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Suppose that you have an abstract for a scientific paper: we study certain stationary and time - evolution problems of trapped bose - einstein condensates of weakly interacting alkali atoms described by a nonlinear gross - pitaevskii ( gp ) equation .
we suggest a pseudospectral method involving laguerre polynomials to solve the time dependent gp for a spherically symmetric trap potential . the radial wavefunction and energy values have been calculated for different nonlinearities .
further , we study the effect of suddenly changing the interatomic scattering length or harmonic oscillator trap potential in the condensate .
we also investigate the frequency of oscillation due to the variation in the strength of nonlinearity .
bose - einstein condensation , pseudospectral method .
And you have already written the first three sentences of the full article: experimental realization@xcite of bose - einstein condensates ( becs ) in dilute weakly - interacting trapped bosonic atoms at ultra - low temperature initiated intense theoretical effort to describe the properties of the condensate .
the properties of a condensate at zero temperature are usually described by the time - dependent , nonlinear , mean - field gross - pitaevskii ( gp ) equation@xcite .
the effect of the interatomic interaction ( few - body correlation ) leads to a nonlinear term in the gp equation which complicates the solution procedure ..
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although there have been previous studies of the solution of the gp equation for stationary or time - independent problems , virtually all time - dependent studies in realistic cases , e.g. , in three space dimensions , have employed approximate approaches rather than exact numerical solution of the gp equation .
a numerical study of the time - dependent gp equation is of interest , as this can provide solution to many stationary and time - evolution problems .
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11,201 |
Suppose that you have an abstract for a scientific paper: because diffusion typically involves symmetric interactions , scant attention has been focused on studying asymmetric cases . however , important networked systems underlain by diffusion ( e.g. cortical networks and www ) are inherently directed . in the case of undirected diffusion , it can be shown that the steady - state probability of the random walk dynamics is fully correlated with the degree , which is no longer true for directed networks .
we investigate the relationship between such probability and the inward node degree in modular networks , which we call _ efficiency_. our findings show that the efficiency of a given community depends mostly on the balance between its ingoing and outgoing connections . in addition , we derive analytical expressions to show that neither the internal degree nor the communities topology play a crucial role in their efficiency .
the results are illustrated with respect to the macaque cortical network , providing subsidies for improving transportation and communications systems . .
And you have already written the first three sentences of the full article: diffusion is one of the most fundamental dynamics in physics . in addition to being ubiquitous
, diffusion also underlies important non - linear systems such as turing reaction - diffusion , schrdinger , fokker - planck , and navier - stokes equations . because these systems typically present symmetric interactions
, few works have addressed the asymmetric counterpart ..
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however , important networked systems in biology ( e.g. cortical and metabolic networks ) , transportation ( e.g. city traffic ) , and communications ( e.g. www and email networks ) are typically directed and underlain by diffusion @xcite .
a particularly important property of such systems is how the asymptotic probability of the random walk dynamics ( activation ) can be predicted from intrinsic topological features .
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11,202 |
Suppose that you have an abstract for a scientific paper: we consider the observability model in networks with arbitrary topologies .
we introduce a system of coupled nonlinear equations , valid under the locally tree - like ansatz , to describe the size of the largest observable cluster as a function of the fraction of directly observable nodes present in the network .
we perform a systematic analysis on 95 real - world graphs and compare our theoretical predictions with numerical simulations of the observability model .
our method provides almost perfect predictions in the majority of the cases , even for networks with very large values of the clustering coefficient .
potential applications of our theory include the development of efficient and scalable algorithms for real - time surveillance of social networks , and monitoring of technological networks .
the state of an entire networked dynamical system can be determined by monitoring or dominating the states of a limited number of nodes in the network @xcite .
a power - grid network can be observed in real time by placing phasor measurement units to a selection of nodes in the network @xcite .
routing tables in mobile ad - hoc networks rely on gateway nodes to form connected dominating sets used as backbones for communication @xcite .
disease outbreaks in urban environments can be efficiently detected by placing sensors on specific locations visited by potentially infected individuals @xcite .
whereas all these examples markedly differ in their underlying dynamics , from the structural point of view , they can all be framed in terms of the so - called network observability model @xcite . in this model , placing an observer on one node can make the node itself and all its nearest neighbors observable .
nodes in the network can therefore assume three different states : ( i ) directly observable , if hosting an observer ; ( ii ) indirectly observable , if being the first neighbor of an observer ; ( iii ) or not observable , otherwise .
observable , either directly or indirectly ,....
And you have already written the first three sentences of the full article: in the main text , we used the fact that @xmath76 = \sum _ { \{s_r\ } , r \in \mathcal{q } } \ ; \prod_{q \in \mathcal{q } } \ , [ \phi ( 1 - a_q ) ] ^{s_q } \ ; [ ( 1 - \phi ) ( 1 - b_q ) ] ^{1 - s_q } \ ; .
\label{eq : app1}\ ] ] note that eq .
( [ eq : app1 ] ) is a more general version of eq ..
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( [ eq:4 ] ) .
we recall that sum on the r.h.s .
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11,203 |
Suppose that you have an abstract for a scientific paper: recently , researches performed by two groups have revealed that the magnetar spin - down energy injection model with full energy trapping can explain the early - time light curves of sn 2010gx , sn 2013dg , lsq12dlf , sss120810 and css121015 , but fails to fit the late - time light curves of these superluminous supernovae ( slsne ) .
these results imply that the original magnetar - powered model is challenged in explaining these slsne .
our paper aims to simultaneously explain both the early- and late - time data / upper limits by considering the leakage of hard emissions .
we incorporate quantitatively the leakage effect into the original magnetar - powered model and derive a new semi - analytical equation . comparing the light curves reproduced by our revised magnetar - powered model to the observed data and/or upper limits of these five slsne , we found that the late - time light curves reproduced by our semi - analytical equation are in good agreement with the late - time observed data and/or upper limits of sn 2010gx , css121015 , sn 2013dg and lsq12dlf and the late - time excess of sss120810 , indicating that the magnetar - powered model might be responsible for these slsne and that the gamma ray and x - ray leakage are unavoidable when the hard photons were down - comptonized to softer photons . to determine the details of the leakage effect and unveil the nature of slsne , more high quality bolometric
light curves and spectra of slsne are required . .
And you have already written the first three sentences of the full article: in recent years , several wide field optical transient projects , e.g. , the palomar transient factory ( ptf ; * ? ? ? * ; * ? ? ?
* ) , the panoramic survey telescope & rapid response system ( pan - starrs1 , ps1 ; * ? ? ?
* ; * ? ? ?.
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* ) , the catalina real - time transient survey ( crts ; * ? ? ?
* ) , la silla quest supernova survey ( lsq ; * ? ? ?
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11,204 |
Suppose that you have an abstract for a scientific paper: emission - line variability data on ngc 5548 argue strongly for the existence of a mass of order @xmath0within the inner few light days of the nucleus in the seyfert 1 galaxy ngc 5548 .
the time - delayed response of the emission lines to continuum variations is used to infer the size of the line - emitting region , and these determinations are combined with measurements of the doppler widths of the variable line components to estimate a virial mass .
the data for several different emission lines spanning an order of magnitude in distance from the central source show the expected @xmath1 correlation and are consistent with a single value for the mass . .
And you have already written the first three sentences of the full article: since the earliest days of quasar research , supermassive black holes ( sbhs ) have been considered to be a likely , if not the most likely , principal agent of the activity in these sources .
evidence for the existence of sbhs in active galactic nuclei ( agns ) , and indeed in non - active nuclei as well , has continued to accumulate ( e.g. , kormendy & richstone 1995 ) . in the specific case of agns ,
probably the strongest evidence to date for sbhs has been keplerian motions of megamaser sources in the seyfert galaxy ngc 4258 ( miyoshi et al ..
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1995 ) and asymmetric fek@xmath3 emission in the x - ray spectra of agns ( e.g. , tanaka et al .
1995 ) , though the latter is still somewhat controversial as the origin of the fek@xmath3 emission has not been settled definitively .
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11,205 |
Suppose that you have an abstract for a scientific paper: tensor products of @xmath0 random unitary matrices of size @xmath1 from the circular unitary ensemble are investigated .
we show that the spectral statistics of the tensor product of random matrices becomes poissonian if @xmath2 , @xmath1 become large or @xmath0 become large and @xmath3 .
@xmath4institute of mathematics , university of warsaw , banacha 2 , 02 - 097 warsaw , poland .
+ ` [email protected] ` + + @xmath5the marian smoluchowski institute of physics , jagiellonian university , reymonta 4 , 30 - 059 cracow , poland . ` [email protected] ` + + @xmath6center of theoretical physics , polish academy of sciences , al .
lotnikow 32/46 , 02 - 668 warsaw , poland . ` [email protected] ` , ` [email protected] ` + + @xmath7school of mathematics , university of minnesota and faculty of mathematics , weizmann institute of science , pob 26 , rehovot 76100 , israel . `
[email protected] ` * 2010 mathematics subject classification . *
60b20 , 15b52 . * key words and phrases . * random matrices , circular unitary ensemble , tensor product . .
And you have already written the first three sentences of the full article: random matrices proved their usefulness in describing the spectra of quantum systems , the classical analogues of which are chaotic @xcite .
in particular , spectral properties of the evolution operator of a deterministic quantum chaotic system seem to coincide with predictions obtained for the circular ensembles of random unitary matrices .
the symmetry properties of the system determine which ensemble of random matrices is applicable . specifically ,.
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if the physical system does not possess any time - reversal symmetry , one uses random unitary matrices of the circular unitary ensemble ( cue ) .
statistical predictions obtained for ensembles of random matrices are also useful in analyzing generic properties of entangled states @xcite . in the theory of quantum information
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11,206 |
Suppose that you have an abstract for a scientific paper: by employing hopf s functional method , we find the exact characteristic functional for a simple nonlinear dynamical system introduced by orszag .
steady - state equal - time statistics thus obtained are compared to direct numerical simulation .
the solution is both non - trivial and strongly non - gaussian . .
And you have already written the first three sentences of the full article: a nonlinear dynamical system can be completely deterministic and its solution unique , yet two trajectories that begin close to one another may diverge significantly in a finite time .
such sensitive dependence on initial conditions sets a fundamental limit on predictive accuracy , as these systems forget their initial conditions after a short time .
probabilistic descriptions , by contrast , avoid the details of time - evolution , and instead answer meaningful statistical questions . as a canonical example , experimental measurements of turbulent velocity fluctuations show disordered and unpredictable behavior yet reproducible statistical properties ..
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the complexity of the flow contrasts with the smoothness of averaged quantities like the energy spectrum , demonstrating that statistical descriptions may be both economical and insightful . to accumulate statistics
, numerical simulations may implement ensemble averages over initial condition and/or long - time integration , yet the computational work required to carry out such calculations can be prohibitive in the case of high - dimensional systems .
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11,207 |
Suppose that you have an abstract for a scientific paper: past years have brought an increasingly wider recognition of the ubiquity of relativistic outflows ( jets ) in galactic nuclei , which has turned jets into an effective tool for investigating the physics of nuclear regions in galaxies .
a brief summary is given here of recent results from studies of jets and nuclear regions in several active galaxies with prominent outflows . .
And you have already written the first three sentences of the full article: substantial progress achieved during the past decade in studies of active galactic nuclei ( see @xcite for a review of recent results ) has brought an increasingly wider recognition of the ubiquity of relativistic outflows ( jets ) in galactic nuclei @xcite turning them into an effective probe of nuclear regions in galaxies @xcite .
emission properties , dynamics , and evolution of an extragalactic jet are intimately connected to the characteristics of the supermassive black hole , accretion disk and broad - line region in the nucleus of the host galaxy @xcite .
the jet continuum emission is dominated by non - thermal synchrotron and inverse - compton radiation @xcite ..
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the synchrotron mechanism plays a more prominent role in the radio domain , and the properties of the emitting material can be assessed using the turnover point in the synchrotron spectrum @xcite , synchrotron self - absorption @xcite , and free - free absorption in the plasma @xcite .
high - resolution radio observations access directly the regions where the jets are formed @xcite , and trace their evolution and interaction with the nuclear environment @xcite .
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11,208 |
Suppose that you have an abstract for a scientific paper: we study the effect of an inhomogeneous out - of - plane magnetic field on the behaviour of 2d spatially indirect excitons . due to the difference of the magnetic field acting on electrons and holes the total lorentz force affecting the center of mass motion of an
indirect exciton appears .
consequently , an indirect exciton acquires an effective charge proportional to the gradient of the magnetic field .
the appearance of the lorentz force causes the hall effect for neutral bosons which can be detected by measurement of the spatially inhomogeneous blueshift of the photoluminescence using counterflow experiment . .
And you have already written the first three sentences of the full article: the interaction of electrically charged particles with an external magnetic field leads to a variety of phenomena in condensed matter physics .
the classical examples are integer and fractional quantum hall effects which have been studied extensively both experimentally and theoretically in the last decades.@xcite in the domain of cold atoms the magnetic field can also change the behavior of the system , _ e.g. _ driving the bec - bcs transition by means of feshbach resonances.@xcite however , as cold atoms are neutral objects , the application of the magnetic field does not lead to an appearance of the lorentz force and hall effect .
meanwhile , the possibility of generation of an artificial magnetic field in the atomic systems was proposed.@xcite this phenomenon is based on the effect of the geometric ( berry ) phase and requires illumination of the sample by several laser beams tuned in resonance with atomic transitions.@xcite this has opened the way for the observation of the analog of quantum hall effect for neutral cold bosons and fermions . in solid state physics there exist electrically neutral bosonic particles similar to atoms . these are excitons.
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bounded electron - hole pairs .
the impact of excitons onto optical and transport properties of semiconductor materials have been studied intensively,@xcite and the possibility of bose - einstein condensation for excitons was consider theoretically long time ago.@xcite however , an experimental observation of exciton bec still remains an open question.@xcite a great step forward was achieved by using the effect of strong exciton - photon coupling in semiconductor microcavities.@xcite hybrid light - matter quasiparticles called exciton - polaritons revealed intriguing physical properties and the formation of a macroscopically coherent state of polaritons was experimentally reported.@xcite however , the question of how it is connected with the standard bec picture is still under debate.@xcite indeed , usually cavity polaritons have a very short lifetime ( not exceeding tens of picoseconds ) which prevents the possibility of full thermalization of the system .
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11,209 |
Suppose that you have an abstract for a scientific paper: we present the spectroscopic analysis of a large sample of late - m , l , and t dwarfs from the united kingdom deep infrared sky survey . using the yjhk photometry from the large area survey and the red - optical photometry from the sloan digital sky survey we selected a sample of 262 brown dwarf candidates and we have followed - up 196 of them using the echelle spectrograph x - shooter on the very large telescope . the large wavelength coverage ( @xmath0 m ) and moderate resolution ( r@xmath1 ) of x - shooter allowed us to identify peculiar objects including 22 blue l dwarfs , 2 blue t dwarfs , and 2 low gravity m dwarfs . using a spectral indices - based technique we identified 27 unresolved binary candidates , for which we have determined the spectral type of the potential components via spectral deconvolution .
the spectra allowed us to measure the equivalent width of the prominent absorption features and to compare them to atmospheric models .
cross - correlating the spectra with a radial velocity standard , we measured the radial velocity for our targets , and we determined the distribution of the sample , which is centred at [email protected] km s@xmath3 with a dispersion of 31.5 km s@xmath3 . using our results we estimated the space density of field brown dwarfs and compared it with the results of numerical simulations . depending on the binary fraction
, we found that there are @xmath4 to @xmath5 objects per cubic parsec in the l4-l6.5 range , @xmath6 to @xmath4 objects per cubic parsec in the l7-t0.5 range , and @xmath7 to @xmath8 objects per cubic parsec in the t1-t4.5 range .
we notice that there seem to be an excess of objects in the l to t transition with respect to the late t dwarfs , a discrepancy that could be explained assuming a higher binary fraction than expected for the l to t transition , or that objects in the high - mass end and low - mass end of this regime form in different environments , i.e. following different initial mass functions .
[ firstpage ] brown dwarfs -....
And you have already written the first three sentences of the full article: the study of sub - stellar objects still presents a number of open questions . a very intriguing one is the understanding of the physical and chemical processes taking place at the transition between the spectral types l and t. the sharp near - infrared colour turnaround that characterizes the transition between the spectral types l7 to t5 is particularly challenging to model . the dust settling and the onset of the methane and molecular hydrogen absorption
are now believed to be the main causes of the turnaround , but the details of these processes , in particular of the dust settling , are still not well understood .
a number of different scenarios have been proposed ( e.g. * ? ? ?.
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* ; * ? ? ?
* ; * ? ? ?
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11,210 |
Suppose that you have an abstract for a scientific paper: equilibrium numerical data on the three dimensional bimodal ( @xmath0 ) interaction ising spin glass up to size @xmath1 show that corrections to scaling , which are known to be strong , behave in a non - monotonic manner with size .
extrapolation to the infinite size thermodynamic limit is difficult ; however the large @xmath2 data indicate that the ordering temperature @xmath3 lies significantly higher than the values which have been estimated from previous numerical work limited to smaller sizes . in view of the present results it is at the least premature to conclude that the three dimensional bimodal and gaussian ising spin glasses lie in the same universality class . .
And you have already written the first three sentences of the full article: renormalization group theory ( rgt ) provides an explanation of the physical origin of the critical exponents and of the universality classes for standard second order transitions which is one of the most remarkable achievements of statistical physics .
the universality rules state that the critical exponents depend only on a small number of basic parameters @xcite , essentially the dimension of space @xmath4 , the range of interaction , and the number of order parameter components @xmath5 .
physically , the critical parameters should not depend on the details of the short range interactions ..
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the few known and well understood exceptions to universality concern mainly rare marginal cases , such as certain regularly frustrated spin systems in two dimensions where critical exponents vary continuously with the value of a control parameter .
it should also be kept in mind that if the specific heat exponent @xmath6 is positive for pure ferromagnets , disorder induces another universality class@xcite .
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11,211 |
Suppose that you have an abstract for a scientific paper: coherent @xmath0 and @xmath1 production in low energy neutrino reactions is discussed in the framework of the partially conserved axial vector current theory ( pcac ) . the role of lepton mass effects in suppressing the @xmath0 production
is emphasized . instead of using models of pion nucleus scattering ,
the available data on pion carbon scattering are implemented for an analysis of the pcac prediction .
our results agree well with the published upper limits for @xmath0 production but are much below the recent miniboone result for @xmath1 production . .
And you have already written the first three sentences of the full article: the availability of high intensity neutrino beams with energies up to a few gev opens the way to precise investigation of neutrino oscillations .
essential for these experiments is a detailed understanding of all low energy neutrino reactions especially single pion production in charged ( cc ) and neutral ( nc ) current reactions .
coherent pion production off nuclei , e.g. in @xmath2 constitutes an especially interesting subsample not only because it is a significant background to the @xmath3 oscillation search but also because it is deeply rooted in fundamental physics via adler s pcac theorem @xcite which connects forward neutrino scattering with the pion nucleon cross section ..
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our starting point is the general expression for inelastic neutrino scattering and @xmath4 are the fermi coupling constant and the cabbibo angle . ]
@xmath5 \label{eq:1}\ ] ] already derived by lee and yang @xcite in 1962 for zero mass of the outgoing lepton .
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11,212 |
Suppose that you have an abstract for a scientific paper: using the cloudy_3d code ( morisset , this conference ) , we run a set of models to build a catalog of emission line profiles of pne .
the goal is to cover the main morphologies ( spherical , ellipsoidal , bipolar , thin or thick shells ) and to compute profiles changing the orientation of the nebula , the expansion velocity law ( including or not turbulence ) , the position / size of the aperture .
the results is a huge set of profiles and pv - diagrams that can be compared to observations as a help to derive morpho - kinematical properties of real objects . .
And you have already written the first three sentences of the full article: it is possible to define spherical , ellipsoidal and bipolar morphologies in a simple way : the inner surface of the nebula is defined as the merge of 2 ellipsoids intersecting in the equatorial plane .
only 2 parameters are then needed : ellipticity _ e _ and bipolarity _ b _ ( distance between the lobe centers and the center of the nebula ) .
b_=0 , the nebula is spherical or ellipsoidal ..
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we run a set of models to build the catalog .
we use 5 shapes ( spherical , ellipsoidal , and 3 kind of bipolar , changing the ellipticity of the lobes ) , 2 shell sizes ( thin and thick ) and 3 laws for the angular dependence of the inner hydrogen density .
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11,213 |
Suppose that you have an abstract for a scientific paper: consider a frictionless surface @xmath0 in a gravitational field that need not be uniform . given two points @xmath1 and @xmath2 on @xmath0 ,
what curve is traced out by a particle that starts at @xmath1 and reaches @xmath2 in the shortest time ?
this paper considers this problem on simple surfaces such as surfaces of revolution and solves the problem two ways : first , we use conservation of mechanical energy and the euler - lagange equation ; second , we use geometrical optics and the eikonal equation .
we conclude with a discussion of the relativistic effects at relativistic velocities .
this paper contains the results in the first author s undergraduate thesis codirected by the second and third authors ] .
And you have already written the first three sentences of the full article: in 1696 , johann bernouli posed the following brachistochrone problem _ find the shape of the curve down which a bead sliding from rest and accelerated by gravity will fall from one point to another in the least time .
_ this problem assumes that the particle is falling on a vertical plane in a uniform gravitational field .
sir isaac newton , gottfried leibniz , guillaume de lhospital , jakob bernouli , and johann bernouli showed that the solution is a cycloid , the curve traced out by a point on the rim of a rolling circle , see dunham @xcite ..
