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10,000 |
Suppose that you have an abstract for a scientific paper: methods of calculation of loop diagrams in heavy quark effective theory ( hqet ) are presented . .
And you have already written the first three sentences of the full article: @xmath0 meson is the hydrogen atom of quantum chromodynamics ( qcd ) , its simplest nontrivial object . in the leading approximation
, the @xmath1 quark in it just seats at rest at the origin and creates chromoelectric field .
light constituents ( gluons , light quarks and antiquarks ) move in this external field ..
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their motion is relativistic ; the number of gluons and light quark - antiquark pairs in this light cloud is undetermined and varying .
therefore , there are no reasons to expect that a nonrelativistic potential quark model describes @xmath0 meson well .
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10,001 |
Suppose that you have an abstract for a scientific paper: in a recent paper , kuperberg described the first subexponential time algorithm for solving the dihedral hidden subgroup problem .
the space requirement of his algorithm is super - polynomial .
we describe a modified algorithm whose running time is still subexponential and whose space requirement is only polynomial . .
And you have already written the first three sentences of the full article: a central problem in quantum computation is the hidden subgroup problem ( hsp ) . here , we are given a black box that computes a function on elements of a group @xmath0 .
the function is known to be constant and distinct on left cosets of a subgroup @xmath1 and our goal is to find @xmath2 .
interestingly , most known quantum algorithms that provide a super - polynomial advantage over classical algorithms solve special cases of the hsp on abelian groups ..
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there has also been considerable interest in the hsp on noncommutative groups ( see , e.g. , @xcite ) .
for example , one important group is the symmetric group : it is known that solving the hsp on the symmetric group leads to a solution to graph isomorphism @xcite . in this paper
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10,002 |
Suppose that you have an abstract for a scientific paper: we study gravitational instabilities in disks , with special attention to the most massive clumps that form because they are expected to be the progenitors of globular - type clusters .
the maximum unstable mass is set by rotation and depends only on the surface density and orbital frequency of the disk .
we propose that the formation of massive clusters is related to this largest scale in galaxies not stabilized by rotation .
using data from the literature , we predict that globular - like clusters can form in nuclear starburst disks and protogalactic disks but not in typical spiral galaxies , in agreement with observations . .
And you have already written the first three sentences of the full article: the study of instabilities in disks has a long history , following the seminal work of toomre ( 1964 ) , with a considerable literature on many aspects of it .
however , relatively little attention has been given to the most massive agglomerations that can form by the fragmentation of galactic gas disks .
these most massive agglomerations are of interest because they may be the precursors of the most massive star clusters known , the globular clusters ..
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globular clusters were until recently viewed as exclusively old objects , and cluster formation models were therefore based on ideas about early stages of galaxy formation .
this view changed with the realization that elliptical galaxies often contain two populations of globular clusters that appear to have different origins , suggested to be a ` primordial ' population and a ` merger ' population ( ashman & zepf 1992 ) .
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10,003 |
Suppose that you have an abstract for a scientific paper: motivated by the recent efforts in creating flat bands in ultracold atomic systems , we investigate how to probe a flat band in an optically trapped spin - orbital - coupled bose - einstein condensate using bragg spectroscopy .
we find that the excitation spectrum and the dynamic structure factor of the condensate are dramatically altered when the band structure exhibits various levels of flatness .
in particular , when the band exhibits perfect flatness around the band minima corresponding to a near - infinite effective mass , a quadratic dispersion emerges in the low - energy excitation spectrum ; in sharp contrast , for the opposite case when an ordinary band is present , the familiar linear dispersion arises .
such linear - to - quadratic crossover in the low - energy spectrum presents a striking manifestation of the transition of an ordinary band into a flat band , thereby allowing a direct probe of the flat band by using bragg spectroscopy . .
And you have already written the first three sentences of the full article: there have been intensive efforts in realizing flat bands in various context of condensed - matter @xcite and atomic physics @xcite .
the motivation behind this search is twofold .
first , a flat band , whose kinetic energy is highly quenched compared to the scale of interactions , possesses macroscopic level degeneracy , and as a result , interactions play a dominant role in affecting the system that has given rise to many interesting quantum phases @xcite ..
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second , even more challenging is to create topological flat bands with nonzero chern number @xcite , which can open a new avenue for engineering a fractional topological quantum insulator @xcite without landau levels prompted by the analogy to landau levels @xcite in condensed matter physics .
motivated by the ongoing interests in creating flat bands in ultracold atomic systems@xcite , we address below the problem of how to probe an arising isolated flat band in an optically trapped spin - orbital - coupled ( soc ) bose - einstein condensate ( bec ) @xcite by using bragg spectroscopy .
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10,004 |
Suppose that you have an abstract for a scientific paper: we discuss ground state factorization schemes in spin @xmath0 arrays with general quadratic couplings under general magnetic fields , not necessarily uniform or transverse .
it is shown that given arbitrary spin alignment directions at each site , nonzero @xmath1 couplings between any pair and fields at each site always exist such that the ensuing hamiltonian has an exactly separable eigenstate with the spins pointing along the specified directions .
furthermore , by suitable tuning of the fields this eigenstate can always be cooled down to a nondegenerate ground state .
it is also shown that in open one - dimensional systems with fixed arbitrary first neighbor couplings , at least one separable eigenstate compatible with an arbitrarily chosen spin direction at one site is always feasible if the fields at each site can be tuned .
we demonstrate as well that in the vicinity of factorization , i.e. , for small perturbations in the fields or couplings , pairwise entanglement reaches full range .
some noticeable examples of factorized eigenstates are unveiled .
the present results open the way for separable ground state engineering . a notation to quantify the complexity of a given type of solution according to the required control on the system couplings and fields
is introduced . .
And you have already written the first three sentences of the full article: over the last two decades quantum information and quantum computation sciences have experienced an extraordinary theoretical and experimental progress @xcite . in particular , the possibility of performing quantum information processing and quantum simulation tasks in archetypal many - body systems such as spin arrays has attracted considerable attention @xcite .
furthermore , the recent noticeable advances in control techniques of quantum systems have made it possible to engineer and simulate spin interactions by means of cold atoms in optical lattices @xcite , superconducting josephson junctions @xcite or trapped ions @xcite , leading to an ever increasing interest in these strongly correlated systems . in this framework
, it is well known that the exact eigenstates of interacting spin systems in the presence of an external magnetic field are typically entangled states ..
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however , one of the most exceptional features of these systems is that under certain conditions they can posses a completely separable ground state ( gs ) , i.e. , a _
factorized _ gs which can be expressed as the product of single spin states @xcite .
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10,005 |
Suppose that you have an abstract for a scientific paper: we consider one of the quantum key distribution protocols recently introduced in ref .
[ pirandola et al . ,
nature physics * 4 * , 726 ( 2008 ) ] .
this protocol consists in a two - way quantum communication between alice and bob , where alice encodes secret information via a random phase - space displacement of a coherent state .
in particular , we study its security against a specific class of individual attacks which are based on combinations of gaussian quantum cloning machines . .
And you have already written the first three sentences of the full article: recently @xcite , we have shown how two - way quantum communication can profitably be exploited to enhance the security of continuous variable quantum key distribution @xcite . in particular , we have investigated the security of two - way protocols in the presence of collective gaussian attacks which are modelled by combinations of entangling cloners @xcite . even though this situation is the most important one from the point view of the practical implementation , the effect of other kind of gaussian attacks ( i.e. , not referable to entangling cloners ) must also be analyzed . in this paper , we study the security of the two - way coherent - state protocol of ref .
@xcite against individual attacks where an eavesdropper ( eve ) combines two different gaussian quantum cloning machines ( also called _ gaussian cloners _ ) .
in particular , we are able to show the robustness of the two - way protocol when the first cloner is fixed to be symmetric in the output clones ..
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this symmetry condition enables us to derive the results quite easily but clearly restricts our security analysis to a preliminary stage .
for this reason , the _ optimal _ performance of gaussian cloners against two - way quantum cryptography is still unknown at the present stage .
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10,006 |
Suppose that you have an abstract for a scientific paper: it is still an outstanding challenge to characterize and understand the topological features of strongly correlated states such as bound - states in interacting quantum systems . here ,
from the cotranslational symmetry in an interacting multi - particle quantum system , we develop a general method to construct an intrinsic chern invariant for identifying strongly correlated topological states . as an example , we study the topological magnons in a strongly interacting two - dimensional spinor hofstadter model , which can be realized by the currently experimental techniques [ phys . rev . lett .
* 111 * , 185301 ( 2013 ) ; phys .
rev .
lett . * 111 * , 185302 ( 2013 ) ] . through calculating the two - magnon excitation spectrum and the intrinsic chern number
, we explore the emergence of topological edge bound - states and give their topological phase diagram .
we also analytically derive an effective single - particle hofsdadter superlattice model for understanding the topological bound - states .
our results not only provide a new approach to defining topological invariants , but also give deep insights into the characterization and understanding of strongly correlated topological states .
topological invariants , which describe the invariant property of a topological space under homeomorphisms , are of great importance in characterizing topological matters and topological phase transitions . weakly interacting topological states , whose universal properties
do not depend on inter - particle interactions , are well - understood due to the well - developed tools for treating weakly interacting systems @xcite .
however , strongly interacting topological states , whose universal properties are determined by inter - particle interactions , pose much greater challenges to both theory @xcite and experiment @xcite .
the characterization of strongly interacting topological states is quite different from that of the weakly interacting counterparts @xcite . due to the existence of strong....
And you have already written the first three sentences of the full article: in this section , we give a detailed derivation of the interacting spinor hofstadter model . based upon the approach for treating noninteracting spinless bosons @xcite , we generalize it to deal with interacting two - component bosons .
we consider an ultracold two - component bose gas confined in a two - dimensional optical lattice potential , @xmath168 with @xmath169 and @xmath170 . here ,
@xmath171 and @xmath172 are respectively the wavelength and lattice depth along @xmath173-direction ( where @xmath174 and @xmath49 ) . a gradient magnetic field along @xmath48-direction.
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is used to generate a spin - dependent linear potential , @xmath175 with the amplitude @xmath176 . given the bare coupling along @xmath48-direction @xmath177 , when @xmath178 , the tunneling along @xmath48-direction is inhibited and can be restored by a pair of far - detuned running - wave beams , @xmath179 with @xmath180 and @xmath181 , see fig .
[ figs_exp_setup ] .
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10,007 |
Suppose that you have an abstract for a scientific paper: a method is presented for the calculation of the one - body ( 1 dm ) and two - body ( 2 dm ) density matrices and their fourier transforms in momentum space , that is consistent with the requirement for translational invariance ( ti ) , in the case of a nucleus ( a finite self - bound system ) .
we restore ti by using the so - called fixed center - of - mass ( cm ) approximation for constructing an intrinsic nuclear ground state wavefunction ( wf ) by starting from a non - translationally invariant ( nti ) wf and applying a projection prescription .
we discuss results for the one - body ( obmd ) and two - body ( tbmd ) momentum distributions of the @xmath0he nucleus calculated with the slater determinant of the harmonic oscillator ( ho ) orbitals , as the initial nti wf .
effects of such an inclusion of cm correlations are found to be quite important in the momentum distributions .
address = ncs `` kharkov institute of physics and technology '' , academicheskaya str . 1 , + 61108 kharkov , ukraine ( [email protected] )
address = institute of nuclear physics , t.u.darmstadt , schlossgartenstr .
9 , d-64289 darmstadt , germany ( [email protected] ) address = university of athens , physics department , nuclear and particle physics division , panepistimiopoli , ilissia , gr-15771 athens , greece ( [email protected] ) .
And you have already written the first three sentences of the full article: the last years the interest in the study of nuclei from both experimental and theoretical point of view involves , besides the 1 dm @xmath1}(\vec{r}_1,\vec{r}_{1 ' } ) \equiv a \int \psi^{\ast}(\vec{r}_1,\vec{r}_2,\ldots,\vec{r}_a ) \psi ( \vec{r}_{1'},\vec{r}_2,\ldots,\vec{r}_a ) { \rm d}^3r_2\ldots { \rm d}^3r_a \label{eq01}\ ] ] and the obmd @xmath2 } ( \vec{r}_1,\vec{r}_{1 ' } ) { \rm d}^3r_1{\rm d}^3r_{1 ' } , \label{eq02}\ ] ] also the 2 dm @xmath3}(\vec{r}_1,\vec{r}_2;\vec{r}_{1'},\vec{r}_{2 ' } ) \equiv a(a-1 ) \int \psi^{\ast}(\vec{r}_1,\vec{r}_2,\vec{r}_3,\ldots,\vec{r}_a ) \psi ( \vec{r}_{1'},\vec{r}_{2'},\vec{r}_3,\ldots,\vec{r}_a ) { \rm d}^3r_3\ldots { \rm d}^3r_a \label{eq03}\ ] ] and its fourier transforms , for instance the tbmd @xmath4 } ( \vec{p},\vec{k } ) \equiv \int { \rm e}^ { { \rm i } \vec{p}\cdot ( \vec{r}_1-\vec{r}_{1 ' } ) } { \rm e}^ { { \rm i } \vec{k}\cdot ( \vec{r}_2-\vec{r}_{2 ' } ) } \rho^{[2 ] } ( \vec{r}_1,\vec{r}_2;\vec{r}_{1'},\vec{r}_{2 ' } ) { \rm d}^3r_1{\rm d}^3r_{1 ' } { \rm d}^3r_2{\rm d}^3r_{2 ' } .
\label{eq04}\ ] ] the above quantities provide among others information on the short - range correlations ( src ) in nuclei . a prominent role towards the experimental investigation of the 2 dm and related quantities
is played by the study of electromagnetically induced two - nucleon emission @xmath5 , @xmath6 , carried out with high precision in photon facilities ( elsa , mami ) and electron accelerators with high energy 100% duty - cycle beams ( jlab , mami ) @xcite ..
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one of the theoretical issues still under discussion is a proper consideration of ti and the respective separation of spurious cm effects.the latter contaminate the calculated observables , when the independent - particle shell model and theories which take also dynamical correlations into account ( e.g. , brueckner - hartree - fock , variational monte carlo ) are used , and inhibit the extraction of reliable information on the intrinsic properties of nuclei directly from the experimental data ( see , e.g. , @xcite and refs . therein ) . in this context
, we prefer to deal with the intrinsic obmd and tbmd and the associated 1 dm and 2 dm @xcite .
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10,008 |
Suppose that you have an abstract for a scientific paper: we investigate the amount of noise required to turn a universal quantum gate set into one that can be efficiently modelled classically .
this question is useful for providing upper bounds on fault tolerant thresholds , and for understanding the nature of the quantum / classical computational transition .
we refine some previously known upper bounds using two different strategies .
the first one involves the introduction of bi - entangling operations , a class of classically simulatable machines that can generate at most bipartite entanglement . using this class
we show that it is possible to sharpen previously obtained upper bounds in certain cases . as an example
, we show that under depolarizing noise on the controlled - not gate , the previously known upper bound of 74% can be sharpened to around 67% .
another interesting consequence is that measurement based schemes can not work using only 2-qubit non - degenerate projections . in the second strand of the work we utilize the gottesman - knill theorem on the classically efficient simulation of clifford group operations . the bounds attained using this approach for the @xmath0-gate can be as low as 15% for general single gate noise , and 30% for dephasing noise . .
And you have already written the first three sentences of the full article: the recent development of quantum information has led to a great deal of interest in the classical simulation of quantum systems .
an understanding of this issue is important in order to discern which resources are essential for an exponential quantum speedup .
if we remove certain resources from a particular model for universal quantum computation , and find that the resulting machine can be efficiently simulated classically , then we can infer that those resources are essential to any exponential speedup that the original device may offer ..
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for instance , this approach has been used to show that quantum entanglement is an essential ingredient for quantum computation @xcite while fermionic linear optics does not allow for an exponential speedup @xcite .
in addition to questions of resources , an understanding of classically tractable quantum evolution is also useful for bounding the fault tolerance thresholds of universal quantum machines .
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10,009 |
Suppose that you have an abstract for a scientific paper: in this article we discuss an implementation of renormalization group ideas to spin foam models , where there is no a priori length scale with which to define the flow . in the context of the continuum limit of these models ,
we show how the notion of cylindrical consistency of path integral measures gives a natural analogue of wilson s rg flow equations for background - independent systems .
we discuss the conditions for the continuum measures to be diffeomorphism - invariant , and consider both exact and approximate examples . .
And you have already written the first three sentences of the full article: the application of renormalization techniques to quantum gravity theories has always been problematic .
this is due to the inherent tension between the notion of scale - dependent physics of the renormalization group on the one side , and the role of background - independence of general relativity on the other side .
the renormalization group is a tool for dealing with a phenomenon that is inherent to many physical systems with a very large number of degrees of freedom , which are nonlinear , i.e. exhibit nontrivial self - interaction . to describe such systems ,.
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it is convenient to not consider all degrees of freedom on an equal footing , but rather to order them according to some hierarchy . this way one considers only a finite and manageable amount of the system at a time .
this hierarchy often runs along a length scale , introducing a notion of `` smaller '' and `` larger '' degrees of freedom .
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10,010 |
Suppose that you have an abstract for a scientific paper: we have obtained the first large sample of accurate temperatures for clusters at @xmath0 from asca .
we compare the luminosity temperature ( l - t ) distribution for these clusters with the low redshift sample of david et al ( 1993 ) and find that there is no evidence for evolution .
we also find that the intrinsic variance in this relation is roughly constant with redshift . additionally , there is no detectable change in the relationship of optical velocity dispersion to x - ray temperature with redshift .
most cosmological simulations driven primarily by gravity predict substantial changes in the l - t relation due to the recent rapid growth of clusters .
our results are consistent either with models in which the cluster core entropy is dominated by pre - heating , or with low @xmath1 models in which cluster structure does not evolve strongly with time .
the intrinsic variance in the l - t relation at a fixed redshift can be due a variety of possibilites e.g. a change in the baryonic fraction from cluster to cluster , variation in the fraction of the total energy in the system arising from shocks or supernova heating or variations in the emission measure distributions in multiphase gas . .
And you have already written the first three sentences of the full article: clusters of galaxies are the largest relaxed systems in the universe and as such provide a strong test of theories of the origin of and evolution of structure .
a critical measurement ( @xcite ) is the relationship of the mass of a system to its temperature .
this can be best probed by comparing the evolution of the x - ray luminosity ( which is related to the baryonic mass ) to the x - ray temperature , which is roughly proportional to @xmath2 ..
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calculations of the evolution of these quantities ( c.f .
, @xcite , @xcite ) indicate that , in a closed universe , where gravity dominates the evolution of the gas and the dark matter , the relationship between luminosity and temperature should evolve strongly at all redshifts , with significant changes occurring at @xmath3
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10,011 |
Suppose that you have an abstract for a scientific paper: we study the signatures of a two higgs doublet model of davidson and logan .
the model includes an extra higgs doublet with the vacuum expectation value ( vev ) much smaller than the one of the standard model like higgs .
the smaller vev is related to the origin of the small neutrino mass in the two higgs doublet model . in the model , a single non - standard model like higgs production of weak gauge boson fusion
is suppressed due to the smallness of the vacuum expectation value .
in contrast to the single higgs production , the cross section of the higgs pair production due to gauge boson fusion is not suppressed . using the model , we compute the charged higgs and neutral higgs pair production cross section in w@xmath0 z annihilation channel . in the two higgs doublet model ,
the charged higgs @xmath1 decays into a pair of the charged anti - lepton and right - handed neutrino .
the neutral higgs boson decays into right - handed neutrino and left - handed anti - neutrino pair which is invisible .
a single charged anti - lepton and three neutrinos are the products of the subsequent decays of the charged higgs and the neutral higgs .
w@xmath0 z pair production gives the background for the signal through the decays @xmath2 and @xmath3 . by multiplying the charged and neutral higgses production cross section with the lepton flavor specific decay branching fractions of charged higgs
, we define a measurement which characterizes the present model .
we numerically compute the measurement and find the sizable deviation from the standard model prediction . #
1/#1 s / .
And you have already written the first three sentences of the full article: probing the higgs sector beyond the standard model is a main subject of new physics search in collider experiments and in flavor factories . among them , two higgs doublet models have been studied in their many aspects . here
we study the two higgs doublet model in which the hierarchy of the neutrino mass and the other fermions mass is explained by two higgs vacuum expectation values ( vevs ) with large hierarchy @xcite . in the model ,
the neutrino mass is protected from the large standard model like higgs vev by assigning u(1 ) charge for right - handed neutrino and the second higgs ..
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the corresponding u(1 ) symmetry is softly broken .
moreover the tiny vev of the second higgs is stable against the radiative corrections , @xcite . in this letter , we study the production of the higgs bosons in the second doublet in gauge bosons fusion process .
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10,012 |
Suppose that you have an abstract for a scientific paper: the generation of quantum entanglement of macroscopic or mesoscopic bodies in mechanical motion is generally bounded by the thermal fluctuation exerted by their environments . here we propose a scheme to establish stationary entanglement between two mechanically oscillating mirrors of a cavity .
it is revealed that , by applying a broadband squeezed laser acting as a squeezed - vacuum reservoir to the cavity , a stable entanglement between the mechanical mirrors can be generated . using the adiabatic elimination and master equation methods
, we analytically find that the generated entanglement is essentially determined by the squeezing of the relative momentum of the mechanical mirrors , which is transferred from the squeezed reservoir through the cavity .
numerical verification indicates that our scheme is within the present experimental state of the art of optomechanics . .
