific paper: the large area telescope ( lat ) instrument on board the fermi satellite consists of a multi - layer silicon - strip tracker interleaved with tungsten converters ( tkr ) , followed by a csi crystal hodoscopic calorimeter ( cal ) .
sixteen tkr and cal modules are assembled in a 4@xmath04 array .
a segmented anticoincidence plastic scintillator ( acd ) surrounds the tkrs .
the primary cosmic - ray electron / positron energy spectrum has been measured from 20 gev to 1 tev using a dedicated event analysis that ensures efficient electron detection and reduced hadron contamination .
results from detailed monte carlo simulations have been used to reconstruct the observed energy spectrum to the primary cosmic ray spectrum .
we present here details of the analysis procedure and the energy spectrum reconstruction .
cosmic rays ; spectral analysis ; electrons . .
And you have already written the first three sentences of the full article: the electron component in the primary cosmic radiation ( cr ) consists of both electrons and positrons . a number of measurements of their energy spectrum by balloon - borne experiments @xcite and by a single space mission @xcite have shown that the electron intensity , about 1% of the proton intensity at 10 gev , decreases more rapidly with energy than that of cosmic - ray nuclei .
although existing data exhibit sizeable statistical and systematic uncertainties , it is clear that the power - law index of the electron spectrum above 10 gev is larger than 3.0 , in contrast to the proton index of 2.7 .
high - energy electrons in the galactic magnetic field lose energy through synchrotron radiation and by inverse compton collisions with low - energy photons ..
Please generate the next two sentences of the article
|
the measurement of the energy spectrum of primary electrons can give information on the galactic magnetic field as well as on the confinement time of electrons in the galaxy and on the distribution of particle sources in our galaxy .
positrons are believed to be mainly created in secondary production processes resulting from the interaction of cr nuclei with the interstellar medium .
|
12,066 |
Suppose that you have an abstract for a scientific paper: supernova 1006 is the first shell type supernova remnant to show evidence of particle acceleration to tev energies . in the present paper
we examine this possibility by modeling the observed x - ray non - thermal emission in terms of synchrotron radiation from fermi accelerated electrons .
the predicted synchrotron spectrum fits the radio and non - thermal component of the observed soft x - ray to hard x - ray emission quite well .
these particles can produce tev gamma rays by inverse compton scattering on the microwave radiation and other ambient fields , and the derived electron distribution is also used to calculate the expected inverse compton flux .
we find that if the remnant is characterised by a magnetic field strength lower than @xmath0 g , then the tev flux can be higher than that of the crab nebula .
about 75% of the tev emission from sn 1006 is expected to be concentrated in the synchrotron bright ne and sw rims ( the hard aegis " ) of the remnant , which would allow a sensitive search if the atmospheric imaging cherenkov technique is used . .
And you have already written the first three sentences of the full article: the type ia supernova remnant g327.6 + 14.6 , or sn 1006 , is the remnant of the explosion which took place in ad 1006 .
the distance to this source is between 1.4 and 2.1 kpc ( green 1988 ) .
its mean expansion rate has been measured as @xmath1 arcsec / yr , which implies a present expansion speed of @xmath2 km / s for an average distance of 1.8 kpc . the time dependence of the expansion ( @xmath3 ) is consistent with sedov expansion , or with a forward / reverse shock pair moving into constant - density material ( moffett , goss , & reynolds 1993 ) ..
Please generate the next two sentences of the article
|
the asca detection of power law x - ray emission from the bright northeastern ( ne ) and southwestern ( sw ) rims of sn 1006 led koyama et al .
( 1995 ) to infer the existence of electrons accelerated by the first order fermi mechanism up to energies of @xmath4 tev .
|
12,067 |
Suppose that you have an abstract for a scientific paper: the self - consistent procedure in electronic structure calculations is revisited using a highly efficient and robust algorithm for solving the non - linear eigenvector problem i.e. @xmath0 .
this new scheme is derived from a generalization of the feast eigenvalue algorithm to account for the non - linearity of the hamiltonian with the occupied eigenvectors . using a series of numerical examples and the dft - kohn / sham model
, it will be shown that our approach can outperform the traditional scf mixing - scheme techniques by providing a higher converge rate , convergence to the correct solution regardless of the choice of the initial guess , and a significant reduction of the eigenvalue solve time in simulations . .
And you have already written the first three sentences of the full article: although first - principle calculations in general , and dft in particular , have provided a practical ( i.e. numerical tractable ) path for solving the electronic structure problem , they have introduced new numerical challenges on their own . within the single electron picture ,
the hamiltonian operator depends on the occupied eigenfunctions and the resulting eigenvalue problem becomes fully non - linear ( i.e. @xmath0 ) . in practice , this _ non - linear eigenvector problem _ is commonly addressed using a self - consistent field method ( scf ) wherein a series of linear eigenvalue problems ( i.e. @xmath1 ) , needs to be solved iteratively until convergence @xcite . successfully reaching convergence by performing scf iterations is of paramount importance to first - principle quantum chemistry and solid - state physics simulations software .
a typical self - consistent iteration procedure for the discretized dft / kohn - sham problem is represented in figure [ fig1 ] . basic self - consistent procedure for solving the ( discretized ) non - linear eigenvector problem with @xmath2 real symmetric and @xmath3 symmetric positive definite ( using non - orthogonal basis functions ) , and obtaining the ground state electron density @xmath4 ( with a factor @xmath5 for spin ) . for the dft / kohn - sham problem , the hamiltonian @xmath6 = -\delta + v_h[n]+v_{xc}[n]+v_{ext}$ ] ,.
Please generate the next two sentences of the article
|
is composed of the hartree potential @xmath7 ( solution of poisson equation ) , the exchange - correlation potential @xmath8 , and other external potential @xmath9 including the ionic potential . ]
traditional scf mixing methods employ successive approximation iterates of a fixed point mapping to generate the new input electron density at each cycle .
|
12,068 |
Suppose that you have an abstract for a scientific paper: in this work we derive the general conditions for obtaining nonreciprocity in multi - mode parametrically - coupled systems .
the results can be applied to a broad variety of optical , microwave , and hybrid systems including recent electro- and opto - mechanical devices . in deriving these results
, we use a graph - based methodology to derive the scattering matrix .
this approach naturally expresses the terms in the scattering coefficients as separate graphs corresponding to distinct coupling paths between modes such that it is evident that nonreciprocity arises as a consequence of multi - path interference and dissipation in key ancillary modes .
these concepts facilitate the construction of new devices in which several other characteristics might also be simultaneously optimized . as an example
, we synthesize a novel three - mode unilateral amplifier design by use of graphs .
finally , we analyze the isolation generated in a common parametric multi - mode system , the dc - squid . .
And you have already written the first three sentences of the full article: reciprocity is the symmetry of a physical system with respect to the exchange of a source and detector .
for example , in systems which demonstrate nonreciprocal behavior the transmission loss and/or phase delay depends on the direction of propagation @xcite . in general ,
reciprocal symmetry can be violated in multi - mode devices and the most well - known examples are ferrite - based circulators and isolators @xcite ..
Please generate the next two sentences of the article
|
such devices are useful in several practical contexts : circulators for instance are commonly employed in both optical @xcite and cryogenic microwave systems @xcite to reduce reflections and , more importantly , to protect from amplifier backaction on the device - under - test .
likewise , in superconducting quantum information , circulators are often used to direct the amplified reflected signal from lumped - element superconducting parametric amplifiers .
|
12,069 |
Suppose that you have an abstract for a scientific paper: in a graphene bilayer with bernal stacking both @xmath0 and @xmath1 orbital landau levels have zero kinetic energy .
an electronic state in the @xmath2 landau level consequently has three quantum numbers in addition to its guiding center label : its spin , its valley index @xmath3 or @xmath4 , and an orbital quantum number @xmath5 the two - dimensional electron gas ( 2deg ) in the bilayer supports a wide variety of broken - symmetry states in which the pseudospins associated these three quantum numbers order in a manner that is dependent on both filling factor @xmath6 and the electric potential difference between the layers . in this paper , we study the case of @xmath7 in an external field strong enough to freeze electronic spins . we show that an electric potential difference between layers drives a series of transitions , starting from interlayer - coherent states ( ics ) at small potentials and leading to orbitally coherent states ( ocs ) that are polarized in a single layer .
orbital pseudospins carry electric dipoles with orientations that are ordered in the ocs and have dzyaloshinskii - moriya interactions that can lead to spiral instabilities .
we show that the microwave absorption spectra of icss , ocss , and the mixed states that occur at intermediate potentials are sharply distinct . .