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solutions of the classical brachistochrone problem typically use techniques of calculus of variations , see gelfand and fomin @xcite , or geometrical optics , see erlichson @xcite .
the problem of finding brachistochrone curves with coulomb friction lying on a vertical plane in a uniform gravitational field has been discussed by ashby et al .
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11,214 |
Suppose that you have an abstract for a scientific paper: various quantities of an attractively interacting fermion system at the unitary limit are determined by extrapolating monte carlo results of low - density neutron matter .
smooth extrapolation in terms of @xmath0 ( @xmath1 is the fermi momentum , and @xmath2 is the @xmath3 scattering length ) is found with the quantities examined : the ground - state energy , the pairing gap at @xmath4 , and the critical temperature of the normal - to - superfluid phase transition .
we emphasize proximity of the physics of low - density neutron matter to that at the unitary limit .
the extrapolated quantities are in a reasonable agreement with those in the literature . .
And you have already written the first three sentences of the full article: in our previous paper @xcite , we reported a monte carlo calculation of thermodynamic properties of low - density neutron matter by using nuclear effective field theory ( eft ) @xcite .
as pairing in neutron matter is strong , neutron matter is a strongly correlated fermionic system .
we firmly established that low - density neutron matter is in the state of bcs - bose - einstein condensation ( bec ) crossover @xcite instead of a bcs - like state , the standard description in nuclear physics @xcite ..
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the crossover state of low - density neutron matter is actually an expected one from studies of the bcs - bec crossover over the past decade .
the pairing strength of an attractively interacting ( therefore unstable ) fermion system is characterized by a product of the two physical parameters , the fermi momentum @xmath1 and the ( @xmath5-wave ) scattering length @xmath2 @xcite . in terms of @xmath6 , the state of the bcs limit
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11,215 |
Suppose that you have an abstract for a scientific paper: a binary word is a map @xmath0 , and the set of factors of @xmath1 with length @xmath2 is @xmath3 .
a word is _ sturmian _ if @xmath4 for every @xmath5 .
we show that the sum of the heights ( also known as hamming weights ) of the @xmath6 factors with length @xmath2 of a binary sturmian word has the same parity as @xmath2 , independent of @xmath1 .
many facts are known about the factors of length @xmath2 of a sturmian word @xmath1 . among the many noteworthy results
are : that @xmath7 is closed under reversals ( the map that takes @xmath8 to @xmath9 ) @xcite*prop 2.1.19 ; that the volume of the convex hull of @xmath7 is @xmath10 , independent of @xmath1 @xcite*thm 1.1 ; and that as @xmath1 varies over all sturmian words , @xmath7 takes on @xmath11 values .
we direct the reader to either @xcite*chap 9 or @xcite*chap 2 for an introduction to sturmian words . to these
we add [ thm : main ] for every binary sturmian word @xmath1 and every positive integer @xmath2 , @xmath12 where @xmath13 is the number of components of @xmath14 that are ` 1 ' . a natural approach to proving this is to observe that since @xmath7 is closed under reversal , we can pair off non - palindrome factors that have the same height @xmath13 , and therefore it suffices to consider only the palindromes in @xmath7 . moreover , if a palindrome has even length , then it must have even height , and so the ` even-@xmath2 case ' of our theorem does follow easily from the ` closure under reversal ' property . when @xmath2 is odd , the situation is more complicated as a palindrome may have even or odd weight , and there are always two @xcite : @xmath15 where @xmath16 is a particular sturmian word defined below .
our proof does not follow this line , and does not make use of closure under reversal .
this result ( and other computations ) suggests that the eigenvalues of the gram matrix @xmath17 , where @xmath18 , may have structure .
note that the eigenvalues of a gram matrix do not depend on the ordering of the vectors....
And you have already written the first three sentences of the full article: let @xmath23 denote the floor of @xmath24 , and @xmath25 the fractional part of @xmath24 , i.e. , @xmath26 .
define @xmath27 , which counts the number of integers in @xmath28 that are ` better ' denominators for approximating @xmath29 from below .
our proof proceeds by connecting the sum in theorem [ thm : main ] to @xmath30 ( for some @xmath29 ) , finding a recurrence satisfied by @xmath30 , and then reducing that recurrence modulo 2 . the characteristic word with slope @xmath29.
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is defined by @xmath31 if @xmath29 is irrational , then @xmath32 is a sturmian word @xcite*thm 2.1.13 .
it is known @xcite*thm 2.1.3 , prop 2.1.18 that for every binary sturmian word @xmath1 and natural number @xmath2 , there is an @xmath33 with @xmath34 , and so it suffices for our purposes to consider characteristic words , and to write @xmath35 .
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11,216 |
Suppose that you have an abstract for a scientific paper: we report the tentative detection of the near - infrared emission of the hot jupiter wasp-12b with the low - resolution prism on irtf / spex . we find a @xmath0 contrast color of , corresponding to a blackbody of temperature and consistent with previous , photometric observations .
we also revisit s energy budget on the basis of secondary eclipse observations : the dayside luminosity is a relatively poorly constrained @xmath1 erg s@xmath2 , but this still allows us to predict a day / night effective temperature contrast of @xmath3,000 k ( assuming @xmath4 ) .
thus we conclude that probably does not have both a low albedo and low recirculation efficiency .
our results show the promise and pitfalls of using single - slit spectrographs for characterization of extrasolar planet atmospheres , and we suggest future observing techniques and instruments which could lead to further progress . limiting systematic effects include the use of a too - narrow slit on one night which observers could avoid in the future and chromatic slit losses ( resulting from the variable size of the seeing disk ) and variations in telluric transparency which observers can not control .
single - slit observations of the type we present remain the best option for obtaining @xmath5 spectra of transiting exoplanets in the brightest systems .
further and more precise spectroscopy is needed to better understand the atmospheric chemistry , structure , and energetics of this , and other , intensely irradiated planet . .
And you have already written the first three sentences of the full article: transiting extrasolar planets allow the exciting possibility of studying the intrinsic physical properties of these planets .
the last several years have seen rapid strides in this direction , with measurements of precise masses and radii , detection of numerous secondary eclipses and phase curves , and the start of ground - based optical spectroscopy @xcite . though ground - based , near - infrared ( nir ) photometry of exoplanets is becoming commonplace , until recently there were no successful detections via ground - based nir spectroscopy @xcite .
several groups have employed high - resolution spectrographs with some form of template cross - correlation @xcite with varying degrees of success ..
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though cross - correlation provides a method to test for the detection of a particular model , it has the significant drawback that it does not provide a model - independent measurement .
furthermore , such observations require high - resolution cryogenic spectrographs on large - aperture telescopes .
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11,217 |
Suppose that you have an abstract for a scientific paper: * abstract : * we investigate the gravitational lensing scenario due to schwarzschild - like black hole surrounded by quintessence ( kiselev black hole ) .
we work for the special case of kiselev black hole where we take the state parameter @xmath0 . for the detailed derivation and analysis of the bending angle involved in the deflection of light
, we discuss three special cases of kiselev black hole : nonextreme , extreme and naked singularity .
we also calculate the approximate bending angle and compare it with the exact bending angle .
we found the relation of bending angles in the decreasing order as : naked singularity , extreme kiselev black hole , nonextreme kiselev black hole and schwarzschild black hole . in the weak field approximation
, we compute the position and total magnification of relativistic images as well .
+ * keywords * : black hole ; gravitational lensing ; null - geodesics ; quintessence ; relativistic images . .
And you have already written the first three sentences of the full article: gravitational lensing ( gl ) signifies the deflection of electromagnetic waves .
light propagates in empty space along a straight line .
the well - known theory of general relativity ( gr ) predicts that light will be bent if an object with a certain gravitational field is interposed in the light path . in literature.
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, gl has been used to study highly redshifted galaxies , quasars , supermassive black holes , exoplanets , dark matter candidates , primordial gravitational wave signatures , etc . , @xcite .
in @xmath1 , soldner was the first person who calculated the bending angle of light by using newtonian mechanics @xcite . in @xmath2 , einstein derived the same soldner s result by using the equivalence principle and minkowski metric , unaffected by gravity @xcite .
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Suppose that you have an abstract for a scientific paper: we discuss the conceptual differences between the broad histogram ( bhm ) and reweighting methods in general , and particularly the so - called multicanonical ( muca ) approaches .
the main difference is that bhm is based on microcanonical , fixed - energy averages which depends only on the good statistics taken * inside * each energy level .
the detailed distribution of visits among different energy levels , determined by the particular dynamic rule one adopts , is irrelevant .
contrary to muca , where the results are extracted from the dynamic rule itself , within bhm any microcanonical dynamics could be adopted . as a numerical test
, we have used both bhm and muca in order to obtain the spectral energy degeneracy of the ising model in @xmath0 and @xmath1 lattices , for which exact results are known .
we discuss why bhm gives more accurate results than muca , even using * the same * markovian sequence of states .
in addition , such advantage increases for larger systems . * key words * : monte carlo methods , ising model , computational physics .
And you have already written the first three sentences of the full article: development of tools for optimization of computer simulations is a field of great interest and activity .
cluster updating algorithms @xcite , probability reweighting procedures @xcite and , more recently , methods @xcite that obtain directly the spectral degeneracy @xmath2 are a few examples of very successful approaches ( for reviews of these methods see , for instance , @xcite and references therein ) .
the multicanonical ( muca ) and broad histogram ( bhm ) methods belong to the former category ..
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the entropic sampling method ( esm ) @xcite was proven to be an equivalent formulation of muca @xcite . from the knowledge of @xmath2 ,
these methods allow us to obtain any thermodynamical quantity of interest for the system under study , as the canonical average @xmath3 of some macroscopic quantity @xmath4 ( magnetization , density , correlations , etc ) .
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Suppose that you have an abstract for a scientific paper: we study off - resonant collective light scattering from ultracold atoms trapped in an optical lattice .
scattering from different atomic quantum states creates different quantum states of the scattered light , which can be distinguished by measurements of the spatial intensity distribution , quadrature variances , photon statistics , or spectral measurements .
in particular , angle - resolved intensity measurements reflect global statistics of atoms ( total number of radiating atoms ) as well as local statistical quantities ( single - site statistics even without an optical access to a single site ) and pair correlations between different sites . as a striking example we consider scattering from transversally illuminated atoms into an optical cavity mode . for the mott insulator state ,
similar to classical diffraction , the number of photons scattered into a cavity is zero due to destructive interference , while for the superfluid state it is nonzero and proportional to the number of atoms .
moreover , we demonstrate that light scattering into a standing - wave cavity has a nontrivial angle dependence , including the appearance of narrow features at angles , where classical diffraction predicts zero .
the measurement procedure corresponds to the quantum non - demolition ( qnd ) measurement of various atomic variables by observing light . .
And you have already written the first three sentences of the full article: ever since the first generation of bose - einstein condensates ( bec ) , it has been a central task to study quantum properties of such degenerate gases .
surprisingly , it turned out that many properties are well explained by the gross - pitaevskii equation , which is a an effective nonlinear single - particle equation and allows to calculate the evolution of the average atomic density and phase .
the density can be observed by simple absorption images after expansion , and the phase can be mapped onto density modulations in interferometric setups ..
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the limited validity of such mean - field descriptions became apparent with the advent of optical lattices @xcite , where one has quantum phase transitions between states of similar average density but radically different quantum fluctuations .
the majority of methods to characterize quantum properties of degenerate gases are based on matter - wave interference between atoms released from a trap in time - of - flight measurements @xcite , which destroys the system .
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Suppose that you have an abstract for a scientific paper: we study how the dynamics of a class of discrete dynamical system models for neuronal networks depends on the connectivity of the network . specifically
, we assume that the network is an erds - rnyi random graph and analytically derive scaling laws for the average lengths of the attractors and transients under certain restrictions on the intrinsic parameters of the neurons , that is , their refractory periods and firing thresholds .
in contrast to earlier results that were reported in @xcite , here we focus on the connection probabilities near the phase transition where the most complex dynamics is expected to occur . .
And you have already written the first three sentences of the full article: we study generic behavior of a class of discrete dynamic system models of neuronal networks . this class was designed to model the phenomenon of so - called _ dynamic clustering , _ where time appears to be partitioned into consecutive episodes during which certain groups of neurons fire together ,
while other neurons are quiescent and membership in the respective groups may change from episode to episode @xcite .
this phenomenon has been observed in a number of actual neuronal tissues @xcite . in.
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@xcite it was proved that dynamic clustering occurs in a broad class of ode models with a certain architecture , and that , moreover , discrete models as described here will reliably predict , for a large region of the state space of these ode models , which neurons fire during a given episode . in order to gain biological insights from this type of models , one needs to understand how the dynamics of the network depends on the network connectivity , which is modeled as a directed graph @xmath0 .
some provable restrictions on the possible network dynamics for certain classes of digraphs were derived in @xcite and section 6.4 of @xcite . for most neuronal networks in actual organisms
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Suppose that you have an abstract for a scientific paper: the recent detection of the shock precursors toward the very young l1448mm outflow offers the possibility to study the grain chemistry during the first stages of the shock evolution , constraining the molecules ejected from grains and the species formed in gas phase .
observations of key molecules in the grain chemistry like sio , ch@xmath0oh , so , cs , h@xmath1s , ocs , and so@xmath1 toward this outflow are presented .
the line profiles and the derived abundances show three distinct velocity regimes that trace the shock evolution : the preshock , the shock precursor and the postshock gas .
the sio , ch@xmath0oh , so , and cs abundances are enhanced with respect to the quiescent gas by one order of magnitude in the shock precursor component , and by three orders of magnitude in the postshock gas .
the derived sio and ch@xmath0oh abundances are consistent with the recent ejection of these molecules from grains . since h@xmath1s is only enhanced in the shock precursor component , and ocs and so@xmath1 are undetected , so and cs are the most abundant sulfur bearing species in the grain mantles of l1448mm .
the ejection of mainly so and cs rather than h@xmath1s or ocs from grains , suggests that the sulfur chemistry will depend on the chemical `` history '' of the grain mantles in outflows and hot cores . .
And you have already written the first three sentences of the full article: observational studies of the abundances of shock tracers like sio , ch@xmath0oh and the sulfur bearing molecules h@xmath1s , so , cs , ocs or so@xmath1 toward relatively evolved ( t@xmath210@xmath3@xmath4yr ) outflows and hot cores ( blake et al . 1987 ; bachiller & prez
gutirrez 1997 ; van der tak et al .
2003 ) , have established that these molecules are largely enhanced ( @xmath510@xmath6 ) due to the release of material from grains ..
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since silicon is heavily depleted onto grains ( ziurys , friberg , & irvine 1989 ; martn pintado , bachiller , & fuente 1992 ) and ch@xmath0oh has been firmly detected on icy mantles ( tielens & allamandola 1987 ) , sio and ch@xmath0oh are accepted to be ejected from grains . for the sulfur chemistry ,
since h@xmath1s is predicted to be efficiently formed on grain surfaces ( duley , millar , & williams 1980 ) , this molecule is assumed to initiate this chemistry ( charnley 1997 ) .
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Suppose that you have an abstract for a scientific paper: the interactions between an excitation ( similar to a pair of nambu monopoles connected by their associated string ) and a lattice defect are studied in an artificial two - dimensional square spin ice .
this is done by considering a square array of islands containing only one island different from all others .
this difference is incorporated in the magnetic moment ( spin ) of the imperfect " island and several cases are studied , including the special situation in which this distinct spin is zero ( vacancy ) .
we show that the two extreme points of a defective island behave like two opposite magnetic charges .
then , the effective interaction between a pair of nambu monopoles with the defective island is a problem involving four magnetic charges ( two pairs of opposite poles ) and a string .
we also sketch the configuration of the field lines of these four charges to confirm this picture .
the influence of the string on this interaction decays rapidly with the string distance from the defect . .
And you have already written the first three sentences of the full article: artificial spin ices @xcite are systems composed by an array of lithographically defined two - dimensional ( @xmath0 ) ferromagnetic nanostructures with single - domain islands ( elongated permalloy nanoparticles , in general ) , where the net magnetic moment of each island is assumed to be well approximated by an ising - like spin ( for a regime out of the ising behavior in a single elliptic island , see ref . ) .
they can be produced in diverse types of geometries with lattices like the square @xcite , brickwork @xcite , honeycomb or kagome @xcite , triangular @xcite etc .
recently , these artificial materials have been objects of intense experimental and theoretical investigations @xcite associated mainly with the appearance of collective excitations that are expected to behave like magnetic monopoles ..
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the theoretical and experimental studies concerning the physical properties of the ground state and excitations of the artificial square spin ices have deserved a great deal of attention in recent years @xcite . in this system , there are four ising spins at each vertex and they can be distributed in sixteen configurations grouped in four different topologies ( see fig . [
fig : squareice_topology ] ) .
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Suppose that you have an abstract for a scientific paper: * the first - passage time ( fpt ) , defined as the time a random walker takes to reach a target point in a confining domain , is a key quantity in the theory of stochastic processes@xcite .
its importance comes from its crucial role to quantify the efficiency of processes as varied as diffusion - limited reactions @xcite , target search processes @xcite or spreading of diseases @xcite .
most methods to determine the fpt properties in confined domains have been limited to markovian ( memoryless ) processes @xcite .
however , as soon as the random walker interacts with its environment , memory effects can not be neglected .
examples of non markovian dynamics include single - file diffusion in narrow channels@xcite or the motion of a tracer particle either attached to a polymeric chain@xcite or diffusing in simple @xcite or complex fluids such as nematics @xcite , dense soft colloids @xcite or viscoelastic solutions @xcite . here
, we introduce an analytical approach to calculate , in the limit of a large confining volume , the mean fpt of a gaussian non - markovian random walker to a target point .
the non - markovian features of the dynamics are encompassed by determining the statistical properties of the trajectory of the random walker in the future of the first - passage event , which are shown to govern the fpt kinetics .
this analysis is applicable to a broad range of stochastic processes , possibly correlated at long - times .
our theoretical predictions are confirmed by numerical simulations for several examples of non - markovian processes including the emblematic case of the fractional brownian motion in one or higher dimensions .
these results show , on the basis of gaussian processes , the importance of memory effects in first - passage statistics of non - markovian random walkers in confinement .
* it has long been recognized that the kinetics of reactions is influenced by the properties of the transport process that brings reactants into contact@xcite .
transport can even....
And you have already written the first three sentences of the full article: * mean first - passage time of a random walker in confinement*. * a * : what is the mean time @xmath52 needed for a random walker to reach a target in a confining volume ?
in this paper , we answer this question for random walkers with memory . *
b * : in one dimension , the problem is to quantify the first - passage time to a target in the presence of a reflecting boundary ..
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we show here that @xmath52 is controlled by the average trajectory @xmath53 followed by the walker in the future of its first passage to the target .
* mfpt of 1-dimensional non markovian random walks . *
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Suppose that you have an abstract for a scientific paper: we have performed a complete study of bps vortex solutions in the abelian sector of the standard model extension ( sme ) . specifically , we have coupled the sme electromagnetism with a higgs field which is supplemented with a lorentz - violating cpt - even term .
we have verified that lorentz violation ( lv ) belonging to the higgs sector allows to interpolate between some well known models like , maxwell - higgs , chern - simons - higgs and maxwell - chern - simons - higgs .
we can also observed that the electrical charged density distribution is nonnull in both cpt - even and cpt - odd models ; however , the total electric charge in the cpt - even case is null , whereas in the cpt - odd one it is proportional to the quantized magnetic flux .
the following general results can be established in relation to the lv introduced in the higgs sector : it changes the vortex ansatz and the gauge field boundary conditions .
a direct consequence is that the magnetic flux , besides being proportional to the winding number , also depends explicitly on the lorentz - violation belonging to the higgs sector . .
And you have already written the first three sentences of the full article: physics in the context of lorentz - violating theories have been an important branch for different theoretical and experimental research in recent years . the standard model extension ( sme )
@xcite is the general theoretical framework for studying lorentz violation ( lv ) effects , and it is build by adding lorentz - violating terms in all sectors of the minimal standard model .
particulary , the abelian gauge sector of the sme is the principal focus in searching for lv effects in physical systems jackiw-@xcite ..
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on the other hand , magnetic flux vortices have gained great interest since abrikosov s description for type - ii superconductors @xcite , which arise naturally from the non - relativistic limit of ginzburg - landau ( gl ) theory @xcite . in field theory ,
stable vortex configurations came up with the seminal work by nielsen and olesen @xcite whose study of the maxwell - higgs ( mh ) model shows that electrically neutral vortex solutions correspond to the ones obtained by abrikosov . lately , the existence of electrically charged vortex solutions in chern - simons - higgs ( csh ) cs , csv and maxwell - chern - simons - higgs ( mcsh ) @xcite models was verified .
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Suppose that you have an abstract for a scientific paper: edges of some quantum hall liquids and a number of other systems exhibit chiral transport : excitations can propagate in one direction only , e.g. , clockwise .
we derive a family of fluctuation - dissipation relations in non - equilibrium steady states of such chiral systems .
the theorems connect nonlinear response with fluctuations far from thermal equilibrium and hold only in case of chiral transport .
they can be used to test chiral or non - chiral character of the system .
reservoirs are connected to subsystem s by chiral edge channels @xmath0 .
the propagation direction along each edge channel is shown with an arrow .
each reservoir is at equilibrium with its own temperature and chemical potential .
panel ( b ) illustrates a quantum hall bar .
transport occurs along chiral edges and in quantum point contacts .
dotted lines show tunneling between edges in the point contacts.,width=288 ] according to the causality principle , past events influence the future but the future has no effect on the past .
this principle has no general counterpart in terms of the spatial separation of events : consequences of some events can be felt in every point after a sufficient wait time .
a spatial version of the causality principle emerges in low - energy effective theories of some many - body systems .
the best known example is the integer quantum hall effect ( qhe ) : low - energy excitations are confined to the edges and can propagate only clockwise or counterclockwise @xcite .
this can lead to a situation in which earlier events affect only those future events that occur `` downstream '' .
similar chiral transport is possible in a number of other systems : some fractional quantum hall liquids @xcite , interfaces of topological insulators , superconductors and ferromagnets @xcite , surface states in 3d qhe and so on .
the simplest example comes from the statistical mechanics models of traffic @xcite : chiral transport is possible on a network of one - way roads as long as no....