And you have already written the first three sentences of the full article: quantum entanglement , as a cornerstone in understanding many phenomena in quantum world @xcite , serves as a necessary resource in various practical applications of quantum information processing , such as quantum algorithms @xcite , quantum teleportation @xcite , and quantum crytography @xcite . in the past decade ,
tremendous efforts have been devoted to generate entanglement in microscopic systems @xcite .
recently , the generation of entanglement in macroscopic and mesoscopic objects and the study of quantum mechanical features in these scales have attracted much attentions @xcite ..
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an optomechanical system supplies an ideal platform to explore quantum features of macroscopic or mesoscopic objects in mechanical motion @xcite .
advances in this field raise a fundamental question : whether mechanical systems in macroscopic scale exhibit quantum behavior ?
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10,013 |
Suppose that you have an abstract for a scientific paper: the process of gap formation by a growing planetary embryo embedded in a planetesimal disk is considered .
it is shown that there exists a single parameter characterizing this process , which represents the competition between the gravitational influence of the embryo and planetesimal - planetesimal scattering .
for realistic assumptions about the properties of the planetesimal disk and the planetary embryo , a gap is opened long before the embryo can accrete all the bodies within its region of influence .
the implication of this result is that the embryo stops growing and , thus , large bodies formed during the coagulation stage should be less massive than is usually assumed . for conditions expected at @xmath0 au in the solar protoplanetary disk , gap formation
is expected to occur around bodies of mass @xmath1 g. the effect of protoplanetary radial migration is also discussed . .
And you have already written the first three sentences of the full article: the formation of planets is one of the most complex problems in astrophysics , involving accumulation of bodies over some @xmath2 orders of magnitude in mass from dust grains to giant planets .
one issue which has received a lot of attention is the formation of planetary embryos by the accretion of planetesimals . from the perspective of dynamics we call an object an embryo when it becomes so massive that one can no longer describe its behavior by means of simple kinetic theory ( in this paper we use names embryo , protoplanet and massive body interchangeably ) . in other words , in the presence of embryos the multiparticle distribution function can not be taken as a product of one - particle distribution functions ; the gravitational influence of the embryo is strong enough to affect the distribution of planetesimals with which it interacts .
for example , a gap could form around the embryo . to study properties of systems containing embryos.
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one must either resort to n - body simulations or try to account properly for their influence on the underlying planetesimal population and on each other . in the standard scenario ,
protoplanets grow in orderly ( safronov , 1972 ) or runaway fashion ( wetherill & stewart , 1989 ; wetherill & stewart , 1993 ) by accreting planetesimals from the protoplanetary nebula .
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10,014 |
Suppose that you have an abstract for a scientific paper: two different induced effects of a laser falling edge on high - order harmonic generation are resolved by solving numerically full - dimensional electronic time - dependent schrdinger equation beyond the born - oppenheimer approximation .
the harmonic spectrum of h@xmath0 and t@xmath0 isotopes are compared to see the effects of a 4-cycle falling edge of a 800 nm , 15-cycle trapezoidal laser pulse of @xmath13 @xmath2 w@xmath3 intensity on harmonic emission spectrum .
the harmonic emission at the laser falling part is negligible for h@xmath0 due to ionization suppression , but considerable for t@xmath0 .
the falling edge of the laser pulse induces two effects on the hhg in t@xmath0 .
the first well - known effect is non - adiabatic frequency redshift of generated odd - order harmonics .
the second unknown one is spatially asymmetric harmonic emission which appears as even harmonic orders . in order to clarify this new effect , spatial distribution of hhg and resolving hhg into different components are demonstrated .
the asymmetric emission would appear for both atoms and molecules as long as harmonic emission of either rising or falling edge of an intense trapezoidal or non - trapezoidal laser pulse is dominant . .
And you have already written the first three sentences of the full article: an electron in the ground state of hydrogen atom in bohr s model has an orbital period of 150 attosecond ( 1 as=@xmath4 s ) . in order to temporally
resolve electronic dynamics in real time , it is necessary to follow its dynamics within attosecond time scales .
nowadays , this attosecond temporal resolution is accessible with attosecond and even femtosecond laser pulses [ 1 ] ..
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first attosecond laser pulse was measured in 2001 based on high - oder harmonic generation ( hhg)[2,3 ] .
the underlying mechanism of hhg is often described by a three - step semi - classical model [ 4 ] . in the first step , an electron releases into continuum via tunneling .
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10,015 |
Suppose that you have an abstract for a scientific paper: in this study , we investigated the @xmath0k , h@xmath1 @xmath0k , k@xmath2 @xmath0h , k@xmath3weingarten and @xmath0k , h@xmath4k , k@xmath5h , k@xmath6 and @xmath7linear weingarten canal surfaces in ir@xmath8 .
[ multiblock footnote omitted ] .
And you have already written the first three sentences of the full article: in 1863 , julius weingarten was able to make a major step forward in the topic when he gave a class of surfaces isometric to a given surface of revolution .
surface for which there is a definite functional relation between the principal curvatures ( which called curvature diagram ) and also between the gaussian and the mean curvatures is called weingarten surface .
the knowledge of first fundamental form i and second fundamental form ii of a surface facilitates the analysis and the classification of surface shape . especially recent years , the geometry of the second fundamental form ii has become an important issue in terms of investigating intrinsic and extrinsic geometric properties of the surfaces ..
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very recent results concerning the curvature properties associated to ii and other variational aspects can be found in @xcite .
one may associate to such a surface m geometrical objects measured by means of its second fundamental form , as second gaussian curvature k@xmath9 , respectively .
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10,016 |
Suppose that you have an abstract for a scientific paper: recently , the @xmath0-nonconforming finite element space over square meshes has been proved stable to solve stokes equations with the piecewise constant space for velocity and pressure , respectively . in this paper
, we will introduce its locally divergence - free subspace to solve the elliptic problem for the velocity only decoupled from the stokes equation .
the concerning system of linear equations is much smaller compared to the stokes equations .
furthermore , it is split into two smaller ones . after solving the velocity first
, the pressure in the stokes problem can be obtained by an explicit method very rapidly .
[ section ] [ theorem]remark [ theorem]lemma [ theorem]proposition [ theorem]definition [ section ] 2h_2h u v c .
And you have already written the first three sentences of the full article: a divergence - free vector field frequently appears in various mathematical and engineering problems such as an incompressible flow in the navier - stokes equation or a solenoidal magnetic induction in the maxwell equations or the limit of displacements in elasticity equations when poisson s ratio goes to 1/2 .
an incompressible stokes problem can be reduced to an elliptic problem for the velocity only in the divergence - free space @xcite .
the locally divergence - free subspace of @xmath1 ^ 2 $ ] was used for finite element methods to solve that elliptic problem @xcite , where @xmath2 is the crouzeix - raviart @xmath0-nonconforming finite element space on triangular meshes ..
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it have also been adopted for the time - harmonic maxwell equations @xcite .
it is equipped with sufficient interpolants for continuous divergence - free functions in @xmath3 ^ 2 $ ] , since it can be interpreted as the curls of the morley element .
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10,017 |
Suppose that you have an abstract for a scientific paper: taking partial traces for computing reduced density matrices , or related functions , is a ubiquitous procedure in the quantum mechanics of composite systems . in this article , we present a thorough description of this function and analyze the number of elementary operations ( ops ) needed , under some possible alternative implementations , to compute it on a classical computer . as we notice , it is worthwhile doing some analytical developments in order to avoid making null multiplications and sums , what can considerably reduce the ops .
for instance , for a bipartite system @xmath0 with dimensions @xmath1 and @xmath2 and for @xmath3 , while a direct use of partial trace definition applied to @xmath4 requires @xmath5 ops , its optimized implementation entails @xmath6 ops . in the sequence , we regard the computation of partial traces for general multipartite systems and describe fortran code provided to implement it numerically .
we also consider the calculation of reduced density matrices via bloch s parametrization with generalized gell mann s matrices . .
And you have already written the first three sentences of the full article: when calculating certain functions of quantum systems , in many instances the running time of classical computers increases exponentially with the number of elementary parts that compose those systems .
this issue is a hurdle to current research in many areas of science .
but it is also a motive for the quest towards the construction of a large scale quantum computer @xcite . for.
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now , we have to resort to several other alternative techniques , with which one can extract approximate information about quantum systems using only the available classical computing power . among those methods ,
some famous examples are : stochastic monte carlo simulations @xcite , mean field approximations @xcite , density functional theory @xcite , renormalization group @xcite , and matrix product states and projected entangled pair states @xcite . on the other hand , recently several authors have shown that some general patterns of the many - body behavior , usually accessed in the thermodynamical limit , may be disclosed by analyzing systems with a moderate number of particles @xcite . in such kind of investigation , it is desirable to use a system as large as practically possible . and for that purpose we would like to optimize the implementation of basic and frequently used functions in order to reduce the computation time as much as possible . in the quantum mechanics of composite systems ,
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10,018 |
Suppose that you have an abstract for a scientific paper: an implicit lagrangian hydrodynamics code for general relativistic spherical collapse is presented .
this scheme is based on an approximate linearized riemann solver ( roe type scheme ) and needs no artificial viscosity .
this code is aimed especially at the calculation of the late phase of collapse - driven supernovae and the nascent neutron star , where there is a remarkable contrast between the dynamical time scale of the proto - neutron star and the diffusion time scale of neutrinos , without such severe limitation of the courant condition at the center of the neutron star .
several standard test calculations have been done and their results show ( 1 ) this code captures the shock wave accurately , though some erroneous jumps of specific internal energy are found at the contact discontinuity in the shock tube problems .
( 2 ) the scheme shows no instability even if we choose the courant number larger than 1 .
( 3 ) however , the courant number should be kept below @xmath0 at the shock position so that the shock can be resolved with a few meshes .
( 4 ) the scheme reproduces the well known analytic solutions to the point blast explosion , the gravitational collapse of the uniform gas with @xmath1 and the general relativistic collapse of uniform dust .
two other adiabatic simulations have also been done in order to test the performance of the code in the context of the collapse - driven supernovae .
it is found that the time step can be extended far beyond the courant limitation at the center of the neutron star .
the details of the scheme and the results of these test calculations are discussed . .
And you have already written the first three sentences of the full article: since the pioneering work by colgate and white ( 1966 ) , detailed studies of the dynamics of collapse - driven supernovae have been done mainly with numerical simulations ( @xcite , @xcite , and references therein ) .
one of the difficulties in so doing is the remarkable contrast between the dynamical time scale of the nascent neutron star ( @xmath2msec ) and the diffusion time scale of neutrinos ( @xmath3sec ) .
if we want to simulate the whole scenario of the collapse - driven supernovae , these time scales should be treated simultaneously ..
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since the typical time scale of weak interactions ( @xmath4sec ) is much smaller than the dynamical time scale , the neutrino transfer has been treated in implicit ways in general .
the hydrodynamics , however , has been calculated chiefly by explicit schemes , so that the time steps are restricted by the courant condition and a large number of integration steps are required to simulate the late stage of collapse - driven supernovae .
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10,019 |
Suppose that you have an abstract for a scientific paper: we investigate the possibility of exciting self - oscillation in a perpendicular ferromagnet by the spin hall effect on the basis of a nonlinear analysis of the landau - lifshitz - gilbert ( llg ) equation . in the self - oscillation state , the energy supplied by the spin torque during a precession on a constant energy curve should equal the dissipation due to damping . also , the current to balance the spin torque and the damping torque in the self - oscillation state should be larger than the critical current to destabilize the initial state .
we find that these conditions in the spin hall system are not satisfied by deriving analytical solutions of the energy supplied by the spin transfer effect and the dissipation due to the damping from the nonlinear llg equation .
this indicates that the self - oscillation of a perpendicular ferromagnet can not be excited solely by the spin hall torque . .
And you have already written the first three sentences of the full article: nonlinear dynamics such as fast switching and self - oscillation ( limit cycle ) has been a fascinating topic in physics @xcite .
magnetization dynamics excited by the spin transfer effect @xcite in a nanostructured ferromagnet @xcite provide fundamentally important examples of such nonlinear dynamics .
the magnetization switching was first observed in co / cu metallic multilayer in 2000 @xcite ..
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three years later , self - oscillation was reported in a similar system @xcite . in these early experiments on the spin transfer effect
, linear analysis was used to estimate , for example , the critical current destabilizing the magnetization in equilibrium @xcite . however , recently it became clear that nonlinear analysis is necessary to quantitatively analyze the magnetization dynamics @xcite .
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10,020 |
Suppose that you have an abstract for a scientific paper: novel behavior of the critical current density @xmath0 of a regularly perforated superconducting film is found , as a function of applied magnetic field @xmath1 .
previously pronounced peaks of @xmath0 at matching fields were always found to decrease with increasing @xmath1 .
here we found a _ reversal of this behavior _ for particular geometrical parameters of the antidot lattice and/or temperature .
this new phenomenon is due to a strong `` caging '' of interstitial vortices between the pinned ones .
we show that this vortex - vortex interaction can be further tailored by an appropriate choice of the superconducting material , described by the ginzburg - landau parameter @xmath2 . in effective type - i samples
we predict that the peaks in @xmath3 at the matching fields are transformed into a _ step - like behavior_. .
And you have already written the first three sentences of the full article: for practical applications of superconducting ( sc ) materials , the increase and , more generally , control of the critical current in sc samples are of great importance . in recent years
much attention was given to the investigation of superconducting films patterned with a regular array of microholes ( antidots ) , which have a profound influence on both the critical current and the critical magnetic field @xcite .
due to the collective pinning to the regular antidot array , vortices are forced to form rigid lattices when their number `` matches '' integer and fractional multiples of the number of pinning sites at fields @xmath4 , and @xmath5 ( where @xmath6 are integers ) respectively , where @xmath7 is the flux quantum , and @xmath8 is the area of the unit cell of the antidot lattice ..
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this locking between the pinning array and the vortex lattice is responsible for the reduced mobility of the vortices in applied drive and consequently the increased critical current at integer and fractional matching fields , was confirmed both by experiments ( imaging @xcite , magnetization and transport measurements @xcite ) and molecular dynamics simulations @xcite .
however , regardless on the imposed pinning profile , the vortices at interstitial sites always have high mobility @xcite , show different dynamic regimes from the pinned ones , and their appearance is followed by a sharp drop in the critical current @xcite . in this respect ,
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10,021 |
Suppose that you have an abstract for a scientific paper: here we describe a compact and efficient strontium oven well suited for laser - cooling experiments .
novel design solutions allowed us to produce a collimated strontium atomic beam with a flux of @xmath0 at the oven temperature of @xmath1 , reached with an electrical power consumption of @xmath2w . the oven is based on a stainless - steel reservoir , filled with @xmath3 g of metallic strontium , electrically heated in a vacuum environment by a tantalum wire threaded through an alumina multi - bore tube .
the oven can be hosted in a standard dn40cf cube and has an estimated continuous operation lifetime of 10 years .
this oven can be used for other alkali and alkaline earth metals with essentially no modifications . .
And you have already written the first three sentences of the full article: laser cooling is today an established technique to produce samples of atoms with temperature approaching the zero kelvin limit .
ultra - cold strontium samples are largely studied , with experiments ranging from quantum degeneracy , quantum computation , to applications as quantum sensors of force and highly accurate optical clocks .
these experiments are all based on an oven , which provides the needed flux of atoms in an ultra high vacuum ( uhv ) environment ( pressure @xmath4 mbar ) . at room temperature.
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the vapor pressure of alkaline earth metals ( as strontium ) is lower than that of alkali at the same temperature , for this reason relatively high temperature ovens are typically needed ( @xmath5c for @xmath6 ) . in particular the application of alkaline earth metals for optical clocks is today prompting significant scientific and technological efforts for the realization of compact , reliable and transportable apparatus , in the perspective of a their future use in space @xcite .
this background is at the basis of our study on an efficient strontium oven , which represents one of the critical parts in an optical clock in terms of power consumption , size and heat management .
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10,022 |
Suppose that you have an abstract for a scientific paper: recently , there has been an upsurge of the number of articles on spatio - temporal modeling in statistical journals .
many of them focus on building good nonstationary spatio - temporal models . in this article
, we introduce a state space based nonparametric nonstationary model for the analysis of spatio - temporal data .
we consider that there are some fixed spatial locations ( generally called the monitoring sites ) and that the data have been observed at those locations over a period of time . to model the data we assume that the data generating process is driven by some latent spatio - temporal process , which itself is evolving with time in some unknown way .
we model this evolutionary transformation via compositions of a gaussian process and also model the unknown functional dependence between the data generating process and the latent spatio - temporal process ( observational transformation ) by another gaussian process .
we investigate this model in detail , explore the covariance structure and formulate a fully bayesian method for inference and prediction .
finally , we apply our nonparametric model on two simulated data sets and a real data set and establish its effectiveness . + _ keywords : _ observational equation ; evolutionary equation ; gaussian process ; state - space model ; mcmc ; gibbs sampler ; posterior predictive distribution .
+ _ ams 2000 subject classification : _ primary 62m20 , 62m30 ; secondary 60g15 . .
And you have already written the first three sentences of the full article: spatio - temporal modeling has received much attention in recent years . particularly , the rise in global temperature being a major environmental concern
, scientists are now taking keen interest in the study of the dynamics of such climatic spatio - temporal processes@xcite .
another closely related class of spatio - temporal processes , that are also of much importance to climatologists , are daily rainfall and precipitation ( like mist , snowfall etc . ) across a region . apart from climatology ,.
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many important spatio - temporal processes are also associated with different subfields of environmental and ecological science . to mention a few , studies on ground level concentration of ozone , @xmath0 , @xmath1 and pm ,
species distribution over a region , change in land usage pattern over time , etc .
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10,023 |
Suppose that you have an abstract for a scientific paper: nearly all field theories suffer from singularities when particles are introduced .
this is true in both classical and quantum physics .
classical field singularities result in the notorious self - force problem , where it is unknown how the dynamics of a particle change when the particle interacts with its own ( self ) field .
self - force is a pressing issue and an active research topic in gravitational phenomena , as well as a source of controversies in classical electromagnetism . in this work ,
we study a hidden geometrical structure manifested by the electromagnetic field - lines that has the potential of eliminating all singularities from classical electrodynamics .
we explore preliminary results towards a consistent way of treating both self- and external fields . .
And you have already written the first three sentences of the full article: the notion of a field - line was introduced by michael faraday in his work on magnetism @xcite .
faraday argued that the forces of electricity , magnetism and gravity are better described by fields , populated with field - lines . from faraday
s point of view , a field is not a mere mathematical abstract but a real physical object . today , despite faraday s groundbreaking work , field - lines.
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are commonly used as a mere pedagogical tool for visualizing classical fields rather than providing a genuine clue about the field s physical nature .
we suggest to revive the field s ontological status in light of several open problems in physics .
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Suppose that you have an abstract for a scientific paper: during a hubble time , cluster galaxies may undergo several mutual encounters close enough to gravitationally perturb their hot , x ray emitting gas flows .
we ran several 2d , time dependent hydrodynamical models to investigate the effects of such perturbations on the gas flow inside elliptical galaxies , focusing on the expected x ray properties .
in particular , we studied in detail the modifications occurring in the scenario proposed by dercole et al .
( 1989 ) , in which the galactic interstellar medium produced by the aging galactic stellar population , is heated by type ia supernovae ( snia ) at a decreasing rate .
we find that , although the tidal interaction in our models lasts less than 1 gyr , its effect extends over several gyrs .
the tidally induced turbulent flows create dense filaments which cool quickly and accrete onto the galactic center , producing large spikes in the global x ray luminosity @xmath0 .
once this mechanism starts , it is fed by gravity and amplified by snia .
this evolution is found to be virtually independent of the dynamical state of the gas flow at the beginning of the interaction .
to better understand the role of snia heating , we also considered a `` pure '' cooling flow model without supernovae ; in this case the amplitude of the @xmath0 fluctuations due to the tidal interaction is substantially reduced .
we conclude that , if snia significantly contribute to the energetics of the gas flows in ellipticals , then the observed spread in the @xmath1 diagram at any fixed optical galaxy luminosity @xmath2 may be caused , at least in part , by this mechanism . on the contrary
, tidal interactions can not be responsible for the observed spread if the pure cooling flow scenario applies .
= cmmib10=cmmib10 = 11 versim#1#22.9truept = 12 # 1to 0pt#1 .
And you have already written the first three sentences of the full article: in a previous paper dercole et al .
( 1989 ) proposed the wind outflow
inflow ( woi ) scenario as a possible explanation for one of the most striking properties of the x ray emission of elliptical galaxies , i.e. , the large scatter in the @xmath1 diagram of roughly two orders of magnitude in @xmath0 at any fixed @xmath3 ( fabbiano 1989 , fabbiano , kim & trinchieri 1992 ) . in their subsequent extensive exploration of 1d hydrodynamical models.
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ciotti et al .
( 1991 , hereafter cdpr ) assumed that the type i supernova ( snia ) rate decreases in time as @xmath4 , faster than the decrease of the mass return rate from the ( passively ) evolving stellar population , which varies in time approximately as @xmath5 . in these models ,
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10,025 |
Suppose that you have an abstract for a scientific paper: we develop a procedure to determine the portion of exact hartree - fock exchange interaction contained in a hybrid density functional to treat the range of electronic correlation governing the physics of a system as a function of a thermodynamical parameter .
this includes systems that depend on physical parameters accessible to experiment ( i.e. , temperature , pressure , composition , etc . ) or those composed of two or more materials such as heterostructures and interfaces .
this approach is applied to lamno@xmath0 where for the first time we are able to simulate the high temperature insulator - to - metal transition ( imt ) and observe a half - metallic orbital disorder ferromagnetic state using density functional theory . in particular , we show that the softening of the _ q@xmath1 _ jahn - teller mode plays a central role in driving the imt .
these findings are likely to motivate the investigation of heterostructures and bulk materials that contain a range of electronic correlation in similar material systems .
pacs numbers : : 71.30.+h , 31.15.a- , 71.20.be , 71.70.ej .