And you have already written the first three sentences of the full article: semiconductor double - quantum - well systems in a quantizing magnetic field develop spontaneous inter - layer coherence when the wells are brought into close proximity.@xcite spontaneous coherence leads to a variety of fascinating transport effects including counterflow superfluidity and anomalous interlayer tunneling , and to unusual charged excitations such as merons . a convenient way to describe these ground states is to use a pseudospin language in which the _ which layer _ degree - of - freedom is mapped to a @xmath8 pseudospin . in this language ,
the ground state of a bilayer at total filling factor @xmath9 is an easy - plane pseudospin ferromagnet . at higher filling factors ,
still more exotic states occur , for example states in which the pseudospin orientation varies in space and a charge - density - wave is formed.@xcite interest has recently been growing in the strong - magnetic - field ordered states of graphene bilayers ..
Please generate the next two sentences of the article
|
single layer graphene@xcite is a two - dimensional honeycomb lattice network of carbon atoms .
bilayer graphene@xcite consists of two graphene layers separated by a fraction of a nanometer . in the normal bernal stacking structure ,
|
12,070 |
Suppose that you have an abstract for a scientific paper: the silicate cross section peak near 10 produces emission and absorption features in the spectra of dusty galactic nuclei observed with the _ spitzer space telescope_. especially in ultraluminous infrared galaxies , the observed absorption feature can be extremely deep , as iras 08572 + 3915 illustrates .
a foreground screen of obscuration can not reproduce this observed feature , even at large optical depth .
instead , the deep absorption requires a nuclear source to be deeply embedded in a smooth distribution of material that is both geometrically and optically thick .
in contrast , a clumpy medium can produce only shallow absorption or emission , which are characteristic of optically - identified active galactic nuclei . in general ,
the geometry of the dusty region and the total optical depth , rather than the grain composition or heating spectrum , determine the silicate feature s observable properties .
the apparent optical depth calculated from the ratio of line to continuum emission generally fails to accurately measure the true optical depth .
the obscuring geometry , not the nature of the embedded source , also determines the far - ir spectral shape . .
And you have already written the first three sentences of the full article: the observable spectra of the nuclei of galaxies depend on both the underlying emission sources and the subsequent obscuration and reprocessing of their light by material along the line of sight .
dust is common in these nuclear regions , so its spectral signature is often observed at mid - infrared ( mid - ir ) wavelengths . in particular , the silicate cross section peak near 10 produces a spectral feature that is observed frequently in absorption @xcite and sometimes in emission @xcite .
@xcite examine local active galactic nuclei ( agns ) and ultraluminous infrared galaxies ( ulirgs ) with the striking result that the average spectra of various classes of galaxies show marked differences in the 10 silicate feature ( their fig ..
Please generate the next two sentences of the article
|
1 ) . we seek a physical explanation for the differences among these families .
moreover , the underlying origin of the distinct classes must also account for the most extreme example , the deep absorption of the ulirg iras 08572 + 3915 .
|
12,071 |
Suppose that you have an abstract for a scientific paper: a rational representation for the self - energy is explored to interpolate the solution of the anderson impurity model in general orbitally degenerate case .
several constrains such as the friedel s sum rule , high frequency moments and the value of quasiparticle residue are used to establish the equations for the coefficients of the interpolation .
we test two fast techniques , the slave boson mean field and the hubbard i approximation to determine the coefficients .
the obtained self energies are compared with the results of numerically exact quantum monte carlo method .
we find that using the slave boson mean field approach we can construct an accurate self
energy for all frequencies via the proposed interpolation procedure . .
And you have already written the first three sentences of the full article: there has been recent progress in understanding physics of strongly correlated electronic systems and their electronic structure near a localization delocalization transition through the development of dynamical mean
field theory ( dmft ) @xcite . merging this computationally tractable many body technique with realistic local density
approximation ( lda ) @xcite based electronic structure calculations of strongly correlated solids is promising due to its simplicity and correctness in both band and atomic limits . at present , much effort is being made in this direction including the developments of a lda+dmft method anisimovkotliar , lda++ approach @xcite , combined gw and dmft theory @xcite as well as applications to various systems such as la@xmath0sr@xmath1tio@xmath2 @xcite , v@xmath3o@xmath2 @xcite , fe and ni licht , ce @xcite , pu @xcite , and many others . for a review , see ref . ..
Please generate the next two sentences of the article
|
the development of _ ab initio _ dmft scheme requires fast methods and algorithms to solve the anderson impurity model @xcite in general multiorbital case .
present techniques based on either non crossing approximation ( nca ) or iterative perturbation theory ( ipt ) are unable to provide the solution to that problem due to a limited number of regimes where these methods can be applied @xcite .
|
12,072 |
Suppose that you have an abstract for a scientific paper: a famous result by jeavons , cohen , and gyssens shows that every constraint satisfaction problem ( csp ) where the constraints are preserved by a _
semi - lattice operation _ can be solved in polynomial time .
this is one of the basic facts for the so - called _ universal - algebraic approach _ to a systematic theory of tractability and hardness in finite domain constraint satisfaction .
not surprisingly , the theorem of jeavons et al . fails for arbitrary infinite domain csps .
many csps of practical interest , though , and in particular those csps that are motivated by _ qualitative reasoning calculi _ from artificial intelligence , can be formulated with constraint languages that are rather well - behaved from a model - theoretic point of view . in particular , the automorphism group of these constraint languages tends to be _ large _ in the sense that the number of orbits of @xmath0-subsets of the automorphism group is bounded by some function in @xmath0 . in this paper
we present a generalization of the theorem by jeavons et al . to infinite domain csps where the number of orbits of @xmath0-subsets grows sub - exponentially in @xmath0 , and prove that preservation under a semi - lattice operation for such csps implies polynomial - time tractability . unlike the result of jeavons et al .
, this includes many csps that can not be solved by datalog .
= [ draw , circle , fill = black , text = white , minimum size=2pt , inner sep=0pt ] = [ -latex ] = [ -latex , dashed ] .
And you have already written the first three sentences of the full article: constraint satisfaction problems are fundamental computational problems that arise in many areas of theoretical computer science . in recent years
, a considerable amount of research has been concentrated on the classification of those constraint satisfaction problems that can be solved in polynomial time , and those that are computationally hard . in this paper
, we contribute to this line of research and generalize an important tractability condition from finite domain constraint satisfaction to a broad class of infinite domain constraint satisfaction problems ..
Please generate the next two sentences of the article
|
we work with the following definition of constraint satisfaction problems ( csps ) , which is well - adapted to treat csps over infinite as well as finite domains .
the definition is based on the concept of a _ homomorphism _ between relational structures , and equivalent to the standard definition for finite domain csps .
|
12,073 |
Suppose that you have an abstract for a scientific paper: minimal models of active brownian colloids consisting of self - propelled spherical particles with purely repulsive interactions have recently been identified as excellent quantitative testing grounds for theories of active matter and have been the subject of extensive numerical and analytical investigation .
these systems do not exhibit aligned or flocking states , but do have a rich phase diagram , forming active gases , liquids and solids with novel mechanical properties .
this article reviews recent advances in the understanding of such models , including the description of the active gas and its swim pressure , the motility - induced phase separation and the high - density crystalline and glassy behavior .
active matter , phase separation , active glasses , swim pressure .
And you have already written the first three sentences of the full article: living entities , on scales from birds to individual cells , organize in complex patterns with collective behaviors that serve important biological functions .
examples range from the flocking of birds @xcite to the sorting and organization of cells in morphogenesis @xcite .
work over the last ten years has shown that many aspects of this complex organization can be captured by physical models based on a minimal set of rules or interactions , leading to the emergence of the new field of active matter @xcite ..