And you have already written the first three sentences of the full article: to make the paper self - contained we include a brief derivation of the fluctuation relation ( [ eq - fr ] ) [ eq .
( 3 ) of the main text ] .
additional details can be found in refs . [ 42,43 ] and references therein ..
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the main text defines forward and backward processes .
we want to connect the joint distribution functions @xmath37 $ ] of the energy and particle number changes in the reservoirs in the forward and backward processes .
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Suppose that you have an abstract for a scientific paper: a polynomial has _ saturated newton polytope _ ( snp ) if every lattice point of the convex hull of its exponent vectors corresponds to a monomial .
we compile instances of snp in algebraic combinatorics ( some with proofs , others conjecturally ) : skew schur polynomials ; symmetric polynomials associated to reduced words , redfield plya theory , witt vectors , and totally nonnegative matrices ; resultants ; discriminants ( up to quartics ) ; macdonald polynomials ; key polynomials ; demazure atoms ; schubert polynomials ; and grothendieck polynomials , among others .
our principal construction is the _
schubitope_. for any subset of @xmath0 ^ 2 $ ] , we describe it by linear inequalities .
this generalized permutahedron conjecturally has positive ehrhart polynomial .
we conjecture it describes the newton polytope of schubert and key polynomials .
we also define _ dominance order _ on permutations and study its poset - theoretic properties . .
And you have already written the first three sentences of the full article: the * newton polytope * of a polynomial @xmath1 $ ] is the convex hull of its exponent vectors , i.e. , @xmath2 @xmath3 has * saturated newton polytope * ( snp ) if @xmath4 whenever @xmath5 .
@xmath6 the determinant of a generic @xmath7 matrix .
the exponent vectors correspond to permutation matrices ..
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@xmath8 is the _ birkhoff polytope _ of @xmath7 doubly stochastic matrices .
snpness says there are no additional lattice points , which is obvious here .
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Suppose that you have an abstract for a scientific paper: we study the energetics , the electronic structure , and the ballistic transport of an infinite au monatomic chain with an adsorbed co molecule . we find that the bridge adsorption site is energetically favoured with respect to the atop site , both at the equilibrium au - au spacing of the chain and at larger spacings .
instead , a substitutional configuration requires a very elongated au - au bond , well above the rupture distance of the pristine au chain .
the electronic structure properties can be described by the blyholder model , which involves the formation of bonding / antibonding pairs of @xmath0 and @xmath1 states through the hybridization between molecular levels of co and metallic states of the chain . in the atop geometry , we find an almost vanishing conductance due to the @xmath0 antibonding states giving rise to a fano - like destructive interference close to the fermi energy . in the bridge geometry , instead
, the same states are shifted to higher energies and the conductance reduction with respect to pristine au chain is much smaller .
we also examine the effects of strain on the ballistic transport , finding opposite behaviors for the atop and bridge conductances .
only the bridge geometry shows a strain dependence compatible with the experimental conductance traces . .
And you have already written the first three sentences of the full article: au monatomic chains are produced in nanocontact experiments through different techniques,@xcite such as the scanning tunneling microscope,@xcite the high - resolution transmission electron microscope,@xcite and the mechanically controllable break - junction ( mcbj).@xcite it has been demonstrated that a single row of suspended au atoms between two electrical contacts typically displays a conductance of one quantum unit @xmath2 ( @xmath3 being the electron charge and @xmath4 planck s constant),@xcite which can be satisfactorily explained by a ballistic transport model based on the landauer - bttiker theory and a single , almost perfectly transmitted conductance channel ( as also confirmed by shot noise experiments , see ref . ) .
this conductance channel arises from the @xmath5-type valence electronic states of the au chain , which form a wide , spin - degenerate electronic band crossing the fermi level .
the reduced dimensionality of monatomic chains , and of atomic - sized contacts in general , favors the adsorption of _ impurities _ on the atoms forming the thinnest part of the contact because of their reduced coordination with respect to bulk or surface atoms.@xcite it is nowadays well understood that accidental or controlled contaminations with small impurities may change substantially the nanocontact conductance , because an adsorbed impurity can act as a source of electron scattering in the contact region . on the experimental side , a large number of cases have been already examined so far , such as @xmath6 on pt,@xcite au,@xcite and pd nanocontacts,@xcite but also on fe , co , and ni nanocontacts;@xcite co on pt,@xcite au , cu , and ni nanocontacts;@xcite @xmath7 on au and ag nanocontacts;@xcite and many others ..
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the effect of contamination is usually visible in the conductance histograms : the distribution of peaks often looks significantly altered after the admission of impurities in the proximity of the nanocontact.@xcite in some cases , the presence of adsorbed impurities changes the formation process and the structural properties of the chain : a remarkable example is the enhancement of monatomic chains formation for au nanocontacts in @xmath7-enriched atmosphere , which has been attributed to atomic oxygen embedded in the chains.@xcite several theoretical studies have been carried out in this field,@xcite but the understanding of the physical properties of monatomic chains in presence of impurities is far from complete . in this respect ,
an interesting case study is the adsorption of co on au monatomic chains .
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Suppose that you have an abstract for a scientific paper: as a follow - up to a recent study in the spin-@xmath0 case [ j. bunao and e. a. galapon , ann .
phys . * 353 * , 83 - 106 ( 2015 ) ] , we construct a one - particle time of arrival ( toa ) operator conjugate to a hamiltonian describing a free relativistic spin-@xmath1 particle in one spatial dimension . upon transformation in a representation where the hamiltonian is diagonal ,
it turns out that the constructed operator consists of an operator term @xmath2 whose action is the same as in the spin-@xmath0 case , and another operator term @xmath3 which commutes with the hamiltonian but breaks invariance under parity inversion .
if we must impose this symmetry on our toa operator , then we can throw away @xmath3 so that the toa operator is just @xmath2 . .
And you have already written the first three sentences of the full article: the marriage of relativity and quantum mechanics is a difficult one . even for the case of special relativity
, the interpretations can be somewhat troublesome . in the regime where the effects of quantum mechanics and special relativity are no longer negligible ,
the particle number in a system can , and will , fluctuate . roughly speaking ,.
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this is because mass is just another form of energy , according to special relativity , and energy can fluctuate , according to quantum mechanics .
thus , there can be massive particles being created and annihilated in a relativistic quantum system .
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Suppose that you have an abstract for a scientific paper: the low energy ( @xmath0 kev ) x - ray emission of the soft gamma - ray repeater has been studied by means of four xmm - newton observations carried out in the last two years , the latest performed in response to a strong sequence of hard x - ray bursts observed on 2004 october 5 .
the source was caught in different states of activity : over the 2003 - 2004 period the 2 - 10 kev flux doubled with respect to the historical level observed previously .
the long term raise in luminosity was accompanied by a gradual hardening of the spectrum , with the power law photon index decreasing from 2.2 to 1.5 , and by a growth of the bursting activity .
the pulse period measurements obtained in the four observations are consistent with an average spin - down rate of 5.5@xmath110@xmath2 s s@xmath3 , higher than the values observed in the previous years .
the long - term behavior of exhibits the correlation between spectral hardness and spin - down rate previously found only by comparing the properties of different sources ( both sgrs and anomalous x - ray pulsars ) .
the best quality spectrum ( obtained on 6 september 2004 ) can not be fitted by a single power law , but it requires an additional blackbody component ( kt@xmath4=0.79 kev , r@xmath4 = 1.9 ( d/15 kpc)@xmath5 km ) , similar to the spectra observed in other sgrs and in anomalous x - ray pulsars .
no spectral lines were found in the persistent emission , with equivalent width upper limits in the range 30 - 110 ev .
marginal evidence for an absorption feature at 4.2 kev is present in the cumulative spectrum of 69 bursts detected in september - october 2004 . .
And you have already written the first three sentences of the full article: the high - energy sources known as soft gamma - ray repeaters ( sgrs ) are probably one of the most intriguing manifestations of young neutron stars .
they were first discovered as transient phenomena through the observation of short ( @xmath6 1 s ) gamma - ray bursts .
the detection of several bursts coming from the same sky directions , coupled with their softer spectra , clearly set them apart from the standard gamma - ray bursts and led to the definition of this small class of sources ..
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only three confirmed sgrs are known in our galaxy and one in the large magellanic cloud ( see hurley 2000 for a review ) .
the nature of sgrs bursts remained a mystery for many years .
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Suppose that you have an abstract for a scientific paper: we study the influence of a fast noise on landau - zener transitions .
we demonstrate that a fast colored noise much weaker than the conventional white noise can produce transitions itself or can change substantially the landau - zener transition probabilities . in the limit of fast colored or strong white noise
we derive asymptotically exact formulae for transition probabilities and study the time evolution of a spin coupled to the noise and a sweeping magnetic field . .
And you have already written the first three sentences of the full article: landau - zener ( lz ) formula for transition probabilities at avoided crossing of two levels is one of a few fundamental results of non - stationary quantum mechanics .
its rather general character and simplicity makes it extremely suitable for versatile applications .
traditionally it was applied in quantum chemistry @xcite and in collision theory @xcite , @xcite ..
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a recent treatment of the experiments on the quantum molecular hysteresis in nanomagnets by wernsdorfer and sessoli was a real triumph of the lz theory .
a substantial contributions to the theory of spin tunnelling in these molecules was made by theorists .
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Suppose that you have an abstract for a scientific paper: we present a principal component analysis of galaxy spectra from the cnoc sample of rich x - ray luminous clusters at @xmath0 .
composite radial distributions of different stellar populations show strong gradients as a function of cluster - centric redshift .
the composite population is dominated by evolved populations in the core , and gradually changes to one which is similar to coeval field galaxies at radii greater than the virial radius .
we do not see evidence in the clusters for an excess of star formation over that seen in the coeval field . within this redshift range , significant evolution in the gradient shape
is seen , with higher redshift clusters showing steeper gradients .
this results in larger numbers of younger galaxies seen towards the inner regions of the clusters in effect , a restatement of the butcher - oemler effect .
luminosity density profiles are consistent with a scenario where this phenomenon is due to a decline over time in the infall rate of field galaxies into clusters . depending on how long galaxies reside in clusters before their star formation rates
are diminished , this suggests an epoch for maximal infall into clusters at @xmath1 .
we also discuss alternative scenarios for the evolution of cluster populations . .
And you have already written the first three sentences of the full article: the evolving populations in galaxy clusters offer a unique opportunity to observe galaxy evolution in action , and particularly the effects of environment on star forming galaxies .
present - day rich clusters have strikingly different populations from galaxies in poorer environments , suggesting that some mechanism is at work transforming normal field galaxies into the cluster population .
many recent investigations have focused on the details of how this tranformation occurs ( couch & sharples 1987 , barger et al . , 1996 , poggianti et al . , 1999 , balogh et al . , 1999 ) ..
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the emerging picture is that there may be a population of galaxies which were formed very early in the cluster s history , corresponding to the ellipticals often seen in cluster cores .
( e.g. bower et al . , 1992 ,
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Suppose that you have an abstract for a scientific paper: this paper is an extension of the work done by @xcite in which they have investigated the behaviour of a two - planet system embedded in a protoplanetary disc .
they have put a jupiter mass gas giant on the internal orbit and a lower mass planet on the external one .
we consider here a similar problem taking into account a gas giant with masses in the range of @xmath0 to @xmath1 and a super - earth ( i.e. a planet with mass @xmath2 ) as the outermost planet . by changing disc parameters and planet masses
we have succeeded in getting the convergent migration of the planets which allows for the possibility of their resonant locking .
however , in the case in which the gas giant has the mass of jupiter , before any mean motion first order commensurability could be achieved , the super - earth is caught in a trap when it is very close to the edge of the gap opened by the giant planet .
this confirms the result obtained by @xcite in their simulations .
additionally , we have found that , in a very thin disc , an apsidal resonance is observed in the system if the super - earth is captured in the trap .
moreover , the eccentricity of the small planet remains low , while the eccentricity of the gas giant increases slightly due to the imbalance between lindblad and corotational resonances .
we have also extended the work of @xcite by studying analogous systems in which the gas giant is allowed to take sub - jupiter masses . in this case , after performing an extensive survey over all possible parameters , we have succeeded in getting the 1:2 mean motion resonant configuration only in a disc with low aspect ratio and low surface density .
however , the resonance is maintained just for few thousand orbits .
thus , we conclude that for typical protoplanetary discs the mean motion commensurabilities are rare if the super - earth is located on the external orbit relative to the gas giant .
[ firstpage ] methods : numerical - planets and satellites : formation .
And you have already written the first three sentences of the full article: among over 300 extrasolar planets discovered so far only a few super - earths , that is planets with masses in the range of 2 - 10 @xmath3 , have been observed .
however , more candidates are just waiting to be confirmed and new discoveries are going to be announced , so we can soon find ourselves in the middle of the super - earth epoch .
some of such low - mass planets might exist in the neighborhood of gas giants and by means of numerical simulations it is possible to predict what are the most common configurations of extrasolar systems with super - earths and what will be detected by present and future observational programmes ..
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it is believed that the observed architecture of the planetary systems might be an outcome of the large scale orbital migration induced by the disc - planet interactions .
depending on the planet masses and on the disc properties , two main regimes of orbital migration can be distinguished @xcite .
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Suppose that you have an abstract for a scientific paper: we investigate by monte carlo simulations the critical properties of the three - dimensional bond - diluted ising model . the phase diagram is determined by locating the maxima of the magnetic susceptibility and
is compared to mean - field and effective - medium approximations .
the calculation of the size - dependent effective critical exponents shows the competition between the different fixed points of the model as a function of the bond dilution . , , and critical phenomena , ising model , disorder , monte carlo simulations 64.60.cn , 05.50.+q , 05.70.jk , 64.60.fr .
And you have already written the first three sentences of the full article: the qualitative influence of quenched disorder at second - order phase transitions is well understood since harris proposed a relevance criterion @xcite based on the knowledge of the specific heat critical exponent @xmath0 of the pure model : when @xmath0 is positive , the disordered system will reach a new fixed point with new critical exponents whereas if @xmath0 is negative , the same universality class will persist . as a paradigmatic model ,
the three - dimensional ( 3d ) disordered ising model characterized by @xmath1 has been extensively studied by : @xmath2 renormalization group methods in the weak quenched dilution regime .
the best estimates for the critical exponents obtained by this method are @xcite : @xmath3 @xmath4 @xmath5 ..
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@xmath2 monte carlo simulations of the site - diluted case for which the following exponents have been found @xcite : @xmath6 @xmath7 @xmath8 .
@xmath2 experimental investigations . for a review of these different results , see ref .
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Suppose that you have an abstract for a scientific paper: we empirically determine effective temperatures and bolometric luminosities for a large sample of nearby m dwarfs , for which high accuracy optical and infrared photometry is available .
we introduce a new technique which exploits the flux ratio in different bands as a proxy of both effective temperature and metallicity .
our temperature scale for late type dwarfs extends well below @xmath0 ( almost to the brown dwarf limit ) and is supported by interferometric angular diameter measurements above @xmath0 .
our metallicities are in excellent agreement ( usually within 0.2 dex ) with recent determinations via independent techniques .
a subsample of cool m dwarfs with metallicity estimates based on hotter _ hipparcos _ common proper motion companions indicates our metallicities are also reliable below @xmath0 , a temperature range unexplored until now .
the high quality of our data allow us to identify a striking feature in the bolometric luminosity versus temperature plane , around the transition from k to m dwarfs .
we have compared our sample of stars with theoretical models and conclude that this transition is due to an increase in the radii of the m dwarfs , a feature which is not reproduced by theoretical models . .
And you have already written the first three sentences of the full article: low mass dwarfs are the dominant stellar component of the galaxy and have been employed in a variety of galactic studies : tracing galactic disk kinematics ( e.g. hawley , gizis & reid 1996 ; gizis et al .
2002 ; bochanski et al . 2005 , 2007 ) , studying the stellar age velocity relations
( west et al . 2006 ) , investigating galactic structure ( e.g. reid et al ..
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1997 , kerber et al .
2001 , pirzkal et al .
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Suppose that you have an abstract for a scientific paper: we model for the first time the complete orbital evolution of a pair of supermassive black holes ( smbhs ) in a 1:10 galaxy merger of two disk dominated gas - rich galaxies , from the stage prior to the formation of the binary up to the onset of gravitational wave emission when the binary separation has shrunk to 1 milli parsec .
the high - resolution smoothed particle hydrodynamics ( sph ) simulations used for the first phase of the evolution include star formation , accretion onto the smbhs as well as feedback from supernovae explosions and radiative heating from the smbhs themselves . using the direct @xmath0-body code @xmath1-gpu
we evolve the system further without including the effect of gas , which has been mostly consumed by star formation in the meantime .
we start at the time when the separation between two smbhs is @xmath2 pc and the two black holes are still embedded in their galaxy cusps .
we use 3 million particles to study the formation and evolution of the smbh binary till it becomes hard . after a hard binary
is formed , we reduce ( reselect ) the particles to 1.15 million and follow the subsequent shrinking of the smbh binary due to 3-body encounters with the stars .
we find approximately constant hardening rates and that the smbh binary rapidly develops a high eccentricity .
similar hardening rates and eccentricity values are reported in earlier studies of smbh binary evolution in the merging of dissipationless spherical galaxy models .
the estimated coalescence time is @xmath3 gyr , significantly smaller than a hubble time .
we discuss why this timescale should be regarded as an upper limit .
since 1:10 mergers are among the most common interaction events for galaxies at all cosmic epochs , we argue that several smbh binaries should be detected with currently planned space - borne gravitational wave interferometers , whose sensitivity will be especially high for smbhs in the mass range considered here . .
And you have already written the first three sentences of the full article: central supermassive black holes ( smbhs ) are ubiquitous and are found in a variety of galaxies , ranging from low mass galaxies to the most massive early - type galaxies @xcite . within our current cosmological picture of hierarchical structure formation
, galaxies form through continuous mergers .
if both candidate galaxies harbor a central smbh before the merger , the evolution of the latter is thought to be as follows @xcite : the smbhs of the merging galaxies sink towards the center of the merger remnant due to dynamical friction and form a gravitationally bound binary system ..
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the further evolution of the smbh binary is governed by interactions with stars and gas .
if the binary semi - major axis value shrinks to a value where emission of gravitational waves ( gws ) efficiently takes away energy and angular momentum from the binary , the coalescence of smbhs becomes inevitable .
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Suppose that you have an abstract for a scientific paper: building on coprincipal mesoprimary decomposition [ kahle and miller , 2014 ] , we combinatorially construct an irreducible decomposition of any given binomial ideal . in a parallel manner , for congruences in commutative monoids
we construct decompositions that are direct combinatorial analogues of binomial irreducible decompositions , and for binomial ideals we construct decompositions into ideals that are as irreducible as possible while remaining binomial .
we provide an example of a binomial ideal that is not an intersection of binomial irreducible ideals , thus answering a question of eisenbud and sturmfels [ 1996 ] .
namedefsubjclassname@2010 mathematics subject classification .
And you have already written the first three sentences of the full article: an ideal in a commutative ring is irreducible if it is not expressible as an intersection of two ideals properly containing it .
irreducible ideals are primary , and any ideal @xmath0 in a noetherian ring is an intersection of irreducible ideals .
these _ irreducible decompositions _ are thus special cases of primary decomposition , but likewise are hard to compute in general ..
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if @xmath0 is a monomial ideal , however , this task is much easier : any monomial ideal is an intersection of irreducible ideals that are themselves monomial ideals ( see ( * ? ? ?
* theorem 5.27 ) for polynomial rings and ( * ? ? ?
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Suppose that you have an abstract for a scientific paper: for a real borel measurable function @xmath0 , which satisfies certain integrability conditions , it is possible to define a stochastic integral of the process @xmath1 with respect to a brownian motion @xmath2 , where @xmath3 is a diffusion driven by @xmath2 .
it is well know that the stochastic exponential of this stochastic integral is a local martingale .
in this paper we consider the case of an arbitrary borel measurable function @xmath0 where it may not be possible to define the stochastic integral of @xmath1 directly . however
the notion of the stochastic exponential can be generalized .
we define a non - negative process @xmath4 , called _ generalized stochastic exponential _ , which is not necessarily a local martingale .
our main result gives deterministic necessary and sufficient conditions for @xmath4 to be a local , true or uniformly integrable martingale . .
And you have already written the first three sentences of the full article: a _ stochastic exponential _ of @xmath5 is a process @xmath6 defined by @xmath7 for some continuous local martingale @xmath5 , where @xmath8 denotes a quadratic variation of @xmath5 .
it is well known that the process @xmath6 is also a continuous local martingale .
the characterisation of the martingale property of @xmath6 has been studied extensively in the literature because this question appears naturally in many situations . in the case of one dimensional processes ,.