And you have already written the first three sentences of the full article: lamno@xmath0 perovskite - type manganites have been subjected to intense scrutiny due to the existence of highly desired properties such as the observed colossal magnetoresistance ( cmr ) by either introducing impurities @xcite or applying pressure @xcite .
this effect along with the occurrence of fully spin - polarized conduction bands @xcite makes these materials ideal candidates for the development of spintronic applications @xcite .
lamno@xmath0 exhibits a range of electronic correlation ( i.e. , different strength of the electronic interactions in the system ) as a function of temperature . at low temperature.
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the system is a mott - hubbard a - type antiferromagnetic ( a - afm ) insulator that crystallizes in the pbnm orthorhombic structure @xcite .
however , at temperatures above t@xmath2 = 750 k the system forms a _ pseudo - cubic _ ferromagnetic ( fm ) metal @xcite where @xmath3 and @xmath4 lattice parameters are nearly equal @xcite .
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10,026 |
Suppose that you have an abstract for a scientific paper: a local principal curve algorithm has been implemented in three dimensions for automated track and shower reconstruction of neutrino interactions in a liquid argon time projection chamber .
we present details of the algorithm and characterise its performance on simulated data sets . .
And you have already written the first three sentences of the full article: liquid argon time projection chambers ( lar - tpcs ) , that are currently in development in various r&d programmes in europe , japan and the usa @xcite , are acknowledged to be a detector technology capable of meeting the physics requirements of a next - generation neutrino oscillation experiment .
they can provide simultaneous tracking and calorimetry of particles from neutrino interactions over a wide range of energies , with exquisite millimetric granularity , as demonstrated by results from icarus @xcite . despite this advantage
, it has proven difficult to achieve an automated software process that can fully reconstruct neutrino interactions , which will contain a mixture of ionisation tracks as well as electromagnetic and hadronic showers , especially when the neutrino interaction point is not known beforehand . in this paper , we describe a first application of using local principal curves @xcite to automatically reconstruct neutrino interactions using three - dimensional lar - tpc data . when a charged particle passes through a liquid argon medium it releases a stream of ionisation charge which can be measured by a tpc to provide a 3d trajectory in space.
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. we can represent this data as a collection of `` hits '' , each of which contain the spatial cell co - ordinate information ( @xmath0 ) as well as the charge or energy deposit @xmath1 .
the task of any reconstruction algorithm is to first obtain the hits from the detector output , then group these hits into clusters in order to identify the particles coming from the neutrino interaction , before extracting physics parameters such as momentum or energy from the reconstructed particles . here ,
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10,027 |
Suppose that you have an abstract for a scientific paper: in this article , we assume the @xmath0 as the color octet - octet type axial - vector molecule - like state , and construct the color octet - octet type axial - vector current to study its mass and width with the qcd sum rules .
the numerical values @xmath1 and @xmath2 are consistent with the experimental data @xmath3 and @xmath4 , and support assigning the @xmath0 to be the color octet - octet type molecule - like state with @xmath5 .
furthermore , we discuss the possible assignments of the @xmath6 , @xmath0 and @xmath7 as the diquark - antidiquark type tetraquark states with @xmath5 .
+ zhi - gang wang + department of physics , north china electric power university , baoding 071003 , p. r. china pacs number : 12.39.mk , 12.38.lg key words : molecule - like state , qcd sum rules .
And you have already written the first three sentences of the full article: in 2014 , the belle collaboration analyzed the @xmath8 decays with the full @xmath9 data sample corresponds to @xmath10 data sample collected by the belle detector at the asymmetric - energy @xmath11 collider , and observed a resonance ( named @xmath0 ) in the @xmath12 mass spectrum with a statistical significance of more than @xmath13 , the measured mass and width are @xmath3 and @xmath4 , respectively @xcite .
the preferred assignment of the quantum numbers is @xmath14 . in 2007 ,
the belle collaboration observed a distinct peak in the @xmath15 mass spectrum in the @xmath16 decays with the statistical significance of @xmath17 @xcite . in 2014 ,.
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the lhcb collaboration analyzed the @xmath18 decays by performing a four - dimensional fit of the decay amplitude , and provided the first independent confirmation of the @xmath19 and established its spin - parity to be @xmath20 @xcite . in 2013 ,
the besiii collaboration studied the process @xmath21 and observed a structure @xmath6 in the @xmath22 mass spectrum @xcite .
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10,028 |
Suppose that you have an abstract for a scientific paper: we have used the seven year _ wilkinson microwave anisotropy probe _ ( wmap ) data in order to update the measurements of the intensity signal in the region within the perseus molecular complex , and to set constraints on the polarization level of the anomalous microwave emission in the frequency range where this emission is dominant . at 23 , 33 and 41 ghz
, we obtain upper limits on the fractional linear polarization of 1.0 , 1.8 and 2.7% respectively ( with a 95 per cent confidence level ) .
these measurements rule out a significant number of models based on magnetic dipole emission of grains that consist of a simple domain @xcite as responsible of the anomalous emission .
when combining our results with the measurement obtained with the cosmosomas experiment at 11 ghz @xcite , we find consistency with the predictions of the electric dipole and resonance relaxation theory @xcite at this frequency range . .
And you have already written the first three sentences of the full article: the dust - correlated microwave ( 10 - 60 ghz ) emission detected by several cosmic microwave background ( cmb ) experiments performed in the two last decades ( cobe @xcite ; ovro at 14.5 and 32 ghz @xcite ; saskatoon @xcite ; 19 ghz @xcite ; tenerife @xcite ; cosmosomas @xcite ; vsa @xcite ; and references therein ) suggests the existence of a new continuum microwave emission mechanism unlike to the three well - known galactic mechanisms : synchrotron , free - free and thermal dust emission .
a remarkable observational effort has been devoted to the understanding of the intensity and polarization properties of this `` anomalous '' microwave emission , among other reasons , because of the importance of an accurate foreground correction of the cmb maps at low frequencies . among the various scenarios proposed to explain this emission , electric dipole radiation @xcite from very small ( n @xmath0 atoms ) rapidly rotating ( @xmath1 ) carbon based molecules in the interstellar medium ( the so - called `` _ spinning dust _ '' ) appears to reproduce well the observational constraints ( see e.g. * ? ? ?
* ; * ? ? ?.
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* ; * ? ? ?
* ; * ? ? ?
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10,029 |
Suppose that you have an abstract for a scientific paper: the particle number projected bcs ( pbcs ) approximation is tested against the exact solution of the so(5 ) richardson - gaudin model for isovector pairing in a system of non - degenerate single particle orbits .
two isovector pbcs wave functions are considered .
one is constructed as a single proton - neutron pair condensate , while the other corresponds to a product of a neutron pair condensate and a proton pair condensate .
the pbcs equations are solved using a recurrence method and the analysis is performed for systems with an equal number of neutrons and protons distributed in a sequence of equally spaced 4-fold ( spin - isospin ) degenerate levels .
the results show that although pbcs improves significantly over bcs , the agreement of pbcs with the exact solution is less satisfactory than in the case of the su(2 ) richardson model for pairing between like particles . .
And you have already written the first three sentences of the full article: neutron - proton ( @xmath0 ) pairing is a longstanding issue in nuclear structure @xcite . despite many efforts , the specific fingerprints of these correlations in existing nuclear data are not yet clear , nor the appropriate theoretical tools for their correct treatment . for many years
the theoretical framework commonly used to describe the @xmath0 pairing correlations was the generalized hfb approach @xcite . in this approach the @xmath0 pairing ,
both isovector and isoscalar , is treated simultaneously with neutron - neutron ( @xmath1 ) and proton - proton ( @xmath2 ) pairing ..
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however , although the generalized bcs approach treats on equal footing all type of pairing correlations , most of bcs calculations show that they rarely mix @xcite .
thus , in general , there are three bcs solutions which seem to exclude each other : one with @xmath1 and @xmath2 pairs ; the second , degenerate to the first in even - even @xmath3 nuclei , with isovector @xmath0 pairs ; and the third with isoscalar @xmath0 pairs .
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10,030 |
Suppose that you have an abstract for a scientific paper: we propose a new approach to theoretical description of doped cuprate like + @xmath0 and @xmath1 , assuming phase separation and treating it as inhomogeneous composite material , containing the dielectric and metallic stripe - like nanoparticles .
the formalism of effective medium theory is then applied for calculation of dielectric permittivity , optical and eels spectra of @xmath0 with @xmath2 varying in a wide range .
reasonable semi - quantitative agreement with experiment has been obtained even for the simplest version of the theory .
the model was found able to reproduce all essential features of optical conductivity @xmath3 and transmittance both for thin films ( m. suzuki , phys .
rev . * b 39 * , 2321 ( 1989 ) ) and bulk single - crystalline samples ( s. uchida _ et al . _
phys . rev .
* b 43 * , 7942 ( 1991 ) ) .
substantial difference in spectral and doping dependence of optical absorption for the thin - film and bulk samples is easily explained if only to assume different shape of metallic and dielectric regions in both materials .
new peaks in @xmath3 and absorption spectra , that emerge in the midinfrared range near @xmath4 and @xmath5 ev upon doping are attributed to geometrical ( mie s ) resonances .
overall , we point out that all main peculiarities of the doping effect on optical and eels spectra for cuprates including the spectral changes accompanying the insulator - to - metal transition can be explained rather prosaically by recognizing that the doping results in emergence of nanoscopic metallic stripe - like droplets
. high-@xmath6 cuprates .
inhomogeneity .
effective medium . .
And you have already written the first three sentences of the full article: high-@xmath6 superconductivity and other unconventional properties of doped quasi-2d cuprates remain a challenging and hot debated problem . as usual , the active @xmath7 planes in cuprates are considered as homogeneous systems , starting from one- , three- or multiband hubbard models .
often only in - plane @xmath8 basis set is taken into account and the well defined zhang - rice singlet ground state for doped holes is presumed . in frames of such theories
the dependence of various properties of copper oxides on doping are related to the rearrangements of hubbard bands . however there are clear experimental evidences in favour of intrinsic and generic inhomogeneous nature of the systems under consideration with well developed static and dynamic spatial inhomogeneities @xcite ..
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nonisovalent chemical substitution in insulating cuprates like @xmath0 and @xmath1 results in an increase of the energy of the parent phase and creates proper conditions for its competing with other , possibly metallic phases capable to provide an effective screening of the charge inhomogeneity potential . at the beginning ( nucleation regime )
a new phase appears in form of a somewhat like a metallic droplet in insulating matrix .
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10,031 |
Suppose that you have an abstract for a scientific paper: we have studied the fir/_mm _ spectrum of ir galaxies by combining iras photometry with new _ mm _ data on a complete southern iras galaxy sample .
the observed spectra and a dust model emphasize a dicothomy in the galaxy population : half of the objects with a lot of warm dust are characterized by higher values of the bolometric ( uv - fir ) luminosity , of the dust - to - gas mass ratio , of the dust optical depths and extinction , while those dominated by cold ( _ cirrus _ ) dust show opposite trends . from these data
we derive the _ mm _ luminosity function of galaxies and estimate their contribution to the sub-_mm _ background ( bkg ) . .
And you have already written the first three sentences of the full article: observations of diffuse dust in galaxies impact on some basic questions about their present structure and past history . in particular , are we missing significant amounts of luminous matter because of the effects of dust extinction ?
how much severe are the corresponding selection effects ? traditional approaches to investigate dust in galaxies rely on either _
( a ) _ indirect estimates based on dust extinction effects in the optical and near - ir , or _ ( b ) _ direct measurements of dust emission from fir / mm observations.
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. neither have provided conclusive results at the moment : the former method is based on model - dependent and controversial assumptions about the optical - ir spectrum of various galactic components , the latter still lacks a large enough statistical basis and suffers from the observational uncertainties of the sub-_mm_/_mm _ data .
we have tackled the question of the dust content of spirals by observing the 1.25 _ mm _ continuum emission from a complete sample of iras galaxies with the sest telescope .
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10,032 |
Suppose that you have an abstract for a scientific paper: we analyze the possibility of probing higgs couplings in the rare decays @xmath0 , @xmath1 being a vector quarkonium state .
these rare decays involve both gauge as well as the yukawa sectors and either of them can be potentially anomalous . moreover ,
as both @xmath1 and @xmath2 can decay into pair of charged leptons , they provide experimentally clean channels and future lhc runs should observe such decays .
we discuss origin of all possible contributions and their relative strengths in @xmath0 process .
we perform a model independent analysis and show how angular asymmetries can be used for probing higgs couplings in the rare decays , taking further decays of @xmath1 and @xmath2 to pair of leptons into account .
the angular asymmetries can play a significant role in probing higgs couplings to sm particles in both gauge and yukawa sectors . .
And you have already written the first three sentences of the full article: the atlas and cms collaborations at large hadron collider ( lhc ) have recently discovered a new bosonic resonance of mass around 125 gev @xcite .
measuring its coupling to different standard model ( sm ) particles and establishing its nature are going to be leading aims of future lhc runs .
although it is yet to be confirmed as sm higgs , in this paper we specify this resonance as higgs and denote it by @xmath3 ..
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any deviations from its sm nature should exhibit in its coupling to different particles .
anomalous couplings of higgs may come in both gauge and yukawa sectors . establishing the nature of
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10,033 |
Suppose that you have an abstract for a scientific paper: the low - mass end of the supermassive black hole mass function is unknown and difficult to determine . here
we discuss our successful program to find active nuclei of late type `` normal '' galaxies using x - ray detections and multiwavelength identifications .
we conclude that most of the _ chandra _ detected nuclear x - ray sources are agns .
we then outline methods of black hole mass determination when broad emission lines are unobservable .
address = department of astronomy , the ohio state university , 140 w 18th ave , columbus , oh 43210 , usa address = department of astronomy , the ohio state university , 140 w 18th ave , columbus , oh 43210 , usa address = herzberg institute of astrophysics , 5071 west saanich road , victoria , bc v8x 4m6 , canada address = inaf - osservatorio astronomico di roma , via frascati 33 , 00040 monteporzio catone ( roma ) , italy .
And you have already written the first three sentences of the full article: the local low - mass ( below @xmath0 @xmath1 ) supermassive black hole ( smbh ) mass function is not well known .
current estimates of the smbh mass function are based on host galaxy properties ( luminosity of the bulge or bulge stellar velocity dispersion @xmath2 ) and known scaling relationships between the mass @xmath3 of the smbh and these properties ( most prominently @xmath4 and @xmath5 ) .
these estimates can be widely discrepant with each other at the low - mass end ( see , for example , fig . 8 in @xcite ) ..
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much of the uncertainty arises because it is unknown how the scaling relationships extrapolate to very late - type and very low mass galaxies . yet
smbhs _ do _ exist in very late - type spirals , e.g.ngc 4395 , a spiral galaxy of type sdm , with @xmath6 @xmath1@xcite , and in very low mass galaxies , e.g. pox 52 , a dwarf galaxy , with @xmath6 @xmath1@xcite .
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10,034 |
Suppose that you have an abstract for a scientific paper: in this paper , firstly , some applications of hilbert matrix in image processing and cryptology are mentioned and an algorithm related to the hilbert view of a digital image is given . in section 2 ,
the new matrix domains are constructed and some properties are investigated . furthermore , dual spaces of new matrix domains are computed and matrix transformations are characterized . in last section , examples of transformations of new spaces are given .
[ section ] [ thm]proposition [ thm]example [ thm]corollary [ thm]definition [ thm]lemma [ thm]remark .
And you have already written the first three sentences of the full article: we consider the matrices @xmath0 and @xmath1 as follows : @xmath2 it is well known that these matrices are called the infinite hilbert matrix and the @xmath3 hilbert matrix , respectively .
a famous inequality of hilbert ( @xcite , section 9 ) asserts that the matrix @xmath0 determines a bounded linear operator on the hilbert space of square summable complex sequences . also , @xmath3 hilbert matrices are well known examples of extremely of ill - conditioned matrices . + frequently , hilbert matrices are used both mathematics and computational sciences . for examples , in image processing , hilbert matrices
are commonly used ..
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any @xmath4 array of natural numbers in the range @xmath5 $ ] for all @xmath6 can be viewed as a greyscale digital image .
+ we take the hilbert matrix @xmath1(@xmath3 matrix ) .
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Suppose that you have an abstract for a scientific paper: quantum memory is important to quantum information processing in many ways : a synchronization device to match various processes within a quantum computer , an identity quantum gate that leaves any state unchanged , and a tool to convert heralded photons to photons - on - demand .
in addition to quantum computing , quantum memory would be instrumental for the implementation of long - distance quantum communication using quantum repeaters .
the importance of this basic quantum gate is exemplified by the multitude of optical quantum memory mechanisms being studied : optical delay lines , cavities , electromagnetically - induced transparency , photon - echo , and off - resonant faraday interaction . here
we report on the state - of - the - art in the field of optical quantum memory , including criteria for successful quantum memory and current performance levels . .
And you have already written the first three sentences of the full article: quantum information science incorporates quantum principles into information processing and communication . amongst the most spectacular discoveries and conjectures ,
we know that quantum cryptography could enable information - theoretic secure communication through public channels @xcite , and quantum computing would efficiently solve certain computational problems that are believed to be intractable by conventional computing @xcite .
furthermore quantum dynamics becomes efficiently simulatable on a quantum computer @xcite ..
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the prototypical model of quantum information processing represents information as strings of qubits , and processing is effected by unitary quantum gates .
the qubit is a single - particle state in a two - dimensional hilbert space .
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10,036 |
Suppose that you have an abstract for a scientific paper: in the proposed model with interaction between dark energy and dark matter , we consider cosmological scenarios with different equations of state ( @xmath0 ) for dark energy . for both constant and variable equation of state ,
we analyze solutions for dark energy and matter in 7 variants of the model .
we investigate exact analytic solutions for @xmath1 constant equation of state , and several variants of the model for variable @xmath0 .
these scenarios are tested with the current astronomical data from type ia supernovae , baryon acoustic oscillations and the hubble parameter @xmath2 .
finally , we compare our interacting model with some known cosmological models . .
And you have already written the first three sentences of the full article: a dramatic change in the dynamic history of the universe happened since 1998 when observations from type ia supernovae @xcite claimed our universe to be expanding with certain acceleration .
this peculiar result was verified in several independent observations @xcite supporting the present accelerating phase of our universe . however , this observational prediction required a perfect theoretical explanation behind such a scenario , and finally , the cosmologists came up to the conclusion that our universe must contain some exotic components with large negative pressure . in equation of state
( hereafter we call it as eos ) of these components , the ratio of total pressure to the total energy density satisfies the condition `` @xmath3 '' ..
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the components with this condition are dubbed `` dark energy '' to differ from other normal matter components ( with positive pressure ) in our universe . however , among the several dark energy candidates , the best description for our present accelerating universe is the @xmath4cdm model due to its satisfactory agreement with the current astronomical data we have . still , the model suffers with two very known serious problems : the first one , known as the cosmological constant problem , is in huge ( of the order 10@xmath5 ) difference between the observed value of the cosmological constant and its predicted value by the quantum field theory @xcite .
the second problem , the cosmic coincidence problem @xcite , is in surprising fact , that the dark energy density has the same order of magnitude as the matter density in our universe today , though these two quantities have different laws of evolution . on the other hand ,
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10,037 |
Suppose that you have an abstract for a scientific paper: we describe an approach , based on direct numerical solution of the usadel equation , to finding stationary points of the free energy of superconducting nanorings .
we consider both uniform ( equilibrium ) solutions and the critical droplets that mediate activated transitions between them . for the uniform solutions ,
we compute the critical current as a function of the temperature , thus obtaining a correction factor to bardeen s 1962 interpolation formula . for the droplets , we present a metastability chart that shows the activation energy as a function of the temperature and current .
we also discuss the nature of the bifurcation point at which the droplet merges with the uniform solution . .
And you have already written the first three sentences of the full article: destruction of superconductivity in thin wires at high currents is a classic topic .
bardeen s 1962 review @xcite summarizes the state of the art at the time . in particular
, it presents an interpolation formula i_c(t ).
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i_c(0 ) [ 1 - ( t / t_c)^2]^3/2 [ bardeen ] for the critical ( depairing ) current as a function of the temperature . an important development subsequent to bardeen s article has been little s work @xcite , which emphasized the role of large thermal fluctuations ( phase slips ) as a cause for transition to the normal state at currents below @xmath0 . experimental studies of this switching transition have developed fast in recent years . on the theoretical side ,
a study of thermal phase slips begins with identifying the saddle - point of the free energy ( the critical droplet ) that determines the activation barrier .
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Suppose that you have an abstract for a scientific paper: we have made a detailed study of the ground - state properties of nuclei in the light mass region with atomic numbers z=10 - 22 in the framework of the relativistic mean - field ( rmf ) theory .
the nonlinear @xmath0 model with scalar self - interaction has been employed .
the rmf calculations have been performed in an axially deformed configuration using the force nl - sh .
we have considered nuclei about the stability line as well as those close to proton and neutron drip lines .
it is shown that the rmf results provide a good agreement with the available empirical data .
the rmf predictions also show a reasonably good agreement with those of the mass models . it is observed that nuclei in this mass region are found to possess strong deformations and exhibit shape changes all along the isotopic chains .
the phenomenon of the shape coexistence is found to persist near the stability line as well as near the drip lines .
it is shown that the magic number n=28 is quenched strongly , thus enabling the corresponding nuclei to assume strong deformations .
nuclei near the neutron and proton drip lines in this region are also shown to be strongly deformed .