Please generate the next two sentences of the article
|
this is defined as a distinct category of non - equilibrium matter in which energy uptake , dissipation and movement take place at the level of discrete microscopic constituents .
the active matter paradigm has additionally inspired the development of ingenious synthetic chemical and mechanical analogues , such as `` active '' colloids : micron - size spheres partly coated with a catalyst that promotes the decomposition of one of the components of the ambient fluid , resulting in self - propulsion of the colloidal particles @xcite .
|
12,074 |
Suppose that you have an abstract for a scientific paper: the latest ams-02 electron / positron precision data add to the spectrum knee as direct cosmic ray evidence for an electroweak scale strong interaction .
in addition , there is significant evidence for a strong self - interaction of dark matter .
qud is a unique massless su(5 ) field theory with an anomaly - generated bound - state s - matrix that could be an unconventional origin for the standard model .
the electroweak scale color sextet quark enhanced qcd interaction is the only new physics .
production of multiple vector bosons , that acquire masses via sextet quark pions , will give the ams positron and electron cross - sections - related vector boson pair production having been seen at the lhc .
stable sextet quark neutrons ( neusons ) provide a novel form of very strongly interacting dark matter that has the desired experimental properties .
large rapidity hadronic production of neusons will produce the knee .
-0.4 in 8.5 in 1=0.5 in -0.5 in plus 1000pt minus 1000pt # 1 # 1= to#1 to # 1 # 1 # 1 to 2 # 1 # 1 to 1 in # 1 # 1#2#1#2 # 1#2#3 2 # 1#2 # 3 # 1#1| # 1| # 1 # 1#1 # 1#2#1| .
# 2 # 1/ # 1| # 1| # 1#1 # 1 #
1#20=1=1>0.51-.500-.50-.5110>1 .50-.51 # 1#2 # 1#2 # 1 # 1\{. # 1 # 1=@xmath0= = # 1 # 1,by1 = 1 [ # 1]==,[#1]= # 1-#1- # 1(#1 ) # 1/#2 # 1@xmath0 # 1 # 1 # 1#2#3*#1 * , # 2 ( 19#3 ) # 1[#1 ] # 1 # 1 # 1 # 1(#1 ) ams-02 , strongly self - interacting dark matter , and qud alan r. white 0.6 cm argonne national laboratory 9700 south cass , il 60439 , usa . .
And you have already written the first three sentences of the full article: extension of the unprecedentedly accurate ams-02 data@xcite on positron and electron cross - sections to energies above the electroweak scale has major implications . before the publication of the data shown in fig .
1 , it was possible to argue@xcite that the positron content of cosmic rays is the consequence of galactic collisions of high energy primaries via established physics .
now , it is unarguably clear that a new phenomenon of some kind is necessarily involved ..
Please generate the next two sentences of the article
|
= 3.8 in = 2.7 in @xmath1 = 2.7 in figure 1 ams-02 data various proposals have been put forward but the simplest and most obvious explanation is that there is a new electroweak scale strong interaction , within the primary collisions , that plentifully produces positrons and electrons equally .
this explanation is a radical proposition within the current theory paradigm but the consequences are historic if what is seen is ( as i already suggested@xcite for the lower energy results ) the qcd interaction of the color sextet quark sector of the theory@xcite that i call qud . very significantly ,
|
12,075 |
Suppose that you have an abstract for a scientific paper: we present a new measure of entanglement for mixed states
. it can be approximately computable for every state and can be used to quantify all different types of multipartite entanglement .
we show that it satisfies the some of the usual properties of a good entanglement quantifier and derive relations between it and other entanglement measures . .
And you have already written the first three sentences of the full article: the quantification of entanglement in a multipartite quantum system is one of the most important and challenging topics of quantum information theory .
the first attempt of measuring entanglement was based on the violation of the so called bell s inequalities @xcite .
it was thought that the amount of non - classical correlations in a bipartite quantum system was intrinsically related to the level of violation of these family of inequalities ..
Please generate the next two sentences of the article
|
nonetheless , the generalization of such inequalities to multipartite states is not possible in general .
furthermore , it was already shown that , even for the bipartite case , the chsh ( clauser - horne - shimony - holt ) form of bell s inequalities does not constitute a good measure of quantum correlations in the sense that there are states which do not violate it , but can be purified by local operations and classical communication ( locc ) to a state which does @xcite .
|
12,076 |
Suppose that you have an abstract for a scientific paper: measurement techniques based upon the hall effect @xcite are invaluable tools in condensed matter physics . when an electric current flows perpendicular to a magnetic field , a hall voltage develops in the direction transverse to both the current and the field . in semiconductors ,
this behaviour is routinely used to measure the density and charge of the current carriers ( electrons in conduction bands or holes in valence bands ) internal properties of the system that are not accessible from measurements of the conventional resistance . for strongly interacting electron systems
, whose behaviour can be very different from the free electron gas , the hall effect s sensitivity to internal properties makes it a powerful tool ; indeed , the quantum hall effects @xcite are named after the tool by which they are most distinctly measured instead of the physics from which the phenomena originate . here
we report the first observation of a hall effect in an ultracold gas of neutral atoms , revealed by measuring a bose - einstein condensate s transport properties perpendicular to a synthetic magnetic field @xcite .
our observations in this vortex - free superfluid are in good agreement with hydrodynamic predictions @xcite , demonstrating that the system s global irrotationality influences this superfluid hall signal . and @xmath0 .
at the microscopic level ( right ) , the electrons move in curved paths under the influence of the magnetic field , and scatter from random impurities ( red crosses ) with a rate @xmath1 ( drude model ) .
* b , * the experiment used a 3d bec , flattened along @xmath2 and elongated along @xmath3 , trapped at the intersection of two 1064 nm laser beams ( pink ) .
a nearly uniform synthetic magnetic field @xmath4 ( green arrow ) was created via the combination of two raman laser beams ( red arrows ) counterpropagating along @xmath5 , and a magnetic field gradient along @xmath3 , making a vector potential @xmath6 .
* c , * we generated a current in the bec by....
And you have already written the first three sentences of the full article: in a 2deg , the equation of motion for the electrons is given by euler s equation @xcite @xmath112 where @xmath113 is the electrons mechanical momentum , @xmath11 their charge , @xmath38 the mean time between scattering events , @xmath114 the external potential energy , and @xmath115 the local pressure .
this hydrodynamic description involves the momentum distribution @xmath116 of the fluid s velocity field , rather than the momenta of individual particles , requiring the use of the convective derivative @xmath117 $ ] . for a noninteracting single - component 2deg
, the internal energy in an area @xmath118 is @xmath119 , where @xmath120 is the number of electrons and @xmath121 the fermi energy . from the energy ,.
Please generate the next two sentences of the article
|
the local pressure @xmath122 can be determined . because @xmath123 , the force due to the internal fermi pressure is proportional to the gradient of the density , and is ( coincidentally ) directly analogous to the effect of contact interactions in a bec .
the sfhd equations described in the text were derived from the time - dependent gross - pitaevskii equation ( gpe ) @xcite @xmath124 with the order parameter ( or wavefunction ) @xmath125 and inverse mass tensor @xmath126 ( which may in general be anisotropic ) . by writing the order parameter @xmath127 in terms of the density @xmath128 , the phase @xmath129 , and the vector potential @xmath130 ( where the integral is evaluated over the position of the particle @xmath131 ) , and neglecting the quantum pressure term @xcite , the gpe can be reformulated as the continuity and euler equations : @xmath132\label{eq : continuitymethods}\\ 0 = & \
|
12,077 |
Suppose that you have an abstract for a scientific paper: we report _ ab initio _ calculations of the dielectric function of six mono- and bilayer molybdenum dichalcogenides based in a bethe salpeter equation+g@xmath0w@xmath0 ( bse@g@xmath0w@xmath0)ansatz , focussing on the excitonic transitions dominating the absorption spectrum up to an excitation energy of 3.2ev .
our calculations suggest that switching chalcogen atoms and the strength of interlayer interactions should affect the detailed composition of the high c peaks in experimental optical spectra of molybdenum dichalcogenides and cause a significant spin - orbit - splitting of the contributing excitonic transitions in monolayer mose@xmath1 and mote@xmath1 .
this can be explained through changes in the electronic dispersion around the fermi energy along the chalcogen series s@xmath2se@xmath2te that move the van - hove singularities in the density of states of the two - dimensional materials along the _ @xmath3_-_k _ line in the brillouin zone .
further , we confirm the distinct interlayer character of the _c_ peak transition in few - layer mos@xmath1 that was predicted before from experimental data and show that a similar behaviour can be expected for mose@xmath1 and mote@xmath1 as well . .