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necessary and sufficient conditions for the process @xmath6 to be a martingale were recently studied by engelbert and senf in @xcite , blei and engelbert in @xcite and mijatovi and urusov in @xcite . in @xcite @xmath5 is a general continuous local martingale and the characterisation is given in terms of the dambis - dubins - schwartz time - change that turns @xmath5 into a brownian motion . in @xcite @xmath5 is a strong markov continuous local martingale and the condition is deterministic , expressed in terms of the speed measure of @xmath5 . in @xcite
the local martingale @xmath5 is of the form @xmath9 for some measurable function @xmath0 and a one - dimensional diffusion @xmath3 with drift @xmath10 and volatility @xmath11 driven by a brownian motion @xmath2 . in order to define the stochastic integral @xmath5 , an assumption that the function @xmath12 is locally integrable on the entire state space of the process @xmath3 is required . under this restriction
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Suppose that you have an abstract for a scientific paper: i review various phenomena associated with mass - accreting white dwarfs ( wds ) in relation to progenitors of type ia supernovae ( sne ia ) .
the wd mass can be estimated from light curve analysis in multiwavelength bands based on the optically thick wind theory . in the single degenerate scenario of sne ia ,
two main channels are known , i.e. , wd + main sequence ( ms ) channel and wd + red giant ( rg ) channel . in each channel , a typical binary undergoes three evolutional stages before explosion , i.e. , the wind phase , supersoft x - ray source ( sss ) phase , and recurrent nova phase in order of time because the accretion rate decreases with time as the companion mass decreases .
we can specify some accreting wds as the corresponding stage of evolution .
intermittent supersoft x - ray source like rxj0513.9@xmath06951 and v sge are corresponding to the wind phase objects . for the sss phase
cal 87-type objects correspond to the wd+ms channel . for the wd + rg channel , soft x - ray observations of early type galaxies
gave a statistical evidence of sss phase binaries .
recurrent novae of u sco - type and rs oph - type correspond to the wd + ms channel and wd + rg channel , respectively .
majority of recurrent novae host a very massive wd ( @xmath1 ) and often show a plateau phase in optical light curve correspondingly to the long lasted supersoft x - ray phase : these properties are indications of increasing wd masses . .
when the mass accretion rate decreases , to less than the value to keep steady hydrogen - burning ( @xmath2 ) , the binary enters the recurrent nova ( weak shell flashes ) phase .
the wd explodes at the star mark as an sn ia ( taken from ( * ? ? ?
* hachisu et al . 2010 ) ) . , width=240 ] and the initial wd mass of @xmath3 .
the initial system inside the region encircled by a thin solid line ( labeled `` initial '' ) increases its wd mass up to the critical mass ( @xmath4 ) for the sn ia explosion , the regions of which are encircled by a thick solid....
And you have already written the first three sentences of the full article: mass accreting white dwarfs ( wds ) become novae , persistent supersoft x - ray sources ( ssss ) , or wind evolution objects , depending on the mass - accretion rate .
very massive wds and its position in binary evolution are interesting subjects because they are closely related to type ia supernova ( sn ia ) progenitors . in this paper
i review how to specify the mass and its growth rate of wds and discuss them in relation to progenitors of sn ia ..
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section [ sec_evol ] introduces binary evolution scenarios to sne ia in which accreting wds are growing in mass ( single degenerate scenario ) .
for relatively low mass accretion rates ( @xmath5 yr@xmath6 ) , the wd experience recurrent nova outbursts .
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Suppose that you have an abstract for a scientific paper: we present an analysis of the x - ray properties of sources detected in the @xmath0xmm-_newton _ deep ( 200ks ) field . in order to constrain the absorbed agn population ,
we use extensive monte carlo simulations to directly compare the x - ray colours of observed sources with those predicted by several model distributions .
in particular , we have carried out our comparisons over the entire 0.210 kev energy range of the xmm-_newton _ cameras , making our analysis sensitive to a large range of absorbing column densities .
we have tested the simplest form of the unified scheme , whereby the intrinsic luminosity function of absorbed agn is set to be the same as that of their unabsorbed brethren , coupled with various model distributions of absorption .
of the tested distributions , the best fitting model has the fraction of agn with absorbing column @xmath1 , proportional to ( log@xmath1)@xmath2 .
we have also tested two extensions to the unified scheme : an evolving absorption scenario , in which the fraction of absorbed sources is larger at higher redshifts , and a luminosity dependent model in which high luminosity agn are less likely to be absorbed .
both of these models provide poorer matches to the observed x - ray colour distributions than the best fitting simple unified model .
we find that a luminosity dependent density evolution luminosity function reproduces poorly the 0.52 kev source counts seen in the @xmath0field .
field to field variations could be the cause of this disparity .
computing the x - ray colours with a simple absorbed power - law spectral model is found to over - predict , by a factor of two , the fraction of hard sources that are completely absorbed below 0.5 kev , implying that an additional source of soft - band flux must be present in a number of the absorbed sources .
the tested synthesis models predict that around 16% of the detections in the @xmath0field are due to agn at @xmath3 .
however , so far , only a single agn with @xmath4 has been identified in....
And you have already written the first three sentences of the full article: deep x - ray surveys have progressively resolved an increasing fraction of the soft x - ray background ( xrb ) , into faint point - like sources .
most recently , the ultra - deep _ chandra _ surveys ( @xcite , @xcite ) , have resolved over @xmath8 of the 0.52 kev xrb .
source counts have been measured in these fields to limiting fluxes of a few times @xmath9erg s@xmath10 @xmath11 , with corresponding sky densities of over @xmath12 sources deg@xmath13 , @xcite ..
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optical identification of faint x - ray sources reveals a heterogeneous mixture of objects , with the dominant class being active galactic nuclei ( agn ) , ( @xcite , @xcite ) .
these x - ray selected agn have a range of luminosities spanning several orders of magnitude , are found at redshifts up to 5 , and exhibit a wide range of observational properties .
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Suppose that you have an abstract for a scientific paper: imagej is a graphical user interface ( gui ) driven , public domain , java - based , software package for general image processing traditionally used mainly in life sciences fields .
the image processing capabilities of imagej are useful and extendable to other scientific fields . here
we present astroimagej ( aij ) , which provides an astronomy specific image display environment and tools for astronomy specific image calibration and data reduction .
although aij maintains the general purpose image processing capabilities of imagej , aij is streamlined for time - series differential photometry , light curve detrending and fitting , and light curve plotting , especially for applications requiring ultra - precise light curves ( e.g. , exoplanet transits ) .
aij reads and writes standard fits files , as well as other common image formats , provides fits header viewing and editing , and is world coordinate system ( wcs ) aware , including an automated interface to the astrometry.net web portal for plate solving images .
although aij provides research grade image calibration and analysis tools , its gui driven approach and cross - platform compatibility enable new users , even at the level of undergraduate student , high school student , or amateur astronomer , to quickly start processing , modeling , and plotting astronomical image data with one tightly integrated software package . .
And you have already written the first three sentences of the full article: in many areas of astronomy , there is a need for image processing and analysis capabilities and light curve extraction .
one such general purpose environment is iraf .
however , especially for ultra - precise photometry in fast - paced areas of research such as exoplanet transits and microlensing , there remains a need for a general , off - the - shelf integrated analysis environment that is at once sophisticated yet easy to use ..
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indeed , citizen science and professional - amateur collaborations increasingly require robust tools that can deliver research grade results while enabling broad usability . here
we present astroimagej ( aij ) , an astronomical image analysis software package that is based on imagej ( ij ; @xcite ) , but includes customizations to the base ij code and a packaged set of software plugins that provide an astronomy specific image display environment and tools for astronomy specific data reduction , analysis , modeling , and plotting .
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Suppose that you have an abstract for a scientific paper: we present a new method of extracting gravitational radiation from three - dimensional numerical relativity codes and providing outer boundary conditions .
our approach matches the solution of a cauchy evolution of einstein s equations to a set of one - dimensional linear wave equations on a curved background .
we illustrate the mathematical properties of our approach and discuss a numerical module we have constructed for this purpose .
this module implements the perturbative matching approach in connection with a generic three - dimensional numerical relativity simulation .
tests of its accuracy and second - order convergence are presented with analytic linear wave data . .
And you have already written the first three sentences of the full article: an important goal of numerical relativity is to compute the gravitational waveforms generated by systems of compact astrophysical objects such as binary black holes or binary neutron stars . with the prospect that gravitational wave detectors such as ligo , virgo and geo will be on - line in the next few years ,
it is crucial to study numerical relativistic simulations of events which might be observable by these detectors .
such calculations are important not only because they could provide signal templates which would considerably increase the probability of detection , but also because the comparison of such templates with the observations may provide essential astrophysical information on the nature of the emitting sources . the purpose of the binary black hole `` grand challenge '' _ alliance _.
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@xcite , a multi - institutional collaboration in the united states , is to study the inspiral coalescence of the most significant source of signals for the interferometric gravity wave detectors : a binary black hole system .
central to the goal of determining waveforms generated by astrophysical systems is the need for accurate techniques which compute asymptotic waveforms from numerical relativity simulations on three - dimensional ( 3d ) spacelike hypersurfaces with finite extents . in general ,
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Suppose that you have an abstract for a scientific paper: employing the maximum entropy method algorithm , we fit interstellar extinction measurements which span the wavelength range 0.125 - 3 .
we present a uniform set of mem model fits , all using the same grain materials , optical constants and abundance constraints .
in addition , we are taking advantage of improved uv and ir data and better estimates of the gas - to - dust ratio .
the model fits cover the entire range of extinction properties that have been seen in the galaxy and the magellanic clouds .
the grain models employed for this presentation are the simplistic homogeneous spheres models ( i.e. , mathis , rumpl , & nordsieck 1977 ) with two ( graphite , silicate ) or three ( graphite , silicate , amorphous carbon ) components .
though such usage is only a first step , the results do provide interesting insight into the use of grain size as a diagnostic of dust environment .
we find that the smc bar extinction curve can not be fit using carbon grains alone .
this is a challenge to the recent observational result indicating little silicon depletion in the smc . .
And you have already written the first three sentences of the full article: it was suspected as long as 150 years ago that something was blocking the light of stars on its way to earth , but it was nt until the early twentieth century that the work of barnard and trumpler confirmed the existence of obscuring clouds of interstellar dust ( whittet 1992 and references therein ) .
trumpler found that the wavelength dependence of interstellar extinction is proportional to @xmath0 implying submicron size dust grains . despite these early advances , we ,
in the early twenty - first century , are still struggling to understand the nature of cosmic dust ..
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the chemical composition of the dust grains has been the most difficult problem to address since the available observational data do not provide strong constraints .
many solids have been suggested including ices , silicates , various carbon compounds , metals and complex organic molecules .
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Suppose that you have an abstract for a scientific paper: we are able to detect clear signatures of dephasing a distinct trait of many - body localisation ( mbl ) via the dynamics of two - sites entanglement , quantified through the concurrence . using the protocol implemented in [ science * 349 * , 842 ( 2015 ) ]
we show that in the mbl phase the average two - site entanglement decays in time as a power law , while in the anderson localised phase it tends to a plateau .
the exponent of the power law is not universal and shows a clear dependence on the strength of the interaction .
this behaviour is also qualitatively different in the ergodic phase where the two - site entanglement decays exponentially .
all the results are obtained by means of time - dependent density matrix renormalisation group simulations ; they are corroborated by analytical calculations on an effective model .
two - site entanglement has been already measured in cold atoms : our analysis paves the way for the first direct experimental test of many - body dephasing in the mbl phase . .
And you have already written the first three sentences of the full article: the phenomenon of many - body localisation @xcite ( mbl ) refers to the breakdown of ergodicity in generic , disordered many - body systems due to quantum effects .
this is a striking counterexample to the fundamental assumptions of statistical mechanics about the thermalization of an isolated system . for any non - integrable , classical many - body hamiltonian system ,
the dynamics is ergodic in phase space leading eventually to thermalization . in classical mechanics.
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this occurs even for systems close to integrability via arnold diffusion , a phenomenon strictly related to the celebrated kam theorem @xcite . in quantum systems
there is a striking exception : destructive interference between matter waves forbids a system in the mbl phase to thermalize .
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Suppose that you have an abstract for a scientific paper: in this paper we study a filtered @xmath0-theoretical " analog of a graded algebra associated to any loopless graph @xmath1 which was introduced in @xcite .
we show that two such filtered algebras are isomorphic if and only if their graphs are isomorphic .
we also study a large family of filtered generalizations of the latter graded algebra which includes the above
@xmath0-theoretical " analog . .
And you have already written the first three sentences of the full article: the following square - free algebra @xmath2 associated to an arbitrary vertex labeled graph @xmath1 was defined in @xcite , see also @xcite .
let @xmath1 be a graph without loops on the vertex set @xmath3 ( below we always assume that all graphs might have multiple edges , but no loops ) . throughout the whole paper ,
we fix a field @xmath4 of zero characteristic ..
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let @xmath5 be the graded commutative algebra over @xmath4 generated by the variables @xmath6 , with the defining relations : @xmath7 let @xmath2 be the subalgebra of @xmath5 generated by the elements @xmath8 for @xmath9 where @xmath10 for the reasons which will be clear soon , we call @xmath2 the _ spanning forests counting algebra _ of @xmath1 .
its hilbert series and the set of defining relations were calculated in @xcite following the initial paper @xcite .
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Suppose that you have an abstract for a scientific paper: we present observations of quiet - sun small - scale structures ( sss ) in the microwave range with the _ radio astronomical telescope of the academy of sciences 600 _ ( ratan-600 ) spectral - polarization facility in a wide range of frequencies .
sss are regularly recorded in routine observations of the large reflector - type radio telescope and represent manifestations in the radio range of various structures of the quiet - sun : supergranulation network , bright points , plage patches and so on . a comparison with with images from the _ solar dynamics observatory _
( sdo ) showed that the microwave emission comes from a region extending from the chromosphere to the low transition region .
we measured the properties of the sss as well as the degree of circular polarization averaged over the beam of the radio telescope and from this we estimated the magnetic field at the formation level of the radiation . .
And you have already written the first three sentences of the full article: the microwave range is rich in information on quiet - sun structures in the upper chromosphere , the transition region and the low corona ( see , for a recent review ) .
the variation of the brightness temperature with frequency provides valuable data for modeling , while the circular polarization gives estimates of the magnetic field . due to the limited spatial resolution
, useful information can only be obtained with large radio telescopes or interferometers ..
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the chromospheric network was first detected in interferometric data (; ; ) .
the first , one - dimensional , imaging observations came from the _ radio astronomical telescope of the academy of sciences _ 600 ( ratan-600 ) in the wavelength range of 24 cm , which showed small - scale brightness fluctuations across the quiet - sun (; ; ) ; this phenomenon was called _ solar radiogranulation_. thanks to the high spatial resolution ( 9 by 50 ) at the wavelength of 1.35 cm , it was possible to identify the individual elements of the radiogranulation with bright and dark elements of the chromospheric network visible in the caii k line @xcite . in the millimeter range , small - scale structures ( sss )
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Suppose that you have an abstract for a scientific paper: the dynamics of cosmological models with isotropic matter sources ( perfect fluids ) is extensively studied in the literature ; in comparison , the dynamics of cosmological models with anisotropic matter sources is not . in this paper
we consider spatially homogeneous locally rotationally symmetric solutions of the einstein equations with a large class of anisotropic matter models including collisionless matter ( vlasov ) , elastic matter , and magnetic fields .
the dynamics of models of bianchi types i , ii , and ix are completely described ; the two most striking results are the following : ( i ) there exist matter models , compatible with the standard energy conditions , such that solutions of bianchi type ix ( closed cosmologies ) need not necessarily recollapse ; there is an open set of forever expanding solutions .
( ii ) generic type ix solutions associated with a matter model like vlasov matter exhibit oscillatory behavior toward the initial singularity .
this behavior differs significantly from that of vacuum / perfect fluid cosmologies ; hence `` matter matters '' .
finally , we indicate that our methods can probably be extended to treat a number of open problems , in particular , the dynamics of bianchi type viii and kantowski - sachs solutions . .
And you have already written the first three sentences of the full article: spatially homogeneous ( sh ) cosmologies are one of the main cornerstones of general relativity . on the one hand
, they provide a rich supply of case studies for the effects that solutions of the einstein equations of general relativity can ( and will ) produce ; in particular , the behavior of sh cosmologies gives the necessary input to model the behavior of our actual universe . on the other hand , there are convincing arguments that the dynamics of generic solutions of the einstein equations close to spacelike singularities are built on the dynamics of sh cosmological models @xcite .
an sh cosmological model is a solution of the einstein equations that is independent of the spatial variables in a suitable frame ( see sec ..
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[ sh ] for a precise definition ) .
therefore , for these models , the einstein equations reduce to an autonomous system of non - linear ordinary differential equations . as first recognized by collins @xcite , provided the system possesses the appropriate regularity , the equations can be analyzed using the potent methods of dynamical systems theory . since then , our knowledge of the ( qualitative ) dynamics of sh cosmological models has increased substantially , see @xcite for reviews . until recent years , the analysis of sh cosmologies has been largely restricted to isotropic matter sources like perfect fluids ( including dust ) and scalar fields .
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Suppose that you have an abstract for a scientific paper: this paper is a further extension of the method proposed in @xcite as applied to another set of jump - diffusion models : inverse normal gaussian , hyperbolic and meixner . to solve the corresponding pides we accomplish few steps .
first , a second - order operator splitting on financial processes ( diffusion and jumps ) is applied to these pides . to solve the diffusion equation
, we use standard finite - difference methods . for the jump part
, we transform the jump integral into a pseudo - differential operator and construct its second order approximation on a grid which supersets the grid that we used for the diffusion part .
the proposed schemes are unconditionally stable in time and preserve positivity of the solution which is computed either via a matrix exponential , or via pde approximation of the matrix exponent .
various numerical experiments are provided to justify these results . .
And you have already written the first three sentences of the full article: this paper is a further extension of the method proposed in @xcite as applied to another set of jump - diffusion models : inverse normal gaussian , hyperbolic and meixner .
these models have been introduced in mathematical finance within last two decades , see @xcite . however , to the best of author s knowledge it seems they received less attention of practitioners as compared , e.g. , with merton , kou and cgmy / kobol models , see @xcite for a short survey of the latter models and references therein . at the first glance this looks unfair , because typical distributions of returns produced by the former models fit the observed market data ( and , in particular , fat tails and skew ) even better than their more popular counterparts .
one of the possible reasons could be that despite the pdf and the characteristic function ( cf ) of these models are known in closed form , and , therefore , pricing of plain vanilla and even american options could be done transform methods ( fft , cosine , adaptive integration in the fourier space ) , see @xcite , the analytic expressions for the pdf and cf are more complicated than that for their counterparts , and sometimes require usage of special functions ..
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however , the latter does nt prevent pricing and hedging of simple vanilla instruments to be efficiently done .
the second point is that the considered models are pure jump models that do nt contain a diffusion component .
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Suppose that you have an abstract for a scientific paper: using the classical field method , we study numerically the characteristics and decay of the turbulent tangle of superfluid vortices which is created in the evolution of a bose gas from highly nonequilibrium initial conditions . by analysing the vortex line density , the energy spectrum and the velocity correlation function ,
we determine that the turbulence resulting from this effective thermal quench lacks the coherent structures and the kolmogorov scaling ; these properties are typical of both ordinary classical fluids and of superfluid helium when driven by grids or propellers .
instead , thermal quench turbulence has properties akin to a random flow , more similar to another turbulent regime called ultra - quantum turbulence which has been observed in superfluid helium . .
And you have already written the first three sentences of the full article: the formation of a coherent bose - einstein condensate from a thermal bose gas is a rich topic of ongoing research @xcite .
recent experiments on thermally - quenched bose gases have observed the spontaneous formation of defects in the guise of vortices @xcite and solitonic vortices @xcite , confirming the occurrence of the kibble - zurek mechanism @xcite in these gases .
a paradigm for this non - equilibrium phase transition is the formation of a homogeneous weakly - interacting bose gas starting from highly non - equilibrium initial conditions @xcite ..
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the gas is modelled as a classical matter field described by the gross - pitaevskii equation .
this field undergoes a universal self - ordering into a quasi - condensate , i.e. a coherent superfluid component , and a non - condensed , thermal component .
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Suppose that you have an abstract for a scientific paper: we propose a new smoothing method for obtaining surface densities from discrete particle positions from numerical simulations .
this is an essential step for many applications in gravitational lensing .
this method is based on the `` scatter '' interpretation of the discrete density field in the smoothed particle hydrodynamics .
we use monte carlo simulations of uniform density fields and one isothermal ellipsoid to empirically derive the noise properties , and best smoothing parameters ( such as the number of nearest neighbors used ) . a cluster from high - resolution simulations is then used to assess the reality of high - order singularities such as swallowtails and butterflies in caustics , which are important for the interpretation of substructures in gravitational lenses .
we also compare our method with the delaunay tesselation field estimator using the galaxy studied by bradac et al .
( 2004 ) , and find good agreements .
we show that higher order singularities are not only connected with bound subhaloes but also with the satellite streams
. however , the presence of high - order singularities are sensitive to not only the fluctuation amplitude of the surface density , but also the detailed form of the underlying smooth lensing potential ( such as ellipticity and external shear ) . .
And you have already written the first three sentences of the full article: gravitational lensing provides an important technique to study the matter distribution in the universe ( e.g. , kochanek , schneider & wambsganss 2004 ) . on galaxy - scales ,
simple smooth isothermal models appear to match the gravitational lenses reasonably well ( e.g. , kochanek 1991 ) , although there are some difficulties in accurately reproducing the observed flux ratios . at present , it is unclear what causes these `` anomalous flux ratios '' ( e.g. , kochanek & dalal 2005 ; mao et al .