= 16 true cm = 23.5 true cm = -1.0 true cm = cmbx10 scaled2 .
And you have already written the first three sentences of the full article: the advent of radioactive beams and emergence of several facilities to produce these has provided a possibility to study the structure and properties of nuclei far away from those known to us so far @xcite .
these so - called `` exotic '' nuclei transcend the valley of stability and possess the extreme ratios of protons to neutrons on both the sides .
an increase in each unit of isospin makes nuclei vulnerable to decay and consequently nuclei in the extreme domains of the periodic table are far short - lived ..
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an access to these nuclei with a view to study their structure and properties poses a serious experimental challenge . at the same time
, a comprehension of the nuclear properties in such areas is essential .
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Suppose that you have an abstract for a scientific paper: an analytical model of a single - atom electron source is presented , where electrons are created by near - threshold photoionization of an isolated atom .
the model considers the classical dynamics of the electron just after the photon absorption , i.e. its motion in the potential of a singly charged ion and a uniform electric field used for acceleration . from closed expressions for the asymptotic transverse electron velocities and trajectories ,
the effective source temperature and the virtual source size can be calculated .
the influence of the acceleration field strength and the ionization laser energy on these properties has been studied . with this model ,
a single - atom electron source with the optimum electron beam properties can be designed .
furthermore , we show that the model is also applicable to ionization of rubidium atoms , and thus also describes the ultracold electron source , which is based on photoionization of laser - cooled alkali atoms . .
And you have already written the first three sentences of the full article: single - atom electron emitters are the closest one can get to the ideal of a point - like electron source .
they are capable of producing beams with nearly full spatial coherence , i.e. approaching the heisenberg uncertainty limit @xmath0 , with @xmath1 the root - mean - square ( rms ) transverse beam size and @xmath2 the rms transverse momentum spread ; this was recently demonstrated experimentally @xcite .
currents in the range of tens of na can be generated in this way , resulting in ultra - bright electron beams ..
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the fabrication of single - atom emitters , however , involves complicated preparation methods , usually based on the formation of a tiny protrusion on the apex of a 10100 nm hemispherical metallic tip @xcite .
after proper treatment the protrusion forms a sharp structure with a single atom on top , which sprays a narrow beam of electrons when an external field is applied .
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Suppose that you have an abstract for a scientific paper: we have applied a double decoupled localized level anderson - newns hamiltonian to the analysis of surface effects upon the ionized fraction @xmath0 of sputtered atoms from a metal surface .
electronic excitations , induced in the conduction band by the transient formation of quasi molecular systems , between substrate and emitted atoms , in the collision cascade generated by the primary incident beam , have been explicitly included into an instantaneous transition matrix peaked at the fermi level of the material .
the interaction dynamics seem to take place over two different time scales , one related to sputtered atom trajectories and the other to recoiled substrate particles .
finite temperature calculations have suggested , at very low ejection energies , a power law dependence of the final charge state of the sputtered beam on its detected velocity .
this result is in agreement , in the zero temperature limit , with some previously published papers and its validity has been compared to other theoretical outcomes and tested on sims data .
_ pacs _ : 79.20.-m , 71.23.an _ keywords _ : ion - solid interactions ; ion emission ; metallic surfaces ; models of non equilibrium phenomena ; scattering and sputtering . and and .
And you have already written the first three sentences of the full article: resonant electron transfer during sputtering of atoms and molecules from metal surfaces has been a very interesting subject in relation to secondary ion mass spectroscopy ( sims ) where the knowledge of ionization and neutralization rates is essential for many quantitative analyses .
the theory of such processes should encompass a detailed description of charge exchanges in the collision cascade to the outgoing atom or atomic cluster .
in fact , to make this complicated problem tractable , a basic model has been formulated in terms of a single orbital parametrically time - dependent anderson - newns hamiltonian @xcite-@xcite , in which the effects of the bombardment , including the substrate motion , the electronic excitations generated and the physical and chemical consequences of the void produced by the ejected particle have been neglected ..
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many experimental results have been reproduced in this way @xcite-@xcite which is common to both sims and atomic surface scattering . yet the need for a more comprehensive theory of surface influences in sputtering has led to a generalized approach @xcite in which the substrate dynamics have been modeled with locally time - dependent perturbations created during the collision and acting within the first layers of the surface region . in a first simplified treatment @xcite a one - body time dependent scattering potential , localized in the vicinity of the emission site , was added to the basic hamiltonian and _ direct _ ( i.e. non mediated by the atomic localized level ) electronic excitations , created in the conduction band by this new term , were explicitly considered in the evaluation of the ionized fraction . although the average lifetime of these excitations is believed to be rather short on the time - scale of the emission trajectory @xcite , their contribution to the final charge state of secondary ions becomes important at very low emission energies where the ionization probability calculated from the basic theory exhibits an exponential dependence on the inverse of the _ average _ outgoing velocity of sputtered particles @xcite . in a recent paper @xcite
, an exact formal solution of the two potential problem formulated in ref.@xcite has been obtained confirming more rigorously that , in the velocity regime typically observed in many sims experiments , the basic hopping mechanism may be negligible with respect to surface induced excitations , at least if they can be represented in the form of a one - body scattering potential . in the present article , we have proposed a more accurate form of the sputtering potential combining the above mentioned impurity scattering contribution with a hopping resonant interaction due to a second discrete state embedded in the conduction band ( sec.2 ) .
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10,041 |
Suppose that you have an abstract for a scientific paper: motivated by applications in optics and acoustics we develop a dynamical - system approach to describe absorption in chaotic systems .
we introduce an operator formalism from which we obtain ( i ) a general formula for the escape rate @xmath0 in terms of the natural conditionally - invariant measure of the system , ( ii ) an increased multifractality when compared to the spectrum of dimensions @xmath1 obtained without taking absorption and return times into account , and ( iii ) a generalization of the kantz - grassberger formula that expresses @xmath2 in terms of @xmath0 , the positive lyapunov exponent , the average return time , and a new quantity , the reflection rate .
simulations in the cardioid billiard confirm these results .
* published as : phys .
rev .
lett .
111 , 144101 ( 2013 ) * the design of concert halls was probably the first problem in which the importance of the partial absorption of energy along trajectories was fully recognized @xcite . in berry s elegant formulation , confinement is needed _ to prevent sound from being attenuated by radiating into the open air .
but if the confinement were perfect , that is , if the walls of the room were completely reflecting , sounds would reverberate forever . to avoid these extremes , the walls in a real room
must be partially absorbing _ @xcite . besides acoustics @xcite , chaotic dynamical systems in which trajectories are partially absorbed appear nowadays in an increasing number of different areas @xcite , ranging from optics ( microlasers ) @xcite to environmental sciences ( resetting mechanism ) @xcite and quantum chaos @xcite .
the analogy of the decay of the sound intensity with the survival probability of transient chaos has early been recognized @xcite , here we add that a sharp distinction between the attenuation of energy ( absorption ) and the escape of particles ( transport ) is necessary
. a seemingly unrelated problem is monitoring continuous time in flows represented by discrete - time maps....
And you have already written the first three sentences of the full article: here we evaluate different approximants from the escape rate formula
( 5 ) in the main text for the general case of non - constant reflection coefficient @xmath24 and non - zero exit region @xmath98 .
we write the main formula as @xmath216 and the corresponding cumulant expansion is @xmath217,\ ] ] where @xmath218 ..
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up to second order in @xmath219 , eq .
( [ eq.cumdef ] ) yields @xmath220 .
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10,042 |
Suppose that you have an abstract for a scientific paper: we analyze the sudbury neutrino observatory ( sno ) and super - kamiokande ( sk ) data on charged current ( cc ) , neutral current ( nc ) and neutrino electron elastic scattering ( es ) reactions to constrain the leading weak axial two - body current parameterized by @xmath0 this two - body current is the dominant uncertainty of every low energy weak interaction deuteron breakup process , including sno s cc and nc reactions .
our method shows that the theoretical inputs to sno s determination of the cc and nc fluxes can be self - calibrated , be calibrated by sk , or be calibrated by reactor data .
the only assumption made is that the total flux of active neutrinos has the standard @xmath1 spectral shape ( but distortions in the electron neutrino spectrum are allowed ) .
we show that sno s conclusion about the inconsistency of the no - flavor - conversion hypothesis does not contain significant theoretical uncertainty , and we determine the magnitude of the active solar neutrino flux . .
And you have already written the first three sentences of the full article: recent conclusive results from the sudbury neutrino observatory ( sno ) have established the existence of non - electron active neutrino components in the @xmath1 solar neutrino flux @xcite and hence have given a strong evidence for neutrino oscillation .
these results are based on the three reactions measured by sno to detect the @xmath1 solar flux @xmath2 the charged current reaction ( cc ) is sensitive exclusively to electron - type neutrinos , while the neutral current reaction ( nc ) is equally sensitive to all active neutrino flavors ( @xmath3 ) .
the elastic scattering reaction ( es ) is sensitive to all active flavors as well , but with reduced sensitivity to @xmath4 and @xmath5 ..
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detection of these three reactions allows sno to determine the electron and non - electron active neutrino components of the solar flux , and it is then obvious that the cross sections for these three reactions are important inputs for sno .
the cross sections for all three reactions are determined from theory , but the cc and nc cross sections involve nuclear - physics complexities not present in the es interaction description .
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10,043 |
Suppose that you have an abstract for a scientific paper: at small @xmath0 , the gluon distribution dominates the nuclear wave function . the increase needs to be tamed in avoid violating unitarity constraints .
the most efficient way to study this in colliders is through @xmath1+a collisions as the nucleus is an efficient amplifier of the physics of high gluon densities . to this end
, there are proposals to build an @xmath1+a machine in the usa which would operate over a large range of energies and masses .
these studies would also allow an in - depth comparison to a+a collisions where recent results have given tantalising hints of a new state of matter produced with partonic degrees of freedom .
as gluon interactions are the dominant source of hard probes , they themselves must be understood before the results are explained quantitatively . .
And you have already written the first three sentences of the full article: r0.5 although all of the unique features of qcd are determined by the self - interactions of gluons , currently , very little is known about their space- and momentum - distributions in nuclei . as the gluonic degrees of freedom are missing in the hadronic spectrum , in order to study the gluon structure of the nuclear wave - function , high - energy probes of the nucleus
are required . whilst @xmath2+a collisions provide excellent information on the gluon properties ,
as many observables require gluons to participate at the leading order , interpreting the data is difficult due to the soft colour interactions between the @xmath2 and the a before the hard scattering takes place ..
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therefore , the most desirable collision system to probe the gluon properties are lepton+a collisions .
the lepton beams interact with the electrically charged quarks in a process known as deep - inelastic scattering ( dis ) and the gluonic part of the nuclear wave - function modifies the interaction in ways which allow the extraction of the gluon properties .
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Suppose that you have an abstract for a scientific paper: recently , a self - contained trajectory - based formulation of non - relativistic quantum mechanics was developed [ ann .
phys . * 315 * , 505 ( 2005 ) ; chem . phys . * 370 * , 4 ( 2010 ) ; j. chem . phys . * 136 * , 031102 ( 2012 ) ] , that makes no use of wavefunctions or complex amplitudes of any kind .
quantum states are represented as ensembles of real - valued quantum trajectories that extremize a suitable action . here , the trajectory - based approach is developed into a viable , generally covariant , relativistic quantum theory for single ( spin - zero , massive ) particles .
central to this development is the introduction of a new notion of global simultaneity for accelerated particles together with basic postulates concerning probability conservation and causality .
the latter postulate is found to be violated by the klein - gordon equation , leading to its well - known problems as a single - particle theory .
various examples are considered , including the time evolution of a relativistic gaussian wavepacket . .
And you have already written the first three sentences of the full article: in this document , we develop a new formulation of single - particle relativistic quantum mechanics . traditionally , the formulation of quantum mechanics proceeds via a set of postulates,@xcite which we do not find it necessary to repeat here .
we do note , however , that the order , precise content , and even total number of quantum postulates , vary from one treatment to the next . this situation might be taken as an indication of the controversy or uncertainty that still exists particularly around those postulates having to do with quantum measurement .
the latter are especially nettlesome in the context of relativistic quantum mechanics where , e.g. , it may not be entirely clear how to reconcile the `` instantaneous '' collapse of the wavefunction with subluminal propagation ..
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on the other hand , the traditional quantum treatments all do agree on the first and most important postulate
that the state of a system be completely described by the quantum wavefunction , @xmath0 .
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10,045 |
Suppose that you have an abstract for a scientific paper: we derive from a microscopic model the effective theory of nematic order in a system with a spontaneous quantum anomalous hall effect in two dimensions . starting with a model of two - component fermions ( a spinor field ) with a quadratic
band crossing and short range four - fermion marginally relevant interactions we use a @xmath0 expansion and bosonization methods to derive the effective field theory for the hydrodynamic modes associated with the conserved currents and with the local fluctuations of the nematic order parameter .
we focus on the vicinity of the quantum phase transition from the isotropic mott chern insulating phase to a phase in which time - reversal symmetry breaking coexists with nematic order , the nematic chern insulator .
the topological sector of the effective field theory is a bf / chern - simons gauge theory .
we show that the nematic order parameter field couples with the maxwell - type terms of the gauge fields as the space components of a locally fluctuating metric tensor .
the nematic field has @xmath1 dynamic scaling exponent .
the low - energy dynamics of the nematic order parameter is found to be governed by a berry phase term . by means of a detailed analysis of the coupling of the spinor field of the fermions to the changes of their local frames originating from long - wavelength lattice deformations
we calculate the hall viscosity of this system and show that in this system it is not the same as the berry phase term in the effective action of the nematic field , but both are related to the concept of torque hall viscosity which we introduce here . .
And you have already written the first three sentences of the full article: the theory of topological phases of matter has been a central problem in condensed matter physics since the discovery of the quantum hall effects@xcite in two - dimensional electron gases ( 2deg ) in large magnetic fields .
the precisely observed ( quantized or fractional ) values of the hall conductance is a manifestation of the fact that it is a topological invariant of the incompressible fluid.@xcite the fractional quantum hall fluids , on the other hand , are explained by the universal properties encoded in the structure of their wave functions@xcite whose excitations ( vortices ) carry fractional charge and fractional statistics.@xcite the robustness of these properties a consequence of their topological character .
in addition to having fractionalized excitations , these topological fluids have a ground state degeneracy which depends on the topology of the surface on which they reside , which is not a consequence of the spontaneous breaking of any global symmetry.@xcite the universal behavior of these topological fluids is encoded in an effective low - energy , the chern - simons gauge theory.@xcite there is now a growing body of ( mostly theoretical ) evidence that such topological phases of matter exist in several models of frustrated quantum antiferromagnets@xcite and in quantum dimer models.@xcite the recent discovery of topological insulators@xcite has opened a new arena in which these ideas play out . interacting versions of simple models of topological chern insulators , such as the haldane model,@xcite have topological phases with fractionalized excitations.@xcite an interesting question is the interlay and possible coexistence of topological order and spontaneous symmetry breaking . for some filling fraction the 2deg.
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is known to have a ferromagnetic quantum hall ground state,@xcite in which spin rotational symmetry is spontaneously broken .
also , a state with a nematic `` valley '' order has also been seen in quantum hall fluids on misoriented samples.@xcite on the other hand , experiments in the 2deg in the second landau level found a nematic state in a regime in which the fractional ( and integer ) quantum hall effect is absent.@xcite in this phase the 2deg is an uniform gapless electron fluid with a spontaneously broken spatial rotational symmetry.@xcite recent experiments by xia and coworkers found that the 2deg in the first landau level in tilted magnetic fields has a strong tendency to break rotational invariance inside an incompressible fractional quantum hall laughlin state.@xcite although in the the experiments rotational invariance is broken explicitly by the tilted magnetic field , the temperature dependence of the transport anisotropy suggest that this state has a large nematic susceptibility and may be close to a phase transition to a nematic state .
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10,046 |
Suppose that you have an abstract for a scientific paper: a two - component ( soft + hard ) model ( tcm ) of hadron production in yields and spectra derived from the charge - multiplicity dependence of 200 gev _
p - p _ collisions at the relativistic heavy ion collider ( rhic ) is extended to describe _ p - p _ spectrum data from the large hadron collider ( lhc ) up to 13 tev .
the lhc data include spectrum ratios that provide only partial information on the tcm .
the lhc ratio method is first applied to well - understood rhic spectrum data to derive an algebraic link between spectrum ratios and the full tcm .
lhc spectrum ratios are then analyzed to obtain the collision - energy dependence of isolated soft and hard tcm spectrum components over three orders of magnitude .
the energy dependence of the spectrum soft component is a new result suggesting a relation to gribov diffusion .
the spectrum hard component varies simply with qcd parameter @xmath0 and is quantitatively consistent with minimum - bias jet spectra .
some aspects of the form of the hard component on transverse momentum are found to be multiplicity dependent , possibly indicating bias of the underlying jet spectrum by an imposed event - multiplicity condition . .
And you have already written the first three sentences of the full article: a two - component ( soft + hard ) model ( tcm ) of hadron production near mid - rapidity from 200 gev collisions in terms of longitudinal projectile - nucleon dissociation and transverse minimum - bias ( mb ) dijet production derived from the charge - multiplicity dependence of spectra @xcite has been extended recently to consider the dependence of -integral angular correlations @xcite . in that study an analysis of new high - statistics spectra
was observed to be quantitatively consistent with a similar analysis completed ten years earlier .
analysis of 2d angular correlations revealed a significant nonjet quadrupole component as a novel aspect of collisions ..
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the dependence of yields , spectra and correlations has played a key role in establishing ( a ) the nature of hadron production mechanisms in collisions and ( b ) that the dijet contribution to spectra is quantitatively consistent with qcd expectations @xcite .
the phenomenology of collision data serves as an essential reference for high - energy and collisions , specifically regarding claims of novel physical mechanisms such as formation of a quark - gluon plasma @xcite or possible manifestations of hydrodynamic flows ( `` collectivity '' ) even in small collision systems @xcite .
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Suppose that you have an abstract for a scientific paper: we describe a non - perturbative determination of @xmath0 using correlators containing the axial - vector and pseudoscalar currents at zero and non - zero momentum .
we apply the method of bhattacharya et al to extract @xmath0 from the requirement that the ratio of appropriate correlators for the pcac relation becomes independent of time in the excited state region .
we find that the result depends strongly on the order of the derivatives used in the pcac relation .
we also find that , using the lowest order derivatives , we can not get a consistent value of @xmath0 between zero and non - zero momentum cases .
the @xmath0 values that we obtain as we improve the derivatives are consistent and decrease in magnitude heading towards the perturbative result . .
And you have already written the first three sentences of the full article: the use of symanzik - improved lattice actions and matrix elements is widespread .
however , with each improvement term added the corresponding coefficient must be determined to enable discretisation effects to be reduced to the desired level .
considering the light hadron spectrum and matrix elements , the relevant @xmath1 improvement coefficients are , for the most part , only known to @xmath2-loop in perturbation theory . a nonperturbative determination of these coefficients is desirable and may be simpler than performing higher loop perturbative calculations ..
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the alpha collaboration , using schrdinger functional techniques , have calculated several @xmath1 improvement coefficients nonperturbatively . in most cases agreement
is found with @xmath2-loop ( tadpole - improved ) perturbation theory , or the discrepancy is consistent with estimates of the size of omitted higher orders in @xmath3 ( albeit in some cases assuming a slow convergence of the perturbative series ) .
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Suppose that you have an abstract for a scientific paper: the recent burst in the number of radii measurements of very low - mass stars from eclipsing binaries and interferometry of single stars has opened more questions about what can be causing the discrepancy between the observed radii and the ones predicted by the models .
the two main explanations being proposed are a correlation between the radius of the stars and their activity levels or their metallicities .
this paper presents a study of such correlations using all the data published to date .
the study also investigates correlations between the radii deviation from the models and the masses of the stars .
there is no clear correlation between activity level and radii for the single stars in the sample .
those single stars are slow rotators with typical velocities @xmath0 @xmath1 3.0 km @xmath2 .
a clear correlation however exists in the case of the faster rotating members of binaries .
this result is based on the of x - ray emission levels of the stars .
there also appears to be an increase in the deviation of the radii of single stars from the models as a function of metallicity , as previously indicated by berger et al .
( 2006 ) .
the stars in binaries do not seem to follow the same trend .
finally , the baraffe et al .
( 1998 ) models reproduce well the radius observations below 0.300.35 @xmath3 , where the stars become fully convective , although this result is preliminary since almost all the sample stars in that mass range are slow rotators and metallicities have not been measured for most of them .
the results in this paper indicate that stellar activity and metallicity play an important role on the determination of the radius of very low - mass stars , at least above 0.35@xmath3 . .
And you have already written the first three sentences of the full article: the two most fundamental parameters of a star are its mass and its radius . for a given stellar mass ,
models try to reproduce the radius of the star by implementing the best known stellar interior and atmospheric physics . for stars more massive than the sun , convective interior and radiative atmosphere models reproduce well the observations ( e.g. andersen 1991 , 1997 ) .
the atmospheres of these stars are dominated by atomic species and their interiors can be closely modeled as an ideal gas ..