And you have already written the first three sentences of the full article: the experimental realization of graphene in 2004@xcite opened the gates to a whole scientific field of quasi - twodimensional materials with the promise of novel applications and peculiar physical phenomena by virtue of their reduced dimensionality . among these ,
the transition metal dichalcogenides ( tmd ) of molybdenum and tungsten are an interesting addition due to their intrinsic semiconducting nature and high chemical stability both in bulk and few - layer phases .
analogously to graphite , these materials assume a hexagonal crystal structure with stacked layers of quasi - twodimensional atomic layers that are bound together through van - der - waals forces ..
Please generate the next two sentences of the article
|
the strong spin - orbit interaction and missing inversion symmetry in the monolayer materials cause a significant split of the valence band edge with an associated valley pseudospin and magnetic moment .
this gives rise to coupled spin- and valley physics in these materials@xcite that manifest , for instance , in optically induced spin and valley polarizations due to valley - dependent circular dichroism and a combination of the spin and valley hall effects .
|
12,078 |
Suppose that you have an abstract for a scientific paper: a rudimentary , one - zone , closed - box model for inhomogeneous chemical evolution is offered as an alternative reference than the simple model in the limit of no mixing .
the metallicity distribution functions ( mdfs ) of galactic halo and bulge stars can be matched by varying a _ single _ evolutionary parameter , @xmath0 .
@xmath1 is the filling factor of contaminating regions and @xmath2 is the number of star - forming generations .
therefore , _ q and n have equivalent roles _ , and combinations of @xmath2 and @xmath1 yield systems with different metallicities at any given age .
the model also revises interpretation of observed mdfs .
unevolved systems probe the parent distribution of metal production @xmath3 , for example , the high - metallicity tail of the halo distribution agrees with a power - law @xmath3 . #
1to 0pt#1 .
And you have already written the first three sentences of the full article: the relation between galactic star formation history and the interstellar medium ( ism ) is recorded in the distribution of elements we observe today .
the principal signatures are : ( a ) time - integrated metallicity distribution functions ( mdfs ) , as exhibited by long - lived stars ; ( b ) instantaneous mdfs at a given time , for example , the present - day dispersion in the inhomogeneous ism ; ( c ) abundance ratios of elements with varying origin and histories ; and ( d ) age - metallicity relations .
a unified understanding of these tracers is fundamental to solving the puzzle of galaxy assembly and evolution . over the 30 years of work on chemical evolution modeling ,.
Please generate the next two sentences of the article
|
the constraints offered by ( b ) , the instantaneous mdf , have been relatively neglected .
however , tinsley ( 1975 ) showed early on that chemical inhomogeneity significantly affects the other chemical signatures .
|
12,079 |
Suppose that you have an abstract for a scientific paper: 0.2 cm we discuss dynamical aspects of an asymmetric version of assisted diffusion of hard core particles on a ring studied by g. i. menon _ et al .
_ in j. stat phys .
* 86 * , 1237 ( 1997 ) .
the asymmetry brings in phenomena like kinematic waves and effects of the kardar - parisi - zhang nonlinearity , which combine with the feature of strongly broken ergodicity , a characteristic of the model .
a central role is played by a single nonlocal invariant , the irreducible string , whose interplay with the driven motion of reconstituting dimers , arising from the assisted hopping , determines the asymptotic dynamics and scaling regimes .
these are investigated both analytically and numerically through sector - dependent mappings to the asymmetric simple exclusion process . .
And you have already written the first three sentences of the full article: the issue of universality classes in nonequilibrium statistical systems is often linked to the existence of conservation laws [ ] . normally , the number of conservation laws is finite , leading to the occurrence of dynamically disjoint sectors whose number grows as a power of the system size . however , certain dynamical processes involving composite objects exhibit strongly broken ergodicity , with the number of disjoint sectors growing exponentially with system size , as a result of having an extensive number of conservation laws .
examples studied earlier include deposition and evaporation ( @xmath0 ) [ ] , and diffusion ( @xmath1 ) [ ] of bunches of particles .
if these moves are interpreted as involving trimers or dimers ( in general @xmath2-mers ) , then the @xmath2-mers in question do not keep their identity , and can reconstitute in time ..
Please generate the next two sentences of the article
|
the dynamical moves in these models do not connect configurations in different sectors , implying that the steady state is not unique and depends strongly on the initial condition .
moreover , the form of the long - time decay of time - dependent correlations in the steady state varies strongly from one sector to another . in one dimension , both the partitioning of phase space into many sectors and the accompanying dynamical diversity
|
12,080 |
Suppose that you have an abstract for a scientific paper: the study of the vassiliev invariants of legendrian knots was started by d. fuchs and s. tabachnikov who showed that the groups of @xmath0-valued vassiliev invariants of legendrian and of framed knots in the standard contact @xmath1 are canonically isomorphic .
recently we constructed the first examples where vassiliev invariants of legendrian and of framed knots are different , and vassiliev invariants of legendrian knots distinguish legendrian knots that are isotopic as framed knots and homotopic as legendrian immersions .
this raised the question what information about legendrian knots can be captured using vassiliev invariants . here
we answer this question by showing that for any contact @xmath2-manifold with a cooriented contact structure the groups of vassiliev invariants of legendrian knots and of knots that are nowhere tangent to a vector field that coorients the contact structure are canonically isomorphic . .
And you have already written the first three sentences of the full article: in this section we describe the main results of the paper .
( in case any of the terminology appears to be new to the reader , the corresponding definitions are given in the next section . )
if a contact structure on a @xmath2-manifold is cooriented , then every legendrian knot ( i.e. a knot that is everywhere tangent to the contact distribution ) has a natural framing ( a continuous normal vector field ) . hence when studying legendrian knots in such contact manifolds the main question is to distinguish those of them that realize isotopic framed knots . on the other hand a cooriented contact structure @xmath3 on a manifold @xmath4 gives rise to a nondegenerate vector field @xmath5 in @xmath6 that coorients the contact structure . clearly if two legendrian knots @xmath7 and @xmath8 are isotopic as legendrian knots , then they are also isotopic in the category of knots that are everywhere nontangent to @xmath5 ..
Please generate the next two sentences of the article
|
this observation leads to the following definition .
let @xmath9 be a contact manifold with a cooriented contact structure , and let @xmath5 be the nondegenerate vector field on @xmath6 that coorients the contact structure .
|
12,081 |
Suppose that you have an abstract for a scientific paper: an inflationary single field model with a non - trivial kinetic term for the inflaton is discussed .
it is shown that it is possible to have large primordial non - gaussianities and large tensor - to - scalar ratio in a simple concrete model with just a scalar field and a generalized kinetic term for the inflaton field .
this is potentially interesting in the prospect of new forthcoming observations . .
And you have already written the first three sentences of the full article: the inflationary phase of the early universe @xcite is a very important ingredient in modern cosmology .
the reason for this is twofold .
first , inflation solves the longstanding problems of standard hot big - bang cosmology , namely the horizon , flatness and monopole problems ..
Please generate the next two sentences of the article
|
furthermore , it produces the primordial perturbations for the structure that we observe today .
the recent spectacular cmb data from the wmap satellite @xcite have strengthen the inflationary idea , since the observations indicate an _ almost _ scale - free spectrum of gaussian adiabatic density fluctuations , just as predicted by simple models of inflation . in the prospect of future cmb experiments , like @xcite , constructing inflationary models which predict detectable primordial gravitational waves
|
12,082 |
Suppose that you have an abstract for a scientific paper: the two anomalous x - ray pulsars ( axps ) with well - sampled timing histories , 1e 1048.1@xmath05937 and 1e 2259@xmath1586 , are known to spin down irregularly , with ` bumps ' superimposed on an overall linear trend . here
we show that if axps are non - accreting magnetars , i.e. isolated neutron stars with surface magnetic fields @xmath2 , then they spin down electromagnetically in exactly the manner observed , due to an effect called ` radiative precession ' .
internal hydromagnetic stresses deform the star , creating a fractional difference @xmath3 between the principal moments of inertia @xmath4 and @xmath5 ; the resulting eulerian precession couples to an oscillating component of the electromagnetic torque associated with the near - zone radiation fields , and the star executes an anharmonic wobble with period @xmath6 , where @xmath7 is the rotation frequency as a function of time @xmath8 .
we solve euler s equations for a biaxial magnet rotating _ in vacuo _ ; show that the computed @xmath7 matches the measured timing histories of 1e 1048.1@xmath05937 and 1e 2259@xmath1586 ; predict @xmath7 for the next 20 years for both objects ; predict a statistical relation between @xmath9 and @xmath10 , to be tested as the population of known axps grows ; and hypothesize that radiative precession will be observed in future x - ray timing of soft gamma - ray repeaters ( sgrs ) . .