2004 ; macci et al ..
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2006 ; macci & miranda 2006 ) . on cluster scales , it became clear early on that smooth spherical models under - predict the number of giant arcs by orders of magnitude ( e.g. , bartelmann & weiss 1994 ; bartelmann et al . 1995 ; bartelmann et al .
ellipticity and substructures in clusters have dramatic effects on the lensing cross - sections of giant arcs .
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Suppose that you have an abstract for a scientific paper: we studied magnetic - field induced microwave absorption in 100 - 200 nm thick la@xmath0sr@xmath1mno@xmath2 films on srtio@xmath2 substrate and found a low - field absorption with a very peculiar angular dependence : it appears only in the oblique field and is absent both in the parallel and in the perpendicular orientations .
we demonstrate that this low - field absorption results from the ferromagnetic resonance in the multidomain state ( domain - mode resonance ) .
its unusual angular dependence arises from the interplay between the parallel component of the magnetic field that drives the film into multidomain state and the perpendicular field component that controls the domain width through its effect on domain wall energy .
the low - field microwave absorption in the multidomain state can be a tool to probe domain structure in magnetic films with in - plane magnetization . .
And you have already written the first three sentences of the full article: low - field microwave absorption is a useful tool of detection of magnetic transitions in bulk materials and thin films @xcite .
it is also known as nonresonant , zero - field , or magnetically - modulated microwave absorption and it was used to find the traces of ferromagnetic and superconducting phases in bulk materials @xcite .
the low - field absorption in magnetic materials has multiple sources that operate in different frequency ranges @xcite ..
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the dominant contribution at radiofrequencies arises from magnetoimpedance @xcite ( the field dependence of the skin - depth ) and domain wall resonances @xcite , while at microwave frequencies it is commonly attributed to various ferromagnetic resonances in the magnetically unsaturated state .
these include non - aligned fmr mode @xcite , the natural fmr @xcite , off - resonant absorption associated with the fmr tail @xcite , and the domain mode resonances @xcite .
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Suppose that you have an abstract for a scientific paper: we consider a prototypical dynamical lattice model , namely the discrete nonlinear schrdinger equation on non - square lattice geometries .
we present a systematic classification of the solutions that arise in principal six - lattice - site and three - lattice - site contours in the form of both discrete multi - pole solitons and discrete vortices . additionally to identifying the possible states , we analytically track their linear stability both qualitatively and quantitatively .
we find that among the six - site configurations , the `` hexapole '' of alternating phases ( @xmath0-@xmath1 ) , as well as the vortex of topological charge @xmath2 have intervals of stability ; among three - site states , only the vortex of topological charge @xmath3 may be stable in the case of focusing nonlinearity .
these conclusions are confirmed both for hexagonal and for honeycomb lattices by means of detailed numerical bifurcation analysis of the stationary states from the anti - continuum limit , and by direct simulations to monitor the dynamical instabilities , when the latter arise .
the dynamics reveal a wealth of nonlinear behavior resulting not only in single site solitary waveforms , but also in robust multi - site breathing structures . .
And you have already written the first three sentences of the full article: hamiltonian lattice or quasi - discrete systems have become popular in the last few years , to a considerable extent due to experimental implementations of such systems drawn from various branches of physics .
one of the first examples where such developments became relevant was in the nonlinear optics of fabricated algaas waveguide arrays @xcite . there , the interplay of inherent discreteness and nonlinearity led to the emergence of numerous interesting phenomena including peierls - nabarro potential barriers , diffraction and diffraction management @xcite , gap solitons @xcite , and so on ( see also the reviews @xcite and references therein ) . on the other hand , more recently another area of nonlinear optics that has been central to the development of both theoretical as well as of computational tools to study such systems ,
has been the setting of optically induced photonic lattices in photorefractive crystals such as sbn . there.
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, the original theoretical proposal of these lattices @xcite was susbequently followed by experimental realizations @xcite , paving the way for the observation of a diverse array of novel and interesting phenomena in such crystals .
these include the formation of patterns such as dipole @xcite , quadrupole @xcite and necklace @xcite solitons , impurity modes @xcite , discrete vortices @xcite , rotary solitons @xcite , higher order bloch modes @xcite and gap vortices @xcite , the observation of two - dimensional ( 2d ) bloch oscillations and landau - zener tunneling @xcite , the observation of localization and diffraction in honeycomb @xcite , hexagonal @xcite and quasi - crystalline lattices @xcite , and most recently the study of anderson localization in disordered photonic lattices @xcite ( for a review of some of this activity see , e.g. , refs .
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Suppose that you have an abstract for a scientific paper: the dynamical friction force experienced by a massive gravitating body moving through a gaseous medium is modified by sufficiently strong large - scale magnetic fields . using linear perturbation theory
, we calculate the structure of the wake generated by , and the gravitational drag force on , a body traveling in a straight - line trajectory in a uniformly magnetized medium .
the functional form of the drag force as a function of the mach number ( @xmath0 , where @xmath1 is the velocity of the body and @xmath2 the sound speed ) depends on the strength of the magnetic field and on the angle between the velocity of the perturber and the direction of the magnetic field .
in particular , the peak value of the drag force is not near mach number @xmath3 for a perturber moving in a sufficiently magnetized medium . as a rule of thumb
, we may state that for supersonic motion , magnetic fields act to suppress dynamical friction ; for subsonic motion , magnetic fields tend to enhance dynamical friction . for perturbers moving along the magnetic field lines ,
the drag force at some subsonic mach numbers may be stronger than it is at supersonic velocities .
we also mention the relevance of our findings to black hole coalescence in galactic nuclei . .
And you have already written the first three sentences of the full article: an object moving in a background medium induces a gravitational wake .
the asymmetry of the mass density distribution upstream and downstream from the perturber produces a drag on the body , which is often referred to as gravitational drag or dynamical friction ( df ) force .
a body in orbital motion may undergo a radial decay of its orbit due to the loss of angular momentum by the negative torque caused by df drag ..
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chandrasekhar ( 1943 ) derived the dynamical friction on a massive particle passing through a homogeneous and isotropic background of light stars .
his formula is applied to estimate the merger timescale of satellite systems or to study the accretion history of galaxies .
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Suppose that you have an abstract for a scientific paper: we present a power spectrum analysis of the final 2df qso redshift survey catalogue containing 22652 qsos . utilising the huge volume probed by the qsos
, we can accurately measure power out to scales of @xmath0mpc and derive new constraints , at @xmath1 , on the matter and baryonic contents of the universe .
importantly , these new cosmological constraints are derived at an intermediate epoch between the cmb observations at @xmath2 , and local ( @xmath3 ) studies of large - scale structure ; the average qso redshift corresponds to a look - back time of approximately two - thirds of the age of the universe .
we find that the amplitude of clustering of the qsos at @xmath1 is similar to that of present day galaxies .
the power spectra of the qsos at high and low redshift are compared and we find little evidence for any evolution in the amplitude . assuming a @xmath4 cosmology to derive the comoving distances , @xmath5 , to the qsos , the power spectrum derived can be well described by a model with shape parameter @xmath6 .
if an einstein - de sitter model @xmath5 is instead assumed , a slightly higher value of @xmath7 is obtained . a comparison with the _ hubble volume _
@xmath4cdm simulation shows very good agreement over the whole range of scales considered .
a standard ( @xmath8 ) cdm model , however , predicts a much higher value of @xmath9 than is observed , and it is difficult to reconcile such a model with these data .
we fit cdm model power spectra ( assuming scale - invariant initial fluctuations ) , convolved with the survey window function , and corrected for redshift space distortions , and find that models with baryon oscillations are slightly preferred , with the baryon fraction @xmath10 .
the overall shape of the power spectrum provides a strong constraint on @xmath11 ( where @xmath12 is the hubble parameter ) , with @xmath13 .
cosmology : observations , large - scale structure of universe , quasars : general , surveys - quasars .
And you have already written the first three sentences of the full article: the large - scale structure of the universe represents one of the most powerful discriminants between cosmological models .
qsos are highly effective probes of the structure of the universe over a wide range of scales and can trace clustering evolution over a look - back time which is 70 - 80 per cent of its present age . in the linear regime ( @xmath14h@xmath15mpc )
, they are clearly superior to galaxies as probes of large scale structure by virtue of both the large volumes they sample and their flat @xmath16 distribution . accurately measuring the clustering over these scales bridges the gap between the clustering results on relatively small scales from galaxy redshift surveys out to scales previously only probed by microwave background anisotropy experiments ..
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the power spectrum perhaps provides the most natural description of the matter fluctuations that comprise large - scale structure ; for a gaussian field , the amplitude of the fourier modes provide a statistically complete description of the density perturbations .
one potential problem of using qsos as probes of large scale structure is that they , like galaxies , are biased tracers of the mass density field .
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Suppose that you have an abstract for a scientific paper: we calculate the next - to - leading order perturbative qcd corrections to the transverse momentum weighted single transverse spin asymmetry in drell - yan lepton pair production in hadronic collisions .
we identify the splitting function relevant for the scale evolution of the twist - three quark - gluon correlation function .
we comment on the consequences of our results for phenomenology . .
And you have already written the first three sentences of the full article: single transverse spin asymmetries ( ssas ) in high energy hadronic reactions continue to attract much theoretical and experimental interest .
they are defined as differences of cross sections when one of the initial hadrons transverse spin is flipped , divided by the sum : @xmath0 .
the theoretical description of ssas has proven to be a challenge @xcite , since the leading collinear partonic contribution to the asymmetries vanishes @xcite . over the past few years.
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, there have been a number of theoretical developments that have led to much progress in the exploration of the underlying physics for single spin asymmetry phenomena .
these developments mainly follow two lines : the so - called transverse momentum dependent ( tmd ) approach @xcite , which uses parton distributions and/or fragmentation functions that depend on partonic transverse momentum , and the twist - three quark - gluon correlation function approach . more recently
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Suppose that you have an abstract for a scientific paper: we present results concerning resolvent estimates for the linear operator associated with the system of differential equations governing 2 dimensional perturbations of plane couette flow .
we prove estimates on the @xmath0 norm of the resolvent of this operator showing this norm to be proportional to the reynolds number @xmath1 for a region of the unstable half plane . for the remaining region , we show that the problem can be reduced to estimating the solution of a homogeneous ordinary differential equation with non - homogeneous boundary conditions .
numerical approximations indicate that norm of the resolvent is proportional to @xmath1 in the whole region of interest .
[ theorem]lemma @=11 addtoresetequationsection .
And you have already written the first three sentences of the full article: we consider the initial boundary value problem @xmath2 where @xmath3 \times [ 0 , \infty ) \longrightarrow \mathbb{r}^2 $ ] is the unknown function @xmath4 .
@xmath5 is the vector field @xmath6 and the reynolds number @xmath1 is a positive parameter .
the forcing @xmath7 is a given @xmath8 function satisfying satisfying @xmath9 and @xmath10 for all @xmath11 \times [ 0 , \infty)$ ] ..
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these equations are the linearization of the equations governing 2 dimensional perturbations @xmath12 of @xmath6 , known as couette flow , which is a steady solution of @xmath13 the pressure term @xmath14 in ( [ eq1.1 ] ) is determined in terms of @xmath15 by the linear elliptic equation @xmath16 we note that @xmath17 depends linearly on @xmath15 , and is determined up to a constant .
the estimates derived in this paper are independent of @xmath17 . with @xmath17 given by the above equation ,
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Suppose that you have an abstract for a scientific paper: a controlled - phase gate was demonstrated in superconducting xmon transmon qubits with fidelity reaching 99.4% , relying on the adiabatic interaction between the @xmath0 and @xmath1 states .
here we explain the theoretical concepts behind this protocol that achieves fast gate times with only @xmath2 control of the hamiltonian , based on a theory of non - linear mapping of state errors to a power spectral density and use of optimal window functions . with a solution given in the fourier basis , optimization is shown to be straightforward for practical cases of an arbitrary state change and finite bandwidth of control signals .
we find that errors below @xmath3 are readily achievable for realistic control waveforms . .
And you have already written the first three sentences of the full article: high fidelity controlled - phase ( cz ) gates were recently demonstrated for adjacent qubits in a 5-qubit quantum processor @xcite .
for a two - qubit gate , cz fidelity as high as 99.4% was obtained using the phase shift from near crossing of the @xmath0 and @xmath1 states , similar to previous work on superconducting qubits @xcite , but following a new `` fast adiabatic '' protocol that gives both fast gate times and low error rates . here
we explain the theoretical concepts behind this protocol , showing how waveforms may be generated and parameterized in a manner that is readily optimized , both numerically and experimentally ..
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the general problem of achieving fast adiabatic performance is of great interest to the physics community @xcite , with applications in coherent manipulation , precision measurements , and quantum computing .
finding an improved control methodology therefore has potential for applications in a variety of quantum systems .
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Suppose that you have an abstract for a scientific paper: we present new imaging measurements of 27 individual globular clusters in the halo of the nearby elliptical galaxy ngc 5128 , obtained with the _ hubble space telescope _ stis and wfpc2 cameras .
we use the cluster light profiles to determine their structural parameters ( core and half - light radii , central concentration , and ellipticity ) . combining these with similar data for selected inner - halo clusters from holland et al .
1999 ( aap , 348 , 418 ) , we now have a total sample of 43 ngc 5128 globular clusters with measured structural properties .
we find that classic king - model profiles match the clusters extremely well , and that their various structural parameters ( core- and half - light radius , central surface brightness , central concentration ) fall in very much the same range as do the clusters in the milky way and m31 .
we find half a dozen bright clusters which show tentative evidence for `` extra - tidal light '' that extends beyond the nominal tidal radius , similar in nature to several such objects previously found in the milky way and m31 ; these may represent clusters being tidally stripped , or possibly ones in which anisotropic velocity distributions are important .
we also confirm previous indications that ngc 5128 contains relatively more clusters with large ( @xmath0 ) ellipticity than does the milky way .
instead , the @xmath1distribution of the ngc 5128 clusters strongly resembles that of the old clusters in the lmc and also in m31 .
finally , calculations of the cluster binding energies @xmath2 as defined by mclaughlin 2000 ( apj , 539,618 ) show that the ngc 5128 clusters occupy the same extremely narrow region of the parametric `` fundamental plane '' as do their milky way counterparts .
our data are thus strongly consistent with the claim that the globular clusters in both ngc 5128 and the milky way are fundamentally the same type of object : old star clusters with similar mass - to - light ratios and king - model structures . .
And you have already written the first three sentences of the full article: globular star clusters have remarkably simple structures that are well approximated by isotropic , single - mass @xcite models . in the multi - dimensional space of all their structural quantities such as scale radii , central concentration , surface brightness , velocity dispersion , mass - to - light ratio , and so forth , it is striking that real globular clusters in the milky way inhabit only a narrow region referred to as the fundamental plane ( fp ; see * ? ? ?
recently , @xcite has shown that a particularly simple way of expressing the fp is to note that any king model is completely specified by four input parameters such as total cluster luminosity @xmath3 , central concentration @xmath4 log @xmath5 , mass - to - light ratio , and binding energy @xmath2 .
adding in the two strong empirical constraints that @xmath6 const and @xmath7 then requires the clusters to lie on a two - dimensional slice of this 4-space , leaving only two quantities ( @xmath8 and @xmath3 ) to determine the residual scatter on this fp . in turn , the concentration @xmath8 is correlated with @xmath3 , leaving the remarkable result that the structures of these clusters are fixed largely by just one major _ internal _ parameter , their total mass ( or luminosity , at a given age ) ..
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the _ external _ environment , i.e. its location in the galactic tidal field , also has some influence on the fp parameters .
however , clusters may have formed under drastically different environmental conditions in other galactic environments ( giant and dwarf ellipticals , starburst systems , galactic bulges and rings , etc . ) .
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Suppose that you have an abstract for a scientific paper: extreme mass ratio inspirals ( emris ) are one of the main gravitational wave ( gw ) sources for a future space detector , such as elisa / ngo , and third generation ground - based detectors , like the einstein telescope .
these systems present an interest both in astrophysics and fundamental physics . in order to make a high precision determination of their physical parameters
, we need very accurate theoretical waveform models or templates . in the case of a circular equatorial
orbit , the key stumbling block to the creation of these templates is the flux function of the gw .
this function can be modeled either via very expensive numerical simulations , which then make the templates unusable for gw astronomy , or via some analytic approximation method such as a post - newtonian approximation .
this approximation is known to be asymptotically divergent and is only known up to 5.5pn order for the schwarzschild case and to 4pn order for the kerr case . a way to improve
the convergence of the flux is to use re - summation methods . in this work
we extend previous results using the pad and chebyshev approximations , first by taking into account the absorption of the gws by the central black hole which was neglected in previous studies , and secondly by using the information from the schwarzschild and absorption terms to create a kerr flux up to 5.5pn order .
we found that these two additions both improve the convergence .
we also demonstrate that the best re - summation method for improving the flux model is based on a flux function which we call the inverted chebyshev approximation " . .
And you have already written the first three sentences of the full article: the extreme mass ratio inspirals ( emris ) are one of the most important sources of gravitational waves ( gws ) for future space detectors such as the elisa / ngo mission @xcite , and terrestrial detectors like the einstein telescope @xcite .
these systems are composed of a stellar mass compact object orbiting around a ( super)massive black hole ( bh ) such that the mass ratio is on the order of @xmath0 .
their physical interest comes from the fact that the small object normally traces out approximately @xmath1 orbits from when it is first observed in the detector until it plunges into the central bh ..
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the test particle can then be thought of as something which maps the spacetime around the central bh , providing a very strong test of the theory of general relativity
. even if emris are quite simple objects , their dynamics , which we need to understand for gw astrophysics , are very complicated . as we do not have a solution for the case of generic orbits around the central bh , we concentrate on a test particle in a circular equatorial orbit . due to the fact that there is no plane precession in this case
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Suppose that you have an abstract for a scientific paper: a fully parallel version of the contact dynamics ( cd ) method is presented in this paper . for large enough systems ,
@xmath0 efficiency has been demonstrated for up to @xmath1 processors using a hierarchical domain decomposition with dynamic load balancing .
the iterative scheme to calculate the contact forces is left domain - wise sequential , with data exchange after each iteration step , which ensures its stability .
the number of additional iterations required for convergence by the partially parallel updates at the domain boundaries becomes negligible with increasing number of particles , which allows for an effective parallelization .
compared to the sequential implementation , we found no influence of the parallelization on simulation results .
contact dynamics method , granular materials , hierarchical domain decomposition , load balancing , mpi library 45.70.-n , 02.70.-c , 45.10.-b .
And you have already written the first three sentences of the full article: _ discrete element method _ simulations have been widely employed in scientific studies and industrial applications to understand the behavior of complex many - particle systems such as granular materials .
the common property of these methods is that the time evolution of the system is treated on the level of individual particles , i.e. the trajectory of each particle is calculated by integrating its equations of motion . among the discrete element methods , _ soft particle molecular dynamics _
( md ) @xcite , _ event driven _.
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( ed ) @xcite and _ contact dynamics _ ( cd ) @xcite are often used for simulating granular media .
_ molecular dynamics _ is the most widely used algorithm for discrete element simulations . for granular materials ,
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Suppose that you have an abstract for a scientific paper: we discuss the emergence of scalar gravitational waves in metric - affine @xmath0-gravity .
such a component allows to discriminate between metric and metric
affine theories the intrinsic meaning of this result is that the geodesic structure of the theory can be discriminated .
we extend the formalism of cross correlation analysis , including the additional polarization mode , and calculate the detectable energy density of the spectrum for cosmological relic gravitons .
the possible detection of the signal is discussed against sensitivities of virgo , ligo and lisa interferometers . .
And you have already written the first three sentences of the full article: extending general relativity ( gr ) to more general actions with respect to the hilbert - einstein one is revealing a very fruitful approach in modern physics . from a conceptual point of view
, there is no _ a priori _ reason to restrict the gravitational lagrangian to a linear function of the ricci scalar @xmath1 , minimally coupled with matter .
the idea that there are no `` exact '' laws of physics but that the lagrangians of physical interactions are `` stochastic '' functions with the property that local gauge invariances ( i.e. conservation laws ) are well approximated in the low energy limit and that physical constants can vary has been recently taken into serious consideration . beside fundamental physics motivations ,.
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all these theories have acquired a huge interest in cosmology due to the fact that they naturally `` exhibit inflationary behaviors able to overcome the shortcomings of cosmological standard model .
furthermore , dark energy models mainly rely on the implicit assumption that einstein s gr is the correct theory of gravity , indeed .
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Suppose that you have an abstract for a scientific paper: we derive microscopically the dynamics associated with the d.c . josephson effect in a superconducting tunnel junction interacting with an arbitrary electromagnetic environment . to do so , we extend to superconducting junctions the so - called @xmath0 theory ( see e.g. ingold and nazarov , http://arxiv.org/abs/cond-mat/0508728[arxiv:cond-mat/0508728 ] ) that accurately describes the interaction of a nonsuperconducting tunnel junction with its environment .
we show the dynamics of this system is described by a small set of coupled correlation functions that take into account both cooper pair and quasiparticle tunneling . when the phase fluctuations are small the problem is fully solved self - consistently , using and providing the exact linear admittance @xmath1 of the interacting junction .
fifty years ago josephson stunned the community when he published @xcite the equations that govern the behavior of superconducting tunnel junctions .
these josephson relations , as they became known , link the voltage @xmath2 and the superconducting phase difference @xmath3 across the junction , and the current @xmath4 through it : @xmath5 if @xmath3 is static , @xmath6 , and a nondissipative current @xmath4 flows through the junction , bounded by @xmath7 .
this maximum supercurrent @xmath8 ( or the corresponding josephson coupling energy @xmath9 ) was originally predicted to be an intrinsic property of the tunnel junction , depending only on its resistance in the normal state and the superconducting gap of its electrodes @xcite , but not on other details such as the junction s geometry , or its fabrication process . along the years , josephson junctions ( jjs )
have proved invaluable electronic components forming exquisitely sensitive sensors ( e.g. , squid magnetometers , quantum - limited amplifiers ) , metrological volt standard devices , or quantum bits and gates .
it is important to note that the first josephson relation was derived assuming that the phase @xmath3 has negligible quantum....