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as detailed in the physics of low - mass stars review paper by chabrier & baraffe ( 2000 ) , below 1@xmath3 we enter a new physics domain where molecular compounds begin to form in the atmospheres of the stars as their effective temperature drops , and convection expands to the outer layers of the star , until the objects become fully convective below @xmath4 0.35 @xmath3 .
in addition , the interior of the stars becomes denser , and the conditions begin to resemble those of a partially degenerate plasma .
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Suppose that you have an abstract for a scientific paper: let @xmath0 be an arbitrary real @xmath1-surface , with or without boundary , contained in a hypersurface @xmath2 of @xmath3 , with @xmath0 and @xmath2 of class @xmath4 , where @xmath5 . if @xmath0 is totally real except at finitely many complex tangencies which are hyperbolic in the sense of e. bishop and if the union of separatrices is a tree of curves without cycles , we show that every compact @xmath6 of @xmath0 is cr- , @xmath7- and @xmath8-removable ( theorem 1.3 ) . our purely local techniques enable us to formulate substantial generalizations of this statement , for the removability of closed sets in totally real @xmath9-codimensional submanifolds contained in generic submanifolds of cr dimension @xmath9 . = 0.35
cm * table of contents * * part i 1 . * * part ii 45 . * .
And you have already written the first three sentences of the full article: in the past fifteen years , remarkable progress has been made towards the understanding of the holomorphic extendability properties of cr functions .
at the origin of this development , the most fundamental achievement was the deep discovery , due to the effort of numerous mathematicians , that the so - called _ cr orbits _ are the adequate underlying objects for the semi - local cr analysis on a general embedded cr manifold .
as an independent and now established theory in several complex variables , one may find a precise correspondence between such orbits and progressively attached analytic discs covering a thick part of the envelope of holomorphy of cr manifolds , _ cf ..
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_ @xcite , @xcite , @xcite , @xcite , @xcite , @xcite , @xcite , @xcite and @xcite for a recent synthesis . within this framework
, it became mathematically accessible to endeavour the general study of removable singularities on embedded cr manifolds @xmath10 of arbitrary cr dimension and of arbitrary codimension , not necessarily being the boundaries of ( strictly ) pseudoconvex domains .
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10,050 |
Suppose that you have an abstract for a scientific paper: low - luminosity active galactic nuclei ( llagns ) represent the bulk of the agn population in the present - day universe and they trace the low - level accreting supermassive black holes . in order to probe the accretion and jet physical properties in llagns as a class , we model the broadband radio to x - rays spectral energy distributions ( seds ) of 21 llagns in low - ionization nuclear emission - line regions ( liners ) with a coupled accretion - jet model .
the accretion flow is modeled as an inner adaf outside of which there is a truncated standard thin disk .
we find that the radio emission is severely underpredicted by adaf models and is explained by the relativistic jet .
the origin of the x - ray radiation in most sources can be explained by three distinct scenarios : the x - rays can be dominated by emission from the adaf , or the jet , or the x - rays can arise from a jet - adaf combination in which both components contribute to the emission with similar importance . for 3 objects both the jet and adaf fit
equally well the x - ray spectrum and can be the dominant source of x - rays whereas for 11 llagns a jet - dominated model accounts better than the adaf - dominated model for the data .
the individual and average sed models that we computed can be useful for different studies of the nuclear emission of llagns . from the model
fits , we estimate important parameters of the central engine powering llagns in liners , such as the mass accretion rate and the mass - loss rate in the jet and the jet power - relevant for studies of the kinetic feedback from jets . .
And you have already written the first three sentences of the full article: one of the central paradigms in extragalactic astronomy is that today s galaxies host supermassive black holes ( smbhs ) at their centers and have a symbiotic evolution with them @xcite .
the central black holes seeded in proto - galaxies at high redshift grow in mass during cosmic history through a sequence of mergers of massive black holes and accretion episodes ( e.g. , @xcite ) .
the massive black holes grow in such a way that they co - evolve with the galactic bulges @xcite but do not seem to do so with the galaxy disks @xcite or dark matter haloes @xcite ..
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the growth of smbhs is dominated by the quasar phase @xcite during which they accrete from their large gas reservoir via geometrically thin accretion disks which are radiatively efficient @xcite as suggested by different lines of evidence @xcite .
the quasar population has a strong cosmological evolution with its density decreasing by a factor of @xmath0 from @xmath1 where the density reaches its peak to the present time ( e.g. , @xcite ) . in the present - day universe ,
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10,051 |
Suppose that you have an abstract for a scientific paper: we present keck laser guide star observations of two t2.5 dwarfs 2mass j11061197 + 2754225 and 2mass j14044941@xmath03159329 using nirc2 on keck - ii and find 2mass j14044941@xmath03159329 to be a 0@xmath113 binary .
this system has a secondary that is 0.45 mags brighter than the primary in @xmath2-band but 0.49 mags fainter in @xmath3-band and 1.13 mags fainter in @xmath4-band .
we use this relative photometry along with near - infrared synthetic modelling performed on the integrated light spectrum to derive component types of t1 @xmath5 1 for the primary and t5 @xmath5 1 for the secondary .
optical spectroscopy of this system obtained with magellan / ldss-3 is also presented .
this is the fourth l / t transition binary to show a flux reversal in the 11.2 @xmath6 m regime and this one has the largest flux reversal . unless the secondary is itself an unresolved binary , the @xmath2-band magnitude difference between the secondary and primary shows that the @xmath2-band `` bump '' is indeed a real feature and not an artifact caused by unresolved binarity . .
And you have already written the first three sentences of the full article: as brown dwarfs cool and pass through the l / t spectral class boundary , their spectral morphologies transition from red near - infrared ( nir ) colors of the l dwarf class , caused by condensate dust in their photospheres , to blue nir colors of the t dwarf class , where their photospheres are relatively clear of dust .
this transition is rapid , as implied by the nearly flat effective temperature scale around 1400 k for nir l7t5 dwarfs ( , bottom panel of fig .
7 in that paper ) . within this transition ,.
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a remarkable brightening in @xmath2-band ( @xmath7m@xmath8 1 ) from spectral types @xmath9t1@xmath0t5 , known as the @xmath2-band `` bump '' @xcite , has been noted .
two withstanding mechanisms to explain this brightening have been suggested : ( 1 ) the `` patchy clouds '' model proposed by @xcite ( see also @xcite ) , suggesting that the break - up of clouds in the atmosphere allows hot flux from inner layers to emerge ( analogous to the 5 @xmath6 m hot spots of jupiter ) , and ( 2 ) the `` sudden downpour '' model proposed by @xcite , suggesting that the dust clouds suddenly condense out due to an increase in sedimentation efficiency .
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10,052 |
Suppose that you have an abstract for a scientific paper: we present _ chandra _ observations of the radio - quiet broad absorption line ( bal ) qso pg 1254 + 047 .
we find that it is a weak x - ray source , with a total of @xmath0 photons measured in 36 ksec across the observed energy range @xmath1 kev .
its x - ray weakness is consistent with the known correlation between @xmath2 and the strength of the uv absorption lines .
the spectral energy distribution suggests that pg 1254 + 047 is intrinsically x - ray weak , in addition to being heavily x - ray absorbed .
the x - ray absorption column density is @xmath3 @xmath4 for neutral gas , while the intrinsic ( unabsorbed ) emission spectrum has @xmath5 .
the data are fit best by including an ionized ( rather than neutral ) absorber , with column density @xmath6 @xmath4 .
the degree of ionization is consistent with the uv bals , as is the total column density if the strongest uv lines are saturated .
if the x - ray absorber forms in a wind that is radiatively accelerated to the bal velocities , then the wind must be launched from a radius of about @xmath7 cm with a mass loss rate of @xmath8 m@xmath9 yr@xmath10 . .
And you have already written the first three sentences of the full article: almost all quasi - stellar objects ( qsos ) are x - ray sources . the reprocessing of the x - rays by intervening matter along the line - of - sight to the qso imprints informative features on the resulting spectrum ( e.g. , turner 1991 ) .
x - ray absorption studies provide an important tool to determine the physical and chemical state of the gas associated with qsos ( e.g. , netzer 1996 ) .
a subclass of qsos that have interesting x - ray properties in terms of continuum strength and absorption are the broad absorption line ( bal ) qsos ( foltz et al ..
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1990 ; weymann et al .
they display broad ( fwhm @xmath11 km s@xmath10 ) absorption lines in the rest - frame ultraviolet ( uv ) , which originate in an outflow of matter from the central engine of the qso .
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10,053 |
Suppose that you have an abstract for a scientific paper: laser guide star systems based on rayleigh scattering require some means to deal with the flash of low altitude laser light that follows immediately after each laser pulse . these systems also need a fast shutter to isolate the high altitude portion of the focused laser beam to make it appear star - like to the wavefront sensor .
we describe how these tasks are accomplished with unisis , the rayleigh laser guided adaptive optics system at the mt .
wilson observatory 2.5-m telescope .
we use several methods : a 10,000 rpm rotating disk , dichroics , a fast sweep and clear mode of the ccd readout electronics on a 10 @xmath0s timescale , and a pockel s cell shutter system .
the pockel s cell shutter would be conventional in design if the laser light were naturally polarized , but the unisis 351 nm laser is unpolarized .
so we have designed and put into operation a dual pockel s cell shutter in a unique bow tie arrangement . .
And you have already written the first three sentences of the full article: the unisis rayleigh laser guide star system has been commissioned as described in @xcite .
the system is built around a 30 watt excimer laser that emits short 90 mj pulses of 351 nm light at rates up to 333 hz .
these pulses are projected in the `` full- aperture broadcast '' mode and are focused in the stratosphere at an altitude of @xmath120 km above mean sea level ( @xmath118 km above the telescope ) ..
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immediately after the outgoing pulse of laser light hits the telescope primary mirror , a bright flash of low altitude rayleigh scattered light fills the near - field of the telescope .
as described below , the science cameras can be shielded from this near - field burst of light by dichroics because the projection method a 10,000 rpm rotating glass disk blocks the adaptive optics system from seeing a large fraction of this light in the first few microseconds after the laser pulse .
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10,054 |
Suppose that you have an abstract for a scientific paper: each of two players , by turns , rolls a dice several times accumulating the successive scores until he decides to stop , or he rolls an ace .
when stopping , the accumulated turn score is added to the player account and the dice is given to his opponent .
if he rolls an ace , the dice is given to the opponent without adding any point .
in this paper we formulate this game in the framework of competitive markov decision processes ( also known as _ stochastic games _ ) , show that the game has a value , provide an algorithm to compute the optimal minimax strategy , and present results of this algorithm in three different variants of the game .
* keywords : * competitive markov processes , stochastic games , dice games , minimax strategy .
* ams msc : * 60j10 , 60g40 , 91a15 .
And you have already written the first three sentences of the full article: consider a two - players dice game in which players accumulate points by turns with the following rules .
the player who reaches a certain fixed number of points is the winner of the game . in his turn
each player rolls the dice several times until deciding to stop or rolling an ace . if he decides to stop the accumulated successive scores are added to his account ; while if he rolls an ace no additional points are obtained . as a first approach to find optimal strategies for this game.
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roters @xcite studied the optimal stopping problem corresponding to the maximisation of the expected score in one turn .
the optimal solution is a good way of minimising the number of turns required to reach the objective .
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10,055 |
Suppose that you have an abstract for a scientific paper: in this work we have studied the possibility of obtaining cosmic acceleration in brans - dicke theory with varying or constant @xmath0 ( brans- dicke parameter ) and with or without self - interacting potential , the background fluid being barotropic fluid or generalized chaplygin gas . here
we take the power law form of the scale factor and the scalar field .
we show that accelerated expansion can also be achieved for high values of @xmath0 for closed universe . .
And you have already written the first three sentences of the full article: recent measurements of redshift and luminosity - distance relations of type ia supernovae indicate that the expansion of the universe is accelerating [ 1 , 2 ] .
this observation gives rise to the search for a matter field , which can be responsible for accelerated expansion .
there are several proposals regarding this , _ cosmological constant , quintessence , dark energy _ [ 3 - 5 ] being some of the competent candidates ..
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however , most of these models fit only to spatially flat @xmath1 friedmann - robertson - walker model [ 6 ] , though a few models [ 7 ] work for open universe ( @xmath2 ) also .
brans- dicke ( bd ) theory has been proved to be very effective regarding the recent study of cosmic acceleration [ 8 ] .
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10,056 |
Suppose that you have an abstract for a scientific paper: we consider a model dissipative quantum - mechanical system realized by coupling a quantum oscillator to a semi - infinite classical string which serves as a means of energy transfer from the oscillator to the infinity and thus plays the role of a dissipative element .
the coupling between the two quantum and classical parts of the compound system is treated in the spirit of the mean - field approximation and justification of the validity of such an approach is given .
the equations of motion of the classical subsystem are solved explicitly and an effective _ dissipative _ schrdinger equation for the quantum subsystem is obtained .
the proposed formalism is illustrated by its application to two basic problems : the decay of the quasi - stationary state and the calculation of the nonlinear resonance line shape . .
And you have already written the first three sentences of the full article: the rapid expansion of research frontiers into the nanometer and femtosecond regime demands a careful consideration of dissipation as a way to counterbalance the energy influx from the external fields in quantum mechanical systems .
the subject takes roots in the seminal work by feynman and vernon @xcite who treated a quantum object coupled to an infinite collection of oscillators as a model of a linear dissipative environment . by employing the path - integral techniques they were able to eliminate the environment variables and arrived at a dissipative modification of the green s function of the quantum object
this approach was further used by a number of authors , most notably by caldeira and leggett @xcite , who applied it to a specific problem of dissipative effects in tunneling on a macroscopic scale . a detailed account on the problem of dissipation in quantum - mechanical systems.
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can be found in a monograph by weiss @xcite while semiclassical approaches are also reviewed in @xcite .
generally , the main mode of attack uses the density - matrix formalism @xcite and the popular lindblad technique @xcite .
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10,057 |
Suppose that you have an abstract for a scientific paper: we construct exact functional renormalization group ( rg ) flow equations for non - relativistic fermions in arbitrary dimensions , taking into account not only mode elimination but also the rescaling of the momenta , frequencies and the fermionic fields .
the complete rg flow of all relevant , marginal and irrelevant couplings can be described by a system of coupled flow equations for the irreducible @xmath0-point vertices . introducing suitable dimensionless variables , we obtain flow equations for generalized scaling functions which are _ continuous _ functions of the flow parameter , even if we consider quantities which are dominated by momenta close to the fermi surface , such as the density - density correlation function at long wavelengths .
we also show how the problem of constructing the renormalized fermi surface can be reduced to the problem of finding the rg fixed point of the irreducible two - point vertex at vanishing momentum and frequency .
we argue that only if the degrees of freedom are properly rescaled it is possible to reach scale - invariant non - fermi liquid fixed points within a truncation of the exact rg flow equations .
= 10000 .
And you have already written the first three sentences of the full article: recently several authors @xcite have used exact functional renormalization group ( rg ) methods to gain a deeper understanding of strongly correlated non - relativistic fermions in reduced dimensions .
the exact functional rg yields an infinite hierarchy of coupled differential equations describing the change of the correlation functions due to the elimination and the rescaling of the degrees of freedom . for classical statistical mechanics problems
the exact functional rg has been developed long time ago in a pioneering work by wegner and houghton @xcite , who performed the usual three rg - steps @xcite to derive their exact flow equation : 1 ..
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integrate out fields with momenta @xmath1 in a shell @xmath2 , where @xmath3 is infinitesimal and @xmath4 is some ultraviolet cutoff .
2 . rescale the remaining momenta by a factor @xmath5 and express all quantities in terms of the rescaled momenta .
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10,058 |
Suppose that you have an abstract for a scientific paper: thomson optical depth @xmath0 measurements from planck provide new insights into the reionization of the universe . in pursuit of model - independent constraints on the properties of the ionizing sources , we determine the empirical evolution of the cosmic ionizing emissivity .
we use a simple two - parameter model to map out the evolution in the emissivity at @xmath16 from the new planck optical depth @xmath0 measurements , from the constraints provided by quasar absorption spectra and from the prevalence of lyman @xmath2 emission in @xmath3 - 8 galaxies .
we find the redshift evolution in the emissivity @xmath4 required by the observations to be @xmath5 ( @xmath6 for a flat prior ) , largely independent of the assumed clumping factor @xmath7 and entirely independent of the nature of the ionizing sources .
the trend in @xmath4 is well - matched by the evolution of the galaxy @xmath8-luminosity density ( d@xmath9 ) to a magnitude limit @xmath1013 mag , suggesting that galaxies are the sources that drive the reionization of the universe .
the role of galaxies is further strengthened by the conversion from the uv luminosity density @xmath11 to @xmath4 being possible for physically - plausible values of the escape fraction @xmath12 , the lyman - continuum photon production efficiency @xmath13 , and faint - end cut - off @xmath14 to the luminosity function .
quasars / agn appear to match neither the redshift evolution nor normalization of the ionizing emissivity .
based on the inferred evolution in the ionizing emissivity , we estimate that the @xmath15 uv - luminosity density is @xmath16 lower than at @xmath17 , consistent with the observations .
the present approach of contrasting the inferred evolution of the ionizing emissivity with that of the galaxy uv luminosity density adds to the growing observational evidence that faint , star - forming galaxies drive the reionization of the universe . .
And you have already written the first three sentences of the full article: one of the most important phase transitions in the history of the universe is the reionization of the neutral hydrogen gas .
following recombination early in the universe shortly after the big bang , the universe likely remained in a largely neutral state until @xmath18 - 25 .
the collapse of the first dark matter halos and gas cooling brought about the formation of the first stars and galaxies . these early stars and galaxies have long been thought to provide the ionizing photons necessary to reionize the universe ( loeb & barkana 2001 ; loeb 2006 ) . despite this general picture of reionization and the likely role that early galaxies played in the process , establishing that this is the case has been particularly challenging , both due to the difficulties in probing the ionization state of the universe at @xmath19 ( e.g. , ouchi et al ..
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2010 ; stark et al .
2010 ) and providing constraints on the ionizing photons that early galaxies themselves are thought to produce ( e.g. , siana et al . 2010 , 2015 ;
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10,059 |
Suppose that you have an abstract for a scientific paper: in this paper and a companion paper , we report on a wide - field imaging survey of the globular cluster ( gc ) populations around m87 carried out with suprime - cam on the 8.2 m subaru telescope . here
we describe the observations , data reduction , and data analysis and present luminosity functions of gc populations around m87 and ngc 4552 , another luminous virgo elliptical in our survey field .
the imaging data were taken in the @xmath0 , @xmath1 , and @xmath2 bands with a sky coverage of @xmath3 extending from the m87 centre out to @xmath4 0.5 mpc .
gc candidates were selected by applying a colour criterion on the @xmath5 and @xmath6 diagram to unresolved objects , which greatly reduces contamination .
the data from control fields taken with subaru / suprime - cam were also analyzed for subtraction of contamination in the gc sample .
these control field data are compatible with those in the m87 field in terms of the filter set ( @xmath7 ) , limiting magnitudes , and image quality , which minimizes the possibility of introducing any systematic errors into the subtractive correction .
we investigate gc luminosity functions ( gclfs ) at distances @xmath8 ( @xmath9 45 kpc ) from the host galaxy centre in detail . by fitting gaussians to the gclfs , the @xmath1-band turnover magnitude ( @xmath10 ) is estimated to be @xmath11 mag and @xmath12 mag for the gc population in m87 and ngc 4552 , respectively .
the gclf is found to be a function of gc colour ; @xmath13 of the red gc subpopulation ( @xmath14 ) is fainter than that of the blue gc subpopulation ( @xmath15 ) in both m87 and ngc 4552 , as expected if the colour differences are primarily due to a metallicity effect and the mass functions of the two subpopulations are similar .
the radial dependence of the gclf is also investigated for the gc population in m87 .
the gclf of each subpopulation at @xmath16 is compared with that at @xmath17 but no significant trend with distance is found in the shape of the gclf .
we also estimate gc....
And you have already written the first three sentences of the full article: globular clusters ( gcs ) are homogeneous stellar systems containing stars with a single age and metallicity , which are in principle simpler to interpret than photometric and spectroscopic observations of the integrated stellar light of a galaxy .
gcs are therefore considered to be powerful probes with which to understand the star formation and chemical enrichment history of their host galaxy .
one of the basic findings from observations about gc populations in luminous galaxies is that while thousands of gcs are associated with luminous elliptical galaxies , a significantly smaller number of gcs exist around spiral galaxies with similar luminosities ( e.g. , harris 1991 ; barmby 2003 ) ..
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this indicates that the specific frequency of gcs ( @xmath18 ) , which is considered to be related to the relative efficiency of gc formation and/or survival compared to galactic halo / bulge stars , depends on galaxy morphology .
in fact , @xmath18 has also been suggested to be correlated with local galaxy density , with galaxies in denser environments having larger @xmath18 values ( west 1993 ) .
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10,060 |
Suppose that you have an abstract for a scientific paper: projective clustering is a problem with both theoretical and practical importance and has received a great deal of attentions in recent years . given a set of points @xmath0 in @xmath1 space , projective clustering is to find a set @xmath2 of @xmath3 lower dimensional @xmath4-flats so that the average distance ( or squared distance ) from points in @xmath0 to their closest flats is minimized .
existing approaches for this problem are mainly based on adaptive / volume sampling or core - sets techniques which suffer from several limitations . in this paper , we present the first uniform random sampling based approach for this challenging problem and achieve linear time solutions for three cases , general projective clustering , regular projective clustering , and @xmath5 sense projective clustering . for the general projective clustering problem ,
we show that for any given small numbers @xmath6 , our approach first removes @xmath7 points as outliers and then determines @xmath3 @xmath4-flats to cluster the remaining points into @xmath3 clusters with an objective value no more than @xmath8 times of the optimal for all points . for regular projective clustering ,
we demonstrate that when the input points satisfy some reasonable assumption on its input , our approach for the general case can be extended to yield a ptas for all points . for @xmath5 sense projective clustering ,
we show that our techniques for both the general and regular cases can be naturally extended to the @xmath5 sense projective clustering problem for any @xmath9 .
our results are based on several novel techniques , such as slab partition , @xmath10-rotation , symmetric sampling , and recursive projection , and can be easily implemented for applications . .