And you have already written the first three sentences of the full article: anomalous x - ray pulsars ( axps ) are a sub - class of x - ray pulsars distinguished by pulse periods lying in a narrow range between @xmath11 and @xmath12 , low x - ray luminosities , soft x - ray spectra , no detected optical counterparts , no detected orbital doppler shifts of pulse arrival times , and associations with shell - type supernova remnants ( mereghetti & stella 1995 ; van paradijs , taam & van den heuvel 1995 ) .
the nature of axps is uncertain ; possibilities include an accreting neutron star in a binary , with a low - mass white dwarf or he - burning star as a companion ( mereghetti & stella 1995 ; baykal & swank 1996 ; mereghetti , israel & stella 1998 ) , an isolated neutron star accreting from a residual disk following a phase of common - envelope evolution ( van paradijs et al .
1995 ; ghosh , angelini & white 1997 ) , a non - accreting massive white dwarf ( morini et al . 1988 ; paczyski 1990 ; usov 1994 ) , and a non - accreting magnetar ( thompson & duncan 1996 ; heyl & hernquist 1998 ; kouveliotou et al ..
Please generate the next two sentences of the article
|
1998 ) . the two axps with well - sampled timing histories , 1e 1048.1@xmath05937 and 1e 2259@xmath1586 ,
are observed to spin down irregularly : the rotation frequency @xmath13 of each object decreases linearly with time @xmath8 on average , but there are ` bumps ' superimposed on this average trend during which @xmath14 fluctuates by a factor of between two and five every five to ten years ( mereghetti 1995 ; baykal & swank 1996 ; baykal et al . 1998 ; oosterbroek et al . 1998 ; and references therein ) . in accreting - star models of axps
|
12,083 |
Suppose that you have an abstract for a scientific paper: in bafe@xmath0as@xmath0 , structural and magnetic planar defects begin to proliferate below the structural phase transition , affecting descriptions of magnetism and superconductivity .
we study using density - functional theory the stability and magnetic properties of competing antiphase and domain boundaries , twins and isolated @xmath1twins ( twin nuclei ) - spin excitations proposed and/or observed .
these nanoscale defects have very low surface energy ( @xmath2-@xmath3 @xmath4jm@xmath5 ) , with twins favorable to the mesoscale .
defects exhibit smaller moments confined near their boundaries making a uniform - moment picture inappropriate for long - range magnetic order in real samples .
_ nano_twins explain features in measured pair distribution functions , so should be considered when analyzing scattering data .
all these defects can be weakly mobile and/or have fluctuations that lower assessed `` ordered '' moments from longer spatial and/or time averaging , and should be considered directly . .
And you have already written the first three sentences of the full article: fe - based superconductors ( fescs ) provide another avenue to understand unconventional superconductivity.@xcite due to its ease of synthesis , bafe@xmath0as@xmath0 is a prototype for these systems , where its low - temperature ( t @xmath6 k ) ground state is a striped , antiferromagnetic ( afm ) orthorhombic ( @xmath7 ) structure,@xcite often called a spin - density wave ( sdw ) , and which is reproduced in density functional theory ( dft ) calculations.@xcite at nel t@xmath8 ( @xmath9 k ) , both a magnetic and structural transition occurs to a tetragonal ( @xmath10 ) paramagnet.@xcite by doping with a transition - metal on the fe - site or others on ba- and as - sites , superconductivity ( sc ) can be achieved , and similarly with pressure.@xcite there are strong connections between the magnetism and sc . dopants weaken the magnetic state and cooper pairing is , perhaps , driven by increased magnetic fluctuations out of the ground state.@xcite dft has proven successful in modeling the geometry , magnetic ordering , and electronic structure of fescs .
the magnetic ground states of lafeaso , bafe@xmath0as@xmath0 , nafeas , and fete are all correctly predicted.@xcite fermi - surface ( fs ) nesting is apparent from dft calculations and agrees with angle - resolved photoemission ( arpes ) , suggesting an itinerant nature@xcite and which is supported from the spin - wave dispersion.@xcite furthermore , dft explains quantitatively effects of doping on fs nesting , and why cu doping behaves differently than co and ni.@xcite k@xmath11fe@xmath0se@xmath0 ( isostructural to bafe@xmath0as@xmath0 ) does not have the hole pockets needed for fs nesting,@xcite as dft finds.@xcite dft results for bafe@xmath0as@xmath0 show a strong coupling between the structure and magnetism.@xcite planar defects , thus , have been proposed to explain key features in magnetic and transport properties of fescs near / below the structural transition .
mazin and johannes@xcite suggested a model in which low - energy magnetic anti -....
Please generate the next two sentences of the article
|
[ fig1 ] ) , which have yet to be tested .
so , are structural and magnetic planar defects energetically favorable and what are their properties ? to answer , we use dft to model potentially operative magnetic ( structural - induced ) defects , both isolated and extended , and explore their stability and properties by varying the structural parameters .
|
12,084 |
Suppose that you have an abstract for a scientific paper: among the unusual broad absorption line quasars being found by the sloan digital sky survey ( sdss ) are objects with much stronger absorption in feiii than feii .
these unusual line ratios require a high density in the outflow ( @xmath0 @xmath1 ) .
they should also appear for only a limited range of outflow column densities , which explains their rarity .
previously we suggested that the feiii line ratios were also affected by a resonance ; we now believe this is an artifact of structure in the underlying feii+feiii pseudocontinuum . the sdss is also discovering objects with absorption in rarely seen transitions such as hei .
vlt+uves high - resolution spectra of one such object , the mini - bal quasar sdss 1453 + 0029 , show that it has two hei absorption systems with considerably different properties separated by only 350 km s@xmath2 . .
And you have already written the first three sentences of the full article: broad absorption line ( bal ) quasars show absorption from gas with blueshifted outflow velocities of typically 0.1@xmath3 . about 10% of quasars exhibit bal troughs ,
usually attributed either to an orientation effect such that all quasars have bal outflows covering @xmath410% of the sky , or a phase of @xmath4100% covering lasting @xmath410% of the typical quasar lifetime .
understanding bal outflows is necessary since the bal outflow mass loss rates seem comparable to the accretion rates required to power quasars ..
Please generate the next two sentences of the article
|
unusual bal quasars delineate the full range of physical conditions and parameter space spanned by bal outflows .
the sloan digital sky survey ( york et al . 2000 ; www.sdss.org ) has discovered populations of unusual low - ionization broad absorption line quasars ( ` lobals ' ) , many of them ` felobals ' with absorption from excited feii or feiii ( hall et al . 2002 ) . one population of unusual bal quasars has unprecedented line ratios which are the reverse of those seen in previously known objects ; namely , lobals with stronger absorption in aliii than mgii and felobals with weak or no feii absorption but with feiii even stronger than mgii ( fig .
|
12,085 |
Suppose that you have an abstract for a scientific paper: we consider the problem of low rank matrix recovery in a stochastically noisy high dimensional setting .
we propose a new estimator for the low rank matrix , based on the iterative hard thresholding method , and that is computationally efficient and simple .
we prove that our estimator is optimal both in terms of the frobenius risk , and in terms of the operator norm risk , i.e. in terms of the entry - wise risk uniformly over any change of orthonormal basis .
this result allows us to provide the limiting distribution of the estimator . in the case where the design is gaussian
, we prove that the entry - wise bias of the limiting distribution of the estimator is small , which is of great interest for constructing tests and confidence sets for low dimensional subsets of entries of the low rank matrix . .