And you have already written the first three sentences of the full article: here we evaluate the linear response of the junction to a vanishingly small ac excitation @xmath119 added to the static phase difference @xmath3 of the junction .
this can be done exactly , even in presence of the environment @xcite . at the lowest order in the tunneling hamiltonian and in the excitation ,
the time evolution of the current flowing through the junction under this perturbation is given by @xmath120 \rangle\\ & = & \frac{i}{\hbar } \int_{- \infty}^{t } { \mathrm{d}}s \left\langle \left [ \hat{i } ( t ) + \delta \varphi ( t ) \frac{\partial \hat{i}}{\partial \varphi } ( t ) , h_{t } ( s ) + \delta \varphi ( s ) \frac{\partial h_{t}}{\partial \varphi } ( s ) \right ] \right\rangle\\ & = & \langle \hat{i } \rangle + \frac{i}{\hbar } \delta \varphi ( t ) \int_{- \infty}^{t } { \mathrm{d}}s \left\langle \left [ \frac{\partial \hat{i}}{\partial \varphi } ( t - s ) , h_{t } \right ] \right\rangle + \frac{i}{\hbar } \int_{- \infty}^{t } { \mathrm{d}}s \left\langle \left [ \hat{i } ( t - s ) , \frac{\partial h_{t}}{\partial \varphi } \right ] \right\rangle \delta \varphi ( s ) \end{aligned}\ ] ] where , as in the body of the article , the angular brackets denote averaging over unperturbed states of the electrode and the environment and the time evolution of operators is the unperturbed one ..
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@xmath121 is the dc supercurrent in absence of the ac excitation . using the identities : @xmath122 @xmath123 and denoting @xmath124 , and @xmath125 the odd part of @xmath126 we get @xmath127 going to the frequency domain @xmath128
finally we obtain the junction s admittance as @xmath129 this expression is a generalized fluctuation - dissipation relation @xcite . note that the integral contains contributions from both cooper pair and quasiparticle tunneling .
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Suppose that you have an abstract for a scientific paper: noise filtering is an essential part for measurement of quantum phenomena at extremely low temperatures . here , we present the design of a filter which can be installed in space constrained cryogenic environment containing a large number of signal carrying lines .
our filters have a -3db point of 65khz and its performance at ghz frequencies are comparable to the best available rf filters . .
And you have already written the first three sentences of the full article: with the advancement of science , low noise measurements at low temperatures are becoming increasingly important .
experiments probing quantum mechanical phenomena require high degree of immunity from stray noise present in our surroundings . though it is relatively easy to reach temperatures as low as 10mk in commercial dilution refrigerators , achieving similar electronic temperatures on the other hand is far from being trivial .
this is due to the fact that the microscopic system to be studied is connected to measurement instruments at room temperature ..
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the electromagnetic noise coming from the room temperature environment perturbs the system through propagation through the measurement lines . to eliminate such disturbance , effective cryogenic filters are necessary for each measurement line . in the literature
there are various types of filters which have been developed , for example thin film filters @xcite , distributed thin - film microwave filters @xcite , thermocoax@xmath0 ( flers , france ) filters @xcite to name a few .
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Suppose that you have an abstract for a scientific paper: we obtain the exact nontopological soliton lattice solutions of the associated lam equation in different parameter regimes and compute the corresponding energy for each of these solutions .
we show that in specific limits these solutions give rise to nontopological ( pulse - like ) single solitons , as well as to different types of topological ( kink - like ) single soliton solutions of the associated lam equation . following manton
, we also compute , as an illustration , the asymptotic interaction energy between these soliton solutions in one particular case . finally , in specific limits
, we deduce the soliton lattices , as well as the topological single soliton solutions of the lam equation , and also the sine - gordon soliton solution . .
And you have already written the first three sentences of the full article: over the years , extensive research has been carried out seeking the exact soliton solutions of both periodic ( e.g. , sine - gordon , double sine - gordon ) and nonperiodic ( e.g. , @xmath0 , @xmath1 ) field theory models .
for example , the exactly solvable sine - gordon ( sg ) equation @xcite and its quasi - exactly solvable ( qes ) partner , i.e. , the double sine - gordon equation ( dsg ) , have exact single soliton @xcite as well as soliton lattice @xcite solutions .
there have been some advances in the study of the _ hyperbolic _ analogues of these problems ; the exactly solvable hyperbolic analogue of the sg equation is the sine - hyperbolic gordon ( shg ) equation @xcite ..
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this potential has only one minimum and thus does not support ( topological ) soliton solutions .
the hyperbolic analogue of the dsg equation is the double sine - hyperbolic gordon ( dshg ) equation , which is a qes double - well potential with exact single soliton and soliton lattice solutions @xcite . however , not much is known regarding the _ elliptic _ analogues of these problems . the elliptic ` generalization ' of the sg is the lam equation @xcite but ,
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Suppose that you have an abstract for a scientific paper: we describe a future possible upgrade of the european xfel consisting in the construction of an undulator beamline dedicated to life science experiments .
the availability of free undulator tunnels at the european xfel facility offers a unique opportunity to build a beamline optimized for coherent diffraction imaging of complex molecules , like proteins and other biologically interesting structures .
crucial parameters for such bio - imaging beamline are photon energy range , peak power , and pulse duration .
key component of the setup is the undulator source .
the peak power is maximized in the photon energy range between @xmath0 kev and @xmath1 kev by the use of a very efficient combination of self - seeding , fresh bunch and tapered undulator techniques .
the unique combination of ultra - high peak power of @xmath2 tw in the entire energy range , and ultrashort pulse duration tunable from @xmath3 fs to @xmath4 fs , would allow for single shot coherent imaging of protein molecules with size larger than @xmath4 nm . also , the new beamline would enable imaging of large biological structures in the water window , between @xmath5 kev and @xmath6 kev . in order to make use of standardized components , at present we favor the use of sase3-type undulator segments .
the number segments , @xmath7 , is determined by the tapered length for the design output power of @xmath2 tw .
the present plan assumes the use of a nominal electron bunch with charge of @xmath8 nc .
experiments will be performed without interference with the other three undulator beamlines .
therefore , the total amount of scheduled beam time per year is expected to be up to @xmath9 hours .
* deutsches elektronen - synchrotron * * + * desy 12 - 082 may 2012 @xmath10 @xmath11 * conceptual design of an undulator system for a dedicated bio - imaging beamline at the european x - ray fel * @xmath12 gianluca geloni , _ + european xfel gmbh , hamburg _ vitali kocharyan and evgeni saldin _ + deutsches....
And you have already written the first three sentences of the full article: structural biology aims at the understanding of the biological function of proteins by studying their three - dimensional structure .
the major method for determining such macromolecular three - dimensional structure is x - ray crystallography @xcite .
requirements on the crystal samples set limits to structural studies of biological systems with atomic resolution . in fact , many molecules fail to form crystals ..
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the development of xfels promises to open up new areas in life science by allowing structure determination without the need for crystallization .
in fact , as suggested in @xcite , sufficiently short and intense pulses from x - ray lasers may allow for the imaging of single protein molecules .
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Suppose that you have an abstract for a scientific paper: for stationary kpz growth in @xmath0 dimensions the height fluctuations are governed by the baik - rains distribution . using the totally asymmetric single step growth model , alias tasep
, we investigate height fluctuations for a general class of spatially homogeneous random initial conditions .
we prove that for tasep there is a one - parameter family of limit distributions , labeled by the roughness of the initial conditions .
the distributions are defined through a variational formula .
we use monte carlo simulations to obtain their numerical plots .
also discussed is the connection to the six - vertex model at is conical point . .
And you have already written the first three sentences of the full article: for stochastic growth models in the kardar - parisi - zhang ( kpz ) universality class over a one - dimensional substrate the height fluctuations `` always '' broaden as @xmath1 .
on the other hand the full probability density function depends on the choice of the initial data .
as well known , for a flat initial surface , @xmath2 , the large @xmath3 fluctuations of @xmath4 are distributed according to goe tracy - widom distribution @xcite ..
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in contrast , if the height profile is macroscopically curved , then goe has to be replaced by gue @xcite .
such dependence is not so easily inferred directly from the growth dynamics .
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Suppose that you have an abstract for a scientific paper: we have used recent very long baseline interferometry ( vlbi ) observations by with a resolution of @xmath0 mas to investigate the properties of faint sources selected from the tenth cambridge ( 10c ) survey in the lockman hole .
the 10c survey is complete to 0.5 mjy at 15.7 ghz and has a resolution of 30 arcsec .
we have previously shown that this population is dominated by flat - spectrum sources below @xmath1 mjy , in disagreement with several models of the faint , high - frequency sky .
we find that 33 out of the 51 10c sources in the vlbi field ( 65 percent ) are detected by the vlbi observations .
the sources detected by the vlbi observations must have a high brightness temperature , thus ruling out the possibility that this faint , high frequency population is dominated by starbursting or starforming sources and indicating that they must be active galactic nuclei .
galaxies : active radio continuum : galaxies .
And you have already written the first three sentences of the full article: in @xcite ( 2013 ; hereafter paper i ) we studied a sample of 296 faint ( @xmath2 mjy ) sources selected from the tenth cambridge survey ( 10c ; @xcite ) at 15.7 ghz in the lockman hole .
the 10c survey was made with the arcminute microkelvin imager ( ami ; @xcite ) and covers ten fields complete to 0.5 mjy , two of which are in the lockman hole . by matching the 10c catalogue to several lower - frequency surveys we investigated the radio spectral properties of the sources in this sample .
we found a significant change in spectral index @xmath3 with flux density @xmath4 ( where @xmath5 for frequency @xmath6 ) the median spectral index between 15.7 ghz and 610 mhz changes from @xmath7 for 15.7-ghz flux densities @xmath8 to @xmath9 for lower flux densities ( @xmath10 ) ( full details of this study are given in paper i ) ..
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this suggests that a population of faint , flat - spectrum sources is emerging at flux densities @xmath11 . the properties of the 10c sample were compared with those of a sample of sources selected from the skads simulated sky ( s@xmath12 ; @xcite ) ( full details are in paper i ) .
we found that this simulation fails to reproduce the observed spectral index distribution and underpredicts the number of sources in the faintest flux density bin ( @xmath13 ) .
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Suppose that you have an abstract for a scientific paper: in this review i will describe progress that has been made in determining masses of galaxy clusters using ` weak lensing ' and how this technique my be applied in the future to determine the dark matter distribution both on supercluster scales and on the scale of galaxy haloes . .
And you have already written the first three sentences of the full article: masses of galaxy clusters have traditionally been obtained either from measurements of the velocity dispersion of the galaxies or from the temperature of the x - ray emitting gas , and have given a great deal of input to cosmology : these results have shown that the total cluster mass greatly exceeds the mass in galaxies and ( for any reasonable hubble constant ) the mass in x - ray emitting gas , and thus suggest the existence of non - baryonic dark matter .
they have been used to estimate the density parameter under the assumption that the mass - to - light ratio of clusters is equal to that of the universe as a whole , and , more recently , under the assumption that the baryonic - to - total mass ratio is representative of the universal value .
they have also been used to try to estimate the cluster mass function , which potentially has much power to constrain theories for structure formation ..
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while vital for cosmology , these mass estimates are subject to a number of systematic uncertainties arising from the assumptions that go into the modelling , and which are rather hard to quantify . for the virial analysis , one must make assumptions about the anisotropy of the orbits , one typically assumes that light traces the mass ; that the cluster is spherical , and one assumes that the cluster is dynamically relaxed .
similar assumptions go into the x - ray analysis , yet it is not entirely clear to what extent these assumptions are valid , or what effect departures from sphericity etc .
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Suppose that you have an abstract for a scientific paper: we have undertaken the study of the elemental abundances and kinematic properties of a metal - poor sample of candidate thick - disk stars selected from the rave spectroscopic survey of bright stars to differentiate among the present scenarios of the formation of the thick disk . in this paper
, we report on a sample of 214 red giant branch , 31 red clump / horizontal branch , and 74 main - sequence / sub - giant branch metal - poor stars , which serves to augment our previous sample of only giant stars .
we find that the thick disk @xmath0 ratios are enhanced , and have little variation ( @xmath1 dex ) , in agreement with our previous study .
the augmented sample further allows , for the first time , investigation of the gradients in the metal - poor thick disk . for stars with @xmath2 ,
the thick disk shows very small gradients , @xmath3 , in @xmath4-enhancement , while we find a @xmath5 radial gradient and a @xmath6 vertical gradient in iron abundance .
in addition , we show that the peak of the distribution of orbital eccentricities for our sample agrees better with models in which the stars that comprise the thick disk were formed primarily in the galaxy , with direct accretion of stars contributing little .
our results thus disfavor direct accretion of stars from dwarf galaxies into the thick disk as a major contributor to the thick disk population , but can not discriminate between alternative models for the thick disk , such as those that invoke high - redshift ( gas - rich ) mergers , heating of a pre - existing thin stellar disk by a minor merger , or efficient radial migration of stars . .
And you have already written the first three sentences of the full article: since its identification @xcite , the thick disk has been shown to have distinct kinematics ( e.g. * ? ? ?
* ; * ? ? ?
* ; * ? ? ?.
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* ) and a distinct metallicity distribution ( e.g. * ? ? ?
* ; * ? ? ?
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Suppose that you have an abstract for a scientific paper: we derive the multi - fractal scaling of probability distributions of multi - particle configurations for the binary reaction - diffusion system @xmath0 in @xmath1 and for the ternary system @xmath2 in @xmath3 . for the binary reaction
we find that the probability @xmath4 of finding @xmath5 particles in a fixed volume element @xmath6 at time @xmath7 decays in the limit of large time as @xmath8 for @xmath9 and @xmath10 for @xmath11 . here
@xmath12 .
for the ternary reaction in one dimension we find that @xmath13 .
the principal tool of our study is the dynamical renormalization group .
we compare predictions of @xmath14-expansions for @xmath15 for binary reaction in one dimension against exact known results .
we conclude that the @xmath14-corrections of order two and higher are absent in the above answer for @xmath4 for @xmath16 .
furthermore we conjecture the absence of @xmath17-corrections for all values of @xmath5 . .
And you have already written the first three sentences of the full article: modeling chemical reactions is an important practical and theoretical problem
. systems of reacting particles are typical of complex irreversible non - equilibrium systems
. the popular description of these systems in terms of simple rate equations currently adopted in chemical kinetics @xcite does not appear to have a firm theoretic foundation and often produces wrong results ..
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interacting particle systems provide a good model for simple chemical reactions .
well - known examples include systems of diffusing - coalescing and diffusing - annihilating particles describing reactions @xmath18 and @xmath0 respectively .
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Suppose that you have an abstract for a scientific paper: we investigate the impact of dust - induced gas fragmentation on the formation of the first low - mass , metal - poor stars ( @xmath0 ) in the early universe .
previous work has shown the existence of a critical dust - to - gas ratio , below which dust thermal cooling can not cause gas fragmentation .
assuming the first dust is silicon - based , we compute critical dust - to - gas ratios and associated critical silicon abundances ( @xmath1}_{\text{crit}}$ ] ) . at the density and temperature associated with protostellar disks , we find that a standard milky way grain size distribution gives @xmath1}_{\text{crit } } = -4.5 \pm 0.1 $ ] , while smaller grain sizes created in a supernova reverse shock give @xmath1}_{\text{crit } } = -5.3 \pm 0.1 $ ] .
other environments are not dense enough to be influenced by dust cooling .
we test the silicate dust cooling theory by comparing to silicon abundances observed in the most iron - poor stars ( @xmath2}<-4.0 $ ] ) .
several stars have silicon abundances low enough to rule out dust - induced gas fragmentation with a standard grain size distribution .
moreover , two of these stars have such low silicon abundances that even dust with a shocked grain size distribution can not explain their formation . adding small amounts of carbon dust
does not significantly change these conclusions .
additionally , we find that these stars exhibit either high carbon with low silicon abundances or the reverse .
a silicate dust scenario thus suggests that the earliest low - mass star formation in the most metal - poor regime may have proceeded through two distinct cooling pathways : fine structure line cooling and dust cooling .
this naturally explains both the carbon - rich and carbon - normal stars at extremely low [ fe / h ] . .
And you have already written the first three sentences of the full article: the formation of the first stars marks the beginnings of structure formation , cosmic reionization , and chemical enrichment ( e.g. , @xcite and references within ) .
these so - called population iii stars formed out of metal - free primordial gas at the centers of dark matter minihalos @xcite . due to relatively weak feedback and inefficient cooling , they had high characteristic masses of order at least tens of solar masses and therefore short life spans ( e.g. , @xcite ) .
although the short lives of population iii stars implies that they can not be directly observed anymore , it is believed that the metals released in their supernovae trigger a transition from predominantly high mass star formation to a low mass mode @xcite ..
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the chemical abundances of low - mass , metal - poor population ii stars in the milky way stellar halo have been interpreted as traces of the population iii star era ( e.g. , @xcite , @xcite ) .
if this is indeed the case , then an understanding of the formation process for population ii stars is one way to probe the epoch of the first stars @xcite .
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Suppose that you have an abstract for a scientific paper: the binding energy of a negatively charged hydrogenic impurity with on- and off - center position in a spherical gaussian quantum dot was calculated with the configuraction interaction method .
our calculations show that @xmath0 is always positive for on - center impurities with a maximum near to the radius for one - electron stability of the potential well @xmath1 . for off - center positions the binding energy can assume negative values within a range of the quantum dot radius , thus indicating the instability of the system donor binding energy , quantum dot , off - center impurity 71.55.-i , 73.21.la .
And you have already written the first three sentences of the full article: doping of semiconductor crystallites of nanometer size , or quantum dots ( qds ) , allows tuning the transport , electric , optical and magnetic properties for the purpose of tailoring proposed quantum devices @xcite .
incorporation of impurities into qds provides charge carriers that strongly modifies those properties @xcite .
neutral and negatively charged shallow donor impurities ( @xmath2 and @xmath3 centers ) in semiconductors are the analogue of the h atom and the h@xmath4 ion in atomic physics , _.
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i.e. _ , one and two electrons bonded to a positively charged coulomb center , respectively . in particular , @xmath3 centers are the simplest system where correlation effects can play a role . the binding energy of a @xmath2 center in qds has been studied with different confining potential shapes and calculation methods @xcite .
many of them assume the impurity to be at the center of the qd .
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Suppose that you have an abstract for a scientific paper: we explore the effects of element diffusion due to gravitational settling and thermal and chemical diffusion on the pulsational properties of da white dwarfs . to this end
, we employ an updated evolutionary code coupled with a pulsational , finite difference code for computing the linear , non - radial g - modes in the adiabatic approximation .
we follow the evolution of a 0.55 white dwarf model in a self - consistent way with the evolution of chemical abundance distribution as given by time dependent diffusion processes .
results are compared with the standard treatment of diffusive equilibrium in the trace element approximation .
appreciable differences are found between the two employed treatments .
we conclude that time dependent element diffusion plays an important role in determining the whole oscillation pattern and the temporal derivative of the periods in dav white dwarfs .
in addition , we discuss the plausibility of the standard description employed in accounting for diffusion in most of white dwarf asteroseismological studies . _
lsun@xmath0 _ msun@xmath1 _
mstar@xmath2 # 1#1 [ firstpage ] stars : evolution - stars : interiors - stars : white dwarfs - stars : oscillations .
And you have already written the first three sentences of the full article: asteroseismology is a method to extract information about the internal structure and evolution of stars by means of the study of their oscillatory pattern .
this technique , very sophisticated in the case of the sun , has also undergone a strong development in other stars , in particular the pulsating white dwarfs ( wds ) ( for reviews , see , e.g. , brown & gilliland 1994 ; gautschy & saio 1995 ; 1996 ) .
pulsating wds show multi - periodic luminosity variations in three ranges of effective temperatures ( ) corresponding to the currently called dov , dbv and dav ( see , e.g. , the reviews by winget 1988 and kepler & bradley 1995 ) . of interest for this work.
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are the davs ( hydrogen - dominated atmospheres ) , or zz ceti , that pulsate in the instability strip corresponding to 12500 k @xmath3 10700 k. the periodicities in the light curves of pulsating wds are naturally explained in terms of non - radial g - modes of low harmonic degree ( @xmath4 ) , driven by the `` @xmath5 mechanism '' working in a partial ionization region near the stellar surface ( dolez & vauclair 1981 , winget et al . 1982 ) .
other physically plausible mechanism for overstability of g - modes in zz ceti stars is the `` convective driving mechanism '' ( see brickhill 1991 and goldreich & wu 1999 for details ) .
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Suppose that you have an abstract for a scientific paper: we conduct an investigation into the dispersive post - shock oscillations in the entropic lattice - boltzmann method ( elbm ) . to this end
we use a root finding algorithm to implement the elbm which displays fast cubic convergence and guaranties the proper sign of dissipation .
the resulting simulation on the one - dimensional shock tube shows no benefit in terms of regularization from using the elbm over the standard lbgk method .
we also conduct an experiment investigating of the lbgk method using median filtering at a single point per time step . here
we observe that significant regularization can be achieved .