And you have already written the first three sentences of the full article: projective clustering for a set @xmath0 of @xmath11 points in @xmath1 space is to find a set @xmath2 of @xmath3 lower dimensional @xmath4-flats so that the average distance ( by certain distance measure ) from points in @xmath0 to their closest flats is minimized .
depending on the choices of @xmath4 and @xmath3 , the problem has quite a few different variants .
for instance , when @xmath12 , the problem is to find a @xmath4-flat to fit a set of points and is often called shape fitting problem . on the contrary , when @xmath13 , the problem is to find @xmath3 lines to cluster a point set , and thus is called @xmath3-line clustering . in this paper , we mainly consider the @xmath14 sense projective clustering , i.e. , minimizing the average squared distances to the resulting flats ..
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we also consider extensions to regular projective clustering and @xmath5 sense projective clustering for any integer @xmath9 , where the regular projective clustering is for points whose projection on its optimal fitting flat have bounded coefficient of variation along any direction .
* previous results : * projective clustering is related to many theoretical problems such as shape fitting , matrix approximation , etc .
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10,061 |
Suppose that you have an abstract for a scientific paper: we present the discovery of several new regions of interaction between the ejecta and equatorial circumstellar ring of sn1987a , an interaction leading to a much expanded development of the supernova remnant .
we also trace the development of the first such `` hot spot , '' discovered in 1997 , back to 1995 .
later hot spots seem to have emerged by early 1999 .
we discuss mechanisms for the long delay between the first and later spots . .
And you have already written the first three sentences of the full article: the development of sn 1987a provides an unprecedented opportunity to observe , at high spatial , spectral , and temporal resolution , the birth of a supernova remnant ( snr ) .
observations of snr 1987a might reveal the angular and velocity distribution of the ejecta by highlighting where it impacts a presumably well - known nebular structure . while snr 1987a has been observed for some years in x - rays and radio , only optical / near - ir data have sufficient sensitivity and angular resolution to detail the structures presented here .
the early discovery of these interaction regions is crucial ..
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we demonstrate how they are best revealed with difference imaging , in h@xmath0 and [ ] , and in 1.083@xmath1 m , for which the newly - formed spots have greatest contrast above the circumstellar equatorial ring ( er ) .
we detect several new interaction sites , and trace known features back to epochs well before their actual discoveries .
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10,062 |
Suppose that you have an abstract for a scientific paper: in 1987 , ornstein and weiss discovered that the bernoulli @xmath0-shift over the rank two free group factors onto the seemingly larger bernoulli @xmath1-shift . with the recent creation of an entropy theory for actions of sofic groups ( in particular free groups ) ,
their example shows the surprising fact that entropy can increase under factor maps . in order to better understand this phenomenon
, we study a natural generalization of the ornstein weiss map for countable groups .
we relate the increase in entropy to the cost and to the first @xmath2-betti number of the group .
more generally , we study coboundary maps arising from simplicial actions and , under certain assumptions , relate @xmath2-betti numbers to the failure of the juzvinski addition formula .
this work is built upon a study of entropy theory for algebraic actions .
we prove that for actions on profinite groups via continuous group automorphisms , topological sofic entropy is equal to measure sofic entropy with respect to haar measure whenever the homoclinic subgroup is dense . for algebraic actions of
residually finite groups we find sufficient conditions for the sofic entropy to be equal to the supremum exponential growth rate of periodic points . .
And you have already written the first three sentences of the full article: entropy is a fundamental invariant of dynamical systems .
it was first defined for probability measure preserving actions of @xmath3 by kolmogorov in 1958 @xcite and then extended to actions of countable amenable groups by kieffer in 1975 @xcite .
the notion was transferred to continuous actions of @xmath3 by adler - konheim - mcandrew in 1965 @xcite . despite evidence suggesting that entropy theory could not be extended beyond actions of amenable groups , groundbreaking work by bowen in 2008 @xcite , together with improvements by kerr and li @xcite , created a definition of entropy for probability measure preserving actions of sofic groups ..
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this definition was also generalized to the topological setting by kerr and li @xcite .
this new notion of entropy is an extension of its classical counterpart , as when the acting sofic group is amenable the two notions coincide @xcite , however it displays surprising behavior which violates some of the fundamental properties of classical entropy theory . in this paper
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10,063 |
Suppose that you have an abstract for a scientific paper: recent observational studies have revealed that the galactic bulge has cylindrical rotation and a steeper vertical metallicity gradient .
we adopt two representative models for the bulge formation and thereby investigate whether the two models can explain both the observed cylindrical rotation and vertical metallicity gradient in a self - consistent manner .
one is the `` pure disk scenario '' ( pds ) in which the bulge is formed from a pure thin stellar disk through spontaneous bar instability .
the other is the `` two - component disk scenario '' ( tcds ) in which the bulge is formed from a disk composed of thin and thick disks through bar instability .
our numerical simulations show that although pds can reproduce the cylindrical rotation , it shows a rather flatter vertical metallicity gradient that is inconsistent with observations .
the derived flatter metallicity gradient is due to the vertical mixing of stars with different initial metallicities by the stellar bar .
this result implies that the bulge can not be simply formed from a pure thin stellar disk . on the other hand
, the bulge formed from the two - component disk in tcds can explain both the observed cylindrical rotation and vertical metallicity gradient of the galactic bulge reasonably well .
in tcds , more metal - poor stars at higher @xmath0 ( vertical distance ) which originate from the already dynamically hotter thick disk can not be strongly influenced by vertical mixing of the bar so that they can stay in situ for longer timescales and thus keep the lower metallicity at higher @xmath0 .
consequently , the vertical metallicity gradient of the bulge composed of initially thin and thick disk stars can not be so flattened , even if the gradient of the thin disk can be flattened significantly by the bar in tcds .
we therefore suggest that a significant fraction of the present galactic bulge is composed of stars initially in the inner part of the thick disk and thus that these bulge stars and the thick disk have a common....
And you have already written the first three sentences of the full article: the galaxy is observed to have a `` boxy '' bulge in near - infrared images ( dwek et al .
1995 ) and the nature and the origin of the inner triaxial shape of the galaxy ( i.e. , bar / bulge ) has been extensively discussed by several authors ( e.g. , babusiaux & gilmore 2005 ; rattenbury et al .
recent spectroscopic observations on stellar abundances and kinematics of the galactic bulge have provided new clues to the origin of the triaxial bulge ( e.g. , melndez et al ..
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2008 ; zoccali et al . 2008 ; babusiaux et al . 2010 ) .
melndez et al .
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10,064 |
Suppose that you have an abstract for a scientific paper: interactions among living organisms , from bacteria colonies to human societies , are inherently more complex than interactions among particles and nonliving matter .
group interactions are a particularly important and widespread class , representative of which is the public goods game .
in addition , methods of statistical physics have proven valuable for studying pattern formation , equilibrium selection , and self - organisation in evolutionary games . here
we review recent advances in the study of evolutionary dynamics of group interactions on structured populations , including lattices , complex networks and coevolutionary models .
we also compare these results with those obtained on well - mixed populations .
the review particularly highlights that the study of the dynamics of group interactions , like several other important equilibrium and non - equilibrium dynamical processes in biological , economical and social sciences , benefits from the synergy between statistical physics , network science and evolutionary game theory . .
And you have already written the first three sentences of the full article: we present a review of recent advances on the evolutionary dynamics of spatial games that are governed by group interactions .
the focus is on the public goods game , or more generally @xmath0-player games , which are representative for this type of interaction .
although relevant aspects of @xmath1-player games are surveyed as well , we refer to @xcite for a more thorough exposition ..
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another important aspect of this review is its focus on structured populations . in the continuation of this introductory section we will also summarise basic results concerning the public goods game on well - mixed populations , but we refer the reader to @xcite for details .
the methodological perspective that permeates throughout the review is that of statistical physics .
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10,065 |
Suppose that you have an abstract for a scientific paper: researchers have devoted themselves to exploring static features of social networks and further discovered many representative characteristics , such as power law in the degree distribution and assortative value used to differentiate social networks from nonsocial ones .
however , people are not satisfied with these achievements and more and more attention has been paid on how to uncover those dynamic characteristics of social networks , especially how to track community evolution effectively . with these interests ,
in the paper we firstly display some basic but dynamic features of social networks . then on its basis
, we propose a novel core - based algorithm of tracking community evolution , commtracker , which depends on core nodes to establish the evolving relationships among communities at different snapshots . with the algorithm
, we discover two unique phenomena in social networks and further propose two representative coefficients : growth and metabolism by which we are also able to distinguish social networks from nonsocial ones from the dynamic aspect . at last ,
we have developed a social network model which has the capabilities of exhibiting two necessary features above . .
And you have already written the first three sentences of the full article: social network analysis has been a hot topic in the field of data mining . in the co - authorship network ,
a node is an author and a edge indicates a publishing collaboration between them .
researchers are interested in these special networks from which they discover power law in the degree distribution , that is , only a small proportion of nodes have high degrees while the rest has low degree ..
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social networks also present positive assortative values while in nonsocial networks , such as internet , biology network , the values are always negative , indicating that in social networks , higher degree nodes trend to connect with higher degree nodes while in nonsocial ones , it is largely possible that higher degree ones are linked with lower degree ones .
moreover , researchers reveal community structures where the vertices within communities have higher density of edges while vertices between communities have lower density of edges . in the co - authorship network ,
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10,066 |
Suppose that you have an abstract for a scientific paper: a multispeckle technique for efficiently measuring correctly ensemble - averaged intensity autocorrelation functions of scattered light from non - ergodic and/or non - stationary systems is described .
the method employs a ccd camera as a multispeckle light detector and a computer - based correlator , and permits the simultaneous calculation of up to 500 correlation functions , where each correlation function is started at a different time .
the correlation functions are calculated in real time and are referenced to a unique starting time .
the multispeckle nature of the ccd camera detector means that a true ensemble average is calculated ; no time averaging is necessary .
the technique thus provides a snapshot " of the dynamics , making it particularly useful for non - stationary systems where the dynamics are changing with time .
delay times spanning the range from 1 ms to 1000 s are readily achieved with this method .
the technique is demonstrated in the multiple scattering limit where diffusing - wave spectroscopy theory applies .
the technique can also be combined with a recently - developed two - cell technique that can measure faster decay times .
the combined technique can measure delay times from 10 ns to 1000 s. the method is peculiarly well suited for studying aging processes in soft glassy materials , which exhibit both short and long relaxation times , non - ergodic dynamics , and slowly - evolving transient behavior . .
And you have already written the first three sentences of the full article: dynamic light scattering has proven to be a powerful tool for investigating the dynamics of colloidal suspensions , emulsions , foams , and other complex fluids . over the past decade ,
dynamic light scattering ( dls ) has been increasingly applied to glassy systems with slow , and often non - ergodic , dynamics .
slow dynamics pose experimental difficulties for dls , particularly with respect to the stability of the lasers , and sometimes for the light detection system ..
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nonergodic samples pose even more serious experimental difficulties , which are exacerbated by the presence of slow dynamics .
one way of addressing the problem of long data acquisition times is to use an array detector .
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10,067 |
Suppose that you have an abstract for a scientific paper: we study spacetime singularities in a general five - dimensional braneworld with curved branes satisfying four - dimensional maximal symmetry . the bulk is supported by an analog of perfect fluid with the time replaced by the extra coordinate .
we show that contrary to the existence of finite distance singularities from the brane location in any solution with flat ( minkowski ) branes , in the case of curved branes there are singularity - free solutions for a range of equations of state compatible with the null energy condition . .
And you have already written the first three sentences of the full article: in previous work we studied the singularity structure of a braneworld model consisting of a flat @xmath0-brane embedded in a five - dimensional bulk space filled with an analogue of a perfect fluid ( the fifth coordinate @xmath1 playing the role of time ) .
the perfect fluid satisfied a linear equation of state with a constant parameter @xmath2 , @xmath3 , where @xmath4 is the ` pressure ' and @xmath5 is the ` density ' . in @xcite
we showed that for a flat brane there exist singularities that appear within finite distance @xmath6 from the position of the brane supposedly located at the origin , for all values of @xmath2 . a way to avoid such singularities.
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is to exploit the natural @xmath7 symmetry introduced by the existence of the brane by cutting the bulk space and considering a slice of it which is free from finite - distance singularities .
although this matching mechanism is possible for all values of @xmath2 , the requirement for localised gravity on the brane restricts @xmath2 in the interval @xmath8 . on the other hand , further requirements for physical conditions , such as energy conditions ,
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10,068 |
Suppose that you have an abstract for a scientific paper: we analyze the decay processes @xmath0 , @xmath1 , @xmath2 , and @xmath3 in a model - independent way . using the quark diagram approach ,
we determine the magnitudes of the relevant amplitudes and the relative strong phase shifts . in order to find the most likely values of the magnitudes and the relative strong phases of the amplitudes in a statistically reliable way
, we use the @xmath4 minimization technique .
we find that the strong phase difference between the color - allowed and the color - suppressed tree amplitude can be large and is non - zero at 1@xmath5 level with the present data .
the color - suppressed tree contributions are found to be sizably enhanced .
we also examine the validity of factorization and estimate the breaking effects of flavor su(3 ) symmetry in @xmath0 , @xmath2 and in @xmath6 , @xmath3 . .
And you have already written the first three sentences of the full article: a tremendous amount of experimental data on @xmath7 meson decays are being collected from @xmath7 factory experiments , such as belle and babar .
experimentally plenty of two - body hadronic @xmath7 decays have been observed and a lot of theoretical works on these decay processes have been done . in particular , the first observation of the color - suppressed decay processes @xmath8 and @xmath9 by the belle collaboration @xcite has drawn special attentions , since it allows one to do a complete isospin analysis of the @xmath10 modes together with the previously observed charged modes of the @xmath10 type .
two - body hadronic @xmath7 meson decays to @xmath11 and @xmath12 final states have been of great interest . in these decay modes.
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, there is no contribution from penguin diagrams so that theoretical uncertainties involved in the relevant qcd dynamics become much less .
thus , these modes serve as a good testing ground for various theoretical issues in hadronic @xmath7 decays , such as factorization hypothesis and final - state interactions .
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10,069 |
Suppose that you have an abstract for a scientific paper: regularization of ill - posed linear inverse problems via @xmath0 penalization has been proposed for cases where the solution is known to be ( almost ) sparse .
one way to obtain the minimizer of such an @xmath0 penalized functional is via an iterative soft - thresholding algorithm .
we propose an alternative implementation to @xmath0-constraints , using a gradient method , with projection on @xmath0-balls .
the corresponding algorithm uses again iterative soft - thresholding , now with a variable thresholding parameter .
we also propose accelerated versions of this iterative method , using ingredients of the ( linear ) steepest descent method .
we prove convergence in norm for one of these projected gradient methods , without and with acceleration . .
And you have already written the first three sentences of the full article: our main concern in this paper is the construction of iterative algorithms to solve inverse problems with an @xmath0-penalization or an @xmath0-constraint , and that converge faster than the iterative algorithm proposed in @xcite ( see also formulas and below ) .
before we get into technical details , we introduce here the background , framework , and notations for our work . in many practical problems
, one can not observe directly the quantities of most interest ; instead their values have to be inferred from their effect on observable quantities ..
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when this relationship between observable @xmath1 and interesting quantity @xmath2 is ( approximately ) linear , as it is in surprisingly many cases , the situation can be modeled mathematically by the equation @xmath3 where @xmath4 is a linear operator mapping a vector space @xmath5 ( which we assume to contain all possible `` objects '' @xmath2 ) to a vector space @xmath6 ( which contains all possible data @xmath1 ) .
the vector spaces @xmath5 and @xmath6 can be finite or infinite dimensional ; in the latter case , we assume that @xmath7 and @xmath6 are ( separable ) hilbert spaces , and that @xmath8 is a bounded linear operator .
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10,070 |
Suppose that you have an abstract for a scientific paper: we present a study of mcneil s nebula , a newly appeared reflection nebula in the l1630 cloud , together with photometry and spectroscopy of its source .
new ir photometry compared to earlier 2mass data shows that the star has brightened by about 3 magnitudes in the near - infrared , changing its location in a j - h / h - k@xmath0 diagram precisely along a reddening vector .
a gemini niri k - band spectrum shows strong co - bandhead emission and br@xmath1 is in emission , indicative of strong accretion .
a gemini gmos optical spectrum shows only a red , heavily veiled continuum , with h@xmath2 strongly in emission and displaying a pronounced p cygni profile , with an absorption trough reaching velocities up to 600 km s@xmath3 .
this implies significant mass loss in a powerful wind .
however , no evidence is found for any shocks , as commonly seen in collimated outflows from young stars . apparently the eruption has dispersed a layer of extinction and this ,
together with the intrinsic brightening of the iras source , has allowed an earlier outflow cavity to be flooded with light , thus creating mcneil s nebula . .
And you have already written the first three sentences of the full article: wide - field photographic and ccd images have documented the presence of numerous small compact reflection nebulae in star - forming dark clouds .
such nebulae may possibly represent a transitional stage in which a young star goes from being an embedded infrared source to a visible t tauri star or herbig ae / be star .
this process is widely believed to involve powerful bipolar outflow activity , as reflected in the morphology of the nebulae , which are often cometary , with the partially embedded star illuminating an outflow cavity . when observed over longer time - scales , such small reflection nebulae.
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are often found to vary in brightness and occasionally in illumination pattern .
perhaps the earliest known example is ngc 2261 , which reflects light from the young star r mon and was found to vary by hubble ( 1916 ) .
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10,071 |
Suppose that you have an abstract for a scientific paper: we present the techniques used to determine redshifts and to characterize the spectra of objects in the caltech faint galaxy redshift survey in terms of spectral classes and redshift quality classes .
these are then applied to spectra from an investigation of a complete sample of objects with @xmath0 mag in a 2 by 7.3 arcmin@xmath1 field at j005325 + 1234 .
redshifts were successfully obtained for 163 of the 195 objects in the sample ; these redshifts lie in the range [ 0.173 , 1.44 ] and have a median of 0.58 ( excluding 24 galactic stars ) .
the sample includes two broad lined agns and one qso . .
And you have already written the first three sentences of the full article: the caltech faint galaxy redshift survey , ( henceforth cfgrs ) , is designed to measure the properties of field galaxies in the redshift interval @xmath2 .
it uses complete samples to a fixed limiting magnitude in a particular bandpass within a small solid angle on the sky .
spectra are obtained for every object in the sample with the low resolution imaging spectrograph ( henceforth lris ) ( oke _ et al . _.
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1995 ) on the 10 m keck telescope .
the defining features of this program that distinguish it from existing and ongoing or planned surveys , such as the cfa1 survey ( @xcite ) , the las campanas redshift survey ( @xcite ) , the canada - france redshift survey ( henceforth cfrs ; lilly _ et al . _ 1995a ,
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10,072 |
Suppose that you have an abstract for a scientific paper: the phase behavior of a large but finite ising ferromagnet in the presence of competing surface magnetic fields @xmath0 is studied by monte carlo simulations and by phenomenological theory . specifically , the geometry of a double pyramid of height @xmath1 is considered , such that the surface field is positive on the four upper triangular surfaces of the bi - pyramid and negative on the lower ones .
it is shown that the total spontaneous magnetization vanishes ( for @xmath2 ) at the temperature @xmath3 , related to the `` filling transition '' of a semi - infinite pyramid , which can be well below the critical temperature of the bulk .
the discontinuous vanishing of the magnetization is accompanied by a susceptibility that diverges with a curie - weiss power law , when the transition is approached from either side . a landau theory with size - dependent critical amplitudes
is proposed to explain these observations , and confirmed by finite size scaling analysis of the simulation results .
the extension of these results to other nanosystems ( gas - liquid systems , binary mixtures , etc . ) is briefly discussed . .
And you have already written the first three sentences of the full article: the current paradigm of attempting to develop various kinds of nanoscopic devices requires careful consideration of the phase behavior of nanosystems , since in nanoscopic geometries effects due to external walls or other boundaries of the system can modify its `` bulk '' behavior substantially . qualitatively new kinds of phenomena may occur , that have not yet been studied for macroscopic bulk systems .
we demonstrate a new kind of phase transition in the present paper , which belongs to the class of interface localization - delocalization phenomena , using the simple ising ferromagnet with nearest - neighbor exchange on a cubic lattice as a generic example . choosing a compact octahedral shape of the system in the form of a bi - pyramid of height 2l
, we assume that on the upper surfaces of the pyramid ( @xmath4 ) a positive surface magnetic field @xmath5 acts , while on the lower surfaces ( with @xmath6 ) the field is negative but of the same absolute strength , so that no sign of the magnetization is overall preferred . more generally , one might consider the case with positive and negative fields of different strength ; their difference , however , could be effectively compensated by a suitably chosen bulk field such that at low temperatures again a degeneracy with respect to the sign of the spontaneous magnetization is possible , similar to the case of `` capillary condensation''-type phenomena in semi - infinite thin films @xcite ..