And you have already written the first three sentences of the full article: high - dimensional data have generated a great challenge in different fields of statistics , computer science , and machine learning . in order to consider cases where the number of covariates is larger than the sample size ,
new methodologies , applicable for the model under some structural constraints , have been developed .
for instance , there have been substantial works under the sparsity assumption including sparse linear regression , sparse covariance matrices estimation or sparse inverse covariance matrices estimation ( see e.g. * ? ? ? * ; * ? ? ? * ; * ? ? ? * ; * ? ? ? * ; * ? ? ? * ) . in this paper , we focus on the problem of _ low rank matrix recovery and uncertainty quantification_. there have been quite a few work on estimating low rank matrices in the matrix regression setting ( also named the trace regression setting , the matrix compressed sensing setting , or the quantum tomography setting when the parameter is a density matrix ) . many authors ( e.g. * ? ? ? * ; * ? ? ? * ; * ? ? ? * ; * ? ? ? * ) considered the exact recovery of a low - rank matrix based on a subset of uniformly sampled entries ..
Please generate the next two sentences of the article
|
also @xcite considered matrix recovery based on a small number of noisy linear measurements in the framework of restricted isometry property ( rip ) .
@xcite proved non - asymptotic bounds on the frobenius risk , and investigated matrix completion under a row / column weighted random sampling .
|
12,086 |
Suppose that you have an abstract for a scientific paper: we review observational constraints on the structures responsible for extreme scattering events , focussing on a series of observations of the quasar pks 1741@xmath0038 .
vla observations were conducted to search for changes in the rotation measure and absorption during the ese , while vlbi observations sought ese - induced changes in the source s image .
no rm changes were found implying @xmath1 mg , and no opacity changes were found implying @xmath2 .
no multiple imaging was observed , but the diameter of the source _ increased _ by 0.7 mas , contrary to what is predicted by simple refractive lens modeling of eses .
we summarize what these limits imply about the structure responsible for this . .
And you have already written the first three sentences of the full article: extreme scattering events ( ese ) are a class of dramatic decreases ( @xmath3 50% ) in the flux density of radio sources near 1 ghz for several weeks bracketed by substantial increases (; fig .
[ fig : lightcurve ] ) .
because of their simultaneity at different wavelengths and light travel time arguments , eses are likely a propagation effect @xcite ..
Please generate the next two sentences of the article
|
first identified toward extragalactic sources , eses have since been observed toward pulsars @xcite . to date , the only other observational constraints on the structures responsible for eses besides the light curves are the lack of pulse broadening and the variation in the pulse times of arrival during the pulsar eses .
this paper summarizes constraints obtained during the ese toward the quasar 1741@xmath0038 .
|
12,087 |
Suppose that you have an abstract for a scientific paper: the spectrum of partons in a qcd jet becomes independent of the primary energy in the low momentum limit .
this follows within the perturbative qcd from the colour coherence in soft gluon branching .
remarkably , the hadrons follow such behaviour closely , suggesting the parton hadron duality picture to be appropriate also for the low momentum particles .
more generally , this scaling property holds for particles of low transverse and arbitrary longitudinal momentum , which explains an old experimental observation ( `` fan invariance '' ) . further tests of the perturbatively based picture for soft particle production are proposed for three - jet events in annihilation and di - jet production events in @xmath0 , @xmath1 and @xmath2 collisions .
they are based upon the difference in the intensity of the soft radiation from primary @xmath3 and @xmath4 antennae . * perturbative universality in soft particle production * valery a. khoze @xmath5 , sergio lupia @xmath6 , wolfgang ochs @xmath6 @xmath7 _ infn - laboratori nazionali di frascati , p.o .
box 13 , + i-00044 frascati , italy _
+ + @xmath8 _ th division cern + ch-1211 , geneva 23 _
+ + @xmath9 _ max - planck - institut fr physik + ( werner - heisenberg - institut ) + fhringer ring 6 , d-80805 munich , germany _ .
And you have already written the first three sentences of the full article: the study of multiparticle production in hard processes provides one with an important information about both the qcd partonic branching processes and the transition from the coloured partons to the colourless hadrons .
the vast amount of experimental data collected in various hard collisions processes convincingly confirms that the inclusive characteristics of qcd jet systems can be successfully described within the analytical perturbative approach to multiparticle production , see e.g. @xcite .
this approach is based on the so - called modified leading logarithmic approximation ( mlla ) @xcite and on the concept of local parton hadron duality ( lphd ) @xcite ..
Please generate the next two sentences of the article
|
in particular , the experiment clearly demonstrates that the bright colour coherence effects survive the hadronization stage and are distinctively visible in the data .
this has been known for quite a long time for annihilation processes ( see e.g. @xcite ) . recently the very impressive data from hera @xcite and from the tevatron @xcite have become available .
|
12,088 |
Suppose that you have an abstract for a scientific paper: we present some results of monte carlo simulations for the deposition of particles of different sizes on a two - dimensional substrate .
the particles are linear , height one , and can be deposited randomly only in the two , @xmath0 and @xmath1 directions of the substrate , and occupy an integer number of cells of the lattice .
we show there are three different regimes for the temporal evolution of the interface width . at the initial times
we observe an uncorrelated growth , with an exponent @xmath2 characteristic of the random deposition model . at intermediate times
, the interface width presents an unusual behavior , described by a growing exponent @xmath3 , which depends on the size of the particles added to the substrate . if the linear size of the particle is two we have @xmath4 , otherwise we have @xmath5 , for all other particle sizes . after a long time the growth reaches the saturation regime where the interface width becomes constant and is described by the roughness exponent @xmath6 , which is nearly independent of the size of the particle .
similar results are found in the surface growth due to the electrophoretic deposition of polymer chains .
contrary to one - dimensional results the growth exponents are non - universal . .
And you have already written the first three sentences of the full article: the formation of structures due to the deposition of particles is a topic of growing interest , and has challenged theoretical and experimental researchers in the field of material physics @xcite . from the experimental point of view there is a real possibility of developing thin film devices with important technological applications and , at the same time , the theoretical physicists can apply the tools well known in the realm of statistical equilibrium physics to describe these new nonequilibrium phenomena .
it is well established that some characteristics of the growing surfaces present scale - invariant properties , so that quite different growing processes exhibit very similar scaling behavior , which we believe is universal .
the temporal evolution of a surface formed by the deposition of particles is usually described in terms of some scale exponents ..
Please generate the next two sentences of the article
|
these scaling exponents define the most fundamental characteristics of the growth processes , so that we can put into the same universality class many different processes that have the same values of the scaling exponents .
in this work we are interested in the description of the morphology of a surface formed by adding particles to an initially flat two - dimensional substrate .
|
12,089 |
Suppose that you have an abstract for a scientific paper: the effect of the shape of six different periodic forces and second periodic forces on the onset of horseshoe chaos are studied both analytically and numerically in a duffing oscillator .
the external periodic forces considered are sine wave , square wave , symmetric saw - tooth wave , asymmetric saw - tooth wave , rectified sine wave , and modulus of sine wave .
an analytical threshold condition for the onset of horseshoe chaos is obtained in the duffing oscillator driven by various periodic forces using the melnikov method .
melnikov threshold curve is drawn in a parameter space .
for all the forces except modulus of sine wave , the onset of cross - well asymptotic chaos is observed just above the melnikov threshold curve for onset of horseshoe chaos . for the modulus of sine wave long time transient motion followed by a periodic attractor
is realized .
the possibility of controlling of horseshoe and asymptotic chaos in the duffing oscillator by an addition of second periodic force is then analyzed .
parametric regimes where suppression of horseshoe chaos occurs are predicted .
analytical prediction is demonstrated through direct numerical simulations .
starting from asymptotic chaos we show the recovery of periodic motion for a range of values of amplitude and phase of the second periodic force .
interestingly , suppression of chaos is found in the parametric regimes where the melnikov function does not change sign . , , , duffing oscillator , melnikov method , horseshoe chaos , asymptotic chaos . 05.45.+b .
And you have already written the first three sentences of the full article: the dynamics of nonlinear oscillators and circuits are very often studied with external force being of the form @xmath0 or @xmath1 .
other forms of forces such as square wave , rectified sine wave , rectangular wave , etc . can be generated and applied to dynamical systems .
the study of the effect of such periodic forces will be helpful to choose a suitable external drive in creating and controlling nonlinear behaviours . in recent years.