* keywords * : fluid dynamics , lattice boltzmann , entropy balance , dispersive oscillations , numerical test , shock tube * ams subject classifications . *
65n12 , 76m28 , 74q10 , 74j40 .
And you have already written the first three sentences of the full article: the lattice boltzmann methods in their original form ( see @xcite ) do not guarantee the proper entropy production and may violate the second law .
the proper entropy balance remains up to now a challenging problem for many lattice boltzmann models @xcite . the entropic lattice boltzmann method ( elbm )
was invented first in 1998 as a tool for construction of single relaxation time lattice boltzman models which respect the @xmath0-theorem @xcite ..
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for this purpose , instead of the mirror image with local equilibrium as reflection center , the entropic involution was proposed , which preserves the entropy value .
later , we call it the karlin - succi involution @xcite . in 2000
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Suppose that you have an abstract for a scientific paper: the atlas experiment will undergo a major upgrade of the tracker system in view of the high luminosity phase of the lhc ( hl - lhc ) foreseen to start around 2025 .
thin planar pixel modules are promising candidates to instrument the new pixel system , thanks to the reduced contribution to the material budget and their high charge collection efficiency after irradiation . new designs of the pixel cells , with an optimized biasing structure , have been implemented in n - in - p planar pixel productions with sensor thicknesses of m. using beam tests , the gain in hit efficiency is investigated as a function of the received irradiation fluence .
the outlook for future thin planar pixel sensor productions will be discussed , with a focus on thin sensors with a thickness of 100 and m and a novel design with the optimized biasing structure and small pixel cells ( 50x50 and 25x100 ) .
these dimensions are foreseen for the new atlas read - out chip in 65 nm cmos technology and the fine segmentation will represent a challenge for the tracking in the forward region of the pixel system at hl - lhc . to predict the performance of 50x50 pixels at high @xmath0 ,
fe - i4 compatible planar pixel sensors have been studied before and after irradiation in beam tests at high incidence angle with respect to the short pixel direction .
results on cluster shapes , charge collection- and hit efficiency will be shown .
= 1 pixel detectors , planar sensors , atlas , hl - lhc .
And you have already written the first three sentences of the full article: one of the main challenges for the innermost tracking detectors after the upgrade to the hl - lhc with an instantaneous luminosity of up to will be the exposure to high radiation .
the atlas pixel system will be prospectively exposed to particle fluences up to ( 1 mev neutron equivalent ) @xcite . to maximize the hit efficiency and reduce the leakage current and power dissipation after irradiation , thin sensors are being developed .
sensors with a thickness of 100 and 150 were found to reach the same hit efficiency as thicker sensors already at a bias voltage of 300 v shown in fig [ effthick4 ] . + a highest hit efficiency of around 97% was obtained for perpendicular incident tracks at a fluence of , the expected fluence for the second layer at hl - lhc @xcite ..
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the main inefficiencies are caused by the bias dot and the bias rail , as described in @xcite for fluences up to . in this
paper , different designs of n - in - p planar hybrid pixel modules are investigated at the expected fluence of the second layer .
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Suppose that you have an abstract for a scientific paper: we use free probability techniques to compute borders of spectra of non hermitian operators in finite von neumann algebras which arise as `` free sums '' of `` simple '' operators . to this end
, the resolvent is analyzed with the aid of the haagerup inequality .
concrete examples coming from reduced @xmath0-algebras of free product groups and leading to systems of polynomial equations illustrate the approach . .
And you have already written the first three sentences of the full article: computation of spectra of convolution operators on discrete groups was one of the motivations behind the development of free probability .
it has some interest for harmonic analysis and analysis of random walks on free products of discrete groups , where under the name of the _ transition operator _
these operators carry much information about the random walks under consideration ..
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_ free probability _ is an abstract framework for harmonic analysis on the free group in the language of non - commutative probability .
let us introduce briefly the terminology of the latter , which is used throughout the paper .
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Suppose that you have an abstract for a scientific paper: the scattering of two - dimensional ( 2d ) massless dirac electrons is investigated in the presence of a random array of circular mass barriers . the inverse momentum relaxation time and the hall factor
are calculated and used to obtain parallel and perpendicular resistivity components within linear transport theory .
we found a non zero perpendicular resistivity component which has opposite sign for electrons in the different @xmath0 and @xmath1 valleys .
this property can be used for valley filter purposes . the total cross - section for scattering on penetrable barriers exhibit resonances due to the presence of quasi - bound states in the barriers that show up as sharp gaps in the cross - section while for schrdinger electrons they appear as peaks . .
And you have already written the first three sentences of the full article: nanostructures have become the system of choice for studying transport over the past few years@xcite . starting with 2d ( two dimensional ) electron systems at the interface of two different materials several decades ago@xcite ,
recently it has shifted to 2d _ relativistic _
materials e. g. graphene @xcite and topological insulators@xcite . in pristine graphene.
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the conduction and valence bands touch each other in six points of the brillouin zone and are defined by two independent sets of cones commonly called @xmath0 and @xmath1 . near these points
the electronic dispersion is linear which corresponds to the dispersion of massless relativistic particles , described by the dirac - weyl equation@xcite . during the last decades
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Suppose that you have an abstract for a scientific paper: in this paper , we consider the problem of distributed optimal control of linear dynamical systems with a quadratic cost criterion .
we study the case of output feedback control for two interconnected dynamical systems , and show that the linear optimal solution can be obtained from a combination of two uncoupled riccati equations and two coupled riccati equations . .
And you have already written the first three sentences of the full article: decentralized control has been a challenging area of open research for over three decades . however , these problems are still intractable in general . in one of the earliest works
, it was shown that for a linear system subject to quadratic cost and gaussian noise , complex nonlinear controllers could outperform any given linear controller ( see @xcite ) .
centralized controller design problems assume a classical information pattern where each system has access to the information of all other systems ..
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however , in decentralized problems , different systems have access to different information sets and their decisions are based on local measurements .
solving the problem in the presence of this constraint is a much harder problem .
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Suppose that you have an abstract for a scientific paper: the idea of perturbation independent decay ( pid ) has appeared in the context of survival - probability studies , and lately has emerged in the context of quantum irreversibility studies . in both cases
the pid reflects the lyapunov instability of the underlying semiclassical dynamics , and it can be distinguished from the wigner - type decay that holds in the perturbative regime . the theory of the survival probability is manifestly related to the parametric theory of the local density of states ( ldos ) .
in contrast to that the physics of quantum irreversibility requires to take into account subtle cross correlations which are not captured by the ldos alone . .
And you have already written the first three sentences of the full article: the study of quantum irreversibility @xcite has become lately of much interest @xcite due to its potential relevance to quantum computing , and to the theory of dephasing @xcite .
following @xcite we define in section 2 the main object of the present paper : this is the `` fidelity '' , also known as `` loschmidt echo '' , which constitutes a measure for quantum irreversibility .
the analysis of `` fidelity '' necessitates a generalization of the theory regarding `` survival probability '' @xcite . in section.
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3 we remind the reader that the latter reduces to the analysis of the local density of states ( ldos ) @xcite .
is it possible to make a similar reduction in case of the `` fidelity '' ? at first sight such reduction looks feasible because the general physical picture looks very similar ( sections 5 - 6 ) . in the present paper
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Suppose that you have an abstract for a scientific paper: we improve the non - asymptotic key rate shown by scarani and renner by proposing several methods to construct tighter conservative confidence intervals of the phase error rate than one shown by them .
in addition , we show that the accurate channel estimation method non - asymptotically increases the key rate over the amplitude damping channel as well as the asymptotic case in the bb84 protocol . .
And you have already written the first three sentences of the full article: quantum key distribution ( qkd ) has attracted great attention as a feasible application of quantum information science with the current device technology @xcite .
the goal of a qkd protocol is to share a random bit sequence not known by the eavesdropper eve , between the legitimate sender alice and the receiver bob .
the fundamental feature of qkd protocols is that the maximum amount of information gained by eve can be determined from the channel estimate between alice and bob ..
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such a task can not be conducted in classical key distribution schemes .
if the estimated amount is lower than a threshold , then alice and bob determine the length of a secret key from the estimated amount of eve s information , and can share the secret key by performing the information reconciliation ( error correction ) and the privacy amplification . since the key rate , which is the length of securely sharable key per channel use , is one of the most important criteria for the efficiency of qkd protocols , the estimation of the channel is of primary importance . conventionally in the bennett - brassard 1984 ( bb84 ) protocol @xcite
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Suppose that you have an abstract for a scientific paper: we address the issue of variable selection in the regression model with very high ambient dimension , that is , when the number of variables is very large .
the main focus is on the situation where the number of relevant variables , called intrinsic dimension , is much smaller than the ambient dimension @xmath0 . without assuming any parametric form of the underlying regression function , we get tight conditions making it possible to consistently estimate the set of relevant variables . these conditions relate the intrinsic dimension to the ambient dimension and to the sample size .
the procedure that is provably consistent under these tight conditions is based on comparing quadratic functionals of the empirical fourier coefficients with appropriately chosen threshold values .
the asymptotic analysis reveals the presence of two quite different re gimes .
the first regime is when the intrinsic dimension is fixed . in this case
the situation in nonparametric regression is the same as in linear regression , that is , consistent variable selection is possible if and only if @xmath1 is small compared to the sample size @xmath2 .
the picture is different in the second regime , that is , when the number of relevant variables denoted by @xmath3 tends to infinity as @xmath4 .
then we prove that consistent variable selection in nonparametric set - up is possible only if @xmath5 is small compared to @xmath6 .
we apply these results to derive minimax separation rates for the problem of variable selection . .
And you have already written the first three sentences of the full article: real - world data such as those obtained from neuroscience , chemometrics , data mining or sensor - rich environments are often extremely high - dimensional , severely underconstrained ( few data samples compared to the dimensionality of the data ) and interspersed with a large number of irrelevant or redundant features .
furthermore , in most situations the data is contaminated by noise , making it even more difficult to retrieve useful information from the data .
relevant variable selection is a compelling approach for addressing statistical issues in the scenario of high - dimensional and noisy data with small sample size . starting from mallows @xcite , akaike @xcite , schwarz @xcite who introduced , respectively ,.
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the famous criteria @xmath7 , aic and bic , the problem of variable selection was extensively studied in the statistical and machine learning literature both from the theoretical and algorithmic viewpoints .
it appears , however , that the theoretical limits of performing variable selection in the context of nonparametric regression are still poorly understood , especially when the number of variables , denoted by @xmath0 and referred to as ambient dimension , is much larger than the sample size @xmath2 .
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Suppose that you have an abstract for a scientific paper: we present the analysis of a ccd survey of 31 nearby ( @xmath0 110 mpc ) edge - on spiral galaxies .
the three - dimensional one - component best fit models provide their disk - scalelengths @xmath1 and for the first time their disk cut - off radii @xmath2 .
we confirm for this sample the existence of such sharp truncations , and find a significantly lower mean value of the distance independent ratio @xmath3 than the standard value of @xmath4 often used in the literature .
our data show no correlation of these parameters with hubble type , whereas we report a correlation between @xmath5 and the distance based scalelength in linear units .
compared to the milky way we find only lower values of @xmath5 , explained either by possible selection effects or by the completely different techniques used .
we discuss our data in respect to present models for the origin of the cut - off radii , either as a relict of the galaxy formation process , or as an evolutionary phenomenon . .
And you have already written the first three sentences of the full article: although _ cut - off radii _ of spiral galaxies are known for about 20 years no unique physical explanation has been given to describe this observational phenomenon .
they were already mentioned by van der kruit ( @xcite ) , who stated , based on photographic material , that the outer parts of disks of spiral galaxies do not retain their exponential light distribution to such faint levels , whereas the exponential behaviour of the radial light distribution for the inner part was well accepted ( de vaucouleurs @xcite , freeman @xcite ) .
for three nearby edge - on galaxies he claimed , that the typical radial scalelength @xmath1 steepens from 5 kpc to about 1.6 kpc at the edge of the disk ..
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this is confirmed by modern deep ccd imaging ( abe et al .
@xcite , fry et al .
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Suppose that you have an abstract for a scientific paper: when utilities are additive , we uncovered in our previous paper @xcite many similarities but also surprising differences in the behavior of the familiar _ competitive rule _ ( with equal incomes ) , when we divide ( private ) _ goods _ or _ _
bads__.the rule picks in both cases the critical points of the product of utilities ( or disutilities ) on the efficiency frontier , but there is only one such point if we share goods , while there can be exponentially many in the case of bads .
we extend this analysis to the fair division of _ mixed items _ : each item can be viewed by some participants as a good and by others as a bad , with corresponding positive or negative marginal utilities .
we find that the division of mixed items boils down , normatively as well as computationally , to a variant of an _ all goods _ problem , or of an _ all bads _ problem : in particular the task of dividing the non disposable items must be either good news for everyone , or bad news for everyone .
if at least one feasible utility profile is positive , the competitive rule picks the unique maximum of the product of ( positive ) utilities .
if no feasible utility profile is positive , this rule picks all critical points of the product of _ _ dis__utilities on the efficient frontier . .
And you have already written the first three sentences of the full article: in our previous paper @xcite we consider fair division of ( private , divisible ) items under linear preferences , represented for convenience by additive utilities .
we explain there the appeal of this domain restriction for the practical implementation of division rules vindicated by theoretical analysis .
we focus there on the _ competitive rule _ ( aka competitive equilibrium with equal incomes ) to divide the items , and contrast its behavior when we divide _ goods _ ( assets , such as family heirlooms , real estate , land , stocks ) , and when we divide _ bads _ ( chores , workloads , liabilities , noxious substances or facilities ) ..
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several normative properties of this rule are identical in both contexts , e. g. , _ no envy _ and a simple version of maskin monotonicity that we call _ independence of lost bids_. however the unexpected finding is that several aspects of the rule are very different in the two contexts : dividing _ bads _ is not a mirror image of dividing _ goods . _
the competitive rule picks a unique welfare profile when it divides goods , but for dividing bads it often proposes many ( up to exponentially many in the number of agents and bads ) allocations with different welfare consequences ; in the former case the competitive welfare profile is continuous in the marginal rates of substitution , in the latter case such continuity is not feasible .
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Suppose that you have an abstract for a scientific paper: we conduct numerical simulations based on a model of blowing snow to reveal the long - term properties and equilibrium state of aeolian particle transport from @xmath0 to @xmath1 above the flat surface .
the numerical results are s follows .
( i ) time - series data of particle transport are divided into development , relaxation , and equilibrium phases , which are formed by rapid wind response below @xmath2 and gradual wind response above @xmath2 .
( ii ) the particle transport rate at equilibrium is expressed as a power function of friction velocity , and the index of @xmath3 implies that most particles are transported by saltation .
( iii ) the friction velocity below @xmath4 remains roughly constant and lower than the fluid threshold at equilibrium .
( iv ) the mean particle speed above @xmath5 is less than the wind speed , whereas that below @xmath5 exceeds the wind speed because of descending particles .
( v ) the particle diameter increases with height in the saltation layer , and the relationship is expressed as a power function . through comparisons with the previously reported random - flight model
, we find a crucial problem that empirical splash functions can not reproduce particle dynamics at a relatively high wind speed . .
And you have already written the first three sentences of the full article: snow / sand erosion and deposition due to wind emit many deposited particles into the atmosphere , and drifting snow and dust storms are generated as massive particles are transported .
additionally , fluid - particle and particle - particle interactions increase spatial heterogeneity , resulting in the formation of microscopic and macroscopic structures on snow / ice surfaces , sand deserts , and beaches . for example , wind ripples and dunes are observed in natural fields .
the particle transport by the aeolian processes is a key factor to understand the morphodynamics of objects ..
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generally , aeolian particle transport is maintained and developed through four physical sub - processes @xcite : aerodynamical entrainment , wind - blown particle dynamics , splash caused by particle - granular bed collision , and wind modification ( fig . [ fig:1 ] ) . in the equilibrium state , the wind profile is almost fixed because of the momentum exchange with particles , whereas the dynamics of particles ejected from granular beds consists of three different modes : creep , saltation , and suspension .
these motions strongly depend on wind speed and particle diameter ; thus , the spatial structure is complex in particle transport .
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Suppose that you have an abstract for a scientific paper: the epoch of reionization ( eor ) sets a fundamental benchmark in cosmic structure formation , corresponding to the formation of the first luminous objects that act to ionize the neutral intergalactic medium ( igm ) .
recent observations at near - ir and radio wavelengths imply that we are finally probing into this key epoch of galaxy formation at @xmath0 . the square kilometer array ( ska )
will provide critical insight into the eor in a number of ways .
first , the ability of the ska to image the neutral igm in 21 cm emission is a truly unique probe of the process of reionization , and is recognized as the next necessary and fundamental step in our study of the evolution of large scale structure and cosmic reionization .
second , study of hi 21 cm absorption toward the first radio loud objects probes small to intermediate scale structure in the neutral cosmic web , as well as hi in the first collapsed structures ( proto - disks and mini - halos ) . and
third , the incomparable sensitivity of the ska allows for the study of the molecular gas , dust , and star formation activity in the first galaxies , as well as the radio continuum emission from the first accreting massive black holes .
such objects will be obscured at optical wavelengths due to absorption by the neutral igm . .
And you have already written the first three sentences of the full article: after recombining at @xmath1 , the intergalactic medium ( igm ) remains neutral until the formation of the first luminous sources in the universe . these act to reionize the universe , leading to the fully ionized
igm seen today ( neutral fraction @xmath2 ) .
the epoch of cosmic reionization ( eor ) therefore sets a fundamental benchmark in cosmic structure formation , corresponding to the formation of the first luminous objects ( star forming galaxies and/or accreting massive black holes ) ..
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the last few years has seen a revolution in our understanding of the eor , in particular , the first observational constraints on the redshift for the eor .
the discovery of the gunn peterson absorption trough in the spectra of the most distant quasars ( @xmath3 ) , corresponding to ly @xmath4 absorption by the neutral igm , implies that we have finally probed into the eor @xcite .
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Suppose that you have an abstract for a scientific paper: * magnetoresistance ( mr ) has attracted tremendous attention for possible technological applications .
understanding the role of magnetism in manipulating mr may in turn steer the searching for new applicable mr materials . here
we show that antiferromagnetic ( afm ) gdsi metal displays an anisotropic positive mr value ( pmrv ) , up to @xmath0 415% , accompanied by a large negative thermal volume expansion ( ntve ) . around @xmath1
the pmrv translates to negative , down to @xmath0 -10.5% .
their theory - breaking magnetic - field dependencies [ pmrv : dominantly linear ; negative mr value ( nmrv ) : quadratic ] and the unusual ntve indicate that pmrv is induced by the formation of magnetic polarons in 5__d _ _ bands , whereas nmrv is possibly due to abated electron - spin scattering resulting from magnetic - field - aligned local 4__f _ _ spins .
our results may open up a new avenue of searching for giant mr materials by suppressing the afm transition temperature , opposite the case in manganites , and provide a promising approach to novel magnetic and electric devices . * utf8zhkai magnetoresistance ( mr )
, a change in electrical resistivity when an external magnetic field ( @xmath2 ) applied , occurs in metals , inorganic and organic semiconductors , and particularly close to an intermediate regime of the transformations of charge ( insulator , metal ) order and spin [ paramagnetic ( pm ) , ferromagnetic ( fm ) ] order in thin manganites films as a colossal negative mr value ( nmrv ) @xcite .
the colossal mr ( cmr ) in manganites is accompanied by a shift of the transition temperature to a higher value by applied magnetic field so that a sharp peak appears in the mr values near the transition , e.g. , the nmrv reaches @xmath0 -95% at @xmath2 = 15 t near @xmath3 = 240 k in la@xmath4sr@xmath5mno@xmath6 @xcite .
although the double exchange interaction can qualitatively explain the cmr effect based only on the charge and spin degrees of freedom , the exact picture still remains elusive....
And you have already written the first three sentences of the full article: * x - ray powder diffraction refinements and anisotropic stains . * the observed and refined x - ray powder patterns at 10 k and 300 k
are shown in fig .
the listed reliability factors in the caption indicate good refinements . in fig ..
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s1b , the full width at half maximum of the nuclear ( 1 1 2 ) bragg peak by lorentzian fitting increases largely below @xmath1 , indicating the existence of strong strains that are produced by the gradual formation of the antiferromagnetic ( afm ) state that is a process accompanied by the afm sublattice domain movements .
we first measured the standard lab@xmath69 powders , with which we extracted the instrumental resolution .
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Suppose that you have an abstract for a scientific paper: we calculate the tunneling conductance spectra of a ferromagnetic metal / insulator / triplet superconductor from the reflection amplitudes using the blonder - tinkham - klapwijk ( btk ) formula . for the triplet superconductor ,
we assume one special @xmath0-wave order parameter , having line nodes , and two two dimensional @xmath1-wave order parameters with line nodes , breaking the time reversal symmetry .
also we examine nodeless pairing potentials .
the evolution of the spectra with the exchange potential depends solely on the topology of the gap .
the weak andreev reflection within the ferromagnet results in the suppression of the tunneling conductance and eliminates the resonances due to the anisotropy of the pairing potential .
the tunneling spectra splits asymmetrically with respect to @xmath2 under the influence of an external magnetic field .
the results can be used to distinguish between the possible candidate pairing states of the superconductor sr@xmath3ruo@xmath4 . .