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in this case one can also expect an interesting interplay between the wetting behavior of the semi - infinite system and the phase behavior in confinement , a complication that is not considered in the present manuscript .
such a system is then described ( for @xmath7 ) by an order parameter ( the spontaneous magnetization of the ising ferromagnet ) , which does _ not _ remain non - zero up to the critical temperature @xmath8 of the bulk three - dimensional model , but rather only up to a temperature @xmath9 , identical with the ( critical ) temperature of the filling transition @xcite in a single semi - infinite pyramid .
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10,073 |
Suppose that you have an abstract for a scientific paper: trigonometric time integrators are introduced as a class of explicit numerical methods for quasilinear wave equations . second - order convergence for the semi - discretization in time with these integrators
is shown for a sufficiently regular exact solution .
the time integrators are also combined with a fourier spectral method into a fully discrete scheme , for which error bounds are provided without requiring any cfl - type coupling of the discretization parameters .
the proofs of the error bounds are based on energy techniques and on the semiclassical grding inequality . + * mathematics subject classification ( 2010 ) : * 65m15 , 65p10 , 65l70 , 65m20 .
+ * keywords : * quasilinear wave equation , trigonometric integrators , exponential integrators , error bounds , loss of derivatives , energy estimates . .
And you have already written the first three sentences of the full article: the topic of the present paper is the numerical analysis of _ quasilinear wave equations_. such wave equations show up in a variety of applications , ranging from elastodynamics to general relativity . while the ( local - in - time ) analysis of them is well - developed since the seventies , the papers @xcite by kato and @xcite by hughes , kato & marsden being major contributions to the local well - posedness theory , and has meanwhile found its way into classical monographs on partial differential equation , see , for instance , the monograph @xcite by taylor , as well as the books by sogge @xcite and hrmander @xcite , the numerical analysis of quasilinear wave equations is much less developed .
the main challenge is , of course , the numerical treatment of the quasilinear term in the equation . in the present paper ,
we focus on quasilinear wave equations of the form @xmath0 where @xmath1 and @xmath2 are smooth and real - valued functions such that @xmath3 ..
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we consider real - valued solutions to with @xmath4-periodic boundary conditions in one space dimension , @xmath5 , for initial values @xmath6 given at time @xmath7 .
the real - valued parameter @xmath8 will be used to emphasize the strength of the nonlinearities , and we will be interested both in the regime where @xmath8 is small so that the nonlinearities are small and the regime where @xmath8 is of order one .
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10,074 |
Suppose that you have an abstract for a scientific paper: i investigate the quantum phase transition of the transverse - field quantum ising model in which nearest neighbors are defined according to the connectivity of scale - free networks . using a continuous - time quantum monte carlo simulation method and the finite - size scaling analysis
, i identify the quantum critical point and study its scaling characteristics . for the degree exponent @xmath0
, i obtain results that are consistent with the mean - field theory . for @xmath1 and 4 , however , the results suggest that the quantum critical point belongs to a non - mean - field universality class .
further simulations indicate that the quantum critical point remains mean - field - like if @xmath2 , but it continuously deviates from the mean - field theory as @xmath3 becomes smaller . .
And you have already written the first three sentences of the full article: recently , complex networks have drawn much attention among the physics community because they can describe a huge variety of both natural and man - made systems , such as the world wide web,@xcite the internet,@xcite human social networks,@xcite power grids,@xcite ecological networks,@xcite metabolic networks,@xcite neural networks,@xcite and protein interactions@xcite . in a physical model based on such a network ,
individual elements interact with each other if they are directly connected by a link .
the equilibrium properties of such a system are strongly affected by its topological structure ..
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as opposed to a regular lattice with nearest neighbor interactions , a complex network has random long - range connections that enhance long - range correlation , clustering , and small - worldness . while the `` volume '' of the system is proportional to the number of nodes @xmath4 , the largest distance grows no faster than @xmath5 , hence the effective dimension of a complex network becomes infinitely large.@xcite in many cases , these effects are manifested in critical phenomena , where the increase of long - range connections drive the critical point toward the mean - field universality class.@xcite the degree @xmath6 of a node is defined as the number of links it is connected to .
the way the degrees are distributed is an important property that characterizes a complex network .
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10,075 |
Suppose that you have an abstract for a scientific paper: using @xmath0-body simulations we study the phenomenon of radial orbit instability occurring in dark matter haloes of the size of a dwarf galaxy .
we carried out simulations of seven spherical models , with the same standard nfw density profile but different anisotropy profiles of particle orbits .
four of them underwent instability : two with a constant positive anisotropy , one with an anisotropic core and an isotropic envelope and one with a very small isotropic core and an anisotropic envelope .
haloes affected by the instability become approximately axisymmetric and prolate , with the profile of the shortest - to - longest axis ratio increasing with radius .
the lower limit for the central value of this axis ratio is 0.3 for an nfw halo .
the density profiles of the haloes did not change significantly , whereas the velocity distributions became axisymmetric .
the angular momentum modulus rose due to large - amplitude oscillations of its components perpendicular to the symmetry axis of the halo .
we also studied orbits of individual particles assigning them to classical orbit families in triaxial potentials .
we find that the membership of a given particle in a family depends on its initial angular momentum modulus and its components along the principal axes of matter distribution .
galaxies : dwarf galaxies : fundamental parameters galaxies : kinematics and dynamics cosmology : dark matter .
And you have already written the first three sentences of the full article: simulations of structure formation in the universe with dark matter only lead us to believe that virialized structures , such as dark matter haloes , possess universal properties that depend only weakly on mass .
one such property , most often used , is the spherically averaged density profile that can be approximated by the well - known nfw @xcite formula .
however , dark matter haloes are definitely not spherical and their shapes can be approximated by triaxial ellipsoids , with principal axes labelled @xmath1 , @xmath2 , @xmath3 , so that @xmath4 ..
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@xcite reported that on average @xmath5 and @xmath6 .
in addition , the longest axis is usually aligned with the closest filament in the neighbouring structure .
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10,076 |
Suppose that you have an abstract for a scientific paper: we study in detail a peculiar configuration of the talbot - lau matter wave interferometer , characterised by unequal distances between the two diffraction gratings and the observation plane .
we refer to this apparatus as the `` asymmetric talbot - lau setup '' .
particular attention is given to its capabilities as an inertial sensor for particle and atomic beams , also in comparison with the classical moir deflectometer .
the present analysis is motivated by possible experimental applications in the context of antimatter wave interferometry , including the measurement of the gravitational acceleration of antimatter particles . to support our findings ,
we have performed numerical simulations of realistic particle beams with varying speed distributions . .
And you have already written the first three sentences of the full article: inertial sensors for particle beams based on material transmission gratings exist and have been studied extensively ( see for example @xcite ) .
commonly , these devices are moir deflectometers @xcite : two - grating setups operating in the classical regime , with the particles following ballistic trajectories and producing geometrical shadow fringe patterns .
the presence of a constant and uniform force in the transverse direction ( corresponding to an acceleration @xmath0 ) induces a displacement @xmath1 in the fringe pattern , where @xmath2 is the time of flight between the two gratings ..
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it is known that the talbot - lau matter - wave interferometer @xcite also possesses the same inertial sensitivity @xcite . unlike the moir deflectometer ,
this device operates in the quantum diffraction regime ; therefore the properties of the interference pattern depend on the de broglie wavelength of the interfering particles @xcite .
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10,077 |
Suppose that you have an abstract for a scientific paper: the initial phoenix deep survey ( pds ) observations with the australia telescope compact array have been supplemented by additional 1.4ghz observations over the past few years . here
we present details of the construction of a new mosaic image covering an area of 4.56 square degrees , an investigation of the reliability of the source measurements , and the 1.4ghz source counts for the compiled radio catalogue .
the mosaic achieves a @xmath0 rms noise of @xmath1jy at its most sensitive , and a homogeneous radio - selected catalogue of over 2000 sources reaching flux densities as faint as @xmath2jy has been compiled .
the source parameter measurements are found to be consistent with the expected uncertainties from the image noise levels and the gaussian source fitting procedure .
a radio - selected sample avoids the complications of obscuration associated with optically - selected samples , and by utilising complementary pds observations including multicolour optical , near - infrared and spectroscopic data , this radio catalogue will be used in a detailed investigation of the evolution in star - formation spanning the redshift range @xmath3 .
the homogeneity of the catalogue ensures a consistent picture of galaxy evolution can be developed over the full cosmologically significant redshift range of interest .
the 1.4ghz mosaic image and the source catalogue are available on the web at ` http://www.atnf.csiro.au/~ahopkins/phoenix/ ` or from the authors by request . .
And you have already written the first three sentences of the full article: exploration of star - formation processes in galaxies through observations at radio wavelengths has developed rapidly in the past few years @xcite . by avoiding the problems associated with dust obscuration , dominant at optical wavelengths , radio data provide a valuable tool in understanding the full picture of star - formation in galaxies .
the evolution of these galaxies , and the role of interactions and mergers in the population , are still only partially understood .
the phoenix deep survey ( pds ) aims to catalogue a large sample of _ radio - selected _ star - forming galaxies spanning the redshift range @xmath4 ..
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the pds includes a 1.4ghz survey made using the australia telescope compact array ( atca ) , and covers a field a little more than @xmath5 diameter , selected to lie in a region of low optical obscuration and devoid of bright radio sources @xcite . to clarify our nomenclature , we use the acronym pds to designate the survey as a whole , which includes multicolour optical photometry and spectroscopy as well as the radio imaging . the full 1.4ghz atca mosaic itself , over which all the complementary multiwavelength observations have been conducted ,
is referred to as the phoenix deep field ( pdf ) .
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10,078 |
Suppose that you have an abstract for a scientific paper: we propose two distinct atom interferometer gravitational wave detectors , one terrestrial and another satellite - based , utilizing the core technology of the stanford @xmath0 atom interferometer presently under construction .
each configuration compares two widely separated atom interferometers run using common lasers .
the signal scales with the distance between the interferometers , which can be large since only the light travels over this distance , not the atoms .
the terrestrial experiment with two @xmath1 atom interferometers separated by a @xmath2 baseline can operate with strain sensitivity @xmath3 in the 1 hz - 10 hz band , inaccessible to ligo , and can detect gravitational waves from solar mass binaries out to megaparsec distances . the satellite experiment with two atom interferometers separated by a @xmath4 baseline can probe the same frequency spectrum as lisa with comparable strain sensitivity @xmath5 .
the use of ballistic atoms ( instead of mirrors ) as inertial test masses improves systematics coming from vibrations , acceleration noise , and significantly reduces spacecraft control requirements .
we analyze the backgrounds in this configuration and discuss methods for controlling them to the required levels . .
And you have already written the first three sentences of the full article: gravitational waves offer a rich , unexplored source of information about the universe @xcite .
many phenomena can only be explored with gravitational , not electromagnetic , radiation .
these include accepted sources such as white dwarf , neutron star , or black hole binaries whose observation could provide useful data on astrophysics and general relativity ..
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it has even been proposed that these compact binaries could be used as standard sirens to determine astronomical distances and possibly the expansion rate of the universe more precisely @xcite .
gravitational waves could also be one of the only ways to learn about the early universe before the surface of last scattering .
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10,079 |
Suppose that you have an abstract for a scientific paper: we consider an approximate computation of several minimal eigenpairs of large hermitian matrices which come from high dimensional problems .
we use the tensor train format ( tt ) for vectors and matrices to overcome the curse of dimensionality and make storage and computational cost feasible . applying a block version of the tt format to several vectors simultaneously ,
we compute the low lying eigenstates of a system by minimization of a block rayleigh quotient performed in an alternating fashion for all dimensions . for several numerical examples ,
we compare the proposed method with the deflation approach when the low lying eigenstates are computed one - by - one , and also with the variational algorithms used in quantum physics .
_ keywords : _ high dimensional problems , dmrg , mps , tensor train format , low lying eigenstates . .
And you have already written the first three sentences of the full article: high - dimensional problems are notoriously difficult to solve by standard numerical techniques due to the _ curse of dimensionality _ the complexity grows exponentially with the number of degrees of freedom .
the problems of such kind arise in many different applications in physics , chemistry , biology and engineering , but their study in numerical linear algebra has begun quite recently .
there are not many techniques capable of solving high dimensional problems efficiently ..
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the most prominent among them are monte carlo and quasi monte carlo methods , best n - term approximations , and advanced discretization methods such as sparse grids and radial basis functions .
however , all of these methods have their own disadvantages . for example , it is difficult to achieve high accuracy using the monte carlo approach , and sparse grid techniques require sophisticated analytical and algebraic manipulations and still suffer ( in a milder way though ) from the curse of dimensionality , which make them inapplicable for @xmath0 one of the most fruitful ideas for solving high - dimensional problems is the idea of _ separation of variables_. for two variables it boils down to the celebrated schmidt decomposition , which is known on a discrete level as the singular value decomposition ( svd ) , a particular low
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10,080 |
Suppose that you have an abstract for a scientific paper: using a new grism at the keck interferometer , we obtained spectrally dispersed ( @xmath0 ) interferometric measurements of the mira star r vir .
these data show that the measured radius of the emission varies substantially from 2.0 - 2.4 @xmath1 m .
simple models can reproduce these wavelength - dependent variations using extended molecular layers , which absorb stellar radiation and re - emit it at longer wavelengths . because we observe spectral regions with and without substantial molecular opacity , we determine the stellar photospheric radius , uncontaminated by molecular emission . we infer that most of the molecular opacity arises at approximately twice the radius of the stellar photosphere . .
And you have already written the first three sentences of the full article: miras are asymptotic giant branch ( agb ) stars that show long - period ( hundreds of days ) photometric variability ( e.g. , * ? ? ?
these stars typically lose mass at a rapid rate ( @xmath2 m@xmath3 yr@xmath4 ) , and this material condenses into heavy elements , molecules , and dust ( e.g. , * ? ? ?
since agb stars account for most of the mass loss in the galaxy , their circumstellar environments are the likely factories in which many constituents of planets , and life , are produced ..
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separating molecular emission and absorption from stellar photospheric emission is important for constraining properties of molecular layers and the underlying stars .
the opacity and location of gaseous layers constrain the temperature structure in the circumstellar environments of mira stars ; this directly affects the dust condensation radius , and in turn the mass loss rate .
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10,081 |
Suppose that you have an abstract for a scientific paper: observations using the australia telescope compact array at a wavelength of 6 cm have uncovered the radio counterpart to the compact x - ray nebula surrounding the vela pulsar .
two lobes were found oriented about the spin axis of the pulsar , starting at the edge of x - ray emission , they extend to three times the size .
the northern lobe has a bright , defined edge and an integrated flux of 0.14 jy , while the southern lobe of 0.12 jy is more diffuse .
# 1_#1 _ # 1_#1 _ = # 1 1.25 in .125 in .25 in .
And you have already written the first three sentences of the full article: high resolution images from chandra x - ray observations of the vela pulsar have shown ( helfand , gotthelf , & halpern 2001 ; pavlov et al .
2001 ) an x - ray pulsar wind nebula ( pwn ) , which has been modelled in detail by helfand et al .
( 2001 ) with an alternative interpretation by radhakrishnan & deshpande ( 2001 ) ..
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x - ray and synchrotron emissions are closely linked as highly charged particle flows drive both , so radio emission is a natural comparison . this targeted observation was optimised at 6 cm to match the chandra image resolution and to improve on previous radio knowledge .
we imaged a compact radio counterpart about the pulsar ( figure 1 ) .
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10,082 |
Suppose that you have an abstract for a scientific paper: we have studied the magnetization of various , well characterized samples of highly oriented pyrolitic graphite ( hopg ) , kish graphite and natural graphite to investigate the recently reported ferromagnetic - like signal and its possible relation to ferromagnetic impurities .
the magnetization results obtained for hopg samples for applied fields parallel to the graphene layers - to minimize the diamagnetic background - show no correlation with the magnetic impurity concentration .
our overall results suggest an intrinsic origin for the ferromagnetism found in graphite .
we discuss possible origins of the ferromagnetic signal . .
And you have already written the first three sentences of the full article: we find in the literature reports on ferromagnetism in carbon - based compounds which apparently did not attract the necessary attention in the community .
for example there are reports on ferromagnetic - like signals in pyrolytic carbon @xcite and in hopg @xcite . in the first study pyrolytic carbon with
higher crystallinity than usual was prepared from adamantane by chemical vapor deposition @xcite ..
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the metal impurities were claimed to be @xmath0 ppm and the ferromagnetic - like loop was reported to persist up to 400 k. in other work @xcite the main study was the magnetization of pd nanoparticles encapsulated in a graphite host . in the inset of their fig .
2 the authors show a ferromagnetic - like hysteresis loop for graphite without pd nanoparticles at a temperature of 300 k. we note that the saturation magnetization @xmath1 emu / g is much larger than the one measured in this work and by kopelevich et al . @xcite . because the impurity concentration of that sample was not reported the origin of this signal remains , however , unclear .
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10,083 |
Suppose that you have an abstract for a scientific paper: pulsars of very different types isolated objects , and binaries with short- and long - period orbits , white - dwarf and neutron - star companions provide the means to test both the predictions of general relativity and the viability of alternate theories of gravity .
this article presents an overview of pulsars , then discusses the current status and future prospects of tests of equivalence principle violations and strong - field gravitational experiments . .
And you have already written the first three sentences of the full article: since their discovery in 1967 @xcite , radio pulsars have provided insights into physics on length scales covering the range from 1 m ( giant pulses from the crab pulsar @xcite ) to 10 km ( neutron star ) to kpc ( galactic ) to hundreds of mpc ( cosmological ) .
pulsars present an extreme stellar environment , with matter at nuclear densities , magnetic fields of 10@xmath0 g to nearly 10@xmath1 g , and spin periods ranging from 1.5ms to 8.5s .
the regular pulses received from a pulsar each correspond to a single rotation of the neutron star ..
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it is by measuring the deviations from perfect observed regularity that information can be derived about the neutron star itself , the interstellar medium between it and the earth , and effects due to gravitational interaction with binary companion stars .
in particular , pulsars have proved to be remarkably successful laboratories for tests of the predictions of general relativity ( gr ) .
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10,084 |
Suppose that you have an abstract for a scientific paper: we report on the discovery and analysis of a striking neutral sodium gas tail associated with comet c/1995 o1 hale - bopp .
sodium d
line emission has been observed at heliocentric distance @xmath0 au in some long period comets and the presence of neutral sodium in the tailward direction of a few bright comets has been noted , but the extent , and in particular the source , has never been clear .
here we describe the first observations and analysis of a neutral sodium gas tail in comet hale
bopp , entirely different from the previously known ion and dust tails .
we show that the observed characteristics of this third type of tail are consistent with it being produced by radiation pressure due to resonance fluorescence of sodium atoms and that the lifetime for photoionization is consistent with recent theoretical calculations .
= 0.5 cm -0.6 cm -0.6 cm .
And you have already written the first three sentences of the full article: sodium emission has been previously observed in both long - period and dynamically new comets ( rahe et al .
1976 , sivaraman et al . 1979 , hicks and fink 1997 ) .
although the abundance of sodium in comets is much lower than other observable elements and molecules , it can be used as a tracer of processes acting in the same environment ..
Please generate the next two sentences of the article
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this is because the extremely high efficiency of the sodium atom in resonant scattering of solar radiation makes it detectable even when the column density is low .
for instance the absolute sodium abundance in the io atmosphere is @xmath11% , yet it has been the neutral species most studied after its discovery and is an important tracer of the atmospheric interactions with the plasma torus ( thomas 1992 ) .
|
10,085 |
Suppose that you have an abstract for a scientific paper: we present optical photometry of the low mass x - ray binary systems gx 349 + 2 ( = x1702 - 363 ) and ser x-1 ( = x1837 + 049 ) .
extensive @xmath0 photometry of the faint optical counterpart ( @xmath1 ) to gx 349 + 2 reveals a period of @xmath2 h and half - amplitude 0.2 mag .
this result confirms and extends our previously reported 22 h period ( wachter & margon 1996 ) .
no color change is detected over the orbit , although the limits are modest .
we also report the discovery of two new variable stars in the field of gx 349 + 2 , including a probable w uma system .
ser x-1 is one of the most intense persistent x - ray burst sources known .
it is also one of only three burst systems for which simultaneous optical and x - ray bursts have been observed .
the faint blue optical counterpart mm ser ( @xmath3 ) has long been known to have a companion 2.1 distant .
our images indicate that mm ser is itself a further superposition of two stars , separated by only 1 . at the very least
, the ratio of inferred burst to quiescent optical flux is affected by the discovery of this additional component . in the worst case ,
the wrong object may have previously been assumed as the optical counterpart . .
And you have already written the first three sentences of the full article: little is known about the faint optical counterpart ( @xmath4 ) of the bright bulge z - source gx 349 + 2 .
the one published spectrum of the counterpart is of both low resolution and quality ( penninx & augusteijn 1991 ) and only shows a strong h@xmath5 emission line . from the first photometric study of the system we reported the detection of a possible @xmath6 h period ( wachter & margon 1996 , hereafter paper i ) . at the same time , southwell et al .
( 1996 ) suggested a period of 14 d for gx 349 + 2 from an analysis of the h@xmath7 emission line velocities . in order to resolve this ambiguity and better.