Please generate the next two sentences of the article
|
there are reports on the effect of different forces on certain nonlinear phenomena @xcite .
analysis of features of a particular dynamics with various periodic forces and a detailed comparative study of effects induced by them will be of great use .
|
12,090 |
Suppose that you have an abstract for a scientific paper: we report the design and implementation of a call - graph profiler for gnu octave , a numerical computing platform .
gnu octave simplifies matrix computation for use in modeling or simulation .
our work provides a call - graph profiler , which is an improvement on the flat profiler .
we elaborate design constraints of building a profiler for numerical computation , and benchmark the profiler by comparing it to the rudimentary timer start - stop ( tic - toc ) measurements , for a similar set of programs .
the profiler code provides clean interfaces to internals of gnu octave , for other ( newer ) profiling tools on gnu octave . .
And you have already written the first three sentences of the full article: gnu octave is a numerical computing platform based on programming with matrices as a fundamental construct .
several modeling and simulation research work benefit through the reduced time and complexity offered by matrix programming environments .
modeling and simulation applications when developed through exploratory analysis , or initial speculative analysis of parameters , optimization in not the key goal ..
Please generate the next two sentences of the article
|
however , once a stable model is created , running parametric search over a large search space requires the creation of optimized models . optimizing computational models written in matrix languages , for time and space usage , help to directly speed up the search process by reducing time and resources ( memory , diskspace ) .
there are many ways of optimizing program performance , like tracing , logging , and profiling .
|
12,091 |
Suppose that you have an abstract for a scientific paper: over two hundred years ago capt .
james cook sailed up whitsunday passage , just a few miles where we now sit , on a voyage of astronomical observation and discovery that remains an inspiration to us all .
since the prospects of our visiting planets beyond our solar system are slim , we will have to content ourselves with searching for life using remote sensing , not sailing ships .
fortunately , a recently completed nasa study has concluded that a terrestrial planet finder could be launched within a decade to detect terrestrial planets around nearby stars . a visible light coronagraph using an 8 - 10 m telescope , or an infrared nulling interferometer , operated on either a @xmath0 m structure or separated spacecraft , could survey over 150 stars , looking for habitable planets and signs of primitive life .
such a mission , complemented by projects ( kepler and eddington ) that will provide statistical information on the frequency of earth - sized planets in the habitable zone , will determine key terms in the `` drake equation '' that describes the number of intelligent civilizations in the universe .
# 1_#1 _ # 1_#1 _ = # 1 1.25 in .125 in .25 in epsf .
And you have already written the first three sentences of the full article: this conference takes place in the whitsunday group of islands discovered on whitsunday ( june 3 ) , 1770 , by the english explorer , capt .
james cook .
surprisingly , the stated goal of cook s voyage was astronomical in nature ..
Please generate the next two sentences of the article
|
as described in richard hough s excellent biography ( 1997 ) of capt .
cook , the story has echoes in today s searches for other worlds .
|
12,092 |
Suppose that you have an abstract for a scientific paper: the formalism of kohn and sham uses a specific ( model ) hamiltonian which highly simplifies the many - electron problem to that of noninteracting fermions .
the theorem of hohenberg and kohn tells us that , for a given ground state density , this hamiltonian is unique . in principle , this density can be chosen as that of the real , interacting system . to obtain the energy , or other properties of the real system ,
approximations are needed . working with non interacting fermions
is an important simplification , but it may be easier to produce approximations with different choices of the model hamiltonian . the feature that the exact density is ( ideally ) reproduced can be kept in the newly defined fictitious systems . using model hamiltonians having the same form as the physical one ,
that is , being built of one- and two - body operators , allows to approach the physical hamiltonian arbitrarily close , and thus a systematic reduction of the approximations . .
And you have already written the first three sentences of the full article: the knowledge from first principles of the electronic structure of atoms , molecules and solids is contained in the @xmath0-electron schrdinger equation that , within the born - oppenheimer approximation ( i.e. , at fixed nuclei positions @xmath1 ) , reads ( _ 1, ... ,_n)(_1_1, ... ,_n_n)= e(_1_1, ...
,_n_n ) , [ eq_schro ] with @xmath2 where @xmath3 is the external potential due to the @xmath4 nuclei of charges @xmath5 at positions @xmath6 , and hartree atomic units , @xmath7 ( reduced planck s constant ) @xmath8 ( electron mass ) , @xmath9 ( bohr radius ) , @xmath10 ( electron charge ) , have been used .
since electrons obey the fermi - dirac statistics , @xmath11 must be antisymmetric under particle exchange , @xmath12 , where @xmath13 denotes the three - dimensional electronic position and @xmath14 the spin degree of freedom ( @xmath15 or @xmath16 ) . in what follows.
Please generate the next two sentences of the article
|
we will be only concerned with the search for the ground - state energy , i.e. , the lowest eigenvalue @xmath17 of eq .
( [ eq_schro ] ) .
|
12,093 |
Suppose that you have an abstract for a scientific paper: we analyze the behavior of interacting fermions near a ferromagnetic stoner instability .
we show that the landau damping of the spin susceptibility is a relevant perturbation near a ferromagnetic quantum - critical point ( fqcp ) .
we argue that , as the system approaches a fqcp , the fermionic self - energy crosses over from predominantly momentum dependent away from the transition to predominantly frequency dependent in the immediate vicinity of the transition .
we argue that due to this self - generated locality , the quasiparticle effective mass does not diverge before a fqcp is reached . .
And you have already written the first three sentences of the full article: over 50 years , fermi liquid theory serves as the basis for our understanding of the behavior of electrons in metals @xcite .
developed by landau to describe the behavior of @xmath0 at low @xmath1 @xcite and based on a minimal number of postulates , it allows to describe the behavior of interacting fermions not only qualitatively , but also quantitatively ( see e.g. , @xcite ) .
the key postulate of fermi liquid theory is that the interaction between fermions with energies near the fermi energy is weak in any fermi liquid , and does not qualitatively change the structure of low - energy fermionic states compared to a fermi gas . in the green s function language.
Please generate the next two sentences of the article
|
, the condition of weak scattering near the fermi surface implies that the fermionic self - energy @xmath2 is linear in @xmath3 and in @xmath4 at smallest frequencies and smallest @xmath5 . in particular , at @xmath6 ,
@xmath7 the imaginary part of @xmath8 , responsible for the scattering from one electronic state into the other , and hence , for a finite lifetime of a given fermionic state , must be smaller than @xmath3 , i.e. , should behave at low frequencies as @xmath9 the conditions specified by ( [ 1 ] ) and ( [ 2 ] ) imply that at low energies , the dominant effect of electron - electron interaction is the shift of the energy levels , proportional to the deviation of the energy level from the fermi surface . at the same time , the levels themselves remain intact , i.e. , they are not destroyed by the interaction .
|
12,094 |
Suppose that you have an abstract for a scientific paper: we analyzed effects of elasticity on the dynamics of fluids in porous media by studying a flow of a maxwell fluid in a tube , which oscillates longitudinally and is subject to oscillatory pressure gradient .
the present study investigates novelties brought about into the classic biot s theory of propagation of elastic waves in a fluid - saturated porous solid by inclusion of non - newtonian effects that are important , for example , for hydrocarbons . using the time fourier transform and transforming the problem into the frequency domain
, we calculated : ( a ) the dynamic permeability and ( b ) the function @xmath0 that measures the deviation from poiseuille flow friction as a function of frequency parameter @xmath1 .
this provides a more complete theory of flow of maxwell fluid through the longitudinally oscillating cylindrical tube with the oscillating pressure gradient , which has important practical applications .
this study has clearly shown transition from dissipative to elastic regime in which sharp enhancements ( resonances ) of the flow are found . .
And you have already written the first three sentences of the full article: a quantitative theory of propagation of elastic waves in a fluid - saturated porous solid was formulated in the classic papers by biot [ 1 ] .
one of the major findings of biot s work was that there was a breakdown in poisseuille flow above a certain characteristic frequency specific to the fluid - saturated porous material .
biot theoretically studied this phenomenon by considering the flow of a viscous fluid in a tube with longitudinally oscillating walls under an oscillatory pressure gradient ..