And you have already written the first three sentences of the full article: the recent discovery of superconductivity in sr@xmath3ruo@xmath4 has attracted much theoretical and experimental interest @xcite .
the time reversal symmetry is broken for the superconductor sr@xmath3ruo@xmath4 , and the magnetic field is spontaneously induced as shown by @xmath5sr experiment . @xcite .
the knight - shift shows no change when passing through the superconducting state and is a clear indication for spin triplet pairing state , with a @xmath6-vector aligned to the @xmath7-axis ..
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in addition the band structure calculations @xcite and de haas van alphen measurements @xcite show little dispersion along @xmath8 which is consistent with a two dimensional basis function on a cylindrical fermi surface .
furthermore , the presence of a large residual density of states of quasiparticles inside the superconducting gap is evident from the linear temperature dependence of the nuclear spin lattice relaxation rate @xmath9 of @xmath10ru bellow @xmath11 .
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Suppose that you have an abstract for a scientific paper: dual superconductivity in the confining phase of gauge theories is discussed in terms of a disorder parameter which vanishes in normal phase and is different from zero in the superconducting phase .
# 1*#1 * .
And you have already written the first three sentences of the full article: there exists evidence from lattice simulations that qcd vacuum is a dual superconductor in the confining phase , and undergoes a transition to normal state at deconfinement temperature@xcite .
this support the idea that confinement is produced by dual meissner effect@xcite .
however there are aspects of confinement which are not understood in this scenario ..
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the evidence for dual superconductivity from lattice simulations can be put into two categories : phenomenological and direct .
phenomenological evidence is the observation of basic features which are consistent with the picture : + 1 ) existence of string tension , as detected by the area law behaviour of wilson loops@xcite , indicating that confinement really takes place in qcd .
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Suppose that you have an abstract for a scientific paper: in ambient re - scatter communications , devices convey information by modulating and re - scattering the radio frequency signals impinging on their antennas . in this correspondence
, we consider a system consisting of a modulated continuous carrier multiple - input multiple - output ( mimo ) link ( primary ) and a multi - antenna modulated re - scatter ( mrs ) node ( secondary ) , where the mrs node uses the signal generated by the primary transmitter .
the receiver tries to decode both the original transmitted message and the information added by the mrs antennas .
we show that the sum capacity of this system exceeds that , which the mimo system could achieve alone .
we also consider the impact of channel estimation errors under least squares channel estimation .
the results suggest that the estimation error has negative impact on the capacity , however , its severity can be minimised by increasing the number of receiver antennas .
backscatter , re - scatter , bi - static channel , mimo , keyhole channel , modulation coding , polyphase coding . .
And you have already written the first three sentences of the full article: of the limiting factors of connecting things to the internet using wireless technologies is the availability of energy .
one solution is provided by the modulated back - scattering ( mbs ) systems , such as rfid , where the nodes ( tags ) modulate their information onto a carrier generated by a reader , and the reader decodes the modulated information . in the advanced forms of mbs systems ,
multiple - antenna techniques are applied to increase the capacity @xcite and improve the reliability @xcite ..
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the communication range can be increased by allowing a carrier transmitter and a reader ( receiver ) to be physically separated , referred to as a bi - static mbs system @xcite .
recently , a new communication technology is emerging based on the fact that the tags can re - scatter even modulated signals , often referred to as ambient mbs system @xcite . these systems
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Suppose that you have an abstract for a scientific paper: we present a combined maximum - entropy method ( mem ) and mexican hat wavelet ( mhw ) analysis in order to recover the different components of the microwave sky .
we apply this technique to simulated observations by the esa planck satellite in small patches of the sky . in particular
, the introduction of the mhw allows one to detect and subtract the brightest point sources present in the input data and therefore to improve the reconstructions of the cmb and foreground components achieved by mem on its own .
in addition , a point source catalogue at each planck frequency is produced , which is more complete and accurate than those obtained by each technique independently . .
And you have already written the first three sentences of the full article: cosmic microwave background ( cmb ) observations carry a wealth of information about the universe .
indeed , an accurate knowledge of the cmb anisotropies can place tight constraints on fundamental parameters as well as to discriminate between competing theories of structure formation .
future cmb experiments such as the nasa map satellite and the planck mission from esa , will provide with multifrequency data at high resolution and sensitivity ..
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however , these data contain not only the cosmological signal but also galactic foregrounds , extragalactic point sources , thermal and kinetic sunyaev - zelodvich ( sz ) emission from cluster of galaxies and instrumental noise .
therefore our capacity to recover all the valuable information encoded in the cmb will critically depend on our ability to denoise and separate the cosmological signal from the rest of components of the microwave sky . to perform such a separation ,
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Suppose that you have an abstract for a scientific paper: in rotationally constrained percolation models , a site of a percolation cluster could be occupied more than once from different directions due to the nature of the rotational constraint .
a state variable @xmath0 is assigned to each lattice site whose value corresponds to the number times it has been visited during the growth of a cluster .
it is proposed here that the percolation transition and the multifractal aspects of infinite percolation clusters under rotational constraint can be studied defining suitable measures in terms of the state variable @xmath0 .
this method does not require to introduce any external agency like an electric current or a random walker in order to explore multifractality as in the case of ordinary percolation .
the state variable representation also describes the universality class of the percolation models appropriately . .
And you have already written the first three sentences of the full article: multifractals appear in a wide range of situations like energy dissipation in turbulent flows@xcite , electronic eigenstates at metal insulator transition@xcite , diffusion in porous structures@xcite , diffusion limited aggregation@xcite , fluctuations in finance@xcite , dynamics of human heartbeat@xcite and many others .
the multifractal properties associated with the infinite percolation clusters at the percolation threshold @xmath1 is considered in this paper . in ordinary percolation ( op)@xcite ,
a cluster is generated by occupying a lattice site randomly with a probability @xmath2 or remains empty with a probability @xmath3 ..
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each site of a percolation cluster then has two states , occupied or empty .
the average @xmath4 moments of the cluster size distribution of percolation clusters are linearly dependent on the moment @xmath4 and described by a single fractal dimension @xmath5@xcite . in order to study the multifractal aspects of percolation clusters , usually
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Suppose that you have an abstract for a scientific paper: in this paper we adopt a method to analyse absorption line spectra from elliptical galaxies that determines the dynamics of the galaxy and at the same time offers a way to study the stellar populations in that galaxy by a direct fit to the spectra .
the result of the modelling is a distribution function for each stellar population that is considered in the fit .
the method is described in detail in an accompanying paper @xcite .
this paper reports on a dynamical stellar population study in ngc 3258 , based on spectra in two different wavelength regions , the near - ir ca ii triplet around 8600 and the ca h and k lines around 3900 .
these absorption lines have discriminating power toward various stellar types .
the dynamical model shows an increase in dwarfs ( represented by g2v stars ) toward the centre .
most of the rotation in the model is delivered by the giants ( represented by m1iii stars ) . moreover , the different models that were considered indicate that establishing a potential for a galaxy is dependent on the wavelength range used for the modelling .
[ firstpage ] methods : numerical - methods : statistical - galaxies : kinematics and dynamics - galaxies : elliptical and lenticular , cd - galaxies : individual ( ngc 3258 ) - galaxies : structure .
And you have already written the first three sentences of the full article: elliptical galaxies are no longer seen as simple isothermal objects that follow a de vaucouleurs - law and that are chemically well mixed .
color gradients indicating that elliptical galaxy centres have redder colours than the outer regions ( e.g. @xcite , @xcite , @xcite ) , and variations in line strengths ( see @xcite and references therein ) can be interpreted in terms of a metallicity or an age gradient @xcite .
moreover , spectroscopic studies revealed that a considerable number of early - type galaxies have a kinematically distinct core , that may have a separate stellar population ( @xcite , @xcite , @xcite , @xcite ) ..
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current stellar population modelling techniques for elliptical galaxies explicitly take an evolution scenario into account .
most of them use theoretically calculated isochrones and a library of theoretical or observed stellar spectra .
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Suppose that you have an abstract for a scientific paper: within the scope of bianchi type - vi cosmological model we study the role of spinor field in the evolution of the universe . it is found that due to the spinor affine connections the energy - momentum tensor of the spinor field possesses non - diagonal components .
the non - triviality of non - diagonal components of the energy - momentum tensor imposes some severe restrictions either on the spinor field or on the metric functions or on both of them .
but unlike in cases of bianchi type - i or @xmath0 , in case of bianchi type - vi model it does not lead to the elimination of spinor field nonlinearity or mass term in the spinor field lagrangian . it is also found that depending on the sign of self - coupling constant the model can give rise to late time acceleration or generate oscillatory mode of evolution . -24pt .
And you have already written the first three sentences of the full article: with the more and more observational data available from far sky , the need for a change in the standard cosmological paradigm becomes inevitable .
prior to 1998 when we had no idea about the accelerating mode of expansion the available observational data were well fit in the standard einstein model .
but the discovery and further reconfirmation of the existence of the late time accelerated mode of expansion @xcite have opened a new window for change . along with.
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that comes out a number of alternative models of the evolution of the universe .
the most popular among the models are those which consider the old einstein theory with a new `` matter '' as a source field . the models with @xmath1-term @xcite , quintessence @xcite , chaplygin gas @xcite etc .
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Suppose that you have an abstract for a scientific paper: we exhibit infinitely many overtwisted , right veering , non
destabilizable open books , thus providing infinitely many counterexamples to a conjecture of honda kazez mati .
the page of all our open books is a four holed sphere and the underlying 3manifolds are lens spaces . .
And you have already written the first three sentences of the full article: the purpose of this note is to construct infinitely many counterexamples to a conjecture of honda , kazez and mati from @xcite . for the basic notions of contact topology not recalled below we refer the reader to @xcite .
let @xmath0 be a compact , oriented surface with boundary and @xmath1 the group of orientation preserving diffeomorphisms of @xmath0 which restrict to @xmath2 as the identity , up to isotopies fixing @xmath2 pointwise .
an _ open book _ ( a.k.a . an _ abstract open book _ ) is a pair @xmath3 where @xmath0 is a surface as above and @xmath4 ..
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giroux @xcite introduced a fundamental operation of _ stabilization _
@xmath5 on open books , and proved the existence of a 11 correspondence between the set of open books modulo stabilization and the set of contact 3manifolds modulo isomorphism ( see e.g. @xcite for details ) .
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Suppose that you have an abstract for a scientific paper: pulse walk - off in the process of sum frequency generation in a nonlinear @xmath0 crystal is shown to be responsible for pulse jittering which is reminiscent to the zitterbewegung ( trembling motion ) of a relativistic freely moving dirac particle .
an analytical expression for the pulse center of mass trajectory is derived in the no - pump - depletion limit , and numerical examples of zitterbewegung are presented for sum frequency generation in periodically - poled lithium niobate .
the proposed quantum - optical analogy indicates that frequency conversion in nonlinear optics could provide an experimentally accessible simulator of the dirac equation . .
And you have already written the first three sentences of the full article: originally predicted by schrdinger in the study of the dirac equation @xcite , zitterbewegung ( zb ) refers to the trembling motion of a freely - moving relativistic quantum particle that arises from the interference between the positive- and negative - energy parts of the spinor wave function @xcite . for a free electron ,
the dirac equation predicts the zb to have an extremely small amplitude ( of the order of the compton wavelength @xmath1 ) and an extremely high frequency ( @xmath2 ) , making such an effect experimentally inaccessible .
in addition , the physical relevance of zb in relativistic quantum mechanics is a controversial issue because such an effect arises in the framework of the single - particle picture of the dirac equation , but not in quantum field theory @xcite ..
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the notion of zb and resulting formalism , however , are not peculiar to relativistic quantum dynamics , and phenomena analogous to zb , which underly the same mathematical model of the dirac equation , have so far predicted in a wide variety of quantum and even classical physical systems , including among others semiconductors and quantum wells @xcite , trapped ions @xcite , graphene @xcite , cold atoms @xcite , acoustic @xcite and photonic @xcite systems . simulations of relativistic quantum effects using experimentally - accessible physical set - ups , in which parameter tunability allows access to different physical regimes , have seen in recent years an increasing interest , culminating to the very recent first experimental observation of a quantum analogue of zb using a single trapped ion set to behave as a free relativistic quantum particle @xcite . in the optical context , the use of photonic systems to mimic quantum phenomena in the lab has seen a continuous and increasing interest ( see , for instance , @xcite and references therein ) ; in particular , optical analogues of the relativistic zb have been recently proposed to occur in photonic crystals @xcite , metamaterial slabs @xcite , and binary waveguide arrays @xcite . in this work
it is shown theoretically that a classical analogue of zb can be observed in a much simpler and well - known set - up of nonlinear optics , namely in the process of sum frequency generation of light waves in a nonlinear @xmath0 medium @xcite in presence of pulse ( or spatial ) walk off . in the nonlinear optics context ,
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Suppose that you have an abstract for a scientific paper: we analyze the simultaneous time - optimal control of two - spin systems .
the two non coupled spins which differ in the value of their chemical offsets are controlled by the same magnetic fields .
using an appropriate rotating frame , we restrict the study to the case of opposite shifts .
we then show that the optimal solution of the inversion problem in a rotating frame is composed of a pulse sequence of maximum intensity and is similar to the optimal solution for inverting only one spin by using a non - resonant control field in the laboratory frame .
an example is implemented experimentally using techniques of nuclear magnetic resonance . .
And you have already written the first three sentences of the full article: since its discovery in 1945 by purcell , torrey and pound , nuclear magnetic resonance ( nmr ) has become a powerful physical tool to study molecules and matter in a variety of domains extending from biology and chemistry to solid physics and quantum mechanics @xcite .
nmr involves the manipulation of nuclear spins via its interaction with a magnetic field , and is therefore a domain where techniques of quantum control can be applied ( see @xcite and references therein ) .
such an approach has many potential applications ranging from the improvement of the resolution and sensitivity of nmr spectroscopy experiments @xcite to quantum computing @xcite ..
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the control technology developed over the past fifty years allows the use of sophisticated control fields for spectroscopy and also permits the implementation of complex quantum algorithms @xcite . in this context , some challenging control problems are raised by the experimental constraints of nmr experiments .
roughly speaking , the measured signal is the magnetization of a sample which is produced by a large number of spin systems .
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Suppose that you have an abstract for a scientific paper: we derive an alternative representation for the relativistic non local kinetic energy operator and we apply it to solve the relativistic salpeter equation using the variational sinc collocation method .
our representation is _ analytical _ and does not depend on an expansion in terms of local operators .
we have used the relativistic harmonic oscillator problem to test our formula and we have found that arbitrarily precise results are obtained , simply increasing the number of grid points .
more difficult problems have also been considered , observing in all cases the convergence of the numerical results . using these results
we have also derived a new representation for the quantum mechanical green s function and for the corresponding path integral .
we have tested this representation for a free particle in a box , recovering the exact result after taking the proper limits , and we have also found that the application of the feynman kac formula to our green s function yields the correct ground state energy . our path integral representation allows to treat hamiltonians containing non local operators and it could provide to the community a new tool to deal with such class of problems . .
And you have already written the first three sentences of the full article: the appearance of non local operators in the relativistic extensions of the schrdinger equation poses a serious challenge both to analytical and numerical calculations .
however , the inclusion of relativistic effects is crucial for example in the study of meson phenomenology , where the bethe - salpeter equation ( bse ) provides the correct theoretical tool to describe relativistic bound states . replacing the kernel in the bse with an instantaneous local potential one obtains a relativistic schrdinger equation , which is also known as `` spinless salpeter equation '' ( sse ) . in such case
the hamiltonian operator is typically given by = + v ( ) ..
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[ eq1 ] from a technical point of view , the inclusion in the hamiltonian of the relativistic kinetic energy operator , @xmath0 , complicates the solution of the problem because of its non local nature .
the great phenomenological relevance of the sse has motivated in the past twenty years many efforts to solve this equation , either using analytical or numerical techniques . early work on this subject is contained for example in @xcite . the method described in @xcite , which allows one to obtain
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Suppose that you have an abstract for a scientific paper: we report a study of the stellar content of the near - infrared cluster [ dbs2003]157 embedded in the extended hii region gal331.31 - 00.34 , which is associated with the iras source 16085 - 5138 .
@xmath0 photometry was carried out in order to identify potential ionizing candidates , and the follow - up nir spectroscopy allowed the spectral classification of some sources , including two o - type stars . a combination of nir photometry and spectroscopy data was used to obtain the distance of these two stars , with the method of spectroscopic parallax : irs298 ( o6v , @xmath1kpc ) and irs339 ( o9v , @xmath2kpc ) .
adopting the average distance of @xmath3kpc and comparing the lyman continuum luminosity of these stars with that required to account for the radio continuum flux of the hii region , we conclude that these two stars are the ionizing sources of gal331.31 - 00.34 .
young stellar objects ( ysos ) were searched by using our nir photometry and mir data from the glimpse survey .
the analysis of nir and mir colour - colour diagrams resulted in 47 yso candidates .
the glimpse counterpart of iras16085 - 5138 , which presents iras colour indices compatible with an ultra - compact hii region , has been identified .
the analysis of its spectral energy distribution between @xmath4 and @xmath5 m revealed that this source shows a spectral index @xmath6 between @xmath4 and @xmath7 m , which is typical of a yso immersed in a protostellar envelope .
lower limits to the bolometric luminosity and the mass of the embedded protostar have been estimated as @xmath8 and @xmath9 , respectively , which corresponds to a b0b1v zams star .
[ firstpage ] stars : early - type hii regions stars : pre - main - sequence . .
And you have already written the first three sentences of the full article: the study of the stellar content and the determination of the distances of hii regions and star - forming complexes associated with massive molecular clouds are fundamental for the determination of the spiral structure and the rotation curve of the galaxy .
also , the assessment of galactic gradients of chemical abundances and electron temperatures have strong dependence on the accuracy of the distance estimates .
the norma region is a very interesting sector of the galaxy for this investigation , since the line of sight intersects three spiral arms ( sagittarius - carina , scutum - crux , and norma ) ..
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in addition to the tens of optical hii regions identified by @xcite , radio observations have revealed many other hii regions heavily obscured by interstellar dust .
the ionizing stellar clusters of some of these objects have been studied in detail in the last decade .
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Suppose that you have an abstract for a scientific paper: recent generations of field programmable gate arrays ( fpgas ) have become indispensable tools for complex state machine control and signal processing , and now routinely incorporate cpu cores to allow execution of user software code . at the same time , their exceptional performance permits low - power implementation of functionality previously the exclusive domain of dedicated analog electronics .
specific examples presented here use fpgas as discriminator , time - to - digital ( tdc ) and analog - to - digital converter ( adc ) .
all three cases are examples of instrumentation for current or future astroparticle experiments . .
And you have already written the first three sentences of the full article: recent generations of field programmable gate arrays ( fpgas ) have become incredibly powerful logic devices . with companion sensors and a data interface ,
they become valuable data collection nodes for the physical sciences . for certain applications ,
it has become apparent that these logic devices themselves can serve as the crucial processing elements of instrumentation electronics ..
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specific applications where this resource can be tapped include , but are not limited to : * compact form factor ( complete system with very small footprint ) * ultra low - power compared with discrete systems of comparable functionality * input - output ( i / o ) limited systems * low electromagnetic interference ( emi ) specific examples presented here use the xilinx spartan-3 fpga , a low - cost and flexible device generously made available through the xilinx university program @xcite .
high performance instrumentation is increasingly a marriage between custom application specific integrated circuits ( asics ) and high performance fpgas , capable of processing and transmitting the data collected . in certain applications ,
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Suppose that you have an abstract for a scientific paper: gapless nodal quasiparticles emerge at a low - energy regime of high-@xmath0 cuprate superconductors due to the @xmath1 gap symmetry .
we study the unusual renormalizations of the fermi velocity @xmath2 and gap velocity @xmath3 of these quasiparticles close to various quantum critical points in a superconducting dome .
special attention is paid to the behavior of the velocity ratio , @xmath4 , since it determines a number of observable quantities .
we perform a renormalization - group analysis and show that the velocity ratio may vanish , approach unity , or diverge at different quantum critical points .
the corresponding superfluid densities and critical temperatures are suppressed , slightly increased , or significantly enhanced .
the effects of three types of static disorders , namely , random mass , random gauge potential , and random chemical potential , on the stability of the system are also addressed .
an analogous analysis reveals that both random mass and random gauge potential are irrelevant .
this implies that these fixed points of the velocity ratio are stable , and hence observable effects ignited by them are unchanged .
however , the random chemical potential is marginal . as a result
, these fixed points are broken , and thus , the instabilities of quantum phase transitions are triggered . .
And you have already written the first three sentences of the full article: it has been well - established that high-@xmath0 cuprate superconductors have an anisotropic @xmath1 energy gap .
this gap vanishes at four nodes @xmath5 , so the low - energy elementary excitations are gapless nodal quasiparticles ( qps ) with a linear energy spectrum .
these nodal qps are responsible for many low - temperature thermal and transport properties of the superconducting phase of high-@xmath0 superconductors @xcite . for instance , the specific heat exhibits a linear temperature dependence , @xmath6 @xcite , which is quite different from that of conventional @xmath7-wave superconductors , and indeed has played a crucial role in the determination of @xmath1 gap symmetry . in the superconducting state ,.
Please generate the next two sentences of the article
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nodal qps are revealed by numerous experiments , especially angle - resolved photoemission spectroscopy ( arpes ) @xcite and transport measurements @xcite , to be well - defined , with extraordinary long mean - free paths @xcite .
a residual short - range interaction between nodal qps leads only to a quite weak damping rate , @xmath8 @xmath9 , and insignificant corrections to fermion velocities @xcite . in 1999 , arpes measurements by valla _
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