Please generate the next two sentences of the article
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determine the orbital period we undertook a second monitoring campaign of the system .
ser x-1 is one of the most intense persistent x - ray burst sources known .
|
10,086 |
Suppose that you have an abstract for a scientific paper: the lux ( large underground xenon ) detector is a two - phase xenon time projection chamber ( tpc ) designed to search for wimp - nucleon dark matter interactions . as with all noble element detectors , continuous purification of the detector medium is essential to produce a large ( @xmath01ms ) electron lifetime ; this is necessary for efficient measurement of the electron signal which in turn is essential for achieving robust discrimination of signal from background events . in this paper
we describe the development of a novel purification system deployed in a prototype detector .
the results from the operation of this prototype indicated heat exchange with an efficiency above 94% up to a flow rate of 42 slpm , allowing for an electron drift length greater than 1 meter to be achieved in approximately two days and sustained for the duration of the testing period .
noble - liquid detectors , charge transport and multiplication in liquid media , large detector systems for particle and astroparticle physics .
And you have already written the first three sentences of the full article: evidence continues to mount that roughly 23% of the energy density of the universe is constituted of a type of matter which is not baryonic in nature @xcite .
this is commonly referred to as `` dark matter '' , and has become the focus of many research programs .
one of the most popular particle candidates for dark matter is the weakly interacting massive particle , or wimp ..
Please generate the next two sentences of the article
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since one of the defining qualities of dark matter is that it does not interact electromagnetically , its detection requires complex instruments designed to detect rare interactions with great precision .
the lux dark matter project @xcite intends to detect wimps using a two phase liquid - gas xenon tpc detector @xcite .
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10,087 |
Suppose that you have an abstract for a scientific paper: religiosity is one of the most important sociological aspects of populations .
all religions may evolve in their beliefs and adapt to the society developments .
a religion is a social variable , like a language or wealth , to be studied like any other organizational parameter .
several questions can be raised , as considered in this study : e.g. ( i ) from a `` macroscopic '' point of view : how many religions exist at a given time ?
( ii ) from a `` microscopic '' view point : how many adherents belong to one religion ? does the number of adherents increase or not , and how ?
no need to say that if quantitative answers and mathematical laws are found , agent based models can be imagined to describe such non - equilibrium processes .
it is found that empirical laws can be deduced and related to preferential attachment processes , like on evolving network ; we propose two different algorithmic models reproducing as well the data .
moreover , a population growth - death equation is shown to be a plausible modeling of evolution dynamics in a continuous time framework .
differences with language dynamic competition is emphasized . .
And you have already written the first three sentences of the full article: all features of societies ( beliefs , attitudes , behaviors , languages , wealth , etc . )
are due to competition @xcite .
recently the dynamics of world s languages , especially on their disappearing due to competition with other languages @xcite has been of interest ..
Please generate the next two sentences of the article
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it is fair to examine whether such considerations can be applied to religions .
we do not enter into any discussion on the definition of a religion ; we recognize that there are various denominations which can impair data gathering and subsequent analysis ; like many , we admit to put on the same footing religions , philosophies , sects and rituals .
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10,088 |
Suppose that you have an abstract for a scientific paper: janus particles have attracted significant interest as building blocks for complex materials in recent years .
furthermore , capillary interactions have been identified as a promising tool for directed self - assembly of particles at fluid - fluid interfaces . in this paper
, we develop theoretical models describing the behaviour of magnetic janus particles adsorbed at fluid - fluid interfaces interacting with an external magnetic field .
using numerical simulations , we test the models predictions and show that the magnetic janus particles deform the interface in a dipolar manner . we suggest how to utilise the resulting dipolar capillary interactions to assemble particles at a fluid - fluid interface , and further demonstrate that the strength of these interactions can be tuned by altering the external field strength , opening up the possibility to create novel , reconfigurable materials . .
And you have already written the first three sentences of the full article: colloidal janus particles have drawn special attention during the past two decades for their potential in materials science @xcite .
janus particles are characterized by anisotropic surface chemical ( e.g. wetting or catalytic ) or physical ( e.g. optical , electric , or magnetic ) properties at well - defined areas on the particle .
this combination of chemical anisotropy and response to external fields makes janus particles promising building blocks of reconfigurable and programmable self - assembled structures @xcite ..
Please generate the next two sentences of the article
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janus particles strongly adsorb at fluid - fluid interfaces @xcite , making the formation of 2-d structures accessible . for symmetric janus particles composed of hydrophobic and hydrophilic hemispheres ,
the equilibrium contact angle is @xmath0 since each hemisphere immerses in its favourable fluid , and the interface remains flat @xcite .
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10,089 |
Suppose that you have an abstract for a scientific paper: we consider the inflaton as a scalar field described by a non - minimal derivative coupling model with a power law potential .
we study the slow roll inflation , the rapid oscillation phase , the radiation dominated and the recombination eras respectively , and estimate e - folds numbers during these epochs . using these results and recent astrophysical data
we determine the reheating temperature in terms of the spectral index and the amplitude of the power spectrum of scalar perturbations . .
And you have already written the first three sentences of the full article: to solve some dilemmas in the standard model of cosmology such as the flatness , the horizon , the monopoles problems and so on , inflation as an accelerated expansion era in the early universe was introduced by @xcite .
this scenario is now dubbed as old model of inflation , in which the universe underwent a de - sitter expansion in a supercooled unstable false vacuum . afterwards , by proposing a scalar field ( inflaton ) as the source of inflation , a new inflationary model was introduced in @xcite . in this context , inflation was driven by the inflaton which slowly rolled down towards the minimum of its effective potential . to provide enough e - folds number
, the potential must be nearly flat near its minimum ..
Please generate the next two sentences of the article
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the nature of this scalar field has not yet been identified , but a simple possible candidate might be the higgs boson @xcite . to adapt the inflaton to the higgs boson ,
a non - minimally derivative coupling model in which the kinetic term of the inflaton is coupled to the einstein tensor , was proposed in @xcite .
|
10,090 |
Suppose that you have an abstract for a scientific paper: we examine angular distributions of leptons arising from the decay of @xmath0 in inclusive hadroproduction . taking into account feed - down contributions from @xmath1 ,
a flat distribution emerges without fine tuning parameters .
changes in the ratio of direct to total @xmath0 cross sections would change this distribution significantly .
such angular distributions are , therefore , confirmatory tests of the @xmath0 suppression signal for the production of a quark - gluon plasma .
related effects are predicted for the @xmath2 .
@=11 addtoresetequationsection
@=12
# 1to # 1 * quarkonium polarization in non - relativistic qcd + and the quark - gluon plasma * sourendu gupta + theory group , tata institute of fundamental research , + homi bhabha road , bombay 400005 , india . .
And you have already written the first three sentences of the full article: in the hadroproduction of @xmath0 , the angular distribution of the dileptons coming from the decay of the quarkonium is of the form @xmath3 where @xmath4 is the angle ( measured in the rest frame of the quarkonium ) between the direction of motion of the positively charged lepton and the ( lab - frame ) direction of the quarkonium momentum .
as long as the initial particles are unpolarized , there can be no difference in the weights for production of quarkonia with helicities @xmath5 and @xmath6 .
the angular distributions can then be summarized by an `` alignment parameter '' @xcite @xmath7 here @xmath8 is the cross section for production of quarkonia with longitudinal polarization ( @xmath9 ) , and @xmath10 is the total cross section.
Please generate the next two sentences of the article
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. for hadroproduction , @xmath11 is close to zero for all beam and target combinations investigated @xcite , implying that @xmath12 is close to @xmath13 .
the question of angular distributions and alignment has attracted a lot of attention recently . in @xcite
|
10,091 |
Suppose that you have an abstract for a scientific paper: using the exceptional monitoring capabilities of the macho project we present here the optical history of the lmc supersoft source ( sss ) rx j0513.9 - 6951 , for a continuous 3 year period . recurring low states ,
in which the optical brightness drops by up to a magnitude , are observed at quasi - regular intervals .
this provides a crucial insight into the nature of the sss and , in particular , a chance to investigate the poorly understood behaviour of their accretion discs .
analysis of the high state data reveals a small modulation of semi - amplitude @xmath0 0.02 magnitudes at [email protected]@xmath20.00005 days , a period which is consistent with the current `` best '' suggested spectroscopic value . #
1to 0pt#1 accretion , accretion discs binaries : close binaries : spectroscopic x - rays : stars stars : individual : rx j0513.9 - 6951 .
And you have already written the first three sentences of the full article: _ rosat _ observations have considerably enlarged the new class of high luminosity x - ray objects , the so - called `` supersoft sources '' ( ssss ) characterised by their euv temperatures ( trmper 1992 ) .
ssss were first detected in the large magellanic cloud in 1979 - 1980 with the _ einstein _ x - ray observatory ( long , helfand & grabelsky , 1981 ) . until recently ,
little progress had been made in determining the exact nature of these elusive systems , the high level of x - ray absorption rendering them undetectable in the galactic plane ..
Please generate the next two sentences of the article
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most currently known sss are therefore extragalactic and , as such , they are optically faint . the current inventory of supersoft objects ( hasinger 1994 ; cowley et al . 1996 ;
kahabka & trmper 1996 ) is of the order of 11 in the magellanic clouds , 15 in m31 and 7 galactic sources , with candidates existing also in m101 , ngc253 and m33 .
|
10,092 |
Suppose that you have an abstract for a scientific paper: a novel modular high - resolution charged - particle tracking detector design using @xmath0 diameter , round , scintillating fibers and sipm arrays for readout is presented .
the fiber modules consist of 8 layers of 128 fibers , mechanically stabilized by a carbon fiber / rohacell foam structure . a prototype using scintillating fibers with a diameter of @xmath1 and two types of silicon photomultipliers has been tested in a @xmath2 proton beam in late october 2006 at the t9 ps - beamline , cern .
we present the measured spatial resolution , efficiency and signal - over - noise for this setup .
the advantage of this tracker concept is a compact and modular design with low material budget and only little or no cooling requirements depending on the quality of the silicon photomultiplieres . .
And you have already written the first three sentences of the full article: the idea to use scintillating fibers for charged - particle tracking is not new .
several experiments have already successfully built and used scintillating fiber trackers in high - energy and astro - particle physics .
d _ experiment @xcite for example chose to use a scintillating fiber tracker built from @xmath3 thick , multi - clad scintillating fibers , read out by _ visible - light photon counters _ ( vlpc ) ..
Please generate the next two sentences of the article
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the mice experiment took the idea of a scintillating fiber tracker one step further , using @xmath4 thin multiclad fibers , also read out by vlpcs .
the use of vlpcs requires a significant overhead , because they have to be operated in cryostats at temperatures of around @xmath5 .
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10,093 |
Suppose that you have an abstract for a scientific paper: the multiple - planet systems discovered by the kepler mission show an excess of planet pairs with period ratios just wide of exact commensurability for first - order resonances like 2:1 and 3:2 . in principle
, these planet pairs could have both resonance angles associated with the resonance librating if the orbital eccentricities are sufficiently small , because the width of first - order resonances diverges in the limit of vanishingly small eccentricity .
we consider a widely - held scenario in which pairs of planets were captured into first - order resonances by migration due to planet - disk interactions , and subsequently became detached from the resonances , due to tidal dissipation in the planets . in the context of this scenario
, we find a constraint on the ratio of the planet s tidal dissipation function and love number that implies that some of the kepler planets are likely solid .
however , tides are not strong enough to move many of the planet pairs to the observed separations , suggesting that additional dissipative processes are at play . .
And you have already written the first three sentences of the full article: the _ kepler _ space telescope is designed to detect the periodic transits of exoplanets in front of their host stars . based on the data obtained during the first 16 months of kepler s operation , more than 2000 planetary candidates have been identified , analyzed , and published @xcite .
most of these planetary candidates have radii in the range 14 times that of the earth ( @xmath0 ) and orbital periods @xmath1 less than a few months .
the rarity of planets with smaller radii and longer periods is due to observational selection effects ..
Please generate the next two sentences of the article
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although a large fraction of these candidates may indeed be planets , some of them may be due to the blending of background eclipsing binary stars with the light of foreground stars . in the @xmath2-month kepler catalog , there are 361 host stars which bear two or more transiting planetary candidates @xcite , and almost all of them are real multiple - planet systems @xcite .
their orbital configurations contain valuable information on the history of their formation and dynamical evolution .
|
10,094 |
Suppose that you have an abstract for a scientific paper: triggering the electroweak symmetry breaking may not be the only key role played by the higgs boson in particle physics . in a
recently proposed warped five - dimensional @xmath0 gauge - higgs unification model the higgs boson can also constitute the dark matter that permeates the universe .
the stability of the higgs boson in this model is guaranteed in all orders of perturbation theory by the conservation of an _ h - parity _ quantum number that forbids triple couplings to all sm particles .
recent astrophysical data constrain the mass of such a higgs dark matter particle to a narrow window of @xmath1@xmath2 range .
we show that the large hadron collider can observe these higgs bosons in the weak boson fusion channel with about 240@xmath3 of integrated luminosity in that mass range .
the mechanism responsible for the breaking of the electroweak symmetry from @xmath4 to @xmath5 and the necessity of existence of cold dark matter ( cdm ) relics in the universe have motivated a large theoretical effort towards a beyond standard model ( sm ) physics in the last decades .
the electroweak symmetry breaking ( ewsb ) @xcite is achieved in the standard model ( sm ) and in many of its extensions introducing scalars whose couplings to fermions and gauge bosons generate their masses . within sm there
remains a scalar particle in the spectrum : the higgs boson .
one of the major goals of the lhc is the detection and the study of the properties of the higgs boson which , in this respect , constitutes a window for the whole ewsb mechanism and hopefully for the high energy structure of the new physics . on the other hand ,
the indirect detection of the dark matter particle at colliders ( whose existence has been established by the wmap experiment @xcite ) is important to establish the nature of dark matter and , again , constitute a mean to decide between new physics models . in a recent work @xcite an interesting connection between these two phenomena
was proposed : the higgs boson could....
And you have already written the first three sentences of the full article: the signal total cross section without cuts is @xmath61 for a @xmath62 higgs boson at the @xmath63 lhc while the total background cross section amounts to @xmath64 . as we anticipated in section
[ sec : model ] the @xmath65 rate in this gauge - higgs unification model is about 5 times larger than its sm analog whose wbf production cross section for a @xmath6 higgs mass is @xmath66 .
the same set of parameters , factorization scale and parton distribution functions for the higgs dark matter case were used in this computation ..
Please generate the next two sentences of the article
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.signal and background cross sections after basic cuts ( [ eq : cuts ] ) and basic cuts plus the @xmath57 cut of eq .
( [ eq : cutphi ] ) . the survival probability after a soft central jet veto
|
10,095 |
Suppose that you have an abstract for a scientific paper: it is shown that on the de sitter manifolds the tachyonic geodesics are restricted such that the classical tachyons can not exist on this manifold at any time . on the contrary , the theory of the scalar quantum tachyons is free of any restriction .
the tachyonic scalar and dirac plane waves are deduced in this geometry , pointing out that these are well - defined , behaving as tempered distributions at any moment .
pacs : 04.62.+v amssym.tex keywords : de sitter ; classical tachyons ; scalar tachyons ; dirac tachyons . .
And you have already written the first three sentences of the full article: in special relativity one knows three types of particles , tardyons ( subluminal ) , light - like and tachyons ( superluminal ) .
the first two types of particles are of our world , inside the light - cone , while the tachyons seems to live in another one , outside the light - cone .
these two worlds seems to be completely separated as long as there are no direct physical evidences about the tardyon - tachyon interactions . for this reason the tachyons are the most attractive hypothetical objects for speculating in some domain in physics where we have serious difficulties in building coherent theories ..
Please generate the next two sentences of the article
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we mention , as an example , the presumed role of the tachyons in the early brane cosmology @xcite .
however , here we do not intend to comment on this topics , restricting ourselves to analyze , from the mathematical point of view , the possibility to meet classical or quantum scalar or dirac tachyons on the de sitter backgrounds .
|
10,096 |
Suppose that you have an abstract for a scientific paper: we formulate two types of extension of the large deviation theory initiated by bahadur in a non - regular setting . one can be regarded as a bound of the point estimation , the other can be regarded as the limit of a bound of the interval estimation .
both coincide in the regular case , but do not necessarily coincide in a non - regular case . using the limits of relative rnyi entropies , we derive their upper bounds and give a necessary and sufficient condition for the coincidence of the two upper bounds .
we also show the attainability of these two bounds in several non - regular location shift families . *
two non - regular extensions of the large deviation bound * * masahito hayashi + laboratory for mathematical neuroscience , brain science institute , riken * keywords : non - regular family , large deviation , relative rnyi entropy , point estimation , interval estimation .
And you have already written the first three sentences of the full article: as discussed by bahadur @xcite , fisher information characterizes the limit of the decreasing rate of the tail probability of the optimal estimator .
however , when the kullback - leibler ( kl ) divergence diverges or fisher information can not be defined , this can not be applied . as an alternative information quantity between two probabilities
, we can use the relative rnyi entropies @xmath0 , which play an important role in simple hypothesis testing ..
Please generate the next two sentences of the article
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( hoeffding @xcite , chernoff @xcite ) in general , for a probability distribution family @xmath1 , the relative rnyi entropies @xmath2 tend to @xmath3 when @xmath4 goes to @xmath3 , but their order is not necessarily @xmath5 . in this paper , we treat a large deviation theory , which can be applied to such a case .
the importance of the relative rnyi entropies @xmath2 was pointed out by akahira @xcite from the viewpoint of information loss in a non - regular family .
|
10,097 |
Suppose that you have an abstract for a scientific paper: the hyperbolic dodecahedral space of weber and seifert has a natural non - positively curved cubulation obtained by subdividing the dodecahedron into cubes .
we show that the hyperbolic dodecahedral space has a @xmath0sheeted irregular cover with the property that the canonical hypersurfaces made up of the mid - cubes give a very short hierarchy .
we also describe the natural cubulation and covers of the spherical dodecahedral space ( aka poincar homology sphere ) . .
And you have already written the first three sentences of the full article: a _ cubing _ of a 3manifold @xmath1 is a decomposition of @xmath1 into euclidean cubes identified along their faces by euclidean isometries .
this gives @xmath1 a singular euclidean metric , with the singular set contained in the union of all edges .
the cubing is _ non - positively curved _ if the dihedral angle along each edge in @xmath1 is at least @xmath2 and each vertex satisfies gromov s _ link condition _ :.
Please generate the next two sentences of the article
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the link of each vertex is a triangulated sphere in which each 1cycle consists of at least 3 edges , and if a 1cycle consists of exactly 3 edges , then it bounds a unique triangle . in this case
, we say that @xmath1 has an _
|
10,098 |
Suppose that you have an abstract for a scientific paper: measurements of cosmic rays by experiments such as atic , cream , and pamela indicate a hardening of the cosmic - ray energy spectrum at tev energies . in our recent work @xcite
, we showed that the hardening can be due to the effect of nearby supernova remnants .
we showed it for the case of protons and helium nuclei . in this paper , we present an improved and more detailed version of our previous work , and extend our study to heavier cosmic - ray species such as boron , carbon , oxygen , and iron nuclei .
unlike our previous study , the present work involves a detailed calculation of the background cosmic rays and follows a consistent treatment of cosmic - ray source parameters between the background and the nearby components .
moreover , we also present a detailed comparison of our results on the secondary - to - primary ratios , secondary spectra , and the diffuse gamma - ray spectrum with the results expected from other existing models , which can be checked by future measurements at high energies .
[ firstpage ] cosmic rays diffusion ism : supernova remnants ism : general .
And you have already written the first three sentences of the full article: recent measurements of cosmic rays by the atic @xcite , cream @xcite , and pamela @xcite experiments have indicated the presence of hardening in the energy spectra of protons , helium and heavier nuclei at tev energies .
the observed hardening does not seem to be in good agreement with general theoretical predictions .
based on the simple linear theory of diffusive shock acceleration ( dsa ) of cosmic rays @xcite , and the nature of cosmic - ray transport in the galaxy ( see e.g. , @xcite ) , the cosmic - ray spectrum is expected to follow a single power - law at least up to @xmath0 pev , the so - called cosmic - ray knee " ..
Please generate the next two sentences of the article
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different explanations for the spectral hardening have been proposed .
most of these explanations suggest either hardening in the cosmic - ray source spectrum or changes in the propagation properties in the galaxy .
|
10,099 |
Suppose that you have an abstract for a scientific paper: at present , ten years after they were first discovered , ten accreting millisecond pulsars are known .
i present a study of the aperiodic x - ray variability in three of these systems , which led to the discovery of simultaneous khz quasi periodic oscillations in xte j1807294 and extremely strong broadband noise at unusually low variability frequencies in igr j00291 + 5934 .
furthermore , we classified swift j1756.92508 as an atoll source and measured in its 2007 outburst spectral and variability properties typical of the extreme island state .
i also give detailed estimates of the total fluence during the studied outbursts .
address = astronomical institute `` anton pannekoek '' , university of amsterdam , kruislaan 403 , nl-1098 sj amsterdam , netherlands .
mail to : [email protected] .
And you have already written the first three sentences of the full article: during the last decade accreting millisecond pulsars ( amps ) have revealed a number of interesting phenomena and have opened a new window to the physics of accretion onto neutron stars ( nss ) .
the first of such systems was discovered by ( * ? ? ?
* sax j1808.43658 ) , presenting the first prove of an accreting neutron star having both millisecond spin period and dynamically important magnetic field ..
Please generate the next two sentences of the article
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ten amps have been discovered to date , and in three of them millisecond x - ray pulsations have been seen to appear in and disappear from the persistent emission , producing predominant ( hete j1900.1 - 2455 ; * ? ? ?
* ) intermittent ( sax j1748.9 - 2021 ; * ? ? ?
|
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