Please generate the next two sentences of the article
|
apart from the fundamental interest , the investigation of the dynamics of fluid in porous media under oscillatory pressure gradient and oscillating pore walls is of prime importance for the recently emerged technology of acoustic stimulation of oil reservoirs [ 2 ] .
for example , it is known that the natural pressure in an oil reservoir generally yields no more than approximately 10 percent oil recovery .
|
12,095 |
Suppose that you have an abstract for a scientific paper: recent advances in understanding of the basic properties of compressible magnetohydrodynamic ( mhd ) turbulence call for revisions of some of the generally accepted concepts . first , mhd turbulence is not so messy as it is usually believed .
in fact , the notion of strong non - linear coupling of compressible and incompressible motions is not tenable .
alfven , slow and fast modes of mhd turbulence follow their own cascades and exhibit degrees of anisotropy consistent with theoretical expectations .
second , the fast decay of turbulence is not related to the compressibility of fluid . rates of decay of compressible and incompressible motions are very similar .
third , viscosity by neutrals does not suppress mhd turbulence in a partially ionized gas .
instead , mhd turbulence develops magnetic cascade at scales below the scale at which neutrals damp ordinary hydrodynamic motions .
the implications of those changes of mhd turbulence paradigm for molecular clouds require further studies .
those studies can benefit from testing of theoretical predictions using new statistical techniques that utilize spectroscopic data .
we briefly discuss advances in development of tools using which the statistics of turbulent velocity can be recovered from observations . .
And you have already written the first three sentences of the full article: it is well known that molecular clouds are magnetized with compressible magnetic turbulence determining most of their properties ( see elmegreen & falgarone 1996 , stutzki 2001 ) .
star formation ( see mckee & tan 2002 , elmegreen 2002 , pudritz 2001 ) , cloud chemistry ( see falgarone 1999 and references therein ) , shattering and coagulation of dust ( see lazarian & yan 2003 and references therein ) are examples of processes for which knowledge of turbulence is absolutely essential .
there are many excellent reviews that deal the theory of turbulent molecular clouds and numerical simulations ( see falgarone 1999 , vazquez - semadeni et al ..
Please generate the next two sentences of the article
|
2000 , mac low & klessen 2003 ) .
this _ short _ review is focused on the recently uncovered basic properties of mhd turbulence and their implications for understanding of molecular clouds .
|
12,096 |
Suppose that you have an abstract for a scientific paper: we study the @xmath0 theory of gravity using metric approach .
in particular we investigate the recently proposed model by hu - sawicki , appleby @xmath1 battye and starobinsky . in this model ,
the cosmological constant is zero in flat space time .
the model passes both the solar system and the laboratory tests .
but the model parameters need to be fine tuned to avoid the finite time singularity recently pointed in the literature .
we check the concordance of this model with the @xmath2 and baryon acoustic oscillation data .
we find that the model resembles the @xmath3cdm at high redshift .
however , for some parameter values there are variations in the expansion history of the universe at low redshift . .
And you have already written the first three sentences of the full article: 0.5 cm it is remarkable that different data sets of complementary nature such as supernovae , baryon oscillations , galaxy clustering , microwave back ground and weak lensing all taken together strongly support the late time acceleration of universe . in the standard lore , one assumes that the history of universe is described by the general relativity ( gr ) .
the late time acceleration can easily be captured in this frame work by introducing a scalar field with large negative pressure known as _ dark energy _ @xcite . in view of the fine tuning problem ,
the scalar field models , specially those with tracker like solutions , are more attractive compared to the models based on cosmological constant . at present , observations are not in a position to reject or to establish the dark energy metamorphosis . a host of scalar field models have been investigated in the literature ..
Please generate the next two sentences of the article
|
the scalar field models can fit the data but lack the predictive power .
it then becomes important to seek the support of these models from a fundamental theory of high energy physics .
|
12,097 |
Suppose that you have an abstract for a scientific paper: an edge - coloring of a graph @xmath0 with colors @xmath1 is called an interval @xmath2-coloring if for each @xmath3 there is at least one edge of @xmath0 colored by @xmath4 , and the colors of edges incident to any vertex of @xmath0 are distinct and form an interval of integers . in this paper
we prove that if a connected graph @xmath0 with @xmath5 vertices admits an interval @xmath2-coloring , then @xmath6 . we also show that if @xmath0 is a connected @xmath7-regular graph with @xmath5 vertices has an interval @xmath2-coloring and @xmath8 , then this upper bound can be improved to @xmath9
. + keywords : edge - coloring , interval coloring , bipartite graph , regular graph .
And you have already written the first three sentences of the full article: all graphs considered in this paper are finite , undirected , and have no loops or multiple edges .
let @xmath10 and @xmath11 denote the sets of vertices and edges of @xmath0 , respectively .
an @xmath12-biregular bipartite graph @xmath0 is a bipartite graph @xmath0 with the vertices in one part all having degree @xmath13 and the vertices in the other part all having degree @xmath14 ..
Please generate the next two sentences of the article
|
a partial edge - coloring of @xmath0 is a coloring of some of the edges of @xmath0 such that no two adjacent edges receive the same color .
if @xmath15 is a partial edge - coloring of @xmath0 and @xmath16 , then @xmath17 denotes the set of colors of colored edges incident to @xmath18 .
|
12,098 |
Suppose that you have an abstract for a scientific paper: we report the discovery of the narrow - line seyfert 1 galaxy mkn 335 in an extremely low x - ray state . a comparison of _ swift _ observations obtained in may and june / july 2007 with all previous x - ray observations between 1971 to 2006 show the agn to have diminished in flux by a factor of more than 30 , the lowest x - ray flux mkn 335 has ever been observed in .
the _
swift_observations show an extremely hard x - ray spectrum at energies above 2 kev .
possible interpretations include partial covering absorption or x - ray reflection from the disk . in this letter
we consider the partial covering interpretation .
the _ swift _
observations can be well fit by a strong partial covering absorber with varying absorption column density ( @xmath0 @xmath1 ) and a covering fraction @xmath2=0.9 - 1 .
when corrected for intrinsic absorption , the x - ray flux of mkn 335 varies by only factors of 4 - 6 . in the uv mkn 335
shows variability in the order of 0.2 mag .
we discuss the similarity of mkn 335 with the highly variable nls1 wpvs007 , and speculate about a possible link between nls1 galaxies and broad - absorption line quasars . .
And you have already written the first three sentences of the full article: since the mid 1980s narrow - line seyfert 1 galaxies ( nls1s ; * ? ? ?
* ) have become a field of extensive study in agn science .
nls1s are crucial for our understanding of the agn phenomenon , because they are most likely agn at an early stage ( e.g. * ? ? ?.
Please generate the next two sentences of the article
|
they possess relatively low - mass black holes and high eddington ratios @xmath4 .
nls1s are characterized by extreme properties , such as steep soft and hard x - ray spectra , strong x - ray variability , and strong optical fe ii emission ( e.g. * ? ? ?
|
12,099 |
Suppose that you have an abstract for a scientific paper: we show that the dual of the cone of divisors on a complete @xmath0-factorial toric variety @xmath1 whose stable base loci have dimension less than @xmath2 is generated by curves on small modifications of @xmath1 that move in families sweeping out the birational transforms of @xmath2-dimensional subvarieties of @xmath1 .
we give an example showing that it does not suffice to consider curves on @xmath1 itself . .
And you have already written the first three sentences of the full article: let @xmath1 be a smooth @xmath3-dimensional complex projective variety .
boucksom , demailly , paun , and peternell have recently shown that the dual of the cone of numerical classes of effective divisors on @xmath1 is the closure of the cone of numerical classes of movable curves ( * ? ? ?
* theorem 0.2 ) ; see also @xcite ..
Please generate the next two sentences of the article
|
their theorem is analogous to a theorem of kleiman that says that the dual of the cone of numerical classes of ample divisors is the closure of the cone of numerical classes of effective curves @xcite .
debarre and lazarsfeld asked whether these results might generalize in the following way : for @xmath4 , is the dual of the cone of numerical classes of divisors on @xmath1 whose stable base locus has dimension less than @xmath2 generated by the numerical class of a natural collection of curves , such as curves moving in a family that sweeps out a subvariety of dimension @xmath2 ? this paper gives an affirmative answer to their question in the toric case , with a slight twist the curves that one must consider include not only curves on @xmath1 , but also curves on small modifications of @xmath1 .
|
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.